JP2019100311A - Gas engine system - Google Patents

Abstract

To provide a gas engine system capable of estimating a heating value of fuel gas without assembling components into a fuel passage.SOLUTION: A gas engine system 1 comprises an engine controller 40 for controlling an opening degree A of a fuel valve 251 and an opening degree B of a throttle valve 261. The engine controller 40 is configured to be able to execute heating value estimation processing of estimating a heating value of fuel gas contained in air-fuel mixture supplied to a combustion chamber 111 on the basis of suction negative pressure PA in a suction pipe 24 when an operational state of a gas engine 10 is a reference operational state that a rotation speed of the gas engine and a load applied to the gas engine are predetermined reference values.SELECTED DRAWING: Figure 2

Description

  The present invention relates to gas engine systems.

The city gas used in Japan is 13A, 12A, 6A, 5C, L1 (6B, 6C, 7C), L2 (5A, 5B, 5AN), L3 (4A) according to the calorific value per unit volume. , 4B, 4C) are classified into seven groups (13 types). At present, city gas classified into 13A and 12A is mainly used. The calorific value (reference calorific value) per unit volume of city gas (hereinafter sometimes referred to as 13A gas) classified into 13A is 45 MJ / m ³ . However, the calorific value of the 13A gas actually supplied to the gas apparatus varies, and the calorific value fluctuates in a certain range centering on 45 MJ / m ³ .

Moreover, the gas engine with which a gas heat pump (GHP) etc. are equipped drives gas as a fuel. Therefore, city gas represented by 13A gas etc. may be used as fuel gas of a gas engine. Here, for example, a gas engine in which 13A gas is supplied as fuel gas is designed on the premise that the calorific value of 13A gas is the reference calorific value (45 MJ / m ³ ), so the calorific value of 13A gas supplied is If the amount is different from the reference calorific value due to the above-mentioned variation, there is a concern that the ability of the gas engine may not be fully exerted.

  For example, the flow rate of the mixture (fuel gas + air) supplied to the combustion chamber of the gas engine to which a predetermined load L is applied is set on the premise that the calorific value of the supplied fuel gas is a standard calorific value. Be done. Therefore, when the calorific value of the fuel gas is different from the reference calorific value, the mixed airflow amount set for the predetermined load L is the mixture set when the calorific value of the fuel gas is the standard calorific value It is different from air flow. When the amount of mixed air flow differs depending on the amount of heat generation, various problems may occur. For example, when the calorific value of the supplied fuel gas is smaller than the standard calorific value, the mixed air flow rate is increased to obtain an output corresponding to the load L. In this case, the opening degree of the throttle valve interposed in the intake pipe connected to the gas engine is increased. When the opening degree of the throttle valve is made close to the upper limit opening degree by the increase of the opening degree of the throttle valve, the opening degree is larger than the upper limit opening degree even if the opening degree of the throttle valve is further increased by the load L increase. Can not increase. Therefore, the case where the output of the gas engine according to the load L can not be obtained may occur. That is, when the calorific value of the supplied fuel gas fluctuates, there is a possibility that a problem may occur due to the fluctuation of the mixed air flow amount due to the fluctuation.

  As described above, when the calorific value of the supplied fuel gas is different from the reference calorific value, there is a possibility that the capacity of the gas engine may not be sufficiently exhibited. And in order to cope with such a situation, it is necessary to estimate the calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber. Conventionally, various methods have been used to estimate the calorific value of fuel gas.

  According to Patent Document 1, the fuel gas stored in the tank is temporarily released to temporarily increase the amount of fuel gas supplied to the combustion chamber, and based on the increase in the output of the engine at that time. The calorific value of the fuel gas is estimated.

JP, 2013-127232, A

(Problems to be solved by the invention)
According to Patent Document 1, in order to estimate the calorific value of the fuel gas, a tank and a valve are incorporated in a fuel passage through which the fuel gas flows. Parts incorporated into the fuel path must meet high standards for reliability, tight dimensional control, and specifications. Therefore, the cost of parts satisfying these requirements is high, and hence the manufacturing cost of the entire system is increased. Further, according to Patent Document 1, the fuel gas flow rate is temporarily increased to estimate the calorific value of the fuel gas, but due to that, the rapid fluctuation of the engine speed, the occurrence of excessive rotation, the fuel gas Unwanted phenomena such as the occurrence of knocking due to the increase may occur, and the occurrence of these phenomena may damage the engine body or engine driving parts.

  An object of the present invention is to provide a gas engine system capable of estimating the calorific value of fuel gas without incorporating parts into the fuel path.

(Means to solve the problem)
In the gas engine system (1) according to the present invention, the combustion chamber (111) to which the mixture of fuel gas and air is supplied is formed inside, and the mixture in the combustion chamber is ignited to generate the driving force. And a fuel pipe (21) through which the fuel gas flows, and a mixture of fuel gas and air flowing through the fuel pipe, for supplying the circulating mixture to the combustion chamber. A fuel valve (251) provided in the intake pipe (24) and the fuel pipe and configured to adjust the flow rate of the fuel gas flowing through the fuel pipe, and provided in the intake pipe and supplied to the combustion chamber And a controller (40) for controlling the opening degree of the fuel valve and the opening degree of the throttle valve. The control device includes the mixture supplied to the combustion chamber when the operating state of the gas engine is a reference operating state where the number of revolutions of the gas engine and the load applied to the gas engine are predetermined reference values. A calorific value estimation process may be performed to estimate the calorific value of fuel gas based on any of the intake negative pressure in the intake pipe, the opening degree of the throttle valve, and the flow rate of the mixture flowing through the intake pipe. Configured

  When the operating condition of the gas engine is the reference operating condition (the operating condition at which the engine speed and the load applied to the gas engine are predetermined reference values), the flow rate of the mixture supplied to the combustion chamber includes the mixture Based on the premise that the calorific value of the fuel gas to be obtained is the standard calorific value, it can be uniquely determined as the standard mixed airflow. Further, the opening degree of the throttle valve and the intake negative pressure in the intake pipe at this time can be uniquely determined as the reference throttle valve opening degree and the reference intake negative pressure, respectively. However, even if the operating condition of the gas engine is the reference operating condition, if the calorific value of the fuel gas contained in the mixture supplied to the combustion chamber is not the standard calorific value, the flow rate of the mixture supplied to the combustion chamber is Unlike the reference mixed air flow rate, the opening degree of the throttle valve and the intake negative pressure are also different from the reference throttle valve opening degree and the reference intake negative pressure. For example, when the calorific value of the fuel gas contained in the mixture supplied to the combustion chamber is less than the standard calorific value, the energy obtained by the combustion of the mixture in the combustion chamber is the calorific value of the fuel gas being the standard calorific value. It is smaller than the energy obtained in some cases. Therefore, when the fuel gas with such a small calorific value is supplied to the combustion chamber at the time of the standard operation state, the engine speed decreases due to the lack of energy if the flow rate of the mixture is the reference mixed air flow rate. In this case, the opening degree of the throttle valve is increased in order to maintain the reference operating state, that is, to suppress the decrease in the engine speed and maintain the engine speed at the reference value. An increase in the degree of opening of the throttle valve increases the mixed air flow amount in the intake pipe, and the intake negative pressure in the intake pipe increases (decreases in the negative direction). Further, when the calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber is larger than the standard calorific value, the energy obtained by the combustion of the air-fuel mixture in the combustion chamber is the calorific value of the fuel gas Is greater than the energy obtained if Therefore, when a fuel gas with such a large calorific value is supplied to the combustion chamber at the time of the reference operation state, the engine speed is increased by the excess energy if the flow rate of the mixture is the reference mixture flow rate. In this case, the degree of opening of the throttle valve is reduced in order to maintain the reference operating state, that is, to suppress the increase in the engine speed and maintain the engine speed at the reference value. The reduction of the opening degree of the throttle valve reduces the mixed air flow amount in the intake pipe, and the intake negative pressure in the intake pipe decreases (increases in the negative direction).

