JP2023031379A - engine system - Google Patents

Abstract

An object of the present invention is to provide a reforming cylinder that partially oxidizes an excessively rich air-fuel mixture to generate a reformed gas, and even if the external environment such as the intake air temperature and the intake air humidity of the engine fluctuates, To maintain the net thermal efficiency of the whole including reforming cylinders and normal cylinders near a maximum point.
A reformed gas component concentration measuring unit (S) for measuring a gas component concentration, which is the concentration of an arbitrary gas component in a reformed gas (K) generated in a reforming cylinder (40d), and an excess air ratio in the reforming cylinder (40d). within a predetermined range in which the reformed gas K is generated. The excess air ratio in the reforming cylinder 40d is controlled based on the determined gas component concentration.
[Selection drawing] Fig. 1

Description

The present invention is a reformed gas containing a combustion-promoting gas having a faster burning speed than fuel by partially oxidizing at least part of a mixture containing fuel and combustion air in at least part of a plurality of cylinders. The present invention relates to an engine system capable of operating as reformed cylinders for reforming to , and operating the remainder of a plurality of cylinders as normal cylinders to which the reformed gas reformed in the reforming cylinders is guided.

Conventionally, as an engine system, at least one normal cylinder having a combustion chamber for burning an air-fuel mixture containing fuel and combustion air is provided, and at least part of the air-fuel mixture undergoes a partial oxidation reaction in the combustion chamber to reduce the amount of fuel. It is known that the reformed gas reformed in the reforming cylinder is provided with at least one reforming cylinder for reforming into a reformed gas containing a combustion-promoting gas with a high combustion speed, and the reformed gas is led to at least a normal cylinder. (See Patent Document 1).
In the reforming cylinder, for example, a reformed gas containing a combustion promoting gas with a high burning rate such as hydrogen can be generated by causing a partial oxidation reaction of a rich air-fuel mixture containing fuel whose main component is methane. . By guiding the reformed gas to the normal cylinder, for example, the spark propagation speed in the combustion chamber of the normal cylinder can be increased, misfires and combustion fluctuations can be reduced, and the thermal efficiency can be improved by burning the combustion-promoting gas. I can expect it.
On the other hand, conventionally, in order to operate the engine at a desired thermal efficiency, it has a lambda sensor that measures the oxygen concentration of the exhaust gas flowing through the exhaust passage, and the output of the lambda sensor is used to detect excess air in the combustion chamber. An engine system is known that controls the air ratio to a predetermined excess air ratio (see Patent Document 2).

JP 2016-94930 A Japanese Patent Application Laid-Open No. 2007-278070

In the engine system disclosed in Patent Document 1, in order to operate the engine at a desired thermal efficiency, for example, as in the technology disclosed in Patent Document 2, a lambda is placed in an exhaust passage through which combustion exhaust gases from a plurality of cylinders flow. A configuration is conceivable in which a sensor is provided and the operation of the engine is controlled based on the measurement result of the lambda sensor. However, in the engine system disclosed in Patent Document 1, the reformed cylinder generates the reformed gas containing the combustion promoting gas, so the excess air ratio is set to be smaller than 1, and the air from the reformed cylinder is set to be less than 1. Even if the reformed gas is measured with a lambda sensor, it is difficult to accurately capture changes in the concentration of hydrogen, etc., as the reformed gas due to changes in the temperature and humidity of the atmosphere. It was difficult to control. Therefore, it has been desired to develop a new technique for operating the engine system disclosed in Patent Document 1 with high thermal efficiency.
In particular, as described above, in an engine system equipped with a reformed cylinder, even when the external environment such as the intake air temperature and humidity of the engine fluctuates, the technology to maintain the thermal efficiency of the engine at a high value is There was room for improvement as neither disclosure nor suggestion was made.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a reforming cylinder that causes a partial oxidation reaction of a rich air-fuel mixture to generate a reformed gas. To provide an engine system capable of maintaining the net thermal efficiency of the whole including reformed cylinders and normal cylinders near the maximum point even when the external environment such as temperature and supply air humidity fluctuates.

In order to achieve the above object, an engine system promotes combustion at a faster combustion speed than fuel by partially oxidizing at least a portion of an air-fuel mixture containing fuel and combustion air in at least a portion of a plurality of cylinders. It is possible to operate the cylinders as reforming cylinders for reforming into a reformed gas containing a volatile gas, and to operate the remaining cylinders as normal cylinders to which the reformed gas reformed in the reforming cylinders is guided. An engine system characterized by:
a reformed gas component concentration measuring unit for measuring a gas component concentration, which is the concentration of at least one of the combustion promoting gas and the unburned hydrocarbon in the reformed gas generated in the reforming cylinder; ,
a control device for executing excess air ratio control for controlling the excess air ratio in the reforming cylinder within a predetermined range in which the reformed gas is generated;
In the excess air ratio control, the control device controls the excess air ratio in the reforming cylinder based on the gas component concentration measured by the reformed gas component concentration measuring section.

