JP2006322365A - Fuel system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel system capable of taking a measure for leak of fuel evaporating at ambient temperature and atmosphere pressure without affecting the output of an internal combustion engine. <P>SOLUTION: Liquefied DME fuel from a DME tank 1 is pressurized to a primary pressure by a primary pump 5, is pressurized to a secondary pressure by a secondary pump 7 and is supplied to a fuel injection pump 3. The DME fuel pressurized to an injection pressure in the fuel injection pump 3 is supplied to a fuel injector 4. Excess fuel not supplied from the fuel injection pump 3 to the fuel injector 4 is returned between the primary pump 5 and the secondary pump 7 through a fuel recirculation pipe 11. The DME fuel leaked from between a plunger 31 and a plunger barrel 32 in the fuel injection pump 3 is returned to the fuel recirculation pipe 11 though a plunder leak pipe 17. The DME fuel in the fuel recirculation pipe 11 is maintained at the primary pressure or above by a pressure regulating valve 12 and an accumulator 13 and therefore the DME fuel of the fuel recirculation pipe 11 can be stably recirculated to a fuel main pipe 2 while being kept in the liquefied condition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present application relates to a fuel system system, and more particularly, to a fuel system system that supplies fuel that is gaseous at normal temperature and atmospheric pressure to an internal combustion engine.

  Conventionally, diesel engines using light oil or heavy oil as fuel have been affected by the environmental impact of PM (particulate matter) and NOx (nitrogen oxides) contained in the exhaust gas. Diesel engines using alternative fuels have been proposed. As an alternative fuel, DME (dimethyl ether), which has substantially the same cetane number as light oil, has a small amount of PM contained in the exhaust gas after combustion, and has an advantage of easily reducing the concentration of NOx, Attention has been paid.

  However, since DME is a gas at room temperature and atmospheric pressure and has a lower viscosity than light oil, the fuel system of a diesel engine using DME as a fuel has a stricter countermeasure against leakage than when using light oil as a fuel. Necessary. Conventionally, as a fuel system system for DME in consideration of leakage countermeasures, DME gas leaked into the plunger lower chamber from the gap between the plunger of the fuel injection pump and the plunger barrel is sucked into the combustion chamber of the diesel engine. Has been proposed (see, for example, Japanese Patent Laid-Open No. 10-281029: Patent Document 1). In this fuel system, the fuel efficiency of the diesel engine is improved by inhaling the leaked DME gas into the combustion chamber as compared with the case of releasing the leaked DME gas into the atmosphere.

However, in the conventional fuel system, the amount of leakage from the plunger lower chamber is large because the DME supplied to the fuel injection pump is at a high pressure. In addition, since the viscosity of DME changes greatly with changes in temperature, the leak amount fluctuates within a large range with changes in temperature due to changes in the operating state of the diesel engine and changes in ambient temperature. Therefore, the fuel system system supplies DME fuel to the combustion chamber with a large fluctuation range regardless of the control of the fuel injection device. As a result, the fuel system has a problem that the output of the diesel engine becomes unstable.
JP-A-10-281029

  Accordingly, an object of the present invention is to provide a fuel system that can take measures against leakage of fuel vaporized at normal temperature and atmospheric pressure without affecting the output of the internal combustion engine.

In order to solve the above problems, the fuel system of the present invention is:
A fuel tank for storing fuel that vaporizes at room temperature and atmospheric pressure;
A primary pressure increasing unit for increasing the pressure of the fuel supplied from the fuel tank to a primary pressure;
A secondary booster connected to the downstream side of the primary booster and boosting the pressure of the fuel from the primary booster to a secondary pressure;
A fuel injection pump connected to the downstream side of the secondary booster and boosting the pressure of the fuel from the secondary booster to an injection pressure;
A fuel injection device to which fuel at the injection pressure is supplied from the fuel injection pump;
A first return pipe for returning the fuel leaked from the fuel injection pump between the primary booster and the secondary booster in a state where the leaked fuel has a pressure higher than the primary pressure; It is characterized by that.

  According to the above configuration, the fuel stored in the fuel tank is boosted to the primary pressure by the primary booster, and further boosted to the secondary pressure by the secondary booster. The fuel boosted to the secondary pressure is boosted to the injection pressure by the fuel injection pump and sent from the fuel injection pump to the fuel injection device. The fuel leaking from the fuel injection pump is returned between the primary booster and the secondary booster by the first return pipe. Therefore, even if the amount of fuel leakage from the fuel injection pump fluctuates, the fluctuation of the output of the internal combustion engine as in the conventional case where the leaked fuel is supplied to the combustion chamber of the internal combustion engine does not occur. Therefore, the output of the internal combustion engine using this fuel system can be stabilized. The fuel leaked from the fuel injection pump is not only the fuel leaked from the sliding surface of the plunger of the fuel injection pump, for example, but also excess fuel that was not supplied from the fuel injection pump to the fuel injection device. Also means.

