Low Temperature Combustion Exploration with Negative Valve Overlap
2022-01-0549
03/29/2022
- Event
- Content
- Progressively stringent emission regulations and increasing regulatory demand on fuel economy have been leading to advanced combustion development. The low temperature combustion (LTC), as known as homogenous charge compression ignition, is a promising technology in reducing exhaust emissions and improving efficiency. However, its operation range is limited to low load due to the reduced volumetric efficiency and the high pressure rise rate. Additionally, how to effectively control the combustion phasing is another challenge in realizing the associated combustion gain. In this work, an advanced valve control mechanism known as continuously variable valve duration (CVVD) and continuously variable valve timing (CVVT) was used for both intake and exhaust valvetrains to enable negative valve overlap (NVO) to trap hot residuals and promote multipoint simultaneous ignition. Heat release phasing was controlled by varying fueling scheme and by adjusting the amount of NVO. Parametric study on valve timing and duration, fueling strategy, lambda, external EGR, spark assist, etc., was first carried out. And then the combustion performance was optimized for different engine speeds. The approaches for extending load limits were summarized and discussed. Finally, the combustion performance was compared to that of spark ignition combustion, demonstrating the combustion gain of LTC.
- Citation
- Zhu, S., JOO, N., Hollowell, J., Ha, K. et al., "Low Temperature Combustion Exploration with Negative Valve Overlap," SAE Technical Paper 2022-01-0549, 2022, .