  That is, under the condition that the engine speed and load of the gas engine are the same (that is, under the condition of being in the reference operation state), the intake negative pressure in the intake pipe, the opening degree of the throttle valve, and the mixed air flow amount It changes with the calorific value of the fuel gas contained in the air-fuel mixture supplied to the chamber. By utilizing this, in the present invention, the control device executes the heat generation amount estimation processing in the reference operation state, and the intake negative pressure in the intake pipe, the opening degree of the throttle valve, and the mixture flowing through the intake pipe. The calorific value of the fuel gas supplied to the combustion chamber is estimated based on either the flow rate. The intake negative pressure in the intake pipe can be detected, for example, by attaching a pressure sensor (intake pressure sensor) to the intake pipe. The opening degree of the throttle valve can be detected by a throttle valve opening degree sensor attached to a drive component (for example, a throttle valve motor) for driving the throttle valve. The mixed air flow rate can be obtained from the throttle valve opening degree. Therefore, according to the present invention, the calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber can be calculated without incorporating a dedicated part for estimating the calorific value of the fuel gas in the fuel path (fuel piping). It can be estimated.

  The heat generation amount estimation process is supplied to the combustion chamber based on the intake negative pressure acquisition process (S107) for acquiring the intake negative pressure (PA) in the intake pipe and the intake negative pressure acquired in the intake negative pressure acquisition process. It is preferable to include an estimated heating value calculation process (S108) for calculating an estimated heating value (E) which is an estimated value of the heating value of the fuel gas contained in the mixture gas. According to this, the calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber can be estimated based on the intake negative pressure in the intake pipe. In this case, the estimated heat generation amount calculation process is a process of calculating the estimated heat generation amount using the correlation between the intake negative pressure and the heat generation amount of the fuel gas when the operation state of the gas engine is the reference operation state. Good to have. Furthermore, the above correlation changes with the ratio of the flow rate (Qgas) of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber to the flow rate (Qair) of the air (flow rate ratio C = Qgas: Qair). Therefore, the estimated heat value calculation process may be a process of calculating the estimated heat value based on the correlation between the intake negative pressure determined according to the flow ratio C and the heat value of the fuel gas.

In the above, the reference calorific value may be the calorific value used to define the fuel gas used for the gas engine. For example, when the fuel gas used for the gas engine is 13A gas, the reference calorific value should be about 45 MJ / m ^{3. When the} fuel gas used for the gas engine is 12A gas, the reference calorific value is 42 MJ / m ^It should be around ³ .

  Further, when the estimated calorific value calculated in the calorific value estimation process is less than a predetermined standard calorific value (E0), the control device generates the opening degree of the fuel valve and the calorific value of the fuel gas as a standard calorific value. Fuel rich correction processing (S206) to set the opening degree larger than the reference fuel valve opening degree (A0) set in the case of the amount, and the estimated heat generation amount calculated in the heat generation amount estimation process from the reference heat generation amount In the case where the opening degree of the fuel valve is larger than the reference fuel valve opening degree, it is preferable that the fuel lean correction process (S208) can be performed. According to this, when the estimated value (estimated calorific value) of the calorific value of the fuel gas supplied to the combustion chamber is less than the standard calorific value, the opening degree of the fuel valve is set larger than the standard fuel valve opening degree When the estimated calorific value is larger than the standard calorific value, the flow rate of the air-fuel mixture supplied to the combustion chamber can be calculated by setting the fuel valve opening degree smaller than the standard fuel valve opening degree. It can be maintained almost constant regardless of the fluctuation of As a result, the occurrence of a problem caused by the fluctuation of the mixed gas flow caused by the fluctuation of the calorific value of the fuel gas is prevented.

  The control device may be configured to be able to execute an ignition timing advance correction process (S207) and an ignition timing retardation correction process (S209). The ignition timing advance correction process is performed when the fuel rich correction process is performed, and the ignition timing of the air-fuel mixture in the combustion chamber is set to a reference ignition set when the calorific value of the fuel gas is a reference calorific value. It is processing to advance more than time. The ignition timing retarding correction processing is executed when the fuel lean correction processing is executed, and retards the ignition timing of the air-fuel mixture in the combustion chamber than the reference ignition timing.

  When the fuel rich correction process is performed, the calorific value of the fuel gas supplied to the combustion chamber is less than the reference calorific value. During the time required from the time the mixture containing the fuel gas whose calorific value is less than the standard calorific value is ignited in the combustion chamber to the combustion, the mixture containing the fuel gas whose calorific value is the standard calorific value is ignited in the combustion chamber It takes longer than the time it takes to burn. In this case, the control device executes the ignition timing advance correction process to advance the ignition timing more than the ignition timing (reference ignition timing) set when the calorific value of the fuel gas is the standard calorific value. Thus, the fuel gas can be ignited at an ignition timing that is optimum for the supplied fuel gas, and as a result, the engine efficiency can be improved.

  Further, when the fuel lean correction process is executed, the calorific value of the fuel gas supplied to the combustion chamber is larger than the reference calorific value. During the time required from combustion of the mixture containing fuel gas whose heat generation amount is larger than the reference heat generation amount in the combustion chamber to combustion, the mixture containing fuel gas whose heat generation amount is the reference heat generation amount is ignited in the combustion chamber It is shorter than the time it takes to burn after burning. In this case, the control device executes the ignition timing retardation correction process to retard the ignition timing with respect to the reference ignition timing to ignite the fuel gas at the optimum ignition timing for the supplied fuel gas. As a result, engine efficiency can be improved.

FIG. 1 is a view showing a schematic configuration of a gas engine system according to an embodiment of the present invention. FIG. 2 is a flowchart showing the flow of a heat generation amount estimation processing routine executed by the engine control device. FIG. 3 is an example of a map representing the correlation between the intake negative pressure and the mixed air flow rate, and the estimated calorific value when the flow ratio C is 1:10. FIG. 4 is a flowchart showing a flow of a fuel valve opening degree adjustment processing routine executed by the engine control device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a schematic configuration of a gas engine system 1 according to the present embodiment. As shown in FIG. 1, the gas engine system 1 includes a gas engine 10, an intake system component 20, an exhaust system component 30, and an engine control device 40. The engine control device 40 corresponds to the control device of the present invention.

  The gas engine 10 is an engine that obtains power by burning a mixture of fuel gas and air. The gas engine 10 has an engine body 11, a piston 12, a connecting rod 13, an output shaft 14, an intake valve mechanism 15, an exhaust valve mechanism 16, and an ignition plug 17.

  As is well known, the engine body 11 has a cylinder head and a cylinder block, and is configured by combining these parts and other parts (for example, a crankcase). A cavity is formed in the engine body 11, and a cylindrical piston 12 is disposed in the cavity so as to be capable of reciprocating in the axial direction. A combustion chamber 111 is formed by a space surrounded by the inner wall surface of the engine body 11 and the top surface of the piston 12. Thus, the combustion chamber 111 is formed inside the gas engine 10. A mixture of fuel gas and air is supplied to the combustion chamber 111.

