A method and system for eliminating water vapor condensation in an engine crankcase

Abstract

The present invention discloses a method and system for eliminating condensation of water vapor in an engine crankcase, comprising: generating negative pressure at the engine crankcase outlet according to the engine operating state and the external ambient temperature, so that the engine crankcase blowby gas flows out; introducing fresh dry air from the engine crankcase air inlet according to the engine operating state, the external ambient temperature and the crankcase humidity, until the engine crankcase humidity is below a set value and the solenoid valve is closed. The present invention generates negative pressure at the engine crankcase outlet and introduces fresh dry air at the engine crankcase air inlet, thereby accelerating the crankcase blowby gas out of the crankcase, reducing the amount of water vapor condensation in the crankcase, and preventing the crankcase oil from emulsifying, the valve mechanism from rusting, and the valve mechanism from getting stuck. The present invention has a simple structure, low cost, and high efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of engines, and in particular relates to a method and a system for eliminating water vapor condensation in an engine crankcase. Background Art

[0002] The application of low-carbon and zero-carbon energy such as natural gas, hydrogen, and ammonia has become a new direction for the development of internal combustion engines. However, these low-carbon and zero-carbon fuels produce more water after combustion, leading to water vapor condensation in the engine crankcase and the resulting oil emulsification, frequent rust and sticking of the valve mechanism, and adverse effects on the normal use of the engine.

[0003] Existing technical solutions to the problem of water vapor condensation mostly use an external high-pressure gas storage tank as a gas source for diluting and scavenging the crankcase blowby gas after the engine is shut down, and use a supercharger to compress gas to dilute and scavenge the blowby gas in the engine crankcase when the engine is running.

[0004] The Chinese patent "A method and engine for preventing engine oil emulsification", publication number CN113969810A, publication date 2022-01-25, discloses a method and engine for preventing engine oil emulsification. The method for preventing engine oil emulsification mainly includes that when the engine is turned off, the ECU receives the engine's flameout signal, and the ECU controls the solenoid valve to open the air path between the air storage source and the crankcase. The air storage source delivers dry gas to the crankcase, and by injecting dry gas, the gas flow in the crankcase is accelerated, and the mixed water vapor in the crankcase is diluted, thereby delaying the emulsification and dilution of the engine oil, and can extend the service life of the engine oil. This patent controls the connection between the external air storage tank and the crankcase through a solenoid valve. After the engine is stopped, the ECU controls the solenoid valve to open, and the high-pressure gas enters the crankcase. After a period of time or when the crankcase pressure reaches a certain pressure value, the solenoid valve is closed to achieve the purpose of crankcase scavenging.

[0005] The Chinese patent "A method and engine for preventing engine oil emulsification", publication number CN113969810A, publication date 2017-02-08, discloses an engine local oil emulsification prevention system, including an engine, a fresh air inlet, a three-way valve, a supercharger, an oil-gas separator, a solenoid valve and an air filter. The engine includes an oil pan, a cylinder block, a cylinder head and a cylinder head cover connected to each other from bottom to top. The gas flowing out of the exhaust gas outlet and the fresh air inlet is divided into two parts after flowing out through the supercharger and the three-way valve. One part enters the cylinder body for combustion, and the other part passes through the solenoid valve, air filter, oil pan, cylinder block, cylinder head and cylinder head cover in sequence to dilute and replace the exhaust gas in the engine crankcase from bottom to top. This patent realizes the scavenging function of the blowby gas in the crankcase when the engine is running by introducing fresh air after the supercharger.

[0006] Through the above description, the prior art has the following disadvantages:

[0007] 1. All existing technical solutions can only realize the blowby gas dilution and scavenging functions in the crankcase of the vehicle under certain working conditions, and cannot meet the application under various working conditions at the same time.

[0008] 2. The existing technologies all require the use of high-pressure fresh air to achieve dilution and scavenging of crankcase blowby gas, which requires the provision of an additional power source, has a complex structure and is costly.

