Exhaust gas turbochargers of different brands (including Carter, Huiyuan, Garrett, etc.) are widely used in various large and medium-sized diesel trucks, flat transporters, dump trucks and various construction machinery. They enable the diesel engine to significantly increase power and torque, reduce fuel consumption and exhaust pollution, especially in plateau areas, under the condition of unchanged structure and size.

During the working process, the speed of the supercharger is as high as tens of thousands of revolutions per minute, and it operates under high exhaust temperature for a long time, so its working conditions are poor. During the use of the above vehicles, the power drop and fuel consumption rise caused by the improper use of the supercharger have occurred to varying degrees, resulting in a significant decline in operating efficiency and economic benefits. Based on the research on various faults of diesel exhaust turbocharger in engineering practice, the author makes the following discussion on the causes of common faults and preventive measures.

1. Correct use of diesel engine

First of all, the quality grade of diesel engine oil. For low supercharged diesel engines, diesel engine oil not lower than CC grade should be selected; For medium turbocharged diesel engines, diesel engine oil not lower than CD grade shall be selected. Secondly, the viscosity grade of diesel engine oil should be selected according to the temperature condition and the wear condition of engine parts.

Thirdly, the cleanness of diesel engine oil, because the rotor shaft of the exhaust gas turbocharger and its bearing (shaft sleeve) are closely matched. If the diesel engine oil is too dirty or deteriorated, impurities or abrasive particles will be brought into the turbocharger. The light is to accelerate bearing wear, and the heavy is to prevent the formation of lubricating oil film, which will cause the rotor shaft and bearing to bite. Therefore, it is necessary to keep the engine oil clean, clean the engine oil filter of Beiben V3 accessories frequently, and replace the deteriorated and failed engine oil in time.

2. Correct cold start method

After the vehicle is started, the diesel engine should be allowed to idle for a few minutes (depending on the engine temperature and the ambient air temperature), the standby oil should reach a certain temperature and pressure, the flow performance should be improved, and the turbocharger bearing should be fully lubricated before the speed can be increased, and the vehicle can be started or put into operation, which is particularly important when the ambient air temperature is low.

For vehicles that have been parked for a long time (such as more than a few days), loosen the supercharger oil inlet connector before starting, and fill the oil inlet with an appropriate amount of oil of the same brand as the oil pan to prevent the rotor shaft from burning due to poor lubrication during starting. Some users have had similar situations on the dump truck of the liberation project king and on the grader, which should be avoided as much as possible.

3. Correct flameout method

If the diesel engine running at high speed suddenly stalls, the oil in the exhaust turbocharger will stop circulating immediately due to the stop of the oil pump, but the rotor shaft of the turbocharger is still rotating at high speed under the inertia, which is easy to be burnt out with its bearings due to the oil cut-off.

In addition, the temperature of the exhaust manifold of the diesel engine running under load is very high. If it suddenly stops running, the heat will be transferred to the supercharger housing, and the oil that has stopped flowing will be boiled into carbon deposits. When the carbon deposit is more and more, it will also block the oil inlet, causing the bearing to lack oil. Even if the oil inlet is not blocked, the carbon deposit will also accelerate the bearing wear.

For this reason, make sure that the load of the diesel engine is gradually reduced before flameout, and finally idle for an appropriate time. After the speed of the turbocharger rotor shaft decreases and the oil temperature decreases, flameout and stop. After flameout, the supercharger rotor shaft will continue to idle for a certain time, and sometimes a slight "buzzing" sound can be heard.

4. Correct operation of diesel engine during operation

① Maintain the normal operating temperature of the supercharger. When the supercharger is working, the normal temperature of the turbine casing is about 400 ℃, and the temperature of the compressor casing should not be too hot. In use, if the diesel engine supplies too much oil, the oil supply time is too late, the supercharger is overloaded for a long time, or the throttle is often slammed, the supercharger will overheat and wear will be aggravated due to the high exhaust temperature.

If the oil seal at the turbine end fails, the oil in the turbocharger flows into the turbine housing and is discharged with the high-temperature exhaust gas discharged from the cylinder, resulting in excessive oil consumption and smoke in the exhaust pipe. If the oil seal at the compressor end fails, the oil in the supercharger will flow into the compressor housing, and as the intake air is sucked into the cylinder for combustion, it will also cause excessive oil consumption, exhaust smoke, and increased carbon deposition in the cylinder.

② Maintain normal lubrication system oil pressure. When the diesel engine is running and the oil pressure of the lubricating system is lower than 015MPa, it should be stopped for inspection to prevent the rotor shaft and bearing from being burnt by the poor lubrication of the supercharger. The oil pressure should not be too high to prevent oil from entering the turbine chamber or compressor chamber. The idling time of the diesel engine at low speed shall not be too long to prevent the turbocharger from being poorly lubricated due to low oil pressure.

③ Strengthen the maintenance of air filter. To make the diesel fuel injected into the cylinder fully burn, a large amount of clean air needs to be supplied. After the diesel engine is equipped with a supercharger, the fuel supply of the fuel injection pump will be increased accordingly. If the air filter is blocked and the intake is insufficient, the power of the diesel engine will be significantly reduced. Therefore, the maintenance of air filter should be strengthened to ensure its normal working condition.

In addition, if the filter element of the Beiben V3 accessory filter is damaged or the sealing rubber ring is aged and fails, the supercharger will rotate unsteadily due to the invasion of sand, and the noise will be increased, which will lead to increased wear of the bearing, oil seal and gas seal components. It should be noted that when the air filter is empty for maintenance, do not let hard objects fall into the intake pipe, so as to avoid breaking the impeller or breaking the rotor shaft after the supercharger is inhaled, which may also cause cylinder pulling accident.

5. Proper maintenance of supercharger

During use, the bolts between the three housings of the supercharger should be checked and tightened frequently to eliminate oil and gas leakage. After the diesel engine works for 500~1000h, remove the supercharger, check whether the rotor rotates flexibly, and whether there is carbon deposit at the inlet and outlet of the supercharger, and carefully clean it to ensure that the oil is unblocked. Scrape the tiny dust deposited on the throat of the compressor, clean the scale, gas seal channel and oil cavity in the water interlayer of the intermediate shell, remove the carbon deposit in the turbine, nozzle ring and turbine shell, clean all gas seals and oil seals, check their damage, and replace them if necessary.

When disassembling and assembling the supercharger, because the turbine casing and the compressor casing are thin-walled castings, it is strictly forbidden to hit and collide. When necessary, it should be gently knocked with a wooden hammer, and it is not allowed to use iron tools to prevent damage. The rotor shaft assembly must be in place according to the original mark during assembly to avoid affecting its dynamic balance. During the final assembly, keep clean, and do not let sundries fall into the shell cavity or pipe. The oil inlet and outlet on the intermediate housing shall be installed vertically, and the oil outlet pipe shall be gradually bent to the crankcase after being connected from the supercharger. There shall be no "dead bend" in the middle to prevent the oil from leaking into the turbine chamber or compressor chamber due to the blocked oil return.

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