Engine system, cogeneration equipment, and control method thereof

Abstract

In a main fuel system where the mixing ratio of a first fuel containing hydrocarbon gas and hydrogen is variable, operation is performed while maintaining high thermal efficiency even when the mixing ratio of the main fuel is changed. [Solution] The control device R performs ignition timing determination control to determine the mixed fuel ignition timing, which is the MBT ignition timing of a mixed fuel in which a first fuel and hydrogen are mixed, to be an ignition timing between the first fuel ignition timing and the hydrogen ignition timing, according to the first fuel ignition timing which is the MBT ignition timing when the fuel is only the first fuel, the hydrogen ignition timing which is the MBT ignition timing when the fuel is only hydrogen, and the calorific value ratio of hydrogen in the mixed fuel.

Description

Technical Field

[0001] The present invention relates to an engine system that includes a control device for controlling operation and burns fuel containing at least one of a first fuel containing hydrocarbon gas and hydrogen in a combustion chamber, and a control method for the same.

Background Art

[0002] Conventionally, various engine systems using ammonia as a main component have been proposed. In view of the flame-retardant property of ammonia, an engine system is known in which part of ammonia is reformed into highly ignitable hydrogen, and the reformed hydrogen is used as fuel together with ammonia. From another perspective, this engine system is an engine system driven by different fuels as power sources, and a configuration is disclosed in which the engine is driven in a mode using ammonia as one fuel and hydrogen as the other fuel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] Although the engine system disclosed in Patent Document 1 discloses operation by mixing different fuels, there is no disclosure or suggestion on how to set various operation indices when operating by mixing fuels with different properties, and there is room for improvement in realizing a further highly efficient engine.

[0005] The present invention has been made in view of the above-mentioned problems, and its objective is to provide an engine system, a cogeneration facility, and a control method thereof that can operate while maintaining high thermal efficiency even when the mixing ratio of a mixed fuel, in which the mixing ratio of a first fuel containing hydrocarbon gas and hydrogen is variable. [Means for solving the problem]

[0006] The engine system for achieving the above objective is: An engine system equipped with a control device for controlling operation, which burns a fuel containing at least one of a first fuel containing hydrocarbon gas and hydrogen in a combustion chamber, the characteristic configuration of which is: The control device performs ignition timing determination control to determine the mixed fuel ignition timing, which is the MBT ignition timing of a mixed fuel obtained by mixing the first fuel and the hydrogen, to be an ignition timing between the first fuel ignition timing and the hydrogen ignition timing, according to the first fuel ignition timing which is the MBT ignition timing when the fuel is only the first fuel, the hydrogen ignition timing which is the MBT ignition timing when the fuel is only the hydrogen, and the calorific value ratio of the hydrogen in the mixed fuel.

[0007] A control method for an engine system to achieve the above objective is: A control method for an engine system that burns a fuel containing at least one of a first fuel containing methane and hydrogen in a combustion chamber, the characteristic configuration thereof is: The key feature is the execution of ignition timing determination control, which determines the mixed fuel ignition timing, which is the MBT ignition timing of a mixed fuel obtained by mixing the first fuel and the hydrogen, to be an ignition timing between the first fuel ignition timing and the hydrogen ignition timing, according to the first fuel ignition timing, which is the MBT ignition timing when the fuel is only the first fuel, the hydrogen ignition timing, which is the MBT ignition timing when the fuel is only the hydrogen, and the calorific value ratio of the hydrogen in the mixed fuel.

[0008] Ignition timing is one of the indicators of engine operation, and it is known that the MBT ignition timing, which maximizes thermal efficiency, differs for each fuel. However, there was insufficient knowledge about how the MBT ignition timing changes when different fuels are mixed. As a result of diligent research, the inventors of this invention have found that there is a correlation between the calorific value ratio of fuels in a fuel mixture and the MBT ignition timing of the fuel mixture, as shown in the graphs in Figures 2 and 3. In other words, as described in the above characteristic configuration, the control device performs ignition timing determination control to determine the mixed fuel ignition timing, which is the MBT ignition timing for a mixed fuel of first fuel and hydrogen, to be between the first fuel ignition timing and the hydrogen ignition timing, according to the MBT ignition timing when only first fuel is used, the hydrogen ignition timing when only hydrogen is used, and the calorific value ratio of hydrogen in the mixed fuel. By controlling the operation of the engine based on this ignition timing determination control, the thermal efficiency when using mixed fuel can be further improved. Based on the above, in a mixed fuel in which the mixing ratio of a first fuel containing hydrocarbon gas and hydrogen is variable, it is possible to realize an engine system and a control method thereof that can operate while maintaining high thermal efficiency even when the mixing ratio of the mixed fuel is changed.

