3) Peak pressure Vs. Engine Speed ( a ) ( b ) ( c ) ( d ) ( e ) ( f ) Figure 53. Peak pressure vs. engine speed for :(a) diesel fuel ,(b)GTL fuel ,(c)diesel-GTL blend,(d)diesel-waste cooking oil blend (e) diesel-GTL-waste cooking oil blend (f) diesel-GTL-waste cooking oil-corn oil blend In a compression ignition engine, the combustion characteristics of the fuel and the engine performance and emission depend upon the ignition delay period. The longer the delay period, the higher is the rate of combustion and the higher is the resulting pressure rise. The rise in pressure inside the cylinder is attributed to the rate of combustion as well as the ignition delay period of the fuel, which in turn depends on the cetane index. The higher the value of the cetane index of the fuel, the shorter is the ignition delay period. Figure 53 demonstrates the variation of the in-cylinder peak pressure with speed for six different types of fuel. As it can be deduced, the peak pressure decreases with increasing the engine …show more content…
Figure 55 demonstrates the variation of the in-cylinder peak pressure with load for six different types of fuel. As it can be observed, the peak pressure increases with increasing the engine load. The reason behind that is that the mass flow rate of air is kept constant when the engine speed is steady ( =1700 rpm in this case) ,however the amount of fuel injected is increasing , thus the rate of mixing between air and fuel is lower which delays the ignition period