Rail pressure stability control method for marine large common rail diesel engine

Abstract

The invention discloses a rail pressure stability control method for a marine large common rail diesel engine, which is characterized in that a low-pressure oil pump mainly pumps diesel oil from an oil tank, a high-pressure oil pump converts low-pressure diesel oil into high-pressure diesel oil and stores the high-pressure diesel oil in a rail pipe, and a controller collects rail cavity pressure in the rail pipe through a pressure sensor. The pressure of a rail cavity is stabilized by controlling a proportional valve on the high-pressure oil pump, an on-board oil injector and an off-board oil injector, and a pressure relief valve relieves the pressure when the pressure of the rail cavity is ultrahigh, so that the safety of the whole system is ensured. The invention further provides a rail pressure stability control method of the marine large common rail diesel engine under the working conditions of sudden power discharge, non-dead closing of an oil pump proportional valve and stormy waves.

Description

Technical Field

[0001] The patent of the present invention relates to the technical field of marine engines, and in particular to a rail pressure stabilization control method for a marine common rail medium- and high-speed diesel engine with a cylinder diameter of 250-350mm. Background Art

[0002] With the introduction of increasingly stringent emission regulations and the increasingly severe fossil energy situation, diesel engines have gradually transitioned from traditional mechanical control systems to electronic control systems, which are divided into single pump electronic control systems and high-pressure common rail electronic control systems. The high-pressure common rail electronic control system can obtain a larger injection pressure and the best atomization effect under any operating condition because the injector pressure is not affected by the speed of the diesel engine. It is significantly better than other types of diesel engines in terms of energy saving and emission reduction. However, the biggest control difficulty of common rail diesel engines lies in the stable control of the pressure in the rail pipe. If the pressure control is unstable, it may lead to abnormal speed fluctuations, incomplete combustion, and even flameout risks.

[0003] During the processing of high-pressure oil pumps and proportional valves, due to problems with processing materials, manufacturing accuracy or manufacturing processes, the proportional valves often cannot be closed during actual use. When the diesel engine is running at a low oil volume, even if the controller has issued a command to completely close the proportional valve, the oil intake of the high-pressure oil pump is still far greater than the oil output of the injector, which will cause the pressure in the rail pipe to continue to rise and there is a risk of overpressure parking.

[0004] During the operation of the diesel engine, due to the complexity of the operating environment, sudden load unloading sometimes occurs. When sudden unloading occurs, the fuel injection volume of the injector is greatly reduced. Due to the mechanical delay characteristics of the proportional valve on the high-pressure oil pump, the rail pressure may rise rapidly and there is a risk of over-pressure shutdown.

[0005] When a diesel engine is traveling in choppy waters, the ups and downs of the propeller will cause the load of the diesel engine to fluctuate, causing the rail pressure to fluctuate back and forth, and may also cause the diesel engine to shut down due to overpressure. Summary of the invention

[0006] In view of the above risks, the problem to be solved by the present invention is: to provide a rail pressure stabilization control method for a large marine common rail diesel engine, by arranging an external fuel injector outside the diesel engine, when the real-time pressure in the rail pipe is greater than a certain value of the target rail pressure, the oil intake amount can be reduced by controlling the opening of the proportional valve on the high-pressure oil pump, and the rail pipe pressure is adjusted by injecting oil from the external fuel injector arranged outside the diesel engine, so that the pressure in the rail pipe is kept near the target value, thereby preventing shutdown due to excessive pressure in the rail pipe.

