A SIMULATE MODEL FOR ANALYZING THE EFFECT OF ENGINE DESIGN PARAMETERS ON THE PERFORMANCE AND EMISSIONS OF SPARK IGNITION ENGINES

A mathematical and simulation model has been developed to simulate a spark ignition engine
operation cycle. The programme written from this simulation model and modified so can be used to
assist in the design of a spark ignition engine for alternative fuels as well as to study many design
parameters such as the effect of engine design parameter like stroke and diameter of the cylinder on
the performance and exhaust emissions of spark ignition engines. In this paper, the description of
three type of engines design parameters according to (stroke/diameter) which are called under
square, square and over square engines using three type of fuel (gasoline, LPG, CNG) singly have
been taken. The variations of power output, thermal efficiency, specific fuel consumption, ignition
delay, temperature of exhaust gases, heat loss and the exhaust emissions (CO2, CO, NO, O2) by
volume, were calculated for each type of engine and then comparing the results to investigate how to
increase engine efficiency and reduce exhaust emissions. The accuracy of the present model is
confirmed by comparison with experimental result that have established by previous literatures and
the results were agreement with literatures. The main results obtained from the present study shows
that, the square engines (S/D=1) can be considered as most efficient, modern and suitable design for
engines running by gasoline and alternative fuels like LPG and CNG, because of higher power
output due to the suitable piston area for pressure distribution. The area of flame front which may
create higher combustion qualities and higher thermal efficiency through faster burning and lower
overall chamber heat loss, also, the potential of the square engines (S/D=1) for indicate specific fuel
consumption was 4% improved.