Numerical and Experimental Analysis of the Intake Flow in a High Performance Four-Stroke Motorcycle Engine: Influence of the Two-Equation Turbulence Models

2007 ◽  
Vol 129 (4) ◽  
pp. 1095-1105 ◽  
Author(s):  
Angelo Algieri ◽  
Sergio Bova ◽  
Carmine De Bartolo ◽  
Alessandra Nigro
Keyword(s):  
Flow Field ◽  
Combustion Chamber ◽  
High Performance ◽  
Laser Doppler Anemometry ◽  
Fluid Dynamic ◽  
Turbulence Models ◽  
Mean Flow ◽  
Intake System ◽  
Cylinder Flow ◽  
Motorcycle Engine

An experimental and numerical analysis of the intake system of a production high performance four-stroke motorcycle engine was carried out. The aim of the work was to characterize the fluid dynamic behavior of the engine during the intake phase and to evaluate the capability of the most commonly used two-equation turbulence models to reproduce the in-cylinder flow field for a very complex engine head. Pressure and mass flow rates were measured on a steady-flow rig. Furthermore, velocity measurements were obtained within the combustion chamber using laser Doppler anemometry (LDA). The experimental data were compared to the numerical results using four two-equation turbulence models (standard k-ε, realizable k-ε, Wilcox k-ω, and SST k-ω models). All the investigated turbulence models well predicted the global performances of the intake system and the mean flow structure inside the cylinder. Some differences between measurements and computations were found close to the cylinder head while an improving agreement was evident moving away from the engine head. Furthermore, the Wilcox k-ω model permitted the flow field inside the combustion chamber of the engine to be reproduced and the overall angular momentum of the flux with respect to the cylinder axis to be quantified more properly.

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

2006 ◽  
Vol 128 (4) ◽  
pp. 934-941 ◽  
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.

Experimental investigation of the air flow in a simplified underhood environment

2021 ◽  
pp. 095440702110597
Author(s):  
Randi Franzke ◽  
Simone Sebben ◽  
Emil Willeson
Keyword(s):  
Flow Field ◽  
Laser Doppler Anemometry ◽  
Fluid Dynamic ◽  
Air Flow ◽  
Measurement Data ◽  
Quality Measurement ◽  
Flow Distribution ◽  
Lateral Position ◽  
Reference Case ◽  
Lateral Direction

In this paper, a simplified underhood environment is proposed to investigate the air flow distribution in a vehicle-like set-up and provide high quality measurement data that can be used for the validation of Computational Fluid Dynamic methods. The rig can be equipped with two types of front openings representative for electrified vehicles. Furthermore, it is possible to install differently shaped blockages downstream of the fan to imitate large underhood components. The distance between the blockages and the fan can be varied in longitudinal and lateral direction. The measurements are performed with Laser Doppler Anemometry at a fixed distance downstream of the fan. The results show that the lack of an upper grille opening in the configuration for a battery electric vehicle has a notable impact on the flow field in the reference case without any downstream blockage. However, the differences in the flow field between the two front designs become less when a downstream obstruction is present. The longitudinal and lateral position of the blockages have a minor impact on the flow field compared to the shape of the obstacle itself.

Applications of EARSM Turbulence Models to Internal Flows

2012 ◽  
Author(s):  
O. Z. Mehdizadeh ◽  
L. Temmerman ◽  
B. Tartinville ◽  
Ch. Hirsch
Keyword(s):  
Reynolds Stress ◽  
High Performance ◽  
Eddy Viscosity ◽  
Computational Cost ◽  
Turbulence Models ◽  
Industrial Applications ◽  
Mean Flow ◽  
Viscosity Models ◽  
Stress Models ◽  
Corner Flows