[0007] In order to solve the above problems, the technical solution of the present invention is:

[0008] A rail pressure stabilization control method for a large marine common rail diesel engine is applied to a rail pressure stabilization control system for a large marine common rail diesel engine. The rail pressure stabilization control system for a large marine common rail diesel engine comprises a fuel tank, a low-pressure fuel pump, a high-pressure fuel pump, a rail pipe, a pressure sensor, a controller, an onboard fuel injector, a pneumatic pressure relief valve, an off-board fuel injector, an oil return system and a safety valve. The high-pressure fuel pump is connected to the low-pressure fuel pump through a fuel pipe, the high-pressure fuel pump is connected to the rail pipe through a high-pressure fuel pipe, the controller is connected to the pressure sensor, the onboard fuel injector, the off-board fuel injector and the pneumatic pressure relief valve through electric wires, the on-board fuel injector and the off-board fuel injector are connected to the rail pipe through a high-pressure fuel pipe, and the off-board fuel injector does not participate in the internal combustion of the diesel engine cylinder.

[0009] The rail pressure stabilization control method for a large marine common rail diesel engine comprises:

[0010] S10, the controller obtains the real-time pressure in the current rail pipe through the pressure sensor;

[0011] S20, the controller compares the real-time pressure with the target pressure;

[0012] S30, if the real-time pressure is less than the target pressure, the controller controls the opening of the proportional valve on the high-pressure oil pump to increase the oil intake;

[0013] S40, if the real-time pressure is greater than the target pressure and the difference between the real-time pressure and the target pressure is within a preset range, the controller controls the opening of the proportional valve on the high-pressure oil pump to reduce the oil intake;

[0014] S50. If the real-time pressure is greater than the target pressure and the difference between the real-time pressure and the target pressure is greater than the maximum value of a preset range, the controller controls the opening of the proportional valve on the high-pressure oil pump to reduce the oil intake, and the controller also controls the opening of the external fuel injector to reduce the real-time pressure in the rail pipe by adjusting the opening frequency and opening duration of the external fuel injector.

[0015] Preferably, the method further comprises:

[0016] S60: If the diesel engine is in a shutdown state, the controller controls the pneumatic pressure relief valve to quickly release the high pressure in the rail pipe;

[0017] S70: If the controller fails and the real-time pressure of the rail pipe exceeds the working pressure of the safety valve, the safety valve opens to release the high pressure in the rail pipe.

[0018] Preferably, in step S30 and step S40, the controller adopts the first PID formula:

[0019]

[0020] Calculate the proportional valve opening u(t) of the high-pressure oil pump, where e(t) is the difference between the actual pressure and the target pressure, K p1 , K i1 , K d1 are pre-calibrated PID proportional, integral and differential coefficients.

[0021] Preferably, in step S50, the controller first controls the external fuel injector to perform fuel injection and pressure reduction according to the initially set injection fuel quantity and injection frequency, and then uses the second PID formula to adjust the injection fuel quantity of the external fuel injector according to the difference between the real-time pressure and the target pressure; the second PID formula is:

[0022] Δu(t)=K p [e(t)-e(t-1)]+K i e(t)+K d [e(t)-2e(t-1)+e(t-2)]

[0023] The increment Δu(t) is the increment of the injection amount of the external fuel injector, e(t) is the difference between the actual pressure and the target pressure, K p2 , K i2 , K d2 are pre-calibrated incremental PID proportional, integral and differential coefficients.

[0024] Preferably, the safety valve is a mechanical spring type safety valve, and the working pressure of the safety valve is greater than the maximum pressure of the pneumatic pressure relief valve controlled by the controller.

[0025] Preferably, the external fuel injector is not provided with a spray hole and does not atomize the fuel.

[0026] Preferably, the rail pressure stabilization control method for a large marine common rail diesel engine is applicable to a marine common rail medium and high speed diesel engine with a cylinder diameter of 250-350 mm.

