Effects of Intake Port Geometry on Large Scale In-Cylinder Flows

Church, William F.; Farrell, Patrick V.

doi:10.4271/980484

Cited by 11 publications

(7 citation statements)

References 6 publications

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“…The high-temperature residual gas may account for this difference. Other researchers have also found that the mixing of the incoming air charge and the residual gases is not uniform [6]. It may also result from the fact that the temperatures of the intake valves, exhaust valves, and cylinder head are different.…”

Section: Engine Simulation Resultsmentioning

confidence: 98%

See 1 more Smart Citation

Investigation of the grid and intake-generated tumble on the in-cylinder flow in a compression ignition direct-injection engine

Micklow

Gong

2008

Proceedings of the Institution of Mechanical Engineers, Part D:

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The in-cylinder flow field was numerically investigated for a four-valve per cylinder Caterpillar diesel CAT3401 engine. The computer program used was the KIVA3V code developed by Los Alamos National Laboratory. To assess the effect of modelling assumptions made during the domain discretization, three grid models were developed. The first grid or the 'complete' grid was a full 360u mesh with moving valves, intake ports, exhaust ports, and runners. The second grid was a full 360u mesh without moving valves, intake ports, or exhaust ports. The third grid assumed that the in-cylinder flow field was periodic and a 60u mesh was generated to accommodate one of the six centrally located fuel injectors. It also neglected the valves and the intake and exhaust ports. The simplification of the grids is to reduce the massive computational and memory requirements to model these flows.For the complete grid, the computation was initiated when the piston was at the top dead centre location on the intake stroke. For the second and third grids, the computation was initiated after the intake valve had closed. Complex three-dimensional vortical flow structures or tumble is developed during the intake stroke. These structures were clearly shown when the complete grid was used. By comparing the solution of the complete grid with the solutions of the second and third grids, it was seen that important in-cylinder flow information is lost. To overcome this deficiency, a new parameter, namely the initial tumble ratio, was embedded into the standard KIVA3V code by the present authors. When the simplified second grid is used in conjunction with the initial tumble ratio option, an in-cylinder flow pattern similar to that which was computed with the complete grid was obtained. This indicates that the new option significantly improves the accuracy of in-cylinder flow prediction when the moving valves and intake or exhaust ports are not modelled.The effects of the values of the initial turbulence kinetic energy (TKE i ) and the initial turbulence length scale (SCL i ) were also studied. It is found that the suggested value of TKE i used in KIVA3V is too small to predict the actual turbulence kinetic energy in the cylinder when the second and third grids are used. Therefore, a larger value for TKE i is recommended. The effects of the different grids, the new initial tumble ratio, and the different values of SCL i and TKE i on important flow parameters, such as the swirl ratio, the tumble ratio, and the turbulence kinetic energy are compared in detail in this article.

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Section: Engine Simulation Resultsmentioning

confidence: 98%

“…Further, it has been reported that changes to intake port geometries have a marked effect on the flow field structures appearing within the cylinder [6][7][8]. These important flow influences often referred to as tumble are particularly apparent before bottom dead centre (BDC).…”

Section: Introductionmentioning

confidence: 99%

Investigation of the grid and intake-generated tumble on the in-cylinder flow in a compression ignition direct-injection engine

Micklow

Gong

2008

Proceedings of the Institution of Mechanical Engineers, Part D:

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“…Ahmad Amer et al [12] found that the large scale tumble structures are essential in enhancing the turbulence inside the cylinder but only if these structures collapse just before TDC, which allows them to control the initial kernel development, as also reported in [13,14]. Moreover the upper part of the piston is detrimental for tumble breakdown, so they stated the importance of the piston presence in all the tumble motion analysis, as also underlined in [15].…”

Section: Literature Summary On the Tumble Motionmentioning

confidence: 85%

3D CFD Analysis of the Influence of Some Geometrical Engine Parameters on Small PFI Engine Performances - The Effects on Tumble Motion and Mean Turbulent Intensity Distribution

Falfari¹,

Bianchi²,

Nuti³

2012

SAE Technical Paper Series

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In scooter/motorbike engines coherent and stable tumble motion generation is still considered an effective mean in order to both reduce engine emissions and promote higher levels of combustion efficiency. The promotion of a stable and coherent tumble structure is largely believed in literature to enhance in-cylinder turbulence accelerating combustion process. In small PFI engine layout and weight constraints limit the adoption of more advanced concepts. In previous technical papers the authors demonstrated the influence of head shape and squish area on tumble vortex formation, development, breakdown and on final value of turbulence close to spark plug for small PFI engines. The main result of the this research was that the combustion chamber having the less squish area resulted to have the highest level of turbulence close to spark plug at ignition time. The geometry under analysis in the current paper is a 3-valves pent-roof motorcycle engine. 3D CFD simulations were ran at 6500 rpm with AVL FIRE code. The chosen engine geometry was the geometry found to be the best setup in terms of turbulence and combustion performances in the previous paper. In the present paper the head shape and the squish area were kept constant and the following engine parameters were varied: the intake duct angle (the angle of the intake duct entering the head was reduced of 6%, i.e. it was more directed toward the exhaust side of the chamber), the piston shape, and finally the compression ratio (it was reduced of 9%). The main goal of the current analysis is to understand which of these parameters is predominant in accelerating combustion for directing engine design toward the best setup .

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“…The enhanced in-cylinder turbulence for various intake ports is controlled by the intake flow characteristics during air induction process [22,23]. In the present work, the peak air mass flow rate To correlate with flow data, engine experiments are conducted to quantify the combustion and cyclic variation.…”

Section: Methodsmentioning

confidence: 99%

Impact of Tumble on Combustion in SI Engines: Correlation between Flow and Engine Experiments

He¹,

Selamet²,

Reese³

et al. 2007

SAE Technical Paper Series

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The introduction of tumble into the combustion chamber is an effective method of enhancing turbulence intensity prior to ignition, thereby accelerating the burn rates, stabilizing the combustion, and extending the dilution limit. In this study, the primary intake runners are partially blocked to produce different levels of tumble motion in the cylinder during the air induction process. Experiments have been performed with a Chrysler 2.4L 4-valve I4 engine at maximum brake torque timing under two operating conditions: 2.41 bar brake mean effective pressure (BMEP) at 1600 rpm, and 0.78 bar BMEP at 1200 rpm. A method has been developed to quantify the tumble characteristics of blockages under steady flow conditions in a flow laboratory, by using the same cylinder head, intake manifold, and tumble blockages from the engine experiments. A refined tumblemeter is installed under cylinder head to measure the compressive load of the tumble vortex, allowing for the calculation of angular momentum of the incoming air, tumble number, and tumble ratio at varying intake valve lifts. A correlation is then sought between the engine and flow experiments to help quantify the impact of tumble motion on combustion and cyclic variation. The air flow rate into the cylinder, discharge coefficient of the intake system, and the flow loss coefficient across the blockage are also analyzed for different levels of tumble motion. The validity of the method under steady flow conditions is confirmed by comparison of the results with the engine experiments.

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Effects of Intake Port Geometry on Large Scale In-Cylinder Flows

Cited by 11 publications

References 6 publications

Investigation of the grid and intake-generated tumble on the in-cylinder flow in a compression ignition direct-injection engine

Investigation of the grid and intake-generated tumble on the in-cylinder flow in a compression ignition direct-injection engine

3D CFD Analysis of the Influence of Some Geometrical Engine Parameters on Small PFI Engine Performances - The Effects on Tumble Motion and Mean Turbulent Intensity Distribution

Impact of Tumble on Combustion in SI Engines: Correlation between Flow and Engine Experiments

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