JP2015048831A - Engine, heat pump device and heat value estimation method of fuel gas - Google Patents

Abstract

A heat generation amount of a fuel gas is estimated by a relatively simple configuration without providing a means for directly measuring the heat generation amount of the fuel gas. An air-fuel ratio control means 52 adjusts the opening of a fuel flow rate adjustment valve 14 based on the output of an oxygen sensor 32 in a state where an engine 60 is operated by supplying a fuel gas whose heat generation amount is to be estimated. As a result, the combustion state in the combustion chamber 20 is changed to the stoichiometric state, and the fuel gas subject to the calorific value estimation is based on the opening degree of the fuel flow rate adjusting valve 14 in the stoichiometric state and the first correspondence relationship stored in the storage unit 51. Is provided with a heat generation amount estimation means 53 for estimating the heat generation amount. [Selection] Figure 1

Description

  The present invention relates to a fuel flow rate adjusting valve that adjusts the flow rate of fuel gas, a combustion chamber that burns a mixed gas of fuel gas and combustion air, and an exhaust passage through which exhaust gas flows from the combustion chamber. An engine having an oxygen sensor for measuring the oxygen concentration, and an air-fuel ratio control means for controlling the air-fuel ratio by adjusting the opening of the fuel flow rate adjustment valve based on the measurement result of the oxygen sensor, compressed by the engine TECHNICAL FIELD The present invention relates to a gas engine driven heat pump device in which a machine is driven, and a method for estimating a calorific value of fuel gas.

As the fuel gas supplied to the engine, natural gas containing flammable gas such as ethane, propane, butane and the like, which is mainly composed of methane, may be used. Such natural gas may have a different calorific value because its composition may be different when its production area is different.
Furthermore, today, biogas produced using technology such as methane fermentation is sometimes used as fuel gas. In general, biogas has a lower calorific value than city gas. Therefore, when the fuel gas is supplied to the engine, the amount of heat generated may change.
For a gas engine using a fuel gas whose calorific value changes due to a variation in composition for the reasons described above, the calorific value for measuring the calorific value of the fuel gas in a fuel supply path for supplying the fuel gas to the engine It has also been proposed to control the fuel supply amount by providing a measurement means and adjusting the valve opening degree of the fuel supply valve based on the measurement result of the calorific value measurement means (see Patent Document 1).

JP 2003-328800 A

  However, as shown in Patent Document 1, since the calorific value measuring means provided for measuring the calorific value of the fuel gas is expensive, no calorific value measuring means for directly measuring such calorific value is provided, Development of a method and apparatus for estimating the calorific value of fuel gas has been desired.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to estimate the calorific value of the fuel gas even with a relatively simple configuration in which a means for directly measuring the calorific value of the fuel gas is not provided. A possible engine, an engine-driven heat pump device, and a calorific value estimation method are provided, and an engine that can be operated following fluctuation of the calorific value based on the estimated calorific value and an engine-driven heat pump device are provided. There is to do.

In order to achieve the above object, an engine of the present invention provides:
A fuel flow control valve for adjusting the flow rate of the fuel gas;
An oxygen sensor that measures the oxygen concentration of the exhaust gas in an exhaust passage through which the exhaust gas from the combustion chamber that burns the mixed gas of fuel gas and combustion air flows;
An engine comprising air-fuel ratio control means for controlling the air-fuel ratio by adjusting the opening of the fuel flow rate adjustment valve based on the measurement result of the oxygen sensor, the characteristic configuration of which is
A memory for storing a first correspondence relationship between the degree of opening of the fuel flow rate adjustment valve and the amount of heat generated by the fuel gas when an engine is operated in a stoichiometric state by supplying fuel gas with a known amount of heat generated Part
The combustion chamber is adjusted by adjusting the opening of the fuel flow rate adjustment valve by the air-fuel ratio control means on the basis of the output of the oxygen sensor in a state where the fuel gas to be subjected to heat generation estimation is supplied and the engine is operated. The combustion state at is a stoichiometric state, and based on the opening degree of the fuel flow rate adjustment valve in the stoichiometric state and the first correspondence stored in the storage unit, It is in the point provided with the calorific value estimating means to estimate.

