Sheet Metal · 2022年9月8日

Improper installation position of the breathing tube of the crankcase of the ND2 locomotive diesel engine

 

Tests on locomotives with crankcase explosions and further expansion to all ND2 locomotives in the entire section show that there is a higher pressure in the crankcase when the diesel engine is working normally. For example, when the ND2157# locomotive went online for testing, the oil and gas pressure in the crankcase was as high as 1.47MPa. When the ND2 locomotive diesel engine works under high load conditions, the temperature of the oil and gas in the crankcase is generally around 90°C, while the temperature of the exhaust gas in the exhaust box is as high as 500°C or more. Especially when the combustion state of the diesel engine is poor, the exhaust gas temperature is higher, which can reach 600-700°C. Although the high-speed exhaust gas flow in the exhaust box has a certain gas diversion effect on the breathing tube installed in it, because the temperature of the exhaust gas is too different from the temperature of the oil and gas, it is very easy to cause the high-temperature exhaust gas to flow back into the crankcase through the breathing tube. .

ND2 locomotive diesel engine crankcase breathing tube is installed improperly, not only can not effectively exhaust, but will cause the oil and gas pressure in the crankcase to rise due to the backflow of high-temperature exhaust gas. Improvement measures (1) Change the arc-shaped thin steel plate of the explosion-proof valve to flat thin steel plate, so that not only the upper and lower ends, but also the left and right sides of the explosion-proof valve can be closely attached to the surrounding rectangular hole of the intermediate body of the explosion-proof valve to improve its sealing performance . And when the explosion-proof valve is activated, the flat thin steel plate can also return to its original position. (2) Change the installation position of the crankcase breathing tube, change the breathing tube upwards to pass through the locomotive roof directly to the atmosphere, and install a rain cover on the exhaust port. In this way, not only the “backflow” problem is completely solved, but the airflow induction effect generated by the air sweeping over the exhaust port when the locomotive is running can still be used to pump air to the crankcase through the breathing tube to reduce the pressure in the box. The Nanchang Locomotive Depot conducted the above-mentioned reorientation and loading test on the exhaust ports of the crankcase breathing tubes of two ND2 locomotives, and achieved satisfactory results. (3) Install diesel engine crankcase overpressure automatic stop device. The device is composed of electrical and mechanical parts. When the pressure in the tank reaches a certain set value, it can promptly alarm and stop the diesel engine. The electrical part consists of a differential pressure control circuit, an alarm control circuit and a shutdown control circuit. There is a certain amount of conductive fluid in the U-shaped differential pressure gauge. The test tube connected to the test end is connected to the oil and gas separator of the crankcase of the diesel engine, and the vent tube at the vent end is in communication with the atmosphere.

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