Natural gas engine crankcase ventilation system

Abstract

The natural gas engine crankcase ventilation system comprises an oil-gas separator, the oil-gas separator is provided with a blow-by inlet, a filtering module, an oil return opening and a pressure regulating valve, and a first one-way valve and a second one-way valve are arranged in the oil-gas separator; the first one-way valve is communicated with an air inlet pipe of an engine; the second one-way valve is communicated to an inlet of a compressor of the supercharger; the first one-way valve and the second one-way valve have different opening pressures, and through selective opening of the first one-way valve and the second one-way valve based on the opening pressures, crankcase oil-gas separation and circulation of an engine under different load working conditions are achieved. According to the system, through intelligent switching of the first one-way valve and the second one-way valve, differential ventilation paths that blow-by gas is directly connected with the gas inlet pipe during low load and is connected into an inlet of a supercharger gas compressor during high load are achieved, through the working condition self-adaptive design, the oil and gas circulation efficiency is improved under all working conditions, the low-load combustion stability is guaranteed, and the oil and gas circulation efficiency is improved. And the smoothness of high-load power output is enhanced.

Description

Technical Field

[0001] This invention relates to the field of engine technology, and in particular to a crankcase ventilation system for a natural gas engine. Background Technology

[0002] The crankcase ventilation system is a crucial subsystem for maintaining normal engine operation, its core function being the effective management of blow-by gases within the crankcase. During engine operation, piston ring leakage is inevitable, allowing unburned fuel, oil vapor, and exhaust gases to mix into the crankcase. If these blow-by gases cannot be expelled in time, crankcase pressure will continuously rise. This will damage the engine's sealing structure, causing oil leakage and accelerating wear on the piston rings and cylinder walls, severely impacting the engine's mechanical reliability and lifespan. Furthermore, directly venting the oil vapor carried in the blow-by gases not only wastes oil but also causes serious environmental pollution. Therefore, the crankcase ventilation system must utilize an oil-gas separator to recover oil and reintroduce combustible gas components into the intake system for recirculation, thus balancing engine reliability, fuel economy, and environmental friendliness. However, most existing natural gas engine crankcase ventilation systems adopt a single-pass design architecture, that is, the oil-gas separator is connected to the intake pipe or a certain part of the turbocharger through only one fixed pipeline. This design cannot respond to the differences in intake characteristics under different engine load conditions.

[0003] The different operating conditions of a natural gas engine (such as low-load idling and high-load full-speed operation) will produce drastically different pressure characteristics in the intake system: under low-load conditions, the engine intake volume is small, and a high negative pressure environment is easily formed in the intake manifold; while under high-load conditions, after the turbocharger starts, its compressor inlet will generate a significant negative pressure, and the magnitude, timing, and response characteristics of the negative pressure differ significantly between the two conditions. Existing single-path ventilation systems lack the ability to adapt to different operating conditions. Under low load conditions, insufficient negative pressure in the intake manifold may lead to reduced oil-gas separation efficiency and an increase in the amount of oil carried in blow-by, resulting in oil waste and increased pollutant emissions due to oil participating in combustion; under high load conditions, the dynamic changes in the negative pressure at the turbocharger compressor inlet may make it impossible to accurately control the crankcase pressure, leading to crankcase pressure fluctuations, interfering with engine combustion stability, and reducing the smoothness of power output. Under long-term operation, this technical defect leads to persistently high engine oil consumption, excessive emissions, reduced fuel economy, and even shortened engine lifespan, severely hindering performance breakthroughs in the fields of high efficiency and environmental protection for natural gas engines. Therefore, developing a ventilation system that can adapt to different load conditions and achieve efficient oil-gas separation and precise crankcase pressure regulation has become a critical technical problem urgently needing to be solved in the field of natural gas engines.

[0004] The above background information is provided only to aid in understanding the concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0005] The purpose of this invention is to propose a crankcase ventilation system for a natural gas engine, which can adapt to different load conditions of a natural gas engine and achieve efficient oil-gas separation and crankcase pressure regulation.

[0006] Therefore, the present invention proposes a crankcase ventilation system for a natural gas engine.

