Engine System

Abstract

To provide an engine system capable of improving net thermal efficiency of an engine through increasing a concentration of combustion promoting gas in reformed gas in a configuration capable of generating the reformed gas through partial oxidation reaction of rich mixture in a reforming cylinder.SOLUTION: An engine system comprises a control device 50 which executes air excess rate control controlling an air excess rate in a reforming cylinder 40d within a predetermined range enabling reformed gas K to be generated in a state where air-fuel mixture is compressed and undergoes self-ignition combustion in the reforming cylinder 40d.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an engine system in which at least some of a plurality of cylinders are made to function as reforming cylinders that carry out a partial oxidation reaction of at least a portion of a mixture containing fuel and combustion air to reform it into a reformed gas containing a combustion-promoting gas that has a faster combustion speed than the fuel, and the remaining plurality of cylinders are made to function as normal cylinders to which the reformed gas reformed in the reforming cylinders is introduced. [Background technology]

[0002] Conventionally, there is known an engine system that has at least one normal cylinder having a combustion chamber that burns a mixture containing fuel and combustion air, and at least one reforming cylinder that reforms at least a portion of the mixture into a reformed gas containing a combustion-promoting gas that burns faster than the fuel by a partial oxidation reaction in the combustion chamber, and that directs the reformed gas reformed in the reforming cylinder to at least the normal cylinder (see Patent Document 1). In the reforming cylinder, for example, a rich mixture containing fuel whose main component is methane is subjected to a partial oxidation reaction to produce a reformed gas containing a combustion-promoting gas with a fast combustion rate, such as hydrogen. By introducing this reformed gas into the normal cylinder, for example, it is possible to increase the spark propagation speed in the combustion chamber of the normal cylinder, reduce misfires and combustion fluctuations, and improve thermal efficiency by burning the combustion-promoting gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-94930 Summary of the Invention [Problem to be solved by the invention]

[0004] As mentioned above, in the engine system disclosed in Patent Document 1, it is expected that the thermal efficiency will be improved by using combustion-promoting gas as fuel in the normal cylinders. However, for example, by controlling the combustion state in the reforming cylinders, it is possible to achieve further improvements in thermal efficiency, and the development of new technology has been desired.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide an engine system that can increase the concentration of combustion-promoting gas in the reformed gas and improve the net thermal efficiency of the engine in a configuration that can generate reformed gas by partially oxidizing an over-rich mixture in the reforming cylinder. [Means for solving the problem]

[0006] The engine system for achieving the above object comprises: An engine system in which at least some of a plurality of cylinders are made to function as reforming cylinders that reform at least a portion of a mixture containing fuel and combustion air into a reformed gas containing a combustion-promoting gas that burns faster than the fuel by a partial oxidation reaction, and the remaining cylinders are made to function as normal cylinders to which the reformed gas reformed in the reforming cylinders is introduced, and the engine system is characterized by the following configuration: In the reformed cylinder The excess air ratio is less than 1. a control device that executes an 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 while the air-fuel mixture is compressed and self-ignited and burned; 、 a first fuel supply unit that supplies fuel to be introduced to at least the normal cylinder, and a second fuel supply unit that supplies fuel to be introduced to the reforming cylinder; When the control device is executing the fuel ratio reduction control that reduces a fuel ratio, which is a ratio of the total fuel supply amount to all of the normal cylinders by the first fuel supply unit to the total fuel supply amount to all of the reforming cylinders by the second fuel supply unit, in a state where the control device is executing the air excess ratio control that adjusts the fuel supply amount by the second fuel supply unit to control the air excess ratio in the reforming cylinder within a predetermined range in which the reformed gas is generated, The excess air ratio control is executed while the self-ignition combustion is being performed in the reforming cylinder. It's at the point.

[0007] As a result of extensive research, the inventors of the present invention have discovered that when the excess air ratio of a reforming cylinder is controlled while the air-fuel mixture is spark ignited in that cylinder, as shown in Figures 3(a1) and (a2), as the excess air ratio of the reforming cylinder is reduced from 1 to a predetermined peak excess air ratio (the air excess ratio corresponding to α in Figure 3), the concentrations of hydrogen and carbon monoxide, which are combustion-promoting gases, in the reformed gas gradually increase, and when the excess air ratio is reduced beyond the predetermined peak excess air ratio, the concentrations of hydrogen and nitrogen monoxide, which are combustion-promoting gases, in the reformed gas gradually decrease. Furthermore, as shown in Figure 4, it was also found that the net thermal efficiency including the reformed cylinder when the air-fuel mixture is spark ignited in the normal cylinder and the reformed cylinder gradually increases as the excess air ratio of the reformed cylinder is reduced from 1 to near a predetermined peak excess air ratio, and gradually decreases when the excess air ratio is reduced beyond near the predetermined peak excess air ratio. In other words, from the results shown in Figures 3(a1)(a2) and 4, it is estimated that when the excess air ratio in the reformed cylinder is changed, the net thermal efficiency of the engine including the reformed cylinder has a positive correlation with the concentration of the combustion-promoting gas generated in the reformed cylinder.