The calorific value estimation method of the present invention for achieving the above object is as follows.
A fuel flow control valve for adjusting the flow rate of the fuel gas;
An oxygen sensor that measures the oxygen concentration of the exhaust gas in an exhaust passage through which the exhaust gas from the combustion chamber that burns the mixed gas of fuel gas and combustion air flows,
A method for estimating the calorific value of fuel gas by an engine configured to control the air-fuel ratio by adjusting the opening of the fuel flow rate adjustment valve based on the measurement result of the oxygen sensor, the characteristic configuration is:
A memory for storing a first correspondence relationship between the degree of opening of the fuel flow rate adjustment valve and the amount of heat generated by the fuel gas when an engine is operated in a stoichiometric state by supplying fuel gas with a known amount of heat generated Part
The combustion is performed by adjusting the opening of the fuel flow rate adjustment valve by the air-fuel ratio control means based on the output of the oxygen sensor in a state where the fuel gas to be subjected to heat generation estimation is supplied and the engine is operated. The combustion state in the chamber is a stoichiometric state, and based on the opening degree of the fuel flow rate adjustment valve in the stoichiometric state and the first correspondence stored in the storage unit, the calorific value of the fuel gas that is the calorific value estimation target It is in the point which has the calorific value estimation process which presumes.

According to the above characteristic configuration, the opening of the fuel flow rate adjustment valve is adjusted by the air-fuel ratio control means based on the output of the oxygen sensor, and the combustion state of the engine is adjusted to the stoichiometric state. Here, the first correspondence relationship of the calorific value of the fuel gas corresponding to the opening degree of the fuel flow rate adjustment valve when the engine is operated in the stoichiometric state by supplying the fuel gas whose calorific value is known to the storage unit Is stored, based on the first correspondence relationship and the adjusted opening of the fuel flow rate adjustment valve, it is possible to estimate the heat value of the current fuel gas (the fuel gas that is the target of heat value estimation).
That is, according to the present invention, the basic configuration of a general engine without the need for an expensive calorimeter for measuring the calorific value of fuel gas, and the simple configuration of operating the engine in a stoichiometric state, The amount of heat generated by the fuel gas can be estimated from the valve opening in the state, and based on the estimated result, an engine that can achieve an appropriate operating state according to the amount of heat generated by the currently supplied fuel gas is realized. it can.

Further features of the engine of the present invention are as follows:
When the calorific value of the fuel gas estimated by the calorific value estimation means is smaller than the original calorific value of the fuel gas supplied so far, the opening of the fuel flow rate adjustment valve is adjusted to the larger side,
When it is larger than the original heating value, there is provided a first opening degree adjusting means for adjusting the opening degree of the fuel flow rate adjusting valve to a smaller side.

  According to the above characteristic configuration, since the first opening degree adjusting means adjusts the opening degree of the fuel flow rate adjustment valve, after performing the heat generation amount estimation with simple control, the opening degree of the fuel flow rate adjustment valve is set to the current level. It is possible to follow the fuel gas (the fuel gas whose calorific value is to be estimated).

Further features of the engine of the present invention are as follows:
The storage unit stores a second correspondence relationship that is a relationship between an air-fuel ratio at which the engine can be properly operated and an opening degree of the fuel flow rate adjustment valve, for each calorific value of the fuel gas whose calorific value is known,
Based on the calorific value of the fuel gas estimated by the calorific value estimation means and a separately determined target air-fuel ratio, an opening of a fuel flow rate adjustment valve for maintaining the engine in an appropriate operating state is determined from the second correspondence relationship. The second opening degree adjusting means for deriving the degree and adjusting the opening degree of the fuel flow rate adjustment valve.

According to the above characteristic configuration, the storage unit stores the second correspondence relationship between the air-fuel ratio at which the engine can be properly operated and the opening of the fuel flow rate adjustment valve for each heat generation amount. Further, based on the target air-fuel ratio determined separately from conditions such as the use of the engine, the opening degree of the fuel flow rate adjustment valve for maintaining the engine in an appropriate operating state is derived from the second correspondence relationship, and the second opening degree adjustment is performed. By adjusting the opening of the fuel flow control valve by means, the engine can be maintained in an appropriate state.
That is, even when the heat generation amount fluctuates, the opening degree control of the fuel flow control valve can be executed in a form that follows the fluctuating heat generation amount.