[0007] Preferably, the present invention may also have the following technical features:

[0008] A crankcase ventilation system for a natural gas engine includes an oil-gas separator. The oil-gas separator has a blow-by inlet, a filter module, an oil return port, and a pressure regulating valve. The oil-gas separator has a first check valve and a second check valve inside. The first check valve is connected to the engine intake manifold. The second check valve is connected to the turbocharger compressor inlet. The first check valve and the second check valve have different opening pressures. By selectively opening the two valves based on the opening pressure, the oil-gas separation and circulation in the crankcase of the engine under different load conditions can be achieved.

[0009] Preferably, the opening pressures of the first check valve and the second check valve are independently adjusted by the pressure regulating valve to regulate the crankcase pressure.

[0010] Preferably, the opening pressure of the first check valve is higher than that of the second check valve.

[0011] Preferably, the opening pressure of the first check valve is adapted to the negative pressure range of the intake manifold under low engine load conditions, and the opening pressure of the second check valve is adapted to the negative pressure range of the turbocharger compressor inlet under high engine load conditions.

[0012] Preferably, when the engine is under low load, the second one-way valve is closed and the first one-way valve is open, and the separated gas enters the intake manifold through the first one-way valve to participate in the combustion cycle.

[0013] Preferably, when the engine is under high load, the first one-way valve is closed and the second one-way valve is open. The separated gas enters the compressor inlet of the turbocharger through the second one-way valve, and after being pressurized, it enters the intake manifold to participate in the combustion cycle.

[0014] Preferably, the first check valve and the second check valve are diaphragm check valves or ball valve check valves.

[0015] Preferably, the filter module is used to separate engine oil from the oil vapor, and the separated engine oil flows back into the engine through the oil return port.

[0016] Preferably, the filter module has a primary filter layer, a secondary filter layer and an oil collection tank arranged sequentially along the airflow direction inside.

[0017] Preferably, the pressure regulating valve is a spring-loaded pressure regulating valve, which has two independent pressure regulating components inside. The two components are respectively matched with the first check valve and the second check valve. By adjusting the preload of the corresponding pressure regulating components, the opening pressure of the first check valve and the second check valve can be independently and precisely controlled.

[0018] The beneficial effects of this invention compared to the prior art include:

[0019] 1. The ventilation system of the present invention adopts a dual-passage design of "first one-way valve connected to the intake pipe and second one-way valve connected to the compressor inlet of the turbocharger" and combines the gradient setting of the differential opening pressure of the two to achieve automatic adaptation to low / high load conditions of the engine. Under low load, the first one-way valve is opened by the weak negative pressure of the intake pipe, and under high load, the second one-way valve is triggered by the strong negative pressure of the compressor inlet. This avoids the problems of "low load gas leakage and stagnation, and high load excessive pressure" of the traditional single-passage ventilation system, stabilizes the crankcase pressure in the ideal range, and effectively prevents risks such as oil leakage and seal damage.

[0020] 2. The selective opening logic of the dual one-way valves in this invention ensures that the separated blow-by gas (including unburned natural gas) can efficiently participate in the combustion cycle under different operating conditions: at low loads, it is directly combusted with the fresh air in the intake manifold; at high loads, it is fully combusted after being pressurized by the turbocharger, avoiding energy waste and environmental pollution caused by direct emission of blow-by gas. Simultaneously, the efficient discharge of blow-by gas reduces the condensation of oil vapor in the crankcase, and combined with the oil recovery function of the filter module, further reduces the engine oil consumption rate.

[0021] 3. This invention integrates the oil-gas separator, dual one-way valves, and pressure regulating valve into a single design, which is bolted to the outside of the engine cylinder head cover. The compact structure and small footprint allow for installation without significant modifications to existing engines. Furthermore, the pressure regulating valve's adjustment mechanism (such as the adjusting screw) and the tiered filter layer of the filter module are easy to disassemble and clean. The standardized selection of the one-way valves also reduces future maintenance costs, making it highly practical for engineering applications. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall layout of a specific embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the structure of an oil-gas separator according to a specific embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of a specific embodiment of the present invention under low-load conditions.

[0025] Figure 4 This is a schematic diagram of a high-load operating condition in a specific embodiment of the present invention.

[0026] Explanation of reference numerals in the attached diagram: 1-Oil-gas separator; 11-Blow-by inlet; 12-Filter module; 13-Oil return port; 14-Pressure regulating valve; 15-First check valve; 16-Second check valve; 2-Intake pipe; 3-Cylinder head cover; 4-First pipeline; 5-Second pipeline. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to specific embodiments and the accompanying drawings. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope or application of the present invention.

