Optimization of In-Cylinder Flow and Mixing for a Center-Spark Four-Valve Engine Employing the Concept of Barrel-Stratification

Kuwahara, Keisuke; Watanabe, Tetsuya; Takemura, Jiro; Omori, Shuichi; Kume, T.; Ando, Hiroyasu

doi:10.4271/940986

Cited by 50 publications

(23 citation statements)

References 4 publications

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“…The results shown in Figs 9c and d are therefore given only in the cylinder half-plane closest to the illumination source where the appropriate light sheet quality could be achieved. Figure 9d shows a horizontal cross-section through the so-called 'wing vortices' previously observed by Kuwahara et al [7] in a similar engine. In the high swirl case (Fig.…”

Section: Horizontal Planementioning

confidence: 99%

“…Further, it has also been shown that significant charge dilution can be achieved in high barrel swirl engines by means of barrel charge stratification [5 -7]. While turbulence enhancement is required for rapid and repeatable combustion of the charge, high barrel swirl ratios (BSR) may also produce strong bulk flows which, depending on the combustion chamber geometry, can persist throughout and after the time of ignition [7,8]. Excessive bulk flow may adversely affect initiation of the flame kernel owing to stretching of the arc discharge, or convection of the early flame kernel towards a combustion chamber wall.…”

Section: Motivationmentioning

confidence: 99%

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Barrel swirl breakdown in spark-ignition engines: Insights from particle image velocimetry measurements

Reeves¹,

Haste

Garner

et al. 1999

Proceedings of the Institution of Mechanical Engineers, Part D:

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Particle image velocimetry (PIV) has been used here to study the formation and breakdown of barrel swirl (‘tumble’) in a production geometry, four-stroke, four-valve, motored, spark-ignition, optically accessed internal combustion (IC) engine. The barrel swirl ratio (BSR) of the cylinder head could be enhanced by means of a port face inducer gasket so that the flow processes taking place at low and high swirl ratios could be investigated conveniently. Double-exposed images from planes both parallel and perpendicular to the cylinder axis were recorded at selected crank angles through the induction and compression strokes at a motored engine speed of 1000 r/min, with a wide open throttle, for both high and low BSR cases. The recorded images were interrogated by digital autocorrelation to give two-dimensional maps of instantaneous velocity. In both high and low BSR cases, a barrel or tumbling vortex motion is generated during induction, which is shown to persist throughout the majority of the compression stroke. The details of barrel swirl formation during induction and its subsequent modification during compression, however, differ strongly between the two cases. These differences can be explained qualitatively in terms of two main events; the first being competition during induction between vortices of unequal strength and the second being competition between the large-scale swirl motion and the local flow field generated by piston motion during compression. In the low barrel swirl case, significant dissipation occurs owing to these interactions and consequently the large-scale motion exhibits lower mean velocities and undergoes significant distortion. In the case of high BSR, the competition effects are minimized and a single ordered vertical vortex exhibiting high velocity magnitudes is observed to avoid piston induced distortion. It then moves into the apex of the pent roof combustion chamber where it survives as a single ordered vortex until at least 40° crank angle (CA) before top dead centre (TDC). Limitations and developments of the PIV technique are discussed.

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Section: Horizontal Planementioning

confidence: 99%

Section: Motivationmentioning

confidence: 99%

Barrel swirl breakdown in spark-ignition engines: Insights from particle image velocimetry measurements

Reeves¹,

Haste

Garner

et al. 1999

Proceedings of the Institution of Mechanical Engineers, Part D:

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“…By using the effects of turbulence enhancement and the charge stratification realized by tumble, a significant combustion improvement could be realized in the extremely lean conditions such as the air fuel ratio of 30 [7]. The fuel distribution and flow structure in cylinder was optimized by intake port partitions and tumble control piston [8].…”

Section: Lean Burn Enginementioning

confidence: 99%

“…The cylindrical shape is expected to be better. The piston flat top was modified as an attempt to maintain the momentum [8]. Considering the rigorous mixing during the compression stroke shown in Fig.…”

Section: Charge Mixing During the Compression Strokementioning

confidence: 99%

Design and Demonstration of a Spark Ignition Engine Operating in a Stratified-EGR Mode

Han¹,

Cheng²

1998

SAE Technical Paper Series

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The use of substantial amount of exhaust gas recirculation (EGR) via the technique of flow stratification in-cylinder was investigated to improve the fuel economy of spark ignition engines under part load. The fuel economy gain is achieved by reducing the pumping loss with EGR while the stratification enables stable combustion at high levels of EGR. By doing so, the ability to control NOx emissions using the three-way catalytic converter is also retained. To realize this goal, a new method of supplying EGR to achieve in-cylinder stratification was incorporated and experiments were performed to demonstrate the concept.A new transparent engine facility was constructed to assist the development of the stratified EGR strategy. In order to minimize the mixing in intake port, to maintain the stratification in cylinder, and to obtain fast burn, an intake flow control system was realized by using solenoid valve-controlled EGR injection. Qualitative measurements of in-cylinder flow motion at motoring condition were carried out with visualization techniques such as planar laser-induced fluorescence (PLIF) and Mie scattering to obtain information on the mixing process during intake and compression. The engine was operated at firing condition to assess the engine performance operating in a stratified-EGR mode. Cylinder pressure measurements were used to gain information about the combustion process. A new combustion model incorporating mixing and flame stretch factor, which is believed to be significant, especially under the diluted mixture condition, was developed to examine flame propagation properties under the stratified condition.The visualization results of PLIF showed that the stratification between air/fuel mixture and EGR gas was relatively well established during the intake stroke. There was, however, significant mixing in the late part of the compression stroke. This process may be explained by that large scale tumble motion was introduced into the cylinder during the intake stroke, and that the organized motion broke into small eddies during the compression stroke and hence resulted in the substantial mixing then. Performance comparison between the engine operating with the homogeneous mixture and with the stratified mixture illustrated that the stratified mode had greatly improved fuel consumption and had provided stable combustion at high dilution ratio. The observed trend on the burning process could be reproduced reasonably well by the model. Thesis AdvisorWai K. Cheng Associate professor of Mechanical Engineering

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“…It has already been shown that in a 4-valve engine with a pentroof chamber, fuel stratification in the direction parallel to the top of the roof can be achieved by injecting into only one of the two intake ports [2,3,4]. Biacetyl-LIF combined with LDV and combustion analyses [4] showed that by coupling the effect of intense turbulence, moderate velocity at the spark and ignition on the rich side, the performance of the 4-valves engine was greatly enhanced.…”

Section: Introductionmentioning

confidence: 99%

Visualisation of Gasoline and Exhaust Gases Distribution in a 4-Valve Si Engine; Effects of Stratification on Combustion and Pollutants

Deschamps

Baritaud

1997

Rev. Inst. Fr. Pét.

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Optimization of In-Cylinder Flow and Mixing for a Center-Spark Four-Valve Engine Employing the Concept of Barrel-Stratification

Cited by 50 publications

References 4 publications

Barrel swirl breakdown in spark-ignition engines: Insights from particle image velocimetry measurements

Barrel swirl breakdown in spark-ignition engines: Insights from particle image velocimetry measurements

Design and Demonstration of a Spark Ignition Engine Operating in a Stratified-EGR Mode

Visualisation of Gasoline and Exhaust Gases Distribution in a 4-Valve Si Engine; Effects of Stratification on Combustion and Pollutants

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