Reducing Part Load Pumping Loss and Improving Thermal Efficiency through High Compression Ratio Over-Expanded Cycle

2013 ◽  
Author(s):  
Yu Wan ◽  
Aimin Du
Keyword(s):  
Compression Ratio ◽  
Thermal Efficiency ◽  
High Compression Ratio ◽  
Part Load ◽  
High Compression

Improvement of Thermal Efficiency and NOx Emissions by High Compression Ratio Combustion in a DI Diesel Engine

2004 ◽  
Vol 2004.3 (0) ◽  
pp. 131-132
Author(s):  
Yusuke NAKAHIRA ◽  
Takashi OZAWA ◽  
Hidekatsu TSUTSUMI ◽  
Masahiro ONODERA ◽  
Koji IMOTO
Keyword(s):  
Diesel Engine ◽  
Compression Ratio ◽  
Thermal Efficiency ◽  
Nox Emissions ◽  
High Compression Ratio ◽  
High Compression ◽  
Di Diesel Engine

scholarly journals A Numerical Analysis of the Effects of Equivalence Ratio Measurement Accuracy on the Engine Efficiency and Emissions at Varied Compression Ratios

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1413
Author(s):  
Ruomiao Yang ◽  
Xiaoxia Sun ◽  
Zhentao Liu ◽  
Yu Zhang ◽  
Jiahong Fu
Keyword(s):  
Compression Ratio ◽  
Thermal Efficiency ◽  
Equivalence Ratio ◽  
Measurement Accuracy ◽  
High Compression Ratio ◽  
Engine Efficiency ◽  
Fuel Ratio ◽  
High Compression ◽  
Performance And Emissions ◽  
Engine Stability

Increasingly stringent regulations to reduce vehicle emissions have made it important to study emission mitigation strategies. Highly accurate control of the air-fuel ratio is an effective way to reduce emissions. However, a less accurate sensor can lead to reduced engine stability and greater variability in engine efficiency and emissions. Additionally, internal combustion engines (ICE) are moving toward higher compression ratios to achieve higher thermal efficiency and alleviate the energy crisis. The objective of this investigation was to analyze the significance of the accuracy of air-fuel ratio measurements at different compression ratios. In this study, a calibrated 1D CFD model was used to analyze the performance and emissions at different compression ratios. The results showed that carbon monoxide (CO) and nitrogen oxides (NOx) were sensitive to the equivalence ratio regardless of the compression ratio. With a slight change in the equivalence ratio, a high compression ratio had little effect on the change in engine performance and emissions. Moreover, with the same air-fuel ratio, an excessively high compression ratio (CR = 12) might result in knocking phenomenon, which increases the fluctuation of the engine output parameters and reduces engine stability. Overall, for precise control of combustion and thermal efficiency improvement, it is recommended that the measurement accuracy of the equivalence ratio is higher than 1% and the recommended value of the compression ratio are roughly 11.

scholarly journals Combustion and energy distribution of hydrogen-enriched compressed natural gas engines with low heat rejection based on Atkinson cycle

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401881958 ◽  
Author(s):  
Yang Liu ◽  
Yituan He ◽  
Cuijie Han ◽  
Chenheng Yuan
Keyword(s):  
Natural Gas ◽  
Heat Loss ◽  
Compression Ratio ◽  
Thermal Efficiency ◽  
High Compression Ratio ◽  
Compressed Natural Gas ◽  
Heat Rejection ◽  
Natural Gas Engines ◽  
High Compression ◽  
Atkinson Cycle

In order to reduce the heat loss and improve the indicated thermal efficiency of hydrogen-enriched compressed natural gas engines, this article presents a combination of Atkinson cycle with high compression ratio and low heat rejection on the hydrogen-enriched compressed natural gas prototype engine with 55% hydrogen blend. The combustion characteristics and energy distribution of the prototype and modified engines were investigated by simulation, and the conclusions are as follows: the pressure and temperature of modified engines are higher than those of the prototype during the combustion process. Compared with the prototype, the modified engines present lower peak heat release rate, but faster combustion after ignition, and their CA50 are closer to top dead center. Although the high compression ratio engine with Atkinson cycle generates more heat loss, its indicated thermal efficiency still increases by 0.6% with the decrease in the exhaust energy. Furthermore, the high compression ratio engine with low heat rejection and Atkinson cycle combines the advantages of low heat loss and relatively longer expansion stroke, so its heat loss reduces obviously, and 61.6% of the saved energy from low heat rejection and Atkinson cycle can be converted into indicated work that indicates a 4.5% improvement in indicated thermal efficiency over the prototype, which makes it perform better in terms of power and fuel economy simultaneously.

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