[0028] Non-limiting and non-exclusive embodiments will be described with reference to the following figures, wherein the same reference numerals denote the same parts unless otherwise specifically stated.

[0029] A natural gas engine crankcase ventilation system, such as Figures 1-4As shown, the system includes an oil-gas separator 1, which is the core component of the crankcase ventilation system of the natural gas engine. It has a hollow cavity structure and is bolted to the outside of the engine cylinder head cover 3. The oil-gas separator 1 includes a blow-by inlet 11, a filter module 12, an oil return port 13, and a pressure regulating valve 14. The oil-gas separator 1 contains a first one-way valve 15 and a second one-way valve 16. The first one-way valve 15 is connected to the engine intake pipe 2; the second one-way valve 16 is connected to the turbocharger compressor inlet. The first one-way valve 15 and the second one-way valve 16 have different opening pressures. By selectively opening these two valves based on their opening pressures, the oil-gas separation and circulation in the crankcase under different load conditions of the engine can be achieved. Specifically, the blow-by inlet 11 is located at the joint surface between the oil-gas separator 1 and the cylinder head cover 3. The blow-by inlet 11 is connected to the engine crankcase through an internal channel to ensure that the blow-by gas (including unburned natural gas, oil vapor and a small amount of exhaust gas) in the crankcase can directly enter the interior of the oil-gas separator 1. The filter module 12 is located at the inlet end of the cavity of the oil-gas separator 1 (adjacent to the blow-by inlet 11). The oil return port 13 is located at the bottom of the oil-gas separator 1 and is connected to the filter module 12. The first check valve 15 is connected to the engine intake pipe 2 through the first pipeline 4, and the second check valve 16 is connected to the turbocharger compressor inlet (not shown in the figure) through the second pipeline 5. The pressure regulating valve 14 is installed on the side wall of the cavity of the oil-gas separator 1, and its output end is connected to the control end of the first check valve 15 and the second check valve 16 respectively. The opening and closing state of the two check valves can be controlled by a preset pressure threshold.

[0030] When the engine is running, crankcase blow-by gas enters the oil-gas separator 1 through the blow-by inlet 11. It first passes through the filter module 12 to complete the oil-gas separation. The filtered oil flows back into the engine through the oil return port 13 to participate in the circulation. The separated gas is selectively guided by the first one-way valve 15 or the second one-way valve 16 according to the engine load conditions (low load / high load), and enters the intake manifold 2 or the turbocharger compressor inlet respectively, and finally participates in the combustion cycle, realizing adaptive ventilation under different operating conditions.

[0031] Specifically, the opening pressures of the first one-way valve 15 and the second one-way valve 16 are independently adjusted by the pressure regulating valve 14 to regulate the crankcase pressure. During engine operation, the crankcase pressure gradually changes due to blow-by gas accumulation. The opening pressure of the one-way valve is essentially the pressure threshold that allows blow-by gas to escape. Only when the crankcase pressure reaches this threshold will the one-way valve open to release gas, thereby reducing the crankcase pressure. Furthermore, the opening pressure of the first one-way valve 15 is higher than that of the second one-way valve 16. For example, the opening pressure range of the first one-way valve 15 is -5 kPa to -1 kPa, and the opening pressure range of the second one-way valve 16 is -20 kPa to -10 kPa, forming a pressure gradient design to adapt to different operating conditions. From a physical perspective, the magnitude of the opening pressure directly corresponds to the negative pressure intensity required to trigger the valve. The opening pressure value of the first one-way valve 15 is closer to atmospheric pressure (-5kPa to -1kPa), and only a relatively weak negative pressure is needed to trigger its opening. In contrast, the opening pressure value of the second one-way valve 16 is more negative (-20kPa to -10kPa), and a stronger negative pressure is required to trigger its opening.

[0032] Specifically, the opening pressure of the first one-way valve 15 is adapted to the negative pressure range of the intake manifold 2 under low engine load conditions. When the engine is under low load conditions, the second one-way valve 16 is closed and the first one-way valve 15 is open, and the separated gas enters the intake manifold through the first one-way valve 15 to participate in the combustion cycle.

