scholarly journals Effects of split injection strategy on the combustion, emission and economic performance of the low-octane gasoline fueled MPCI engines

2021 ◽  
Vol 7 ◽  
pp. 6651-6657
Author(s):  
Yikai Li ◽  
Jing Peng ◽  
Zhongjie Shi ◽  
Riming Xu
Keyword(s):  
Economic Performance ◽  
Split Injection ◽  
Injection Strategy ◽  
Combustion Emission

Numerical investigation of soot emission sources in a direct-injection spark-ignition engine based on comprehensive breakup model validation

2021 ◽  
pp. 146808742110475
Author(s):  
Joohan Kim ◽  
Jongwon Chung ◽  
Namho Kim ◽  
Seokwon Cho ◽  
Jaeyeop Lee ◽  
...  
Keyword(s):  
Direct Injection ◽  
Spark Ignition ◽  
Emission Sources ◽  
Soot Emission ◽  
Split Injection ◽  
Penetration Length ◽  
Injection Strategy ◽  
Particulate Mass ◽  
Simulation Results ◽  
Breakup Model

Direct injection system is widely adopted in spark-ignition engines to achieve higher thermal efficiency, but it accompanies a penalty in particulate emission, especially when engine is not fully warmed-up. Split injection strategy is known to be an effective measure to reduce engine-out particulate emissions. To better understand the role of split injections, this study aims to analyze the effect of split injection strategy on the sources of soot formation using computational fluid dynamics simulation. To accurately predict changes in particulate mass and number associated with split injection strategy, it is vital that spray models be carefully validated against the experimental data since spray dynamics govern the formation of soot emission sources, such as local fuel-rich mixtures and wall-deposited fuel-films. To this end, a set of spray experiments for free sprays is performed to measure liquid penetration length and droplet size distribution, and hence a comprehensive validation is conducted for spray breakup models. Then, engine simulations are carried out to predict the change in soot sources according to split injection, and the trend of simulation results is compared against the measured engine-out particulate mass and number. Simulation results indicate that breakup model validation using both penetration length and droplet size data is critical for predicting fuel spray dynamics and formation of sources of soot emission. It is also revealed that the piston wetting decreases as the number of injections increases because less amount of fuel is injected when piston is closer to the injector. Lastly, the late evaporation of heavy gasoline components from fuel-film appears to be a significant contributor to soot precursors formation.

On the Effects of Injection Strategy, EGR, and Intake Boost on TSCI With Wet Ethanol

2019 ◽  
Author(s):  
Brian Gainey ◽  
Ziming Yan ◽  
Mozhgan Rahimi-Boldaji ◽  
Benjamin Lawler
Keyword(s):  
Heat Release ◽  
Thermal Stratification ◽  
Equivalence Ratio ◽  
Combustion Efficiency ◽  
Split Injection ◽  
Load Range ◽  
Release Process ◽  
Injection Strategy ◽  
Compression Stroke ◽  
The Impact

Abstract Using a split injection of wet ethanol, where a portion of the fuel is injected during the compression stroke, has been shown to be an effective way to enable thermally stratified compression ignition (TSCI), an advanced, low temperature combustion (LTC) mode that aims to control the heat release process by enhancing thermal stratification, thereby extending the load range of LTC. Wet ethanol is the ideal fuel candidate to enable TSCI because it has a high latent heat of vaporization and low equivalence ratio sensitivity. Previous work has shown “early” compression stroke injections (−150 to −100 deg aTDC) have the potential to control the start of combustion while “mid” compression stroke injections (−90 to −30 deg aTDC) have the potential to control in-cylinder thermal stratification, thereby controlling the heat release rate. In this work, a mixture of 80% ethanol and 20% water by mass is used to further study the injection strategy of TSCI combustion. Additionally, the impact of external, cooled exhaust gas recirculation (EGR) and intake boost level on the effectiveness of a split injection of wet ethanol to control the heat release process are investigated. It was found that neither external, cooled EGR, nor intake boost level has any impact on the effectiveness of the compression stroke injection(s) at controlling the burn rate of TSCI. It was also seen that external, cooled EGR has the potential to increase the overall tailpipe combustion efficiency, while intake boost has the potential to decrease NOx emissions at the expense of combustion efficiency by lowering the global equivalence ratio.

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