Modern diesel engines are basically designed with exhaust gas turbocharging technology, the use of turbochargers, so that the same volume of the machine can get more power, in the diesel engine, turbochargers in the inlet and exhaust channel, therefore, its function is good or bad, the operation of the whole machine plays a crucial role.
In our usual management, can we judge the operation status of the diesel engine through the operation phenomenon of the turbocharger, careful analysis, or we can sum up the different states of the diesel engine through various phenomena.
First, the role and working principle of turbochargers
① Turbocharger uses the energy of the exhaust gas to drive the exhaust gas turbine to rotate, and the exhaust gas turbine drives the coaxial compressor wheel to rotate, improving the intake volume of the diesel engine, so that the diesel engine can have enough air supply in the case of multiple oil supplies, so that the fuel can be fully burned, give full play to the energy of the fuel, and make the machine using the turbocharger more powerful.
② The role of the turbocharger can make the air fuel ratio of the diesel engine in a reasonable range, if the air supply is insufficient, and then increase the fuel, in addition to the black smoke and unburned fuel into the atmosphere, will not produce more power.
Moreover, the phenomenon of insufficient gas supply may also lead to high exhaust temperature of diesel engine, long-term high exhaust temperature, incomplete combustion, exhaust gas can also block the turbine side, reduce the rotor speed, and let the turbocharger enter a vicious cycle.
Two, the components of turbocharger
① The components on the four-stroke diesel engine intake system are supercharger inlet filter screen, muffler, supercharger impeller, diffuser, air cooler, intake manifold and intake valve.
Components on the exhaust system are:
Exhaust valve, exhaust branch pipe, exhaust manifold, exhaust gas turbine, exhaust pipe, exhaust gas boiler, exhaust pipe.
In the diesel engine intake and exhaust system, visible and play a key role in the turbocharger, at the intersection of the intake and exhaust system, the fault phenomenon in the two systems can be reflected in the turbocharger here, therefore, better analysis and understanding of the turbocharger phenomenon, can better manage the diesel engine.
(2) There are a variety of monitoring equipment on the turbocharger, including monitoring turbocharger rotor speed equipment;
The exhaust gas turbine side has the inlet and outlet turbine exhaust temperature meter, and the exhaust gas temperature is higher or lower than the normal value during operation.
After the charging end of the turbocharger, there is a monitoring pressure gauge, and the monitoring pressure gauge value after the air cooler is also higher or lower than the normal value.
Three, turbocharger
Common abnormal phenomena and reason analysis
① The inlet temperature of the exhaust gas turbine is high, the root cause is that the combustion is insufficient, there is a post-combustion phenomenon, and the heat generated by the post-combustion will be converted into the kinetic energy of the rotor, so that the turbocharger rotor speed is higher than the normal value.
In the case of normal intake system, the possible causes are:
Fuel injector atomization is not good, combustion is not sufficient;
High pressure oil pump oil supply timing is not correct, oil supply lag;
The exhaust valve is not strict, there is leakage phenomenon;
Poor fuel quality, insufficient combustion;
The intake system is not normal, the scavenging pressure is low, the air supply is insufficient, the air-fuel ratio is not matched, and the fuel is not completely burned.
② The exhaust gas turbine end temperature is low, the reason is premature combustion or a small amount of fuel combustion, the turbocharger rotor will be due to the lack of kinetic energy of gas and reduce the speed.
Possible causes are:
When the machine starts soon and runs at low load;
The supply time of the high pressure oil pump is advanced, the fuel is burned in advance, and sometimes the cylinder is knocked.
Injector blocked, single cylinder does not spray oil.
③ The scavenging pressure after the supercharger end air cooler is too high, the possible reasons are:
The intake valve is not strict, the compressed air in the cylinder is channeled to the intake manifold, and the sweeping temperature is basically normal;
The seal between the front side and the back side of the air cooler is not strict, and the high pressure gas in the diffuser pipe is funneling into the intake air main, and the sweeping temperature will be slightly higher;
The pressure in front of the air cooler is higher than normal, and the scavenging pressure is higher than normal due to the high speed of the turbocharger rotor.
④ The scavenging pressure after the supercharger end air cooler is too low, the possible reasons are:
The air cooler is dirty and blocked, and the amount of air passing through the air cooler is reduced;
Turbocharger rotor speed is low, the possible reasons are:
Insufficient kinetic energy at turbine end, or rotor bearing wear, high resistance.
⑤ Turbocharger rotor speed is too low, the possible reasons are:
The rotor bearing is damaged and the friction is aggravated.
The nozzle ring is dirty and blocked, and the kinetic energy to drive the turbine is insufficient.
Four, multiple abnormal
The operation state of diesel engine is analyzed under the phenomenon
The scavenging pressure described below refers to the scavenging pressure after the air cooler, assuming that the pressure difference between the front and back of the air cooler is in the normal range, and the air cooler is in normal condition.
