A dry sump engine circulating pre-lubrication system

Abstract

The application discloses a dry sump engine circulating pre-lubricating system and a control method thereof. The application utilizes an electric double pre-lubricating oil pump and original oil oil circuit of an engine pump, and before the engine starts, heated oil in an oil tank is delivered to each friction pair along the original oil oil circuit through the electric double pre-lubricating oil pump, each friction pair and its upstream lubricating pipeline are filled with the heated oil, and after being heated, the heated oil is circulated and returned to the oil tank, thus breaking the conventional thinking of low-temperature pre-lubrication of the dry sump engine, and each friction pair such as a shaft neck bearing bush is pre-lubricated and pre-heated before the engine starts at low temperature, the cooperation clearance is close to the state when the engine works, and movement constraint is more sufficient, and wear caused by insufficient movement constraint of the friction pair is effectively reduced. The oil circulation of the pre-lubricating system also enhances the convection of the oil in the oil tank, the oil is more uniformly heated, and the oil in the oil tank is better pumped.

Description

Technical Field

[0001] This invention relates to the field of engine pre-lubrication technology, specifically to a dry sump engine circulating pre-lubrication system and its control method. Background Technology

[0002] Statistics show that approximately 90% of engine mechanical failures and scrapping are related to wear of friction pairs. Research indicates that although engine starting time accounts for only a small portion of total operating time, the total wear of each friction pair during engine starting is higher than the total wear during other operating times. This is mainly because the engine oil pump 102 is linked to the engine crankshaft and cannot work independently before starting to establish sufficient oil pressure for lubrication, resulting in each friction pair operating in a dry friction state during engine starting.

[0003] In low-temperature environments, engine oil viscosity increases significantly and fluidity decreases drastically, making it more difficult for the engine oil pump 102 to establish sufficient oil pressure for lubrication during cold starts. Although dry-sump engine oil tanks 100 designed for low-temperature environments are often equipped with serpentine coils 109 for oil heating, natural convection heat exchange between hot and cold oil is difficult, and even after prolonged heating, a large amount of low-temperature oil that is difficult to pump still remains in the oil tank 100.

[0004] When the engine's friction pairs are at low temperatures, their clearances are larger than at high temperatures. During a cold start of the engine, excessive clearances can lead to insufficient motion constraint on the friction pairs, resulting in abnormal contact and additional wear. Current methods of heating the engine with high-temperature coolant can only heat the piston assembly-cylinder liner friction pair 117, and cannot heat the main journal-main bearing friction pair 112, the connecting rod journal-connecting rod big end bearing friction pair 113, the connecting rod small end bushing-piston pin friction pair 116, or other friction pairs 114. Therefore, the temperature of each friction pair remains low during a cold start. Summary of the Invention

[0005] In view of this, the present invention provides a circulating pre-lubrication system and control method for a dry sump engine, which can effectively achieve pre-lubrication and heating of various friction pairs in a dry sump engine in a low-temperature environment, reduce wear of friction pairs, and improve engine service life.

[0006] The dry sump engine circulating pre-lubrication system of the present invention includes: an oil tank heating device and a dual pre-lubrication oil pump; wherein, the oil tank heating device is used to heat the oil in the oil tank; the dual pre-lubrication oil pump includes a pressure oil sub-pump and a return oil sub-pump, the pressure oil sub-pump is used to deliver the oil to the oil pump delivery pipe of the engine oil pump and deliver it along the oil pump delivery pipe to each friction pair of the engine and its upstream lubrication pipeline; the return oil sub-pump is used to deliver the oil in the dry sump to the oil tank, thereby completing the recycling of the oil.

[0007] Preferably, the oil outlet of the return oil sub-pump is connected to the oil tank through the oil outlet pipe of the return oil sub-pump; or, the oil outlet of the return oil sub-pump is connected to the return pipe of the engine return oil pump through the one-way valve of the return oil sub-pump, and finally connected to the oil tank.

[0008] Preferably, a check valve is provided on the connecting oil pipe between the oil pump of the sub-pump and the oil pump of the generator.

[0009] Ideally, the pressure oil sub-pump and the return oil sub-pump operate and stop synchronously; during operation, the flow rate of the return oil sub-pump is greater than that of the pressure oil sub-pump.

[0010] Preferably, the oil tank heating device is a serpentine coil and a cooling water heater; the serpentine coil is placed inside the oil tank, and high-temperature cooling water heated by the cooling water heater flows through it.

