JP5259514B2 - How to start the DME engine - Google Patents

Description

  The present invention relates to a method for starting a DME engine in a fuel supply system including a fuel circuit that supplies DME fuel in a fuel tank to a DME engine via a supply line by a feed pump.

  A fuel supply system that supplies DME (dimethyl ether) fuel to a DME engine is known. The fuel supply system includes a fuel circuit that supplies DME fuel in a fuel tank to a DME engine via a supply line by a feed pump. The fuel circuit is configured to circulate the fuel, and the fuel supplied to the engine is returned to the fuel tank or the supply line.

  Conventionally, the DME engine is started in the fuel supply system as follows. First, the feed pump is activated. Thereby, the circulation of the fuel in the fuel circuit is started. Next, it is confirmed whether or not the pressure in the supply line has reached a predetermined pressure. When the pressure does not reach the predetermined pressure, the supply line is purged manually, for example. Thereafter, the engine is started.

  Patent Document 1 discloses an example of a method for starting a DME engine. The fuel supply device of Patent Document 1 includes a plurality of feed pumps between a fuel tank and an engine. In Patent Document 1, before starting the engine, the pressure of each feed pump is controlled to reach the target pressure. The target pressure is a value that is equal to or higher than the saturated vapor pressure of DME, and that DME must be liquid. The target pressure is specified based on a graph showing the relationship between the temperature of the DME and the vapor pressure. For this reason, the control device of Patent Document 1 detects the temperature of the DME and the pressure on the inlet side of each feed pump, and sets the output of each feed pump so that the pressure is equal to or higher than the vapor pressure corresponding to the temperature. To do. As a result, bubbles (DME vapor) are prevented from being mixed into the DME supplied by each feed pump. When all the feed pump pressures reach the target pressure, the control device starts the engine.

JP 2005-98260 A

  During engine shutdown, DME is purged from the engine fuel injection pump and / or DME is leaked from the fuel circuit. As a result, air enters the fuel circuit instead of the DME exiting from the fuel circuit.

  When the engine is started, the feed pump is started. At this time, the air in the fuel circuit causes cavitation by the feed pump. Cavitation prevents the feed pump from being driven. As a result, the pressure of DME does not rise correctly. That is, the presence of air in the fuel circuit hinders engine startup. On the other hand, even if the technique of Patent Document 1 can prevent the vaporization of DME due to the temperature rise, it cannot remove the air that has entered the fuel circuit.

  Therefore, the present invention provides a DME engine starting method that not only prevents DME vaporization but also removes air entering the fuel circuit before starting the DME engine.

  A first invention is a method for starting a DME engine in a fuel supply system including a fuel circuit that supplies DME fuel in a fuel tank to a DME engine via a supply line by a feed pump, and includes at least the fuel circuit. Starting a fuel cooler for cooling the fuel in part, a cooler starting step, opening the supply line, a line opening step, a pump starting step for starting the feed pump after the line opening step, and After the pump activation process, the supply line is opened to the atmosphere until the pressure difference between the outlet side and the inlet side of the feed pump is equal to or greater than a predetermined pressure difference and the pressure on the outlet side of the feed pump is equal to or greater than a predetermined pressure. The temperature of the fuel at a predetermined position in the fuel circuit after the purge step and the cooler start-up step. There waits until less than a predetermined temperature, and temperature lowering standby step, after completion of the purging step and the temperature lowering standby step, starts the starter of the DME engine includes a starter starting step.

  Preferably, the first invention can employ configurations (a) to (c).

(A) Each said process is performed in order of a cooler starting process, a line open process, a pump starting process, the said purge process, the said temperature fall standby process, and the said starter starting process.

(B) In the purge step, the pressure on the outlet side of the feed pump is detected at a position close to the feed pump and a position close to the DME engine, and a pressure for comparison with the predetermined pressure difference The difference is the pressure difference between the pressure on the inlet side of the feed pump and the pressure near the feed pump, and the pressure for comparison with the predetermined pressure is the pressure near the DME engine.

(C) The fuel circuit includes a return line for returning the fuel from the DME engine to the fuel tank, and the fuel circulates between the DME engine and the fuel tank.

  The present invention not only prevents DME vaporization but also removes air entering the fuel circuit before starting the DME engine.

