Analysis and calculation of friction of piston-assembly based on IMEP method

Piston-assembly friction measurement using IMEP (indicated mean effective pressure) method needs to exactly calculate the force of connecting rod and inertia force of the piston-assembly. In this paper, the formula of the piston-assembly friction is given based on the actual assembly. The actual acceleration of the piston-assembly and the acceleration of the arbitrary point along the center line of connecting rod are derived. Part of inertia force of the connecting rod is calculated by means of distributed mass method. The computational error of the inertia force for several kinds of simplification of connecting rod is analyzed. The study provides the analytical basis for precisely measured friction force of piston-assembly with IMEP method.