[0011] Preferably, the oil tank heating device is a tower-shaped coil and a cooling water heater; the inlet of the tower-shaped coil is at the bottom and the outlet is at the top, and high-temperature cooling water heated by the cooling water heater is introduced into it.

[0012] Preferably, in the tower-shaped coil, the width difference and / or length difference between two adjacent coil layers is greater than or equal to twice the coil diameter.

[0013] Preferably, the tower-shaped coil is either upright or inverted.

[0014] The present invention also provides a control method for the above-mentioned dry sump engine circulating pre-lubrication system, comprising:

[0015] S1, detect the oil temperature in the oil tank. If the oil temperature T ≤ T1, then use an oil tank heating device to heat the oil in the oil tank. T1 is the minimum pumpable temperature. If the oil temperature T > T1, then proceed to step S2.

[0016] S2, turn on the oil pressure sub-pump and the oil return sub-pump. The oil in the oil tank is transmitted to each friction pair of the engine and its upstream lubrication line by the oil pressure sub-pump, and then returned to the oil tank by the oil return sub-pump.

[0017] After the oil pressure sub-pump and return sub-pump have been working for time t1 (S3), the engine has been fully pre-lubricated and is now ready for a safe and efficient cold start. The oil pressure sub-pump and return sub-pump are then shut off, and the engine enters the cold start procedure.

[0018] Ideally, the pressure P at the end of the engine lubrication passage should be checked. If P is stable and greater than a pressure P1 higher than normal pressure, it indicates that the engine has been fully pre-lubricated and is ready for safe and efficient cold start.

[0019] Beneficial effects:

[0020] This invention utilizes the existing oil circuit of the electric dual-unit pre-lubricating oil pump and the engine pump. Before engine start-up, heated oil from the oil pan is delivered to each friction pair via the electric dual-unit pre-lubricating oil pump along the existing oil circuit. The heated oil fills each friction pair and its upstream lubrication lines, and after heating, it circulates back to the oil pan. This breaks with the conventional thinking of low-temperature pre-lubrication for dry-sump engines, ensuring that all journals, bearings, and other friction pairs are pre-lubricated and preheated before a cold start. The clearance is close to that during engine operation, resulting in more sufficient motion constraint and effectively reducing wear caused by insufficient motion constraint of the friction pairs. The oil circulation in this pre-lubrication system also enhances oil convection within the oil pan, resulting in more uniform oil heating and better oil pumpability within the oil pan. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the dry sump engine circulating pre-lubrication system of the present invention.

[0022] Figure 2 This diagram illustrates the oil flow direction when the engine is running, the lubrication system is working, and the pre-lubrication system of this invention is not working.

[0023] Figure 3 This diagram illustrates the oil flow direction when the engine is stopped, the lubrication system is not working, and the pre-lubrication system of this invention is in operation.

[0024] Figure 4 This is a schematic diagram of a second implementation of the pre-lubrication system of the present invention.

[0025] Figure 5 This is a schematic diagram illustrating the heating method of the pre-lubrication system of the present invention for each friction pair of the engine.

[0026] Figure 6 This invention describes the control process of the pre-lubrication system under low-temperature cold start conditions where the engine requires external auxiliary heating.

[0027] Figure 7 This is the control process of the pre-lubrication system of the present invention under normal cold start conditions when the engine does not require external auxiliary heating.

[0028] Figure 8 This is a schematic diagram of a serpentine coil in the shape of a tower.

[0029] Figure 9 This is a top view of a tower-shaped coil, where the sections do not obstruct each other in the vertical direction.

[0030] Figure 10 This is a schematic diagram of the natural convection direction of a tower-shaped coil.

[0031] Wherein, 100-oil tank; 101-oil tank strainer; 102-engine oil pump; 103-oil pump oil passage; 104-other parts of the engine lubrication system (including oil filter, oil cooler, piston cooling nozzles, journals, bearings, etc., excluding oil tank, dry sump, engine oil pump, engine return pump and its associated strainer); 105-dry sump; 106-return pump strainer; 107-Engine return oil pump; 108-Return oil pump return pipe; 109-Serpentine coil; 110-Cooling water heater; 111-Oil filter and oil cooler; 112-Main journal-main bearing friction pair; 113-Connecting rod journal-connecting rod big end bearing friction pair; 114-Other friction pairs; 115-Piston cooling nozzle; 116-Connecting rod small end bushing-piston pin friction pair; 117-Piston assembly-cylinder liner friction pair; 118-Engine cooling system; 119-Engine cylinder water jacket; 200-Electric dual pre-lubricating oil pump; 201-Motor; 202-Oil sub-pump; 203-Oil sub-pump filter; 204-Oil sub-pump inlet pipe; 205-Oil sub-pump outlet pipe; 206-Oil sub-pump check valve; 207-Oil pump pre-lubrication pump inlet; 208-Return sub-pump; 209-Return sub-pump inlet pipe; 210-Return sub-pump filter; 211-Return sub-pump outlet pipe; 212-Return sub-pump check valve; 213-Return pump return pipe pre-lubrication pump inlet; 14-Positive tower-shaped coil; 16-Coil inlet; 17-Coil outlet. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] This invention provides a dry sump engine circulating pre-lubrication system.

