Experimental Instrumentation and Procedure
Four cylinders, four strokes SI engine used in the presentexperimental work was shown in figure 1 where as the specifications
of the engine are presented in table 1. Engine torque was measured
by a hydraulic dynamometer and an inductive clamp measured the
instantaneous speed. The cylinder pressure measurements were
made by a piezoelectric quartz high-pressure transducer and the
signal from the transducer was converted from charge to voltage by a
charge amplifier. The output of the charge amplifier was displayed by
a digital oscilloscope. The engine crank angle was measured using an
encoder where the signal was used to trigger the cylinder pressure. A
thermocouple was installed in the exhaust port to measure the exhaust
gas temperature. Additionally, a thermocouple was installed into the
exhaust manifold to measure the temperature of charge. The ignition
timing was monitored and measured as a function of crank angle by
capacitive coupling pickups with the high voltage pulse associated with
the spark event. Water and fuel flow rates were measured by using two
electronic balances. Home-made software was used to measure water
and fuel flow rates on the computer serial ports. Water was injected
into suction port using a gasoline injector. This injected water was in
the form of an ultra-fine mist. The amount of water injection rate was
controlled by varying water supply pressure and/or by an adjustable
valve controlled via a step motor by using a parallel computer port.