الفهرس | Only 14 pages are availabe for public view |
Abstract The present work gives a detailed study on the ·effect of valve tappet clearance and also the state of the valves a~d valve seats on the perfonnance of the four-stroke spark ignition engines. This was done by measuring the pressure in the suction manifold of the engine by the use of a pressure transducer and a cathode ray oscilloscope. The power of the engine was consumed and measured by a hydraulic dynamometer. The first set of experiments was performed to show the effect of inlet valve tappet clearance on the pressure in the suction manifold. This was made by changing the inlet valve tappet clearance several times. For each value of clearance, the engine \1asrun at different loads and speeds. A pressure transducer was installed in the suction manifold. The output of the pressure tra.nsducer was connected to a cathode ray oscilloscope. The curve which represents the variation of pressure in the suc tion manifold against crank ang l.eallover the four strokes of the cycle was traced and recorded on photos. By comparing these photographs the effect of inlet valve tappet clearance could be studied The second set of experiments was performed when one valve (or both) is defective. This means that leakage occurs through this valve (or valves). In each case photographs of the pressure trace at various loads and speeds were taken. Again by comparing these photographs, the effect of the state of the valves and the valve seats could be studied. Also, in each case of valve tappet clearance or valve defect, experiments were performed to measure .the effective power and torque of the engine as we Ll.as its specific fuel consumption at full load. IvIathematical equation whicl...represents the pressure variation with the crank degrees Was obtained using the method of curve fitting for the experimental results at the case of standard clearance at certain load and speed. It is,hoped that this equation can predict any malfunction in either valve. |