It is the schematic which shows a fuel supply system. It is a flowchart which shows the starting method of a DME engine.

  FIG. 1 is a schematic diagram illustrating a fuel supply system and a DME supply source 100. The fuel supply system is a system that supplies DME fuel to the engine 2. The DME supply source 100 supplies DME fuel to the fuel tank 3 of the fuel supply system.

  The fuel supply system includes a fuel circuit 1 for supplying fuel. The fuel circuit 1 includes an engine 2, a fuel tank 3, and a high pressure pump 4.

  The fuel circuit 1 includes a supply line 10 that supplies fuel from the fuel tank 3 to the engine 2, a return line 20 that returns fuel from the engine 2 to the fuel tank 3, and a bypass line that connects the supply line 10 and the return line 20 to each other. 30. The supply line includes a first sub supply line 11, a second sub supply line 12, a third sub supply line 13, and a fourth sub supply line 14. The return line includes a first sub return line 21, a second sub return line 22, a third sub return line 23, and a fourth sub return line 24. The bypass line 30 includes a first sub bypass line 31 and a second sub bypass line 32.

  The fuel circuit 1 further includes three purge lines 71, 72, and 73 and a leak line 80. The first purge line 71, the second purge line 72, and the third purge line 73 are lines for releasing the gas in the fuel circuit 1 into the atmosphere. The first purge line 71 is open to the atmosphere. The second purge line 72 joins the downstream portion of the first purge line 71 at the joining portion 1c. The third purge line 73 joins the downstream portion of the second purge line 72 at the joining portion 1d. The leak line 80 is a line for collecting the fuel leaked from each part in the fuel circuit 1 in the fuel tank 3.

  The high-pressure pump (feed pump) 4 is disposed between the first sub supply line 11 and the second sub supply line 12. The engine 2 is disposed between the fourth sub supply line 14 and the first sub return line 21. The fuel tank 3 is disposed between the fourth sub return line 24 and the first sub supply line 11.

  The branch part 1 a is a connection part between the supply line 10 and the bypass line 30. The second sub supply line 12 branches into a third sub supply line 13 and a first sub bypass line 31 in the branching section 1a. The junction 1 b is a connection between the return line 20 and the bypass line 30. The second sub bypass line 32 and the third sub return line 23 merge with the fourth sub return line 24 at the junction 1b.

  The fuel circuit 1 includes two electromagnetic valves CV-1 and CV-2. The first electromagnetic valve CV-1 is disposed between the third sub supply line 13 and the fourth sub supply line 14. The second solenoid valve CV-2 is disposed between the first sub return line 21 and the second sub return line 22.

  The fuel circuit 1 includes two pressure regulating valves 41 and 42. The first pressure regulating valve 41 is disposed between the first sub bypass line 21 and the second sub bypass line 32. The second pressure regulating valve 42 is disposed between the second sub return line 22 and the third sub return line 23. The two pressure regulating valves 41 and 42 are provided to keep the pressure of the fuel supplied to the engine 2 constant. The pressure from the high pressure pump 4 to the upstream side of the two pressure regulating valves 41 and 42 is kept high. The pressure from the downstream side of the two pressure regulating valves 41 and 42 to the high pressure pump 4 is low. In this embodiment, the high pressure is 1.6 MPa and the low pressure is 0.6 MPa.

  The fuel circuit 1 includes two check valves 43 and 44. The check valve 43 is disposed between the fourth sub return line 24 and the fuel tank 3. The check valve 44 is disposed between the leak line 80 and the fuel tank 3. The check valves 43 and 44 prevent fuel from flowing back from the fuel tank 3 to the lines 24 and 80.

  The fuel circuit 1 includes two solenoid valves RV-1, RV-2 and two shutoff valves 91, 92 for purging. The first solenoid valve RV-1 is disposed on the second purge line 72 between the junction 1c and the junction 1d. The second solenoid valve RV-2 is disposed on the first purge line 71 on the upstream side of the junction 1c. The first shut-off valve 91 is disposed between the fourth sub supply line 14 and the second purge line 72. The second shut-off valve 92 is disposed between the first sub return line 21 and the third purge line 73.