[0008] Here, as shown in Figures 3(a1) and (a2), when the concentration of the combustion-promoting gas in the reformed gas is controlled by controlling the excess air ratio of the reformed cylinder while the mixture in the reformed cylinder is spark ignited, the concentration of the combustion-promoting gas increases as the excess air ratio is reduced to a predetermined peak excess air ratio, but if the excess air ratio is reduced beyond the predetermined peak excess ratio, the concentration decreases for reasons such as it becoming difficult to spark ignite the rich mixture in the reformed cylinder.

[0009] In this situation, the inventors of the present invention conducted experiments and simulations to control the excess air ratio in the reformed cylinder within a predetermined range in which reformed gas is produced, while the air-fuel mixture is compressed and self-ignited in the reformed cylinder. In these experiments and simulations, the stroke-bore ratio (stroke / bore), displacement, and engine speed of the normal and reformed cylinders were adjusted to values ​​generally used in normal engines. The simulation was performed using GT-Power (Gamma Technologies).

[0010] As shown in the experimental results in Figures 3(b1) and (b2) and the simulation results in Figures 3(c1) and (c2), it was confirmed that when the air-fuel mixture is burned by spark ignition in the reformed cylinder, when the air-fuel mixture is burned by auto-ignition in the reformed cylinder, combustion-promoting gas can be generated at an air excess ratio lower than the specified peak air excess ratio (air excess ratio corresponding to α in Figure 3) when the air-fuel mixture is burned by spark ignition. It was also confirmed that even at air excess ratios lower than the specified peak air excess ratio, there is a range of air excess ratios over which the concentration of the combustion-promoting gas tends to increase as the air excess ratio is reduced. Furthermore, in both the experimental and simulation results, the peak value of the concentration of hydrogen as a combustion-promoting gas when the mixture is burned by self-ignition in the reformed cylinder (β1, β2 in Figure 3) is more than twice the peak value of the concentration of hydrogen as a combustion-promoting gas when the mixture is burned by spark ignition in the reformed cylinder (α in Figure 3).This suggests that by directing the reformed gas containing this combustion-promoting gas into the normal cylinder, it may be possible to further improve the net thermal efficiency of the normal cylinder.

[0011] Incidentally, although experimental results will be omitted, the inventors have confirmed that when the mixture is burned by spark ignition in the reformed cylinder, combustion-promoting gas can be generated well even if the excess air ratio in the reformed cylinder is relatively high (for example, in the range of 0.5≦λ<1).

[0012] Here, for example, an engine system that performs auto-ignition combustion of an air-fuel mixture in a combustion chamber, as shown in prior art documents (JP Patent Publication No. 2002-21608), improves the specific heat ratio and net thermal efficiency by operating in a lean region where the excess air ratio is sufficiently greater than 1 (in terms of equivalence ratio, 0.2≦φ≦0.4), and also improves net thermal efficiency by setting the actual compression ratio to a large value (17 or more and 19 or less). In contrast, the present invention aims to improve the net thermal efficiency of the normal cylinders by increasing the concentration of combustion-promoting gas in the reformed gas through auto-ignition combustion in the reformed cylinder in an excess-air ratio region where the excess air ratio is sufficiently smaller than 1, and is therefore based on a technical concept that is completely different from conventional engine systems that use auto-ignition combustion. In other words, the inventors of the present invention came up with the technical idea of ​​increasing the concentration of combustion-promoting gas in the reformed gas by implementing control such as increasing the compression ratio in the reformed cylinder, which serves as a combustion chamber in a fuel-rich state, something that has not been fully considered in engine systems that perform self-ignition combustion in the prior art. Based on this technical concept, an engine system was completed that performs excess air ratio control, controlling the excess air ratio in the reforming cylinder within a predetermined range in which reformed gas is produced, while the mixture is compressed and self-ignited in the reforming cylinder. Furthermore, the inventors of the present invention have discovered that the net thermal efficiency of the engine can be improved by lowering the fuel ratio, which is the ratio of the total fuel supply to all normal cylinders to the total fuel supply to the reformed cylinders, i.e., by increasing the amount of fuel derived from the reformed gas used in the normal cylinders. Therefore, according to the above characteristic configuration, in addition to improving net thermal efficiency based on fuel ratio reduction control, it is also possible to expect the effect of improving net thermal efficiency of the normal cylinders by controlling the excess air ratio while self-ignition combustion is occurring in the reformed cylinder, so that a further improvement in the net thermal efficiency of the engine can be expected.