As a result of extensive research, the inventors of the present invention have found that, as shown in FIG. , the concentration of hydrogen and carbon monoxide as combustion-promoting gases in the reformed gas gradually increases, exceeding a predetermined peak excess air ratio. It has been found that the concentrations of hydrogen and carbon monoxide, which serve as combustion-promoting gases in the reformed gas, gradually decrease as the amount is decreased.
Furthermore, as shown in FIG. 5, the net thermal efficiency of the engine including the reformed cylinders gradually increases as the excess air ratio of the reformed cylinders is decreased from 1 to the vicinity of the predetermined peak excess air ratio. It was found that the excess air ratio gradually decreased when it was decreased beyond the vicinity of the excess air ratio.
That is, from the results shown in FIGS. 3 and 5, when changing the excess air ratio in the reformed cylinder, the net thermal efficiency of the engine including the reformed cylinder is the amount of the combustion promoting gas generated in the reformed cylinder. It is estimated to have a positive correlation with concentration.
In the experiment, the stroke-bore ratio (stroke/bore) of the normal cylinder and the reformed cylinder, the displacement, and the engine speed were adjusted to values generally used in a normal engine.

According to the above characteristic configuration, the control device controls the excess air ratio in the reformed cylinder within a predetermined range in which the reformed gas is generated, and the ratio measured by the reformed gas component concentration measurement unit is Since the excess air ratio in the reforming cylinder is controlled based on the gas component concentration, for example, the control device controls the reformed gas component concentration (e.g., hydrogen, monoxide Concentration of carbon, etc.) is feedback-controlled so that the net thermal efficiency of the engine can be maintained at a maximum point by controlling the excess air ratio in the reforming cylinder.
In particular, even if the external environment of the engine such as supply air temperature and humidity changes, the control is executed based on the reformed gas component concentration that reflects the change in the external environment. As a result, the net thermal efficiency of the engine can be maintained at a local maximum, resulting in control that is robust against changes in the external environment of the engine.

As described above, the engine has a reforming cylinder that partially oxidizes an excessively rich air-fuel mixture to generate a reformed gas. It is possible to provide an engine system capable of executing control that maintains the net thermal efficiency of the whole including the reforming cylinder and the normal cylinder in the vicinity of the maximum point.

Further features of the engine system are:
As the reformed gas component concentration measurement unit, a combustion-promoting gas concentration measuring unit for measuring the concentration of the combustion-promoting gas in the reformed gas,
In the excess air ratio control, the control device controls the excess air ratio in the reforming cylinder so as to maximize the concentration of the combustion-promoting gas measured by the combustion-promoting gas concentration measuring section. It is in the point to do.

As in the above characteristic configuration, the control device controls the excess air ratio in the reforming cylinder so as to maximize the concentration of the combustion-promoting gas measured by the combustion-promoting gas measurement unit in the excess air ratio control. 3 and 5, the concentration of the combustion-promoting gas in the reformed gas is increased, and the net thermal efficiency in the normal cylinder, which has a positive correlation with the concentration of the combustion-promoting gas, is operated at a maximum point. can.

Further features of the engine system are:
The excess air ratio control controls the excess air ratio of the reforming cylinder in a form that follows an arbitrarily changeable reference excess air ratio,
The control device is configured to be capable of executing excess air ratio reduction control for reducing the excess air ratio by a predetermined determination change amount from the reference excess air ratio,
When the amount of change in concentration of the combustion-promoting gas measured by the combustion-promoting gas concentration measuring unit before and after executing the excess air ratio reduction control is positive, the control device controls the reference excess air ratio. and increasing the reference excess air ratio when the amount of change in the concentration of the combustion-promoting gas is negative.

Further features of the engine system are:
The excess air ratio control controls the excess air ratio of the reforming cylinder in a form that follows an arbitrarily changeable reference excess air ratio,
The control device is configured to be capable of executing excess air ratio increase control for increasing the excess air ratio by a predetermined determination change amount from the reference excess air ratio,
When the concentration change amount of the combustion-promoting gas measured by the combustion-promoting gas concentration measuring unit before and after executing the excess air ratio increasing control is positive, the control device controls the reference excess air ratio. and controlling the reference excess air ratio to decrease when the amount of change in the concentration of the combustion-promoting gas is negative.

As in the above characteristic configuration, excess air ratio decrease control for decreasing the excess air ratio of the judgment change amount from the reference excess air ratio or excess air ratio increase control for increasing the excess air ratio of the judgment change amount from the reference excess air ratio is executed. By doing so, it is possible to grasp the concentration change trend of the combustion-promoting gas when the excess air ratio is changed at the time of execution, so by changing the reference excess air ratio based on the concentration change trend, The ratio can approach the peak excess air ratio that maximizes the concentration of pro-combustible gases.
The reference excess air ratio is maintained at the peak excess air ratio that maximizes the concentration of the combustion-promoting gas by continuously executing the excess air ratio reduction control or the excess air ratio increase control at predetermined time intervals. This allows continued operation to maximize the net thermal efficiency of the engine.

