Exhaust Turbocharger of Diesel Generator Set

Structure and working principle of diesel generator set exhaust turbocharger

The radial exhaust gas turbocharger of a diesel generator or diesel engine is composed of an exhaust gas turbine and a compressor. The compressor on the left and the exhaust gas turbine on the right are coaxial. The intake end of the turbine is connected to the exhaust pipe of the cylinder, and the outlet end is connected to the exhaust port of the diesel engine. The inlet end of the compressor is connected to the air cleaner of the intake port of the compressor is connected to the intake pipe of the cylinder.

1. Exhaust turbine

The exhaust gas turbine is composed of a volute, a nozzle ring and a working impeller. The nozzle ring is composed of a nozzle inner ring, an outer ring, and a nozzle vane. The passage formed by the nozzle vanes is contracted from the inlet to the outlet. The working impeller consists of a turntable and an impeller, and a working blade is fixed on the outer edge of the turntable. One nozzle ring forms an stage with the adjacent working impeller, and only one stage of the turbine is called a single stage turbine, and most of the superchargers use a single stage turbine.

When the diesel engine is working, the exhaust gas flows into the nozzle ring through the exhaust pipe at a certain pressure and temperature. Since the passage area of the nozzle ring is gradually reduced, the flow rate of the exhaust gas in the nozzle ring is increased. The high velocity exhaust gas from the nozzle enters the flow passage in the impeller vane, and the air flow is forced to turn. Due to the centrifugal force, the airflow is pressed against the concave surface of the blade, causing a pressure difference between the concave and convex surfaces of the blade. The resultant force of the pressure difference on all the blades generates an impact moment on the rotating shaft, so that the impeller rotates in the direction of the torque, and then the exhaust gas flowing out from the impeller The turbine center is exhausted from the exhaust port.

2. Compressor

Second, the compressor is mainly composed of the intake port, the working impeller, the diffuser and the volute. The compressor is coaxial with the exhaust turbine and is driven by the exhaust turbine to rotate the working turbine at a high speed. The working turbine is the main component of the compressor. Usually it consists of a forwardly curved wind deflector and a semi-open working wheel. The two parts are mounted on the rotating shaft. Straight blades are arranged radially on the working wheel, and an expanding air flow passage is formed between the blades. Due to the rotation of the working wheel, the intake air is compressed by the action of the centrifugal force, and the outer edge of the working wheel is thrown to increase the pressure, temperature and speed of the air. The air flows through the diffusing action to convert the kinetic energy of the air into pressure energy. In the exhaust volute, the kinetic energy of the air is gradually converted into pressure energy. In this way, the intake density of the diesel engine is significantly improved by the compressor.

Assembly of diesel generator set exhaust turbocharger

1. With the compressor end of the middle casing facing up, insert the spring retaining ring into the inner ring groove of the bearing end of the compressor. Then place the floating bearing with the oil on it and the thrust ring into the other spring retaining ring. When installing a floating bearing, turn the end with the oil groove on the side. After each spring snap ring is installed, check that the snap ring is fully inserted into the ring groove.

2. With the turbine end of the intermediate casing facing up, the spring snap ring, the floating bearing, and the thrust ring are sequentially loaded into the turbine end bearing hole in the same order as in the step 1. When installing the floating bearing, care should be taken to raise the end of the oil groove on the side.

3. Two rings made of thin wire are placed over the fingers, and the two elastic sealing rings are opened and inserted into the turbine rotor shaft seal ring groove.

4. When installing two elastic sealing rings on the turbine rotor shaft, the opening position should be shifted by 180 degrees. Then apply cleaning oil on the sealing ring and carefully insert the rotor into the middle casing to prevent the ring from slipping or breaking from one side. The position of the elastic sealing ring relative to the rotor shaft is centered and guided by the upper tapered surface of the intermediate housing hole.

5. Hold the turbine wheel that has been loaded into the intermediate casing with your hand and clamp the hexagonal shoulder at the turbine impeller to the vise. Take care to prevent the turbine rotor shaft from slipping out of the intermediate casing.

6. Place the thrust piece and the spacer on the shaft, and put the thrust bearing on the cleaning oil. Note that the oil inlet hole above the plane of the thrust bearing should be directed downwards to the oil inlet hole on the middle casing, and then the retaining washer is placed. After tightening the 4 bolts, the retaining washer is flanged and the 4 bolts are locked. Place another thrust piece on the shaft and insert it into the oil retaining plate. Note that the oil guiding tongue on the oil retaining plate must extend into the oil returning chamber.

7. Put the shaft seal that has the elastic sealing ring on the cleaning machine oil and put it into the corresponding seat hole on the end seal plate of the compressor. Before loading, the opening positions of the two rings are staggered so that they are separated by 180 degrees. Put the compressor air-sealing ring into the outer ring groove of the compressure air-sealing plate. In order to facilitate pressing into the middle casing, apply some thin oil on the outer surface of the rubber sealing ring and press it into the middle shell body.

8. After aligning the rotor and the compressor impeller with the dynamic balance mark, put on the compressor impeller, screw the self-locking nut and tighten it until it is aligned with the dynamic balance mark on the shaft end face. When tightening, do not allow the compressor impeller to be opposite to the compressor. The shaft has a rotation.

9. Remove the assembled assembly from the vise and insert it into the leafless volute according to the original mark. Be careful not to skew during assembly, install the turbine end plate and the stop washer, and tighten the hex nut.

10. Install the compressor casing alignment mark into the middle casing. Insert the “V” clamp into the middle casing before assembly, and pay attention to the installation without bending, so as to avoid the arc of the compressor casing from hitting the top of the compressor impeller blade. Install the “V” shaped clamp and tighten the bolts.

11. After injecting the cleaning oil into the oil inlet hole of the middle casing, the impeller should be rotated flexibly by hand.

12. After the final assembly, measure the next two items

A. Measurement of the axial movement of the turbine compressor. Place the iron table with the dial gauge on the plane of the volute flange and the end of the measuring rod of the dial indicator at the hexagonal shoulder plane at the turbine impeller exit. Above, the maximum axial movement is measured by pushing and pulling the rotor shaft by hand, and the value should be less than 0.25mm. If this value is exceeded, the combination of the thrust bearing and the thrust piece should be further checked. This method can be used for the determination that the supercharger has been installed in the unit.

B. After pressing the self-locking nut on the rotor shaft with a finger, measure the minimum clearance between the compressor impeller blade and the compressor casing with a thickness gauge. The clearance should be greater than 0.15mm. If it is less than this value, it should be disassembled and inspected.