[0009] More specifically, in the engine system according to the present invention, In the ignition timing determination control, the control device, The ignition timing of the mixed fuel is determined such that the lower the calorific value of hydrogen in the mixed fuel, the closer it is to the first fuel ignition timing between the first fuel ignition timing and the hydrogen ignition timing, and the higher the calorific value of hydrogen in the mixed fuel, the closer it is to the hydrogen ignition timing between the first fuel ignition timing and the hydrogen ignition timing.

[0010] More preferably, the control device is When operating at a predetermined engine speed and a predetermined excess air ratio, and when the heat ratio of hydrogen in the mixed fuel is at a predetermined heat ratio, Based on the first fuel ignition timing and the hydrogen ignition timing determined for each engine speed and the excess air ratio, and a predetermined heat ratio of hydrogen in the mixed fuel, the ignition timing determination control is performed. It is preferable to perform mixed fuel operation using the mixed fuel ignition timing determined by the ignition timing determination control described above.

[0011] This control system allows for the determination of the ignition timing that maximizes thermal efficiency, based on indicators such as engine speed, air-fuel ratio, and hydrogen mixture ratio in the fuel mixture, thereby enabling the engine to operate with higher thermal efficiency.

[0012] In the engine systems described so far, In the ignition timing determination control, the control device, It is preferable to determine the mixed fuel ignition timing in such a way that the higher the calorific value of hydrogen in the mixed fuel, the more retarded the ignition timing between the first fuel ignition timing and the hydrogen ignition timing becomes.

[0013] Further characteristic features of the engine system are: The control device is The system is configured to perform carbon concentration determination control, which determines whether or not the carbon dioxide concentration in the combustion exhaust gas from the combustion chamber exceeds a predetermined decarbonization threshold. In the carbon concentration determination control, if it is determined that the carbon dioxide concentration exceeds the decarbonization threshold, a hydrogen ratio increase correction control is performed to increase the calorific value ratio of hydrogen in the mixed fuel, and the ignition timing determination control is performed based on the calorific value ratio of hydrogen in the mixed fuel after the increase correction of the calorific value ratio of hydrogen in the hydrogen ratio increase correction control.

[0014] This allows the ignition timing to be adjusted to an appropriate value while simultaneously improving the thermal efficiency of the engine when using a mixed fuel, by reducing the carbon dioxide concentration in the combustion exhaust gas to below the decarbonization threshold and thus reducing the carbon content of the combustion exhaust gas.

[0015] Further, according to the cogeneration facility including the engine system described so far, it is possible to realize a cogeneration facility that can favorably exhibit the operational effects achieved by the engine system described so far. Brief Description of the Drawings

[0016] [Figure 1] It is a schematic configuration diagram of the engine system according to the embodiment of the present invention. [Figure 2] It is a graph showing the MBT ignition timing for each calorific value ratio of hydrogen in the mixed fuel of the first fuel and hydrogen (when the excess air ratio is 1). [Figure 3] It is a graph showing the MBT ignition timing for each calorific value ratio of hydrogen in the mixed fuel of the first fuel and hydrogen (when the excess air ratio is 1.66). Modes for Carrying Out the Invention

[0017] The present invention relates to an engine system 100, a cogeneration facility 200, and a control method thereof, which are capable of performing operation while maintaining high thermal efficiency even when the mixing ratio of the mixed fuel is changed, in the mixed fuel with a variable mixing ratio of the first fuel containing hydrocarbon gas and hydrogen according to the embodiment of the present invention. Hereinafter, the engine system 100, the cogeneration facility 200, and the control method thereof according to the present embodiment will be described based on the drawings.

