An engine preheating and fuel circulation heating system and method suitable for extremely cold environments

Abstract

The application provides an engine preheating and fuel circulating heating system suitable for extremely cold environment, which comprises an engine, a coolant heater, an oil tank divided into a main oil cavity and a sub oil cavity, a fuel heater and a sub oil cavity oil suction element. The system stores low-grade diesel in the sub oil tank for preheating and stores conventional diesel in the main oil tank to reduce cost. The coolant heater heats the coolant, and the fuel heater heats the diesel in the main oil tank by using the heated coolant. The system also has an oil valve and a driving motor, which can flexibly switch the main oil tank and the sub oil tank to supply oil. In addition, the application also provides a heating method, which comprises the steps of preheating the coolant, starting the engine with low-grade diesel, circulating heating and melting the waxed diesel, and switching to conventional diesel oil supply. Compared with the prior art, the application has significant advantages in cost-effectiveness, engine starting performance, heating efficiency, risk of diesel waxing and system flexibility, and is suitable for stable operation of the engine in extremely cold environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of engines, and particularly relates to an engine preheating and fuel circulation heating system and method suitable for extremely cold environments. BACKGROUND

[0002] In extremely cold environments, the starting and running of engines face severe challenges. Due to the increase in the viscosity of fuel and the poor flowability of fuel under low-temperature conditions, and the characteristic of diesel fuel that is prone to waxing, the traditional engine preheating and fuel supply methods often fail to meet the requirements. In addition, although the use of low-grade diesel fuel in extremely cold regions can improve the low-temperature flowability of fuel, it is costly and the incomplete combustion of fuel reduces the engine efficiency. Therefore, how to provide an engine preheating and fuel circulation heating system and method suitable for extremely cold environments has become a technical problem to be solved at present.

[0003] Most existing engine preheating systems use electric heating or flame injection to preheat the coolant or fuel, but these methods have problems such as high energy consumption, uneven preheating, and low heating efficiency. At the same time, the traditional fuel supply system often only has one fuel tank, and neither the use of regular diesel fuel nor the use of low-grade diesel fuel can balance the cost-effectiveness and engine performance. In particular, in extremely cold regions, the use of regular diesel fuel can easily lead to engine starting difficulties, while the use of low-grade diesel fuel is costly and the incomplete combustion of fuel at low temperatures further reduces the engine efficiency.

[0004] In addition, the existing fuel tank design often does not take into account the problem of diesel waxing. Under low-temperature conditions, diesel fuel is prone to waxing at the bottom of the fuel tank, making it difficult for the oil pump to suck in the diesel fuel that has waxed at the bottom, thereby affecting the normal starting and working of the engine. This problem is particularly prominent in extremely cold regions, posing a great risk to the stable operation of the engine.

[0005] In summary, the existing engine preheating and fuel supply system has many technical defects in extremely cold environments and cannot meet the starting and running requirements of the engine under low-temperature conditions. Therefore, the present application aims to overcome the above technical defects and provide an engine preheating and fuel circulation heating system and method suitable for extremely cold environments to solve the problems of engine starting difficulty, high fuel cost, and diesel waxing in extremely cold regions. SUMMARY

[0006] The technical problem to be solved by the present application is to overcome the above technical defects and provide an engine preheating and fuel circulation heating system and method suitable for extremely cold environments. The purpose of the present application is to realize the rapid and stable starting of the engine in extremely cold environments through optimized system design and innovative working methods, while reducing fuel costs and avoiding the risks caused by diesel waxing.