  Further, the spark plug 17 is attached to the engine body 11 so that the tip thereof is exposed in the combustion chamber 111. The spark plug 17 is electrically connected to the engine control device 40 via the ignition coil 18 and the igniter 19. The spark plug 17 operates based on an ignition command from the engine control device 40. The mixture in the combustion chamber 111 is ignited by the operation of the spark plug 17. The gas engine 10 is driven by the mixture being ignited.

  The tip of the connecting rod 13 is swingably connected to the rear surface of the piston 12 in the engine body 11. The rear end of the connecting rod 13 is connected to the output shaft 14 via a crankshaft (not shown). The crankshaft converts the reciprocating motion of the piston 12 into rotational motion. Therefore, as the piston 12 reciprocates within the engine body 11, the output shaft 14 rotates. A rotational speed detection sensor 51 (electromagnetic pickup) is attached to the output shaft 14. The rotation number detection sensor 51 detects the rotation number per unit time of the output shaft 14, that is, the engine rotation number R. The engine rotational speed R detected by the rotational speed detection sensor 51 is input to the engine control device 40.

  Further, an intake port 11 a and an exhaust port 11 b are formed on the inner wall surface of the engine body 11 forming the combustion chamber 111. An intake system component 20 (specifically, an intake pipe 24 described later) is connected to the intake port 11a. An exhaust system component 30 (specifically, an exhaust pipe 31 described later) is connected to the exhaust port 11 b.

  The intake system component 20 has a fuel pipe 21, an air pipe 22, a mixer 23, an intake pipe 24, a fuel valve adjustment mechanism 25, and a throttle valve adjustment mechanism 26.

  A fuel source (not shown) is connected to one end (upstream end) of the fuel pipe 21, and a fuel gas (for example, 13A gas) is supplied to the fuel pipe 21 from the fuel source. Therefore, the fuel gas flows in the fuel pipe 21. Further, one end (upstream end) of the air pipe 22 is open to the atmosphere, and air is supplied to the air pipe 22 from the atmosphere. Therefore, air flows in the air pipe 22.

  Further, the other end (downstream end) of the fuel pipe 21 and the other end (downstream end) of the air pipe 22 join together, and the mixer 23 is provided at the joining portion. Accordingly, the mixer 23 is connected to the fuel pipe 21 and the air pipe 22. The fuel gas is supplied from the fuel pipe 21 and the air is supplied from the air pipe 22 to the mixer 23. Then, in the mixer 23, the fuel gas flowing through the fuel pipe 21 and the air flowing through the air pipe 22 are mixed by, for example, the venturi effect.

  Further, one end (upstream end) of the intake pipe 24 is connected to the mixer 23, and the mixture of the fuel gas and the air mixed by the mixer 23 flows through the intake pipe 24. Further, the other end (downstream end) of the intake pipe 24 is connected to an intake port 11 a formed in the engine body 11. Accordingly, the intake pipe 24 communicates with the combustion chamber 111 through the intake port 11a, and the air-fuel mixture flowing through the intake pipe 24 is supplied to the combustion chamber 111 through the intake port 11a. When the gas engine 10 is a multi-cylinder engine, the downstream portion of the intake pipe 24 is configured by an intake manifold including a plurality of branch pipes. Each branch pipe of the intake manifold is in communication with the combustion chamber in each cylinder through an intake port.

  The fuel valve adjustment mechanism 25 has a fuel valve 251 and a fuel valve motor 252. The fuel valve 251 is interposed in the middle of the fuel pipe 21. The fuel valve motor 252 is formed of, for example, a stepping motor, and is attached to the fuel valve 251 so that the opening degree of the fuel valve 251 can be adjusted by driving. By adjusting the opening degree of the fuel valve 251 by driving the fuel valve motor 252, the flow rate of the fuel gas flowing through the fuel pipe 21, that is, the flow rate of the fuel gas contained in the mixture supplied to the combustion chamber 111 The fuel gas flow rate Qgas) is adjusted.

  The throttle valve adjustment mechanism 26 has a throttle valve 261 and a throttle valve motor 262. The throttle valve 261 is interposed in the middle of the intake pipe 24. The throttle valve motor 262 is formed of, for example, a stepping motor, and is attached to the throttle valve 261 so that the opening degree of the throttle valve 261 can be adjusted by driving. By adjusting the opening degree of the throttle valve 261 by driving the throttle valve motor 262, the flow rate of the air-fuel mixture flowing through the intake pipe 24, that is, the flow rate of the air-fuel mixture supplied to the combustion chamber 111 (mixture air flow rate Qmix) Adjusted.

  The fuel valve motor 252 and the throttle valve motor 262 are electrically connected to the engine control device 40, and the engine control device 40 operates the motors, that is, the opening degree of the fuel valve 251 and the opening degree of the throttle valve 261. It is controlled.

  A fuel valve opening sensor 52 is attached to the fuel valve motor 252. The fuel valve opening degree sensor 52 detects the opening degree A of the fuel valve 251 based on the rotation angle of the fuel valve motor 252. The opening degree A of the fuel valve 251 detected by the fuel valve opening degree sensor 52 is input to the engine control device 40. Further, the throttle valve opening sensor 53 is attached to the throttle valve motor 262. The throttle valve opening degree sensor 53 detects the opening degree B of the throttle valve 261 based on the rotation angle of the throttle valve motor 262. The opening degree B of the throttle valve 261 detected by the throttle valve opening degree sensor 53 is input to the engine control device 40.

  Further, an intake pressure sensor 54 is attached to the middle of the intake pipe 24 and on the downstream side of the interposed position of the throttle valve 261 (closer to the combustion chamber 111). The intake pressure sensor 54 detects a pressure in the intake pipe 24 (intake negative pressure PA). The intake negative pressure PA detected by the intake pressure sensor 54 is input to the engine control device 40.

  The exhaust system component 30 has an exhaust pipe 31 and a catalyst device 32. One end (upstream end) of the exhaust pipe 31 is connected to an exhaust port 11 b formed in the engine body 11. Therefore, the exhaust pipe 31 communicates with the combustion chamber 111 through the exhaust port 11b. In the exhaust pipe 31, the exhaust gas generated in the combustion chamber 111 and discharged from the exhaust port 11b flows. The other end of the exhaust pipe 31 is open to the atmosphere. Further, a catalyst device 32 is interposed in the middle of the exhaust pipe 31. A catalyst 321 (for example, a three-way catalyst) is provided in the catalyst device 32. The catalyst 321 purifies the exhaust gas flowing in the exhaust pipe 31.

  Further, the output shaft 14 of the gas engine 10 is connected to the load shaft 60 via the power transmission belt BT. Therefore, when the output shaft 14 rotates, the load shaft 60 also rotates. In the present embodiment, the load shaft 60 is an output shaft of the compressor 70. In this case, when the gas engine 10 is driven to rotate the output shaft 14, the output shaft (load shaft 60) of the compressor 70 is also rotated, and the compressor 70 operates. The compressor 70 includes a suction port 71 and a discharge port 72. A suction pipe 81 is connected to the suction port 71, and a discharge pipe 82 is connected to the discharge port 72. When the compressor 70 operates (when the load shaft 60 rotates), the compressor 70 sucks the gas in the suction pipe 81 from the suction port 71 and compresses the gas sucked therein. Then, the compressed gas is discharged from the discharge port 72 to the discharge pipe 82.

  A suction pressure sensor 55 is attached to a suction pipe 81 connected to the suction port 71 of the compressor 70. The suction pressure sensor 55 detects the pressure in the suction pipe 81, that is, the pressure (suction pressure) PB of the gas sucked into the compressor 70. The suction pressure PB detected by the suction pressure sensor 55 is input to the engine control device 40.

