Internal combustion engine for power generation

Abstract

To provide an internal combustion engine for power generation capable of suppressing operation failure and operating with efficient fuel use.SOLUTION: An internal combustion engine 1 for power generation comprises: an engine body 2 in which a combustion chamber 26 for burning fuel is formed; an air supply pipe P that supplies biomass gas BG to the combustion chamber 26; an air supply valve 35 that opens and closes a communication part between the combustion chamber 26 and the air supply pipe P; a first injection part 46 provided to inject liquid volatile fuel FL toward the air supply valve 35 to clean the air supply valve 35 inside the air supply pipe P; and a control device 6 that appropriately selects any one of the biomass gas BG, the liquid volatile fuel FL, and a mixture MG of the biomass gas BG and the liquid volatile fuel FL as fuel supplied to the combustion chamber 26.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an internal combustion engine for power generation.

Background Art

[0002] An internal combustion engine using biomass gas as fuel may be used for power generation. Biomass gas is generated, for example, by burning wood. Wood contains a tar component. Contaminants such as the tar component exhibit viscosity when the internal combustion engine is cooled and liquefied. When such contaminants with viscosity, such as the tar component, adhere to the intake pipe or intake valve of the internal combustion engine, malfunction such as the intake valve sticking to the intake pipe may occur.

[0003] In addition, the biomass gas supplied to the internal combustion engine as described above may be generated by a facility for generating biomass gas. In such a facility, a certain period of time is required from the start of biomass gas generation until the biomass gas is stably supplied. During this period, since the amount of biomass gas generated varies, the operation of the internal combustion engine is not stable, and it may be difficult to perform stable power generation.

[0004] On the other hand, Patent Document 1 discloses a dual fuel injector nozzle that switches between biomass gas and fossil fuel and injects them separately. By using the nozzle disclosed in such Patent Document 1, it is conceivable to inject fossil fuel from the nozzle instead of biomass gas until the biomass gas is stably supplied. However, in that case, the biomass gas generated while injecting fossil fuel from the nozzle becomes unused, so the fuel use efficiency is poor. There is a need for an internal combustion engine for power generation that can suppress malfunctions and operate efficiently using fuel.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The problem that this invention aims to solve is to provide an internal combustion engine for power generation that can suppress malfunctions and operate efficiently using fuel. [Means for solving the problem]

[0007] An internal combustion engine that solves the above problems is an internal combustion engine for power generation, comprising: an engine body having a combustion chamber formed inside for burning fuel; an air intake pipe for supplying biomass gas to the combustion chamber; an air intake valve for opening and closing a communication section between the combustion chamber and the air intake pipe; an air intake pipe for introducing air into the air intake pipe; a raw gas intake pipe for introducing raw gas supplied from the outside into the air intake pipe; a raw gas pressure sensor provided in the raw gas intake pipe for measuring the pressure of the raw gas; a first injection unit provided inside the air intake pipe for injecting liquid volatile fuel toward the air intake valve to clean the air intake valve; and a control device for appropriately selecting one of the following as the fuel supplied to the combustion chamber: the biomass gas, the liquid volatile fuel, or a mixture of the biomass gas and the liquid volatile fuel. The biomass gas is a mixture of air and raw gas. During normal operation, the control device selects the biomass gas as the fuel and cleans the air intake valve by selecting the mixture as the fuel for a certain period of time. When starting the engine, the control device selects the liquid volatile fuel as the fuel and performs a warm-up operation. After that, it selects the mixture as the fuel and performs a startup adjustment operation to adjust the amount of liquid volatile fuel injected in the first injection unit according to the supply status of the biomass gas before transitioning to normal operation. During the startup adjustment operation, the control device increases the injection amount when the measured value of the raw gas pressure sensor decreases and decreases the injection amount when the measured value increases. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an internal combustion engine for power generation that can suppress malfunctions and operate efficiently using fuel. [Brief explanation of the drawing]

[0009] [Figure 1] This figure schematically shows the configuration of an internal combustion engine for power generation in an embodiment of the present invention. [Figure 2] This figure shows an example of a method for controlling the operation of an internal combustion engine used for power generation using a control device. [Figure 3] This figure schematically shows the configuration of an internal combustion engine for power generation in a modified example of the above embodiment. [Modes for carrying out the invention]

[0010] Hereinafter, with reference to the attached drawings, an embodiment for implementing the internal combustion engine for power generation according to the present invention will be described based on the drawings. Figure 1 is a schematic diagram showing the configuration of an internal combustion engine for power generation in an embodiment of the present invention. In this embodiment, the internal combustion engine 1 for power generation operates using biomass gas as fuel during normal operation. The internal combustion engine 1 for power generation drives a generator (not shown). The internal combustion engine 1 for power generation mainly comprises an engine body 2, an air intake unit 4, and a control device 6.

[0011] The engine body 2 comprises a cylinder block 20, a crankcase (not shown), and a cylinder head 30. The cylinder block 20 includes a cylinder 22. The cylinder 22 is formed in a cylindrical shape extending in the direction of its central axis. In Figure 1, the cylinder 22 is positioned so that its central axis extends in the vertical direction. A piston 23 is housed inside the cylinder 22. The piston 23 is positioned within the cylinder 22 so as to be movable in the direction of the cylinder 22's central axis.