[0034] A dry sump engine lubrication system generally includes: an oil tank 100, an oil tank strainer 101, an engine oil pump 102, an oil pump oil passage 103, a dry sump 105, a return oil pump strainer 106, an engine return oil pump 107, a return oil pump return pipe 108, and components including an oil filter, oil cooler, piston cooling nozzles, journals, and bearings, but excludes the oil tank, dry sump, engine oil pump, engine return oil pump, and their associated strainers, which constitute other parts of the engine lubrication system 104. The general structure of other parts of the engine lubrication system 104 includes an oil filter and oil cooler 111, a main journal-main bearing friction pair 112, a connecting rod journal-connecting rod big end bearing friction pair 113, a piston cooling nozzle 115, a connecting rod small end bushing-piston pin friction pair 116, a piston assembly-cylinder liner friction pair 117, and other friction pairs 114.

[0035] like Figure 1 As shown, the present invention includes a serpentine coil 109 installed in the oil tank 100 to heat the oil in the oil tank 100; simultaneously, an electric dual pre-lubrication oil pump 200 is installed, which includes a motor 201, a pressure sub-pump 202, and a return sub-pump 208; the pressure sub-pump 202 directly delivers the oil in the oil tank 100 to the oil pump delivery pipe 103 and then delivers it to the engine lubrication system along the oil pump delivery pipe 103. Other components (including oil filter, oil cooler, piston cooling nozzles, journals, bearings, etc., excluding oil tank, dry sump, engine oil pump, engine return oil pump and its associated filter); the return oil sub-pump 208 transports the oil in the dry sump 105 to the oil tank 100, completing the oil circulation and making the hot and cold oil in the oil tank 100 more evenly mixed, effectively improving the pumpability of the oil in the oil tank 100 when the engine starts. This invention utilizes an electric dual pre-lubricating oil pump 200 to transport heated oil from the oil tank along the existing oil path to each friction pair. Hot oil fills and heats each friction pair and its upstream lubrication lines, ensuring sufficient lubrication for each friction pair before starting in low-temperature environments, reducing their clearance.

[0036] When the engine is running, the lubrication system is working, or this pre-lubrication system is not working or is not installed, if Figure 2As shown, engine oil is drawn from the bottom of the oil tank 100 through the oil tank strainer 101 to the engine oil pump 102. After being pressurized by the engine oil pump 102, it is sent to other parts 104 of the engine lubrication system through the oil pump delivery passage 103 to lubricate the engine before falling back into the dry sump 105. After the engine oil pump 102 pressurizes the oil, it flows through the pre-lubrication pump inlet 207 into the pre-lubrication system pressure pump 202 described in this invention, but is blocked at the pressure pump check valve 206. Therefore, this pre-lubrication system will not cause the engine oil pump 102 to depressurize during operation. After falling back into the dry sump 105, the oil is drawn through the return pump strainer 106 to the engine return pump 107, where it is pressurized and sent back to the oil tank 100 through the return pump return pipe 108. Figure 4 In form two shown, the engine oil pressurized by the engine return oil pump 107 flows to the pre-lubrication system return oil sub-pump 208 through the return oil pump return pipe pre-lubrication pump inlet 213, but is blocked at the return oil sub-pump check valve 212. This pre-lubrication system will not cause the engine return oil pump 107 to depressurize when it is working.