[0013] As described above, in a configuration capable of generating reformed gas by partially oxidizing an over-rich mixture in the reforming cylinder, an engine system can be realized that can increase the concentration of combustion-promoting gas in the reformed gas and improve the net thermal efficiency of the engine.

[0016] A further characteristic configuration of the engine system is that the control device The feature is that the mixture is caused to self-ignite and burn in the reformed cylinder by activating at least one of an actual compression ratio setting means that adjusts the pressure in the reformed cylinder before the self-ignition to set the actual compression ratio of the reformed cylinder, and a fresh air temperature adjustment means that adjusts the temperature of the fresh air supplied to the reformed cylinder.

[0017] The inventors of the present invention have newly discovered that by activating at least one of an actual compression ratio setting means for adjusting the pressure in the reformed cylinder before self-ignition to set the actual compression ratio of the reformed cylinder, and a fresh air temperature adjustment means for adjusting the temperature of the fresh air supplied to the reformed cylinder, it is possible to cause the mixture to self-ignite and burn in the reformed cylinder in an over-rich region where the excess air ratio is less than 1, thereby improving the concentration of combustion-promoting gas in the reformed gas. The above-described characteristic configuration makes it possible to extend the lower limit of the excess air ratio in the reforming cylinder, increase the concentration of combustion-promoting gas in the reformed gas, and improve the net thermal efficiency of the engine.

[0018] Further characteristic configurations of the engine system include: a combustion promoting gas concentration measuring unit that measures the concentration of the combustion promoting gas in the reformed gas from the reforming cylinder; The control device executes the excess air ratio control in the reforming cylinder so as to maximize the concentration of the combustion promoting gas measured by the combustion promoting gas concentration measuring section.

[0019] As described in the above characteristic configuration, the control device controls the excess air ratio in the reformed cylinder during excess air ratio control so as to maximize the concentration of the combustion-promoting gas measured by the combustion-promoting gas measuring unit. This makes it possible to generate reformed gas with a higher concentration of combustion-promoting gas than the concentration of combustion-promoting gas in the reformed gas when the mixture is spark-ignited in the reformed cylinder (α in Figure 3), i.e., the concentration of combustion-promoting gas when the mixture is self-ignited and burned in the reformed cylinder (β1 or β2 in Figure 3), and the net thermal efficiency of the normal cylinder, which has a positive correlation with the concentration of the combustion-promoting gas, can be operated at its highest point.

[0022] Further characteristic configurations of the engine system include: The control device is characterized in that, when the air excess ratio control is being performed while the self-ignition combustion is occurring in the reformed cylinder, it performs reformed gas operation in which only the reformed gas is introduced as the fuel to the normal cylinder.

[0023] As described above, the net thermal efficiency of the normal cylinders can be improved by increasing the proportion of reformed gas (combustion-promoting gas) as fuel for the normal cylinders. Therefore, by performing reformed gas operation in which only reformed gas is introduced as fuel to the normal cylinders, as in the above characteristic configuration, the net thermal efficiency can be improved. In addition, by performing excess air ratio control while self-ignition combustion is occurring in the reformed cylinders, the net thermal efficiency of the normal cylinders can also be improved, so a further improvement in the net thermal efficiency of the engine can be expected.

[0024] Further characteristic configurations of the engine system include: The engine is characterized by comprising a reformed engine having at least one reformed cylinder as the plurality of cylinders, and an external power engine having the normal cylinders as the plurality of cylinders.

[0025] The engine system of the present invention, as in the above-described characteristic configuration, can effectively exhibit the effects described so far even when it is configured to have a separate reformed engine with a reformed cylinder and an external output engine with a normal cylinder to which reformed gas is guided from the reformed cylinder. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic configuration diagram of an engine system according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram of a reformed cylinder of the engine system according to the embodiment. [Figure 3] This is a graph showing the concentrations of hydrogen and carbon monoxide in the reformed gas for each excess air ratio in the reforming cylinder, where (a1) and (a2) show the experimental results for spark ignition, (b1) and (b2) show the experimental results for auto-ignition, and (c1) and (c2) show the simulation results for auto-ignition. [Figure 4] FIG. 10 is a graph showing the net thermal efficiency of the entire engine for each excess air ratio in the reformed cylinder. DETAILED DESCRIPTION OF THE INVENTION

[0027] The engine system 100 according to an embodiment of the present invention is configured to generate reformed gas by partially oxidizing an over-rich mixture in a reforming cylinder, and is capable of increasing the concentration of combustion-promoting gas in the reformed gas, thereby improving the net thermal efficiency of the engine. The engine system 100 will be described below with reference to the drawings.