The exhaust temperature is high and low, the turbocharger rotor speed is high and low, and the sweeping pressure in the total intake pipe is high and low. The above phenomena can form a variety of combination forms. Below, we will analyze what state the diesel engine is in.
① High exhaust temperature, high turbocharger rotor speed, high scavenging pressure.
The causal relationship between the three phenomena is established, but each phenomenon has its own causes, the main problem is to analyze and solve the problem of high exhaust temperature, because the high exhaust temperature is an important factor affecting the high speed of the turbocharger rotor.
② The exhaust temperature is high, the turbocharger rotor speed is high, the scavenging pressure is low, the phenomenon of high exhaust temperature and the turbocharger rotor speed is high there is a causal relationship, the turbocharger rotor speed is high and the scavenging pressure is low contradictory, you can find the exhaust temperature is high and the scavenging pressure is low that the state is abnormal.
③ The exhaust temperature is high, the turbocharger rotor speed is low, the scavenging pressure is high, this phenomenon is contradictory to each other, to check one by one, first find a correct state, then the opposite state is very likely to be wrong.
④ The exhaust temperature is high, the turbocharger rotor speed is low, the scavenging pressure is low, this phenomenon has a causal relationship between the turbocharger rotor speed is low, the exhaust temperature is high and the turbocharger rotor speed is low, you can first analyze the abnormal contradiction between the two sides, and then find the cause of the problem.
⑤ The exhaust temperature is low, the turbocharger rotor speed is low, and the scavenging pressure is high. This phenomenon has a causal relationship between the first two, but the turbocharger rotor speed is low and the scavenging pressure is high. First of all, the state of the latter two is normal, and then the cause of the abnormal state is analyzed.
⑥The exhaust temperature is low, the turbocharger rotor speed is low, the scavenging pressure is low, the causal relationship between the three is established, but each phenomenon has its own causes, to investigate the influencing factors of each phenomenon one by one, find the abnormal state, and then analyze the cause of the abnormal state.
⑦ Low exhaust temperature, high turbocharger rotor speed, high scavenging pressure, this phenomenon high turbocharger rotor speed and high scavenging pressure has a causal relationship, low exhaust temperature and turbocharger rotor speed is contradictory, to judge the abnormal state of both sides of the contradiction, and then analyze the cause.
⑧The exhaust temperature is low, the turbocharger rotor speed is high, the scavenging pressure is low, this phenomenon is contradictory between the three, to analyze the possible influencing factors of each phenomenon one by one, to find the wrong phenomenon.
Causes and solutions of surge:
① Turbocharger in operation, surge is a more serious abnormal phenomenon, serious surge may damage the turbocharger, surge is generated because when the intake flow channel is blocked, the intake flow is reduced, turbocharger surge will occur, because when the gas flow is reduced to a certain extent, there will be a negative pressure zone at the blade. The gas is strongly shunt on the impeller and diffuser, while producing strong pulsation, and there is gas backflow, resulting in unstable operation of the compressor impeller, compressor vibration, accompanied by wheezing sound and roar.
② When the supercharger surges, you can find the factors that cause insufficient gas supply, in the intake channel, check one by one from the supercharger inlet filter, focus on checking whether the inlet filter and air cooler are dirty and clean.
③ The turbocharger rotor kinetic energy is insufficient, the rotor speed is reduced, the compressor end impeller can not provide enough air due to the low speed, then it is necessary to find the cause of the turbocharger rotor speed reduction, the exhaust gas boiler on the exhaust pipe is dirty and blocked, the turbine speed reduction caused by poor exhaust smoke, clean the outer surface of the heating tube in the exhaust gas boiler, so that the exhaust smoke is smooth;
The nozzle ring on the turbine side is dirty and blocked, and there is not enough exhaust gas to blow the turbine to rotate and slow down the speed. Disassemble the turbocharger, and clean the nozzle ring and exhaust components.
④There is pulsation in the smoke exhaust, resulting in the turbine speed rising and falling, causing the inlet air pulsation at the end of the compressor impeller. The reason is that the oil supply timing of the high pressure oil pump in the fuel system is inconsistent, resulting in the inconsistency of the full degree of combustion and causing the pulsation, which can be solved by adjusting the oil supply timing of the high pressure oil pump.
⑤When the diesel engine changes load, it can also cause smoke pulsation, and it is necessary to reduce the load when the wind and waves are large, avoid flying cars, and avoid sudden increase and sudden reduction of load operation.
The position of the diesel turbocharger is extremely important, and the inlet and exhaust channels are associated with the inlet and exhaust systems by a rotor shaft. Therefore, we can analyze the operating status of the diesel engine by observing a variety of monitoring data of the turbocharger.
Through many years of management experience, learn from relevant knowledge, analyze and summarize the above analysis and judgment methods for peer reference.