Effects of crankcase ventilation When the engine is working, there is always a part of the combustible mud gas and exhaust gas that escapes into the crankcase through the piston rings. The gasoline vapor that escapes into the crankcase condenses and will thin the engine oil and worsen its performance. The exhaust gas contains water vapor and sulfur dioxide. The water vapor condenses in the engine oil to form foam, damaging the engine oil supply. This phenomenon is especially serious in winter; sulfur dioxide reacts with water to form sulfurous acid, and sulfurous acid forms sulfuric acid when it encounters oxygen in the air. These acidic substances The appearance of oil not only deteriorates the engine oil, but also causes parts to be corroded. As combustible mud gas and exhaust gas escape into the crankcase, the pressure in the crankcase will increase, and the oil will leak out from the crankshaft oil seal, crankcase liner, etc. The oil vapor lost into the atmosphere will increase the pollution of the engine to the atmosphere. The engine crankcase ventilation device can prevent or reduce the above phenomenon. Therefore, the functions of the engine crankcase ventilation device are: 1. Prevent the deterioration of the engine oil; 2. Prevent the leakage of the crankshaft oil seal and crankcase liner; 3. Beware of various oil vapors polluting the atmosphere.
2. Forms and characteristics of crankcase ventilation 1. Natural ventilation The gas extracted from the crankcase can be directly introduced into the atmosphere. This ventilation method is called natural ventilation. This ventilation system is relatively simple in structure and easy to operate, but the combustible mixed gas and oil vapor introduced into the atmosphere can easily pollute the atmosphere. Therefore, it is not widely used in modern engines. According to the method of introducing air into the atmosphere, ventilation has ordinary type and respirator type. (1) Popular style The oil vapor in the crankcase is directly exposed to the atmosphere through the oil filler port of the oil pipe. This ventilation method does not require special mechanical parts. Various oil vapors are directly discharged into the atmosphere, causing pollution to the atmosphere. Therefore, it is suitable for internal combustion engines on some fatigue machines used in rural areas with low requirements. . (2)Respirator type The oil vapor in the crankcase is exposed to the atmosphere through a breather-type device. This kind of respirator device is a filtering device that can absorb harmful gases and prevent air pollution. Figure 1 shows the respirator device of the Iveco light bus engine jointly produced by Nanjing Yuejin Group and Italy. The breather is fixed on one side of the cylinder block with bolts. There is an air inlet on the side of the bottom that is similar to the crankcase, and the upper air outlet is connected to the atmosphere with two rubber tubes. There are two layers of filters filled with potted steel wire welded inside the respirator to disperse oil mist. When the engine is working, various gases that rush into the crankcase pass through the air inlet of the respirator; they enter the respirator, are filtered and dispersed by the filter, and finally the clean air is evacuated from the air outlet through the rubber tube. Because there are two layers of filters, the oil mist is partially overhead, which not only ensures the pressure balance in the crankcase, but also prevents the oil vapor in the crankcase from polluting the atmosphere. 2. Forced ventilation The suction function of the engine air intake system is used to suck out the gas in the crankcase. This ventilation method is called forced ventilation. The structure of this ventilation system is somewhat complicated, but it can recycle the combustible muddy gas and exhaust gas that escape into the crankcase, which not only helps improve the economy of the engine, but also reduces the emission pollution of the engine. Therefore, in modern times, It is widely used in automobile engines. According to the mode of sucking the gas in the crankcase, forced ventilation has general type, one-way valve type, oil and gas diffusion type and comprehensive type. (1)General style The ventilation method that uses rubber tubes to connect the crankcase and the intake pipe is normal forced ventilation. This ventilation system has a relatively simple structure. It only needs pipeline connections and no other components are needed in the middle. It is suitable for some small engines. General forced ventilation device for gasoline engine crankcase. The upper part of the air filter is equipped with an air intake hose, which is used to pass into the valve chamber cover. There is an air outlet pipe on the tappet chamber cover that leads to the inlet of the carburetor. When the engine is working, the gas in the crankcase is sucked into the carburetor through the exhaust pipe, and the fresh air filtered by the air filter is replenished into the crankcase through the intake hose and valve cover. (2) One-way valve type: A one-way valve is connected in the pipeline connecting the crankcase and the intake pipe to prevent the oil in the crankcase from being sucked out. It is suitable for automotive gasoline engines, such as EQ6100Q, Japanese Mitsubishi Pajero (Cheetah) automobile engines Think of excellence. Gasoline engine one-way valve crankcase forced ventilation device. A small air filter is installed