[0028] As shown in FIG. 1, the engine system 100 according to the embodiment includes an engine body 40 having normal cylinders 40a, 40b, and 40c that combust a mixture M containing fuel F, such as city gas 13A (an example of a hydrocarbon gas containing methane as a main component), and combustion air A, and a reforming cylinder 40d that reforms at least a portion of the mixture M into a reformed gas K containing a combustion-promoting gas that has a faster combustion speed than the fuel F, through a partial oxidation reaction. The engine system 100 is provided with a first fuel supply unit that supplies fuel to the normal cylinders 40a, 40b, and 40c, and a second fuel supply unit that supplies fuel to the reforming cylinder 40d, and the reformed gas K reformed in the reforming cylinder 40d is supplied to at least the normal cylinders 40a, 40b, and 40c (in this embodiment, it is supplied only to the normal cylinders 40a, 40b, and 40c). In the reforming cylinder 40d, steam reforming shown in the following formula 1 and the water gas shift reaction shown in the following formula 2 also proceed.

[0029] CH4+H20→CO+3H2... [Formula 1]

[0030] CO+H20→CO2+H2... [Formula 2]

[0031] 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 (three in this embodiment) normal cylinders 40a, 40b, 40c and at least one (one in this embodiment) reformed cylinder 40d. Furthermore, the engine system 100 includes an engine control unit (hereinafter referred to as a control device 50) that receives measurement results from sensors that detect the operating state of the engine and is composed of a group of hardware and software that controls the operation of the turbocharged engine based on the input signals.

[0032] Although detailed illustrations are omitted for this type of engine system 100, fresh air is supplied from the main air intake pipe 20 via an intake valve (not shown) to the combustion chambers (not shown) of the normal cylinders 40a, 40b, and 40c, and is compressed as the pistons rise, and is then ignited by a spark from a spark plug (not shown), causing the air to combust and expand, pushing the pistons down and outputting rotational power from the rotating shaft (not shown). Exhaust gas E generated by the combustion is pushed out of the combustion chambers of the normal cylinders 40a, 40b, and 40c via an exhaust valve (not shown) into the exhaust passage 27 and discharged to the outside. As will be described in detail later, the combustion air A supplied from the main air intake pipe 20 is also supplied to the reforming cylinder 40d through the reforming cylinder intake branch pipe 20d, and the piston in the reforming cylinder 40d is also pushed down, outputting rotational power from the rotary shaft. However, the reformed gas K generated as exhaust gas in the reforming cylinder 40d is not discharged to the outside, but is returned to the main air intake pipe 20 via the reformed gas passage 28 and is guided to the normal cylinders 40a, 40b, and 40c.

[0033] The main air intake pipe 20 is provided with, in the order listed from the upstream side, an air cleaner 21 that purifies the combustion air A, a Venturi-type mixer 14 that mixes the combustion air A with fuel F at an appropriate ratio (air-fuel ratio), and a throttle valve 23 for normal cylinders that can adjust the amount of air-fuel mixture M supplied to the normal cylinders 40a, 40b, and 40c by adjusting the opening. That is, in the main air intake pipe 20, the mixture M produced by mixing fuel F and combustion air A in the mixer 14 is adjusted to a predetermined flow rate via the normal cylinder throttle valve 23 and introduced into the combustion chambers of the normal cylinders 40a, 40b, and 40c.

[0034] The reforming cylinder intake branch pipe 20d, which branches off from the main intake pipe 20 upstream of the mixer 14, is provided with the following in the order listed from the upstream side: a compressor 31 as a supercharger 30 that compresses the combustion air A; an intercooler 22 that cools the combustion air A that has been heated by the pressure increase by the compressor 31; a reforming cylinder throttle valve 25 that can adjust the amount of mixture M supplied to the reforming cylinder 40d by adjusting its opening; and a Venturi-type mixer 16 that mixes the combustion air A with fuel F at an appropriate ratio (air-fuel ratio).

[0035] The first fuel supply passage 11, which introduces the fuel F to the mixer 14, is provided with a differential pressure regulator 12 that maintains a constant pressure difference between the pressure of the combustion air A in the main air intake pipe 20 upstream of the mixer 14 and the pressure of the fuel F in the first fuel supply passage 11, and a first fuel flow control valve 13 that adjusts the amount of fuel F supplied to the combustion chambers of the normal cylinders 40a, 40b, and 40c via the mixer 14. That is, the first fuel supply passage 11, the differential pressure regulator 12, the mixer 14, and the first fuel flow control valve 13 function as a first fuel supply unit.

[0036] The supercharger 30 is configured as a turbo-type supercharger 30 that supplies exhaust gas E discharged from the normal cylinders 40a, 40b, 40c to a turbine 32 provided in the exhaust passage 27 connected to the normal cylinders 40a, 40b, 40c, and compresses the air-fuel mixture M supplied to the combustion chamber of the reforming cylinder 40d by a compressor 31 provided in the reforming cylinder air intake duct 20d while connected to the turbine 32. That is, the supercharger 30 rotates the turbine 32 by the kinetic energy of the exhaust gas E flowing through the exhaust passage 27, compresses combustion air A flowing through the reforming cylinder air intake duct 20d by the rotational force of the turbine 32, and supplies the compressed combustion air A to the combustion chamber of the reforming cylinder 40d, i.e., performs so-called supercharging. That is, in this embodiment, the supercharger 30 supercharges only the combustion air A that is guided to the reforming cylinder 40d.