Further features of the engine system are:
As the reformed gas component concentration measurement unit, an unburned hydrocarbon concentration measurement unit that measures the concentration of the unburned hydrocarbons in the reformed gas,
The excess air ratio control controls the excess air ratio of the reforming cylinder in a form that follows an arbitrarily changeable reference excess air ratio,
The control device performs excess air ratio reduction control for decreasing the excess air ratio by a predetermined determination change amount from the reference excess air ratio, or increases the excess air ratio by a predetermined determination change amount from the reference excess air ratio. configured to be able to execute excess air ratio increase control,
The control device determines that the absolute value of the amount of change in the concentration of unburned hydrocarbons measured by the unburned hydrocarbon concentration measuring unit before and after executing the excess air ratio reduction control or the excess air ratio increase control is The reference excess air ratio is controlled to be increased when the amount of change in concentration of unburned hydrocarbons exceeds a predetermined determination amount of change in concentration, and when the absolute value of the amount of change in concentration of unburned hydrocarbons is equal to or less than the predetermined amount of change in concentration of determination, the reference The point is that the excess air ratio is controlled to decrease.

As shown in FIG. 4, the inventors found that when the excess air ratio of the reforming cylinder is varied by controlling the excess air ratio, the concentration of unburned hydrocarbons in the reformed gas increases as the excess air ratio decreases. 5 gradually increases, and in particular, when combined with FIG. It can be seen that the amount of change in the concentration of unburned hydrocarbons with respect to the change in the excess ratio increases greatly.
According to the characteristic configuration based on the knowledge, the control device measures the unburned hydrocarbon concentration measured by the unburned hydrocarbon concentration measurement unit before and after executing the excess air ratio reduction control or the excess air ratio increase control. Control is performed to increase the reference excess air ratio when the absolute value of the concentration change amount of hydrocarbons exceeds a predetermined determination concentration change amount, and the absolute value of the unburned hydrocarbon concentration change amount is equal to or less than the predetermined determination concentration change amount. In the case of , by controlling the reference excess air ratio to decrease, by appropriately setting a predetermined determination concentration change amount when the air excess ratio is changed by a predetermined determination change amount, The excess air ratio can be set to maximize the net thermal efficiency of the engine.

Further features of the engine system are:
A first fuel supply unit that supplies fuel guided to at least the normal cylinder and a second fuel supply unit that supplies fuel guided to the reforming cylinder are separately provided,
The controller adjusts the amount of fuel supplied by the second fuel supply unit to control the excess air ratio in the reforming cylinder within a predetermined range in which the reformed gas is generated. Fuel that is the ratio of the total amount of fuel supplied to all the normal cylinders by the first fuel supply unit to the total amount of fuel supplied to all the reforming cylinders by the second fuel supply unit in the running state When executing fuel ratio decrease control that decreases the ratio,
In the excess air ratio control, the excess air ratio in the reforming cylinder is controlled based on the gas component concentration measured by the reformed gas component concentration measuring section.

The inventors of the present invention reduce the fuel ratio, which is the ratio of the total amount of fuel supplied to all normal cylinders to the total amount of fuel supplied to the reforming cylinders, i.e. It has been found that by increasing the net thermal efficiency of the engine can be improved.
Therefore, according to the above characteristic configuration, in addition to improving the net thermal efficiency based on the fuel ratio reduction control, by controlling the excess air ratio in the reforming cylinder based on the gas component concentration measured by the reformed gas component concentration measuring section, Since the net thermal efficiency can be improved, a further improvement in the net thermal efficiency of the engine can be expected.

Further features of the engine system are:
In the excess air ratio control, the control device controls the excess air ratio in the reforming cylinder based on the gas component concentration measured by the reformed gas component concentration measurement unit, A reformed gas operation is executed in which only the reformed gas is introduced as the fuel into the normal cylinder.

As described above, the net thermal efficiency of the engine can be improved by increasing the ratio of the reformed gas (combustion promoting gas) as the fuel for the normal cylinders. In addition to improving the net thermal efficiency of the engine, the excess air ratio in the reforming cylinder can be controlled based on the gas component concentration measured by the reformed gas component concentration measurement unit. Since the net thermal efficiency of the engine can also be improved by executing this, further improvement of the net thermal efficiency of the engine can be expected.

Further features of the engine system are:
The present invention is provided with a reforming engine including at least one reforming cylinder as the plurality of cylinders, and an external output engine including the normal cylinder as the plurality of cylinders.

The engine system of the present invention, as in the above-described characteristic configuration, is configured to separately include a reforming engine having a reforming cylinder and an external output engine having a normal cylinder into which reformed gas is guided from the reforming cylinder. also preferably exhibits the effects described above.

1 is a schematic configuration diagram of an engine system according to an embodiment; FIG. FIG. 4 is a flow chart showing control of local maximum point tracking control of net thermal efficiency; FIG. 4 is a graph showing the concentrations of hydrogen and carbon monoxide in the reformed gas for each excess air ratio in the reforming cylinder. FIG. 4 is a graph showing concentrations of unburned hydrocarbons and methane in reformed gas for each excess air ratio in a reforming cylinder. FIG. 4 is a graph showing the net thermal efficiency of the entire engine for each excess air ratio in a reforming cylinder;

An engine system 100 according to an embodiment of the present invention has a reforming cylinder that partially oxidizes a rich air-fuel mixture to produce a reformed gas. To maintain the net thermal efficiency of the whole including reforming cylinders and normal cylinders in the vicinity of the maximum point even when the thermal environment fluctuates.
The engine system 100 will be described below with reference to the drawings.