  The fuel leaking from the fuel injection pump is returned between the primary booster and the secondary booster by the primary return pipe, and the fuel between the primary booster and the secondary booster. Is made a secondary pressure by the secondary booster. Therefore, the liquefied fuel is stably supplied to the fuel injection pump. Therefore, since the fuel injection pump can stably supply the fuel of a predetermined injection pressure to the fuel injection device, the output of the internal combustion engine using the fuel system can be stabilized.

  The fuel returned by the first return pipe has a pressure higher than the primary pressure, and the fuel pressure between the primary booster and the secondary booster to which the fuel is returned is the primary pressure. Because of the pressure, the leaked fuel is quickly returned between the primary booster and the secondary booster due to the pressure difference. Therefore, this fuel system system can efficiently collect leaked fuel.

  Note that any fuel such as DME (dimethyl ether), butane or propane can be used as the fuel that is vaporized at normal temperature and atmospheric pressure.

  A fuel system system according to an embodiment includes a lubricating oil supply unit that supplies lubricating oil having a pressure equal to or higher than the secondary pressure to the fuel injection pump.

  According to the above embodiment, the fuel injection pump is supplied with the secondary pressure fuel, while the fuel injection pump is supplied with the lubricating oil having the secondary pressure or higher from the lubricating oil supply unit. Fuel leakage from the injection pump can be effectively prevented. In particular, when the fuel injection pump includes a plunger and a plunger barrel that accommodates the plunger, and the lubricating oil of the secondary pressure or higher is supplied to the gap between the plunger and the plunger barrel, fuel leakage effectively occurs. Is reduced. The lubricating oil having a pressure equal to or higher than the secondary pressure can reduce fuel leakage more effectively than, for example, a seal ring or the like, particularly when the viscosity of the fuel decreases and leakage easily occurs at high temperatures. it can.

  The fuel system of one embodiment includes a second return pipe that returns the fuel leaked from the fuel injection device between the primary booster and the secondary booster.

  According to the above embodiment, the fuel leaked from the fuel injection device is returned between the primary booster and the secondary booster by the second return pipe, so that the discharge of fuel to the outside is effectively reduced. Thus, the fuel efficiency of the internal combustion engine to which the fuel system supplies the fuel can be improved effectively. Further, it is possible to effectively prevent inconveniences such as a fire and an adverse effect on the environment due to the fuel vaporizing around the internal combustion engine.

The fuel system of one embodiment is connected to a fuel high-pressure pipe through which fuel at an injection pressure discharged from the fuel injection pump flows, and a first leak detection pipe for flowing leaked fuel in the fuel high-pressure pipe;
A first leak detector for detecting the flow of fuel in the first leak detector;
A leak fuel storage tank for storing fuel from the first leak detection pipe;
A first discharge pipe for releasing the fuel in the leak fuel storage tank to the atmosphere;
A second leak detection pipe for flowing a leaked fuel at a connecting portion between the fuel injection pump and a drive mechanism for applying a driving force to the fuel injection pump;
A second leak detector for detecting the flow of fuel in the second leak detector tube;
A leaked oil recovery tank for storing fuel from the second leak detection pipe;
A second discharge pipe for releasing the fuel in the oil leakage recovery tank to the atmosphere.

  According to the embodiment, when the fuel leaks in the fuel high-pressure pipe through which the fuel of the injection pressure discharged from the fuel injection pump flows, the leaked fuel flows through the first detection pipe, and the first The leak detector detects a fuel leak. The leak fuel is stored in the leak fuel storage tank, and the leak fuel is released to the atmosphere through the first discharge pipe by opening a discharge valve or the like provided in the fuel storage tank. For example, by issuing an alarm based on the output from the first leak detector, it is possible to quickly cope with fuel leakage at the injection pressure.