The characteristic configuration of the engine-driven heat pump device of the present invention is:
The compressor is driven by the shaft output of the engine.

  According to the above characteristic configuration, the engine-driven heat pump device includes the compressor driven by the shaft output of the gas engine that performs an appropriate operation following the change in the calorific value of the fuel gas. Appropriate operation based on the change in quantity can be executed.

Schematic configuration diagram of an engine-driven heat pump device according to the present invention The graph which shows the relationship between the opening degree of a fuel flow control valve and the output (air-fuel ratio) of an oxygen sensor at the time of operating the fuel gas of different calorific value near the stoichiometric state Control flow diagram related to operation based on estimation of calorific value of fuel gas and estimated calorific value

The engine 60 of the present invention, the engine-driven heat pump apparatus 100 using the engine 60 as a drive source, and the fuel gas calorific value estimation method by the engine 60 can calculate the calorific value of the fuel gas G without using an expensive calorimeter. The present invention relates to an engine that can be estimated and that can freely adjust the operation state of the engine 60 to an appropriate one based on the estimated calorific value.
Hereinafter, those configurations will be described in order.

  As shown in FIG. 1, the engine 60 of the present invention includes a combustion chamber 20 that burns an air-fuel mixture of a fuel gas G guided from a fuel flow path 13 and combustion air A guided from an air supply path 10, and the combustion An exhaust passage 31 is provided for guiding the exhaust gas E after the mixed gas is combusted in the chamber 20 to the outside.

A fuel flow path 13 provided with a fuel flow rate adjusting valve 14 that allows the fuel gas G to flow and adjusts the flow rate of the fuel gas G through the supply air path 10 is a combustion air A that flows through the air supply path 10. The fuel gas G flowing through the fuel flow path 13 in a state of maintaining a constant flow rate ratio with respect to the flow rate is connected via a venturi mixer 11 that mixes the combustion air A in the air supply path 10.
The air supply path 10 includes a throttle valve 12 that adjusts the flow rate of the air-fuel mixture on the downstream side of the venturi mixer 11, and is connected to the combustion chamber 20 via the air supply valve 15 on the downstream side of the throttle valve 12. .

The combustion chamber 20 includes a hollow cylindrical cylinder 25 and an upper surface of a piston 22 that can slide inside the cylinder 25. The piston 22 is provided with a connecting rod 23 that transmits the sliding movement in the cylinder 25 to the crankshaft 24 of the engine 60.
A cylinder head that is an upper surface of the cylinder 25 is provided with an ignition plug 21 that ignites an air-fuel mixture of the fuel gas G supplied to the combustion chamber 20 and the combustion air A, and the ignition plug 21 is compressed. The air-fuel mixture is combusted and expanded in such a manner that the air-fuel mixture is ignited, and the piston 22 is slid and moved in the cylinder 25.

The exhaust passage 31 connected to the combustion chamber 20 via the exhaust valve 30 is provided with an oxygen sensor 32 that detects the oxygen concentration of the exhaust gas E flowing through the exhaust passage 31.
Usually, the oxygen sensor is provided upstream of a three-way catalyst (not shown) provided in the exhaust passage 31 for the purpose of controlling the ratio between the fuel gas G and the combustion air A, and the deterioration detection of the catalyst. For the purpose of, etc., there are those provided downstream of the three-way catalyst.
The oxygen sensor 32 of the present invention is intended to control the ratio between the fuel gas G and the combustion air A.
As shown in FIG. 2, the output of the oxygen sensor 32 is obtained by adjusting the opening of the fuel flow rate adjusting valve 14, that is, adjusting the supply amount of the fuel gas G, so that the stoichiometric combustion state (excess air ratio = In the vicinity of the actual air-fuel ratio / theoretical air-fuel ratio = 1.0), a steep change (change between 0.2 V and 0.7 V in FIG. 2) occurs.
Therefore, the control device 50 sets the opening of the fuel flow rate adjustment valve 14 so that the output of the oxygen sensor 32 has a value that changes sharply, that is, a value between 0.2V and 0.7V in FIG. By controlling, the engine 60 can be maintained in the stoichiometric combustion state (the excess air ratio = the actual air / fuel ratio / theoretical air / fuel ratio = 1.0).
In the case where a three-way catalyst (not shown) is provided in the exhaust passage 31, it is possible to satisfactorily remove HC, CO, and NOx contained in the exhaust gas E by maintaining the engine 60 in a stoichiometric combustion state. Can do.