[0018] As shown in FIG. 1, the engine system 100 according to the embodiment is configured to include a control device R that drives in a mode of supplying fuel containing at least one of a first fuel containing hydrocarbon gas (for example, city gas 13A) and hydrogen, and combustion air A to a combustion chamber (not shown) of a spark ignition type engine body 40 for combustion. The engine system 100 includes a combustion air passage pipe L2 through which combustion air A flows, and an air cleaner 21 for purifying the combustion air A, and a throttle valve 22 that can adjust the amount of combustion air A supplied to the combustion chamber by adjusting its opening, all of which are provided in the order described above from the upstream side of the combustion air passage pipe L2.

[0019] Furthermore, the engine body 40 is equipped with a first fuel passage pipe L1 that guides the first fuel to the inlet of the combustion chamber, and a first injector IJ1 which is an electromagnetic fuel injection valve capable of injecting the first fuel guided by the first fuel passage pipe L1 into the inlet of the combustion chamber according to the engine cycle. In addition, the engine body 40 is equipped with a hydrogen flow pipe L3 that guides hydrogen to the inlet of the combustion chamber, and a second injector IJ2 which is an electromagnetic fuel injection valve capable of injecting the hydrogen guided by the hydrogen flow pipe L3 into the inlet of the combustion chamber according to the engine cycle.

[0020] The rotating shaft (not shown) of the engine body 40 is equipped with a rotation speed sensor, which measures the rotation speed of the rotating shaft (not shown), as an operating state detection unit 41. Furthermore, a torque measuring sensor is provided on the rotating shaft (not shown) of the engine body 40 as an operating state detection unit 41 to measure the torque of the rotating shaft. The control device R controls, for example, the fuel injection amount of the first injector IJ1 and the second injector IJ2 and the opening degree of the throttle valve 22 so that the engine output calculated based on the engine speed measured by the rotation speed sensor and the torque measured by the torque measuring sensor becomes the target output. Furthermore, the control device R sets the calorific value ratio of hydrogen in the mixed fuel introduced into the combustion chamber based on the amount (flow rate) of hydrocarbon gas supplied per cycle by the first injector IJ1 and the amount (flow rate) of hydrogen supplied per cycle by the second injector IJ1.

[0021] The exhaust pipe L4 through which combustion exhaust gas E from the engine body 40 passes is equipped with a CO2 sensor S1 capable of measuring the carbon dioxide concentration contained in the combustion exhaust gas E passing through the exhaust pipe L4, and also with a heat exchanger HE that recovers the waste heat from the combustion exhaust gas E. The waste heat from the engine recovered by the heat exchanger HE is used for heating hot water, etc., and is configured as a so-called cogeneration system 200. Furthermore, the shaft output of the engine body 40 is used as a power source to rotate a generator or the like (not shown).

[0022] Now, the engine system 100 and cogeneration equipment 200 described above are configured to perform the following control in order to achieve highly efficient operation even when burning a mixed fuel in the combustion chamber whose MBT ignition timing is not clear when mixed.

[0023] In other words, the control device R performs ignition timing determination control to determine the mixed fuel ignition timing, which is the MBT ignition timing for a mixed fuel of first fuel and hydrogen, to be between the first fuel ignition timing and the hydrogen ignition timing, according to the first fuel ignition timing, which is the MBT ignition timing when the fuel is only first fuel, the hydrogen ignition timing, which is the MBT ignition timing when the fuel is only hydrogen, and the calorific value ratio of hydrogen in the mixed fuel. Furthermore, in ignition timing determination control, if only the first fuel is used, the ignition timing is set to the known first fuel ignition timing, and if only hydrogen is used, the ignition timing is set to the known hydrogen ignition timing.

[0024] To elaborate, the inventors found that, as shown in Figure 2, for example, in a stationary engine system 100 of a cogeneration facility 200, at a typical engine speed (1200 rpm) and with an excess air ratio of 1.0, the mixed fuel ignition timing can be determined in a manner that substantially linearly complements the relationship between the first fuel ignition timing and the hydrogen ignition timing, regardless of whether the heat input to the combustion chamber per cycle is 300 J / cycle, 400 J / cycle, or 500 J / cycle. They also found that the mixed fuel ignition timing tends to approach the first fuel ignition timing as the heat ratio of hydrogen in the mixed fuel decreases, and the higher the heat ratio of hydrogen in the mixed fuel, the closer it tends to approach the hydrogen ignition timing. Furthermore, in this context, determining the ignition timing of the mixed fuel in a "linearly complementary" manner means determining the ignition timing by adding to the hydrogen ignition timing the period obtained by accumulating the heat ratio of hydrogen in the mixed fuel (= heat amount of hydrogen / heat amount of mixed fuel) during the period between the first fuel ignition timing and the hydrogen ignition timing.