  A discharge pressure sensor 56 is attached to the discharge pipe 82 connected to the discharge port 72 of the compressor 70. The discharge pressure sensor 56 detects the pressure in the discharge pipe 82, that is, the pressure (discharge pressure) PC of the gas discharged from the compressor 70. The discharge pressure PC detected by the discharge pressure sensor 56 is input to the engine control device 40.

  Further, an intake valve mechanism 15 and an exhaust valve mechanism 16 are incorporated in the engine body 11. The intake valve mechanism 15 has an intake valve body 151, and the exhaust valve mechanism 16 has an exhaust valve body 161. The intake valve body 151 is disposed at a position capable of closing the intake port 11 a in the combustion chamber 111, and the exhaust valve body 161 is disposed at a position capable of closing the exhaust port 11 b in the combustion chamber 111. .

  The intake valve mechanism 15 and the exhaust valve mechanism 16 operate in synchronization with the rotation of the output shaft 14 of the gas engine 10 at predetermined timings. As the intake valve mechanism 15 operates, the intake valve body 151 is periodically displaced to a position at which the intake port 11a is closed and a position at which the intake valve 11 is not closed. As the exhaust valve mechanism 16 operates, the exhaust valve body 161 is periodically displaced to a position at which the exhaust port 11 b is closed and a position at which the exhaust port 11 b is not closed.

  The engine control device 40 is configured by a microcomputer including a CPU, a ROM, and a RAM, and based on input information from various sensors and a load L applied to the gas engine 10, the opening A of the fuel valve 251 and the throttle valve 261 Control the opening B of the The gas engine 10 is controlled by the control of the opening degree A of the fuel valve 251 and the opening degree B of the throttle valve 261 by the engine control device 40.

  When driving the gas engine system 1 having such a configuration, the fuel gas flowing through the fuel pipe 21 and the air flowing through the air pipe 22 are mixed by the mixer 23 to generate an air-fuel mixture. The generated mixture flows through the intake pipe 24. The air-fuel mixture in the intake pipe 24 is supplied to the combustion chamber 111 at a predetermined timing at which the intake valve mechanism 15 opens the intake port 11a. The air-fuel mixture supplied to the combustion chamber 111 is ignited by the ignition plug 17 operating at a predetermined timing. The mixture is ignited to burn the mixture. The piston 12 reciprocates by the energy generated when the air-fuel mixture burns. The reciprocating motion of the piston 12 is converted to rotational motion by the crankshaft. The rotary motion is transmitted to the load shaft 60 through the output shaft 14 and the power transmission belt BT to operate the compressor 70. Further, the exhaust generated by the combustion of the air-fuel mixture in the combustion chamber 111 is discharged to the exhaust pipe 31 at a predetermined timing at which the exhaust valve mechanism 16 opens the exhaust port 11b. The exhaust gas discharged to the exhaust pipe 31 is discharged to the outside after being purified by the catalyst 321 in the catalyst device 32.

  During driving of the gas engine 10, the engine control device 40 controls the opening degree B of the throttle valve 261 so that the gas engine 10 outputs according to the load L. In this case, the engine control device 40 determines the engine speed R according to the load L, and outputs a command signal to the throttle valve motor 262 so that the gas engine 10 operates at the determined engine speed R. The throttle valve motor 262 is driven in response to the input command signal. Thereby, the gas engine 10 is driven according to the load L.

  Further, the engine control device 40 executes a heat generation amount estimation process for estimating the heat generation amount of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber 111 while the gas engine 10 is driven. FIG. 2 is a flowchart showing the flow of the heat generation amount estimation processing routine executed by the engine control device 40.

  The heat generation amount estimation process shown in FIG. 2 is repeatedly performed at predetermined minute time intervals while the gas engine 10 is driven. When this routine starts, the engine control device 40 first acquires the current engine rotation number R detected by the rotation number detection sensor 51 in step 101 (hereinafter, step will be abbreviated as step S) in FIG. Next, the engine control device 40 acquires the current suction pressure PB detected by the suction pressure sensor 55 and the current discharge pressure PC detected by the discharge pressure sensor 56 (S102).

  Subsequently, at S103, the engine control device 40 determines whether the operating condition of the gas engine 10 is the reference operating condition. Here, the reference operating state refers to an operating state in which the engine rotational speed R is a predetermined reference rotational speed R0 and the load L applied to the gas engine 10 is a predetermined magnitude L0. In other words, the reference operating state refers to an operating state in which the engine speed R and the load L are predetermined reference values. As an example, a state where the engine rotational speed is 1200 rpm and the load L is 40 N can be set as the reference operating state. The engine rotational speed R is detected by the rotational speed detection sensor 51. Further, the size of the load L is proportional to the amount of work of the compressor 70, and the amount of work of the compressor 70 is proportional to the amount of compression of gas by the compressor 70. Therefore, the magnitude of the load L is the difference ΔP (= PC-PB) between the suction pressure PB, which is the pressure of the gas sucked into the compressor 70, and the discharge pressure PC, which is the pressure of the gas discharged from the compressor 70. It can be determined based on

  When it is determined in S103 that the operating state of the gas engine 10 is not the reference operating state (S103: No), the engine control device 40 ends this routine, and starts this routine again after a predetermined minute time has elapsed. On the other hand, when it is determined in S103 that the operating state of the gas engine 10 is the reference operating state (S103: Yes), the engine control device 40 proceeds with the process to S104.

  In S104, the engine control device 40 acquires the current opening degree A of the fuel valve 251 detected by the fuel opening degree sensor 52 and the current opening degree B of the throttle valve 261 detected by the throttle valve opening degree sensor 53. Do.

  Subsequently, the engine control device 40 calculates the flow rate ratio C at S105. The flow rate ratio C is a ratio (Qgas: Qair) of the flow rate of the fuel gas (fuel gas flow rate Qgas) contained in the air-fuel mixture supplied to the combustion chamber 111 to the flow rate of the air (air flow rate Qair). Here, the flow rate of the air-fuel mixture supplied to the combustion chamber 111 (the mixed air flow amount Qmix) depends on the opening degree B of the throttle valve 261, and the larger the opening degree B, the larger the mixed air flow amount Qmix. Therefore, the mixed air flow rate Qmix can be obtained based on the opening degree B of the throttle valve 261. Further, the fuel gas flow rate Qgas depends on the opening degree A of the fuel valve 251, and the fuel gas flow rate Qgas increases as the opening degree A increases. Therefore, the fuel gas flow rate Qgas can be determined based on the opening degree A of the fuel valve 251. Furthermore, the air flow rate Qair can be obtained from the difference between the mixed air flow rate Qmix and the fuel gas flow rate Qgas (Qmix-Qgas). As described above, the flow rate ratio C can be calculated from the opening degree B of the throttle valve 261 and the opening degree A of the fuel valve 251 as Qgas: (Qmix-Qgas).

  After calculating the flow rate ratio C in S105, the engine control device 40 proceeds to the process in S106 to acquire the current intake negative pressure PA detected by the intake pressure sensor 54 (intake negative pressure acquisition processing). Next, at S108, the estimated heat generation amount E is calculated based on the intake negative pressure PA detected by the intake pressure sensor 54 (estimated heat generation amount calculation processing). The estimated calorific value E is an estimated value of the calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber 111.

