JP2009156093A - Aspirator for recovering fuel source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a structure for further improving an aspirating force in an aspirator for recovering fuel. <P>SOLUTION: This aspirator 30 for recovering fuel has a structure for aspirating residual fuel in an engine fuel passage through an aspiration passage 34 communicated with a drive passage 31 by flowing fuel in the drive passage 31, in which a bottle neck is formed, to generate a negative pressure. Heat-insulation layers 35, 36 are formed around the drive passage 31. By the heat-insulation layers, it becomes difficult to transmit an outside temperature to the drive passage. Meanwhile, it becomes difficult to release temperature fall due to vaporization of the fuel in the drive passage to outside, so that the temperature of the drive passage can be restrained and the vaporization of the fuel flowing as drive fluid can be restrained than conventional, so as to improve an aspirating force. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aspirator used for recovering residual fuel in a liquefied gas engine using liquefied gas such as DME (dimethyl ether) as a fuel.

  In a liquefied gas engine that uses liquefied gas as fuel, the fuel pumped from a fuel tank that stores liquefied gas is boosted by a jerk-type high-pressure pump (injection pump) and then directly injected from the injector into each cylinder. Like to do. In this liquefied gas engine, it is known that the fuel remaining in the injection system after the engine stops leaks into the combustion chamber and vaporizes, and then abnormal combustion can be induced when the engine is started next time.

Therefore, as disclosed in Patent Document 1, an aspirator is used as a suction means for collecting the residual fuel remaining in the engine fuel path such as a pump and a pipe into the fuel tank when the engine is stopped (no combustion). It has been proposed. The aspirator uses the fuel pumped by the feed pump as a driving fluid to flow through a driving passage (passage from the nozzle to the diffuser) that forms a bottleneck to generate a negative pressure, and the negative pressure communicates with the driving passage. This is a structure for sucking the residual fuel in the engine fuel path through the suction passage.
JP 2003-262167 A

  As described above, in the aspirator used for fuel recovery of the liquefied gas engine, the fuel that is the driving fluid is vaporized in the driving passage, and it is not possible to obtain the suction force when water is made to flow as the driving fluid. Has a defect. This is due to the low boiling point temperature of the fuel, and is unavoidable as long as liquefied gas is used as the fuel.

  The present invention pays attention to this point, and proposes a structure capable of further improving the suction force of an aspirator for fuel recovery.

  The fuel recovery aspirator proposed in the present invention sucks the residual fuel in the engine fuel path through the suction passage communicating with the drive passage by causing the fuel to flow through the drive passage that forms the bottleneck and generating negative pressure. It has a structure, and a heat insulating layer is formed in a wall around the drive passage.

  In the aspirator according to the above proposal, the formation of the heat insulating layer makes it difficult for the outside air temperature to be transmitted to the drive passage, while the temperature drop due to fuel vaporization in the drive passage is difficult to escape to the outside. Can be suppressed. By suppressing the temperature, vaporization of the fuel flowing as the driving fluid is suppressed as compared with the conventional case, so that the suction force is improved and more residual fuel can be recovered.

  FIG. 1 shows an example of a fuel system of a liquefied gas engine to which a fuel recovery aspirator is applied.

  Dimethyl ether (DME) as liquefied gas, which is fuel stored in the fuel tank 1, is pressurized and sent out by the feed pump 2, and is supplied to the high-pressure pump 5 through the fuel temperature control unit 3 and the filter 4. The fuel supplied to the high-pressure pump 5 is pressure-fed to the injectors of the respective cylinders with timing. The high-pressure pump 5 includes a pump element 5a (for example, refer to Patent Document 1) for each cylinder that boosts the fuel with a plunger, and the fuel is pumped from each pump element 5a to each injector. Fuel is supplied to the pump element 5 a through the feed passage 6, and the overflowed fuel passes through the return passage 7 and returns to the fuel tank 1 through the fuel temperature control unit 3. Further, the fuel that overflows in the injector is also returned to the fuel tank 1 through the return passage 7.

  In the high-pressure pump 5, a cam for driving the plunger of each pump element 5a is accommodated in the cam chamber 5b, and a governor chamber 5c for cam speed control is provided adjacent to the cam chamber 5b. The governor chamber 5c is provided with a discharge port for discharging fuel leaked from the pump element 5a, and the leaked fuel is sucked into the reliquefaction pump 8 from this discharge port. A reliquefaction pump 8 that pressurizes and reliquefies the leaked fuel is provided on the outer surface of the cam chamber 5b. That is, a cylinder projects from the outer surface of the cam chamber 5b, and a piston that follows the cam of the cam chamber 5b slides inside the cylinder. As the piston moves, leaked fuel is sucked and pressurized to be reliquefied. The reliquefied fuel is returned to the fuel tank 1 through the return passage 7.