  Further, when the fuel injection pump is driven by, for example, a cam mechanism as a drive mechanism, fuel leakage may occur in, for example, a tappet chamber as a connecting portion between the cam mechanism and the fuel injection pump. When a fuel leak occurs in the tappet chamber, the leaked fuel flows through the second leak detection pipe, and the fuel leak is detected by the second leak detector. The leaked fuel is collected in the leaked oil recovery tank. By opening a discharge valve or the like provided in the leaked oil recovery tank, the leaked fuel is released to the atmosphere via the second discharge pipe. For example, by issuing an alarm based on the output from the second leak detection unit, it is possible to quickly cope with the leak from the connection unit.

  The first and second leak detection units may be interposed in the first and second leak detection tubes, or may be provided downstream of the first and second leak detection tubes. In short, it is only necessary to detect the fuel flow from the fuel high-pressure pipe and the connecting portion of the fuel injection pump by detecting the flow of fuel in the first and second leak detection pipes.

In the fuel system of one embodiment, the first return pipe includes a surplus recovery pipe that returns surplus fuel that has not been supplied from the fuel injection pump to the fuel injection device, and leak fuel in a compression element of the fuel injection pump. Including a compression element leak pipe,
A purge supply pipe that is provided downstream of the fuel injection pump and supplies a purge fluid to be replaced with fuel;
A purge recovery pipe provided in an excess recovery pipe of the first return pipe for recovering the fuel replaced with the purge fluid;
A first residual fuel discharge pipe that is provided in the compression element leak pipe of the first return pipe and discharges leaked fuel remaining in the compression element of the fuel injection pump;
A second residual fuel discharge pipe which is provided in the second return pipe and discharges leaked fuel remaining in the fuel injection device.

  According to the above embodiment, for example, when the internal combustion engine to which fuel is supplied in this fuel system system is stopped, the purge fluid is supplied to the upstream side of the fuel injection pump via the purge supply pipe. The purge fluid flows into the fuel injection pump, and the fuel remaining in, for example, the compression chamber in the fuel injection pump is recovered through the excess recovery pipe and the purge recovery pipe. Further, the leaked fuel remaining in the compression element of the fuel injection pump is discharged from the first residual fuel discharge pipe through the compression element leak pipe. The leak fuel remaining in the compression element of the fuel injection pump is, for example, fuel remaining in the gap between the plunger as the compression element and the plunger barrel. Further, the fuel remaining in the fuel injection device is discharged from the second residual fuel discharge pipe through the second return pipe. In this way, since the fuel in the fuel injection pump and the fuel injection device is prevented from remaining, the fuel remaining in the fuel system after the internal combustion engine is stopped may be vaporized to affect the fuel system. It is possible to effectively prevent leakage to the outside of the fuel system and affect the surrounding environment.

  In one embodiment, the fuel includes DME (dimethyl ether).

  According to the embodiment, the fuel system can efficiently supply the fuel containing DME to the internal combustion engine, and can stabilize the output control of the internal combustion engine. The fuel may contain other diesel fuels and additives in addition to DME, or may be pure DME only.

  As described above, the fuel system of the present invention includes a primary boosting unit that boosts fuel from a fuel tank to a primary pressure with fuel that is vaporized at room temperature and atmospheric pressure leaked from a fuel injection pump, and the primary boosting unit. Since the first return pipe returns the fuel from the booster to the secondary booster that boosts the secondary pressure to the secondary pressure, even if the amount of fuel leakage from the fuel injection pump fluctuates, The output can be prevented from fluctuating, and the fuel can be returned between the primary booster and the secondary booster while being liquid.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 is a schematic diagram showing a fuel system as an embodiment of the present invention. In this fuel system, DME fuel mainly composed of DME (dimethyl ether) is supplied to a diesel engine as an internal combustion engine as fuel that is vaporized at normal temperature and atmospheric pressure. This diesel engine drives a generator of a cogeneration device. The DME fuel may contain other diesel fuels and additives, or only pure DME.

  As shown in FIG. 1, this fuel system includes a DME tank 1 as a fuel tank for storing liquefied DME fuel, and a fuel injection pump to which DME fuel is supplied from the DME tank 1 via a fuel main pipe 2. 3 and a fuel injection device 4 to which DME fuel having a predetermined injection pressure is supplied from the fuel injection pump 3. The fuel main pipe 2 includes, in order from the DME tank 1 side, a primary pump 5 as a primary booster, a primary filter 6, a secondary pump 7 as a secondary booster, a secondary filter 8, and an accumulator 9. It is installed. The number of fuel injection pumps 3 corresponding to the number of cylinders of the diesel engine is connected to the fuel main pipe 2, but only one fuel injection pump 3 is shown in FIG.