  When the operating state of the gas engine 10 is a reference operating state (an operating state in which the engine speed R and the load L applied to the engine are predetermined reference values), the flow rate of the mixture supplied to the combustion chamber 111 (mixed air flow amount Qmix) must be unambiguously defined as the reference mixed air flow rate Q0, assuming that the calorific value of the fuel gas contained in the mixture is the reference calorific value (E0) predetermined for the fuel gas. Can. Further, the intake negative pressure PA in the intake pipe 24 at this time can also be uniquely determined as the reference intake negative pressure PA0.

  Further, even if the calorific value of the fuel gas contained in the mixture is different from the standard calorific value under the standard operating condition, the mixed air flow Qmix and the intake negative pressure PA can be uniquely determined, but the values are The reference mixed air flow rate Q0 and the reference intake negative pressure PA0 are different.

  For example, when the calorific value of the fuel gas contained in the mixture supplied to the combustion chamber 111 is less than the reference calorific value, the energy obtained by the combustion of the mixture in the combustion chamber 111 is based on the calorific value of the fuel gas. It is smaller than the energy obtained when it is a calorific value. Therefore, when fuel gas with such a small calorific value is supplied to the combustion chamber 111 at the time of reference operation state, the engine speed R decreases due to lack of energy if the mixed air flow rate Qmix is the reference mixed air flow rate Q0. In this case, the opening degree A of the throttle valve 261 is increased in order to maintain the reference operating state, that is, in order to suppress the decrease in the engine speed R and maintain the engine speed R at the reference value (R0). The flow rate of the air-fuel mixture (mixture air flow rate Qmix) in the intake pipe 24 is increased by the increase of the opening degree A of the throttle valve 261, and the intake negative pressure PA in the intake pipe 24 is increased (decreased in the negative direction). From the above, when the calorific value of the fuel gas contained in the mixed gas is less than the standard calorific value under the standard operating condition, the mixed air flow Qmix is larger than the reference mixed air flow Q0 and the intake negative pressure PA is higher (lower in the negative direction) than the reference intake negative pressure PA0.

  When the calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber 111 is larger than the standard calorific value, the energy obtained by the combustion of the air-fuel mixture in the combustion chamber 111 is the calorific value of the fuel gas. It is larger than the energy obtained when it is a reference calorific value. Therefore, when fuel gas with such a large calorific value is supplied to the combustion chamber 111 at the time of reference operation state, the engine speed R increases due to excessive energy when the mixed air flow rate Qmix is the reference mixed air flow rate Q0. . In this case, the opening degree A of the throttle valve 261 is decreased in order to maintain the reference operating state, that is, to suppress the increase in the engine speed R and maintain the engine speed at the reference value (R0). The decrease of the opening degree A of the throttle valve 261 reduces the flow rate of the air-fuel mixture (mixture air flow rate Qmix) in the intake pipe 24 and reduces the intake negative pressure PA in the intake pipe 24 (increases in the negative direction). From the above, when the calorific value of the fuel gas contained in the mixture is larger than the standard calorific value under the standard operating condition, the mixed air flow Qmix is smaller than the reference mixed air flow Q0 and the intake negative pressure PA is lower than the reference intake negative pressure PA0 (higher in the negative direction).

  That is, under the condition that the engine speed R and the load L of the gas engine 10 are the same (that is, under the condition of being in the reference operation state), the intake negative pressure PA in the intake pipe 24 is supplied to the combustion chamber 111. Affect the calorific value of the fuel gas contained in the mixture. In other words, under the reference operating condition, the intake negative pressure PA and the calorific value of the fuel gas have a correlation. Therefore, when the operating state of the gas engine 10 is the reference operating state, the calorific value of the fuel gas supplied to the combustion chamber 111 can be estimated based on the intake negative pressure PA.

Further, the above-described correlation between the intake negative pressure PA (the mixed flow amount Qmix) and the calorific value of the fuel gas changes with the flow ratio C. Therefore, the correlation between the intake negative pressure PA (the mixed flow amount Qmix) and the calorific value of the fuel gas can be expressed using the flow ratio C as a parameter. Further, such a correlation can be obtained in advance by experiment or the like or theoretically. FIG. 3 shows an example of a map in which the correlation between the intake negative pressure PA and the mixed air flow rate Qmix and the estimated heat generation amount E is shown. The example shown in FIG. 3 is a map representing the correlation between the estimated intake heat amount E and the intake negative pressure PA and the mixed air flow rate Qmix when the flow ratio C (Qgas: Qair) is 1:10. Further, in FIG. 3, the reference calorific value is 45 MJ / m ³ , the reference mixed air flow rate Q0 is 50 L / min, and the reference intake negative pressure PA0 is −30 kPa. As can be seen from FIG. 3, between the intake negative pressure PA and the estimated heat generation amount E, the lower the intake negative pressure PA (the higher the negative direction), the larger the estimated heat generation amount E, and the higher the intake negative pressure PA ( There is a correlation that the estimated calorific value E is smaller as the negative direction is lower. Further, the estimated calorific value E is larger as the mixed air flow amount Qmix is smaller, and the estimated calorific value E is smaller as the mixed air flow amount Qmix is larger.

  The engine control device 40 stores a plurality of maps as shown in FIG. 3 with the flow rate ratio C as a parameter. Then, in S107, when the flow ratio is the flow ratio C calculated in S105, a map representing the relationship between the intake negative pressure PA (mixed air flow amount Qmix) and the estimated calorific value E is extracted and extracted. With reference to the map, the estimated heat generation amount E is calculated from the intake negative pressure PA (mixed air flow rate Qmix). Thus, the engine control device 40 correlates the estimated calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber 111 with the calorific value of the intake negative pressure and the calorific value of the fuel gas in the reference operation state. Calculate using relationships. After calculating the estimated heat generation amount E in S107, the engine control device 40 ends this routine, and starts this routine again after a lapse of a minute time.

  As described above, when the operating state of the gas engine 10 is the reference operating state, the engine control device 40 generates the calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber 111 as the intake air in the intake pipe 24. It is comprised so that the emitted-heat-amount estimation process estimated based on negative pressure PA may be performed. In order to execute this heat generation amount estimation processing, for example, an intake pressure sensor 54 for detecting the intake negative pressure PA of the intake piping 24 may be attached to the intake piping 24. There is no need to install a new part on the (fuel pipe 21). Therefore, according to the present embodiment, it is possible to provide a gas engine system capable of estimating the calorific value of fuel gas without incorporating parts into the fuel path.

  Further, the engine control device 40 adjusts the opening degree B of the fuel valve 251 according to the calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber 111 while the gas engine 10 is driven. Execute the process FIG. 4 is a flow chart showing the flow of the fuel valve opening degree adjustment processing routine executed by the engine control device 40.

  The fuel valve opening adjustment processing routine shown in FIG. 4 is repeatedly executed at predetermined minute intervals while the gas engine 10 is in operation. When this routine starts, the engine control device 40 first reads the latest estimated heat generation amount E calculated in the heat generation amount estimation process in S201 of FIG. Next, it is determined whether the read estimated calorific value E is equal to the reference calorific value E0 (S202). If the estimated calorific value E is equal to the reference calorific value E0 (S202: Yes), it means that a fuel gas having a calorific value which is originally required is being supplied. Therefore, in this case, the engine control device 40 proceeds to S203 and sets the opening A of the fuel valve 251 to the reference fuel valve opening A0 set when the calorific value of the fuel gas is the standard calorific value. Do. As a result, the opening degree A of the fuel valve 251 is made the reference fuel valve opening degree A0.

