Comparing methods for improving spark-ignited engine efficiency: Over-expansion with multi-link cranktrain and high compression ratio with late intake valve closing. (15th March 2020)

• Record Type: Journal Article
• Authors: Yang, Zhuyong; Miganakallu, Niranjan; Miller, Tyler; Worm, Jeremy; Naber, Jeffrey; Roth, David
• Is Part Of: Applied energy. Volume 262(2020)
• Publication Date: 2020-03-15
• Subjects: Internal combustion engine -- Over expanded cycle -- High compression ratio -- High efficiency -- Combustion knock; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2020.114560
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Over-expanded and high compression engine are investigated based on 1D simulation. Effect of LIVC is investigated on studied engines at light load conditions. Multi-link engine benefits from its lower knock propensity and over-expansion. Efficiency of multi-link engine is 13.7% higher than high compression engine. Abstract: A common approach of high efficiency engines is to utilize high compression with late intake valve closing (LIVC) to realize an over-expanded cycle. A multi-link cranktrain can also realize an over-expanded cycle with the same geometric intake displacement as a baseline engine while extending the expansion stroke. These two types of over-expanded cycle engines and a baseline engine are investigated and compared in this simulation study. The baseline engine model is calibrated based on the experimental results from a four-cylinder, boosted, spark-ignited engine with compression ratio (CR) of 10.5:1. The CR of high compression ratio engine and multi-link over-expanded engine is 13.0:1 and 10.5:1, respectively. The over-expansion ratio of multi-link engine is 1.5. These three engines were optimized and investigated at three conditions: 1300 rpm 330 kPa net IMEPnet, 1500 rpm 1300 kPa IMEPnet, and 2500 rpm 1000 kPa IMEPnet. At 1300 rpm 330 kPa IMEPnet, multi-link over-expanded engine and high compression engine both used LIVC. With LIVC, the net indicated efficiency of the high compression engine and multi-link engine were improved by 5.2% and 2.4% (relative), respectively, compared to the same engine without LIVC. Multi-link over-expanded engine benefited from its lower knock propensity and over-expansion at medium to high load conditions. At 1500 rpm 1300 kPa IMEPnet, the net indicated efficiency of the multi-link engine was 13.7% and 14.2% (relative) higher than the high compression engine and baseline engine, respectively. At the peak brake efficiency condition of the high compression engine, the net indicated efficiency of multi-link engine was 8.6% (relative) higher than the high compression engine.