[0007] To solve the above technical problems, the application provides an engine preheating and fuel circulating heating system suitable for extremely cold environments, comprising:

[0008] An engine, the cylinder body of which is provided with a cooling liquid cavity and a fuel cavity;

[0009] A cooling liquid heater, which is communicated with the cooling liquid cavity through a circulating water path and is used for heating the cooling liquid in the cooling liquid cavity;

[0010] An oil tank, which is divided into a main oil cavity and an auxiliary oil cavity, the auxiliary oil cavity is used for storing low-grade diesel oil, and the main oil cavity is used for storing conventional diesel oil;

[0011] A fuel heater, which is arranged in the main oil cavity and comprises a heater main body, a circulating cavity in the heater main body is communicated with the cooling liquid cavity in circulation, and an oil valve in the heater main body is communicated with the fuel cavity in circulation, a heating element and a main oil cavity oil suction element are arranged below the heater main body, the heating element is communicated with the circulating cavity and is used for receiving the heated cooling liquid from the cooling liquid cavity and heating the conventional diesel oil in the main oil cavity, and the main oil cavity oil suction element is used for sucking the conventional diesel oil in the main oil cavity into the oil valve;

[0012] An auxiliary oil cavity oil suction element, which is arranged in the auxiliary oil cavity, is connected with the oil valve and is used for sucking the low-grade diesel oil in the auxiliary oil cavity into the oil valve, the oil valve is connected with the fuel cavity, and the oil valve is used for switching the working modes of the auxiliary oil cavity oil suction element and the main oil cavity oil suction element through a driving motor arranged outside the oil valve.

[0013] Further, the cooling liquid heater comprises a heating tank main body, a heating cavity is arranged in the heating tank main body, a water pump is further arranged on the heating tank main body, a water suction port of the water pump is communicated with the cooling liquid cavity through a water pipe, a water outlet of the water pump is communicated with the heating cavity, and a hot water outlet of the heating tank main body is returned to the cooling liquid cavity through a circulating pipe.

[0014] Further, the main oil cavity oil suction element comprises a main oil suction pipe, a main oil return pipe and a first filter arranged below the main oil suction pipe and the main oil return pipe;

[0015] The auxiliary oil cavity oil suction element comprises an oil suction main body, a low-grade oil supply port and a low-grade oil return port are arranged above the oil suction main body, an auxiliary oil suction pipe and an auxiliary oil return pipe are arranged below the oil suction main body, and a second filter is arranged below the auxiliary oil suction pipe and the auxiliary oil return pipe;

[0016] The oil valve is provided with a first oil return port, a first oil supply port, a second oil return port and a second oil supply port side by side, the first oil supply port and the fuel cavity are connected through a first oil supply pipe, the first oil return port and the fuel cavity are connected through a first oil return pipe, the second oil supply port and the low-grade oil supply port are connected through a second oil supply pipe, and the second oil return port and the low-grade oil return port are connected through a second oil return pipe.

[0017] Further, a heater oil suction pipe is arranged below the oil suction body, and a heater oil suction port is arranged above the oil suction body and communicates with the heater oil suction pipe, the heater oil suction port is connected to a fuel port on the heating tank body through a fuel pipe, and an oil pump is arranged on the fuel pipe.

[0018] Further, a first liquid level sensor is arranged at the bottom of the heater body, a float ball is arranged on the first liquid level sensor, and a positioning seat is arranged at the lower end of the first liquid level sensor, for monitoring the fuel liquid level in the main oil cavity.

[0019] Further, a second liquid level sensor is arranged at the bottom of the oil suction body, for monitoring the fuel liquid level in the auxiliary oil cavity.

[0020] Further, a first oil supply pipe is arranged on the first oil supply port to the fuel cavity, and a first filter and an oil-water separator are arranged in sequence on the first oil supply pipe.

[0021] Further, the heating element is a spiral heating pipe.

[0022] Further, a water inlet and a water outlet are arranged on the heater body and communicate with the circulating cavity, and the water inlet and the water outlet communicate with the cooling liquid cavity through a water inlet pipe and a water return pipe, respectively.

