Turbulent swirling flow in a dynamic model of a uniflow-scavenged two-stroke engine

Ingvorsen, Kristian Mark; Meyer, Knud Erik; Walther, Jens Honoré; Mayer, Stefan

doi:10.1007/s00348-014-1748-y

Cited by 18 publications

(10 citation statements)

References 27 publications

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“…Therefore, the efficiency of the scavenging process is crucial for the total engine performance. Uniflow scavenging, which is widely used in large two-stroke engines, is able to remove exhaust gas much better than loop scavenging and cross scavenging as well as offering a higher scavenging efficiency [4]. It also provides more control on the flow by optimizing the exhaust valve opening and closing timing.…”

Section: Introductionmentioning

confidence: 99%

“…Experimental studies on the scavenging flow inside the full-size firing marine diesel engines are limited due to difficulties of flow measurement inside the large cylinders of these engines during combustion [1,5]. The experimental tests are mostly limited to the steady-flow scavenging process [6,7,8] or dynamic-flow conditions [4,9] on small model engines which differ significantly compared to those in the full-size engine. Therefore, computational fluid dynamics (CFD) studies are essential to obtain an understanding of the scavenging flow inside the large engine cylinder.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Numerical Study of the Scavenging Process in a Large Two-Stroke Marine Engine Using URANS and LES Turbulence Models

Nemati¹,

Ong²,

Jensen³

et al. 2020

SAE Technical Paper Series

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical Study of the Scavenging Process in a Large Two-Stroke Marine Engine Using URANS and LES Turbulence Models

Nemati¹,

Ong²,

Jensen³

et al. 2020

SAE Technical Paper Series

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“…3,10,12,16–19 They are characterized by the strong swirl flow motion formed by the angled intake scavenge ports at the bottom of cylinder liner. 20–22 The axis inclination angle (AIA) and swirl orientation angle (SOA) are shown to have most impact on the in-cylinder flow motions and the scavenging performances in the uniflow scavenged two-stroke engine. 23 Tamamidis and Assanis 24 investigated the effect of SOA on in-cylinder flow motions in a two-stroke scavenged engine by computational fluid dynamics (CFD) simulations of one sector of the cylinder (including one inlet port) and found the larger swirl angles of the inlet ports produce higher swirl levels inside the cylinder.…”

Section: Introductionmentioning

confidence: 99%

Analysis of scavenge port designs and exhaust valve profiles on the in-cylinder flow and scavenging performance in a two-stroke boosted uniflow scavenged direct injection gasoline engine

Wang

Zhao

2017

International Journal of Engine Research

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In this study, effects of intake scavenge port designs and exhaust valve opening profiles were studied on the scavenging process in a newly proposed two-stroke boosted uniflow scavenged direct injection gasoline engine by detailed threedimensional engine simulations. As the most important geometric parameters, the axis inclination angle and swirl orientation angle of scavenge ports, as shown in Figure 1, were investigated and optimized for best scavenging performances at first. With the optimal axis inclination angle of 90°and swirl orientation angle of 20°, various combinations of scavenge port opening timing, exhaust valve opening duration and exhaust valve opening timing were then analysed. Four distinct scavenging periods, that is, early backflow period, backflow scavenging period, main scavenging period and post backflow period, were identified and their impacts on the in-cylinder flow motions and scavenging performances were investigated. The results show that the optimal scavenging performance can be achieved with a higher delivery ratio, charging efficiency and scavenging efficiency when the post backflow is just avoided by tuning the difference between the closing timings of scavenge ports and exhaust valves (D close ) and the overlap between the opening profiles of scavenge ports and exhaust valves (D overlap ) for a specific exhaust valve opening duration. A longer exhaust valve opening duration can be used to further improve the scavenging performances. In addition, the difference between the opening timings of scavenge ports and exhaust valves (D open ) can be increased to improve scavenging efficiency. The D close also shows strong positive correlation with in-cylinder swirl ratio and negative correlation with tumble ratio. The results presented in this study provide the fundamental knowledge of the scavenging process in the uniflow scavenged two-stroke engine and assist the design of scavenge ports and valve strategies to optimize in-cylinder flow motion and scavenge performances in the two-stroke boosted uniflow scavenged direct injection gasoline engine with a variable valve actuation system for exhaust valves.

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“…Because of the long overlapping period of intake and exhaust process in the 2-stroke engine, one of the key issues is the short-circuiting phenomenon, in which some of the intake fresh mixture can flow directly into the exhaust port during the scavenging process [11]. The optical measurement [12,13] and computational fluid dynamic (CFD) simulations [14][15][16][17][18] of the uniflow 2-stroke engine proved the superior scavenging performance of uniflow. The intake ports in a uniflow engine are integrated into the cylinder liner and controlled by the movement of the piston top while exhaust valves are placed in the cylinder head.…”

Section: Introductionmentioning

confidence: 99%

“…The 2-stroke uniflow engines have been widely used in large marine diesel engines [13][14][15] and recently researched for potential applications to passenger cars [3,4,7,10,16,[18][19][20][21]. In this project, a novel 2-stroke Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) engine was proposed to achieve aggressive engine downsizing.…”

Section: Introductionmentioning

confidence: 99%

Evaluations of Scavenge Port Designs for a Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) Engine by 3D CFD Simulations

Wang

Zhao

2016

SAE Technical Paper Series

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The 2-stroke engine has great potential for aggressive engine downsizing due to its double firing frequency which allows lower indicated mean effective pressure (IMEP) and peak in-cylinder pressure with the same output toque compared to the 4-stroke engine. With the aid of new engine technologies, e.g. direct injection, boost and variable valve trains, the drawbacks of traditional 2-stroke engine, e.g. low durability and high emissions, can be resolved in a Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) engine. Compared to the loop-flow or cross-flow engines, the BUSDIG engine, where intake ports are integrated to the cylinder liner and controlled by the movement of piston top while exhaust valves are placed in the cylinder head, can achieve excellent scavenging performance and be operated with high boost. In order to fulfil the potential of the BUSDIG engine, various scavenge ports were designed with different scavenge port number (SPN), Axis Inclination Angle (AIA) and Swirl Orientation Angle (SOA), and their effects were evaluated by three dimensional (3D) computational fluid dynamics (CFD) under different intake pressures and engine speeds. The scavenging process was analyzed by its delivery ratio (DR), trapping efficiency (TE), scavenging efficiency (SE) and charging efficiency (CE). In addition, the in-cylinder flow motions, which play important roles in controlling the charge mixing and combustion process, were studied for different scavenge port designs. Finally, the vertical position of scavenge ports, which determines the scavenge port opening (SPO) timing, the scavenge port height (SPH), and the exhaust valve opening (EVO) timings were varied to investigate their impacts on the scavenging performance and in-cylinder flow motions.

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Turbulent swirling flow in a dynamic model of a uniflow-scavenged two-stroke engine

Cited by 18 publications

References 27 publications

Numerical Study of the Scavenging Process in a Large Two-Stroke Marine Engine Using URANS and LES Turbulence Models

Numerical Study of the Scavenging Process in a Large Two-Stroke Marine Engine Using URANS and LES Turbulence Models

Analysis of scavenge port designs and exhaust valve profiles on the in-cylinder flow and scavenging performance in a two-stroke boosted uniflow scavenged direct injection gasoline engine

Evaluations of Scavenge Port Designs for a Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) Engine by 3D CFD Simulations

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