on the valve cover, which is connected by an outlet pipe between the crankcase and the intake pipe, and a one-way valve is installed at the connection point before entering the intake pipe. When the engine is working, the steam in the crankcase is sucked into the cylinder through the exhaust pipe and the one-way valve, and the fresh air enters the crankcase through the small air filter on the valve chamber cover. The function of the one-way valve is to prevent the vacuum in the intake pipe from being too large and sucking the oil out of the crankcase when the engine is at low speed and low load. The crankcase ventilation check valve is mainly composed of a valve, a valve body, a valve seat and a spring. When the engine is idling, the vacuum in the intake pipe is large, the one-way valve is sucked on the valve seat, and the exhaust gas in the crankcase enters the intake pipe through the small hole on the valve; as the engine load increases, the vacuum in the intake pipe decreases. , the valve is pushed outward under the action of spring force, and the ventilation volume gradually increases; when the engine is under heavy load, the valve is fully opened, and the ventilation volume is large, thus playing the role of renewing the air in the crankcase. (3) Oil and gas diffuser type An oil and gas diffuser is connected in the pipeline connecting the crankcase and the intake pipe to disperse the oil and gas sucked from the crankcase so that the liquid oil flows back to the crankcase and the gaseous gas is sucked into the intake pipe. This can eliminate Oil consumption. The oil and gas diffuser of Steyrzer engine is installed at the front end of the engine cylinder head. When the engine is working, the oil and gas management path that flows into the crankcase enters the oil and gas diffuser. Since the volume of the oil and gas diffuser is inclined, the liquid oil flows back to the crankcase along the inclined plane and the oil return pipe, while the gaseous gas flows back to the crankcase along the inclined plane and the oil return pipe. Keiren is responsible for entering the air intake. (4) Comprehensive In the pipeline connecting the crankcase and the intake pipe, not only a one-way valve is connected, but also an oil and gas diffuser is connected, which greatly reduces the consumption of engine oil and ensures the stability of engine oil lubrication under various working conditions. Comprehensive forced ventilation device for the crankcase of gasoline engines. A crankcase ventilation air inlet filter is installed on the front cover of the cylinder head, and a crankcase ventilation air outlet filter is installed on the rear cover of the cylinder head. The filter has the effect of oil and gas dispersion, so it is also called oil and gas. Diffuser. There is a filter element inside the oil and gas diffuser, and there is a partition on the upper end of the filter element, which makes it effective in diffusing oil and gas; the one-way valve is located on the top of the oil and gas diffuser, which eliminates the effects of high temperature conditions on the valve such as sticking and clogging. When the engine is working, the combustible mixed gas and exhaust gas leaked into the crankcase, under the influence of the vacuum of the intake pipe, pass through the tappet chamber, oil baffle, crankcase ventilation outlet filter, ventilation hose and one-way valve The air entering the engine intake pipe is mixed with strange muddy air, and enters the cylinder and burns out. The strange gas then enters the crankcase through the crankcase ventilation air inlet air filter on the front cover of the cylinder head.
3. Inspection and maintenance of crankcase ventilation 1. Check the pipeline condition (1) Remove the air outlet hose and return hose of the crankcase ventilation device, and remove the relevant components (breather, or one-way valve, or oil and gas diffuser). (2) Check whether the pipeline is flattened, damaged, leaking, etc., then clean it and blow it clean with compressed air. (3) Reinstall in the reverse order of disassembly. 2. Check the condition of the one-way valve In the forced crankcase ventilation device equipped with a one-way valve, focus on checking the one-way valve. If the one-way valve is stuck and kept open or blocked, normal ventilation of the crankcase cannot be guaranteed. When the valve is stuck and clogged, the engine will not have enough ventilation under heavy load, and the oil and gas in the tank will escape into the atmosphere, polluting the environment; when the valve is kept open, the engine's oil consumption will be excessive. (1) Check the vacuum condition of the valve Unscrew the one-way valve on the engine, then connect the ventilation hose, run the engine at idle speed, and place your finger on the opening end of the one-way valve. At this time, your finger should feel a vacuum. If you lift your finger, the valve opening should feel 'Pah, pah' suction sound. If there is no vacuum feeling or sound with your fingers, use cleaning solution to clean the one-way valve and ventilation hose and check again. If still not possible, replace it. (2) Check the activity of the valve Unscrew the one-way valve from the engine and insert a wooden thin rod into the one-way valve. At this time, the valve's plunger should move freely back and forth. If the valve plunger does not move, it should be cleaned or adjusted.
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