[0012] The crankcase (not shown) is connected to the cylinder block 20 at one end (the lower side in Figure 1) of the cylinder 22 in the axial direction. The crankshaft 25 is housed in the crankcase so as to be rotatable around the crankshaft 25s. The piston 23 is connected to the crankpin 25p of the crankshaft 25 via a connecting rod 24. The crankpin 25p is positioned eccentrically with respect to the crankshaft 25s. Due to the combustion of fuel in the combustion chamber 26, which will be described later, the piston 23 reciprocates within the cylinder 22 along the axial direction of the cylinder 22 with a predetermined stroke. As a result of this reciprocating motion, the crankshaft 25 rotates around the crankshaft 25s. Based on this rotational motion, the generator produces electrical energy.

[0013] The number of cylinders 22 and pistons 23 in the engine body 2 may be only one (a so-called single-cylinder engine) or multiple (a so-called multi-cylinder engine). When multiple cylinders 22 are provided, their number can typically be, for example, 4, 5, 6, 8, 10, 12, etc. When multiple sets of cylinders 22 and pistons 23 are provided, the multiple pistons 23 are arranged at intervals in the direction in which the crankshaft 25s of the crankshaft 25 extends (the depth direction in the plane of the paper in Figure 1). In this case, the crankpins 25p to which each of the multiple pistons 23 is connected are provided at different positions in the circumferential direction of the crankshaft 25. As a result, the multiple pistons 23 operate within each cylinder 22 with a predetermined phase difference, rotating the crankshaft 25 around the crankshaft 25s.

[0014] The cylinder head 30 is connected to the cylinder block 20 on the end 22t of the cylinder 22 opposite to the crankshaft 25 in the direction of the central axis. The cylinder head 30 is formed to close the opening on the end 22t of the cylinder 22. A combustion chamber 26 is formed inside the engine body 2. The combustion chamber 26 is formed by being surrounded by the inner circumferential surface of the cylinder 22, the top surface of the piston 23, and a closing surface 30g in the cylinder head 30 that closes off the inside of the cylinder 22.

[0015] The cylinder head 30 has an air intake port 32 and an exhaust port 33. The air intake port 32 constitutes part of the air intake pipe P that supplies biomass gas to the combustion chamber 26. Fuel supplied from the air intake section 4, which will be described later, is sent into the combustion chamber 26 through the air intake port 32. The air intake port 32 has a port opening 32a that opens into the closed surface 30g of the cylinder head 30. The air intake port 32 communicates with the combustion chamber 26 through the port opening 32a.

[0016] The exhaust port 33 is a so-called exhaust port. Exhaust gas, generated by the combustion of fuel in the combustion chamber 26, is discharged from the exhaust port 33 to the outside of the engine body 2. The exhaust port 33 is connected to an external muffler or exhaust system (not shown). The exhaust port 33 has a port opening 33a that opens into the closed surface 30g of the cylinder head 30. The exhaust port 33 communicates with the combustion chamber 26 via the port opening 33a. The exhaust port 33 is equipped with an oxygen sensor 37 for measuring the oxygen concentration of the exhaust gas discharged from the combustion chamber 26.

[0017] The cylinder head 30 is equipped with an intake valve 35, an exhaust valve 36, and a spark plug 38. The intake valve 35 opens and closes the space between the combustion chamber 26 and the inside of the intake port 32. More specifically, the intake valve 35 is provided to open and close a communication section where the combustion chamber 26 and the intake pipe P (intake port 32) are connected and the combustion chamber 26 and the intake pipe P communicate with each other. The intake valve 35 comprises a valve body 35v and a valve stem 35s. The valve body 35v is formed to be able to close the port opening 32a facing the combustion chamber 26 in the intake port 32. The valve stem 35s is supported on the cylinder head 30 so as to be movable along its central axis. The intake valve 35 is driven in the direction of the central axis of the valve stem 35s by a cam 28 provided on the cylinder head 30, so that the valve body 35v opens and closes the port opening 32a of the intake port 32 at a predetermined timing. When this intake valve 35 opens, fuel is supplied into the combustion chamber 26 through the intake port 32.

[0018] The exhaust valve 36 includes a valve body 36v and a valve shaft portion 36s. The valve body 36v is formed to be able to close the port opening 33a facing the combustion chamber 26 in the exhaust port 33. The valve shaft portion 36s is supported by the cylinder head 30 so as to be movable along its central axis direction. The exhaust valve 36 is driven in the central axis direction of the valve shaft portion 36s by a cam (not shown) provided in the cylinder head 30, so that the valve body 36v opens and closes the port opening 33a of the exhaust port 33 at a predetermined timing. When this exhaust valve 36 opens, the exhaust gas generated in the combustion chamber 26 is discharged from the combustion chamber 26 through the exhaust port 33. <{

[0019] The tip of the spark plug 38 is provided so as to protrude into the combustion chamber 26 from the closing surface 30g of the cylinder head 30. The spark plug 38 generates a spark at a predetermined timing in a state where the combustion chamber 26 is filled with fuel, and ignites the fuel. As a result, the fuel burns in the combustion chamber 2�. The timing at which the spark plug 38 ignites is controlled by a control device 6 described later. Note that the configuration of the engine body 2 as described above is only an example, and appropriate changes are possible.

