The Effect of Auxiliary Fuels on the Smoke-limited Power Output of Diesel Engines

It is well known that one of the factors Limiting the power output from Diesel engines is the tendency to produce exhaust smoke. In consequence only some 65–70 per cent of the available air can be burnt. By reducing the full-load quantity of Diesel fuel injected and aspirating a volatile fuel, such as gasoline, into the intake air, power outputs of 20 per cent or more above the maximum rated load can be obtained without producing more smoke than when the engine is operated at full load under normal conditions. About 80 per cent of the available air can then be utilized. The effect of octane number of the auxiliary fuel is important, maximum smoke-limited powers being obtained with the higher octane number fuels, while with fuels of low octane number, power increase may be limited by the occurrence of knocking when the air-fuel ratio is too low. By limiting the power on Diesel fuel alone to about 80 per cent of the normal maximum and aspirating gasoline into the intake, it is possible to obtain a power increase of about 12 per cent at all speeds between that of maximum torque and maximum power without increased smoking or the occurrence of knock. Owing to improved economy, the fuel cost per brake horsepower per hour using gasoline aspiration, is not increased. Modifications required to the engine are slight and the fuels required to operate are readily obtainable; even if the auxiliary fuel should run out no damage would be done to the engine.