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Changes in structural parameters that should be paid attention to when boosting diesel generator sets
Article source:this site | Issuing time：2019-04-22
For a diesel generator set with a high degree of supercharging, its structure may change greatly, and it may even need to be redesigned to adapt to high supercharging. If the body and main parts are to be strengthened in structure, the piston may need to be cooled by oil, and various systems such as oil supply, air distribution, cooling and lubrication must be reconsidered.
For diesel engines with low supercharge, the basic structure of supercharged diesel engines belongs to the same series as non-supercharged diesel engines, which facilitates the organization and production of main components of supercharged and non-supercharged models on the same processing line. In order to meet the requirements of increased diesel engine power after boosting and reduce its mechanical load and thermal load, corresponding changes and adjustments should be made to the thermal parameters, structure, materials and technology of the diesel engine.
Adjust the oil supply system:
In order to adapt to the increase in the intake air volume after boosting and the power requirements, it is necessary to increase the circulating oil supply. Increasing the circulating fuel supply generally takes measures such as increasing the plunger diameter of the fuel injection pump, increasing the fuel supply rate of the fuel injection pump, increasing the fuel injection pressure of the fuel injector and the diameter of the nozzle hole. In order to limit the maximum combustion explosion pressure, after increasing the circulating fuel supply, the fuel injection advance angle of the diesel engine should be appropriately reduced.
Reduce compression ratio and increase excess air coefficient:
In order to reduce the maximum combustion pressure, the compression ratio of supercharged diesel engines is slightly lower than that of non-supercharged diesel engines, usually 1 to 2 units. With the increase of the supercharging degree, the compression ratio can also be appropriately reduced, but it is generally not lower than 12, otherwise it will make the diesel engine cold start difficult.
Increasing the excess air coefficient can reduce the heat load and improve economy. Generally, the excess air coefficient of supercharged diesel engines is increased by about 10% to 30%.
Change the gas phase:
Taking advantage of the favorable conditions that the boosted intake pressure is higher than the exhaust pressure, appropriately changing the gas distribution phase and increasing the overlap angle of the intake and exhaust valves can better cool the combustion chamber and enhance the scavenging of the cylinder, thereby improving Inflate efficiency and reduce thermal load. However, the valve overlap angle should not be too large. Studies have shown that when the valve overlap angle exceeds 80° crankshaft angle, the scavenging effect will not be further improved.
If the overlap angle is too large, it will increase the scavenging air volume, increase the work burden of the compressor, and cause the exhaust gas to flow backwards when the diesel engine is at low speed and low load, which is detrimental to the acceleration and performance of the whole machine; When it is too large, in order to prevent the valve from colliding with the piston, a deep groove should be dug on the top of the piston to worsen the combustion of the diesel engine.
4. Improve the intake and exhaust system:
After the diesel engine is pressurized, due to the increase in the intake air volume, the increase in the intake resistance and pressure fluctuations, the cross-sectional area of the intake pipe should be increased. For the pulse supercharging system, the exhaust pipe must be branched so that the exhaust of each cylinder will not interfere with each other during scavenging. The principle of branching is that the exhaust of each cylinder connected by an exhaust pipe must not overlap each other or overlap very little.
5. Appropriately change the cooling water circuit and lubricating oil circuit:
After the diesel engine is pressurized, measures should be taken to appropriately adjust the water pump capacity, increase the speed of the water pump, increase the heat dissipation area of the cooling water tank, increase the diameter of the fan, change the blade angle of the fan, and increase the fan speed to reduce the heat load; Oil pump capacity, increase the heat dissipation area of the oil cooler and improve crankshaft ventilation conditions, etc.
For diesel engines with low supercharge, the basic structure of supercharged diesel engines belongs to the same series as non-supercharged diesel engines, which facilitates the organization and production of main components of supercharged and non-supercharged models on the same processing line. In order to meet the requirements of increased diesel engine power after boosting and reduce its mechanical load and thermal load, corresponding changes and adjustments should be made to the thermal parameters, structure, materials and technology of the diesel engine.
Adjust the oil supply system:
In order to adapt to the increase in the intake air volume after boosting and the power requirements, it is necessary to increase the circulating oil supply. Increasing the circulating fuel supply generally takes measures such as increasing the plunger diameter of the fuel injection pump, increasing the fuel supply rate of the fuel injection pump, increasing the fuel injection pressure of the fuel injector and the diameter of the nozzle hole. In order to limit the maximum combustion explosion pressure, after increasing the circulating fuel supply, the fuel injection advance angle of the diesel engine should be appropriately reduced.
Reduce compression ratio and increase excess air coefficient:
In order to reduce the maximum combustion pressure, the compression ratio of supercharged diesel engines is slightly lower than that of non-supercharged diesel engines, usually 1 to 2 units. With the increase of the supercharging degree, the compression ratio can also be appropriately reduced, but it is generally not lower than 12, otherwise it will make the diesel engine cold start difficult.
Increasing the excess air coefficient can reduce the heat load and improve economy. Generally, the excess air coefficient of supercharged diesel engines is increased by about 10% to 30%.
Change the gas phase:
Taking advantage of the favorable conditions that the boosted intake pressure is higher than the exhaust pressure, appropriately changing the gas distribution phase and increasing the overlap angle of the intake and exhaust valves can better cool the combustion chamber and enhance the scavenging of the cylinder, thereby improving Inflate efficiency and reduce thermal load. However, the valve overlap angle should not be too large. Studies have shown that when the valve overlap angle exceeds 80° crankshaft angle, the scavenging effect will not be further improved.
If the overlap angle is too large, it will increase the scavenging air volume, increase the work burden of the compressor, and cause the exhaust gas to flow backwards when the diesel engine is at low speed and low load, which is detrimental to the acceleration and performance of the whole machine; When it is too large, in order to prevent the valve from colliding with the piston, a deep groove should be dug on the top of the piston to worsen the combustion of the diesel engine.
4. Improve the intake and exhaust system:
After the diesel engine is pressurized, due to the increase in the intake air volume, the increase in the intake resistance and pressure fluctuations, the cross-sectional area of the intake pipe should be increased. For the pulse supercharging system, the exhaust pipe must be branched so that the exhaust of each cylinder will not interfere with each other during scavenging. The principle of branching is that the exhaust of each cylinder connected by an exhaust pipe must not overlap each other or overlap very little.
5. Appropriately change the cooling water circuit and lubricating oil circuit:
After the diesel engine is pressurized, measures should be taken to appropriately adjust the water pump capacity, increase the speed of the water pump, increase the heat dissipation area of the cooling water tank, increase the diameter of the fan, change the blade angle of the fan, and increase the fan speed to reduce the heat load; Oil pump capacity, increase the heat dissipation area of the oil cooler and improve crankshaft ventilation conditions, etc.
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