Causes of Diesel Generator Knock and Introduction of Air Intake System

The main cause of diesel generator knock is uncontrolled spontaneous combustion (deflagration) of some unburned fuel in the cylinder after the spark plug ignition of the gas engine. The research shows that in the normal combustion process of gas engine, the combustion reaction of the mixture of gas fuel and air is rapidly and continuously diffused outward with the spark plug as the center, and this diffusion reaches the cylinder end wall.

Detonation is an abnormal combustion process. During the ignition of the compressed but abnormal flame diffusion gas-fired diesel generator, the mixture of air and gas consumed by combustion forms the pre detonation gas, which forms spontaneous combustion (deflagration) after ignition of the spark plug. The flame diffusion at the deflagration point and the compression of the pre flame gas make the temperature and pressure at the deflagration point rise; If the deflagration speed is fast, and enough pre flame gas produces deflagration, multiple combustion front end boundaries, namely, the front end of the flame, will converge to produce the impact, and then you can hear the knock sound of the gas engine running.

Several deflagration points converge to produce strong high-pressure shock, which makes some components or the whole engine vibrate. Knock accumulation or severe knock is a serious accident that can cause damage to piston, cylinder head, valve and piston ring of gas engine.

With the change of generator load, the mixer of natural gas diesel generator is controlled and adjusted by the governor to increase or decrease the supply of mixture and meet the demand of generator power. The mixer uses the air pressure difference before and after the mixer to control the opening of the fuel gas cone valve.

When the pressure of fuel gas entering the mixer maintains a constant value, the volume ratio of air to fuel gas in the natural gas diesel generator mixture will remain unchanged, so that the air fuel ratio will not change due to different loads. This is very important to the working condition of the engine.

The air enters the mixer, and the combustible gas enters the mixer from a horizontal pipe with cone valves at both ends in the mixer. The two conical valves at both ends of the horizontal tube are installed in the diaphragm assembly, and the module is provided with a tension spring.

When the mixer is not in operation, the diaphragms at both ends are closely attached to the side wall of the mixer body under the effect of tension spring, and the cone valve is screwed to block the two ends of the horizontal pipe to block the passage of combustible gas.

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