[0009] 3. The condensation of water vapor in the engine crankcase is closely related to the ambient temperature of the vehicle, especially in cold environments, where water vapor condensation is more likely to occur. Existing technical solutions cannot achieve blowby dilution and scavenging control at different ambient temperatures, and the actual application effect is poor.

[0010] As hydrogen engines, ammonia engines, hydrogen / ammonia engines and other technical projects are transformed into commercial projects, the problem of water vapor condensation in the engine crankcase will become more and more serious. The engine water vapor condensation will cause a series of serious problems such as engine oil emulsification, valve jamming and rusting, brake rocker jamming and rusting, oil-gas separator rusting and jamming. In order to solve the water vapor condensation problem, it is necessary to discharge the water blowby gas in the crankcase in time or dilute the crankcase blowby gas, and ensure that no water vapor stays in the engine crankcase after the engine is shut down, so as to prevent the above-mentioned faults from being caused after a long shutdown. Summary of the invention

[0011] In view of the technical problems existing in the background technology, the purpose of the present invention is to provide a system and method for eliminating water vapor condensation in the engine crankcase with simple structure and low cost.

[0012] To achieve the above-mentioned purpose, the method for eliminating water vapor condensation in an engine crankcase designed by the present invention comprises: generating negative pressure at the air outlet of the engine crankcase according to the engine operating state and the external ambient temperature, so that the engine crankcase blowby gas flows out; introducing fresh dry air from the engine crankcase air inlet according to the engine operating state, the external ambient temperature and the crankcase humidity, until the solenoid valve is closed when the engine crankcase humidity is below the set value.

[0013] Preferably, when the engine is stopped and the external ambient temperature is lower than the first preset temperature value T1, if the engine crankcase humidity is greater than the first preset humidity value HUM1, negative pressure is generated at the engine crankcase air outlet and fresh dry air is introduced from the engine crankcase air inlet until the engine crankcase humidity is lower than the first preset humidity value HUM1, and the generation of negative pressure and the introduction of fresh dry air are stopped.

[0014] Further preferably, the first preset temperature value T1 is in the range of 0°C to 5°C.

[0015] Further preferably, the first preset humidity value HUM1 ranges from 40% to 95%.

[0016] Preferably, when the engine is running, the negative pressure value at the engine crankcase outlet is set according to the external ambient temperature: the lower the external ambient temperature, the greater the negative pressure.

[0017] Further preferably, when the external ambient temperature is greater than -25°C, negative pressure is generated at the engine crankcase air outlet, and fresh dry air is not introduced from the engine crankcase air inlet; when the external ambient temperature is less than -25°C, negative pressure is generated at the engine crankcase air outlet, and fresh dry air is introduced from the engine crankcase air inlet.

[0018] Still further preferably, when the external ambient temperature is less than -25°C, the dew point humidity X of water vapor condensation at this time is calculated based on the engine crankcase pressure and temperature, a negative pressure P3 is generated at the engine crankcase air outlet, and fresh dry air is introduced from the engine crankcase air inlet, and the engine crankcase humidity is controlled to be lower than the dew point humidity X until the engine is shut down, and the introduction of fresh dry air from the engine crankcase air inlet is stopped.

[0019] Still more preferably, the negative pressure when the external environment temperature is greater than 0°C is denoted as P1, and the negative pressure when the external environment temperature is between -25°C and 0°C is denoted as P2, and P1 is smaller than P2.

[0020] More preferably, when the external ambient temperature is less than -25 degrees Celsius, a) the engine crankcase humidity is greater than the dew point humidity X, and P3 is greater than P2; b) when the engine crankcase humidity is less than the dew point humidity X, P3 is equal to P2.