  After the opening degree A is set to the reference fuel valve opening degree A0 in S203, the engine control device 40 proceeds with the process to S204. In S204, the engine control device 40 sets the ignition timing θ to the mixture in the combustion chamber 111 by the operation of the spark plug 17 to the reference ignition timing θ0. The reference ignition timing θ0 is an ignition timing predetermined as an ignition timing at which the fuel gas burns most efficiently when the calorific value of the fuel gas is the standard calorific value E0. After setting the ignition timing θ to the reference ignition timing θ0 in S204, the engine control device 40 ends this routine, and starts this routine again after a lapse of a minute time.

  When it is determined in S202 that the estimated heat generation amount E is not equal to the reference heat generation amount E0 (S202: No), the engine control device 40 proceeds to S205, and the estimated heat generation amount E is the reference heat generation amount E0. Determine if it is less than. If it is determined that the estimated heat generation amount E is less than the reference heat generation amount E0 (S205: Yes), the engine control device 40 proceeds to S206 and executes the fuel rich correction process. In the fuel rich correction process, the engine control device 40 sets the opening degree A of the fuel valve 251 to a fuel rich correction opening degree A + predetermined as an opening degree larger than the reference fuel valve opening degree A0. As a result, the opening degree A of the fuel valve 251 is made the fuel rich correction opening degree A +.

  Here, when the calorific value of the fuel gas is less than the standard calorific value, as described above, the mixed airflow quantity Qmix is larger than the reference mixed airflow quantity Q0. Further, when the opening degree A of the fuel valve 251 is made larger than the reference fuel valve opening degree A0 by the fuel rich correction processing of S206, the opening degree A of the fuel valve 251 is the reference fuel valve opening degree The flow rate of the fuel gas (fuel gas flow rate Qgas) contained in the air-fuel mixture supplied to the combustion chamber 111 increases more than in the case of A0. That is, the air-fuel mixture shifts to the fuel rich side. As a result, the energy obtained when the fuel gas burns in the combustion chamber 111 is increased. When the obtained energy increases, the output OP of the gas engine 10 becomes larger than the output according to the load L and the engine rotational speed R rises if the mixed air flow rate Qmix remains unchanged. Therefore, in order to maintain the engine speed R at the reference speed R0 so that the output OP corresponds to the load L, that is, to suppress the increase in the engine speed R (to maintain the reference operating state) The opening degree B of the throttle valve 261 is reduced. As a result, the mixed air flow rate Qmix is reduced and returned to the reference mixed air flow rate Q0.

  After executing the fuel rich correction process at S206, the engine control device 40 proceeds to S207 to execute the ignition timing advance angle correction process. In the ignition timing advance correction process, the engine control device 40 sets the ignition timing for the mixture in the combustion chamber 111 by the operation of the ignition plug 17 to a reference when the calorific value of the fuel gas is the standard calorific value. The ignition timing is controlled so as to be earlier than the ignition timing θ0, that is, the ignition timing moves to a more advanced side than the reference ignition timing θ.

  When the fuel rich correction process is performed in S206, the calorific value of the fuel gas supplied to the combustion chamber 111 is less than the reference calorific value. When fuel gas whose calorific value is smaller than the standard calorific value is supplied to the combustion chamber 111, the time required from ignition to combustion is ignited when fuel gas whose calorific value is the standard calorific value is supplied to the combustion chamber 111 It is longer than the time it takes from combustion to combustion. Therefore, the ignition timing optimum for fuel gas whose calorific value is less than the standard calorific value is earlier than the ignition timing (standard ignition timing θ0) optimum for fuel gas whose calorific value is the standard calorific value. Therefore, when the fuel rich correction process is performed, the ignition timing advance angle correction process is performed in S206, and the ignition timing is advanced by advancing to the reference ignition timing θ0 (displacement to the advance angle side). The fuel gas can be ignited at an ignition timing that is optimal for the calorific value of the fuel gas. This improves engine efficiency. After executing the processing of S207, the engine control device 40 ends this routine, and starts this routine again after a predetermined minute time has elapsed.

  When it is determined in S205 that the estimated heat generation amount E is not less than the reference heat generation amount E0, that is, when the estimated heat generation amount E is larger than the reference heat generation amount E0 (S205: No), the engine control device 40 proceeds to S208. Proceed with the process to execute the fuel lean correction process. In the fuel lean correction process, the engine control device 40 sets the opening degree A of the fuel valve 251 to a fuel lean correction opening degree A− predetermined as an opening degree smaller than the reference fuel valve opening degree A0. As a result, the opening degree A of the fuel valve 251 is made the fuel lean correction opening degree A-.

  Here, when the calorific value of the fuel gas is larger than the standard calorific value, as described above, the mixed airflow quantity Qmix is smaller than the reference mixed airflow quantity Q0. In addition, when the opening degree A of the fuel valve 251 is made smaller than the reference fuel opening degree A0 by the fuel lean correction processing of S208, the opening degree A of the fuel valve 251 is the reference fuel opening degree The flow rate of the fuel gas (fuel gas flow rate Qgas) contained in the air-fuel mixture supplied to the combustion chamber 111 is smaller than in the case of the degree A0. That is, the air-fuel mixture shifts to the fuel lean side. Thereby, the energy obtained when the fuel gas burns in the combustion chamber 111 is reduced. When the obtained energy decreases, the output OP of the gas engine 10 becomes smaller than the output according to the load L and the engine speed R decreases if the mixed air flow rate Qmix remains unchanged. Therefore, to maintain the engine speed R at the reference speed R0 so that the output OP corresponds to the load L, that is, to suppress the decrease in the engine speed R (to maintain the reference operating state) The opening degree B of the throttle valve 261 is increased. As a result, the mixed air flow rate Qmix is increased and returned to the reference mixed air flow rate Q0.

  After executing the fuel lean correction process at S208, the engine control device 40 proceeds to S209 to execute the ignition timing retard correction process. In the ignition timing retarding correction process, the engine control device 40 sets the ignition timing for the mixture in the combustion chamber 111 by the operation of the ignition plug 17 to be a reference when the calorific value of the fuel gas is the standard calorific value. The ignition timing is controlled so as to be later than the ignition timing θ0, that is, the ignition timing moves to the retarded side of the reference ignition timing θ.

  When the fuel lean correction process is performed in S208, the calorific value of the fuel gas supplied to the combustion chamber 111 is larger than the reference calorific value. When fuel gas whose calorific value is larger than the standard calorific value is supplied to the combustion chamber 111, the time required from ignition to combustion is ignited when fuel gas whose calorific value is the standard calorific value is supplied to the combustion chamber 111 It is shorter than the time it takes from combustion to combustion. Therefore, the optimal ignition timing for fuel gas whose calorific value is larger than the standard calorific value is later than the optimal ignition timing for fuel gas whose calorific value is the standard calorific value. Therefore, when the fuel lean correction process is performed, the ignition timing retard correction process is performed in S209, and the ignition timing is supplied by being delayed (shifted to the retard side) relative to the reference ignition timing θ0. The fuel gas can be ignited at an ignition timing that is optimal for the calorific value of the fuel gas. This improves engine efficiency. After executing the process of S209, the engine control device 40 ends this routine, and starts this routine again after a predetermined minute time has elapsed.