[0027] After adopting the above technical solution, the advantages of the present invention are:

[0028] The rail pressure stabilization control system and method for a large marine common rail diesel engine described in the present invention, when the diesel engine is in a sudden unloading condition, a wind and wave condition, or the high-pressure oil pump proportional valve cannot be completely closed in a fully closed state, the rail pressure increases, and when the target pressure is exceeded too much, an overpressure shutdown phenomenon may occur. However, due to the small flow rate of the existing PCV valve, it is unable to meet the requirement of timely discharge of excess oil in the rail pipe when overpressure occurs, and the pneumatic pressure relief valve has only two states, open and closed, and cannot be used to control the pressure in the rail pipe. Based on this, the present invention arranges an external fuel injector outside the diesel engine. When the pressure in the rail pipe exceeds the target value too much, the external fuel injector is used to spray oil to reduce the pressure in the rail pipe to reach the target value. The diesel sprayed by the external fuel injector does not enter the diesel engine for combustion, but returns to the fuel tank through the oil return system for recycling, thereby reducing the risk of shutdown of the common rail diesel engine due to excessive rail pressure, and at the same time, does not cause waste of fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic block diagram of the structure of the rail pressure stability control system of the present invention;

[0030] In the figure: 1-fuel tank, 2-low-pressure fuel pump, 3-high-pressure fuel pump, 4-controller, 5-pressure sensor, 6-rail pipe, 7-onboard injector, 8-pneumatic pressure relief valve, 9-offboard injector, 10-oil return system, 11-diesel engine cylinder, 12-safety valve;

[0031] Figure 2 It is a flow chart of the rail pressure stabilization control method of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] like Figure 1 The embodiment of the present application provides a rail pressure stabilization control system for a large common rail diesel engine for a ship, the system comprising a fuel tank 1, a low-pressure fuel pump 2, a high-pressure fuel pump 3, a controller 4, a pressure sensor 5, a rail pipe 6, an onboard injector 7, a pneumatic pressure relief valve 8, an off-board injector 9, an oil return system 10, a diesel engine cylinder 11, and a safety valve 12, wherein Figure 1 The medium-thick arrows indicate the direction of fuel flow, and the thin arrows indicate electrical signals.

[0034] Combination Figure 1The low-pressure oil pump 2 is connected to the oil tank 1 and the high-pressure oil pump 3 through a low-pressure oil pipe. The high-pressure oil pump 3 is connected to the rail pipe 6 through a high-pressure oil pipe. Holes are opened at appropriate positions on the rail pipe 6 and are connected to the safety valve 12, the on-board injector 7, the pneumatic pressure relief valve 8 and the external injector 9 through the high-pressure oil pipe. The controller 4 is connected to the proportional valve, the pressure sensor 5, the on-board injector 7, the external injector 9 and the pneumatic pressure relief valve 8 on the high-pressure oil pump 3 through electric wires.

[0035] The rail pressure stability control system for a large marine common rail diesel engine in the embodiment of the present invention is used for rail pressure stability control, referring to Figure 2 , the rail pressure stabilization control method comprises the following steps:

[0036] Step S10, the controller 4 obtains the real-time pressure in the rail tube 6 through the pressure sensor 5;

[0037] Step S20, the controller 4 compares the real-time pressure with the target pressure;

[0038] Step S30: If the real-time pressure is less than the target pressure, the controller 4 increases the oil intake by opening the proportional valve on the high-pressure oil pump 3;

[0039] Step S40: If the real-time pressure is greater than the target pressure and the difference between the real-time pressure and the target pressure is within a preset range, the controller 4 still reduces the oil intake by controlling the opening of the proportional valve on the high-pressure oil pump 3;

[0040] Step S50, if the real-time pressure is greater than the target pressure and the real-time pressure and the target pressure are greater than a certain value, the controller 4 controls the opening of the proportional valve on the high-pressure oil pump 3 to reduce the oil intake, and also needs to control the opening of the external fuel injector 9 to reduce the actual pressure in the rail pipe 6 by adjusting the opening frequency and opening duration of the external controller 9;

[0041] Step S60: When the diesel engine is in a shutdown state, the controller 4 quickly releases the high pressure in the rail pipe 6 by controlling the pneumatic pressure relief valve 8;

[0042] Step S70 : When the controller 4 fails, if the real-time pressure exceeds the working pressure of the safety valve 12 , the safety valve 12 will directly release the high pressure in the rail pipe 6 .