[0021] Preferably, the device for generating negative pressure at the outlet of the engine crankcase is an electrically driven centrifugal separator, and the negative pressure at the outlet of the engine crankcase is adjusted by adjusting the speed of the electrically driven centrifugal separator, and the higher the speed, the greater the negative pressure. Of course, other electrically driven separator devices may also be used.

[0022] Further preferably, the pressure of the electrically driven centrifugal separator is controlled to ensure that the engine crankcase pressure is within a working range.

[0023] To achieve the above object, the system designed by the present invention for eliminating water vapor condensation in the engine crankcase comprises:

[0024] A negative pressure generating device is connected to the air outlet of the engine crankcase through a pipeline;

[0025] An air filter, the air inlet of which is connected to the air inlet pipe, and the air outlet of which is connected to the air inlet of the engine crankcase through a pipeline;

[0026] The solenoid valve is installed on the pipeline between the air filter outlet and the engine crankcase air inlet to control the opening and closing of the pipeline;

[0027] An ambient temperature sensor is electrically connected to the control unit to obtain the external ambient temperature;

[0028] A crankcase humidity sensor is electrically connected to the control unit to obtain the engine crankcase humidity;

[0029] The control unit is electrically connected to the negative pressure generating device to control the rotation speed of the negative pressure generating device; and is electrically connected to the solenoid valve to control the opening and closing of the solenoid valve;

[0030] The control unit controls the negative pressure generating device to generate negative pressure according to the engine operating state and the external ambient temperature, so that the engine crankcase blowby gas flows out;

[0031] The control unit controls the opening and closing of the solenoid valve according to the engine operating status, external ambient temperature and crankcase humidity, introducing dry air until the engine crankcase humidity is below the set value and the solenoid valve is closed.

[0032] Preferably, when the engine is stopped and the external ambient temperature is lower than the first preset temperature value T1, if the engine crankcase humidity is greater than the first preset humidity value HUM1, the negative pressure generating device and the solenoid valve are turned on until the engine crankcase humidity is lower than the first preset humidity value HUM1, and then the negative pressure generating device and the solenoid valve are turned off.

[0033] Further preferably, the first preset temperature value T1 is in the range of 0°C to 5°C.

[0034] Further preferably, the first preset humidity value HUM1 ranges from 40% to 95%.

[0035] Preferably, when the engine is running, the negative pressure value at the engine crankcase outlet is set according to the external ambient temperature: the lower the external ambient temperature, the greater the negative pressure.

[0036] Further preferably, when the external ambient temperature is greater than -25°C, the negative pressure generating device is turned on and the solenoid valve is closed; when the external ambient temperature is less than -25°C, the negative pressure generating device and the solenoid valve are turned on.

[0037] Still further preferably, it also includes a crankcase pressure sensor and a crankcase temperature sensor electrically connected to the control unit; the crankcase pressure sensor is used to measure the crankcase pressure, and the crankcase temperature sensor is used to measure the crankcase temperature;

[0038] When the external ambient temperature is less than -25℃, the dew point humidity X of water vapor condensation is calculated according to the engine crankcase pressure and temperature, the negative pressure generating device and the solenoid valve are turned on, and the engine crankcase humidity is controlled to be lower than the dew point humidity X until the engine stops, and the solenoid valve is closed.

[0039] Preferably, the negative pressure generating device is an electrically driven centrifugal separator, and the negative pressure at the engine crankcase outlet is adjusted by adjusting the speed of the electrically driven centrifugal separator, and the higher the speed, the greater the negative pressure. Of course, other electrically driven separator devices may also be used.

[0040] Further preferably, it also includes a crankcase pressure sensor for measuring the crankcase pressure, which is electrically connected to the control unit; the control unit controls the pressure of the electric-driven centrifugal separator according to the crankcase pressure value to ensure that the engine crankcase pressure is within the working range.

[0041] Preferably, a drying device is provided between the air filter and the air inlet of the engine crankcase to make the fresh air introduced into the engine crankcase drier.