  As described above, in the present embodiment, the engine control device 40 executes the fuel valve opening degree adjustment process, and the opening degree A of the fuel valve 251 according to the estimated value of the calorific value of the fuel gas supplied to the combustion chamber 111. Is adjusted. Specifically, when the estimated calorific value E of the fuel gas is less than the reference calorific value E0, the opening degree of the fuel valve 251 is set to an opening degree A + larger than the reference fuel valve opening degree A0, and the estimated heat generation of the fuel gas When the amount E is larger than the reference heat generation amount E0, the opening degree of the fuel valve 251 is set to the opening degree A− smaller than the reference fuel valve opening degree A0. That is, the opening degree A of the fuel valve 251 is adjusted such that the opening degree A becomes smaller as the estimated heat generation amount E becomes larger (the opening degree A becomes larger as the estimated heat generation amount E becomes smaller). As a result, the mixed gas flow rate Qmix can be maintained at a substantially constant flow rate (reference mixed gas flow rate Q0) regardless of fluctuations in the calorific value of the fuel gas. Therefore, it is possible to prevent the occurrence of the problem caused by the fluctuation of the mixed air flow rate Qmix due to the fluctuation of the calorific value of the fuel gas.

  Further, the engine control device 40 executes the ignition timing advance angle correction processing when the fuel rich correction processing is performed and the opening degree A of the fuel valve 251 is made larger than the reference fuel valve opening degree A0. Is advanced with respect to the reference ignition timing θ0. Furthermore, engine control device 40 executes the ignition timing retarding correction processing when the fuel lean correction processing is performed and the opening degree A of the fuel valve 251 is made smaller than the reference fuel valve opening degree A0. Is retarded more than the reference ignition timing θ0. The engine control device 40 executes the ignition timing advance angle correction processing and the ignition timing retardation correction process, so that the mixture can be ignited at an ignition timing suitable for the calorific value of the supplied fuel gas, As a result, engine efficiency can be improved.

Table 1 shows the engine control apparatus when the calorific value (estimated calorific value E) of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber 111 under the standard operating condition changes from the standard calorific value to less than the standard calorific value. The values of the opening A of the fuel valve 251, the opening B of the throttle valve 261, the flow ratio C, the intake negative pressure PA, the mixed air flow Qmix, and the ignition timing θ when the fuel valve opening adjustment process 40 is performed. It is a table showing an example of change of. The column (1) in Table 1 shows each value when the calorific value of the fuel gas contained in the mixture is the reference calorific value (45 MJ / m ³ ), and the column (2) includes the mixture. The respective values immediately after the calorific value of the fuel gas decreases from the calorific value to the calorific value (40 MJ / m ³ ) less than the calorific value are shown, and the column (3) shows that the engine control device 40 adjusts the fuel valve opening. Shows each value when executing.

As shown in column (1) of Table 1, when the calorific value (estimated calorific value E) of the fuel gas is the reference calorific value (45 MJ / m ³ ), the opening degree A of the fuel valve 251 is the reference fuel valve opening degree A0, the opening degree B of the throttle valve 261 is the reference throttle valve opening degree B0, the flow ratio C is 1:10, the intake negative pressure PA is the reference intake negative pressure PA0 (-30 kPa), and the mixture flow rate Qmix is the reference mixture flow rate Q0 (50 L / min), the ignition timing θ is the reference ignition timing θ0 (20 °).

From the state shown in (1) column of Table 1, (2) if the calorific value of the fuel gas as shown in the column (the estimated amount of heat generation E) is decreased reference calorific value from (45 MJ / ^{m 3)} to 40 MJ / ^{m 3} The opening degree B of the throttle valve 261 is set to an opening degree B + larger than the reference throttle valve opening degree B0 in order to suppress a decrease in the engine speed. Also, along with that, the intake negative pressure PA increases from the reference intake negative pressure PA0 (−30 kPa) to a pressure (−25 kPa) that is larger (smaller in the negative direction), and the mixture flow rate Qmix becomes the reference mixture flow rate Q0. It increases from (50 L / min) to a larger flow rate (55 L / min).

  In the state shown in the (2) column of Table 1, the engine control device 40 executes the fuel rich correction process and the ignition timing advance angle correction process in the fuel valve opening degree adjustment process. By the fuel rich correction process, as shown in the (3) column, the opening degree A of the fuel valve 251 is made the fuel rich correction opening degree A + larger than the reference fuel valve opening degree A0. As a result, the ratio of the fuel gas contained in the mixture increases, and the flow ratio C changes from 1:10 to 1.1: 10. Further, the energy obtained can be increased by increasing the ratio of the fuel gas contained in the mixture gas, so the output OP of the gas engine 10 with respect to the load L when the mixture flow rate Qmix remains at 55 L / min. As a result, the engine speed R rises. In order to suppress the increase of the engine speed R, the mixed air flow rate Qmix is reduced. As a result, the mixed air flow rate Qmix returns from 55 L / min to the reference mixed air flow rate Q0 (50 L / min). Furthermore, execution of the ignition timing advance correction process advances the ignition timing θ from the reference ignition timing θ0 (20 °) to 22 °, which is an ignition timing earlier than that. This improves engine efficiency.

Table 2 shows the case where the calorific value (estimated calorific value E) of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber 111 under the standard operating condition changes from the standard calorific value to a calorific value larger than the standard calorific value. When the engine control device 40 executes the fuel valve opening adjustment process, the opening A of the fuel valve 251, the opening B of the throttle valve 261, the flow ratio C, the intake negative pressure PA, the mixed air flow Qmix, ignition It is a table which shows an example of change of each value of time theta. The column (1) in Table 2 shows each value when the calorific value of the fuel gas contained in the mixture is the reference calorific value (45 MJ / m ³ ), and the column (2) includes the mixture. The respective values immediately after the calorific value of the fuel gas rises from the standard calorific value to the calorific value (50 MJ / m ³ ) larger than the standard calorific value, the column (3) shows that the engine control device 40 adjusts the fuel valve opening Indicates each value when processing is performed.

As shown in column (1) of Table 2, when the calorific value (estimated calorific value E) of the fuel gas is the reference calorific value (45 MJ / m ³ ), the opening degree A of the fuel valve 251 is the reference fuel valve opening degree A0, the opening degree B of the throttle valve 261 is the reference throttle valve opening degree B0, the flow ratio C is 1:10, the intake negative pressure PA is the reference intake negative pressure PA0 (-30 kPa), and the mixture flow rate Qmix is the reference mixture flow rate Q0 (50 L / min), the ignition timing θ is the reference ignition timing θ0 (20 °).

From the state shown in (1) column of Table 2, (2) if the calorific value of the fuel gas as shown in the column rises reference calorific value from (45 MJ / ^{m 3)} to 50 MJ / ^{m 3,} increase in the engine speed The opening degree B of the throttle valve 261 is set to an opening degree B− smaller than the reference throttle valve opening degree B0 in order to suppress Also, along with that, the intake negative pressure PA drops from the reference intake negative pressure PA0 (−30 kPa) to a smaller (larger in the negative direction) pressure (−35 kPa), and the mixture flow rate Qmix becomes the reference mixture flow rate Q0. It decreases from (50 L / min) to a smaller flow rate (45 L / min).

  In the state shown in column (2) of Table 2, the engine control device 40 executes the fuel lean correction process and the ignition timing retardation correction process in the fuel valve opening degree adjustment process. By the fuel lean correction processing, as shown in the (3) column, the opening degree A of the fuel valve 251 is made the fuel lean correction opening degree A− smaller than the reference fuel valve opening degree A0. As a result, the ratio of fuel gas contained in the mixture decreases, and the flow ratio C changes from 1:10 to 0.9: 10. In addition, since the energy obtained can be reduced by decreasing the ratio of the fuel gas contained in the mixture, the output OP will be insufficient for the load L if the mixture flow rate Qmix remains at 45 L / min. The number of revolutions R decreases. In order to suppress a decrease in engine speed R, the mixed air flow rate Qmix is increased. As a result, the mixed air flow rate Qmix returns from 45 L / min to the reference mixed air flow rate (50 L / min). Further, the execution of the ignition timing retardation correction retards the ignition timing θ from the reference ignition timing θ0 (20 °) to 18 °, which is a later ignition timing. This improves engine efficiency.