The engine system 100 according to the embodiment, as shown in FIG. and a reformed gas K containing a combustion-promoting gas having a faster burning speed than the fuel F by partially oxidizing at least a part of the mixture M. A reforming cylinder 40d for reforming, a first fuel supply unit supplying fuel guided to the normal cylinders 40a, 40b, and 40c, and a second fuel supply unit supplying fuel guided to the reforming cylinder 40d. Each is separately provided, and the reformed gas K reformed in the reforming cylinder 40d is led to at least the normal cylinders 40a, 40b, and 40c (in this embodiment, it is led only to the normal cylinders 40a, 40b, and 40c).
Incidentally, in the reforming cylinder 40d, the steam reforming represented by [Equation 1] below and the water gas shift reaction represented by [Equation 2] also proceed.

CH ₄ +H ₂ 0→CO+3H ₂ [Formula 1]

CO+H ₂ 0→CO ₂ +H ₂ [Formula 2]

An engine system 100 according to an embodiment will be described below with reference to FIG.
The engine system 100 of this embodiment is configured as a turbocharged engine, and includes at least one or more (three in this embodiment) normal cylinders 40a, 40b, and 40c and at least one or more (this embodiment 1) reforming cylinder 40d. Furthermore, the engine control unit is composed of a hardware group and a software group for controlling the operation of the turbo-supercharged engine based on the input signals of the measurement results of sensors that detect the operating state of the engine. (hereinafter referred to as a control device 50).

Although not shown in detail, this type of engine system 100 supplies air from an intake main pipe 20 to combustion chambers (not shown) of normal cylinders 40a, 40b, and 40c through intake valves (not shown). The air-fuel mixture M is compressed by the upward movement of the piston, and is spark-ignited by a spark plug (not shown) to be burned and expanded, thereby pushing down the piston and generating rotational power from the rotating shaft (not shown). Along with the output, the exhaust gas E generated by combustion is pushed out from the combustion chambers of the normal cylinders 40a, 40b, and 40c to the exhaust passage 27 via the exhaust valve (not shown) and discharged to the outside.
Although the details will be described later, the combustion air A supplied from the air supply main pipe 20 is also supplied to the reforming cylinder 40d through the reforming cylinder supply branch pipe 20d, and the reforming cylinder 40d also pushes down the piston. output rotational power from the rotating shaft. However, the reformed gas K generated as exhaust gas in the reforming cylinder 40d is not discharged to the outside, and all of it is returned to the supply main pipe 20 through the reformed gas passage 28. It will be led to the normal cylinders 40a, 40b, and 40c.

The air supply main pipe 20 includes an air cleaner 21 for purifying the combustion air A, a venturi mixer 14 for mixing the combustion air A with the fuel F at an appropriate ratio (air-fuel ratio), a normal cylinder 40a by adjusting the opening, A normal cylinder throttle valve 23 capable of adjusting the amount of air-fuel mixture M supplied to 40b and 40c is provided in the order described from the upstream side.
That is, in the air supply main pipe 20, the mixture M produced by mixing the fuel F and the combustion air A in the mixer 14 is adjusted to a predetermined flow rate via the normal cylinder throttle valve 23, and is normally It is introduced into the combustion chambers of cylinders 40a, 40b and 40c.

A compressor 31 serving as a supercharger 30 for compressing the combustion air A is provided in a reforming cylinder supply branch pipe 20d branching from the main supply pipe 20 on the upstream side of the mixer 14. An intercooler 22 that cools the combustion air A, a reforming cylinder throttle valve 25 that can adjust the amount of air-fuel mixture M supplied to the reforming cylinder 40d by adjusting the opening, and an appropriate amount of fuel F to the combustion air A. A venturi type mixer 16 for mixing at a ratio (air-fuel ratio) is provided in the order described from the upstream side.

In the first fuel supply passage 11 that guides the fuel F to the mixer 14, the pressure difference between the combustion air A in the air supply main pipe 20 on the upstream side of the mixer 14 and the fuel F in the first fuel supply passage 11 is kept constant. A first fuel flow rate control valve 13 for adjusting the amount of fuel F supplied to the combustion chambers of the normal cylinders 40a, 40b, and 40c via a differential pressure regulator 12 and a mixer 14 is provided. That is, the first fuel supply path 11, differential pressure regulator 12, mixer 14, and first fuel flow rate control valve 13 function as a first fuel supply section.

The turbocharger 30 supplies exhaust gas E discharged from the normal cylinders 40a, 40b, 40c to a turbine 32 provided in an exhaust passage 27 connected to the normal cylinders 40a, 40b, 40c, and is connected to the turbine 32. A turbocharger 30 compresses the air-fuel mixture M supplied to the combustion chamber of the reforming cylinder 40d by means of a compressor 31 provided in the reforming cylinder supply pipe 20d. That is, the turbocharger 30 rotates the turbine 32 by the kinetic energy of the exhaust gas E flowing through the exhaust passage 27, and the rotational force of the turbine 32 causes combustion air to flow through the reforming cylinder supply air branch pipe 20d. A is compressed and supplied to the combustion chamber of the reforming cylinder 40d, so-called supercharging.
That is, in this embodiment, the supercharger 30 supercharges only the combustion air A guided to the reforming cylinder 40d.