  When the first electromagnetic valve RV-1 and the first shutoff valve 91 are opened, the gas in the fourth sub supply line 14 is released to the atmosphere via the second purge line 72. When the first electromagnetic valve RV-1 and the second shut-off valve 92 are opened, the gas in the first sub return line 21 is released to the atmosphere via the third purge line 73. When the second electromagnetic valve RV-2 is opened, the gas in the fuel tank 3 is released into the atmosphere via the first purge line 71.

  The fuel supply system includes six pressure sensors PS-2, PS-3, PS-4, PS-5, PS-6, and PS-7 that detect the pressure of the fuel in each part of the fuel circuit 1. . The second pressure sensor PS-2 detects the pressure of the fuel in the first sub supply line 11. Here, the pressure of the fuel in the first sub supply line 11 is equal to the pressure of the fuel in the fuel tank 3. The third pressure sensor PS-3 detects the pressure of the fuel in the second upstream supply line 12. The fourth pressure sensor PS-4 detects the pressure of the fuel in the fourth sub supply line 14. The fifth pressure sensor PS-5 detects the fuel pressure in the second sub return line 22. The sixth pressure sensor PS-6 detects the fuel pressure in the fourth sub return line 24. The seventh pressure sensor PS-7 detects the pressure of the fuel in the leak line 80.

  The fuel supply system includes two fuel coolers 51 and 52 for cooling the fuel in the fuel circuit 1. The fuel coolers 51 and 52 are chillers (devices for cooling the refrigerant). The first fuel cooler 51 cools the fuel in the supply line 10. The heat exchanger 51 a of the first fuel cooler 51 is disposed in the second sub supply line 12. The second fuel cooler 52 cools the fuel in the return line 20. The heat exchanger 52 a of the second fuel cooler 52 is disposed in the fourth sub return line 24.

  The fuel supply system includes eight temperature sensors 61 to 68 that detect the temperature of the fuel in each part of the fuel circuit 1. The first temperature sensor 61 detects the temperature of the fuel in the first sub supply line 11. The second temperature sensor 62 and the third temperature sensor 63 detect the temperature of the fuel on the upstream side and the downstream side of the first heat exchanger 51 in the second sub supply line 12. The fourth temperature sensor 64 detects the temperature of the fuel at the end of the supply line 10, that is, at the inlet of the engine 2. The fifth temperature sensor 65 detects the temperature of the fuel at the start end of the return line 20, that is, at the outlet of the engine 2. The sixth temperature sensor 66 and the seventh temperature sensor 67 detect the temperature of the fuel on the upstream side and the downstream side of the second heat exchanger 52 in the fourth sub return line 24. The eighth temperature sensor 68 detects the temperature of the fuel in the leak line 80.

  The fuel supply system includes a control device 6. The control device 6 can control driving of the engine 2, the high-pressure pump 4, and the fuel coolers 51 and 52. The control device 6 can maintain or change the opening degree of the two electromagnetic valves CV-1 and CV-2. The control device 6 can confirm detection information by the six pressure sensors PS-2 to PS-7 and the eight temperature sensors 61 to 68.

  A rough operation during driving of the fuel supply system will be described. In the fuel supply system, the fuel in the fuel tank 3 is supplied to the engine 2 through the supply line 10 by the operation of the high-pressure pump 4. The fuel supplied to the engine 2 passes through the engine 2 and then returns to the fuel tank 3 through the return line 20. Further, part of the fuel supplied to the supply line 10 is returned to the fuel tank 3 through the bypass line 30 and the return line 20 without passing through the engine 2. The fuel is cooled by the first fuel cooler 51 in the supply line 10 and is cooled by the second fuel cooler 52 in the return line 20. Due to the presence of the bypass line 30, the flow rate of the fuel passing through the fuel coolers 51 and 52 is increased. For this reason, the fuel is easily cooled.

  With reference to FIG. 2, the starting method of the engine 2 in a fuel supply system is demonstrated. FIG. 2 is a flowchart showing a method for starting the DME engine 2. The control device 6 executes engine start control according to the flow of FIG. The engine start control includes the following steps.

  In the stop state of the engine 2, that is, when the engine start control is started, the four solenoid valves CV-1, CV-2, RV-1, and RV-2 and the two shut-off valves 91 and 92 are all closed. It has been. Further, the driving of the engine 2, the high-pressure pump 4, and the two fuel coolers 51 and 52 are also stopped.

