Role of structural deformations of the crank-slider mechanism in the computation of the instantaneous frictional losses of a single cylinder engine

Reductions in engine frictional losses improve the engine efficiency, which enhances the vehicle fuel consumption and reduces the tail pipe HC, CO and NO_x emissions. This goal cannot be achieved without the development of reliable methods for measuring instantaneous frictional losses in engines. The focus of the current study is to build on previous work by enhancing the accuracy of the ( P–ω) method in order to determine the overall instantaneous frictional losses of internal combustion engines under both transient and steady-state modes of operation.; The present work has concentrated on identifying the sources leading to erroneous results of the (P–ω) method. This was performed in a completely controlled environment, whereby a detailed model of the crank-slider mechanism is used as a test bed to yield the engine friction torque and to generate the combined rigid and flexible motions of the crank-slider mechanism. The rationale is to isolate the results of this study from the effects of measurement errors and/or noise interference.; The simulation results have demonstrated that the structural deformations of the crank-slider mechanism can adversely affect the computation of the instantaneous engine friction torque. Furthermore, the use of a low-pass filter to attenuate the contributions of the higher order dynamics of the system has been proven herein to be ineffective due to the nonlinearities of the system that have induced superharmonic and combination resonance frequencies in the crankshaft angular motion.; Therefore, a scheme for estimating the structural deformations of the crank-slider mechanism has been proposed. The digital simulation results have demonstrated that the estimated structural deformations of the crank-slider mechanism can be successfully implemented to extract the rigid body behavior from the measured angular motion of the crankshaft. The use of the corrected rather than the measured angular motion of the crankshaft have significantly improved the accuracy of the (P–ω) method in estimating the instantaneous engine friction torque.