The air supply main pipe 20 is connected downstream of the air cleaner 21 to a plurality of normal cylinder supply branch pipes 20a, 20b, and 20c that guide the combustion air A to the normal cylinders 40a, 40b, and 40c, respectively. It is branched into a pipe 20 and a reforming cylinder supply branch pipe 20d that guides the combustion air A to the reforming cylinder 40d.
The reforming cylinder 40d partially oxidizes the air-fuel mixture M in its own combustion chamber N to produce hydrogen and carbon monoxide, which burn faster than the fuel F (e.g., methane). is configured to generate a reformed gas K containing Here, when methane and air are mixed and burned, hydrogen and carbon monoxide are generated in a fuel-rich region where the excess air ratio is less than 1 (for example, the excess air ratio region indicated by λα in FIG. 3). It is known that there is a volume peak.
Therefore, in this embodiment, in order to burn the air-fuel mixture M in a fuel rich state in the fuel chamber of the reforming cylinder 40d, the reforming cylinder supply pipe 20d for supplying the fuel mixture M to the reforming cylinder 40d is provided. is connected to a second fuel supply passage 29 for supplying fuel F via a venturi mixer 16, and a second fuel flow rate control for controlling the flow rate of fuel F is connected to the second fuel supply passage 29. A valve 15 is provided. On the upstream side of the second fuel flow rate control valve 15 in the second fuel supply path 29, a compressor (not shown) is provided to increase the supply pressure of the fuel F to the boost pressure at the outlet of the compressor 31 of the air supply main pipe 20. ), etc. are provided.
Further, the reforming cylinder 40d is connected to a reformed gas passage 28 through which the reformed gas K reformed in the reforming cylinder 40d flows. The end is connected to the downstream side of the normal cylinder throttle valve 23 of the intake main pipe 20 . That is, in this embodiment, all of the reformed gas K is guided to the normal cylinders 40a, 40b, and 40c.
The control device 50 controls the excess air ratio in the reforming cylinder 40d to be within a predetermined range in which the reformed gas K is generated, that is, the excess air ratio of the air-fuel mixture M in the reforming cylinder 40d becomes less than 1. Excess air ratio control for controlling the degree of opening of the second fuel flow rate control valve 15 is executed as described above. That is, the second fuel supply path 29, the mixer 16, and the second fuel flow rate control valve 15 function as a second fuel supply section.

A rotating shaft (not shown) of the engine main body 40 is provided with a rotational speed sensor as an operating state detection unit 41 for measuring the rotating speed of the rotating shaft (not shown).
Furthermore, a torque measurement sensor that measures the torque of the rotation shaft is provided as the operating state detection unit 41 on the rotation shaft (not shown) of the engine main body 40, and the control device 50 includes, for example, a rotation speed sensor The first fuel flow control valve 13, the second fuel flow control valve so that the engine output calculated based on the torque measured by the torque measurement sensor becomes the target output. 15, controls the opening degrees of the normal cylinder throttle valve 23 and the reforming cylinder throttle valve 25;

As a result of extensive research, the inventors of the present invention have found that, as shown in FIG. 3, the concentration of hydrogen and carbon monoxide as combustion-promoting gases in the reformed gas K gradually increases, exceeding the peak excess air ratio. It has been found that the concentrations of hydrogen and carbon monoxide, which serve as combustion-promoting gases in the reformed gas K, gradually decrease as they are decreased.
Furthermore, as shown in FIG. 5, the net thermal efficiency of the engine body 40 including the reforming cylinder 40d gradually increases as the excess air ratio of the reforming cylinder 40d is decreased from 1 to near the peak excess air ratio, and reaches a peak. It was found that the excess air ratio gradually decreased when it was decreased beyond the vicinity of the excess air ratio.
That is, from the results shown in FIGS. 3 and 5, when the excess air ratio is changed in the reforming cylinder 40d, the net thermal efficiency of the engine body 40 including the reforming cylinder 40d is generated by the reforming cylinder 40d. It is presumed to have a positive correlation with the concentration of combustion promoting gas.

Therefore, the engine system 100 according to this embodiment has the following configuration in order to maintain the overall net thermal efficiency including the reforming cylinder 40d and the normal cylinders 40a, 40b, and 40c near the maximum point.
The engine system 100 includes a hydrogen sensor S (reformed gas component concentration measurement unit, combustion promoting gas concentration measurement unit) that measures the concentration of hydrogen, which is a combustion promoting gas, in the reformed gas K generated in the reforming cylinder 40d. part) is provided at the outlet of the reforming cylinder 40d in the reformed gas passage 28, and the control device 50 controls the reforming cylinder based on the hydrogen concentration measured by the hydrogen sensor S in the excess air ratio control. In other words, the control device 50 controls the excess air ratio in the reforming cylinder 40d so that the concentration of hydrogen measured by the hydrogen sensor S is maximized in the excess air ratio control. In the form of controlling the excess air ratio, the net thermal efficiency of the engine body 40 is maintained at the maximum point by controlling the excess air ratio of the reforming cylinder 40d.