[0043] When the controller 4 detects that the real-time pressure is less than the target pressure, or the real-time pressure is greater than the target pressure and the difference between the real-time pressure and the target pressure is within a preset range, the difference can be set according to the actual situation, and the following first PID formula is used to adjust the proportional valve opening on the high-pressure oil pump 3. The first PID formula is:

[0044]

[0045] u(t) is the proportional valve opening of high-pressure oil pump 3, e(t) is the difference between the actual pressure and the target pressure, K p1 , K i1 , K d1 are pre-calibrated PID proportional, integral and differential coefficients.

[0046] The external fuel injector 9 is an injector installed on the rail pipe 6 and does not participate in the combustion of the diesel engine cylinder 11. The external fuel injector 9 is required to have no atomization or a very poor atomization effect. The installation position can be reasonably arranged according to actual conditions.

[0047] When the controller 4 detects that the real-time pressure is greater than the target pressure and the difference between the real-time pressure and the target pressure is greater than the maximum value of the preset range, the size of the difference can be set according to the actual situation, and the external injector 9 starts to work. The controller 4 controls the external injector 9 to first inject oil and reduce pressure according to the initially set injection oil quantity and injection frequency, and then uses the following second PID formula to adjust the injection oil quantity of the external injector 9 according to the difference between the real-time pressure and the target pressure. The second PID formula is:

[0048] Δu(t)=K p2 [e(t)-e(t-1)]+K i2 e(t)+K d2 [e(t)-2e(t-1)+e(t-2)]

[0049] Δu(t) is the increment of the injection amount of the external fuel injector 9, e(t) is the difference between the actual pressure and the target pressure, K p2 , K i2 , K d2 are calibrable incremental PID proportional, integral and differential coefficients.

[0050] When the controller 4 detects that the diesel engine is shut down or shuts down due to a fault, the controller 4 will control the pneumatic shear valve 8 to open, so that it opens quickly and releases the pressure in the rail pipe 6 quickly.

[0051] When the controller 4 fails or the pneumatic pressure relief valve 8 is damaged, if the pressure in the diesel engine rail pipe 6 continues to rise, the safety valve 12 is a mechanical spring-type safety valve, and its working pressure is greater than the maximum pressure of the pneumatic pressure relief valve 8 controlled by the controller. When the pressure in the rail pipe 6 rises to the action value of the safety valve 12, the safety valve 12 will open and quickly release the pressure to ensure safety.

[0052] It can be seen that the rail pressure stabilization control method for a large common rail diesel engine for ship provided by the embodiment of the present invention has a simple structure and is easy to operate. When the pressure in the rail pipe 6 increases due to sudden unloading of the diesel engine, wind and wave conditions, or the high-pressure oil pump proportional valve cannot be completely closed due to manufacturing accuracy, the external fuel injector arranged outside the diesel engine can be used to perform non-combustion injection, quickly reduce the fuel in the rail pipe 6, reduce the pressure in the rail pipe 6 and quickly stabilize it near the target pressure, thereby reducing the risk of the diesel engine shutting down due to excessive pressure in the rail pipe 6.

