Numerical investigations on HCCI engine with increased induction induced swirl and engine speed

• Published in: Journal of Central South University Vol. 22; no. 10; pp. 3837 - 3848
• Main Authors: Sharma, T. Karthikeya, Prasad Rao, G. Amba, Murthy, K. Madhu
• Format: Journal Article
• Language: English
• Published: Changsha Central South University 01-10-2015
• Subjects: Engineering; Metallic Materials; HCCI engine; emissions and performance; swirl ratio; ECFM-3Z
• ISSN: 2095-2899; 2227-5223
• DOI: 10.1007/s11771-015-2928-5

Homogeneous charge compression ignition (HCCI) mode of combustion is popularly known for achieving simultaneous reduction of NO
x
as well as soot emissions as it combines the compression ignition (CI) and spark ignition (SI) engine features. In this work, a CI engine was simulated to work in HCCI mode and was analyzed to study the effect of induction induced swirl under varying speeds using three-zone extended coherent flame combustion model (ECFM-3Z, compression ignition) of STAR-CD. The analysis was done considering speed ranging from 800 to 1600 r/min and swirl ratios from 1 to 4. The present study reveals that ECFM-3Z model has well predicted the performance and emissions of CI engine in HCCI mode. The simulation predicts reduced in-cylinder pressures, temperatures, wall heat transfer losses, and piston work with increase in swirl ratio irrespective of engine speed. Also, simultaneous reduction in CO
2
and NO
x
emissions is realized with higher engine speeds and swirl ratios. Low speeds and swirl ratios are favorable for low CO
2
emissions. It is observed that increase in engine speed causes a marginal reduction in in-cylinder pressures and temperatures. Also, higher turbulent energy and velocity magnitude levels are obtained with increase in swirl ratio, indicating efficient combustion necessitating no modifications in combustion chamber design. The investigations reveal a total decrease of 38.68% in CO
2
emissions and 12.93% in NO
x
emissions when the engine speed increases from 800 to 1600 r/min at swirl ratio of 4. Also an increase of 14.16% in net work done is obtained with engine speed increasing from 800 to 1600 r/min at swirl ratio of 1. The simulation indicates that there is a tradeoff observed between the emissions and piston work. It is finally concluded that the HCCI combustion can be regarded as low temperature combustion as there is significant decrease in in-cylinder temperatures and pressures at higher speeds and higher swirl ratios.