The working process of the diesel engine is actually the same as that of the gasoline engine, and each working cycle also experiences four strokes of intake, compression, work and exhaust. However, because the fuel used in diesel engine is diesel, its viscosity is larger than gasoline, it is not easy to evaporate, and its spontaneous combustion temperature is lower than gasoline, so the formation and ignition mode of combustible mixture are different from gasoline engines.
When the fuel supply advance Angle is too large, the fuel is injected in the case of low air temperature in the cylinder, the mixture formation condition is poor, the oil collection before combustion is too much, which causes the diesel engine to work rough, idle speed instability and starting difficulty; Over the hour, the fuel will be generated after combustion, the maximum temperature and pressure of combustion will decrease, the combustion is incomplete and the power will decrease, and even the exhaust will emit black smoke, and the diesel engine will overheat, resulting in reduced power and economy. The optimal fuel advance Angle is not a constant, and should be increased with the change of diesel load (fuel supply) and speed, that is, with the increase of speed. Obviously, the oil supply advance Angle is slightly larger than the oil injection advance Angle. Because the oil supply advance Angle is easy to check and read, it is used more in the production unit and the use department.
If the Angle between the center line and the vertical line of the crankshaft connecting rod journal is too large, that is, the oil supply advance Angle is too large, the piston is further away from TDC, at this time the fuel enters the cylinder, it will burn in advance, generate power, so that the piston does not reach TDC on the decline, then the compression ratio in the cylinder will be reduced, the engine power will also decrease, and the temperature will increase. And there’s a knocking sound inside the cylinder.
Most diesel engines determine the best injection advance Angle under the condition of calibrated speed and full load by test. When the injection pump is installed on the diesel engine, the injection advance Angle is adjusted according to this, and generally no longer changes during the working process of the diesel engine. Obviously, when the diesel engine is running under other conditions, this injection advance Angle is not the most favorable. In order to improve the economy and power performance of the diesel engine with large speed range, it is hoped that the injection advance Angle of the diesel engine can be automatically adjusted with the change of speed to maintain a more favorable value. Therefore, the injection pump of this diesel engine, especially the direct injection diesel engine, is often equipped with a centrifugal fuel supply advance Angle automatic regulator.
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