[0033] like Figures 1-3 As shown, when the engine is under low load conditions (such as engine speed of 600 r / min to 1000 r / min and load rate below 30%), the throttle opening is small, the engine intake air volume is limited, and a weak negative pressure environment is formed in intake manifold 2 (the value range is -6 kPa to -2 kPa, which is much higher than the negative pressure at the compressor inlet of the turbocharger). Figure 2 The middle arrow indicates the flow direction of the separated gas under low engine load conditions. The opening pressure of the first one-way valve 15 needs to be set to a fixed value within the range of -5kPa to -1kPa during factory calibration or subsequent maintenance via the pressure regulating valve 14 (this value remains unchanged during operation after setting and can only be adjusted specifically through the independent adjustment component of the pressure regulating valve 14, rather than dynamically changing). The core logic for this setting value to precisely match the weak negative pressure of the intake manifold 2 is that "absolute value of negative pressure ≥ absolute value of opening pressure". The numerical range of the weak negative pressure of the intake manifold 2 (-6kPa to -2kPa) completely covers the setting range of the opening pressure of the first one-way valve 15 (-5kPa to -1kPa).

[0034] If the opening pressure of the first one-way valve 15 is set to -5kPa (fixed value) during calibration / maintenance, the absolute value of the negative pressure in the intake pipe 2 is ≤-5kPa (e.g., -6kPa, -5kPa), which meets the opening condition. If it is set to -3kPa (fixed value) during calibration / maintenance, the negative pressure in the intake pipe 2 is ≥-3kPa (e.g., -3kPa, -2kPa), which also meets the opening pressure difference. Even if it is set to the upper limit of the range -1kPa (fixed value), the negative pressure in the intake pipe 2 is -1kPa or -2kPa, which can still meet the requirement of "absolute value of negative pressure ≥1kPa".

[0035] Regardless of how the opening pressure of the first one-way valve 15 is calibrated within the range of -5kPa to -1kPa, the weak negative pressure of the intake manifold 2 can consistently meet the opening conditions. However, the opening pressure of the second one-way valve 16 is -20kPa to -10kPa (also a fixed value after calibration, requiring a stronger negative pressure to trigger). At low loads, the turbocharger compressor is not running, and the inlet negative pressure of the turbocharger compressor is close to atmospheric pressure (the value is much higher than -10kPa, and the absolute value of the negative pressure is much less than 10kPa), which completely fails to meet the opening requirements of the second one-way valve 16. Therefore, the first one-way valve 15 automatically opens under the action of pressure difference, while the second one-way valve 16 remains closed. The gas separated by the filter module 12 enters the intake manifold 2 through the first one-way valve 15, mixes with the fresh air entering through the throttle valve, and is then drawn into the cylinder to participate in combustion. This effectively avoids blow-by and stagnation caused by the small intake volume at low loads, ensuring that the crankcase pressure remains stable within the range of -5kPa to +2kPa.

[0036] Specifically, the opening pressure of the second one-way valve 16 is adapted to the negative pressure range of the turbocharger compressor inlet under high engine load conditions. When the engine is under high load conditions, the first one-way valve 15 is closed and the second one-way valve 16 is open. The separated gas enters the turbocharger compressor inlet through the second one-way valve 16, and after being pressurized, it enters the intake manifold to participate in the combustion cycle.

[0037] like Figure 1 , 2 As shown in Figure 4, when the engine is under high load (e.g., speed above 2500 r / min, load rate above 80%), the turbocharger starts and runs at high speed. Air is drawn in at high speed through the compressor, forming a strong airflow. A strong negative pressure environment is formed in the compressor inlet (the value range is -25 kPa to -15 kPa, corresponding to a negative pressure intensity much stronger than that in the intake manifold). At this time, the throttle is fully open, and due to sufficient air intake, the negative pressure in intake manifold 2 is significantly reduced to -3 kPa to -1 kPa (weak negative pressure state). Figure 4 The middle arrow indicates the direction of gas flow after separation under high engine load conditions.

[0038] The opening pressures of both check valves are set to fixed values ​​via pressure regulating valves during factory calibration or subsequent maintenance (these values ​​remain unchanged during operation and can only be adjusted via their respective independent regulating components). The opening pressure of the first check valve 15 is fixed within the range of -5 kPa to -1 kPa, and the opening pressure of the second check valve 16 is fixed within the range of -20 kPa to -10 kPa. The pressure gradient between the two valves remains constant. The core criterion for opening the second check valve 16 is still "absolute negative pressure ≥ absolute opening pressure." The range of strong negative pressure at the compressor inlet (-25 kPa to -15 kPa) completely covers the set range of the opening pressure of the second check valve 16 (-20 kPa to -10 kPa).