[0023] The application also provides an engine preheating and fuel circulation heating method suitable for extremely cold environments, comprising the following steps:

[0024] Step one, when the temperature is low, open the stop valves arranged on the water pipe and the circulating pipe respectively, so that the water inlet and outlet of the cooling liquid cavity form a passage; the cooling liquid is pumped out through the water pump on the cooling liquid heater, heated in the heating cavity, and then returned to the cooling liquid cavity; at the same time, the oil pump sucks oil from the auxiliary oil cavity, and the low-grade diesel oil enters the heating tank body through the fuel port to heat the heating cavity;

[0025] Step two, after the engine cylinder is heated, the stop valves, the cooling liquid heater and the oil pump are closed; the driving motor of the liquid fuel heater is started to drive the oil valve to rotate and cut off the connection with the main oil cavity; at this time, only the oil supply element in the auxiliary oil cavity supplies oil, the low-grade diesel oil is pumped from the auxiliary oil suction pipe to the low-grade oil supply port, enters the fuel cavity through the second oil supply pipe, the second oil supply port, the first oil supply port and the first oil supply pipe, and the engine is started; after starting, the low-grade diesel oil returns to the auxiliary oil cavity through the first oil return pipe, the first oil return port, the second oil return port and the second oil return pipe;

[0026] Step three, after the engine is started, the water pump is opened, the heated cooling liquid is pumped into the circulating cavity of the heater body, and the waxed diesel oil in the main oil cavity is transferred to the waxed diesel oil in the main oil cavity through heat exchange in the spiral heating pipe; after the waxed diesel oil is melted, it returns to the fuel cavity to form a closed loop;

[0027] Step four, after completing the low-temperature start of the engine and the diesel heating of the main oil cavity, the oil suction element of the auxiliary oil cavity is cut off; after the fuel in the pipeline is consumed, the driving motor is started again, and the connection between the main oil suction element and the main oil cavity is opened; at this time, the conventional diesel is sucked through the main oil suction pipe, enters the engine cylinder fuel cavity through the first oil supply port and the first oil supply pipe, and the conventional diesel in the fuel cavity flows back to the main oil cavity through the first oil return pipe, the first oil return port and the main oil return pipe; during the period, the water inlet and outlet passage state outside the heater main body is maintained, the heating is continued, the constant temperature is maintained, and the engine is stably supplied with oil.

[0028] Compared with the prior art, the application has obvious advantages in the field of engine preheating and fuel circulation heating in extremely cold environments. By innovatively adopting the main and auxiliary oil tank structure design, the application only needs to store a small amount of low-grade diesel in the auxiliary oil tank, which accounts for 1 / 10 of the overall oil tank capacity, while the main oil tank stores conventional diesel, which accounts for 9 / 10 of the total oil tank capacity. This strategy greatly reduces fuel costs while taking into account the starting performance and operating efficiency of the engine in low-temperature environments. In addition, the application uses low-grade diesel in the auxiliary oil tank for preheating, significantly shortening the preheating time of the engine in extremely cold conditions and improving the success rate of starting. The innovative design of the fuel heater and the coolant heater not only achieves more uniform and efficient heating, but also effectively reduces energy consumption. In view of the problem that diesel is prone to waxing at low temperatures, the application ensures that the conventional diesel can quickly melt the waxed part after the engine starts through the circulation heating method, avoiding the risk of oil pump suction difficulty and engine failure caused by diesel waxing. At the same time, the system enhances the flexibility and reliability of the system through the flexible switching of the oil valve and the driving motor, so that the entire system can operate more stably and economically in extremely cold environments. In summary, the application has obvious advantages in cost-effectiveness, engine starting performance, heating efficiency, risk of avoiding diesel waxing, and system flexibility and reliability. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a schematic diagram of an engine preheating and fuel circulation heating system suitable for extremely cold environments in the application;

[0030] Figure 2 is Figure 1 is a partial enlarged schematic diagram of the oil tank in

[0031] Figure 3 is a structural schematic diagram of the coolant heater in the application;

[0032] Figure 4 is a structural schematic diagram of the fuel heater in the application;

[0033] Figure 5 is a split structural schematic diagram of the fuel heater in the application;

[0034] Figure 6 is a schematic diagram of the oil suction element of the secondary oil cavity in the application;

[0035] Figure 7 is a schematic diagram of the sectional top structure of the oil suction element of the secondary oil cavity in the application;

[0036] Figure 8 is a schematic diagram of the installation of the engine preheating and fuel oil circulation heating system in the application suitable for extremely cold environments;

[0037] Figure 9 is a schematic diagram of the principle of the oil suction element of the primary oil cavity in the application in operation;

[0038] Figure 10 is a schematic diagram of the principle of the oil suction element of the secondary oil cavity in the application in operation.

