In what way is the diesel engine ignited?

This is a way of forced ignition. Based on the principle of arc discharge between two electrodes of spark plug, combustible mixture is ignited and burned rapidly. At the end of the compression stroke, the combustible mixture composed of fuel and air is compressed to a certain pressure and temperature by the piston in the cylinder and immediately cooled to 1C? 15kV high-voltage current flows into the spark plug installed on the cylinder head, which generates an electric spark in the cylinder, causing the combustible mixture to ignite and burn.

2, compression ignition

This is a kind of ignition mode of diesel engine. Diesel engines use diesel as fuel. Compared with gasoline, diesel oil has low spontaneous combustion temperature (about 220℃), high viscosity and is not easy to evaporate. Moreover, the diesel engine itself has no spark plug, and the compression ratio is higher than that of the gasoline engine. Therefore, the diesel engine compresses the mixture to the ignition point by the compression stroke, so that it can automatically catch fire. So this ignition method is called compression ignition.

Working principle of diesel engine

The working process of diesel engine is actually the same as that of gasoline engine, and each working cycle has to go through four strokes: intake, compression, work and exhaust.

Diesel engines inhale pure air in the intake stroke. At the end of the compression stroke, the oil pressure of diesel oil is increased from the fuel injection pump to above 10MPa, and is injected into the cylinder by the fuel injector, which is mixed with compressed high-temperature air in a short time to form a combustible mixture.

Due to the high compression ratio of diesel engine (generally 16-22), the in-cylinder air pressure can reach 3.5-4.5MPa and the temperature can reach 750- 1000K at the end of compression (while the mixed gas pressure of gasoline engine will be 0.6- 1.2MPa and the temperature will reach 600-700K). Therefore, after diesel oil is injected into the cylinder, it will spontaneously combust immediately after being mixed with air in a short time.

The air pressure in the cylinder rises rapidly to 6-9MPa, and the temperature also rises to 2,000-2,500 K. Driven by high-pressure gas, the piston moves downward, which drives the crankshaft to rotate and do work, and the exhaust gas is also discharged into the atmosphere through the exhaust pipe.