[0020] The air supply unit 4 supplies fuel to the combustion chamber 26 through the air supply port 32. The air supply unit 4 mainly includes an air supply pipe P, an air introduction pipe 42, a raw gas introduction pipe 43, and a first injection unit 46. The air supply pipe P includes the air supply port 32 already described and a surge tank 45. The air introduction pipe 42 is connected to the air supply pipe P and introduces air into the air supply pipe P. The air introduction pipe 42 takes in air from the outside through an air cleaner (not shown) and supplies the taken-in air to the air supply pipe P.

[0021] The raw gas introduction pipe 43 is connected to the air supply pipe P and introduces the raw gas supplied from the outside into the air supply pipe P. One end of the raw gas introduction pipe 43 is connected to the air supply pipe P. The other end of the raw gas introduction pipe 43 is connected to a facility (not shown) that generates the raw gas of the biomass gas BG.

[0022] The air supply pipe P connects the air inlet pipe 42, the raw gas inlet pipe 43, and the combustion chamber 26. In the air supply pipe P, the air introduced from the air inlet pipe 42 and the biomass gas BG introduced from the raw gas inlet pipe 43 are mixed. The mixture of raw gas and air thus produced becomes the biomass gas BG, which is burned as fuel in the combustion chamber 26.

[0023] A raw gas throttle valve 44 is provided in the raw gas inlet pipe 43. The raw gas throttle valve 44 adjusts the flow rate of raw gas by opening and closing the flow path within the raw gas inlet pipe 43. The raw gas throttle valve 44 adjusts the amount of raw gas introduced from the raw gas inlet pipe 43 to the air supply pipe P. The opening and closing operation of the raw gas throttle valve 44 is controlled by the control device 6. By controlling the opening degree of the raw gas throttle valve 44 by the control device 6, biomass gas BG, which is a mixture of raw gas and air in a predetermined ratio, is produced as fuel. In addition, by closing the raw gas throttle valve 44 completely, the amount of raw gas introduced from the raw gas inlet pipe 43 to the air supply port 32 can be set to 0 (zero).

[0024] The intake pipe P is equipped with a throttle valve 47. The opening degree of the throttle valve 47 is controlled by the control device 6. The throttle valve 47 adjusts the flow rate of biomass gas BG, which is a mixture of raw gas and air, by opening and closing the flow path in the intake pipe P. In addition, when the raw gas throttle valve 44 is in a fully closed state, the throttle valve 47 adjusts the flow rate of air introduced through the air inlet pipe 42.

[0025] The surge tank 45 is located between the throttle valve 47 and the air intake port 32. When the engine body 2 comprises multiple sets of cylinders 22 and pistons 23, the air intake port 32 communicating with each combustion chamber 26 is connected to the surge tank 45. In this case, the biomass gas BG or (if no raw gas is included) air introduced into the air intake pipe P is branched in the surge tank 45 and supplied to each of the multiple engine bodies 2.

[0026] The first injection unit 46 is located in the intake pipe P. The first injection unit 46 injects liquid volatile fuel FL towards the intake valve 35 inside the intake pipe P. More specifically, the first injection unit 46 injects the liquid volatile fuel FL towards the back side of the valve body 35v of the intake valve 35, that is, the surface of the valve body 35v that faces the intake pipe P, opposite to the surface that faces the combustion chamber 26. The first injection unit 46 cleans the intake valve 35 by injecting the liquid volatile fuel FL. The liquid volatile fuel FL injected from the first injection unit 46 cleans oil-washable contaminants such as tar components that adhere to the intake valve 35, etc., when biomass gas BG is used as fuel for the engine body 2. Examples of such liquid volatile fuel FL include gasoline and diesel fuel. In this embodiment, gasoline is used as the liquid volatile fuel FL. Furthermore, the liquid volatile fuel FL may contain, in addition to gasoline, components that enhance the cleaning effect of contaminants such as tar. The operation of the first injection unit 46 is controlled by the control device 6.

[0027] The control device 6 controls the operation of each part of the engine body 2 and the air intake unit 4. The control device 6 primarily controls the supply of fuel to the combustion chamber 26. The control device 6 controls the injection operation of liquid volatile fuel FL in the first injection unit 46. In order to perform these controls, the control device 6 monitors the state of each part of the engine body 2 and the air intake unit 4. For example, the control device 6 detects the rotation angle of the crankshaft 25 and the rotation angle of the cam 28 of the engine body 2 using sensors (not shown). Based on the detected rotation angle of the crankshaft 25 and the rotation angle of the cam 28, the control device 6 controls, for example, the injection timing of liquid volatile fuel FL in the first injection unit 46.

[0028] Furthermore, the control device 6 appropriately selects one of the following as the fuel to be supplied to the combustion chamber 26: biomass gas BG, liquid volatile fuel FL, or a mixture MG of biomass gas BG and liquid volatile fuel FL. When the control device 6 selects biomass gas BG as the fuel, it does not inject liquid volatile fuel FL in the first injection unit 46. In this case, the control device 6 opens the raw gas throttle valve 44 and mixes the air introduced from the air inlet pipe 42 with the raw gas introduced from the raw gas inlet pipe 43 to produce biomass gas BG as fuel. The produced biomass gas BG is supplied as fuel into the combustion chamber 26 through the air supply pipe P. In this embodiment, the control device 6 selects biomass gas BG as fuel during normal operation of the engine body 2.