Hereinafter, a description will be added based on the control flow of FIG. 2 regarding the specific control flow of the control. This control maintains the excess air ratio of the reforming cylinder 40d at a value that maximizes the concentration of hydrogen in the reformed gas K, and maintains the net thermal efficiency of the engine body 40 at the maximum point.

In this control, when the engine main body 40 is operated at a predetermined target output, the control device 50 first adjusts the excess air ratio of the reforming cylinder 40d to follow a reference excess air ratio that can be arbitrarily set. shall be controlled.
First, the control device 50 controls the second fuel supply unit to set the excess air ratio of the reforming cylinder 40d to a predetermined arbitrary reference excess air ratio (in this step, for example, a maximum value less than 1 (for example, 0 .95)) (#01).

When the excess air ratio of the reforming cylinder 40d is set to the reference excess air ratio, i.e., before the excess air ratio reduction control described below is executed, the control device 50 detects that the hydrogen sensor S The concentration λC1 of hydrogen (an example of combustion promoting gas) is measured and stored. (#02).
Next, the control device 50 performs excess air ratio reduction control to reduce the excess air ratio of the reformed cylinder 40d, which is set to the reference excess air ratio, by a predetermined determination change amount λJ (for example, a value of about 0.05). (#03), and after the excess air ratio reduction control, the hydrogen sensor S measures and stores the concentration λC2 of hydrogen (an example of a combustion promoting gas) (#04).

Next, when the hydrogen concentration change amount before and after executing the excess air ratio reduction control is negative (λC2−λC1<0: #05), the control device 50 reduces the reference excess air ratio by the reduction control amount Δλ( For example, a value of about 0.05) (#06), and when the hydrogen concentration change amount before and after executing the excess air ratio reduction control is positive (λC2-λC1>0: #07), the reference The excess air ratio is decreased by a decrease control amount Δλ (for example, a value of about 0.05) (#08).

Here, the decrease control amount Δλ (absolute value) is set to be equal to or less than the predetermined determination change amount λJ (absolute value).

The excess air ratio (reference excess air ratio) of the reforming cylinder 40d is controlled so that the hydrogen concentration in the reformed gas K is maximized by continuously executing the processes #02 to #08 at predetermined time intervals. Thus, the net thermal efficiency of the entire engine body 40 based on the excess air ratio control in the reforming cylinder 40d can be maintained at the maximum point.

Furthermore, the inventors of the present application found that the total amount of fuel supplied to all the normal cylinders 40a, 40b, and 40c with respect to the total amount of fuel supplied to all the reforming cylinders 40d while performing excess air ratio control. In the fuel ratio reduction control for reducing the fuel ratio, which is the fuel ratio, it has been found that the net thermal efficiency of the engine main body 40 is improved as the fuel ratio is reduced.
Therefore, the control device 50 adjusts the amount of fuel supplied by the second fuel supply unit and controls the excess air ratio in the reforming cylinders 40d. When executing fuel ratio reduction control for reducing the fuel ratio, which is the ratio of the total fuel supply amount to all the normal cylinders 40a, 40b, and 40c by the first fuel supply unit to the total fuel supply amount of the hydrogen sensor Based on the hydrogen concentration measured at S, the excess air ratio of the reforming cylinder 40d is controlled.
Through this control, in addition to improving the net thermal efficiency based on the fuel ratio reduction control, it is possible to improve the net thermal efficiency by controlling the excess air ratio in the reforming cylinder 40d based on the hydrogen concentration measured by the hydrogen sensor S. Therefore, a further improvement in the net thermal efficiency of the engine can be expected.

[Another embodiment]
(1) In the above-described embodiment, the reformed gas component concentration measuring unit is provided with a hydrogen sensor S for measuring the concentration of hydrogen as the combustion-promoting gas in the reformed gas K. A configuration including a carbon monoxide sensor that measures the concentration of carbon monoxide may be employed. Furthermore, as the reformed gas component concentration measuring unit, a configuration is adopted in which an unburned hydrocarbon sensor that measures the concentration of unburned hydrocarbons such as methane in the reformed gas K instead of the concentration of the combustion promoting gas is adopted. I don't mind.
Moreover, a configuration including a plurality of sensors out of the hydrogen sensor, the carbon monoxide sensor, and the unburned hydrocarbon sensor may be employed.