  In this way, the fuel pumped from the fuel tank 1 by the feed pump 2 is supplied to the cylinder through the feed passage 6 and the high-pressure pump 5, and the overflowed fuel is returned to the fuel tank 1 through the return passage 7. Thus, an engine fuel path is configured. A gas phase introduction line 10 and a liquid phase suction line 20 are provided in order to collect residual fuel remaining when the engine is stopped in the engine fuel path. In addition, an electromagnetic valve and a check valve are provided at the key points of the engine fuel path so that passage conduction can be controlled as necessary.

  The gas phase introduction line 10 is provided to feed the high pressure gas phase in the fuel tank 1 into the feed passage 7 and push out the residual fuel. When the engine is stopped, the electromagnetic valve 11 is opened to introduce the gas phase into the feed passage 7. To do. One liquid phase suction line 20 is provided to recover the residual fuel pushed out by the gas phase introduction and return it to the fuel tank 1, and the electromagnetic valve 21 is opened when the gas phase introduction line 10 is opened. An aspirator 30 for fuel recovery is disposed at the tip of the liquid phase suction line 20.

  In the aspirator 30 shown in detail in FIG. 2, the drive passage 31 is disposed in the reflux passage 40 branched from the feed passage of the feed pump 2. When the engine is stopped, the fuel valve FV of the feed passage 7 is closed and the electromagnetic valve 41 of the return passage 40 is opened, so that the fuel in the fuel tank 1 is pumped back from the return passage 40 to the fuel tank 1 by the operation of the feed pump 2. This fuel passes through the drive passage 31 as a drive fluid.

  The drive passage 31 is formed with a bottleneck composed of a nozzle 32 and a diffuser 33, and negative pressure is generated when fuel passes through the drive passage 31. Since the suction passage 34 connected to the liquid phase suction line 20 communicates with the bottleneck portion of the drive passage 31, when fuel flows into the drive passage 31 and negative pressure is generated, the liquid phase suction line 20 passes through the suction passage 34. Residual fuel is sucked from. In other words, pressure is applied by gas phase introduction of the gas phase introduction line 10 to send out residual fuel from the engine fuel path, and residual fuel is sucked from the engine fuel path by suction by the aspirator 30 through the liquid phase suction line 20. It has become.

  The residual fuel sucked through the suction passage 34 is mixed with the fuel flowing through the drive passage 31 as a drive fluid and returned to the fuel tank 1.

  As shown in the cross-sectional view of FIG. 2, heat insulation layers 35 and 36 are formed in a wall forming the drive passage 31 in the aspirator 30 so as to surround the drive passage 31. The heat insulating layers 35 and 36 in this example are cavities formed in the wall, and are formed in the wall by casting a main body portion of the aspirator 30, for example. Further, the two heat insulating layers 35 and 36 in this example are in communication with each other so that cold air can be fed through the opening 37.

  The heat insulating layers 35 and 36 can be independent from each other, or can be a sealed cavity without providing the opening 37, but it is preferable that the heat-insulating layers 35 and 36 communicate with each other so that cold air can be fed. , The heat insulation effect can be enhanced. In addition, the heat insulating layers 35 and 36 may have a structure in which a heat insulating material is embedded in a wall instead of a hollow, but it can be said that a hollow is suitable in terms of cost performance.

  The cool air blown from the opening 37 may be guided from the fuel temperature control unit 3 shown in FIG. Since the fuel temperature control unit 3 is a cooler that performs cooling with a refrigerant, it can be used by guiding the cold air to the opening 37 with a pipe or the like.

  The aspirator 30 having this structure is such that the outside temperature is hardly transmitted to the drive passage 31 by surrounding the drive passage 31 with the heat insulating layers 35 and 36. On the other hand, since the temperature drop due to the vaporization of the fuel in the drive passage 31 is blocked by the heat insulating layers 35 and 36, it becomes difficult to escape to the outside, so that the temperature rise of the drive passage 31 is suppressed (that is, cooled). In particular, when cool air is blown to the heat insulating layers 35 and 36, the cooling effect by the cool air is also added. By suppressing the temperature, vaporization of the fuel flowing as the driving fluid is suppressed as compared with the conventional case, so that the suction force through the suction passage 34 is improved and more residual fuel can be recovered.

Schematic explaining the fuel path | route of a liquefied gas engine. Sectional drawing of the aspirator which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Feed pump 3 Fuel temperature control unit 5 High pressure pump 6 Feed passage 7 Return passage 8 Reliquefaction pump 10 Gas phase introduction line 20 Liquid phase suction line 30 Aspirator 31 Drive passage 34 Suction passage 35, 36 Heat insulation layer 37 Opening 40 Reflux passage

Claims (3)

In a fuel recovery aspirator that sucks residual fuel in an engine fuel path through a suction path communicating with the drive path by causing fuel to flow through a drive path that forms a bottleneck,
An aspirator, wherein a heat insulating layer is formed in a wall around the drive passage.   The aspirator according to claim 1, wherein the heat insulating layer is a cavity formed so as to surround the drive passage.   The aspirator according to claim 2, wherein cool air is blown into the heat insulating layer.

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