[0037] The electric dual pre-lubricating oil pump 200 is mechanically connected by a motor 201, a pressure sub-pump 202, and a return sub-pump 208. When energized, all three operate together; when de-energized, they all stop operating together. During operation, the flow rate of the return sub-pump 208 is slightly greater than that of the pressure sub-pump 202 to ensure that not all the oil in the oil tank 100 is drawn into other parts of the engine lubrication system 104 and the dry sump 105, thus preventing the engine oil pump 102 from promptly pumping oil to other parts of the engine lubrication system 104 after engine start-up. The electric dual pre-lubricating oil pump 200 has a compact structure, allowing for flexible placement; it can be placed outside the engine, outside the oil tank 100, or in other suitable locations. In addition to the above, compared to engines without this pre-lubrication system, engines equipped with this pre-lubrication system also include an oil sub-pump filter 203, an oil sub-pump inlet pipe 204, an oil sub-pump outlet pipe 205, an oil sub-pump check valve 206, an oil pump delivery passage pre-lubrication pump inlet 207, a return oil sub-pump inlet pipe 209, and a return oil sub-pump filter 210, such as... Figure 1 The form shown also includes an oil return sub-pump outlet pipe 211; as shown Figure 2The second type shown also includes a return oil sub-pump check valve 212 and a return oil pump return pipe pre-lubrication pump inlet 213. The oil inlet of the pre-lubrication system's pressure oil sub-pump 202 is connected to the oil tank 100 via the pressure oil sub-pump filter 203 and pressure oil sub-pump inlet pipe 204. Its outlet is connected to the pressure oil sub-pump outlet pipe 205, and then connected to the pre-lubrication pump inlet 207 of the oil pump delivery passage via the pressure oil sub-pump check valve 206, leading to the oil pump delivery passage 103 and connecting to other parts of the engine lubrication system 104. The oil inlet of the return oil sub-pump 208 is connected to the dry oil pan 105 via the return oil sub-pump inlet pipe 209 and return oil sub-pump filter 210. The outlet of the return oil sub-pump 208 connects to the oil tank 100 in two ways: as shown in... Figure 1 In form one shown, the oil outlet of the return oil sub-pump 208 is directly connected to the oil tank 100 via the return oil sub-pump outlet pipe 211; in such a case... Figure 4 In form two shown, the oil outlet of the return oil sub-pump 208 is connected to the pre-lubrication pump inlet 213 of the return oil pump return pipe via the return oil sub-pump check valve 212 and then to the return oil pump return pipe 108, and finally connected to the oil tank 100.

[0038] When the engine is stopped, the lubrication system is not working, and this pre-lubrication system is working, such as Figure 3As shown, the oil pump 202 draws heated engine oil from the oil tank 100 via the oil pump strainer 203 and the oil pump inlet pipe 204. After pressurization, the oil is supplied to other parts 104 of the engine lubrication system through the oil pump outlet pipe 205, the oil pump check valve 206, and the pre-lubrication pump inlet 207 of the oil pump delivery passage. In the oil pump delivery passage 103, some engine oil flows to the engine oil pump 102. However, when the engine is stopped, the engine oil pump 102 cannot rotate due to its linkage with the engine crankshaft. The engine oil can only leak back to the oil tank 100 through the tiny fit gaps between the components of the engine oil pump 102. The leakage is very small and has minimal impact on the operation of this pre-lubrication system. In other parts of the engine lubrication system 104, after heating and filling the friction pairs such as journal bearings, cylinder liners, and piston rings with oil, the cooled oil falls into the dry oil pan 105. It is then drawn to the return oil sub-pump 208 via the return oil sub-pump filter 210 and the return oil sub-pump inlet pipe 209, and after pressurization, is delivered towards the oil tank. In form one, the oil flows directly back to the oil tank 100 through the return oil sub-pump outlet pipe 211; while in form two, the oil flows through the return oil sub-pump check valve 212 to the return oil pump return pipe pre-lubrication pump inlet 213, and then flows back to the oil tank through the return oil pump return pipe 108. In the return oil pipe 108 of the return oil pump, some engine oil flows to the engine return oil pump 107. However, when the engine stops, the engine return oil pump 107 cannot rotate because it is linked with the engine crankshaft. The engine oil can only leak back to the dry oil pan 105 through the tiny fit gaps between the components inside the engine return oil pump 107. The leakage amount of this leakage phenomenon is very small and has little impact on the operation of this pre-lubrication system.