  The fuel supply system includes a start switch for starting the engine 2. In step S1, when detecting that the start switch has been pressed, the control device 6 starts engine start control.

  In step S2, the control device 6 activates the two fuel coolers 51 and 52. The process of step S2 is a cooler starting process.

  In step S3, the control device 6 opens the two solenoid valves CV-1 and CV-2. As a result, the fuel can flow through the supply line 10 and the return line 20. The process of step S3 is a line opening process.

  In step S4, the control device 6 activates the high-pressure pump (feed pump) 4. As a result, fuel begins to flow in the fuel circuit 1. The process of step S4 is a feed pump starting process.

  In step S5, the control device 6 waits for execution of the next step S6 for a predetermined first waiting time. The first waiting time is set to a time until the high-pressure pump 4 reaches steady rotation, for example. In the present embodiment, the first waiting time is 5 seconds.

  The processing from step S6 to step S12 is a purge process for performing a purge of gas. The process in the purge process is a loop process in which steps S6 to S12 are repeatedly executed under a predetermined condition. This loop processing ends when the determination results in steps S6 and S7 are both Yes. When any determination result in step S6 or S7 is No, the loop process is repeatedly executed.

  In step S6, the control device 6 determines whether or not the pressure difference between the outlet side and the inlet side of the high-pressure pump 4 is equal to or greater than a predetermined pressure difference. The control device 6 can grasp the pressure on the inlet side of the high-pressure pump 4 based on the detection information by the second pressure sensor PS-2. The control device 6 can grasp the pressure on the outlet side of the high-pressure pump 4 based on the detection information by the third pressure sensor PS-3. This pressure difference is obtained by subtracting the inlet side pressure from the outlet side pressure. Therefore, the control device 6 can grasp the pressure difference between the outlet side and the inlet side of the high-pressure pump 4. The predetermined pressure difference is set as an index for knowing the operating state of the high-pressure pump 4. That is, when the pressure difference in the high-pressure pump 4 exceeds the predetermined pressure difference, the high-pressure pump 4 is operating properly. The predetermined pressure difference is 0.3 MPa in the present embodiment.

  When the pressure difference in the high-pressure pump 4 is greater than or equal to the predetermined pressure difference (0.3 MPa), the control device 6 shifts the process to step S7. When the pressure difference in the high-pressure pump 4 is less than the predetermined pressure difference, the control device 6 shifts the process to step S8.

  In step S7, the control device 6 determines whether or not the pressure on the outlet side of the high-pressure pump 4 is equal to or higher than a predetermined pressure. The control device 6 can grasp the pressure on the outlet side of the high-pressure pump 4 based on the detection information by the fourth pressure sensor PS-4. The predetermined pressure is set as an index for knowing the pressure of the fuel supplied to the engine 2. That is, when the pressure on the outlet side of the high pressure pump 4 exceeds a predetermined pressure, the pressure of the fuel supplied to the engine 2 is appropriate. The predetermined pressure is 1.5 MPa in the present embodiment. The pressure on the outlet side in step S7 is preferably a pressure close to the engine 2. For this reason, in step S7, the detection value of the fourth pressure sensor PS-4 is used instead of the detection value of the second pressure sensor PS-2 used in step S6.

  When the pressure on the outlet side is equal to or higher than the predetermined pressure (1.5 MPa), the control device 6 shifts the process to step S13. That is, the control device 6 ends the loop processing from step S6 to S12. When the pressure on the outlet side is less than the predetermined pressure, the control device 6 shifts the process to step S8.

  In step S8, the control device 6 opens the first electromagnetic valve RV-1 and the shut-off valves 91 and 92. As a result, the gas (air and DME vapor) in the supply line 10 and the return line 20 is purged into the atmosphere.

  In step S9, the control device 6 waits for execution of the next step S10 for a predetermined second waiting time. The second standby time is set as the air bleeding time. The second waiting time is 1 second in the present embodiment. During the second waiting time, a gas purge is performed.

  In step S10, the control device 6 closes the first electromagnetic valve RV-1 and the shut-off valves 91 and 92. As a result, the purge of gas is completed.

  In step S11, the control device 6 waits for execution of the next step S10 for a predetermined third standby time. The third standby time is set as the time required for the fuel in the fuel circuit 1 to stabilize after the purge is executed. The third waiting time is 40 seconds in this embodiment.