  The fuel injection pump 3 is connected to a fuel recirculation pipe 11 serving as a surplus recovery pipe for returning surplus fuel between the primary pump 5 and the secondary pump 7 of the fuel main pipe 2. Note that, similarly to the fuel main pipe 2, another fuel injection pump 3 (not shown) is connected to the fuel return pipe 11. The fuel return pipe 11 is provided with a pressure regulating valve 12 for adjusting the pressure of excess fuel flowing from the fuel injection pump 3, and an accumulator 13 for stabilizing the pressure in the fuel return pipe 11 is connected. ing. Further, the fuel return pipe 11 is provided with a cooler 14 for cooling the DME fuel, and is connected to the fuel main pipe 2 through a check valve 15.

  The fuel injection pump 3 is connected to a plunger leak pipe 17 as a compression element leak pipe for returning a DME fuel leak from a compression element, which will be described later, to the fuel main pipe 2. The plunger leak pipe 17 is connected to the fuel return pipe 11 via a check valve 18.

  A fuel high-pressure pipe 103 through which DME fuel having an injection pressure discharged from the fuel injection pump flows is connected to the upper portion of the fuel injection pump 3, and the fuel high-pressure pipe 103 serves as a first leak detection pipe. The high-pressure leak pipe 20 is connected. A storage tank 21 for temporarily storing leaked DME fuel is connected to the downstream side of the high-pressure leak pipe 20. The storage tank 21 includes a leak detector 22 for detecting a DME leak, and a pressure for detecting the pressure in the storage tank 21 and operating the leak detector 22 when a pressure equal to or higher than a predetermined value is detected. A switch 23 is provided. The storage tank 21 is provided with a storage tank discharge pipe 105 as a first discharge pipe for releasing the DME fuel in the storage tank 21 to the atmosphere. Is provided.

  Further, the fuel injection pump 3 is connected with a tappet leak pipe 25 as a second leak detection pipe for flowing a DME fuel leaked from a tappet chamber 34 to be described later and detecting the leak in the tappet chamber 34. Yes. In this case, the tappet chamber 34 corresponds to a connection portion. An oil leakage recovery tank 26 that recovers oil leakage is connected to the downstream side of the tappet leak pipe 25. The oil leakage recovery tank 26 is provided with a leakage detector 27 that detects DME fuel and detects fuel leakage from the tappet chamber 34. The oil leak recovery tank 26 is connected to a reflux bypass pipe 73 described later via an oil leak tank discharge pipe 107. By opening an on-off valve 75 interposed in the oil leakage tank discharge pipe 107, the DME fuel in the oil leakage tank 26 is discharged from the oil leakage tank discharge pipe 107, the reflux bypass pipe 73, and a second residual gas discharge described later. It can be released to the atmosphere via line 57. As described above, the oil leakage tank discharge pipe 107, the reflux bypass pipe 73, and the second residual gas discharge line 57 constitute a second discharge pipe.

  The fuel injection device 4 is connected to a nozzle leak pipe 28 that returns the leaked DME fuel to the fuel main pipe 2. The downstream end of the nozzle leak pipe 28 is connected to the fuel via a check valve 29. It is connected to the reflux pipe 11.

  An open / close valve 51 is provided between the secondary filter 8 and the accumulator 9 of the fuel main pipe 2 and is closed when the purge gas is supplied, and a purge gas supply pipe 52 as a purge supply pipe for supplying the purge gas is provided. It is connected.

  A first residual gas discharge line 54 as a first residual fuel discharge pipe for discharging the compression element of the fuel injection pump 3 and the DME fuel remaining in the plunger leak pipe 17 is provided in the middle of the plunger leak pipe 17. An open / close valve 55 is interposed in the first residual gas discharge line 54.

  Further, a second residual gas discharge line 57 as a second residual fuel discharge pipe for discharging the DME fuel leaking and remaining in the fuel injection device 4 is connected in the middle of the nozzle leak pipe 28, An open / close valve 58 is interposed in the second residual gas discharge line 57.

  A purge gas recovery pipe 60 as a purge recovery pipe for recovering the DME fuel replaced with the purge gas flowing through the fuel main pipe 2, the fuel injection pump 3 and the fuel return pipe 11 is provided in the middle of the fuel return pipe 11. An open / close valve 61 is interposed downstream of the connection position of the purge gas recovery pipe 60 of the fuel recirculation pipe 11.