[0039] If the opening pressure of the second check valve 16 is set to -20 kPa (fixed value) during calibration / maintenance, the absolute value of the negative pressure meets the opening condition when the compressor inlet negative pressure is ≤ -20 kPa (e.g., -25 kPa, -20 kPa). If it is set to -15 kPa (fixed value), the strong pressure difference required for opening is also achieved when the compressor inlet negative pressure is ≥ -15 kPa (e.g., -15 kPa, -18 kPa). Even if it is set to the upper limit of the range -10 kPa (fixed value), the requirement of "absolute negative pressure ≥ 10 kPa" can still be met when the compressor inlet negative pressure is -10 kPa or -15 kPa. Regardless of how the opening pressure of the second check valve 16 is calibrated within the range of -20 kPa to -10 kPa, the strength of the strong negative pressure at the compressor inlet can stably trigger the valve to open.

[0040] Although the opening pressure of the first one-way valve 15 (-5kPa to -1kPa, fixed value) partially overlaps with the weak negative pressure of the intake pipe 2 (-3kPa to -1kPa) in numerical terms, the core reason for its closure under high load conditions is the "priority difference in pressure difference between the passages." Fluid always flows towards the passage with a larger pressure difference, which is a basic characteristic of fluid mechanics. Therefore, blow-by gas preferentially chooses the strong negative pressure passage at the compressor inlet, rather than simply a numerical mismatch. If the first one-way valve 15 is calibrated to -5kPa (fixed value): the absolute value of the negative pressure in the intake pipe (1kPa~3kPa) < 5kPa, which cannot overcome the spring preload, and therefore cannot open; if the first one-way valve 15 is calibrated to -3kPa... kPa (fixed value): The negative pressure of intake pipe 2 at -3 kPa seems to reach the opening threshold, but the pressure difference formed by the strong negative pressure (-25 kPa to -15 kPa) at the compressor inlet is much greater than the weak negative pressure of intake pipe 2. The blow-by gas in the crankcase will preferentially flow to the passage of the second one-way valve 16 on the strong negative pressure side, which will greatly weaken the actual pressure difference on both sides of the first one-way valve 15 and make it impossible to form an effective opening force. If the first one-way valve 15 is calibrated to -1 kPa (fixed value): Although the negative pressure of intake pipe 2 at -1 kPa can reach the opening threshold, the second one-way valve 16 has already opened first. The pressure in the crankcase is rapidly reduced by the strong negative pressure, and the pressure difference on both sides of the first one-way valve 15 disappears instantly and cannot maintain the open state.

[0041] In summary, under high-load conditions, the first one-way valve 15 remains closed due to insufficient pressure differential caused by the "strong negative pressure passage preferential diversion," preventing blow-by gas from diverting into the intake manifold and affecting the boost cycle efficiency. Ultimately, the second one-way valve 16 opens stably under the influence of the strong pressure differential, while the first one-way valve 15 remains closed. The gas separated by the filter module 12 enters the turbocharger compressor inlet via the second one-way valve 16, where it is compressed (boosted to 0.2MPa~0.3MPa) along with fresh air. It is then cooled to below 80°C by the intercooler before entering the intake manifold 2, mixing with other intake air, and being drawn into the cylinder for combustion. This ensures that a large amount of blow-by gas can circulate efficiently with the boosted air under high load, preventing problems such as oil leakage and seal damage caused by excessive crankcase pressure, while also ensuring the stability of engine power output.

[0042] In other examples of this embodiment, the first check valve 15 and the second check valve 16 can be either diaphragm-type check valves or ball-type check valves. The diaphragm-type check valve has a nitrile rubber diaphragm (thickness 0.8mm~1.2mm) as its valve core. The diaphragm edge is fixed to the valve seat, and the center is held in place by a spring. When the inlet pressure difference exceeds the opening pressure, the diaphragm is pushed open to form a channel. It has a fast response speed (opening time <50ms), making it suitable for frequent switching under low-load conditions. The ball-type check valve has a steel ball (diameter 5mm~8mm) as its valve core. The steel ball is pressed against the conical valve port by a spring. When the inlet pressure difference reaches the target, the steel ball is lifted. It has excellent sealing performance and is suitable for high-pressure differential environments under high-load conditions. In practical applications, the appropriate check valve diameter (6mm~10mm) can be selected according to the engine displacement (e.g., 6L~12L) to ensure gas flow resistance <2kPa.