  In the present invention, the air-fuel ratio control means 52 adjusts the air-fuel ratio by adjusting the opening of the fuel flow rate adjustment valve 14 based on the oxygen concentration detected by the oxygen sensor 32. It is possible to switch between a lean operation that operates in a lean combustion state, a stoichiometric operation that operates in a stoichiometric state with a stoichiometric air-fuel ratio, and a rich operation that operates in a rich combustion state. ing.

The crankshaft 24 of the engine 60 is connected to the rotating shaft of the compressor 40 of the heat pump apparatus 100 by a connecting member (not shown), and the compressor 40 is driven by the shaft output of the engine 60.
The engine-driven heat pump apparatus 100 using the engine 60 as a drive source dissipates heat in the refrigerant circuit C that circulates the refrigerant L, the compressor 40 that compresses the refrigerant, and the refrigerant L that is compressed and heated by the compressor 40. The condenser 41, the expansion valve 42 that expands the refrigerant L after passing through the condenser 41, and the evaporator 43 that absorbs heat by the refrigerant L that has been expanded by the expansion valve 42 and cooled down are provided in the order of description. .

The engine 60 and the engine-driven heat pump apparatus 100 of the present invention are configured as described above, but the fuel gas G supplied as fuel includes hydrocarbon gases such as methane, ethane, butane, propane, and the like. Since it is a natural gas, the composition of the hydrocarbon gas contained in the natural gas varies for reasons such as different production areas, so the calorific value varies within a predetermined range. In this example, the variation range of the calorific value of the fuel gas, from 40 MJ / Nm ³ is the lowest heating value, in anticipation of the case that varies in a relatively large change width of up to 46 mJ / Nm ³ is the highest heating value Yes. For this reason, even if the fluctuation range of the calorific value of the fuel gas G becomes large, it is desirable that the engine 60 appropriately operates following the fluctuation of the calorific value.
Therefore, in the engine 60 and the engine driven heat pump apparatus 100 of the present invention, the heat generation amount of the fuel gas G is estimated by the following method.

[Estimation of calorific value of fuel gas]
In the engine 60 and the engine-driven heat pump apparatus 100 of the present invention, in order to estimate the fluctuation of the calorific value of the fuel gas G, the fuel gas whose calorific value is known is supplied and the stoichiometric state (the excess air ratio) = Actual air / fuel ratio / theoretical air / fuel ratio = 1.0) A storage unit 51 that stores the first correspondence relationship that is the relationship between the opening of the fuel flow rate adjustment valve 14 and the amount of heat generated by the fuel gas G when the engine is operated. It has. Further, the opening degree of the fuel flow rate adjustment valve 14 is adjusted by the air-fuel ratio control means 52 based on the output of the oxygen sensor 32 in a state where the fuel gas G to be subjected to heat generation estimation is supplied and the engine 60 is operated. Thus, the combustion state in the combustion chamber 20 is changed to the stoichiometric state, and the fuel gas to be subjected to the calorific value estimation is based on the opening degree of the fuel flow rate adjusting valve 14 in the stoichiometric state and the first correspondence relationship stored in the storage unit 51. A calorific value estimation means 53 for estimating the calorific value of G is provided.

  That is, in the present invention, for every calorific value of the fuel gas G whose calorific value is known, the fuel gas G whose calorific value is known is supplied and stoichiometric (excess air ratio = actual air fuel ratio / Since the opening degree of the fuel flow rate adjustment valve 14 when the engine is operated at the theoretical air-fuel ratio = 1.0) is stored in the storage unit 51 as the first correspondence relationship, the heat generation amount of the supplied fuel gas G is unknown. Even in this case, the calorific value of the fuel gas G can be estimated from the opening degree of the fuel flow rate adjustment valve 14 when the stoichiometric state is adjusted.