Turbulence modeling remains an active CFD development front for turbomachinery as well as for general industrial applications. While DNS and even LES still seem out of reach within the typical industrial design cycle due to their high computational cost, RANS-based models remain the workhorse of CFD. Currently, the most widely used models are Linear Eddy-Viscosity Models (LEVM), despite their known limitations for certain flow complexities. Therefore, extending the reliability of eddy-viscosity models to more complex flows without significantly increasing the computational cost can immediately contribute to more reliable CFD results for wider range of applications. This, in turn, can further reduce the need for costly tests and consequently can reduce the product development cost. A promising approach to achieve this goal is using Explicit Algebraic Reynolds Stress Models (EARSM), obtained through a simplification of the full Differential Reynolds Stress Models (DRSM), and can be perceived as an extension of LEVMs by including the non-linear relation between the turbulence stress tensor, the mean-flow gradient and the turbulence scales. These models are thus less demanding than DRSM, yet capable of capturing more complex turbulence features, compared to LEVM, such as anisotropy in the normal stresses. This may be particularly important in corner flows, for instance, in the hub-blade regions or in diffusers. This work explores the application of EARSM models to a double diffuser and a high-performance centrifugal compressor stage (HPCC). The results are compared to available experimental data [1,2] showing the importance of including the anisotropy of turbulence in the model, particularly in presence of turbulent corner flows in a diffuser. Furthermore, the EARSM results are also compared to results from the commonly used SST turbulence model. The CFD comparison includes details of the flow structure in the diffuser, where the most noticeable impact from the use of EARSM turbulence models is expected.

Experimental and Numerical Investigation of a Cold Turbulent Jet Impinging on a Hot Plate

2012 ◽  
Author(s):  
D. I. Maldonado ◽  
J. K. Abrantes ◽  
L. F. A. Azevedo ◽  
A. O. Nieckele
Keyword(s):  
Flow Field ◽  
Laser Doppler Anemometry ◽  
Turbulence Models ◽  
Impinging Jets ◽  
Reynolds Stresses ◽  
Hot Plate ◽  
Mean Velocity ◽  
Velocity Statistics ◽  
Reliable Assessment ◽  
Anisotropic Structures

Impinging jets are an efficient mechanism to enhance wall heat transfer, and are widely used in engineering applications. The flow field of an impinging jet is quite complex and it is a challenging case for turbulence models validation as well as measurements techniques. In the present work, a detailed investigation of a cold jet impinging on a hot plate operating in the turbulent flow regime was conducted. The flow field was characterized by both Laser Doppler Anemometry and Particle Image Velocimetry (PIV) techniques in order to collect 1st and 2nd order velocity statistics to allow a reliable assessment of the numerical simulations. Comparison was performed with two turbulence methodologies: RANS (κ–ω SST model) and LES (Dynamic Smagorinsky model). The comparison was performed to assess LES feasibility and accuracy in capturing the anisotropic structures that several tested RANS models missed. The mean velocity, instantaneous velocity, Reynolds stresses and Nusselt profiles obtained numerically are compared with experimental data. A physical insight about the general flow dynamics was obtained with the extensive amount of information available from the LES.

Differential stress modelling of turbulent flows in model reciprocating engines

1997 ◽  
Vol 211 (1) ◽  
pp. 59-77 ◽  
Author(s):  
C. J. Lea ◽  
A. P. Watkins
Keyword(s):  
Experimental Data ◽  
Turbulent Flows ◽  
Turbulence Intensity ◽  
Laser Doppler Anemometry ◽  
Turbulence Models ◽  
Apparent Difference ◽  
Mean Flow ◽  
Differential Stress ◽  
Reciprocating Engines ◽  
The Mean