[0053] The above are only typical embodiments of the present invention and are not intended to limit the present invention. Any modifications made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A rail pressure stabilization control method for a large marine common rail diesel engine, applied to a rail pressure stabilization control system for a large marine common rail diesel engine, characterized in that: The rail pressure stabilization control system for a large marine common rail diesel engine comprises a fuel tank (1), a low-pressure fuel pump (2), a high-pressure fuel pump (3), a rail pipe (6), a pressure sensor (5), a controller (4), an onboard fuel injector (7), a pneumatic pressure relief valve (8), an off-board fuel injector (9), an oil return system (10) and a safety valve (12); the high-pressure fuel pump (3) is connected to the low-pressure fuel pump (2) via a fuel pipe; the high-pressure fuel pump (3) is connected to the rail pipe (6) via a high-pressure fuel pipe; the controller (4) is connected to the pressure sensor (5), the on-board fuel injector (7), the off-board fuel injector (9) and the pneumatic pressure relief valve (8) via electric wires; the on-board fuel injector (7) and the off-board fuel injector (9) are connected to the rail pipe (6) via a high-pressure fuel pipe; and the off-board fuel injector (9) does not participate in the internal combustion of the diesel engine cylinder (11); The rail pressure stabilization control method for a large marine common rail diesel engine comprises: S10, the controller (4) obtains the real-time pressure in the current rail tube (6) through the pressure sensor (5); S20, the controller (4) compares the real-time pressure with the target pressure; S30, if the real-time pressure is less than the target pressure, the controller (4) controls the opening of the proportional valve on the high-pressure oil pump (3) to increase the oil intake; S40, if the real-time pressure is greater than the target pressure and the difference between the real-time pressure and the target pressure is within a preset range, the controller (4) controls the opening of the proportional valve on the high-pressure oil pump (3) to reduce the oil intake; S50. If the real-time pressure is greater than the target pressure and the difference between the real-time pressure and the target pressure is greater than the maximum value of a preset range, the controller (4) controls the opening of the proportional valve on the high-pressure oil pump (3) to reduce the oil intake, and the controller also controls the opening of the external fuel injector (9), thereby reducing the real-time pressure in the rail pipe (6) by adjusting the opening frequency and opening duration of the external fuel injector (9).

2. The rail pressure stabilization control method for a large marine common rail diesel engine according to claim 1, characterized in that: The method further comprises: S60, if the diesel engine is in a shutdown state, the controller (4) controls the pneumatic pressure relief valve (8) to quickly release the high pressure in the rail pipe (6); S70: If the controller (4) fails and the real-time pressure of the rail pipe (6) exceeds the working pressure of the safety valve (12), the safety valve (12) opens to release the high pressure in the rail pipe (6).

3. The rail pressure stabilization control method for a large marine common rail diesel engine according to claim 1, characterized in that: In step S30 and step S40, the controller (4) adopts the first PID formula: Calculate the proportional valve opening u(t) of the high-pressure oil pump (3), where e(t) is the difference between the actual pressure and the target pressure, K p1 , K i1 , K d1 are pre-calibrated PID proportional, integral and differential coefficients.

4. The rail pressure stabilization control method for a large marine common rail diesel engine according to claim 1, characterized in that: In step S50, the controller (4) first controls the external fuel injector (9) to perform fuel injection pressure reduction according to the initially set fuel injection amount and injection frequency, and then uses a second PID formula to adjust the fuel injection amount of the external fuel injector (9) according to the difference between the real-time pressure and the target pressure; the second PID formula is: Δu(t)=K p [e(t)-e(t-1)]+K i e(t)+K d [e(t)-2e(t-1)+e(t-2)] The increment Δu(t) is the increment of the injection amount of the external fuel injector (9), e(t) is the difference between the actual pressure and the target pressure, K p2 , K i2 , K d2 are pre-calibrated incremental PID proportional, integral and differential coefficients.

5. The rail pressure stabilization control method for a large common rail diesel engine for marine use according to claim 1, characterized in that: The safety valve (12) is a mechanical spring type safety valve, and the working pressure of the safety valve is greater than the maximum pressure of the pneumatic pressure relief valve (8) controlled by the controller (4).

6. The rail pressure stabilization control method for a large marine common rail diesel engine according to claim 1, characterized in that: The external fuel injector (9) is not provided with a spray hole and does not atomize the fuel.

7. The rail pressure stabilization control method for a large marine common rail diesel engine according to claim 1, characterized in that: The rail pressure stabilization control method for a large marine common rail diesel engine is applicable to a marine common rail medium- and high-speed diesel engine with a cylinder diameter of 250-350 mm.

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