The relationship between the calorific value of the fuel gas G, the opening of the fuel flow rate adjustment valve 14, and the air-fuel ratio will be described with reference to the graph of FIG.
In the graph shown in FIG. 2, the horizontal axis indicates the opening degree of the fuel flow rate adjustment valve 14 (corresponding to the supply amount of the fuel gas G), and the opening degree of the fuel flow rate adjustment valve 14 increases as the number of steps increases. It shows that the fuel gas G shifts to the side (the side where the supply amount of the fuel gas G increases). The vertical axis indicates the output of the oxygen sensor 32, and the higher the output, the lower the oxygen concentration of the exhaust gas E (the air-fuel ratio is low).
When the output of the oxygen sensor 32 changes sharply (when it changes between 0.2V and 0.7V in FIG. 2), the air-fuel ratio is the stoichiometric air-fuel ratio, and excess air Rate = actual air / fuel ratio / theoretical air / fuel ratio = 1.0.
FIG. 2 shows a graph when two different calorific values of the fuel gas G are used, and the graph on the right side shows the case where the calorific value of the fuel gas G is 40 MJ / Nm ^3. The graph on the left shows the case where the calorific value of the fuel gas G is 46 MJ / Nm ³ .

From the relationship shown in the graph, when the opening degree of the fuel flow rate adjustment valve 14 in the stoichiometric operation is about 552 steps, the calorific value of the fuel gas G is 40 MJ / Nm ³ and the fuel flow rate in the stoichiometric operation. When the opening degree of the regulating valve 14 is about 500 steps, it can be estimated that the calorific value of the fuel gas G is 46 MJ / Nm ³ . Regarding these intermediate heat generation amounts, the heat generation amount decreases as the number of steps increases. Therefore, taking this example, the first correspondence described above is that the heating value of the fuel gas is 46 MJ / Nm ³ with respect to the opening (498 to 500), and the opening (550 to 552). On the other hand, the calorific value of the fuel gas is 40 MJ / Nm ³ , and the relationship between the opening degree and the calorific value is a linear relationship between these values.
That is, the first correspondence relationship stored in the storage unit 51 is, for example, the relationship shown in FIG. 2 quantified and stored in a map for each calorific value of the fuel gas G. Based on this, the calorific value of the fuel gas G can be appropriately estimated from the valve opening when the engine 60 is actually operated in the stoichiometric state.

  In the engine of the present invention, as described above, it is possible to estimate the calorific value of the fuel gas only by setting the calorific value of the fuel gas G to the stoichiometric state. Therefore, this operation can be performed at regular intervals with a single engine while maintaining engine operation. In other words, the normal load operation can be executed when the calorific value is not estimated.

[Adjustment of fuel flow adjustment valve opening based on estimated heat generation]
As described above, the calorific value of the fluctuating fuel gas G is appropriately estimated. However, in the present invention, the fuel flow rate is determined based on the calorific value of the fuel gas G thus estimated. The opening degree of the adjusting valve 14 is adjusted, and the flow rate of the supplied fuel is adjusted so as to follow the change in the calorific value of the fuel gas G.
When the explanation is added, the storage unit 51 stores the heat generation amount of the fuel gas G that has been supplied to the engine so far as the original heat generation amount.
When the estimated heat value of the currently supplied fuel gas G is smaller than the original heat value, it is determined that the heat value of the fuel gas G has decreased, and the conventional combustion state is maintained ( In order to maintain the excess air ratio), the opening degree of the fuel flow rate adjustment valve 14 is adjusted to be larger than the opening degree of the fuel flow rate adjustment valve 14 when the fuel gas of the original calorific value is supplied and the operation is continued. To do. On the other hand, if the estimated calorific value of the currently supplied fuel gas G is larger than the original calorific value, it is determined that the calorific value of the fuel gas G has increased, and in order to maintain the conventional combustion state ( In order to maintain the excess air ratio), the opening of the fuel flow rate adjustment valve 14 is adjusted to a smaller side than the opening amount of the fuel flow rate adjustment valve 14 when the fuel gas of the original calorific value is supplied and the operation is continued. First opening degree adjusting means 54 is provided.
As a result, the engine 60 of the present invention can be operated in a state of following the change in the calorific value of the fuel gas G.