  A combustion chamber communication pipe 63 communicating with the outside is connected to the combustion chamber of the diesel engine, and a pressure device 64 for displaying the pressure in the combustion chamber is interposed in the combustion chamber communication pipe 63. The combustion chamber communication pipe 63 is provided with an open / close valve 65, and by opening the open / close valve 65, the residual gas in the combustion chamber can be opened to the atmosphere.

  The fuel return pipe 11 is provided with a purge bypass pipe 70 that bypasses the inflow of the purge gas to the pressure regulating valve 12, and an open / close valve 71 is interposed in the purge bypass pipe 70. A reflux bypass pipe 73 is connected between the fuel return pipe 11 and the second residual gas discharge line 57 connected to the fuel injection device 4, and an open / close valve 74 is connected to the reflux bypass pipe 73. It is installed.

  FIG. 2 is a cross-sectional view showing the fuel injection pump 3. The fuel injection pump 3 includes a plunger 31 and a plunger barrel 32 as compression elements in a main body casing 30. A compression chamber 33 for compressing DME fuel is formed between the upper end surface of the plunger 31 and the plunger barrel 32. A tappet chamber 34 in which a tappet that drives the plunger 31 upward is accommodated is provided on the lower side of the main body casing 30 in FIG. Reference numeral 35 denotes a spring that urges the plunger 31 downward. A cam mechanism (not shown) for driving the tappet is provided below the tappet chamber 34. A fuel supply passage 36 to which secondary pressure DME fuel is supplied through the fuel main pipe 2 communicates with the compression chamber 33, and a fuel discharge passage for discharging fuel that does not need to be supplied to the fuel injection device 4. 37 communicates. The fuel discharge passage 37 is connected to the fuel return pipe 11.

  The plunger barrel 32 is formed with a groove 32a for guiding lubricating oil so as to face the sliding surface between the plunger barrel 32 and the plunger 31. The groove 32 a communicates with an oil supply passage 38 formed in the main body casing 30 and the plunger barrel 32. The oil supply passage 38 is connected to a lubricating oil pump (not shown) that supplies lubricating oil having a pressure higher than the secondary pressure via a lubricating oil pipe 67 (see FIG. 1). Further, the groove 32 a communicates with an oil drain passage 39 formed in the main body casing 30 and the plunger barrel 32, and the lubricating oil that lubricates the sliding surface is discharged through the oil drain passage 39. The The oil drain passage 39 is connected to the plunger leak pipe 17. The lubrication effect of the sliding surface is improved by circulating high-pressure lubricating oil having a secondary pressure or higher to the sliding surface between the plunger 31 and the plunger barrel 32 by the oil supply passage 38 and the oil discharge passage 39, and The leakage of DME fuel having a relatively low viscosity is effectively prevented. The lubricating oil supply section of the present invention is constituted by the lubricating passage 38, the lubricating oil pipe 67, and the lubricating oil pump.

  FIG. 3 is a cross-sectional view showing the fuel injection device 4. The fuel injection device 4 is accommodated in a cylinder head of a diesel engine. The fuel injection device 4 has a generally cylindrical holder 42, and a fuel passage 41 that guides fuel at an injection pressure from the fuel injection pump 3 is formed in the holder 42. A nozzle 43 having a nozzle hole at the tip is fixed to the tip of the holder 42 via a spacer. The tip of the nozzle 43 faces the combustion chamber of the diesel engine. A needle valve 45 is accommodated inside the nozzle 43. A spring 47 that urges the needle valve 45 toward the tip of the nozzle is housed inside the holder 42, and the tip of the needle valve 45 that is urged by the spring 47 is connected to the nozzle 43. The nozzle is closed. The holder 42 is provided with a leak passage 49 for discharging DME fuel leaking from the fuel passage 41. The leak passage 49 is connected to the nozzle leak pipe 28.

  The fuel system of the above configuration operates as follows.

  The DME tank 1 pressurizes the DME fuel to a pressure equal to or higher than the vapor pressure (for example, 0.6 MP) and maintains the liquefied state. The primary pump 5 boosts the DME fuel from the DME tank 1 to a predetermined primary pressure (for example, 1.2 MP), and the primary filter 6 filters the primary pressure DME fuel. The secondary pump 7 raises the DME fuel from the primary filter 6 to a secondary pressure (for example, 1.5 MP), and the secondary filter 8 filters the secondary pressure DME fuel. The DME fuel from the secondary filter 8 is stably held at the secondary pressure by the accumulator 9 and supplied to the fuel injection pump 3.