[0043] Specifically, such as Figures 1-4 As shown, the filter module 12 is used to separate engine oil from the oil vapor, and the separated engine oil flows back into the engine through the oil return port 13. In some examples of this embodiment, the filter module 12 has a primary filter layer, a secondary filter layer, and an oil collection tank arranged sequentially along the airflow direction. The primary filter layer uses a 100-mesh metal wire mesh to intercept engine oil droplets with a diameter greater than 5μm in the blow-by gas; the secondary filter layer is a porous ceramic filter element that can capture fine engine oil mist droplets with a diameter of 1~5μm; the oil collection tank is arranged around the bottom of the filter module and has a funnel-shaped structure to collect the engine oil separated by the filter module. The lowest point of the oil collection tank is connected to the oil return port 13 through the oil return channel. The oil return port 13 is connected to the engine oil pan or cylinder head oil passage through a rubber hose, so that the collected engine oil flows back into the engine under the action of gravity and crankcase micro-pressure, and re-participates in the lubrication cycle, effectively reducing engine oil consumption.

[0044] In other examples of this embodiment, the pressure regulating valve 14 is a spring-loaded pressure regulating valve, which has two independent pressure regulating components inside. The two components are respectively matched with the first one-way valve 15 and the second one-way valve 16. By adjusting the preload of the corresponding pressure regulating components, the opening pressure of the first one-way valve 15 and the second one-way valve 16 can be independently and precisely controlled. Specifically, each pressure regulating component includes a pressure sensing piston, an adjusting spring, and an adjusting structure. One end of the pressure sensing piston abuts against the valve core of the corresponding one-way valve, and the other end is connected to the adjusting spring. The end of the adjusting spring away from the piston is connected to the built-in adjusting structure (such as an adjusting screw) of the pressure regulating valve. The pressure sensing piston corresponding to the first one-way valve 15 is connected to the blow-by buffer chamber of the oil-gas separator through an independent channel. This chamber directly receives the blow-by gas from the engine crankcase through the blow-by inlet, and its internal pressure is completely consistent with the crankcase pressure. The pressure sensing piston corresponding to the second one-way valve 16 is also connected to the blow-by buffer chamber through another independent channel to ensure that the pressure reference sensed by the two sets of pistons is exactly the same, and to avoid adjustment errors caused by pressure sensing deviation.

[0045] When adjusting the opening pressure of the first one-way valve 15, operate its corresponding adjustment structure. When adjusting clockwise, the compression of the adjusting spring increases, the preload is strengthened, and the first one-way valve 15 requires a higher negative pressure (larger absolute value) to overcome the spring force and open, that is, the opening pressure value decreases (corresponding to a stronger negative pressure requirement). For example, when adjusting from -3kPa to -5kPa, the first one-way valve 15 requires a higher negative pressure to overcome the spring preload and open. When adjusting counterclockwise, the spring preload weakens, the opening pressure value of the first one-way valve 15 increases, that is, the negative pressure requirement weakens. For example, when adjusting from -3kPa to -1kPa, only a weaker intake pipe negative pressure is needed to push the valve open.

[0046] When adjusting the opening pressure of the second check valve 16, operate its corresponding adjustment structure. The principle is the same as that of the first check valve 15: clockwise adjustment reduces the opening pressure of the second check valve 16, corresponding to an increased negative pressure requirement and a higher opening threshold. For example, adjusting from -15kPa to -20kPa requires a stronger compressor inlet negative pressure to trigger opening; counterclockwise adjustment increases the opening pressure, corresponding to a decreased negative pressure requirement and a lower opening threshold. For example, adjusting from -15kPa to -10kPa requires a weaker compressor inlet negative pressure to open the valve.

[0047] By adjusting the two sets of independent components, the opening pressures of the first check valve 15 and the second check valve 16 can be set respectively, ensuring that the opening pressure of the first check valve 15 is always higher than that of the second check valve 16, adapting to the negative pressure requirements of different load conditions, and ultimately achieving precise control of crankcase pressure.

