Investigation of in-cylinder gas stratification of diesel engine during intake and compression stroke

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Targeting the performance optimization of an automotive diesel engine under transient operation conditions, in this research, the effect of several non-linear loading strategies on diesel performance have been experimentally analyzed using a heavy-duty turbocharged diesel engine running under transient conditions based on the constant 1650 r/min speed, the load is increased from 10% to 100% in a 5 s transition time The results show that the larger the early loading rate and change point load, the better the dynamic torque response. The peak values of smoke and CO and the transient average of brake specific fuel consumption (BSFC), soot and CO can be decreased by increasing the early loading rate by the loading strategies with the appropriate change point load during transient operation. However, combustion deteriorates under the loading process with an overlarge change point load, causing emissions to increase, and the larger the early loading rate, the worse the worsening. Based on the trade-off consisting of torque dynamic response, transient total and transient average of the BSFC and brake specific emissions, peak values of smoke and CO emissions, it is concluded that the loading strategy with the early loading rate is the 50% load per second and the change point load in the 25% load is the most suitable in these strategies.

Section: Influence Of Non-linear Loading Strategies On Comprehensive mentioning

confidence: 99%

Section: Influence Of Non-linear Loading Strategies On Comprehensive mentioning

confidence: 99%

Experimental Investigation of the Loading Strategy of an Automotive Diesel Engine under Transient Operation Conditions

Liu

Han

et al. 2018

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“…Unfortunately, inhomogeneity of EGR distribution by supplying EGR asymmetrically is limited due to mixing in intake ports and transient heavy turbulence in the engine cylinder [32]. To evaluate the effects of strong EGR stratification on diesel combustion and NO x and soot emissions, EGR was assigned to radial stratification in this study.…”

Section: Of 14mentioning

confidence: 99%

Numerical Investigation on Effects of Assigned EGR Stratification on a Heavy Duty Diesel Engine with Two-Stage Fuel Injection

Shen

Cui

et al. 2018

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External exhaust gas recirculation (EGR) stratification in diesel engines contributes to reduction of toxic emissions. Weak EGR stratification lies in that strong turbulence and mixing between EGR and intake air by current introduction strategies of EGR. For understanding of ideal EGR stratification combustion, EGR was assigned radically at −30 • CA after top dead center (ATDC) to organize strong EGR stratification using computational fluid dynamics (CFD). The effects of assigned EGR stratification on diesel performance and emissions are discussed in this paper. Although nitric oxides (NO x) and soot emissions are both reduced by means of EGR stratification compared to uniform EGR, the trade-off between NO x and soot still exists under the condition of arranged EGR stratification with different fuel injection strategies. A deterioration of soot emissions was observed when the interval between main and post fuel injection increased, while NO emissions increased first then reduced. The case with a 4 • CA interval between main and post fuel injection is suitable for acceptable NO and soot emissions. Starting the main fuel injection too early and too late is not acceptable, which results in high NO emissions and high soot emissions respectively. The start of the main fuel injection −10 • CA ATDC is suitable.

“…The outlets of the two runners were placed as close to the intake valves as possible to keep CO 2 separated from fresh air in intake ports during the intake process. More details of the studied engine have been documented in our previous paper [31]. The different mass fraction and distribution of CO 2 in the two intake ports, of critical importance for achieving CO 2 stratification within cylinder 1, are sensitive to trapped CO 2 .…”

Section: Apparatusmentioning

confidence: 99%

“…It was found that the exhaust gas recirculation stratification can be maintained until late timings corresponding to the combustion event. In 2014, Shen and coworkers [31] investigated the in-cylinder EGR distribution on a reformed six-cylinder diesel engine, where lower emissions of NO x and smoke were obtained, and EGR distribution during the intake and compression processes were also analyzed.…”

Section: Introductionmentioning

confidence: 99%

Numeric Investigation of Gas Distribution in the Intake Manifold and Intake Ports of a Multi-Cylinder Diesel Engine Refined for Exhaust Gas Stratification

Shen

Cui

et al. 2017

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Abstract:In-cylinder exhaust gas recirculation (EGR) stratification, generally achieved by supplying EGR asymmetrically into intake ports on a four-valve diesel engine, is sensitive to trapped exhaust gas in the intake manifold and intake ports that is caused by the continuous supply of EGR during the valve-close periods of the intake valves. The subject of this study is to evaluate the distribution of trapped exhaust gas in the diesel intake system using commercial Star-CD software (version 4.22.018). Numeric simulations of the intake flow of fresh air and recycled exhaust in the diesel intake system were initialized following previous experiments that were conducted on a reformed six-cylinder diesel engine by supplying CO 2 instead of EGR to the tangential intake port alone to establish CO 2 stratification in the first cylinder. The distributions of the intake CO 2 in the intake manifold and intake ports under the conditions of 1330 r/min and 50% load with different mass flow rates of CO 2 are discussed. This indicates that CO 2 supplied to one intake port alone would escape to another intake port, which not only weakens the CO 2 stratification by diminishing the mass fraction disparity of the CO 2 between the two intake ports of cylinder 1, but also influences the total mass of CO 2 in the cylinder. There is 4% CO 2 by mass fraction in the intake port without CO 2 supply under the condition that the CO 2 mass flow rate is 5 kg/h during the intake process, and 10% CO 2 under the condition of 50 kg/h.