On the Ineffective Lift of Poppet Valves in Internal Combustion Engines.(2nd Report)

Abstract

In the previous paper, the authors already reported the effects of engine speed and pressure difference on the ineffective lift in an internal combustion engine, using a model (A) of piston head. Successively, they have carried out some experiments with another model (B) of piston head in order to examine the effect of tappet clearance on the ineffective lift, by means of two methods, that is, measuring air flow and recording the pressure flactuation in the cylinder. Further, using the regular piston head, they have determined the ineffective lift of suction and exhaust valves by the pressure diagram. Some results obtained in such experiments are summarized as follows : a) If the ineffective lift be used instead of the ineffective angle, it is not necessary at all to consider the values of tappet clearance and the kinds of valve lift curve. b) It is possible to estimate the ineffective lift not only by the measurements of air flow, but also by the analyses of the pressure diagrams. c) In all cases of using the piston head models (A) and (B) and the regular piston head, the ineffective lift increases in proportion to the engine speed and decreases with the increase of the pressure difference between suction and exhaust sides. d) In all cases, the minimum value of ineffective lift remains constant in spite in spite of engine speed and pressure difference as shown already in the previous paper.