Numerical Comparative Analysis of In-Cylinder Tumble Flow Structures in Small PFI Engines Equipped by Heads Having Different Shapes and Squish Areas

For increasing the thermal engine efficiency, faster combustion and low cycle-to-cycle variation are required. In PFI engines the organization of in-cylinder flow structure is thus mandatory for achieving increased efficiency. In particular the formation of a coherent tumble vortex with dimensions comparable to engine stroke largely promotes proper turbulence production extending the engine tolerance to dilute/lean mixture. For motorbike and scooter applications, tumble has been considered as an effective way to further improve combustion system efficiency and to achieve emission reduction since layout and weight constraints limit the adoption of more advanced concepts. In literature chamber geometry was found to have a significant influence on bulk motion and turbulence levels at ignition time, while intake system influences mainly the formation of tumble vortices during suction phase. The most common engine parameters believed to affect in-cylinder flow structure are: 1. Intake duct angle; 2. Inlet valve shape and lift; 3. Piston shape; 4. Pent-roof angle. The present paper deals with the computational analysis of three different head shapes equipping a scooter/motorcycle engine and their influence on the tumble flow formation and breakdown, up to the final turbulent kinetic energy distribution at spark plug. The engine in analysis is a 3-valves pent-roof motorcycle engine. The three dimensional CFD simulations were run at 6500 rpm with AVL FIRE code on the three engines characterised by the same piston, valve lift, pent-roof angle and compression ratio. They differ only in head shape and squish areas. The aim of the present paper is to demonstrate the influence of different head shapes on in-cylinder flow motion, with particular care to tumble motion and turbulence level at ignition time. Moreover, an analysis of the mutual influence between tumble motion and squish motion was carried out in order to assess the role of both these motions in promoting a proper level of turbulence at ignition time close to spark plug in small 3-valves engines.

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Development of a Motorcycle Engine with a Three-dimensional Cam for Continuous Variable Valve Lift and Timing Mechanism

SAE International Journal of Engines ◽

10.4271/2008-32-0016 ◽

2008 ◽

Vol 1 (1) ◽

pp. 1357-1365 ◽

Cited By ~ 8

Author(s):

Isato Taki ◽

Muneaki Nakamura ◽

Kenjiro Nakama ◽

Kazutoshi Takahashi ◽

Kosaku Yamauchi

Keyword(s):

Three Dimensional ◽

Continuous Variable ◽

Valve Lift ◽

Timing Mechanism ◽

Variable Valve Lift ◽

Variable Valve ◽

Motorcycle Engine

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Flow Simulation in Port and Cylinder of a Small Motorcycle Engine With Inclined Valve

Design, Application, Performance and Emissions of Modern Internal Combustion Engine Systems and Components ◽

10.1115/ices2003-0667 ◽

2003 ◽

Cited By ~ 1

Author(s):

Ma-Ji Luo ◽

Zhen Huang ◽

Guo-Hua Chen ◽

Yuan-Hao Ma

Keyword(s):

High Speed ◽

Model Comparison ◽

Combustion Engine ◽

Three Dimensional ◽

Engine Performance ◽

Flow Simulation ◽

The Body ◽

Cylinder Pressure ◽

Cylinder Flow ◽

Motorcycle Engine

The in-cylinder flow of an internal combustion engine has great effect on the major engine performance characteristics. To understand the complex intake phenomena in a small high-speed two-valve-per-cylinder motorcycle engine, a numerical analytic model based on the KIVA-3 code is developed for the three-dimensional transient intake flow, including a moving piston and a moving inclined intake valve. The valve model adopts the body-fitted technique and the dynamic grids induced by the moving valve are automatically generated by the grid remeshing method. Turbulence is represented by k-ε model. Comparison with the measured engine cylinder pressure shows that the simulation result is generally in good agreement with the experiment. The calculated results reveal the formation of the in-cylinder tumble motion, the variation of tumble ratios, turbulence kinetic energy and the cylinder pressure. The effects of engine speeds on the intake process are also investigated. The simulation results provide important information for the design of engine intake system.

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Influence of Valve Lift and Throttle Angle on Intake Flow in a High-Performance Four-Stroke Motorcycle Engine

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2180277 ◽

2006 ◽

Vol 128 (4) ◽

pp. 934-941 ◽

Cited By ~ 8

Author(s):

Angelo Algieri ◽

Sergio Bova ◽

Carmine De Bartolo

Keyword(s):

Flow Structure ◽

High Performance ◽

Laser Doppler Anemometry ◽

Fluid Dynamic ◽

Great Influence ◽

Flow Coefficient ◽

Valve Lift ◽

Cylinder Axis ◽

Intake Flow ◽

Motorcycle Engine

A high-performance four-stroke motorcycle engine was analyzed at a steady flow rig. The aim of the work was to characterize the fluid dynamic behavior of the engine head during the intake phase. To this purpose a twofold approach was adopted: the dimensionless flow coefficient was used to evaluate the global breathability of the intake system, while the laser doppler anemometry (LDA) technique was employed to define the flow structure within the combustion chamber. The analysis gave evidence of two contrarotating vortices with axes parallel to the cylinder axis and showed variations in the flow structure when moving away from the engine head. Furthermore, the study highlighted the great influence of the throttle angle on the head fluid dynamic efficiency and how this influence changes with the valve lift. Experimental data were correlated by a single curve adopting a new dimensionless plot. Moreover, LDA measurements were used to evaluate the angular momentum of the flux and an equivalent swirl coefficient, and to correlate them to a previous global swirl characterization carried out on the same engine head using an impulse swirl meter.

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Characterization of the three dimensional turbulent flow structure of angled injection into a supersonic cross flow

10.2514/6.1996-2662 ◽

1996 ◽

Author(s):

R. Bowersox

Keyword(s):

Turbulent Flow ◽

Flow Structure ◽

Three Dimensional ◽

Cross Flow ◽

Turbulent Flow Structure

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The inlet flow structure of a conceptual open-nose supersonic drone

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410020983043 ◽

2021 ◽

pp. 095441002098304

Author(s):

Eiman B Saheby ◽

Xing Shen ◽

Anthony P Hays ◽

Zhang Jun

Keyword(s):

Flow Structure ◽

Stokes Equations ◽

Fluid Dynamic ◽

Three Dimensional ◽

Computational Fluid Dynamic Simulation ◽

Navier Stokes ◽

Ansys Fluent ◽

Navier Stokes Equations ◽

Aerodynamic Efficiency ◽

Performance Effects

This study describes the aerodynamic efficiency of a forebody–inlet configuration and computational investigation of a drone system, capable of sustainable supersonic cruising at Mach 1.60. Because the whole drone configuration is formed around the induction system and the design is highly interrelated to the flow structure of forebody and inlet efficiency, analysis of this section and understanding its flow pattern is necessary before any progress in design phases. The compression surface is designed analytically using oblique shock patterns, which results in a low drag forebody. To study the concept, two inlet–forebody geometries are considered for Computational Fluid Dynamic simulation using ANSYS Fluent code. The supersonic and subsonic performance, effects of angle of attack, sideslip, and duct geometries on the propulsive efficiency of the concept are studied by solving the three-dimensional Navier–Stokes equations in structured cell domains. Comparing the results with the available data from other sources indicates that the aerodynamic efficiency of the concept is acceptable at supersonic and transonic regimes.

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