تاييد الگوي نشتي موتور با استفاده از نتايج تجربي در حالت موتور گرداني

Validation of a Blowby Model Using Experimental Results in Motoring Condition

Blowby and gas flow ʹthrough the cylinder-pis ton -ring crevices are phenomena affecting the engi ne performance and the amount of exhaust pollutant s. Also these phenomena affect the cylinder pressur e, cylinder temperature and the charge amount during a cyc le. The study and validation of a sub-mode l for these phenomena in the absence of combustion ded ucts the effects arisen from the combustion eve nt. In the present study, blowby sub-model and gas flow through crev ices und er motoring conditions ha ve been investigated using a volume and orifice theo ry and the ex perimenta l res ults are measured from a research engi ne. Blowby geometric parameters, consisting of a few critica l cross-sec tiona l areas (orifice areas) and volumes (top land and inter-ring crevice vo lumes), were measure d in ambient temperature and corrected for hot running conditions. The cy linde r pressur e dur ing the cycle opera tion was measured by a piezoelect r ic pressur e transduce r and the low pressure parts of the cyc le were measured using a piezoresistive pressure transdu cer for referencing purposes. The obtained res ults showed a very goo d agreement between expe rimentally measured pressure data and model outpu t for thr ee compression ra tios of 7.6 , 10.2, 12.4 and three engine speeds of 750, 1500 and 2000 rpm, so that the maximum deviation was almost 5%. The model prediction shows that the max imum mass loss inc reases by increasing the compression ratio and decreases by increasing engine speed. Also the peak mas s loss position occurs within the range of 3 to 9DCA after Top Dead Center. Since then , a reverse flow from the top land crevice into the cyli nder is predicted in the model.