Inspection and replacement judgment of the parts of turbocharger
  • Automotive

Turbocharger is the most effective measure to improve engine power and improve economy. It is also an inevitable way for engine strengthening. It has been widely used in large horsepower tractors and combined harvesters. However, in actual use, the turbocharger often causes early damage due to improper maintenance, resulting in engine power degradation, exhaust pipe black smoke or blue smoke and so on. In the repair and maintenance of turbocharger, many repairmen do not understand the working principle and structural characteristics of turbocharger, disassemble and unload and replace the parts blindly, and cause the performance decline of turbocharger. Since some of the important parts of the turbocharger are high temperature resistant materials, such as the turbine is ceramic alloy, the replacement of the new parts is all used in the maintenance. Which parts need to be replaced and which parts do not need to be replaced are evaluated by many aspects, such as ablation, abrasion, deformation and geometric size error. Because of the geometric size error of different turbochargers, the assembly gap is different, so the inspection and replacement judgment here is based on the visual inspection. The bearing of turbocharger usually adopts floating bearing or rolling bearing. High speed turbocharger has been using highly reliable floating bearings. There is a gap between floating bearing and rotor journal and middle bearing housing. In turbocharger operation, the rotor shaft and floating bearing are all floating in lubricating oil, and there is no mechanical friction between them. The lubrication between the rotor shaft and the bearing of the turbocharger is lubricated by pressure. The lubricating oil comes from the main oil channel of the engine and is filtered through the filter to enter the intermediate shell of the turbocharger. If the oil is dirty or deteriorated in use, the floating bearing is not easy to form oil film, and the bearing is easily scratched in the semi dry friction, even overheating makes the bearing deformed or bluing. It must be replaced if there is any scratch, deformation or bluing after disassembly. When checking the floating bearing in the middle of the turbocharger, it is necessary to dredge the inlet and outlet of the turbocharger lubricating oil, replace the oil filter core, and add the standard oil. When the turbocharger works, if the oil supply is sufficient, the thrust bearing plate generally does not wear out, but if the oil is dirty or deteriorated, it is easy to block the hole into the oil hole, forming semi dry friction, producing wear and deformation, and changing the situation after disassembly. If there is a light scratch on the inlet of the air compression engine shell, the small burrs and marks on the shell can be grinded with fine sand cloth, and if the inlet of the pressurized face of the air compressor shell has a deep scratch, it can not be used. If there is any crack or deformation in the compressor housing, it should be scrapped. The function of the turbine casing is to collect the air from the diffuser pipe and lead it to the compressor outlet. The air continues to decelerate and pressurized in the volute and complete the process from kinetic energy to pressure energy. Visually check whether the turbine shell is grinded with the impeller, check the cracks on the flange and the V hoop. Check whether there are cracks at the inlet end of the turbine shell, whether there is deformation and burning loss on its import and export, such as cracks, deformation, burning loss, corrosion and so on. Under normal circumstances, after the tractor farm operation or transportation mileage of 5~6 km, the turbine and bearing seals should be replaced. Check the cracks in the bearing housing at the oil intake and the oil back joint; measure the bore diameter of the bearing shell; measure the bearing shell length from the exit of the air compressor shell to the outlet of the turbine shell at 4 equal distance; if the measurement results show that the bearing shell is distorted, the bearing shell should be scrapped. Check the crack, surface roughness and deformation of the oil seal plate. If there is any damage, it should be replaced. When the turbocharger is operated, the seal ring has dry friction with the related moving parts, and it is bound to produce wear. If it is not disassembled, the seal can be sealed reliably. It is difficult to recover and reduce the seal. Therefore, it must be replaced. The thickness of the sealing ring can be measured after dismantling to check wear. The new sealing ring can be loaded into the tank. If the clearance is more than 0.23 mm, the oil seal sleeve should be scrapped. The floating bearing retaining ring is a fragile seal. Once it is dismantled, it must be replaced. The impeller of air compressor consists of blades, wheels, roulette and wheel covers. When it is rotated, the air is compressed and flung to the edge of the working wheel under the action of centrifugal force, so that the kinetic energy of the air is increased, and the pressure, velocity and temperature of the air are increased. The air compressor impeller is made of aluminum alloy and fixed on the rotor shaft with nuts. If there are cracks on the blades, cracks or traces of scratches with the compressed shells, special coloring solution can be used to check the cracks. The blades and roulette of the turbine are cast together in a precise way, and the shape of the blade is usually parabolic or two times curved. As the turbine works under the impact of high temperature, high speed and corrosive gas, it requires high strength, high temperature resistance and corrosion resistance, and is often used for casting heat resistant alloy steel. Generally, the turbine and the rotor shaft are welded together. The damage of the seal ring groove should be checked during the inspection. Small grooves or scars are permitted, but no deep grooves are allowed. Lapping with fine sand cloth before the latest use. Check the notch on the turbine thrust shoulder; check the cracks on the turbine impeller with special dyeing solution. If the turbine impeller has cracks, the overall achievement can not be used. After a period of time operation, the surface of the rotating shaft generally has to produce high temperature discoloration, the bearing part is worn, so long as the shaft neck and the gap are within the specified range, there is no obvious scratch and groove, still can be used. If the "V" hoop is not damaged, it can be cleaned and used again. As long as the axial movement gap is within the prescribed range, the thrust plate is not scratched and the step grooves can still be used. The inner bore of the floating bearing of the bearing body will not wear due to sufficient oil supply, so long as there is no obvious scratch after disassembly, there is no need to replace it.