2-Stroke CAI Combustion Operation in a GDI Engine with Poppet Valves

Zhang, Yan; Ojapah, Mohammed Moore; Cairns, Alasdair; Zhao, Hua

doi:10.4271/2012-01-1118

Cited by 12 publications

(9 citation statements)

References 13 publications

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“…In a previous study, stable operation in a two-stroke poppet valve engine was 158 claimed at COV IMEP values as high as 35% [5]. In the previous research at part-load conditions [22] the EVC took place before the 171 IVC to increase the residual gas trapped for CAI combustion. In this study, however, the 172 EVC was delayed to obtain higher scavenging efficiencies.…”

Section: Test Procedures 137mentioning

confidence: 99%

High load performance and combustion analysis of a four-valve direct injection gasoline engine running in the two-stroke cycle

Nora

Zhao

2015

Applied Energy

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Section: Test Procedures 137mentioning

confidence: 99%

High load performance and combustion analysis of a four-valve direct injection gasoline engine running in the two-stroke cycle

Nora

Zhao

2015

Applied Energy

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“…homogeneous charge compression ignition (HCCI) and controlled auto-ignition (CAI). [5][6][7] The bore/stroke (B/S) ratio determines the overall dimensions of the engine for a given displacement. The engine with a large B/S ratio is more compact and can be operated at a higher engine speed without deteriorating the mechanical efficiency.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the effect of bore/stroke ratio and scavenge port angles on the scavenging process in a two-stroke boosted uniflow scavenged direct injection gasoline engine

Wang

Zhao

2017

Proceedings of the Institution of Mechanical Engineers, Part D:

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In this study, a two-stroke boosted uniflow scavenged direct injection gasoline (BUSDIG) engine was proposed and researched to achieve aggressive engine downsizing and downspeeding. Compared to loop or cross scavenged twostroke engines, the BUSDIG engine can achieve excellent scavenging performance and be operated with higher boost pressure as well as the absence of air and fuel short-circuiting. As a fundamental engine geometric parameter, the bore/ stroke (B/S) ratio would directly affect the scavenging process in the uniflow scavenged two-stroke engine. Three-dimensional computational fluid dynamics simulations were used to investigate the scavenging process in the BUSDIG engine with different B/S ratios. Four B/S ratios of 0.66, 0.8, 1, and 1.3 were analyzed. The results indicate that a bigger B/S ratio leads to deteriorated swirl flow motion but better delivery ratio, scavenging efficiency, and charging efficiency. In order to fulfil the potential of the BUSDIG engine with different B/S ratios, two key scavenge port angles, i.e. axis inclination angle (AIA) and swirl orientation angle (SOA), were varied from the baseline design (AIA = 90°, SOA = 20°) to study their effects on the scavenging process for each B/S ratio design. Overall, a larger AIA leads to lower swirl ratio (SR) but achieves better scavenge performance, which is crucial for a large B/S ratio design. A small SOA design leads to noticeably lower SR but superior scavenging performances for a small B/S ratio design. An intermediate SOA, e.g. 10 and 20°, is preferred to improve the scavenging for a large B/S ratio design.

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“…In the case of part-load conditions, when controlled auto-ignition (CAI)/homogeneous charge compression ignition (HCCI) combustion is feasible to improve the thermal efficiency of the engine, the residual gas and its temperature distributions directly influence the auto-ignition and heat release process. [12][13][14] Moreover, the characteristics of reversed tumble, especially at high intake pressure, have impact on the local flow field before fuel injection which influences the liquid phase movement, the incylinder mixing process and thus the mixture stratification. At last but not least, it is known that the flame propagation speed and heat release rate are closely related to the turbulence intensity and flow structure when the SI combustion is adopted.…”

Section: Introductionmentioning

confidence: 99%

Influences of intake ports and pent-roof structures on the flow characteristics of a poppet-valved two-stroke gasoline engine

Zhao

2016

International Journal of Engine Research

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In order to minimize the short-circuiting of the intake charge in a poppet-valved two-stroke engine, a ''step structure'' on the intake side of the pent-roof was employed to shroud the bulk flow at the upper periphery of the intake valves at low valve lifts. Several intake-port geometries and pent-roof angles were evaluated on their charging and reversed tumble generating abilities using a steady flow test rig built in computational fluid dynamics, among which top-entry ports and relatively small pent-roof angle were selected. The scavenging processes of the two-stroke engine at high load and 3000 r/min condition with different intake valve seat heights were simulated and evaluated. The local flow patterns and composition distribution were also studied. The results show that lowering the intake valve seat height achieves higher delivery ratio and charging efficiency, but marginally better scavenging efficiency and slightly lower trapping efficiency. The scavenging process experiences a slow displacement period due to low flow momentum for the high valve seat cases and flow interaction at the exhaust exits for the low valve seat cases. Reversed tumble is the dominant flow pattern during the scavenging process. The lower the valve seat, the higher the tumble ratio in the early stage and at the end of the scavenging period. For all valve seat configurations, the least scavenged regions are located near the engine head wall and between the intake and the exhaust valves, while the regions rich in fresh charge are located along the major path of the reversed tumble. Low intake valve seat height is effective in increasing the overall in-cylinder air proportion. Further reducing it can result in higher fresh charge proportion below the exhaust valves and near the head wall.

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2-Stroke CAI Combustion Operation in a GDI Engine with Poppet Valves

Cited by 12 publications

References 13 publications

High load performance and combustion analysis of a four-valve direct injection gasoline engine running in the two-stroke cycle

High load performance and combustion analysis of a four-valve direct injection gasoline engine running in the two-stroke cycle

Analysis of the effect of bore/stroke ratio and scavenge port angles on the scavenging process in a two-stroke boosted uniflow scavenged direct injection gasoline engine

Influences of intake ports and pent-roof structures on the flow characteristics of a poppet-valved two-stroke gasoline engine

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