[0042] The beneficial effects of the present invention are as follows: the present invention generates negative pressure at the engine crankcase outlet and introduces fresh dry air at the engine crankcase inlet, thereby accelerating the crankcase blowby gas out of the crankcase, reducing the amount of water vapor condensation in the crankcase, and preventing the crankcase oil from emulsifying and the valve mechanism from rusting and getting stuck.

[0043] The invention has the advantages of simple structure, low cost and high efficiency.

[0044] The present invention can effectively solve the problem of water vapor condensation in the crankcase, and has important use value for the subsequent development of crankcase ventilation systems for hydrogen engines, ammonia engines, and hydrogen / ammonia engines. It can reduce the probability of serious oil emulsification and other rust problems caused by water vapor condensation after the engine is put on the market, and eliminate user complaints, which has important economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The structural diagram of the present invention is DETAILED DESCRIPTION

[0046] The technical solution of the present invention (including the preferred technical solution) is further described in detail below by means of the accompanying drawings and by listing some optional embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0048] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0049] like Figure 1 As shown, in order to achieve the above-mentioned purpose, the method for eliminating water vapor condensation in the engine crankcase designed by the present invention comprises: generating negative pressure at the engine crankcase air outlet according to the engine operating state and the external ambient temperature, so that the engine crankcase blowby gas flows out; introducing fresh dry air from the engine crankcase air inlet according to the engine operating state, the external ambient temperature and the crankcase humidity, until the engine crankcase humidity is below the set value and the solenoid valve is closed.

[0050] When the engine is shut down, which in the present invention refers to a change from a running state to a shut down state, and the external ambient temperature is lower than a first preset temperature value T1, if the engine crankcase humidity is greater than a first preset humidity value HUM1, negative pressure is generated at the engine crankcase air outlet and fresh dry air is introduced from the engine crankcase air inlet until the engine crankcase humidity is less than or greater than the first preset humidity value HUM1, and the generation of negative pressure and the introduction of fresh dry air are stopped.

[0051] The system designed by the present invention for eliminating water vapor condensation in an engine crankcase comprises:

[0052] A negative pressure generating device is connected to the air outlet of the engine crankcase through a pipeline;

[0053] An air filter, the air inlet of which is connected to the air inlet pipe, and the air outlet of which is connected to the air inlet of the engine crankcase through a pipeline;

[0054] The solenoid valve is installed on the pipeline between the air filter outlet and the engine crankcase air inlet to control the opening and closing of the pipeline;

[0055] An ambient temperature sensor is electrically connected to the control unit to obtain the external ambient temperature;

[0056] A crankcase humidity sensor is electrically connected to the control unit to obtain the engine crankcase humidity;

[0057] A crankcase pressure sensor is electrically connected to the control unit; the crankcase pressure sensor is used to measure the crankcase pressure;

[0058] A crankcase temperature sensor is electrically connected to the control unit; the crankcase temperature sensor is used to measure the crankcase temperature;

[0059] The control unit is electrically connected to the negative pressure generating device to control the rotation speed of the negative pressure generating device; and is electrically connected to the solenoid valve to control the opening and closing of the solenoid valve;

[0060] The control unit controls the negative pressure generating device to generate negative pressure according to the engine operating state and the external ambient temperature, so that the engine crankcase blowby gas flows out;

[0061] The control unit controls the opening and closing of the solenoid valve according to the engine operating status, external ambient temperature and crankcase humidity, introducing dry air until the engine crankcase humidity is below the set value and the solenoid valve is closed.

[0062] The negative pressure generating device is an electrically driven centrifugal separator, and the negative pressure at the engine crankcase outlet is adjusted by adjusting the speed of the electrically driven centrifugal separator, and the higher the speed, the greater the negative pressure. Of course, other electrically driven separator devices may also be used.

[0063] In some optional embodiments of the present invention, the electrically driven centrifugal separator is provided with a rotation speed sensor and a pressure regulating valve.