[0048] The working principle of the ventilation system described above is as follows: Crankcase blow-by gas generated during engine operation enters the oil-gas separator 1 through the blow-by inlet 11, and is separated into oil and gas by the filter module 12. The separated oil flows back to the engine for recycling through the oil return port 13. When the engine is under low load (such as idling), a negative pressure is formed in the intake manifold, the second one-way valve 16 is closed, and the first one-way valve 15 is opened. The separated gas enters the intake manifold 2 through the first one-way valve 15 to participate in combustion. When the engine is under high load (such as full speed and full load), a negative pressure is formed at the turbocharger compressor inlet, the first one-way valve 15 is closed, and the second one-way valve 16 is opened. The separated gas enters the turbocharger compressor inlet through the second one-way valve 16, and after being pressurized, enters the intake manifold 2 to participate in combustion. By adjusting the opening pressure of the one-way valves, the crankcase pressure can be precisely controlled to ensure system stability.

[0049] Those skilled in the art will recognize that numerous variations are possible with respect to the above description, and the embodiments and figures are merely for describing one or more specific implementations.

[0050] Although exemplary embodiments of the invention have been described and illustrated, those skilled in the art will understand that various changes and substitutions can be made thereto without departing from the spirit of the invention. Furthermore, many modifications can be made to adapt specific situations to the doctrine of the invention without departing from the central concepts of the invention described herein. Therefore, the invention is not limited to the specific embodiments disclosed herein, but may include all embodiments and equivalents that fall within the scope of the invention.

Claims

1. A crankcase ventilation system for a natural gas engine, comprising an oil-gas separator, wherein the oil-gas separator is provided with a blow-by inlet, a filter module, an oil return port, and a pressure regulating valve, characterized in that: The oil-gas separator is equipped with a first one-way valve and a second one-way valve; the first one-way valve is connected to the engine intake manifold; the second one-way valve is connected to the turbocharger compressor inlet; the first one-way valve and the second one-way valve have different opening pressures, and by selectively opening the two based on the opening pressure, the crankcase oil-gas separation and circulation under different load conditions of the engine can be realized.

2. The natural gas engine crankcase ventilation system according to claim 1, characterized in that: The opening pressures of the first check valve and the second check valve are independently adjusted by the pressure regulating valve to regulate the crankcase pressure.

3. The natural gas engine crankcase ventilation system according to claim 2, characterized in that: The opening pressure of the first check valve is higher than that of the second check valve.

4. The natural gas engine crankcase ventilation system according to claim 3, characterized in that: The opening pressure of the first check valve is adapted to the negative pressure range of the intake manifold under low engine load conditions, and the opening pressure of the second check valve is adapted to the negative pressure range of the turbocharger compressor inlet under high engine load conditions.

5. The natural gas engine crankcase ventilation system according to claim 4, characterized in that: When the engine is under low load, the second one-way valve is closed and the first one-way valve is open. The separated gas enters the intake manifold through the first one-way valve to participate in the combustion cycle.

6. The natural gas engine crankcase ventilation system according to claim 4, characterized in that: When the engine is under high load, the first one-way valve is closed and the second one-way valve is open. The separated gas enters the compressor inlet of the turbocharger through the second one-way valve, and after being pressurized, it enters the intake manifold to participate in the combustion cycle.

7. The natural gas engine crankcase ventilation system according to claim 1, characterized in that: The first check valve and the second check valve are diaphragm check valves or ball valve check valves.

8. The natural gas engine crankcase ventilation system according to claim 1, characterized in that: The filter module is used to separate engine oil from the oil vapor, and the separated engine oil flows back into the engine through the oil return port.

9. The natural gas engine crankcase ventilation system according to claim 8, characterized in that, The filter module contains a primary filter layer, a secondary filter layer, and an oil collection tank arranged sequentially along the airflow direction.

10. The natural gas engine crankcase ventilation system according to claim 1, characterized in that, The pressure regulating valve is a spring-loaded pressure regulating valve, which has two independent pressure regulating components inside. The two components are respectively matched with the first check valve and the second check valve. By adjusting the preload of the corresponding pressure regulating components, the opening pressure of the first check valve and the second check valve can be independently and precisely controlled.

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