  In the fuel injection pump 3, the secondary pressure DME fuel is guided to the compression chamber 33 through the fuel supply passage 36. A driving force is transmitted from the cam mechanism through the tappet of the tappet chamber 34 to the plunger 31 whose upper end surface faces the compression chamber 33. As a result, the plunger 31 moves upward against the urging force of the spring 35 and pressurizes the DME fuel in the compression chamber 33 to increase the pressure to a predetermined injection pressure. The DME fuel at this injection pressure is discharged from a discharge passage formed in the upper part of the fuel injection pump 3 and supplied to the fuel injection device 4 through the fuel high-pressure pipe 103.

  The fuel injection device 4 guides the DME fuel having the injection pressure supplied from the fuel injection pump 3 to the nozzle 43 through the fuel passage 41. When the internal pressure at the tip of the nozzle 43 is increased by the DME fuel, the needle valve 45 moves toward the holder 42 against the urging force of the spring 47. As a result, the nozzle hole at the tip of the nozzle 43 is opened, and the DME fuel having the injection pressure is injected from the nozzle into the combustion chamber.

  In the fuel injection pump 3, of the DME fuel supplied to the compression chamber 33, DME fuel that is not supplied to the fuel injection device 4 flows into the fuel return pipe 11 through the fuel discharge passage 37. In the fuel return pipe 11, the pressure of the DME fuel is stably held at a pressure equal to or higher than the primary pressure by the pressure regulating valve 12 and the accumulator 13. The DME fuel that has reached a relatively high temperature by the fuel injection pump 3 is cooled by the cooler 14 of the fuel return pipe 11 and returned to the fuel main pipe 2 through the check valve 15. Thus, the DME fuel flowing into the fuel recirculation pipe 11 is stably maintained in a liquefied state at the primary pressure or higher by the pressure regulating valve 12, the accumulator 13 and the cooler 14, and returned to the fuel main pipe 2. In particular, by making the DME fuel in the fuel return pipe 11 slightly higher than the primary pressure by the pressure regulating valve 12 and the accumulator 13, the DME fuel in the fuel return pipe 11 is efficiently obtained by the pressure difference with respect to the fuel main pipe 2. The fuel main pipe 2 can be returned.

  The DME fuel in the fuel main pipe 2 is boosted to the secondary pressure by the secondary pump 7 on the downstream side of the joining position of the DME fuel from the fuel return pipe 11. In addition, the fuel main pipe 2 is provided with an accumulator 9. Accordingly, the DME fuel having a stable secondary pressure is supplied from the fuel main pipe 2 to the fuel injection pump 3 even though the DME fuel is returned to the upstream side of the fuel main pipe 2 by the fuel return pipe 11. The Therefore, the fuel injection pump 3 can stably supply the DME fuel having a predetermined amount of injection pressure to the fuel injection device 4.

  In the fuel injection pump 3, high-pressure, low-viscosity DME fuel leaks from the compression chamber 33 into a gap existing on the sliding surface between the plunger 31 and the plunger barrel 32 during the fuel compression operation. Since the high pressure lubricating oil of secondary pressure or higher is supplied to the groove 32a of the sliding surface facing the gap between the plunger 31 and the plunger barrel 32 through the oil supply passage 39, the high pressure DME fuel is supplied. Most of it is prevented from flowing into the tappet chamber 34 through the gap. The DME fuel leaking into the gap between the plunger 31 and the plunger barrel 32 flows into the plunger leak pipe 17 together with the lubricating oil through the oil drain passage 39 connected to the groove 32a. The DME fuel that has flowed into the plunger leak pipe 17 joins the DME fuel in the fuel recirculation pipe 11 via the check valve 18 and is returned to the fuel main pipe 2. As described above, the DME fuel leaking to the sliding surface of the plunger 31 is recovered to the fuel main pipe 2 while being maintained at a pressure higher than the primary pressure and prevented from being liquefied.

  On the sliding surface of the fuel injection pump 3, DME fuel that has not been recovered by the groove 32 a and the oil discharge passage 39 may flow into the tappet chamber 34. The leakage of DME fuel into the tappet chamber 34 occurs due to abnormal wear of the plunger 31 or the plunger barrel 32, for example. The DME fuel that has flowed into the tappet chamber 34 is guided to the oil leakage recovery tank 26 through the tappet leak pipe 25. When the DME fuel is guided to the oil leakage recovery tank 26, the leak detector 27 that detects the DME fuel is activated to give an alarm, for example. Thereby, the user is effectively notified of the leakage of DME fuel from the tappet chamber 34, so that it is possible to quickly cope with the abnormality.