[0064] The engine senses the changes in ambient temperature and engine speed through the ECU, controls the speed change of the electric drive centrifugal separator and the opening and closing of the solenoid valve, and realizes the blowby gas dilution and scavenging functions under different temperature conditions and engine operating conditions. The specific control strategy is as follows:

[0065] (1) The value of the ambient temperature sensor is higher than a certain value, for example, 0℃~5℃, and the engine speed sensor value is greater than 500rpm (indicating that the engine is running normally):

[0066] The ECU controls the electric drive centrifugal separator to run at a constant speed L, the solenoid valve remains closed, and the value of the crankcase pressure sensor is ensured to be within a certain safety range; the range selected in this embodiment is: -5kpa to 5kpa

[0067] (2) The value of the ambient temperature sensor is lower than a certain value, such as 0℃~5℃, and the engine stops, that is, the engine speed sensor value changes from >500rpm to <500rpm, indicating that the engine changes from the running state to the stopped state:

[0068] The ECU controls the solenoid valve to open, and the pipeline between the air filter and the engine crankcase is connected. At this time, dry air can enter the engine crankcase from the engine crankcase air inlet;

[0069] The ECU controls the electric-driven centrifugal separator to run at a constant speed, for example, 10000, to extract the blow-by gas containing water vapor in the crankcase out of the crankcase, and at the same time, fresh air enters the engine crankcase after being filtered by the air filter, so as to dilute and remove the water vapor of the blow-by gas in the engine crankcase, and the electric-driven centrifugal separator separates and cleans the engine oil in the mixed gas; at the same time, it is ensured that the value of the engine crankcase pressure sensor is within a certain safety range, and the range selected in this embodiment is: -5kpa to 5kpa;

[0070] When the value of the crankcase humidity sensor is lower than a certain set value, such as 40% to 95%, the ECU controls the solenoid valve to close and the electric-driven centrifugal separator to stop working;

[0071] (3) When the value of the ambient temperature sensor is between -25 and 0°C, the engine is running, that is, the value of the engine speed sensor is greater than 500 rpm (indicating that the engine is running normally):

[0072] The electric-driven centrifugal separator runs at a constant speed M (M>L), and the solenoid valve remains closed to ensure that the value of the crankcase pressure sensor is within a certain safety range. In this embodiment, the range selected is: -5kpa to 5kpa;

[0073] (4) The value of the ambient temperature sensor is lower than a certain value (e.g. -25°C), and the engine is running, that is, the value of the engine speed sensor is greater than 500 rpm (indicating that the engine is running normally):

[0074] The ECU controls the solenoid valve to open, so that the pipeline connecting the vehicle air filter and the engine crankcase is connected;

[0075] At this time, the electric-driven centrifugal separator runs normally at the set speed M. The ECU controls the value of the electric-driven centrifugal separator speed sensor to increase to a higher value of N, N>M. While accelerating the extraction of the blowby gas containing water vapor in the crankcase, fresh air enters the crankcase to dilute the blowby gas in the crankcase. At the same time, the separator separates the engine oil from the mixed gas.

[0076] The ECU calculates the dew point humidity X of the water vapor condensation at this time based on the crankcase pressure sensor value and the crankcase temperature sensor value. The dew point X can be obtained by difference calculation based on the common crankcase pressure and temperature data and the corresponding water vapor condensation dew point data table, and controls the electric drive centrifugal separator to run at a speed of N until the value of the crankcase humidity sensor is lower than X, ensuring that water vapor will not condense in the crankcase. At the same time, the value of the crankcase pressure sensor is ensured to be within a certain safety range, such as -5kpa to 5kpa, until the engine stops, the ECU controls the solenoid valve to close, the separator speed drops to a constant speed M, and continues to work.