[0029] When the control device 6 selects liquid volatile fuel FL as the fuel, it closes the raw gas throttle valve 44 and does not supply biomass gas BG. In this case, only air is introduced into the air supply pipe P from the air inlet pipe 42. The control device 6 injects the liquid volatile fuel FL using the first injection unit 46 and mixes it with the air introduced from the air inlet pipe 42. The mixture of liquid volatile fuel FL and air is supplied as fuel into the combustion chamber 26 through the air supply port 32.

[0030] In this embodiment, the control device 6 selects liquid volatile fuel FL as the fuel when starting the engine body 2 and when stopping the engine body 2. When starting the engine body 2, the control device 6 selects liquid volatile fuel FL as the fuel to warm up the engine body 2. When stopping the engine body 2, the control device 6 selects liquid volatile fuel FL as the fuel to clean the intake valve 35, as will be explained later.

[0031] When liquid volatile fuel FL is selected as the fuel, or when a mixture of biomass gas BG and liquid volatile fuel FL MG is selected as the fuel, as described below, liquid volatile fuel FL is injected from the first injection unit 46. The injected liquid volatile fuel FL collides with the air intake port 32 and the air intake valve 35, flows over the surface of the air intake port 32 and the air intake valve 35, and enters the combustion chamber 26, thereby washing away contaminants such as tar components attached to the valve body 35v of the air intake valve 35 and the surrounding area of ​​the air intake valve 35. The washed-away contaminants enter the combustion chamber 26 and are burned together with the liquid volatile fuel FL or the mixture of biomass gas BG and liquid volatile fuel FL MG.

[0032] When the control device 6 selects a mixture MG of biomass gas BG and liquid volatile fuel FL as the fuel, it opens the raw gas throttle valve 44 and mixes the air introduced from the air inlet pipe 42 with the raw gas introduced from the raw gas inlet pipe 43 to produce biomass gas BG as fuel. Furthermore, the control device 6 injects the liquid volatile fuel FL in the first injection unit 46. The injected liquid volatile fuel FL is mixed with the biomass gas BG to produce a mixture MG of biomass gas BG and liquid volatile fuel FL. The produced mixture MG is supplied as fuel into the combustion chamber 26 through the air supply port 32.

[0033] In this embodiment, the control device 6 cleans the air intake valve 35 during normal operation by selecting the mixture MG as fuel for a certain period of time at preset time intervals. In other words, when biomass gas BG is selected as fuel during normal operation, the control device 6 controls the injection of liquid volatile fuel FL from the first injection unit 46 to clean the area around the air intake valve 35, thereby supplying the combustion chamber 26 with a mixture MG of biomass gas BG and liquid volatile fuel FL as fuel.

[0034] Furthermore, the control device 6 selects the mixed fuel MG when transitioning from a state in which biomass gas BG is selected as the fuel to a state in which liquid volatile fuel FL is selected as the fuel, and also when transitioning from a state in which liquid volatile fuel FL is selected as the fuel to a state in which biomass gas BG is selected as the fuel.

[0035] When the control device 6 selects a mixture of biomass gas BG and liquid volatile fuel FL (MG) as fuel, it adjusts the supply amount of liquid volatile fuel FL according to the supply amount of raw gas. For this purpose, a raw gas pressure sensor 48 is provided in the raw gas inlet pipe 43. The raw gas pressure sensor 48 measures the pressure of the raw gas in the raw gas inlet pipe 43. When starting the internal combustion engine 1, the control device 6 operates the internal combustion engine 1 after warm-up, as will be explained later as the start-up adjustment operation. During this start-up adjustment operation, the control device 6 controls the injection amount of liquid volatile fuel FL to increase when the measured value of the raw gas pressure sensor 48 decreases. Also, during the start-up adjustment operation, the control device 6 controls the injection amount of liquid volatile fuel FL to decrease when the measured value of the raw gas pressure sensor 48 increases. This adjusts the mixing ratio of biomass gas BG and liquid volatile fuel FL to maintain the amount of the mixture MG of biomass gas BG and liquid volatile fuel FL supplied as fuel to the combustion chamber 26.

[0036] The control device 6 adjusts the opening degree of the raw gas throttle valve 44, the amount of liquid volatile fuel FL injected from the first injection unit 46, and the opening degree of the throttle valve 47 based on the oxygen concentration of the exhaust gas measured by the oxygen sensor 37, so as to maintain an appropriate air-fuel ratio.

[0037] Figure 2 shows an example of a method for controlling the operation of an internal combustion engine used for power generation using a control device. In the internal combustion engine 1 for power generation, it is required to maintain a constant torque in order to generate power stably in the generator. In particular, in the internal combustion engine 1 of this embodiment, when a mixture MG of biomass gas BG and liquid volatile fuel FL is used as fuel, the control device 6 adjusts the ratio of biomass gas BG and liquid volatile fuel FL so that the same torque is output as when only biomass gas BG is used as fuel or when only liquid volatile fuel FL is used. In Figure 2, the horizontal axis shows the time elapsed from the start to the stop of the internal combustion engine 1. The vertical axis shows the ratio of biomass gas (BG) to liquid volatile fuel (FL) required to maintain a constant torque.