[0037] Downstream of the air cleaner 21, the main air intake pipe 20 branches into a plurality of normal cylinder air intake branch pipes 20a, 20b, and 20c that lead combustion air A1 to the normal cylinders 40a, 40b, and 40c, respectively, and a reforming cylinder air intake branch pipe 20d that leads combustion air A to the reforming cylinder 40d. The reforming cylinder 40d is configured to partially oxidize a portion of the fresh air in its combustion chamber to generate a reformed gas K containing a combustion-promoting gas such as hydrogen, which has a faster combustion speed than the fuel F (e.g., methane). It is known that when methane and air are mixed and burned, the amount of hydrogen generated peaks in a fuel-rich region where the excess air ratio is less than 1. Therefore, in this embodiment, in order to burn the mixture in a fuel-rich state in the fuel chamber of the reforming cylinder 40d, a second fuel supply passage 29 that supplies fuel F via a Venturi-type mixer 16 is connected to the reforming cylinder intake branch pipe 20d that supplies fresh air to the reforming cylinder 40d, and the second fuel supply passage 29 is provided with a second fuel flow control valve 15 that controls the flow rate of the fuel F. A compressor (not shown) or the like is provided on the upstream side of the second fuel flow control valve 15 of the second fuel supply passage 29 in order to increase the supply pressure of the fuel F to the supercharging pressure at the outlet of the compressor 31 of the main intake pipe 20. Furthermore, a reformed gas passage 28, which carries the reformed gas K reformed in the reforming cylinder 40d, is connected to the reforming cylinder 40d, and the downstream end of the reformed gas passage 28 is connected to the downstream side of the throttle valve 23 for the normal cylinders of the main intake pipe 20. That is, in this embodiment, the reformed gas K is configured so that all of it is guided to the normal cylinders 40a, 40b, 40c. The control device 50 executes excess air ratio fluctuation control, which controls the opening of the second fuel flow control valve 15 so that the excess air ratio of the fresh air to the reforming cylinder 40d becomes smaller than 1. In other words, the second fuel supply passage 29, the mixer 16, and the second fuel flow control valve 15 function as a second fuel supply unit.

[0038] A rotation speed sensor that measures the rotation speed of the rotation shaft (not shown) is provided as an operating state detection unit 41 on the rotation shaft (not shown) of the engine body 40. Furthermore, a torque measurement sensor that measures the torque of the rotating shaft (not shown) of the engine body 40 is provided as an operating state detection unit 41 on the rotating shaft of the engine body 40, and the control device 50 controls the openings of the first fuel flow control valve 13, the second fuel flow control valve 15, the throttle valve 23 for the normal cylinder, and the throttle valve 25 for the reformed cylinder so that the engine output calculated based on the engine speed measured by the speed sensor and the torque measured by the torque measurement sensor becomes a target output.

[0039] Now, as shown in Figures 3(a1) and (a2), when the air excess ratio of the reformed cylinder 40d is controlled while the mixture M in the reformed cylinder 40d is being spark ignited, the concentration of the combustion-promoting gas in the reformed gas K increases as the air excess ratio is reduced up to a predetermined peak air excess ratio (the air excess ratio corresponding to α in Figure 3), but if the air excess ratio is reduced beyond the predetermined peak air excess ratio, the concentration of the combustion-promoting gas in the reformed gas K decreases for reasons such as the difficulty of spark igniting the rich mixture in the reformed cylinder 40d.

[0040] Therefore, the inventors conducted experiments and simulations to control the excess air ratio in the reforming cylinder 40d within a predetermined range in which the reformed gas K is produced while the mixture M is compressed and self-ignited in the reforming cylinder 40d. In the experiments and simulations, the stroke-bore ratio (stroke / bore), displacement, and engine speed of the normal cylinder and the modified cylinder were adjusted to values ​​generally used in a normal engine. The simulation was performed using GT-Power (Gamma Technologies).