  Thus, according to the present embodiment, the opening degree A of the fuel valve 251 and the ignition timing are adjusted in accordance with the calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber 111. As a result, the mixed air flow rate Qmix can be maintained substantially constant regardless of fluctuations in the calorific value of the fuel gas, and the mixed gas can be ignited at the optimum ignition timing for the supplied fuel gas, As a result, engine efficiency can be improved.

  As mentioned above, although embodiment of this invention was described, this invention should not be limited to the said embodiment. For example, when the engine control device 40 executes the fuel rich correction process and the ignition timing advance angle correction process, the larger the difference (E0-E) between the reference calorific value E0 and the estimated calorific value E, the larger the opening degree A becomes. The opening degree A and the ignition timing θ can be set so that the ignition timing θ becomes earlier. Further, when the engine control device 40 executes the fuel lean correction process and the ignition timing retardation correction process, the opening degree A decreases as the difference (E−E0) between the estimated heat generation amount E and the reference heat generation amount E0 increases. The opening degree A and the ignition timing θ can be set so that the ignition timing θ becomes later. That is, the optimum opening degree A and the ignition timing θ can be set in accordance with the difference between the estimated heat generation amount E and the reference heat generation amount E0. In addition, without comparing the estimated heat generation amount with the reference heat generation amount, the opening degree A becomes smaller as the estimated heat generation amount E becomes larger and the ignition timing θ becomes later (the opening degree A becomes smaller as the estimated heat generation amount E becomes smaller. The opening degree A and the ignition timing θ can be set based on the estimated heat generation amount E so that the ignition timing θ becomes large and the ignition timing θ becomes earlier. Even in this case, the engine control device 40 performs the fuel rich correction process when the estimated heat generation amount is less than the reference heat generation amount, and performs the fuel lean correction process when the estimated heat generation amount is larger than the reference heat generation amount. As a result, the ignition timing advance correction processing is performed when the fuel rich correction processing is performed, and the ignition timing retardation correction processing is performed when the fuel lean correction is performed. Further, the optimum opening A set by the fuel rich correction process and the fuel lean correction process, and the optimum ignition timing θ set by the ignition timing advance angle correction process and the ignition timing retard correction process have the flow ratio C. Is considered to be different. Therefore, the engine control device 40 can set the opening degree A and the ignition timing θ according to the above process according to the flow rate ratio C. In the above embodiment, an example in which the output shaft of the compressor 70 is connected as the load shaft 60 to the output shaft 14 of the gas engine 10 has been described. However, the components requiring other motive power are the output of the gas engine 10 It can be connected to the shaft 14. Further, in the above embodiment, an example is shown in which the calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber 111 is estimated based on the intake negative pressure PA in the intake pipe 24 in the reference operation state. However, as can be understood from the above description, the change of the intake negative pressure PA is accompanied by the change of the flow rate of the air-fuel mixture flowing through the intake pipe 24 (the mixed air flow amount Qmix) and the change of the throttle valve opening degree B. Therefore, instead of the intake negative pressure PA, the calorific value of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber 111 based on the mixed air flow rate Qix in the reference operation state or the throttle valve opening degree B. Can also be estimated. Thus, the present invention can be modified without departing from the scope of the invention.

Reference Signs List 1 gas engine system 10 gas engine 11 engine body 111 combustion chamber 12 piston 14 output shaft 17 spark plug 20 intake system component 21 fuel piping 22 air piping , 23: mixer, 24: intake pipe, 25: fuel valve adjustment mechanism, 251: fuel valve, 252: fuel valve motor, 26: throttle valve adjustment mechanism, 261: throttle valve, 262: throttle valve motor, 30: exhaust system Parts 40 Engine control device (control device) 51 Rotational speed detection sensor 52 Fuel valve opening sensor 53 Throttle valve opening sensor 54 Intake pressure sensor 55 Suction pressure sensor 56 Discharge Pressure sensor 60 Load axis 70 Compressor A A fuel valve opening A-Fuel lean correction opening A + Fuel rich correction opening A 0 Reference fuel valve opening B: Opening of throttle valve, C: Flow ratio, E: Estimated heat generation amount, E0: Reference heat generation amount, L: Load, PA: Intake negative pressure, PA0: Reference intake negative pressure, Q0: Reference mixed air flow rate, Qmix ... Mixed air flow, R ... Engine speed, R 0 ... Reference speed, θ ... Ignition timing, θ 0 ... Reference ignition timing

Claims (5)

A gas engine in which a combustion chamber to which a mixture of fuel gas and air is supplied is formed and which generates a driving force by igniting the mixture in the combustion chamber;
Fuel piping through which fuel gas flows,
An intake pipe for supplying a mixture of the fuel gas and the air flowing through the fuel pipe to the combustion chamber while the mixture of the fuel gas and the air flows.
A fuel valve provided in the fuel pipe and configured to adjust a flow rate of fuel gas flowing through the fuel pipe;
A throttle valve provided in the intake pipe and configured to adjust a flow rate of the air-fuel mixture supplied to the combustion chamber;
A control device that controls the opening degree of the fuel valve and the opening degree of the throttle valve;
Equipped with
The controller controls the mixture supplied to the combustion chamber when the operating condition of the gas engine is a reference operating condition where the number of revolutions of the gas engine and the load on the gas engine are predetermined reference values. Heat generation amount estimation processing to estimate the heat generation amount of the fuel gas contained in the air intake pipe based on any of the intake negative pressure in the intake pipe, the opening degree of the throttle valve, and the flow rate of the mixture flowing through the intake pipe Gas engine system, which is configured to be able to. In the gas engine system according to claim 1,
The heat generation amount estimation process is
Intake negative pressure acquisition processing for acquiring intake negative pressure in the intake pipe;
Estimated heat generation amount calculation processing for calculating an estimated heat generation amount which is an estimated value of the heat generation amount of the fuel gas contained in the air-fuel mixture supplied to the combustion chamber based on the intake negative pressure acquired in the intake negative pressure acquisition processing Gas engine system, including and. In the gas engine system according to claim 2,
The estimated heat value calculation process is a process of calculating the estimated heat value using the correlation between the intake negative pressure and the heat value of the fuel gas when the operating condition of the gas engine is the reference operating condition. There is a gas engine system. In the gas engine system according to claim 2 or 3,
The controller is
When the estimated calorific value calculated in the calorific value estimation process is less than a predetermined standard calorific value, the opening degree of the fuel valve is set when the calorific value of fuel gas is the standard calorific value Fuel rich correction processing to set the opening degree larger than the reference fuel valve opening degree
Fuel lean correction processing for setting the opening degree of the fuel valve to an opening degree smaller than the reference fuel valve opening degree when the estimated heat generation amount calculated in the heat generation amount estimation processing is larger than the reference heat generation amount When,
A gas engine system, configured to be able to perform. In the gas engine system according to claim 4,
The controller is
This is executed when the fuel rich correction process is performed, and advances the ignition timing of the air-fuel mixture in the combustion chamber more than the reference ignition timing set when the calorific value of the fuel gas is the standard calorific value. Ignition timing advance correction processing,
Ignition timing retardation correction processing which is executed when the fuel lean correction processing is executed and retards the ignition timing of the air-fuel mixture in the combustion chamber with respect to the reference ignition timing;
A gas engine system, configured to be able to perform.

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