(2) In the above embodiment, regarding the control to maintain the net thermal efficiency of the engine body 40 at the local maximum point, the control device 50 changes the excess air ratio of the reforming cylinder 40d set to the reference excess air ratio to a predetermined determination change. Although an example of configuration for executing excess air ratio reduction control that decreases by an amount λJ (for example, a value of about 0.05) has been shown, even in a configuration that executes excess air ratio increase control for increasing the excess air ratio, The object of the present invention can be satisfactorily achieved.
That is, the control device 50 is configured to be capable of executing excess air ratio increase control for increasing the excess air ratio by a predetermined determination change amount from the reference excess air ratio. When the hydrogen concentration change amount measured by the hydrogen sensor S in is positive, the reference excess air ratio is controlled to increase, and when the hydrogen concentration change amount is negative, the reference excess air ratio is controlled to decrease. It does not matter if the configuration is such that

(3) In the above embodiment, an unburned hydrocarbon sensor (an example of an unburned hydrocarbon concentration measuring unit: not shown) for measuring the concentration of unburned hydrocarbons such as methane is used as the reformed gas component concentration measuring unit. When provided, it is preferable to perform the following control instead of the control of the maximum point of the net thermal efficiency of the above embodiment in order to maintain the net thermal efficiency of the engine body 40 at the maximum point.
That is, the excess air ratio control controls the excess air ratio of the reforming cylinder 40d so as to follow an arbitrarily changeable reference excess air ratio. or excess air ratio increase control for increasing the excess air ratio by a predetermined determination change amount.
Then, the control device 50 determines the absolute value of the amount of change in the concentration of unburned hydrocarbons measured by the unburned hydrocarbon concentration sensor before and after executing the excess air ratio reduction control or the excess air ratio increase control. When the concentration change amount is exceeded, the reference excess air ratio is controlled to increase, and when the absolute value of the concentration change amount of unburned hydrocarbons is equal to or less than a predetermined determination concentration change amount, the reference excess air ratio is controlled to decrease.
In this control, the inventors have determined that the absolute value of the amount of change in the concentration of unburned hydrocarbons in the reformed gas K measured by the unburned hydrocarbon sensor, as shown in FIGS. It was completed in view of the sudden increase in the net thermal efficiency near the maximum point.

(4) In the above embodiment, the hydrogen sensor S as the reformed gas component concentration measuring unit is provided at the outlet of the reforming cylinder 40d of the reformed gas passage 28. When a catalyst (not shown) for promoting reforming of the reformed gas K is provided in 28, the hydrogen sensor S is preferably provided downstream of the catalyst.

(5) In the above embodiment, the number of normal cylinders may be one or more, and the number of reforming cylinders may be one or more. It can perform well.

(6) In the above embodiment, one engine main body 40 is provided with the reforming cylinder 40d and the normal cylinders 40a, 40b, and 40c to which the reformed gas K generated in the reforming cylinder 40d is introduced. A configuration example is shown.
Instead of this configuration, although not shown, there is a reforming engine having at least one reforming cylinder, and an external output having a normal cylinder to which the reformed gas generated in the reforming cylinder of the reforming engine is guided. A configuration including an engine can be adopted.
Even with this configuration, the various controls executed by the control device 50 described in the above embodiment can be executed, and the effects thereof can be satisfactorily exhibited.

(7) In the fuel ratio reduction control, the control device 50 sets the fuel ratio to zero while conducting the oxygen-containing gas supply control, and guides only the reformed gas K as fuel to the normal cylinders 40a, 40b, and 40c. Reformed gas operation can also be performed.
In this case, the first fuel supply path 11, the differential pressure regulator 12, the first fuel flow control valve 13, and the mixer 14 as the first fuel supply section can be omitted.

(8) The reformed gas flow path 28 is at least one of the exhaust port 28a of the reforming cylinder 40d and the normal cylinder supply branch pipes 20a, 20b, 20c that supply fresh air to the normal cylinders 40a, 40b, 40c. A configuration connected as above may be adopted.

(9) In the above-described embodiment, the engine system 100 includes the supercharger 30, but the object of the present invention can be satisfactorily achieved even if the configuration does not include the supercharger 30.
As described above, in a configuration in which the supercharger 30 is not provided, the reforming cylinder supply branch pipe 20d is not pressurized to the supercharging pressure. Since there is no need to increase the pressure of the fuel F, the configuration can be simple and compact without a compressor or the like for increasing the pressure. Incidentally, in this case, the pressure of the fuel F supplied from the mixer 16 to the reforming cylinder supply pipe 20d is set to the normal supply pressure.
Furthermore, in the above-described embodiment, an example in which a turbocharger is provided as the supercharger 30 is shown, but a supercharger may be used.
Further, in the above-described embodiment, an example of so-called single-stage supercharging, in which the supercharger 30 includes a single compressor 31 and a single turbine 32, is shown. I don't mind.

(10) In the above embodiment, the fuel F is the city gas 13A, but from the essential meaning of the present invention, it is not limited to the gas fuel, and may be a liquid fuel such as gasoline.

(11) In the above embodiment, the fuel F is supplied by the venturi system, but a configuration in which it is injected into the reforming cylinder supply pipe 20d or a configuration in which it is directly injected into the reforming cylinder 40d is adopted. can do. In this case, the excess air ratio can be controlled by adjusting the injection amount of the fuel F.

It should be noted that the configurations disclosed in the above embodiments (including other embodiments, the same shall apply hereinafter) can be applied in combination with configurations disclosed in other embodiments as long as there is no contradiction. The embodiments disclosed in this specification are exemplifications, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the object of the present invention.

The engine system of the present invention has a reforming cylinder that partially oxidizes an over-rich air-fuel mixture to produce a reformed gas. Even in this case, the net thermal efficiency of the whole including the reforming cylinder and the normal cylinder can be maintained in the vicinity of the maximum point, and can be effectively used.