  In step S12, the control device 6 determines whether or not the pressure on the outlet side of the high-pressure pump 4 has continuously exceeded the predetermined pressure for a predetermined first duration time. The first duration time is set as an index for knowing the degree of stability of driving of the high-pressure pump 4. The first duration is 40 seconds in this embodiment.

  When the detected value of the fourth pressure sensor PS-4 continuously exceeds 1.5 MPa for the first duration (40 seconds), the control device 6 shifts the processing to step S6. On the other hand, if the detected value of the fourth pressure sensor PS-4 cannot continuously exceed 1.5 MPa during the first duration time, the control device 6 determines that an error has occurred and starts the engine. End control.

  The processing from step S13 to S15 is a temperature decrease standby process for waiting until the fuel cools. The process in the temperature decrease standby process is a loop process in which steps S13 to S15 are repeatedly executed under a predetermined condition. This loop processing ends when the determination result in step S13 is Yes. If the determination result in step S13 is No, the loop process is repeatedly executed.

  In step S13, the control device 6 determines whether or not the temperature of the fuel at the inlet of the engine 2 is lower than a predetermined temperature. The control device 6 can grasp the temperature of the fuel at the inlet of the engine 2 based on information detected by the fourth temperature sensor 64. The predetermined temperature is set as an index for knowing the operating state of the fuel coolers 51 and 52. The predetermined temperature is 30 ° C. in the present embodiment.

  When the temperature at the inlet of the engine is lower than the predetermined temperature (30 ° C.), the control device 6 shifts the process to step S16. When the temperature at the inlet of the engine is equal to or higher than the predetermined temperature, the control device 6 shifts the process to step S14.

  In step S14, the control device 6 waits for execution of the next step S15 for a predetermined fourth waiting time. The fourth standby time is set as a time sufficient for the temperature of the fuel to become lower than the predetermined temperature when the fuel coolers 51 and 52 are operating normally. The fourth waiting time is 3 minutes in this embodiment.

  In step S15, the control device 6 determines whether or not the temperature of the fuel is continuously lower than the predetermined temperature for a predetermined second duration. The second duration time is set as an index for knowing the degree of stability of driving of the fuel coolers 51 and 52. In the present embodiment, the second duration is 5 minutes.

  When the detected value of the fourth temperature sensor 64 is continuously lower than 30 ° C. during the second duration (5 minutes), the control device 6 shifts the process to step S13. On the other hand, if the detected value of the fourth temperature sensor 64 does not continuously become less than 30 ° C. during the second duration time, the control device 6 determines that an error has occurred and ends the engine start control.

  In step S <b> 16, the control device 6 starts the starter of the engine 2. That is, the engine 2 is activated.

  Next, in step S17, the control device 6 ends the engine activation control.

  This embodiment has the following operations and effects. While the pressure difference between the outlet side and the inlet side of the high pressure pump 4 is smaller than the predetermined pressure difference and / or while the pressure at the inlet of the engine 2 is lower than the predetermined pressure, the engine is not started and the gas (air And DME vapor). For this reason, this embodiment can remove the air that has entered the fuel circuit 1 before starting the engine 2. Therefore, this embodiment can avoid the malfunction that the high-pressure pump 4 does not operate correctly due to the entry of air into the fuel circuit 1.

  Further, the engine 2 is not started while the temperature at the inlet of the engine 2 is higher than the predetermined temperature. For this reason, this embodiment can prevent vaporization of DME fuel before starting the engine 2. Therefore, this embodiment can avoid the trouble that the high pressure pump 4 does not operate correctly and the trouble that the engine 2 does not start up properly due to the DME vapor in the fuel circuit 1.

  The present invention can employ the following modifications.

  In this embodiment, each process in the engine start control includes (1) a cooler start process, (2) a line open process, (3) a pump start process, (4) a purge process, (5) a temperature decrease standby process, and ( 6) It is executed in the order of the starter starting process. Here, the execution order of each process should just satisfy | fill the following conditions. The (2) line opening process, (3) pump activation process, and (5) purge process need to be executed in the order of (2), (3), and (4). The (1) cooler start-up process and (5) temperature decrease standby process need to be executed in the order of (1) and (5). However, the order of execution of the process groups (2), (3), and (4) and the process groups (1) and (5) is not limited. For example, the (1) cooler starting process may be performed after the (3) pump starting process. Alternatively, (4) the purge step and (5) the temperature decrease standby step may be performed in parallel so that the execution times overlap.