[0039] As shown in the figure: 1, engine, 2, coolant heater, 21, heater main body, 211, fuel port, 22, water pump, 3, oil tank, 31, primary oil cavity, 32, secondary oil cavity, 4, fuel heater, 41, heater main body, 411, water inlet, 412, water outlet, 413, water inlet pipe, 414, water return pipe, 42, oil valve, 421, drive motor, 422, first oil return port, 423, first oil supply port, 424, second oil return port, 425, second oil supply port, 43, heating element, 44, primary oil cavity oil suction element, 441, primary oil suction pipe, 442, primary oil return pipe, 443, first filter, 5, secondary oil cavity oil suction element, 51, oil suction main body, 511, low-grade oil supply port, 512, low-grade oil return port, 52, secondary oil suction pipe, 53, secondary oil return pipe, 54, second filter, 55, heater oil suction pipe, 56, heater oil suction port, 6, circulation waterway, 61, circulation pipe, 71, first oil supply pipe, 72, first oil return pipe, 73, second oil supply pipe, 74, second oil return pipe, 8, fuel oil pipe, 81, oil pump, 9, first liquid level sensor, 10, second liquid level sensor, 11, primary filter, 12, oil-water separator. DETAILED DESCRIPTION

[0040] The application will be further described in detail below with reference to the accompanying drawings.

[0041] The specific embodiments of the application will be further described below with reference to the accompanying drawings. The same parts are denoted by the same reference numerals.

[0042] It should be noted that the words "front", "back", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings, and the words "in" and "out" refer to the directions towards or away from the geometric center of a particular part.

[0043] In order to make the content of the present application more easily and clearly understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

[0044] Reference is made to the accompanying drawings Figure 1 - the accompanying drawings Figure 10 The present application provides an engine preheating and fuel circulation heating system suitable for extremely cold environments, comprising: an engine 1, the cylinder body of which is provided with a coolant cavity and a fuel cavity; a coolant heater 2, which is in communication with the coolant cavity through a circulation waterway 6 and is used for heating the coolant in the coolant cavity; an oil tank 3, which is divided into a main oil cavity 31 and a secondary oil cavity 32, wherein the main oil cavity 31 stores conventional diesel oil and accounts for 9 / 10 of the total volume of the oil tank 3, and the secondary oil cavity 32 stores low-grade diesel oil and accounts for only 1 / 10 of the total volume of the oil tank 3, which significantly reduces the storage cost of oil; a fuel heater 4, which is arranged inside the main oil cavity 31 and comprises a heater main body 41, a circulation cavity in the heater main body 41 is in circulation communication with the coolant cavity, and an oil valve 42 is in circulation communication with the fuel cavity, a heating element 43 and a main oil cavity oil suction element 44 are arranged below the heater main body 41, wherein the heating element 43 is in communication with the circulation cavity and is used for receiving the heated coolant from the coolant cavity and heating the conventional diesel oil in the main oil cavity 31, and the main oil cavity oil suction element 44 is used for sucking the conventional diesel oil in the main oil cavity 31 into the oil valve 42; a secondary oil cavity oil suction element 5, which is arranged inside the secondary oil cavity 32 and is connected with the oil valve 42 and used for sucking the low-grade diesel oil in the secondary oil cavity 32 into the oil valve 42, the oil valve 42 is connected with the fuel cavity and the oil valve 42 is provided with a driving motor 421 outside to switch the working modes of the secondary oil cavity oil suction element 5 and the main oil cavity oil suction element 44.