40: Engine body 40a: Normal cylinder 40b: Normal cylinder 40c: Normal cylinder 40d: Reforming cylinder 50: Control device S: Hydrogen sensor 100: Engine system A: Combustion air E: Exhaust gas F: Fuel K: Reformed gas M : mixture

Claims (8)

At least part of the plurality of cylinders is reformed into a reformed gas containing a combustion promoting gas having a faster burning speed than the fuel by partially oxidizing at least part of the air-fuel mixture containing the fuel and the combustion air. In an engine system capable of operating as reforming cylinders and operating the remainder of the plurality of cylinders as normal cylinders to which the reformed gas reformed in the reforming cylinders is guided,
a reformed gas component concentration measuring unit for measuring a gas component concentration, which is the concentration of at least one of the combustion promoting gas and the unburned hydrocarbon in the reformed gas generated in the reforming cylinder; ,
a control device for executing excess air ratio control for controlling the excess air ratio in the reforming cylinder within a predetermined range in which the reformed gas is generated;
The control device controls the excess air ratio in the reformed cylinder based on the gas component concentration measured by the reformed gas component concentration measurement unit in the excess air ratio control. As the reformed gas component concentration measurement unit, a combustion-promoting gas concentration measuring unit for measuring the concentration of the combustion-promoting gas in the reformed gas,
In the excess air ratio control, the control device controls the excess air ratio in the reforming cylinder so as to maximize the concentration of the combustion-promoting gas measured by the combustion-promoting gas concentration measuring section. The engine system according to claim 1. The excess air ratio control controls the excess air ratio of the reforming cylinder in a form that follows an arbitrarily changeable reference excess air ratio,
The control device is configured to be capable of executing excess air ratio reduction control for reducing the excess air ratio by a predetermined determination change amount from the reference excess air ratio,
When the amount of change in concentration of the combustion-promoting gas measured by the combustion-promoting gas concentration measuring unit before and after executing the excess air ratio reduction control is positive, the control device controls the reference excess air ratio. 3. The engine system according to claim 2, wherein the air ratio is controlled to decrease, and the reference excess air ratio is controlled to increase when the amount of change in concentration of the combustion promoting gas is negative. The excess air ratio control controls the excess air ratio of the reforming cylinder in a form that follows an arbitrarily changeable reference excess air ratio,
The control device is configured to be capable of executing excess air ratio increase control for increasing the excess air ratio by a predetermined determination change amount from the reference excess air ratio,
When the concentration change amount of the combustion-promoting gas measured by the combustion-promoting gas concentration measuring unit before and after executing the excess air ratio increasing control is positive, the control device controls the reference excess air ratio. 3. The engine system according to claim 2, wherein control is performed to increase the air ratio, and control is performed to decrease the reference excess air ratio when the amount of change in concentration of the combustion promoting gas is negative. As the reformed gas component concentration measurement unit, an unburned hydrocarbon concentration measurement unit that measures the concentration of the unburned hydrocarbons in the reformed gas,
The excess air ratio control controls the excess air ratio of the reforming cylinder in a form that follows an arbitrarily changeable reference excess air ratio,
The control device performs excess air ratio reduction control for decreasing the excess air ratio by a predetermined determination change amount from the reference excess air ratio, or increases the excess air ratio by a predetermined determination change amount from the reference excess air ratio. configured to be able to execute excess air ratio increase control,
The control device determines that the absolute value of the amount of change in the concentration of unburned hydrocarbons measured by the unburned hydrocarbon concentration measuring unit before and after executing the excess air ratio reduction control or the excess air ratio increase control is The reference excess air ratio is controlled to be increased when the amount of change in concentration of unburned hydrocarbons exceeds a predetermined determination amount of change in concentration, and when the absolute value of the amount of change in concentration of unburned hydrocarbons is equal to or less than the predetermined amount of change in concentration of determination, the reference 2. The engine system according to claim 1, wherein the excess air ratio is controlled to decrease. A first fuel supply unit that supplies fuel guided to at least the normal cylinder and a second fuel supply unit that supplies fuel guided to the reforming cylinder are separately provided,
The controller adjusts the amount of fuel supplied by the second fuel supply unit to control the excess air ratio in the reforming cylinder within a predetermined range in which the reformed gas is generated. Fuel that is the ratio of the total amount of fuel supplied to all the normal cylinders by the first fuel supply unit to the total amount of fuel supplied to all the reforming cylinders by the second fuel supply unit in the running state When executing fuel ratio decrease control that decreases the ratio,
6. The excess air ratio in the reforming cylinder is controlled based on the gas component concentration measured by the reformed gas component concentration measuring unit in the excess air ratio control. The engine system described in . In the excess air ratio control, the control device controls the excess air ratio in the reforming cylinder based on the gas component concentration measured by the reformed gas component concentration measurement unit, The engine system according to any one of claims 1 to 6, wherein a reformed gas operation is performed in which only the reformed gas is introduced as the fuel into the normal cylinders. The engine system according to any one of claims 1 to 7, comprising a reforming engine including at least one reforming cylinder as the plurality of cylinders, and an external output engine including the normal cylinder as the plurality of cylinders. .

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