[0039] In low-temperature environments, when the engine is off, the lubrication system is not working, and this pre-lubrication system is working, such as Figure 5 As shown, heated engine oil passes through the oil filter and oil cooler 111 into other parts 104 of the engine lubrication system, and is delivered to the main journal-main bearing friction pair 112, piston cooling nozzle 115, and other friction pairs 114. A portion of the hot oil delivered to the main journal-main bearing friction pair 112 is further delivered through oil holes in the crankshaft to the connecting rod journal-connecting rod big end bearing friction pair 113; the hot oil delivered to the piston cooling nozzle 115 is sprayed onto the connecting rod small end bushing-piston pin friction pair 116 and the piston assembly-cylinder liner friction pair 117; the remaining hot oil is delivered to the other friction pairs 114. The hot oil not only fills the above friction pairs and their upstream lubrication lines, but also heats them. Afterwards, the cooled oil falls back into the dry sump 105 and is pumped back to the oil tank 100 by the return oil sub-pump 208. During this process, the high-temperature cooling water flowing through the engine cylinder water jacket 119 in the engine cooling system 118 also heats the piston assembly-cylinder liner friction pair 117, but cannot heat other friction pairs.

[0040] This invention's pre-lubrication system can be used in both low-temperature cold start conditions where the engine requires external auxiliary heating and normal cold start conditions where the engine does not require external auxiliary heating. For example... Figure 6 As shown, in low-temperature cold start conditions where the engine requires external auxiliary heating, the engine oil must be heated to a minimum pumpable temperature T1 before this pre-lubrication system can begin operation. During external auxiliary heating, when the oil pan temperature sensor displays an oil temperature T > T1, the motor 201 can be automatically or manually activated, initiating the pre-lubrication system to pre-lubricate the engine and circulate the oil. After the pre-lubrication system has been operating for time t1, the engine is sufficiently pre-lubricated, and the oil in the oil pan is fully circulated. At this point, the engine is ready for a safe and efficient cold start. Disconnecting the power to the motor 201 allows the engine to enter the cold start procedure. The pre-lubrication system's operating time t1 can be automatically controlled by the program based on the oil pan temperature T, the engine lubrication passage end pressure P, or other sensor parameters, or it can be determined by the operator based on experimental results or usage experience.

[0041] like Figure 7 As shown, under normal cold start conditions where the engine does not require external auxiliary heating, the oil in the oil tank is in a readily pumpable state. Before starting the engine, the motor 201 can be directly connected to pre-lubricate the engine. After this pre-lubrication system is activated, when the sensor detects that the pressure P at the end of the engine lubrication passage has stabilized and is greater than a pressure P1 higher than atmospheric pressure, it indicates that the other parts 104 of the engine lubrication system have been fully filled and the engine has been fully pre-lubricated. At this time, the engine is ready for safe and efficient cold start. After disconnecting the power to the motor 201, the engine cold start procedure can be entered.

[0042] This pre-lubrication system circulates and heats the engine oil used in dry-sump engines between the engine lubrication system and the oil tank 100. Before a cold start at low temperatures, all journals, bearings, and other friction pairs are pre-lubricated and preheated, allowing for rapid oil pressure build-up during engine start-up. The oil circulation provided by this pre-lubrication system also enhances oil convection within the oil tank 100, resulting in more uniform oil heating and better oil pumpability. During engine start-up, all friction pairs are heated, causing their temperature to rise and the clearance to approach the engine's operating state, further reducing wear caused by insufficient constraint on the movement of friction pairs.

[0043] Furthermore, to further improve the heating efficiency of the engine oil, this invention improves the oil tank heating device. Existing serpentine coils utilize high-temperature cooling water inside to conduct heat to the engine oil on the coil surface via the coil wall. The heated oil, with its density decreasing, rises due to the density difference between the hot and cold oil, relying on vertical natural convection caused by this density difference. However, the rising oil heated by the lower layer of the serpentine coil is obstructed by the upper layer of pipes, increasing flow resistance, reducing the natural convection velocity, and ultimately weakening the vertical natural convection heat transfer effect. Simultaneously, only a thin layer of oil near the coil wall participates in heat exchange with the wall. This layer of oil contacts each layer of the coil during its vertical natural convection as it rises and is heated multiple times, reaching a temperature much higher than the oil in other locations within the oil tank. This reduces the temperature difference between the oil participating in heat transfer and the coil wall, resulting in a decrease in the total heat flow between the serpentine coil and the oil, and a slower average oil temperature rise.