[0025] Incidentally, as shown in Figure 3, it has also been found that a similar trend is observed even when the excess air ratio changes to 1.66. Furthermore, the values ​​for each measurement point in the graph in Figure 2 are shown in Table 1, and the values ​​for each measurement point in the graph in Figure 3 are shown in Table 2. Incidentally, the MBT ignition timing on the vertical axis in Figures 2 and 3 represents the BTDCdeg Crank Angle, and a smaller number means a later ignition timing.

[0026] Therefore, in the engine system 100 according to this embodiment, the control device R determines the mixed fuel ignition timing in the ignition timing determination control described above in such a manner that the lower the calorific value ratio of hydrogen in the mixed fuel, the closer the mixed fuel ignition timing is to the first fuel ignition timing between the first fuel ignition timing and the hydrogen ignition timing, and the higher the calorific value ratio of hydrogen in the mixed fuel, the closer the mixed fuel ignition timing is to the hydrogen ignition timing between the first fuel ignition timing and the hydrogen ignition timing.

[0027] To further explain, in the engine system 100 according to this embodiment, when the engine is operated at a predetermined engine speed and a predetermined air-fuel ratio, and the heat ratio of hydrogen in the mixed fuel is a predetermined heat ratio (target heat ratio of hydrogen), the control device R performs ignition timing determination control based on the first fuel ignition timing and hydrogen ignition timing determined for each engine speed and air-fuel ratio, and the predetermined heat ratio of hydrogen in the mixed fuel, and performs mixed fuel operation, which operates at the mixed fuel ignition timing determined by the ignition timing determination control. In other words, the control device R stores a map showing the MBT ignition timing for each percentage of hydrogen's heat content in the fuel mixture, as shown in Figure 2, for each predetermined engine speed and predetermined excess air ratio, and executes fuel mixture operation based on this map. Furthermore, the calorific value ratio of hydrogen in the fuel mixture is determined appropriately based on factors such as the stability of engine combustion and the characteristics of exhaust gases.

[0028] Incidentally, from another perspective, the control device R determines the ignition timing of the mixed fuel in a manner in which the higher the heat content of hydrogen in the mixed fuel, the more the mixed fuel ignition timing is retarded between the first fuel ignition timing and the hydrogen ignition timing.

[0029] Here, we will explain the mechanism by which a higher proportion of hydrogen in the fuel mixture retards the fuel mixture ignition timing between the first fuel ignition timing and the hydrogen ignition timing. When comparing hydrogen and methane, hydrogen has better flammability, and the rate at which the combustion chamber temperature reaches its peak after ignition is steeper. Therefore, under conditions where abnormal combustion such as knocking does not occur, adjusting the combustion center of gravity to approximately 10-15 ATDC Crank Angle will result in the ignition timing of hydrogen being delayed compared to that of methane. Therefore, the higher the calorific value of hydrogen in the fuel mixture, the more the fuel mixture ignition timing is retarded between the first fuel ignition timing and the hydrogen ignition timing.

[0030] [Table 1]

[0031] [Table 2]

[0032] Now, in order to achieve low carbon emissions from combustion exhaust gases, the engine system 100 according to this embodiment can be configured as follows. Specifically, the control device R is configured to perform carbon concentration determination control, which determines whether the carbon dioxide concentration in the combustion exhaust gas E from the combustion chamber (carbon dioxide concentration detected by the CO2 sensor S1) exceeds a predetermined decarbonization threshold. If the carbon concentration determination control determines that the carbon dioxide concentration exceeds the decarbonization threshold, the control device R performs hydrogen ratio increase correction control, which increases the calorific value ratio of hydrogen in the mixed fuel. At the same time, it performs ignition timing determination control based on the calorific value ratio of hydrogen in the mixed fuel after the increase correction performed by the hydrogen ratio increase correction control.

[0033] [Another embodiment] (1) The engine system 100 according to the above embodiment may be configured as a turbocharged engine system, although a detailed explanation will be omitted.