[Control flow]
Next, the flow relating to the estimation of the calorific value of the fuel gas G in the present invention and the control of the opening of the fuel flow control valve 14 so as to follow the estimated calorific value will be described based on FIG.
The engine 60 is started (# 01). Here, when the engine 60 is started, for example, it is assumed that the heat value of the fuel gas G is a standard heat value.

  Next, when estimating the calorific value of the fuel gas G, the air-fuel ratio control means 52 determines the opening of the fuel flow rate adjustment valve 14 based on the measurement result of the oxygen sensor 32, and the combustion state of the engine 60 is stoichiometric ( Control is performed so that the excess air ratio = actual air / fuel ratio / theoretical air / fuel ratio = 1.0) (# 02).

  In this state, the calorific value estimation means 53 is controlled by the air / fuel ratio control means 52 so that the stoichiometric state (excess air ratio = actual air / fuel ratio / theoretical air / fuel ratio = 1.0). And a first correspondence relationship stored in the storage unit 51, a heat generation amount estimation step for estimating the current heat generation amount of the fuel gas G is executed (# 03).

When the estimated heating value of the fuel gas G is different from the standard heating value (# 04), the first opening degree adjusting means 54 adjusts the opening degree of the fuel flow rate adjusting valve 14 (# 05).
Specifically, the estimated calorific value of the fuel gas G is smaller than the original calorific value (an example of a standard calorific value) of the fuel gas supplied in the operation described before the calorific value estimation described above. The opening degree of the fuel flow rate adjustment valve 14 is adjusted to the side larger than the opening degree employed at that time, and when it is larger than the original heating value, the opening degree of the fuel flow rate adjustment valve 14 is adjusted to the smaller side.
On the other hand, when the estimated calorific value of the fuel gas G is equal to the original calorific value (# 04), the opening of the fuel flow rate adjusting valve 14 is maintained at the current level.

[Another embodiment]
(1) In the above embodiment, when the opening degree of the fuel flow rate adjustment valve 14 is adjusted based on the estimated heat generation amount of the fuel gas G, the first opening degree adjusting means 54 The opening degree of the fuel flow rate adjustment valve 14 was adjusted in a form in which the calorific value and the original calorific value were compared.
However, the adjustment of the opening degree of the fuel flow rate adjustment valve 14 based on the estimated calorific value of the fuel gas G may be adjusted by the following configuration and method.
That is, the storage unit 51 stores, for each calorific value of the fuel gas G, the second correspondence relationship that is the relationship between the air-fuel ratio at which the engine 60 can be properly operated and the opening of the fuel flow rate adjustment valve 14, and the calorific value. Based on the calorific value of the fuel gas G estimated by the estimating means 53 and a separately determined target air-fuel ratio, a second opening degree adjustment for adjusting the opening degree of the fuel flow rate adjustment valve 14 from the second correspondence relationship. You may comprise so that a means (not shown) may be provided.
According to the said structure, since the memory | storage part 51 has memorize | stored the 2nd correspondence of the air fuel ratio which can operate the engine 60 appropriately for every calorific value, and the opening degree of the fuel flow control valve 14, the estimated fuel Based on the calorific value of the gas G and the target air-fuel ratio separately determined from conditions such as the use of the engine, the opening degree of the fuel flow rate adjustment valve 14 that maintains the engine 60 in the proper operating state is determined from the second correspondence relationship. Thus, the opening of the fuel flow rate adjustment valve is adjusted by the second opening adjustment means, and the engine 60 can be maintained in an appropriate state.