[0038] As shown in Figure 2, when the control device 6 starts the engine body 2 (time T1 in Figure 2), it selects liquid volatile fuel FL as the fuel and starts the engine body 2. Subsequently, the control device 6 performs a warm-up operation of the engine body 2 using liquid volatile fuel FL (times T1 to T2 in Figure 2) until a predetermined time T2 has elapsed.

[0039] After the warm-up period is complete, the control device 6 selects the MG mixture as the fuel and proceeds to the start-up adjustment operation (time T2 in Figure 2). In equipment that generates raw biomass gas (BG), when the equipment starts up, the temperature of the furnace used to burn wood is gradually increased to reduce the load on the equipment when generating the raw gas. The amount of raw gas generated during this time is not constant but fluctuates. To compensate for this fluctuation in quantity, the internal combustion engine 1 of this embodiment uses liquid volatile fuel (FL) as a supplementary fuel to support the biomass gas (BG).

[0040] More specifically, during the startup adjustment operation (times T2-T3 in Figure 2), the amount of liquid volatile fuel FL injected in the first injection unit 46 is adjusted according to the supply status of biomass gas BG. During the startup adjustment operation, the control device 6 increases the amount of liquid volatile fuel FL injected when the raw gas pressure sensor 48 reading decreases, and decreases the amount of liquid volatile fuel FL injected when the raw gas reading increases. In this way, the control device 6 maintains a constant torque by adjusting the fuel supply to maintain a constant amount. When the control device 6 determines that the raw gas generating equipment has become able to generate raw gas stably, such as when the raw gas pressure sensor 48's measured value exceeds a predetermined set value (time T3 in Figure 2), it selects biomass gas BG as the fuel and switches to normal operation. Normal operation (times T3 to T12 in Figure 2) is the period from the end of the start-up adjustment operation until the start-up adjustment operation, which will be explained later, begins, during which biomass gas BG is used as the main fuel for the internal combustion engine 1 and the internal combustion engine 1 operates stably.

[0041] During normal operation, the control device 6 cleans the air intake valve 35 by selecting the mixture MG as fuel at predetermined intervals (times T4 and T8 in Figure 2) and until a certain period of time has elapsed (times T7 and T11 in Figure 2). In other words, when biomass gas BG is selected as fuel during normal operation, the control device 6 controls the injection of liquid volatile fuel FL from the first injection unit 46 to clean the area around the air intake valve 35, thereby supplying a mixture MG of biomass gas BG and liquid volatile fuel FL as fuel to the combustion chamber 26.

[0042] More specifically, when the control device 6 transitions from a state in which biomass gas BG is selected as the fuel during normal operation to a state in which the mixture MG is used as the fuel and the air intake valve 35 is cleaned, it adjusts the raw gas throttle valve 44 to reduce the amount of raw gas introduced and increases the amount of liquid volatile fuel FL injected into the first injection unit 46 (times T4-T5, T8-T9 in Figure 2). The control device 6 cleans the area around the air supply valve 35 for a certain period of time (times T5-T6 and T9-T10 in Figure 2). The control device 6 then adjusts the raw gas throttle valve 44 to increase the amount of raw gas introduced, while simultaneously reducing the amount of liquid volatile fuel FL injected in the first injection unit 46 (times T6-T7 and T10-T11 in Figure 2).

[0043] In the case where multiple engine bodies 2 are provided, the timing for cleaning the area around the intake valve 35 as described above may differ for each engine body 2, or it may be synchronized and the timing may be the same for all engine bodies 2, as long as the torque of the internal combustion engine 1 is maintained at a constant level.

[0044] Finally, when the control device 6 stops the engine body 2 from normal operation (time T12 in Figure 2), it first selects the mixed fuel MG. In this case, the control device 6 performs a stop adjustment operation (times T12-T13 in Figure 2) in which it gradually increases the amount of liquid volatile fuel FL injected into the first injection unit 46. During the stop adjustment operation, when the control device 6 transitions from a state in which biomass gas BG is selected as the fuel to a state in which it performs operation prior to stopping using the mixed fuel MG as the fuel, it gradually increases the amount of liquid volatile fuel FL injected while adjusting the raw gas throttle valve 44 to gradually reduce the amount of raw gas introduced. When the amount of raw gas introduced becomes zero (time T13 in Figure 2), the control device 6 selects liquid volatile fuel FL as the fuel and switches to a stop operation (times T13-T14 in Figure 2) to clean the intake valve 35. When a preset time has elapsed (time T14 in Figure 2), the control device 6 stops the stop operation and shuts down the engine body 2.

[0045] During the series of processes described above, the control device 6 adjusts the opening degree of the raw gas throttle valve 44, the amount of liquid volatile fuel FL injected from the first injection unit 46, and the opening degree of the throttle valve 47 based on the oxygen concentration of the exhaust gas measured by the oxygen sensor 37, so as to maintain an appropriate air-fuel ratio.