[0041] As shown in the experimental results in Figures 3(b1) and (b2) and the simulation results in Figures 3(c1) and (c2), it was confirmed that when the air-fuel mixture M is self-ignited and burned in the reforming cylinder 40d, the combustion-promoting gas can be generated at an excess air ratio lower than the above-mentioned predetermined peak excess air ratio (the excess air ratio corresponding to α in Figure 3), compared to when the air-fuel mixture M is spark-ignited in the reforming cylinder 40d (Figures 3(a1) and (a2)). It was also confirmed that even at excess air ratios lower than the predetermined peak excess air ratio, there is a range of excess air ratios within which the concentration of the combustion-promoting gas tends to increase as the excess air ratio decreases. Furthermore, in both the experimental and simulation results, the peak value of the concentration of hydrogen as a combustion-promoting gas when the mixture M is burned by self-ignition in the reformed cylinder 40d (β1, β2 in Figure 3) is more than twice the peak value of the concentration of hydrogen as a combustion-promoting gas when the mixture M is burned by spark ignition in the reformed cylinder 40d (α in Figure 3). Therefore, by directing the reformed gas K containing this combustion-promoting gas to the normal cylinders, it may be possible to further improve the net thermal efficiency of the normal cylinders 40a, 40b, and 40c. Incidentally, in the experimental results shown in FIG. 3, β1 / α=approximately 2.2 and β2 / α=approximately 2.8.

[0042] Although there is a difference between the peak value of the concentration of hydrogen as a combustion-promoting gas (β1 in Figure 3) and the excess air ratio at that peak value in the experimental results when the mixture M is self-ignited and the peak value of the concentration of hydrogen as a combustion-promoting gas (β2 in Figure 3) and the excess air ratio at that peak value in the simulation results, the above-mentioned tendency is common to both.

[0043] Therefore, in the engine system 100 according to this embodiment, the control device 50 performs excess air ratio control to control the excess air ratio in the reforming cylinder 40d within a predetermined range in which the reformed gas K is generated while the mixture M is compressed and self-ignited in the reforming cylinder 40d. 。

[0044] As shown in Figure 2, in order to perform self-ignition combustion of the mixture in the reforming cylinder 40d, the reforming cylinder 40d is provided with an opening / closing timing setting mechanism 61 that sets the opening / closing timing of an intake valve 63 that opens and closes the intake port 20f to which the reforming cylinder intake branch pipe 20d is connected, and an exhaust valve 64 that opens and closes the exhaust port 28b to which the reforming gas flow path 28 is connected. When auto-igniting combustion of the air-fuel mixture M in the reforming cylinder 40d, the control device 50 adjusts the pressure in the combustion chamber N of the reforming cylinder 40d before auto-ignition by, for example, changing and adjusting the closing timing of the intake valve 63 during the compression stroke using the opening / closing timing setting mechanism 61, or by adjusting the boost pressure of the fresh air using the above-mentioned supercharger 30, thereby setting the actual compression ratio in the combustion chamber N to the actual compression ratio for auto-ignition combustion. The control device 59, opening / closing timing setting mechanism 61, intake valve 63, supercharger 30, etc. function as actual compression ratio setting means.

[0045] As shown in Fig. 4, the net thermal efficiency of the engine body 40 including the reforming cylinder 40d, which is the result when the air-fuel mixture M is spark ignited in the reforming cylinder 40d, gradually increases as the excess air ratio of the reforming cylinder 40d decreases from 1 to near the peak excess air ratio, and gradually decreases when the excess air ratio is decreased beyond near the peak excess air ratio. Incidentally, in Fig. 4, η1 / η2 = approximately 1.12. That is, from the results shown in Figure 4, it is estimated that when the excess air ratio is changed in the reformed cylinder 40d, the net thermal efficiency of the engine body 40 including the reformed cylinder 40d has a positive correlation with the concentration of the combustion-promoting gas generated in the reformed cylinder 40d.

[0046] Furthermore, as shown in the experimental results and simulation results of Figures 3(b1)(b2)(c1)(c2) above, when excess air ratio control is performed to control the excess air ratio in the reforming cylinder 40d while the mixture M is undergoing auto-ignition combustion in the reforming cylinder 40d, as the excess air ratio of the reforming cylinder 40d is reduced from 1, the concentrations of hydrogen and nitric oxide as combustion-promoting gases in the reforming gas K gradually increase until the hydrogen concentration exceeds its peak value (β1, β2 in Figure 3), and when the hydrogen concentration is reduced beyond its peak value (β1, β2 in Figure 3), the concentrations of hydrogen and nitric oxide as combustion-promoting gases in the reforming gas K gradually decrease.

[0047] Therefore, the engine system 100 according to this embodiment has the following configuration in order to maintain the overall net thermal efficiency including the reformed cylinder 40d and the normal cylinders 40a, 40b, and 40c at near the highest point. That is, the engine system 100 is provided with a hydrogen sensor S (an example of a combustion-promoting gas concentration measuring unit) at the outlet of the reforming cylinder 40d in the reforming gas flow path 28, which measures the concentration of hydrogen, which is a combustion-promoting gas in the reforming gas K generated in the reforming cylinder 40d, and the control device 50 controls the air excess ratio in the reforming cylinder 40d based on the hydrogen concentration measured by the hydrogen sensor S in the air excess ratio control. In other words, the control device 50 controls the excess air ratio in the reforming cylinder 40d so as to maximize the concentration of hydrogen measured by the hydrogen sensor S, thereby maintaining the net thermal efficiency of the engine body 40 at the highest point by controlling the excess air ratio in the reforming cylinder 40d.