  In the present embodiment, the pressure on the outlet side of the high pressure pump 4 is detected at a position close to the high pressure pump 4 and a position close to the engine 2. The third pressure sensor PS-3 is a position relatively close to the high-pressure pump 4, and the fourth pressure sensor PS-4 is relatively close to the engine 2. In the purge process (step S5), the pressure difference for comparison with the predetermined pressure difference is the pressure difference between the pressure on the inlet side of the high pressure pump 4 and the pressure close to the high pressure pump 4. Similarly, in the purge process (step S6), the pressure for comparison with the predetermined pressure is a pressure close to the engine 2. The pressure on the outlet side of the high-pressure pump 4 may be detected at the same position instead of the two different positions as described above.

  In the present embodiment, the temperature near the engine 2 is used as the temperature of the fuel in the fuel circuit 1 for comparison with the predetermined temperature in the temperature decrease standby step (step S7). The fourth temperature sensor 64 detects the temperature near the engine 2. The temperature of the fuel for comparison with the predetermined temperature may be a temperature at a predetermined position in the fuel circuit 1 and is not limited to a temperature close to the engine 2.

  In the present embodiment, the fuel circuit 1 includes a supply line 10, a return line 20, and a bypass line 30. For this reason, some fuel circulates through the engine 2 and the fuel tank 3, and other fuel circulates through the fuel tank 3 without passing through the engine 2. The fuel circuit 1 is not limited to this configuration. The fuel circuit may be configured without the bypass line 30. In the fuel circuit, the return line from the engine 2 may join in the middle of the supply line 10 instead of the fuel tank 3.

1 Fuel circuit 2 DME engine 3 Fuel tank 4 High-pressure pump (feed pump)
DESCRIPTION OF SYMBOLS 10 Supply line 20 Return line 51 1st fuel cooler 52 2nd fuel cooler 64 4th temperature sensor (sensor which detects the temperature of the position near an engine)
71 1st purge line 72 2nd purge line 73 3rd purge line 80 Leak line PS-2 2nd pressure sensor (sensor which detects the pressure of the inlet side of a feed pump)
PS-3 Third pressure sensor (sensor that detects the pressure near the feed pump on the outlet side of the feed pump)
PS-4 Fourth pressure sensor (sensor that detects the pressure near the engine on the outlet side of the feed pump)

Claims (4)

A method for starting a DME engine in a fuel supply system comprising a fuel circuit for supplying DME fuel in a fuel tank to a DME engine via a supply line by a feed pump,
Starting a fuel cooler that cools the fuel in at least a portion of the fuel circuit; and
A line opening step of opening the supply line;
A pump starting step of starting the feed pump after the line opening step;
After the pump activation step, the supply line is brought into the atmosphere until the pressure difference between the outlet side and the inlet side of the feed pump is equal to or greater than a predetermined pressure difference and the pressure on the outlet side of the feed pump is equal to or greater than a predetermined pressure. Opening the purge step;
Waiting until the temperature of the fuel at a predetermined position in the fuel circuit is lower than a predetermined temperature after the cooler starting step,
A starter starting step of starting a starter of the DME engine after completion of the purge step and the temperature decrease standby step;
A method for starting a DME engine. Each of the steps is performed in the order of a cooler starting step, a line opening step, a pump starting step, the purge step, the temperature decrease standby step, and the starter starting step.
The method for starting the DME engine according to claim 1. In the purge step, the pressure on the outlet side of the feed pump is detected at a position close to the feed pump and a position close to the DME engine,
The pressure difference for comparison with the predetermined pressure difference is a pressure difference between the pressure on the inlet side of the feed pump and the pressure close to the feed pump,
The pressure for comparison with the predetermined pressure is a pressure close to the DME engine.
The method for starting the DME engine according to claim 1. The fuel circuit includes a return line for returning the fuel from the DME engine to the fuel tank;
The fuel circulates between the DME engine and the fuel tank;
The method for starting the DME engine according to claim 1.

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