[0045] In order to more efficiently heat the coolant, the inside of the coolant heater 2 comprises a heating tank main body 21, which is provided with a heating cavity inside. A water pump 22 is arranged on the heating tank main body 21, which pumps water from the coolant cavity through a water pipe, heats the water through the heating cavity, and then returns to the coolant cavity through a circulation pipe 61, forming a closed-loop heating system.

[0046] In an embodiment, in order to further improve the heating efficiency and fuel utilization rate of the system, a heater oil suction pipe 55 is additionally arranged below the oil suction main body 51. The oil suction pipe is connected with the fuel oil pipe 8 through a heater oil suction port 56 to directly deliver the low-grade diesel oil to the fuel port 211 of the heating tank main body 21 for heating. In order to control the supply amount of fuel, an oil pump 81 is arranged on the fuel oil pipe 8 to adjust the flow rate of fuel as needed.

[0047] Meanwhile, in order to monitor the fuel level in the main oil cavity 31 and the auxiliary oil cavity 32 in real time, the first liquid level sensor 9 is arranged below the main oil cavity oil suction element 44, and the second liquid level sensor 10 is arranged below the auxiliary oil cavity oil suction element 5. Both the first liquid level sensor 9 and the second liquid level sensor 10 adopt a floating ball design and can float up and down with the rise and fall of the fuel level, thereby accurately reflecting the amount of fuel in the fuel tank 3. Through real-time monitoring of the first liquid level sensor 9 and the second liquid level sensor 10, timely replenishment of fuel can be ensured and the situation of fuel depletion can be avoided.

[0048] The oil valve 42 is provided with a first return oil port 422, a first oil supply port 423, a second return oil port 424 and a second oil supply port 425 side by side, the first oil supply port 423 is connected with the fuel cavity through the first oil supply pipe 71, the first return oil port 422 is connected with the fuel cavity through the first return oil pipe 72, the second oil supply port 425 is connected with the low-grade diesel oil supply port 511 through the second oil supply pipe 73, and the second return oil port 424 is connected with the low-grade diesel oil return port 512 through the second return oil pipe 74. Through the switching of the oil valve 42, low-grade diesel oil can be used during the engine preheating stage, and regular diesel oil can be switched to during the normal operation stage, thereby meeting the needs of the engine at different stages.

[0049] In order to further improve the heating efficiency and fuel utilization rate of the system, a heater oil suction pipe 55 is additionally arranged below the oil suction body 51. The heater oil suction pipe 55 is connected with the fuel oil pipe 8 through a heater oil suction port 56 to directly deliver low-grade diesel oil to the fuel port 211 of the heating tank body 21 for heating. In order to control the supply amount of fuel, an oil pump 81 is arranged on the fuel oil pipe 8 to adjust the flow rate of fuel as needed.

[0050] In order to further improve the purity and safety of fuel, a primary filter 11 and an oil-water separator 12 are arranged on the first oil supply pipe 71 in sequence in the direction from the first oil supply port 423 to the fuel cavity. The primary filter 11 can further intercept and remove small particles and impurities in the fuel, and the oil-water separator 12 can effectively separate water from the fuel to prevent water from damaging the engine. The addition of these two devices makes the fuel supplied to the engine 1 more pure and safe.

[0051] In one embodiment, the heating element 43 is a spiral heating pipe. This design not only improves the heating efficiency, but also makes the heating more uniform, avoiding the occurrence of local overheating or insufficient temperature. At the same time, the spiral heating pipe has a compact structure and occupies a small space, which is conducive to reducing the overall volume and weight of the system.