  The engine, engine-driven heat pump device, and fuel gas calorific value estimation method according to the present invention have a relatively simple configuration that does not include a calorific value measuring means for directly measuring the calorific value of the fuel gas, and thus the calorific value of the fuel gas. Therefore, the engine can be effectively used as an engine that can be operated in a state of following the estimated calorific value and an engine-driven heat pump device.

14: Fuel flow rate adjustment valve 20: Combustion chamber 31: Exhaust passage 32: Oxygen sensor 40: Compressor 50: Engine 51: Storage unit 52: Air-fuel ratio control means 53: Heat generation amount estimation means 54: First opening degree adjustment means 100 : Engine-driven heat pump device A: Combustion air C: Refrigerant circuit E: Exhaust gas G: Fuel gas L: Refrigerant

Claims (5)

A fuel flow control valve for adjusting the flow rate of the fuel gas;
An oxygen sensor that measures the oxygen concentration of the exhaust gas in an exhaust passage through which the exhaust gas from the combustion chamber that burns the mixed gas of fuel gas and combustion air flows;
An engine comprising air-fuel ratio control means for controlling the air-fuel ratio by adjusting the opening of the fuel flow rate adjustment valve based on the measurement result of the oxygen sensor;
A memory for storing a first correspondence relationship between the degree of opening of the fuel flow rate adjustment valve and the amount of heat generated by the fuel gas when an engine is operated in a stoichiometric state by supplying fuel gas with a known amount of heat generated Part
The combustion chamber is adjusted by adjusting the opening of the fuel flow rate adjustment valve by the air-fuel ratio control means on the basis of the output of the oxygen sensor in a state where the fuel gas to be subjected to heat generation estimation is supplied and the engine is operated. The combustion state at is a stoichiometric state, and based on the opening degree of the fuel flow rate adjustment valve in the stoichiometric state and the first correspondence stored in the storage unit, An engine having a calorific value estimating means for estimating. When the calorific value of the fuel gas estimated by the calorific value estimation means is smaller than the original calorific value, which is the calorific value of the fuel gas supplied so far, the opening of the fuel flow rate adjustment valve is adjusted to the larger side. And
2. The engine according to claim 1, further comprising: a first opening degree adjusting unit that adjusts an opening degree of the fuel flow rate adjusting valve to a smaller side when the amount of heat generation is larger than the original heat generation amount. The storage unit stores a second correspondence relationship that is a relationship between an air-fuel ratio at which the engine can be properly operated and an opening degree of the fuel flow rate adjustment valve, for each calorific value of the fuel gas whose calorific value is known,
Based on the calorific value of the fuel gas estimated by the calorific value estimation means and a separately determined target air-fuel ratio, an opening of a fuel flow rate adjustment valve for maintaining the engine in an appropriate operating state is determined from the second correspondence relationship. The engine according to claim 1, further comprising second opening degree adjusting means for deriving a degree and adjusting an opening degree of the fuel flow rate adjusting valve.   An engine-driven heat pump apparatus comprising a compressor driven by the engine shaft output according to claim 1. A fuel flow control valve for adjusting the flow rate of the fuel gas;
An oxygen sensor that measures the oxygen concentration of the exhaust gas in an exhaust passage through which the exhaust gas from the combustion chamber that burns the mixed gas of fuel gas and combustion air flows,
A method for estimating a calorific value of fuel gas by an engine configured to control an air-fuel ratio by adjusting an opening of the fuel flow rate adjustment valve based on a measurement result of the oxygen sensor,
A memory for storing a first correspondence relationship between the degree of opening of the fuel flow rate adjustment valve and the amount of heat generated by the fuel gas when an engine is operated in a stoichiometric state by supplying fuel gas with a known amount of heat generated Part
The combustion is performed by adjusting the opening of the fuel flow rate adjustment valve by the air-fuel ratio control means based on the output of the oxygen sensor in a state where the fuel gas to be subjected to heat generation estimation is supplied and the engine is operated. The combustion state in the chamber is a stoichiometric state, and based on the opening degree of the fuel flow rate adjustment valve in the stoichiometric state and the first correspondence stored in the storage unit, the calorific value of the fuel gas that is the calorific value estimation target A method for estimating the calorific value of a fuel gas, comprising a calorific value estimating step of estimating the fuel gas.

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