[0034] (2) In the above embodiment, the first fuel was city gas 13A, but the first fuel is not limited to city gas 13A, and various hydrocarbon gases such as methane or natural gas can be used as the first fuel.

[0035] (3) In the above embodiment, carbon concentration determination control and hydrogen ratio increase correction control, and the various operations associated therewith, do not necessarily have to be performed.

[0036] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, provided that no inconsistencies arise. Moreover, the embodiments disclosed herein are illustrative, 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. [Industrial applicability]

[0037] The engine system, cogeneration equipment, and control method of the present invention can be effectively used as an engine system, cogeneration equipment, and control method that can operate while maintaining high thermal efficiency even when the mixing ratio of the mixed fuel is changed, in a mixed fuel in which the mixing ratio of a first fuel containing hydrocarbon gas and hydrogen is variable. [Explanation of Symbols]

[0038] 13A: City gas 50: Control device 100: Engine System 200: Cogeneration equipment A: Combustion air E: Combustion exhaust gas R: Control device

Claims

1. An engine system equipped with a control device for controlling operation, which burns a fuel containing at least one of a first fuel containing hydrocarbon gas and hydrogen in a combustion chamber, The control device performs ignition timing determination control to determine the mixed fuel ignition timing, which is the MBT ignition timing of a mixed fuel obtained by mixing the first fuel and the hydrogen, to be an ignition timing between the first fuel ignition timing and the hydrogen ignition timing, according to the first fuel ignition timing which is the MBT ignition timing when the fuel is only the first fuel, the hydrogen ignition timing which is the MBT ignition timing when the fuel is only the hydrogen, and the calorific value ratio of the hydrogen in the mixed fuel.

2. In the ignition timing determination control, the control device, The engine system according to claim 1, wherein the mixed fuel ignition timing is determined in such a manner that the lower the calorific value ratio of hydrogen in the mixed fuel, the closer it is to the first fuel ignition timing between the first fuel ignition timing and the hydrogen ignition timing, and the higher the calorific value ratio of hydrogen in the mixed fuel, the closer it is to the hydrogen ignition timing between the first fuel ignition timing and the hydrogen ignition timing.

3. The control device is When operating at a predetermined engine speed and a predetermined excess air ratio, and when the heat ratio of hydrogen in the mixed fuel is at a predetermined heat ratio, Based on the first fuel ignition timing and the hydrogen ignition timing determined for each engine speed and the excess air ratio, and a predetermined heat ratio of hydrogen in the mixed fuel, the ignition timing determination control is performed. The engine system according to claim 1 or 2, which performs mixed fuel operation in which the engine is operated at the mixed fuel ignition timing determined by the ignition timing determination control.

4. In the ignition timing determination control, the control device, The engine system according to claim 1 or 2, wherein the mixed fuel ignition timing is determined in such a manner that the higher the calorific value of the hydrogen in the mixed fuel, the more the mixed fuel ignition timing is retarded between the first fuel ignition timing and the hydrogen ignition timing.

5. The control device is The system is configured to perform carbon concentration determination control, which determines whether or not the carbon dioxide concentration in the combustion exhaust gas from the combustion chamber exceeds a predetermined decarbonization threshold. The engine system according to claim 1 or 2, wherein, in the carbon concentration determination control, if it is determined that the carbon dioxide concentration exceeds the decarbonization threshold, a hydrogen ratio increase correction control is performed to increase the calorific value ratio of hydrogen in the mixed fuel, and the ignition timing determination control is performed based on the calorific value ratio of hydrogen in the mixed fuel after the calorific value ratio of hydrogen has been increased by the hydrogen ratio increase correction control.

6. A cogeneration system comprising the engine system described in claim 1 or 2.

7. A control method for an engine system that burns a fuel containing at least one of a first fuel containing methane and hydrogen in a combustion chamber, A control method for an engine system, which performs ignition timing determination control to determine the mixed fuel ignition timing, which is the MBT ignition timing of a mixed fuel obtained by mixing the first fuel and the hydrogen, to be an ignition timing between the first fuel ignition timing and the hydrogen ignition timing, according to the first fuel ignition timing which is the MBT ignition timing when the fuel is only the first fuel, the hydrogen ignition timing which is the MBT ignition timing when the fuel is only the hydrogen, and the calorific value ratio of the hydrogen in the mixed fuel.

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