[0046] The internal combustion engine 1 for power generation described above comprises an engine body 2, an air intake pipe P, an air intake valve 35, a first injection unit 46, and a control device 6. The engine body 2 has a combustion chamber 26 formed inside for burning fuel. The air intake pipe P supplies biomass gas BG to the combustion chamber 26. The air intake valve 35 opens and closes the communication between the combustion chamber 26 and the air intake pipe P. The first injection unit 46 is installed inside the air intake pipe P to inject liquid volatile fuel FL towards the air intake valve 35 to clean the air intake valve 35. The control device 6 appropriately selects one of the following as the fuel to be supplied to the combustion chamber 26: biomass gas BG, liquid volatile fuel FL, or a mixture MG of biomass gas BG and liquid volatile fuel FL. With this type of internal combustion engine 1 for power generation, the first injection unit 46 injects liquid volatile fuel FL into the intake valve 35 inside the intake pipe P, thereby cleaning the intake valve 35 and its surroundings. This reduces the amount of contaminants such as tar that adhere to the intake valve 35 and its surroundings. Therefore, it is possible to suppress the occurrence of malfunctions such as the intake valve 35 sticking to the intake port 32. Furthermore, the liquid volatile fuel FL used to clean the intake valve 35 can be burned in the combustion chamber 26. Therefore, the liquid volatile fuel FL can be used as fuel to operate the internal combustion engine. Consequently, even if the liquid volatile fuel FL is used for cleaning, it is not wasted. Furthermore, in cases where, for example, biomass gas BG is not stably supplied to the internal combustion engine 1, in order to maintain the torque of the internal combustion engine 1, the internal combustion engine 1 is normally operated using only liquid volatile fuel FL without using biomass gas BG. Therefore, biomass gas BG is not used and is wasted. In contrast, in this embodiment, one of biomass gas BG, liquid volatile fuel FL, or a mixture MG of biomass gas and liquid volatile fuel FL is appropriately selected as the fuel supplied to the combustion chamber 26. For this reason, in cases such as the above, by selecting the mixture MG of biomass gas and liquid volatile fuel FL, liquid volatile fuel FL can be used as an auxiliary fuel to compensate for the variability of biomass gas BG and maintain the torque of the internal combustion engine 1, and biomass gas BG can be used without waste. Therefore, it is possible to provide an internal combustion engine 1 for power generation that can suppress malfunctions and operate efficiently using fuel.

[0047] In particular, in the internal combustion engine 1 described above, the intake valve 35 is cleaned with liquid volatile fuel FL, so even wood containing a large amount of tar, such as thinned wood, can be used as fuel when producing biomass gas BG. In this way, it becomes possible to produce biomass gas BG using wood that would normally be difficult to use as fuel, thus enabling the effective utilization of wood.

[0048] Furthermore, during normal operation (times T3 to T12 in Figure 2), the control device 6 selects biomass gas BG as fuel, and during that time, selects the mixed fuel MG for a certain period of time to clean the air intake valve 35. With this configuration, during normal operation, the mixed MG is selected as the fuel for a certain period of time. That is, while biomass gas BG is being used as fuel, liquid volatile fuel FL is injected from the first injection unit 46 to supply the mixed MG as fuel to the combustion chamber 26. As a result, the liquid volatile fuel FL contained in the mixed MG cleans the intake valve 35, reducing the amount of contaminants such as tar that have accumulated during normal operation.

[0049] Furthermore, when starting the engine body 2, the control device 6 selects liquid volatile fuel FL as the fuel and performs a warm-up operation (times T1-T2 in Figure 2). After that, the control device 6 selects mixed fuel MG as the fuel and performs a startup adjustment operation (times T2-T3 in Figure 2) to adjust the amount of liquid volatile fuel FL injected in the first injection unit 46 according to the supply status of biomass gas BG, before transitioning to normal operation. With the above configuration, the engine body 2 can be easily and stably started by first performing a warm-up operation. Furthermore, after warming up, a start-up adjustment operation is performed in which a mixed MG is selected as the fuel, and the amount of liquid volatile fuel FL injected in the first injection unit 46 is adjusted according to the supply status of biomass gas BG. This allows the engine body 2 to transition to normal operation stably while making efficient use of the biomass gas BG, even in situations where the supply of biomass gas BG is unstable, from the start of biomass gas BG production until the supply of biomass gas BG becomes stable.

[0050] Furthermore, the internal combustion engine 1 includes an air intake pipe 42 for introducing air into the intake pipe P, a raw gas intake pipe 43 for introducing raw gas supplied from the outside into the intake pipe P, and a raw gas pressure sensor 48 provided in the raw gas intake pipe 43 for measuring the pressure of the raw gas. Biomass gas BG is a mixture of air and raw gas. During startup adjustment operation, the control device 6 increases the injection amount of liquid volatile fuel FL when the measurement value of the raw gas pressure sensor 48 decreases, and decreases the injection amount of liquid volatile fuel FL when the measurement value of the raw gas pressure sensor 48 increases. With this configuration, the supply amount of liquid volatile fuel FL can be automatically adjusted in response to increases or decreases in the supply amount of biomass gas BG. This stabilizes the amount of fuel supplied to the combustion chamber 26, thereby maintaining a constant torque for the internal combustion engine 1. Therefore, even in situations where the supply of raw gas is not stable, the engine body 2 can be stably transitioned to normal operation while making efficient use of the raw gas.