  In addition, the DME fuel that has been boosted by the fuel injection pump 3 to an injection pressure usually does not leak from the fuel injection pump 3, but if the leak occurs for some reason, the leaked fuel is a high-pressure leak. It collects in the storage tank 21 via the pipe 20. When the DME fuel stored in the storage tank 21 exceeds a predetermined pressure, the leak detector 22 is activated by the pressure switch 23 to warn of a leak of the high pressure DME fuel. Thereby, the abnormality of the fuel injection pump 3 can be effectively detected by the user, and a quick response to the abnormality can be made.

  In the fuel injection device 4, the DME fuel leaking from the fuel passage 41 flows into the nozzle leak pipe 28 via the leak passage 49. The DME fuel in the nozzle leak pipe 28 flows into the fuel recirculation pipe 11 through the check valve 29 in a pressurized state and is returned to the fuel main pipe 2. As a result, the leaked fuel from the fuel injection device 4 is efficiently recovered in the liquefied state.

  When the diesel engine that receives the supply of DME fuel by the fuel system of the present embodiment stops, the fuel system removes the DME fuel in the fuel system as follows. First, the on / off valve 51 of the fuel main pipe 2 is closed, and the on / off valve 61 of the fuel recirculation pipe 11 is closed to disconnect the fuel injection pump 3 and the fuel injection device 4 from the DME tank 1. Further, the on-off valve 71 provided in the purge bypass pipe 70 of the fuel recirculation pipe 11 is opened. Subsequently, purge gas is supplied from the purge gas supply pipe 52 to the fuel main pipe 2, while the purge gas recovery pipe 60 is connected to, for example, a purge gas tank. The purge gas supplied to the fuel main pipe 2 is guided to the fuel injection pump 3 and flows into the fuel recirculation pipe 11 through the fuel supply passage 36, the compression chamber 33 and the fuel discharge passage 37 in the fuel injection pump 3. . In the fuel return pipe 11, the purge gas flows through the purge bypass pipe 70 and bypasses the pressure regulating valve 12. The purge gas replaces the DME fuel remaining in the fuel injection pump 3, drives it to the fuel recirculation pipe 11, and recovers it from the purge gas recovery pipe 60 to the purge gas tank. The residual DME fuel in the fuel injection pump 3 and the fuel recirculation pipe 11 is guided to the second residual gas discharge line 57 via the recirculation bypass pipe 73 and discharged from the second residual gas discharge line 57 to the atmosphere. May be.

  Further, the DME fuel leaking in the fuel injection pump 3 is difficult to be replaced with the purge gas passing through the fuel return pipe 11. Therefore, after introducing the purge gas to the fuel injection pump 3, the on-off valve 55 of the first residual gas discharge line 54 is opened, and the DME fuel is passed through the compression element of the fuel injection pump 3 and the plunger leak pipe 17. The gas is discharged from the first residual gas discharge line 54 to the atmosphere. Since the DME fuel released into the atmosphere is rendered harmless in tens of hours, it has little impact on the environment.

  Further, the DME fuel remaining in the fuel high-pressure pipe 103 and the fuel injection device 4 is difficult to be replaced by the purge gas that passes through the fuel recirculation pipe 11. Therefore, after introducing the purge gas to the fuel injection pump 3, the on-off valve 58 of the second residual gas discharge line 57 is opened, and the DME fuel is passed through the fuel high pressure pipe 103, the fuel injection device 4 and the nozzle leak pipe 28. The second residual gas discharge line 57 is then released to the atmosphere. In the fuel injection device 4, the DME fuel remaining in the leak passage 49 and the combustion chamber is released to the atmosphere via the combustion chamber communication pipe 63 by opening the on-off valve 65.

  In this way, since the DME fuel remaining in the fuel system is effectively discharged to the outside by the purge gas, a relatively large amount of remaining DME fuel is vaporized and leaks from the fuel system, causing a fire. And the inconvenience of giving to the surrounding environment can be effectively prevented. Further, initialization for restarting the diesel engine can be performed.

  As described above, according to the fuel system of the present embodiment, the leak DME fuel generated in the fuel injection pump 3 can be effectively returned to the fuel main pipe 2 while being in a liquefied state. Diesel engine output can be stabilized while preventing reduction. Therefore, the electric power generated by the generator driven by this diesel engine can be stabilized. Further, with respect to leaks occurring in the fuel injection device 4, the DME fuel can be returned to the fuel main pipe 2 in a liquefied state. Further, since the DME fuel leaked from the fuel injection pump 3 and the fuel injection device 4 can be prevented from leaking in large quantities to the outside of the fuel system, the leaked DME even if a spark is generated in the generator driven by the diesel engine. The risk of igniting the fuel can be effectively prevented, and there is almost no influence on the surrounding environment. As described above, the fuel system of this embodiment is a fuel system that is suitable for a diesel engine for a generator because it can stabilize the output of the diesel engine and can effectively prevent fuel leakage. .

