Improper installation of breathing tube for crankcase of ND2 locomotive diesel engine

Tests of locomotives that have experienced crankcase explosions and further expansion to all ND2 locomotives in the entire segment indicate that there is high pressure in the crankcase during normal engine operation. If the ND2157# locomotive is tested on-line, the oil pressure in the crankcase is as high as 1.47 MPa. When the ND2 locomotive diesel engine is operating under high load conditions, the temperature of the oil and gas in the crankcase is generally about 90°C, and the exhaust gas temperature 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 and 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 therein, since the difference between the exhaust gas temperature and the oil gas temperature is too large, high-temperature exhaust gas can easily flow back into the crankcase through the breathing tube. .

The improper installation of the breathing tube of the crankcase of the ND2 locomotive diesel engine not only fails to exhaust the gas, but also causes the pressure of the oil in the crankcase to rise due to the backflow of the high-temperature exhaust gas. Improvement measures (1) Change the arc-shaped steel sheet of the explosion-proof valve to a flat steel sheet so that not only the upper and lower ends but also the left and right sides can be closely attached around the rectangular hole of the explosion-proof valve intermediate to improve its sealing performance. . And when the explosion-proof valve is activated, the flat steel sheet can return to its original position. (2) Change the installation position of the crankcase breathing tube. Change the breathing tube upwards to the atmosphere through the roof of the locomotive, and install a rain cover on the exhaust port. In this way, not only the problem of “backflow” is completely solved, but also the airflow induced action of the air sweeping through the exhaust port during the operation of the locomotive can be utilized to pump the air through the breathing tube to the crankcase and reduce the pressure inside the box. The Nanchang Locomotive Section carried out the above reloading tests on the exhaust ports of the crankcase breathing tube of two ND2 locomotives and achieved satisfactory results. (3) Install an over-pressure automatic parking device for diesel engine crankcase. The device consists of two parts, electrical and mechanical. When the pressure in the box reaches a certain set value, it can alarm and stop the diesel engine in time. The electrical part consists of differential pressure control circuit, alarm control circuit and shutdown control circuit. A certain amount of conductive liquid is stored in the U-shaped differential pressure gauge. The test tube connected to the test end is connected to the oil-gas separator of the crankcase of the diesel engine, and the vent pipe of the ventilating end is open to the atmosphere.