[0051] Furthermore, the internal combustion engine 1 is equipped with an air inlet pipe 42 for introducing air into the air intake pipe P, a raw gas inlet pipe 43 for introducing raw gas supplied from the outside into the air intake pipe P, and a raw gas throttle valve 44 for adjusting the amount of raw gas introduced from the raw gas inlet pipe 42 to the air intake pipe P. Biomass gas BG is a mixture of air and raw gas. When the control device 6 transitions from a state in which biomass gas BG is selected as the fuel to a state in which the mixture MG is selected as the fuel (times T4-T5, T8-T9, T12-T13 in Figure 2), it adjusts the raw gas throttle valve 44 to reduce the amount of raw gas introduced. With the above configuration, for example, when cleaning the intake valve 35 during normal operation, or during stop-down adjustment operation when transitioning from normal operation to stop-down operation, the raw gas throttle valve 44 is adjusted to reduce the amount of raw gas introduced when increasing the injection amount of liquid volatile fuel FL and transitioning to a state where the mixture MG is selected as the fuel, thereby maintaining a constant torque of the internal combustion engine 1.

[0052] Furthermore, when stopping the engine body 2 from normal operation, the control device 6 selects the mixed fuel MG as the fuel and performs a stop adjustment operation (times T12-T13 in Figure 2) in which the amount of liquid volatile fuel FL injected into the first injection unit 46 is gradually increased. After that, it selects the liquid volatile fuel FL as the fuel and proceeds to a stop operation (times T13-T14 in Figure 2) in which the intake valve 35 is cleaned. With the above configuration, when stopping the internal combustion engine 1, a stop adjustment operation is performed in which the injection amount of liquid volatile fuel FL is gradually increased, allowing for a smooth transition to a stop operation in which liquid volatile fuel FL is selected as the fuel. Furthermore, during shutdown operation, by selecting liquid volatile fuel FL as the fuel, the intake valve 35 can be cleaned with liquid volatile fuel FL, reducing the amount of contaminants such as tar components that adhere to it, and the internal combustion engine 1 can be stopped. As a result, when starting the engine body 2 next time, it is possible to prevent the intake valve 35 from sticking to the intake port 32, which would make starting difficult.

[0053] Furthermore, the internal combustion engine 1 is equipped with an air inlet pipe 42 for introducing air into the air intake pipe P, a raw gas inlet pipe 43 for introducing raw gas supplied from an external source into the air intake pipe P, and a raw gas throttle valve 44 for adjusting the amount of raw gas introduced from the raw gas inlet pipe 42 to the air intake pipe P. Biomass gas BG is a mixture of air and raw gas. During stop-and-adjust operation, the control device 6 gradually increases the injection amount of liquid volatile fuel FL while gradually reducing the amount of raw gas introduced by adjusting the raw gas throttle valve 44. With the above configuration, when gradually increasing the injection amount of liquid volatile fuel FL during stop-and-adjustment operation, the amount of raw gas introduced is gradually reduced, thereby enabling the torque of the internal combustion engine 1 to be kept constant during stop-and-adjustment operation.

[0054] Furthermore, the liquid volatile fuel FL is gasoline. With the above configuration, it is possible to easily achieve both cleaning performance against contaminants such as tar components and the function of a supplementary fuel to support the biomass gas BG of the internal combustion engine 1.

[0055] (Modified examples of the embodiment) It should be noted that the internal combustion engine for power generation of the present invention is not limited to the embodiments described above with reference to the drawings, and various modifications are conceivable within its technical scope. For example, in the above embodiment, the first injection unit 46 is provided inside the air intake port 32 to inject liquid volatile fuel FL toward the air intake valve 35, but it is not limited to this. Figure 3 is a schematic diagram showing the configuration of an internal combustion engine for power generation in a modified embodiment of the present invention. As shown in Figure 3, the air intake section 4B of the internal combustion engine 1B for power generation in this modified example includes second injection sections 49A and 49B in addition to the configuration of the air intake section 4 shown in the above embodiment. The second injection units 49A and 49B are located in different positions from the first injection unit 46. The second injection units 49A and 49B inject liquid volatile fuel FL into a part of the air intake port 32 that is different from the air intake valve 35. More specifically, the second injection units 49A and 49B inject liquid volatile fuel FL into a part of the air intake port 32 that is located upstream of the air intake valve 35 in the direction of biomass gas BG inflow, thereby cleaning the part upstream of the air intake valve 35 to which the liquid volatile fuel FL was injected. In the example shown in Figure 3, the second injection units 49A and 49B are provided in two locations to inject liquid volatile fuel FL into the surge tank 45 and towards the throttle valve 47. The positions and number of second injection units 49A and 49B are not limited to these and can be changed as appropriate.

[0056] In other words, the modified internal combustion engine 1B for power generation further includes second injection units 49A and 49B that inject liquid volatile fuel FL into the part of the intake pipe P upstream of the intake valve 35 to clean that part. With this configuration, the second injection units 49A and 49B inject liquid volatile fuel FL towards the portion upstream of the air intake valve 35, cleaning that portion. As a result, even in the portion upstream of the air intake valve 35, the amount of contaminants such as tar components that have accumulated can be reduced by the injected liquid volatile fuel FL.

