Enhancement of rate of heat transfer in HCCI engine with induction induced swirl and under varying compression ratios and boost pressures

Abstract

Better fuel economy and lower NOx and PM emissions are the two major issues perplexing the researchers as well as new engine developers. Of late a new combustion concept- HCCI has gained popularity in this direction. Low combustion chamber temperatures favor low NOx emission formation. An attempt is made to study the effect of induction induced swirl in enhancing the rate of heat transfer to attain low in-cylinder temperatures favoring low NOx emissions formation. In this regard a computational study is undertaken in analyzing the heat distribution to the engine parts in HCCI mode of combustion under four swirl ratios and operating parameters. Extensive numerical study is carried out on a single cylinder 1.6 L, reentrant piston bowl CI engine. The analysis has been done using ECFM-3Z model of STAR-CD. Suitable modifications in the existing code are done to incorporate the HCCI mode of combustion. The ECFM -3Z model for HCCI mode of combustion is validated with the existing literature to make sure that the results obtained are accurate. The parameters like compression ratio and boost pressure are varied under different swirl ratios to analyze the rate of heat transfer in the combustion chamber. The analysis resulted in achieving maximum increased heat transfer rates of 0.88% to the wall with swirl ratio 1, 45.66% to the dome and 39.99% to the piston with swirl ratio 4; when the compression ratios are increase from 18 to 21. A maximum increase in heat transfer rates of 15.82% to the wall, 26.41% to the dome and 27.46% to the piston with compression ratio 21; when the swirl ratio is increase from 1 to 4. Similarly a maximum increased heat transfer rates of 83.75% to the wall with swirl ratio 4, 88.04% to the dome with swirl ratio 3 and 87.52% to the piston with swirl ratio 4; when the boost pressures are increase from 1 bar to 2 bar were achieved. A maximum increase in heat transfer rates of 59.35% to the wall with boost pressure 1.5 bar, 81.32% to the dome and 76.34% to the piston with boost pressure 2 bar; when the swirl ratio is increase from 1 to 4 were obtained. The study revealed that apart from adopting higher compression ratios and boost pressures adoption of high swirl ratios is observed to be contributing to a large extent in enhancing the rates of heat transfer which would lead to significant reduction in in-cylinder temperatures suitable for low NOx emission formation in HCCI mode.