Experimental investigation on the pumping loss and pressure oscillations in the crankcase

Experimental investigation on the pumping loss and pressure oscillations in the crankcase Abstract:During the crankshaft rotation, as the pistons fall, the gas in crankcase compresses and its pressure rises because the crankcase is generally closed vessel. Pumping losses inside reciprocating engine is obviously undesirable power reducing parasite. However, precise investigation about deviation of crankcase pressure would be helpful for finding efficient method of oil separation from blow by gases. In this study, a experimental test rig and a thermodynamic model was used to estimate, crankcase pumping loss, pressure deviation, and horizontal ventilation of crankcase gas. Numerical simulation was validated by results of experimental tests which carried out for 4 stroke spark ignition engine. Crankcase pressure was measured by a piezoelectric sensor with 80 kHz frequency. Numerical simulation and experimental results had good agreement especially at low engine speed. By increasing engine speed, variation of numerical and experimental results increased due to effect of crankshaft rotation on the effective area. In addition, effects of window area between liners of crankcase were investigated. Results showed that, decreasing windows area caused higher amount of pumping loss. At low engine speed, frequency of crankcase pressure was two times of engine frequency, but at higher engine speed, frequencies were equal. Moreover, increasing engine speed caused more fluctuation of pressure amplitude. Keywords: Pumping loss, ventilation window, crankcase pressure, one dimensional simulation