[0057] (Other variations) In the above embodiment, a mixture MG of biomass gas BG and liquid volatile fuel FL was used to clean the air intake valve 35. However, when cleaning the air intake valve 35, the supply of biomass gas BG may be stopped, and only liquid volatile fuel FL may be supplied as fuel to the combustion chamber 26. Furthermore, in the above embodiment, the liquid volatile fuel FL used to clean the air intake valve 35 is used when starting and stopping the engine body 2, but for example, different types of liquid volatile fuel may be used for cleaning the air intake valve 35 and for improving the starting stability of the engine body 2 when starting the engine body 2. Furthermore, the control method in the control device 6 shown in Figure 2 of the above embodiment is merely an example, and its contents, processing order, etc., can be changed as appropriate.

[0058] Furthermore, in the above embodiment, in the equipment that generates the raw gas for biomass gas BG, in particular, attention was paid to the fact that variations in the production amount tend to occur when the equipment starts up. Therefore, the equipment is configured to transition to normal operation after undergoing a startup adjustment operation that adjusts the injection amount of liquid volatile fuel FL in the first injection unit 46 according to the supply status of biomass gas BG. However, after the internal combustion engine 1 has transitioned to normal operation, the measured value of the raw gas pressure sensor 48 may be checked at any time. If the measured value of the raw gas pressure sensor 48 decreases, the injection amount of liquid volatile fuel FL may be increased, and if the measured value of the raw gas pressure sensor 48 increases, the injection amount of liquid volatile fuel FL may be decreased. With this configuration, even if there are fluctuations in the supply of raw gas during normal operation of the internal combustion engine 1, the torque can be kept constant.

[0059] In addition to the above, it is possible to select or replace the configurations listed in the above embodiments, or to change them to other configurations as appropriate, as long as it does not deviate from the spirit of the present invention. [Explanation of symbols]

[0060] 1. 1B Internal Combustion Engine 2. Engine body 6. Control device 26 Combustion chamber 35 Air supply valve 42 Air intake pipe 43 Raw gas introduction pipe 44 Raw gas throttle valve 46 1st injection part 48 Raw Gas Pressure Sensor 49A, 49B 2nd injection part BG Biomass Gas FL Liquid volatile fuel MG mixture P Air supply pipe

Claims

1. An internal combustion engine for power generation, The engine body has a combustion chamber formed inside for burning fuel, A supply pipe for supplying biomass gas to the combustion chamber, An air intake valve that opens and closes the communication portion between the combustion chamber and the air intake pipe, An air inlet pipe for introducing air into the aforementioned air supply pipe, A raw gas introduction pipe for introducing raw gas supplied from the outside into the aforementioned air intake pipe, A raw gas pressure sensor is provided in the raw gas introduction pipe to measure the pressure of the raw gas, A first injection unit is provided inside the air intake pipe to inject liquid volatile fuel toward the air intake valve and clean the air intake valve, The system includes a control device that appropriately selects one of the following as the fuel supplied to the combustion chamber: the biomass gas, the liquid volatile fuel, or a mixture of the biomass gas and the liquid volatile fuel. The biomass gas is a mixture of the air and the raw gas. The control device, during normal operation, selects the biomass gas as the fuel, and during that time, selects the mixture as the fuel for a certain period of time to clean the air intake valve. When starting the engine body, the control device selects the liquid volatile fuel as the fuel and performs a warm-up operation. After that, it selects the mixture as the fuel and performs a startup adjustment operation to adjust the amount of liquid volatile fuel injected in the first injection unit according to the supply status of the biomass gas, before proceeding to normal operation. The control device is an internal combustion engine for power generation that, during the startup adjustment operation, increases the injection amount when the measured value of the raw gas pressure sensor decreases, and decreases the injection amount when the measured value increases.

2. A raw gas throttle valve is provided to adjust the amount of raw gas introduced from the raw gas introduction pipe to the air supply pipe, The control device, when transitioning from a state in which biomass gas is selected as the fuel to a state in which the mixture is selected as the fuel, adjusts the raw gas throttle valve to reduce the amount introduced, as described in claim 1.

3. The control device, when stopping the engine body from normal operation, selects the mixture as the fuel and performs a stop adjustment operation in which the amount of liquid volatile fuel injected in the first injection unit is gradually increased, and then selects the liquid volatile fuel as the fuel and proceeds to a stop operation in which the intake valve is cleaned, as described in claim 1.

4. A raw gas throttle valve is provided to adjust the amount of raw gas introduced from the raw gas introduction pipe to the air supply pipe, The control device, during the stop adjustment operation, gradually increases the injection amount while adjusting the raw gas throttle valve to gradually decrease the amount introduced, as described in claim 3, for an internal combustion engine for power generation.

5. The internal combustion engine for power generation according to claim 1, further comprising a second injection unit for injecting the liquid volatile fuel into the portion of the intake pipe upstream of the intake valve to clean the portion.

6. The internal combustion engine for power generation according to any one of claims 1 to 5, wherein the liquid volatile fuel is gasoline.

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