[0052] Further, the heater body 41 is provided with a water inlet 411 and a water outlet 412 communicating with the circulating cavity, and the water inlet 411 and the water outlet 412 communicate with the cooling liquid cavity through the water inlet pipe 413 and the water return pipe 414 respectively, forming a closed loop circulation with the cooling liquid cavity. Through the heat exchange between the cooling liquid in the circulating cavity and the heating element 43, the heat after heating can be transmitted to the conventional diesel oil in the main oil cavity 31, so as to realize the preheating and anti-waxing function of the fuel oil. This design not only improves the heating efficiency of the fuel oil, but also reduces the energy consumption and cost.

[0053] The application also provides an engine preheating and fuel oil circulating heating method suitable for extremely cold environment, comprising the following steps:

[0054] Step one, when the temperature is low, open the respective stop valves provided on the water pipe and the circulating pipe 61 to form a passage for the cooling liquid cavity inlet and outlet, and then the cooling liquid is pumped out through the water pump 22 on the cooling liquid heater 2, heated in the heating cavity and then returned to the cooling liquid cavity; at the same time, the oil pump 81 is started to suck the oil from the auxiliary oil cavity 32, and the oil is heated in the heating cavity through the fuel inlet 211 of the heating tank body 21;

[0055] Step two, after the engine 1 cylinder body is heated, the stop valves, the cooling liquid heater 2 and the oil pump 81 are closed, the driving motor 421 of the liquid fuel oil heater 4 is started, the oil valve 42 is driven to rotate to cut off the connection with the main oil cavity 31; at this time, only the auxiliary oil cavity oil suction element 5 supplies oil, the low-grade diesel oil is pumped from the auxiliary oil suction pipe 52 to the low-grade oil supply port 511, and then enters the fuel cavity through the second oil supply pipe 73, the second oil supply port 425, the first oil supply port 423 and the first oil supply pipe 71, and the engine is started; the low-grade diesel oil after starting is returned to the auxiliary oil cavity 32 through the first oil return pipe 72, the first oil return port 422, the second oil return port 424 and the second oil return pipe 74;

[0056] Step three, after the engine 1 is started, the water pump 22 is opened, the heated cooling liquid is pumped into the circulating cavity of the heater body 41, and then enters the spiral heating pipe to transmit heat to the waxed diesel oil in the main oil cavity 31 through heat exchange; after the waxed diesel oil is melted, it returns to the fuel cavity, forming a closed loop;

[0057] Step four, after the engine low-temperature starting and the diesel oil heating in the main oil cavity are completed, the oil supply of the auxiliary oil cavity oil suction element 5 is cut off; after the fuel in the pipeline is consumed, the driving motor 421 is started again to open the connection between the main oil cavity oil suction element 44 and the main oil cavity 31; at this time, the conventional diesel oil is sucked through the main oil suction pipe 441, enters the engine cylinder fuel cavity through the first oil supply port 423 and the first oil supply pipe 71, and the conventional diesel oil in the fuel cavity returns to the main oil cavity 31 through the first oil return pipe 72, the first oil return port 422 and the main oil return pipe 442; during this period, the water inlet 411 and the water outlet 412 outside the heater body 41 are kept in a passage state, and the heating is continued to maintain a constant temperature and stable oil supply for the engine.

[0058] The above describes the present application and its embodiments, which are not limited, and the drawings only show one of the embodiments of the present application, and the actual structure is not limited thereto. In general, if a person skilled in the art is inspired thereby, without departing from the purpose of the present application, without creative design, similar structure and embodiments of the technical solution are not creative, and should belong to the protection scope of the present application.