[0048] Furthermore, the inventors of the present application have discovered that when excess air ratio control is being performed, in fuel ratio reduction control, which reduces the fuel ratio, which is the ratio of the total fuel supply amount to all normal cylinders 40a, 40b, 40c to the total fuel supply amount to all reformed cylinders 40d, the net thermal efficiency of the engine body 40 improves as the fuel ratio is reduced. Therefore, when the control device 50 is performing fuel ratio reduction control in the reforming cylinder 40d by adjusting the amount of fuel supplied by the second fuel supply unit to reduce the fuel ratio, which is the ratio of the total amount of fuel supplied to all normal cylinders 40a, 40b, 40c by the first fuel supply unit to the total amount of fuel supplied to all reforming cylinders 40d by the second fuel supply unit, the control device 50 controls the air excess ratio of the reforming cylinder 40d while the mixture M is being self-ignited and burned in the reforming cylinder 40d. This control not only improves the net thermal efficiency based on the fuel ratio reduction control, but also improves the net thermal efficiency of the normal cylinders by controlling the excess air ratio while the mixture is self-igniting and burning in the reformed cylinder 40d, so that a further improvement in the net thermal efficiency of the engine body 40 can be expected.

[0049] [Another embodiment] (1) In the above embodiment, the normal cylinders 40a, 40b, and 40c are configured to spark ignite the air-fuel mixture using spark plugs (not shown), and the reforming cylinder 40d is configured to self-ignite and burn the air-fuel mixture. However, the normal cylinders 40a, 40b, and 40c may be configured to self-ignite the air-fuel mixture, and the reforming cylinder 40d may be equipped with a spark plug (not shown) and may spark-ignite the air-fuel mixture when the combustion fluctuation rate is relatively high, such as during engine start-up or warm-up.

[0050] (2) As a configuration for promoting the self-ignition combustion of the mixture M in the reforming cylinder 40d, a configuration may be adopted in which a fresh air temperature adjustment means is provided for adjusting the temperature of the fresh air supplied to the reforming cylinder 40d, and the temperature of the fresh air is increased by the fresh air temperature adjustment means. The fresh air temperature adjustment means can be composed of, for example, a heat exchanger (not shown) that exchanges heat between the exhaust gas E flowing through the exhaust passage 27 and the fresh air flowing through the reforming cylinder intake bronchial pipe 20d, a flow control valve (not shown) that adjusts the flow rate of the exhaust gas E introduced to the heat exchanger, and a control device 50 that controls the opening of the flow control valve, and can be configured to raise the fresh air temperature so that the combustion coefficient of variation (COV) of the reforming cylinder 40d derived from the in-cylinder pressure measured by an in-cylinder pressure sensor (not shown) is below a certain value.

[0051] (3) In the above embodiment, an example of a configuration is shown in which the combustion-promoting gas concentration measuring unit is provided with a hydrogen sensor S that measures the concentration of hydrogen as a combustion-promoting gas in the reformed gas K. However, a configuration may also be adopted in which a carbon monoxide sensor is provided that measures the concentration of carbon monoxide as a combustion-promoting gas. Furthermore, a configuration including both a hydrogen sensor and a carbon monoxide sensor may be employed.

[0052] (4) In the above embodiment, the number of normal cylinders may be any number as long as it is one or more, and the number of reformed cylinders may be any number as long as it is one or more, and the functions of the present invention can be satisfactorily exhibited.

[0053] (5) In the above embodiment, a configuration example was shown in which one engine 40 is provided with the reforming cylinder 40d and the normal cylinders 40a, 40b, 40c to which the reformed gas K generated in the reforming cylinder 40d is introduced. Alternatively, although not shown in the figures, it is possible to adopt a configuration that includes a reformed engine having at least one reformed cylinder and an external output engine having a normal cylinder to which the reformed gas generated in the reformed cylinder of the reformed engine is introduced. Even in this configuration, the various controls performed by the control device 50 described in the above embodiment can be executed, and the effects thereof can be satisfactorily exhibited.

[0054] (6) In the fuel ratio reduction control, the control device 50 can also perform reformed gas operation in which, while the mixture M is being self-ignited and burned in the reformed cylinder 40d, the fuel ratio is set to zero and only reformed gas K is introduced as fuel to the normal cylinders 40a, 40b, and 40c. In this case, the first fuel supply passage 11, the differential pressure regulator 12, the first fuel flow control valve 13, and the mixer 14, which serve as the first fuel supply unit, can be omitted.