  In the above embodiment, DME is used as the fuel to be supplied to the diesel engine. However, other fuels may be used as long as they are vaporized at normal temperature and atmospheric pressure, and fuel other than DME such as butane and propane is used. You can also.

It is the schematic which shows the fuel system | strain system as embodiment of this invention. It is sectional drawing which shows a fuel injection pump. It is sectional drawing which shows a fuel-injection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DME tank 2 Fuel main pipe 3 Fuel injection pump 4 Fuel injection apparatus 5 Primary pump 6 Primary filter 7 Secondary pump 8 Secondary filter 9 Accumulator 11 Fuel return pipe 12 Pressure regulation valve 13 Accumulator 14 Cooler 15 Check valve 17 Plunger leak Pipe 18 Check valve 20 High pressure leak pipe 21 Storage tank 25 Tappet leak pipe 26 Oil leak recovery tank 28 Nozzle leak pipe 29 Check valve 52 Purge gas supply pipe 54 First residual gas discharge line 57 Second residual gas discharge line 60 Purge gas recovery Pipe 63 Combustion chamber communication pipe 70 Purge bypass pipe 73 Reflux bypass pipe 103 Fuel high pressure pipe 105 Storage tank discharge pipe 107 Oil leakage tank discharge pipe

Claims (6)

A fuel tank for storing fuel that vaporizes at room temperature and atmospheric pressure;
A primary pressure increasing unit for increasing the pressure of the fuel supplied from the fuel tank to a primary pressure;
A secondary booster connected to the downstream side of the primary booster and boosting the pressure of the fuel from the primary booster to a secondary pressure;
A fuel injection pump connected to the downstream side of the secondary booster and boosting the pressure of the fuel from the secondary booster to an injection pressure;
A fuel injection device to which fuel at the injection pressure is supplied from the fuel injection pump;
A first return pipe for returning the fuel leaked from the fuel injection pump between the primary booster and the secondary booster in a state where the leaked fuel has a pressure higher than the primary pressure; A fuel system characterized by that. The fuel system according to claim 1, wherein
A fuel system comprising a lubricating oil supply section that supplies lubricating oil having a pressure equal to or higher than the secondary pressure to the fuel injection pump. The fuel system according to claim 1, wherein
A fuel system comprising a second return pipe for returning the fuel leaked from the fuel injection device between the primary booster and the secondary booster. The fuel system according to claim 1, wherein
A first leak detection pipe connected to a fuel high-pressure pipe through which fuel of an injection pressure discharged from the fuel injection pump flows,
A first leak detector for detecting the flow of fuel in the first leak detector;
A leak fuel storage tank for storing fuel from the first leak detection pipe;
A first discharge pipe for releasing the fuel in the fuel storage tank to the atmosphere;
A second leak detection pipe for flowing a leaked fuel at a connecting portion between the fuel injection pump and a drive mechanism for applying a driving force to the fuel injection pump;
A second leak detector for detecting the flow of fuel in the second leak detector tube;
A leaked oil recovery tank for storing fuel from the second leak detection pipe;
A fuel system comprising: a second discharge pipe for releasing the fuel in the oil leakage recovery tank to the atmosphere. The fuel system according to claim 1,
The first return pipe includes a surplus recovery pipe that returns surplus fuel that has not been supplied from the fuel injection pump to the fuel injection device, and a compression element leak pipe that returns leaked fuel in the compression element of the fuel injection pump.
A purge supply pipe that is provided downstream of the fuel injection pump and supplies a purge fluid to be replaced with fuel;
A purge recovery pipe provided in an excess recovery pipe of the first return pipe for recovering the fuel replaced with the purge fluid;
A first residual fuel discharge pipe that is provided in the compression element leak pipe of the first return pipe and discharges leaked fuel remaining in the compression element of the fuel injection pump;
A fuel system comprising: a second residual fuel discharge pipe that is provided in the second return pipe and discharges leaked fuel remaining in the fuel injection device. The fuel system according to claim 1, wherein
The fuel system, wherein the fuel includes DME.

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