Air injection system (or) Air blast injection system

In this method, a blast of air along with the fuel is injected into the cylinder. Before injecting, the air is compressed tn I compressor to a high pressure at 70 bar .For this, normally three stage compressors are used. A fuel pump is driven by the engine itself.
The cam shaft operates the fuel pump through cam and the power required to rotate the cam shaft is taken from the main shaft of the engine through a set of gears and discharges a definite quantity of fuel into the injection valve.
In this method, a blast of air along with the fuel is injected into the cylinder. Before injecting, the air is compressed tn I compressor to a high pressure at 70 bar F or this, normally three stage compressors are used. A fuel pump is driven by the engine itself.The earn shaft operates the fuel pump through cam and the power required to rotate the cam shaft ts taken from the main shaft of the engine through a set of gears and discharge: a definite quantity of fuel into the injection valve.
The injection valve is mechanically operated which delivers the fuel with a air blast into the combustion chamber. By varying the pressure of the injecting air, the rate of fuel supply into the combustion chamber can be controlled.
Since the compressor also driven by the engine, the compressor consumes 10% of the power developed by the engine and hence the net output of the engine is decreased.

Advantages

Better automation and penetration of fuel can be achieved.
Higher brake mean effective pressure can be developed.
Use of inferior fuels is possible.

Disadvantages

System is complicated and expensive. Size and cost of the compressor is very high.
Overall weight of the system is high
Less net output of the engine.

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