Claims

1. A method for engine preheating and fuel circulation heating suitable for extremely cold environments, applied to an engine preheating and fuel circulation heating system suitable for extremely cold environments, the heating system comprising an engine (1), a coolant heater (2) and an oil tank (3), the cylinder body of the engine (1) being provided with a coolant cavity and a fuel cavity, the coolant heater (2) being in communication with the coolant cavity through a circulating water path (6) and being used for heating the coolant in the coolant cavity, the oil tank (3) being divided into a main oil cavity (31) and a secondary oil cavity (32), the secondary oil cavity (32) being used for storing low-grade diesel oil, and the main oil cavity (31) being used for storing regular diesel oil; the main oil cavity (31) being provided with a fuel heater (4), and the secondary oil cavity (32) being provided with a secondary oil cavity oil suction element (5), characterized in that, The method comprises the following steps: Step one, at low temperature, open the respective stop valves arranged on the water pipe and the circulation pipe (61) to form a passage between the inlet and outlet of the cooling liquid chamber; The cooling liquid is pumped out through the water pump (22) on the cooling liquid heater (2), heated in the heating chamber, and then returned to the cooling liquid chamber; at the same time, oil is pumped from the auxiliary oil chamber (32) through the oil pump (81), enters the heating tank main body (21) of the cooling liquid heater (2) through the fuel port (211), and heats the heating chamber; Step two, after the cylinder of the engine (1) is heated, the stop valves, the cooling liquid heater (2), and the oil pump (81) are closed; the driving motor (421) of the fuel heater (4) is started to drive the oil valve (42) to rotate and cut off the connection with the main oil chamber (31); at this time, oil is supplied only through the auxiliary oil chamber oil suction element (5), low-grade diesel is pumped from the auxiliary oil suction pipe (52) to the low-grade oil supply port (511), enters the fuel chamber through the second oil supply pipe (73), the second oil supply port (425), the first oil supply port (423), and the first oil supply pipe (71), and the low-grade diesel after the engine is started is returned to the auxiliary oil chamber (32) through the first oil return pipe (72), the first oil return port (422), the second oil return port (424), and the second oil return pipe (74); Step three, after the engine (1) is started, the water pump (22) is opened to pump the heated cooling liquid into the circulation chamber of the heater main body (41) of the fuel heater (4), and the waxy diesel in the main oil chamber (31) is transferred to the fuel chamber through heat exchange in the spiral heating pipe, and the waxy diesel after melting is returned to the fuel chamber to form a closed loop; Step four, after the engine low-temperature starting and the main oil chamber diesel heating are completed, the oil supply of the auxiliary oil chamber oil suction element (5) is cut off; after the fuel in the pipeline is consumed, the driving motor (421) is started again to open the connection between the main oil chamber oil suction element (44) and the main oil chamber (31); at this time, the conventional diesel is sucked through the main oil suction pipe (441), enters the engine cylinder fuel chamber through the first oil supply port (423) and the first oil supply pipe (71), and the conventional diesel in the fuel chamber is returned to the main oil chamber (31) through the first oil return pipe (72), the first oil return port (422), and the main oil return pipe (442); during the period, the water inlet (411) and the water outlet (412) outside the heater main body (41) are kept in a passage state, continuous heating is maintained, the temperature is kept constant, and stable oil supply is provided for the engine.

2. An engine preheating and fuel circulation heating system suitable for use in extremely cold environments for performing the method of claim 1, characterized in that, The method comprises the following steps: The engine (1) has a cylinder provided with a cooling liquid chamber and a fuel chamber; The cooling liquid heater (2) is connected with the cooling liquid chamber through a circulation water path (6) and is used for heating the cooling liquid in the cooling liquid chamber; The oil tank (3) is divided into a main oil chamber (31) and an auxiliary oil chamber (32), the auxiliary oil chamber (32) is used for storing low-grade diesel, and the main oil chamber (31) is used for storing conventional diesel; The fuel heater (4) is arranged in the main oil cavity (31) and comprises a heater main body (41), a circulating cavity in the heater main body (41) is in circulation communication with the coolant cavity, and an oil valve (42) in circulation communication with the fuel cavity; a heating element (43) and a main oil cavity oil suction element (44) are arranged below the heater main body (41), the heating element (43) is in communication with the circulating cavity and is used for receiving heated coolant from the coolant cavity and heating the conventional diesel oil in the main oil cavity (31), and the main oil cavity oil suction element (44) is used for sucking the conventional diesel oil in the main oil cavity (31) into the oil valve (42); The auxiliary oil cavity oil suction element (5) is arranged in the auxiliary oil cavity (32) and is connected with the oil valve (42) and used for sucking the low-grade diesel oil in the auxiliary oil cavity (32) into the oil valve (42); the oil valve (42) is connected with the fuel cavity and is switched by a driving motor (421) arranged outside the oil valve (42) to switch the working modes of the auxiliary oil cavity oil suction element (5) and the main oil cavity oil suction element (44).