[0077] In some optional embodiments of the present invention, the electrically driven separator may be replaced with a centrifugal separator with other driving forces, such as an oil-driven separator, and the ECU controls the separator rotation speed by controlling its driving oil pressure.

[0078] In some optional embodiments of the present invention, the electrically driven separator may also be replaced with other negative pressure generating devices, whose main purpose is to form negative pressure in the crankcase to introduce fresh dry air, thereby diluting and driving away the blowby gas in the crankcase to prevent water vapor condensation.

[0079] In some optional embodiments of the present invention, a suction drying device may be added between the air filter and the crankcase, so that the fresh air introduced into the crankcase is drier and the water vapor dilution efficiency is higher.

[0080] At normal ambient temperature (above 0°C), with the engine running, the electric-driven centrifugal separator runs at a speed of L;

[0081] When the ambient temperature is below 0℃ and the engine changes from running to shutdown, the electric-driven centrifugal separator runs at a constant speed (10,000 rpm) until the crankcase humidity is below a certain value, ensuring that there is no condensation of water vapor in the crankcase after the engine is shut down, preventing the emulsification of the crankcase oil, rusting and jamming of the valve train;

[0082] When the ambient temperature is between -25℃ and 0℃ and the engine is running, increase the speed of the electric drive centrifugal separator to M (M>L) to accelerate the crankcase blowby gas out of the crankcase, reduce the amount of water vapor condensation in the crankcase, and prevent the oil in the crankcase from emulsifying, rusting and jamming of the valve mechanism;

[0083] When the ambient temperature is lower than -25℃ and the engine is running, continue to increase the speed of the electric drive centrifugal separator to N (N>M), and open the solenoid valve at the same time to introduce fresh dry air, accelerate the crankcase blowby gas out of the crankcase, dilute the blowby gas, reduce the amount of water vapor condensation in the crankcase, and prevent the oil in the crankcase from emulsification and the valve mechanism from rusting and sticking;

[0084] The pressure regulating valve installed in the electric-driven centrifugal separator can ensure that the crankcase pressure is stable within a reasonable range (-5kpa to 5kpa) under any working conditions.

[0085] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0086] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0087] Those skilled in the art will readily appreciate that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, combinations, replacements, improvements, etc. made within the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A method for eliminating water vapor condensation in an engine crankcase, characterized in that: According to the engine operating state and the external ambient temperature, negative pressure is generated at the engine crankcase air outlet to allow the engine crankcase blowby air to flow out; according to the engine operating state, the external ambient temperature and the crankcase humidity, fresh dry air is introduced from the engine crankcase air inlet until the engine crankcase humidity is below the set value and the solenoid valve is closed; when the engine is stopped and the external ambient temperature is lower than the first temperature preset value T1, if the engine crankcase humidity is greater than the first humidity preset value HUM1, negative pressure is generated at the engine crankcase air outlet and fresh dry air is introduced from the engine crankcase air inlet until the engine crankcase humidity is less than the first humidity preset value HUM1, and the generation of negative pressure and the introduction of fresh dry air are stopped.

2. The method for eliminating water vapor condensation in an engine crankcase according to claim 1, characterized in that: The range of the first preset temperature value T1 is 0° C. to 5° C.; the range of the first preset humidity value HUM1 is 40% to 95%.

3. The method for eliminating water vapor condensation in an engine crankcase according to claim 1, characterized in that: When the engine is running, if the external ambient temperature is greater than -25°C, negative pressure is generated at the engine crankcase air outlet, and fresh dry air is not introduced from the engine crankcase air inlet; if the external ambient temperature is less than -25°C, negative pressure is generated at the engine crankcase air outlet, and fresh dry air is introduced from the engine crankcase air inlet.

