Operating principle of Diesel Engine

Operating principle of Diesel Engine
In fact, the working process of diesel engines with gasoline engines are also the same. Each work cycle of intake experience compression, for power, four stroke exhaust. However, due to diesel fuel used is diesel, the viscosity ratio of gasoline, which is difficult to evaporate, while its auto-ignition temperature is lower than gasoline, so the combustible mixture formation and ignition gasoline engine with a different way.
In the intake stroke diesel engine breathe pure air. Near the end of compression stroke, diesel fuel injection pump through the oil pressure to 10MPa or more, through the injectors spray into the cylinder, a very short time and compressed hot air mixture, to form the combustible mixture. As the diesel engine compression ratio (usually 16-22 so the end of the cylinder compressed air pressure up to 3.5-4.5MPa and the temperature up to 750-1000K and a mixture of gasoline at this time, air pressure 0.6-1.2MPa temperature for up to 600 – 700K greatly exceed the ignition temperature of diesel fuel so diesel is injected into the cylinder, the air mixed with a very short time immediately after self-ignition combustion. cylinder pressure up to 6-9MPa rapid temperature rise to 2000-2500K to promote high-pressure gas , the piston downward movement and rotation of the crankshaft drive for power, the same exhaust pipe into the atmosphere through the exhaust.
Ordinary diesel engine by the engine camshaft driven by means of high pressure pump diesel fuel delivered to each cylinder chamber. This approach to oil changes with changes in engine speed, various speeds can not do the best fuel supply. And now more and more widely used electronic control common rail diesel injection systems can better solve the problem.
Common rail injection system is composed of high-pressure fuel supply pump, common for the tubing, injector, electronic control unit (ECU and some pipe pressure sensors, the system each injector through their high-pressure tubing is connected with the public for the pipeline, public for the pipeline to the injector to play the role of hydraulic accumulators. work, high pressure oil pump to high pressure fuel delivery to the public for the pipeline, high pressure pumps, pressure sensors and ECU closed loop composed of the work, the public for the pipeline to achieve within the hydraulic precise control, completely changed the oil pressure with engine speed variation of the phenomenon. Its main features are the following three aspects:
1 injection timing and fuel metering completely separate from the fuel injection pressure and time control by the ECU fuel injection process.
2 can be based on engine operating conditions to adjust the cylinder fuel injection pressure, injection start point, continue the time to pursue the best fuel injection control points.
3 can achieve a high injection pressure, and can achieve the pre-injection diesel.
Compared to gasoline engines, diesel engines with low fuel consumption (on average 30% lower than gasoline) and diesel prices low, so fuel economy is better; while the engine speed is generally much lower than the gasoline engine, big torque than gasoline, but The quality of large, noisy work, manufacturing and maintenance costs, while emissions are worse than gasoline. But with modern technology, diesel engines, these drawbacks are gradually being overcome.