Influence of Injection Timing for Split-Injection Strategies on Well-Mixed High-Load Combustion Performance in an Optically Accessible Spark-Ignition Direct-Injection (SIDI) Engine

2017 ◽  
Author(s):  
Lewis Gene Clark ◽  
Sanghoon Kook ◽  
Qing Nian Chan ◽  
Evatt R. Hawkes
Keyword(s):  
Direct Injection ◽  
Spark Ignition ◽  
High Load ◽  
Injection Timing ◽  
Split Injection ◽  
Combustion Performance ◽  
Injection Strategies

Effect of piston shape design on the scavenging performance and mixture preparation in a two-stroke boosted uniflow scavenged direct injection gasoline engine

2020 ◽  
pp. 146808741990007 ◽  
Author(s):  
Xinyan Wang ◽  
Hua Zhao
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Shape Design ◽  
Injection Timing ◽  
Stoichiometric Mixture ◽  
Split Injection ◽  
Spark Plug ◽  
Direct Injection Gasoline Engine ◽  
Stroke Engine ◽  
Injection Strategies

Compared to a four-stroke engine, the two-stroke engine doubles firing frequency and has favourable power-to-weight or power-to-volume ratio as well as engine downsizing to improve the overall powertrain fuel economy. In order to overcome the shortcomings of the conventional cross-flow or loop scavenged two-stroke engines, a two-stroke boosted uniflow scavenged direct injection gasoline engine was designed and its performance was analysed. In this study, three-dimensional computational fluid dynamics simulations were performed to understand the impact of the piston shape design on the scavenging process, in-cylinder flow formation, turbulence level and subsequent fuel/air mixing process in the boosted uniflow scavenged direct injection gasoline engine. Both single injection and split injection strategies were investigated to study the interactions between piston designs and fuel injection strategies to achieve stoichiometric mixture around the spark plug. The results show that the optimised piston with the same opening timing for all scavenge ports could achieve much better scavenging performance than the baseline piston design. In particular, the shallow pistons, that is, Piston #1 and Piston #4, could produce stoichiometric mixture around the spark plug with relatively lower inhomogeneity and higher turbulence kinetic energy around top dead centre when implementing the split injection strategy with start of injection timing at 250/310 °CA.

scholarly journals Influence of the diesel pilot injector configuration on ethanol combustion and performance of a heavy-duty direct injection engine

2021 ◽  
pp. 146808742110012
Author(s):  
Nicola Giramondi ◽  
Anders Jäger ◽  
Daniel Norling ◽  
Anders Christiansen Erlandsson
Keyword(s):  
Direct Injection ◽  
Engine Performance ◽  
High Load ◽  
Operating Conditions ◽  
Injection System ◽  
Injection Timing ◽  
Diesel Combustion ◽  
Heavy Duty ◽  
Pure Ethanol ◽  
Ethanol Combustion

Thanks to its properties and production pathways, ethanol represents a valuable alternative to fossil fuels, with potential benefits in terms of CO2, NOx, and soot emission reduction. The resistance to autoignition of ethanol necessitates an ignition trigger in compression-ignition engines for heavy-duty applications, which in the current study is a diesel pilot injection. The simultaneous direct injection of pure ethanol as main fuel and diesel as pilot fuel through separate injectors is experimentally investigated in a heavy-duty single cylinder engine at a low and a high load point. The influence of the nozzle hole number and size of the diesel pilot injector on ethanol combustion and engine performance is evaluated based on an injection timing sweep using three diesel injector configurations. The tested configurations have the same geometric total nozzle area for one, two and four diesel sprays. The relative amount of ethanol injected is swept between 78 – 89% and 91 – 98% on an energy basis at low and high load, respectively. The results show that mixing-controlled combustion of ethanol is achieved with all tested diesel injector configurations and that the maximum combustion efficiency and variability levels are in line with conventional diesel combustion. The one-spray diesel injector is the most robust trigger for ethanol ignition, as it allows to limit combustion variability and to achieve higher combustion efficiencies compared to the other diesel injector configurations. However, the two- and four-spray diesel injectors lead to higher indicated efficiency levels. The observed difference in the ethanol ignition dynamics is evaluated and compared to conventional diesel combustion. The study broadens the knowledge on ethanol mixing-controlled combustion in heavy-duty engines at various operating conditions, providing the insight necessary for the optimization of the ethanol-diesel dual-injection system.

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.

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