4. The method for eliminating water vapor condensation in an engine crankcase according to claim 3, characterized in that: When the external ambient temperature is less than -25°C, the dew point humidity X of water vapor condensation is calculated based on the engine crankcase pressure and temperature, a negative pressure P3 is generated at the engine crankcase air outlet, and fresh dry air is introduced from the engine crankcase air inlet. The engine crankcase humidity is controlled to be lower than the dew point humidity X until the engine is shut down, and the introduction of fresh dry air from the engine crankcase air inlet is stopped.

5. The method for eliminating water vapor condensation in an engine crankcase according to claim 4, characterized in that: Suppose the negative pressure when the external ambient temperature is greater than 0°C is P1, and the negative pressure when the external ambient temperature is between -25°C and 0°C is P2, and P1 is less than P2; when the external ambient temperature is less than -25 degrees Celsius, a) when the engine crankcase humidity is greater than the dew point humidity X, P3 is greater than P2; b) when the engine crankcase temperature is less than the dew point humidity X, P3 is equal to P2.

6. A system for eliminating water vapor condensation in an engine crankcase, using the method for eliminating water vapor condensation in an engine crankcase as claimed in any one of claims 1 to 5, characterized in that: include: A negative pressure generating device is connected to the air outlet of the engine crankcase through a pipeline; An air filter, the air inlet of which is connected to the air inlet pipe, and the air outlet of which is connected to the air inlet of the engine crankcase through a pipeline; The solenoid valve is installed on the pipeline between the air filter outlet and the engine crankcase air inlet to control the opening and closing of the pipeline; An ambient temperature sensor is electrically connected to the control unit to obtain the external ambient temperature; A crankcase humidity sensor is electrically connected to the control unit to obtain the engine crankcase humidity; A control unit, electrically connected to the negative pressure generating device, to control the rotation speed of the negative pressure generating device; Electrically connected to the solenoid valve to control the opening and closing of the solenoid valve; The control unit controls the negative pressure generating device to generate negative pressure according to the engine operating state and the external ambient temperature, so that the engine crankcase blowby gas flows out; The control unit controls the opening and closing of the solenoid valve according to the engine operating state, external ambient temperature and crankcase humidity, and introduces dry air until the engine crankcase humidity is below the set value and the solenoid valve is closed; when the engine is stopped and the external ambient temperature is lower than the first preset temperature value T1, if the engine crankcase humidity is greater than the first preset humidity value HUM1, the negative pressure generating device and the solenoid valve are turned on until the engine crankcase humidity is less than the first preset humidity value HUM1, and the negative pressure generating device and the solenoid valve are closed.

7. The system for eliminating water vapor condensation in the engine crankcase according to claim 6, characterized in that: The range of the first preset temperature value T1 is 0° C. to 5° C.; the range of the first preset humidity value HUM1 is 40% to 95%.

8. The system for eliminating water vapor condensation in the engine crankcase according to claim 6, characterized in that: When the engine is running, if the external ambient temperature is greater than -25°C, the negative pressure generating device is turned on and the solenoid valve is closed; if the external ambient temperature is less than -25°C, the negative pressure generating device and the solenoid valve are turned on.

9. The system for eliminating water vapor condensation in the engine crankcase according to claim 8, characterized in that: The system also includes a crankcase pressure sensor and a crankcase temperature sensor electrically connected to the control unit; the crankcase pressure sensor is used to measure the crankcase pressure, and the crankcase temperature sensor is used to measure the crankcase temperature; when the external ambient temperature is less than -25°C, the dew point humidity X of water vapor condensation at this time is calculated according to the engine crankcase pressure and temperature, the negative pressure generating device and the solenoid valve are turned on, and the engine crankcase humidity is controlled to be lower than the dew point humidity X until the engine stops, and the solenoid valve is closed.

10. The system for eliminating water vapor condensation in the engine crankcase according to claim 6, characterized in that: The negative pressure generating device is an electrically driven centrifugal separator. The negative pressure at the engine crankcase outlet is adjusted by adjusting the rotation speed of the electrically driven centrifugal separator. The higher the rotation speed, the greater the negative pressure.

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