[0055] (7) The reformed gas flow passage 28 may be configured to be connected to the exhaust port 28a of the reformed cylinder 40d and at least one of the normal cylinder air intake pipes 20a, 20b, and 20c that supply fresh air to the normal cylinders 40a, 40b, and 40c.

[0056] (8) In the above embodiment, an example was shown in which the engine system 100 includes the supercharger 30. However, even if the engine system 100 does not include the supercharger 30, the object of the present invention can be satisfactorily achieved. As described above, in a configuration that does not include the supercharger 30, the pressure in the reforming cylinder intake pipe 20d is not boosted to the supercharging pressure, so there is no need to boost the pressure of the fuel F supplied to the mixer 16 as a second fuel supply unit, and a simple and compact configuration can be achieved that does not include a compressor or the like for boosting the pressure.Incidentally, in this case, the pressure of the fuel F supplied from the mixer 16 to the reforming cylinder intake pipe 20d is set to the normal intake pressure. Furthermore, in the above embodiment, an example in which a turbo type is provided as the supercharger 30 has been shown, but a supercharger type may also be used. Furthermore, in the above embodiment, an example of so-called single-stage supercharging, in which the supercharger 30 includes a single compressor 31 and a single turbine 32, has been shown, but it may alternatively be a multi-stage supercharger having two or more stages.

[0057] (9) In the above embodiment, the fuel F is city gas 13A. However, in the essential meaning of the present invention, the fuel F is not limited to gas fuel, and may be liquid fuel such as gasoline.

[0058] (10) In the above embodiment, the fuel F is supplied by a venturi system, but it may be injected into the reforming cylinder intake pipe 20d or directly into the reforming cylinder 40d. In this case, the excess air ratio can be controlled by adjusting the injection amount of the fuel F.

[0059] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradictions arise. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0060] The engine system of the present invention can be effectively used in a configuration in which a reformed gas can be generated by partially oxidizing an over-rich mixture in a reforming cylinder, thereby increasing the concentration of combustion-promoting gas in the reformed gas and improving the net thermal efficiency of the engine. [Explanation of symbols]

[0061] 40: Engine body 40a: Normal cylinder 40b: Normal cylinder 40c: Standard cylinder 40d: Modified cylinder 50: Control device 61: Opening and closing timing setting mechanism 63:Air supply valve 64: Exhaust valve 100: Engine system S: Hydrogen sensor A: Combustion air F:Fuel K: Reformed gas M: Air-fuel mixture

Claims

1. In an engine system in which at least some of a plurality of cylinders are made to function as reforming cylinders that reform at least a portion of an air-fuel mixture containing fuel and combustion air into a reformed gas containing a combustion-promoting gas that burns faster than the fuel by a partial oxidation reaction, and the remaining cylinders are made to function as normal cylinders to which the reformed gas reformed in the reforming cylinders is introduced, a control device that executes an excess air ratio control for controlling the excess air ratio in the reforming cylinder within a predetermined range in which the reformed gas is produced, while the air-fuel mixture is compressed and self-ignited in the reforming cylinder with the excess air ratio in an excess air ratio region less than 1; a first fuel supply unit that supplies fuel to be introduced to at least the normal cylinder, and a second fuel supply unit that supplies fuel to be introduced to the reforming cylinder, When the control device is executing the air excess ratio control that adjusts the fuel supply amount by the second fuel supply unit to control the air excess ratio in the reforming cylinder within a predetermined range in which the reformed gas is generated, and is executing a fuel ratio reduction control that reduces a fuel ratio that is a ratio of the total fuel supply amount to all of the normal cylinders by the first fuel supply unit to the total fuel supply amount to all of the reforming cylinders by the second fuel supply unit, An engine system that executes the excess air ratio control while the self-ignition combustion is occurring in the reformed cylinder.

2. The control device 2. An engine system as described in claim 1, wherein the mixture is caused to self-ignite and burn in the reformed cylinder by activating at least one of an actual compression ratio setting means that adjusts the pressure in the reformed cylinder before the self-ignition to set the actual compression ratio of the reformed cylinder, and a fresh air temperature adjustment means that adjusts the temperature of the fresh air supplied to the reformed cylinder.

3. a combustion promoting gas concentration measuring unit that measures the concentration of the combustion promoting gas in the reformed gas from the reforming cylinder; 3. The engine system according to claim 1, wherein the control device executes the excess air ratio control in the reforming cylinder so as to maximize the concentration of the combustion promoting gas measured by the combustion promoting gas concentration measuring unit.

4. An engine system described in any one of claims 1 to 3, wherein the control device performs reformed gas operation in which only the reformed gas is introduced as the fuel to the normal cylinder when the air excess ratio control is being performed while the self-ignition combustion is occurring in the reformed cylinder.

5. An engine system described in any one of claims 1 to 4, comprising a modified engine having at least one modified cylinder as one of the plurality of cylinders, and an external output engine having normal cylinders as one of the plurality of cylinders.

Images