3. The engine pre-heat and fuel circulation heating system for extremely cold environments of claim 2, wherein, The coolant heater (2) comprises a heating tank main body (21), a heating cavity is arranged in the heating tank main body (21), a water pump (22) is further arranged on the heating tank main body (21), a water suction port of the water pump (22) is in communication with the coolant cavity through a water pipe, a water outlet of the water pump is in communication with the heating cavity, and a hot water outlet on the heating tank main body (21) is backflowed into the coolant cavity through a circulating pipe (61).

4. The engine pre-heat and fuel circulation heating system for extremely cold environments of claim 2, wherein, The main oil cavity oil suction element (44) comprises a main oil suction pipe (441), a main oil return pipe (442) and a first filter (443) arranged below the main oil suction pipe (441) and the main oil return pipe (442); The auxiliary oil cavity oil suction element (5) comprises an oil suction main body (51), a low-grade oil supply port (511) and a low-grade oil return port (512) are arranged above the oil suction main body (51), an auxiliary oil suction pipe (52) and an auxiliary oil return pipe (53) are arranged below the oil suction main body (51), and a second filter (54) is arranged below the auxiliary oil suction pipe (52) and the auxiliary oil return pipe (53); The oil valve (42) is provided with a first oil return port (422), a first oil supply port (423), a second oil return port (424) and a second oil supply port (425) side by side, the first oil supply port (423) is connected with the fuel cavity through a first oil supply pipe (71), the first oil return port (422) is connected with the fuel cavity through a first oil return pipe (72), the second oil supply port (425) is connected with the low-grade oil supply port (511) through a second oil supply pipe (73), and the second oil return port (424) is connected with the low-grade oil return port (512) through a second oil return pipe (74).

5. The engine pre-heat and fuel circulation heating system for extremely cold environments of claim 4, wherein, A heater oil suction pipe (55) is further arranged below the oil suction main body (51), a heater oil suction port (56) in communication with the heater oil suction pipe (55) is arranged above the oil suction main body (51), the heater oil suction port (56) is connected to a fuel port (211) on the heating tank main body (21) through a fuel oil pipe (8), and an oil pump (81) is arranged on the fuel oil pipe (8).

6. The engine pre-heat and fuel circulation heating system for extremely cold environments of claim 4, wherein, The bottom of the heater body (41) is further provided with a first liquid level sensor (9), the first liquid level sensor (9) is provided with a floating ball, and the lower end of the first liquid level sensor (9) is provided with a positioning seat for monitoring the fuel liquid level in the main oil cavity (31).

7. The engine pre-heat and fuel circulation heating system for extremely cold environments of claim 4, wherein, The bottom of the oil suction body (51) is further provided with a second liquid level sensor (10) for monitoring the fuel liquid level in the auxiliary oil cavity (32).

8. The engine pre-heat and fuel circulation heating system for extremely cold environments of claim 4, wherein, A first oil supply pipe (71) is arranged on the first oil supply pipe (71) in sequence from the first oil supply port (423) to the fuel cavity, and a first filter (11) and an oil-water separator (12) are arranged in sequence.

9. The engine pre-heat and fuel circulation heating system for extremely cold environments of claim 2, wherein, The heating element (43) is a spiral heating pipe.

10. The engine pre-heat and fuel circulation heating system for extremely cold environments of claim 2, wherein, The heater body (41) is provided with a water inlet (411) and a water outlet (412) communicated with the circulating cavity, and the water inlet (411) and the water outlet (412) are communicated with the cooling liquid cavity through a water inlet pipe (413) and a water return pipe (414) respectively.

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