[0044] This invention proposes a tower-shaped coil, such as Figure 8 and Figure 9 As shown, replace the ordinary serpentine coil with a regular tower coil or an inverted tower coil. Figure 8 The placement of the coil, the location of the inlet, and the location of the outlet are basically the same as the original serpentine coil; only the shape of the coil is changed. In a typical serpentine coil, each layer has the same shape and overlaps vertically. In the tower-shaped coil, the length and width of each layer gradually decrease from the bottom to the top, such as... Figure 8 As shown (inverted tower-shaped coils, the layers gradually increase in size). For example... Figure 9 As shown, viewed vertically, in the case of a tower-shaped coil 14, each layer is either unobstructed or only partially obstructed by the upper layer. The upper coil's obstruction of the vertical natural convection of engine oil is significantly less than that of a conventional serpentine coil. Preferably, the difference in length and width between adjacent layers is greater than or equal to twice the pipe diameter; in this case, each layer is unobstructed by the upper layer, resulting in even better vertical natural convection of engine oil. Figure 10 As shown, the oil near the pipe walls rises after being heated and separates from the upper pipe wall, forming multiple vertical natural convection loops. The oil temperature in the oil pan is more uniform, and the pumpability is greatly improved.

[0045] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dry sump engine circulating pre-lubrication system for pre-lubrication and heating before low-temperature cold starts, characterized in that, include: An oil tank heating device and a dual pre-lubricating oil pump are provided. The oil tank heating device is used to heat the oil in the oil tank. The dual pre-lubricating oil pump includes a motor (201), a pressure oil sub-pump, and a return oil sub-pump. The motor (201) drives the pressure oil sub-pump and the return oil sub-pump. The pressure oil sub-pump is used to deliver the oil to the oil pump delivery pipe of the engine oil pump and deliver it to each friction pair of the engine and its upstream lubrication pipeline along the oil pump delivery pipe. The return oil sub-pump is used to deliver the oil in the dry sump to the oil tank to complete the recycling of the oil. The operating principle of this circulating pre-lubrication system is as follows: When the engine is stopped, the oil temperature in the oil tank is checked. If the oil temperature in the oil tank T≤T1, the oil tank heating device is used to heat the oil in the oil tank. T1 is the minimum pumpable temperature. If the oil temperature in the oil tank T>T1, the motor (201) is turned on to drive the oil pressure pump and the oil return pump. The engine is pre-lubricated and the oil is circulated within time t1. The hot oil in the oil tank is transferred to each friction pair of the engine and its upstream lubrication pipeline by the oil pressure pump. It not only fills the friction pairs of the engine and its upstream lubrication pipeline, but also heats them. The cooled oil falls back into the dry oil pan and is then returned to the oil tank by the oil return pump. The oil convects in the oil tank, and the oil is heated more evenly. The engine oil circulates and is heated between the engine lubrication system and the oil tank. After the oil pressure pump and oil return pump have been working for t1 time, the engine is fully pre-lubricated and preheated. At this time, the engine is ready for safe and efficient cold start. The oil pressure pump and oil return pump are then turned off, and the engine enters the cold start procedure.

2. The dry sump engine circulating pre-lubrication system as described in claim 1, characterized in that, The oil outlet of the return oil sub-pump is connected to the oil tank through the oil outlet pipe of the return oil sub-pump; or, the oil outlet of the return oil sub-pump is connected to the return pipe of the engine return oil pump through the one-way valve of the return oil sub-pump, and finally connected to the oil tank.

3. The dry sump engine circulating pre-lubrication system as described in claim 1, characterized in that, A one-way valve is installed on the connecting oil pipe between the oil pump sub-pump and the oil pump of the generator.

4. The dry sump engine circulating pre-lubrication system as described in claim 1, characterized in that, The pressure oil sub-pump and the return oil sub-pump operate and stop synchronously; during operation, the flow rate of the return oil sub-pump is greater than that of the pressure oil sub-pump.

5. The dry sump engine circulating pre-lubrication system as described in claim 1, characterized in that, The oil tank heating device consists of a serpentine coil and a cooling water heater; the serpentine coil is placed inside the oil tank, through which high-temperature cooling water heated by the cooling water heater flows.

6. The dry sump engine circulating pre-lubrication system as described in claim 1, characterized in that, The oil tank heating device is a tower-shaped coil and a cooling water heater; the inlet of the tower-shaped coil is at the bottom and the outlet is at the top, and high-temperature cooling water heated by the cooling water heater flows into it.

7. The dry sump engine circulating pre-lubrication system as described in claim 6, characterized in that, In the tower-shaped coil, the width difference and / or length difference between two adjacent coil layers is greater than or equal to twice the coil diameter.

8. The dry sump engine circulating pre-lubrication system as described in claim 6 or 7, characterized in that, The tower-shaped coil can be either upright or inverted.

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