A study is made here of the application of a differential stress model (DSM) of turbulence to flows in two model reciprocating engines. For the first time this study includes compressive effects. An assessment between DSM and k-ɛ results is made comparing with laser Doppler anemometry experimental data of the mean flow and turbulence intensity levels during intake and compression strokes. A well-established two-dimensional finite-volume computer code is employed. Two discretization schemes are used, namely the HYBRID scheme and the QUICK scheme. The latter is found to be essential if differentiation is to be made between the turbulence models. During the intake stroke the DSM results are, in general, similar to the k-ɛ results in comparison to the experimental data, except for the turbulence levels, which the DSM seriously underpredicts. This is in contrast to a parallel set of calculations of steady in-flow, which showed significant gains from using the DSM, particularly at the turbulence field level. The increased number of grid lines employed in those calculations contribute to this apparent difference between steady and unsteady flows, but cycle- to-cycle variations are more likely to be the primary cause, resulting in too high levels of turbulence intensity being measured. However, during the compression stroke the DSM returns vastly superior results to the k-ɛ model at both the mean flow and turbulence intensity levels. This is because the DSM generates an anisotropic shear stress field during the early stages of compression that suppresses the main vortical structure, in line with the experimental data.

Free Jet in Confined Combustion Chamber: Numerical Model for Industrial Application in Low NOx Burners

2005 ◽  
Author(s):  
Emanuela Colombo ◽  
Fabio Inzoli ◽  
Enrico Malfa
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Reynolds Number ◽  
Combustion Chamber ◽  
Fluid Dynamic ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Dynamic Features ◽  
Low Reynolds ◽  
High Reynolds

The present work is focused on the prediction of the fluid dynamics behaviour for natural gas burners characterized by low NOx emissions. The fluid dynamics in the combustion chamber is investigated in order to look for the condition under which it is possible to obtain a diluted combustion. The experimental data used as reference come from two set of tests related to different isothermal flow behaviour: high Reynolds number (Re = 68000) and lower Reynolds number (Re = 5427). Many turbulence models are examined in order to validate high and low Reynolds case. The k-ω models implemented by Wilcox in 1998 seems to properly predict the fluid dynamics behaviour of the jet for high Reynolds numbers, while, for low Reynolds jets, a modification needs to be introduced. The numerical analysis for low Reynolds number, based on an unstructured 2D axial symmetrical grid, shows that no two-equation turbulence models fit the experimental data for low Reynolds jet. Based on the evidence that at low Reynolds number the hypothesis of homogeneous isotropic small turbulence eddy is not valid a modification of k-ω turbulence model’s closure constant has been proposed. This leads to a better agreement with the experimental data. The results demonstrate that great attention needs to be taken and invested in the identification of the turbulence models used in CFD and in the proper tunneling (of the closure coefficient for the turbulence model) that need to be computed case by case accordingly with the specific turbulence level and fluid dynamic features of the jet itself.

Numerical Simulation Study of the Influence of Structural Parameters of Combustion Chamber on In-Cylinder Flow Field of Diesel Engine

2013 ◽  
Vol 860-863 ◽  
pp. 1729-1732
Author(s):  
Guo Cheng Li ◽  
Ping Sun ◽  
Peng Hu
Keyword(s):  
Diesel Engine ◽  
Flow Field ◽  
Combustion Chamber ◽  
Structural Parameters ◽  
Volume Ratio ◽  
Initial Boundary ◽  
Swirl Flow ◽  
Swirl Ratio ◽  
Depth Ratio ◽  
Cylinder Flow

Based on the entity model of the type 4B26 diesel engine, calculated by CFD FIRE and combined with the software BOOST for the initial boundary conditions, the influence of combustion chamber structural parameters, such as boss height, surface-volume ratio and diameter-depth ratio of combustion chamber, on in-cylinder flow field of diesel engine was investigated. The results show that the influence of the boss height on flow field in the cylinder and the transient swirl ratio is obvious, and increasing the boss height is beneficial to urge the formation of mixture rapidly. Reducing the surface-volume ratio is beneficial for improving the maximum transient swirl ratio, and the air strength maintains well also, but has little influence to the retentivity of the swirl intensity. Meanwhile, reducing the diameter-depth ratio does not only improves the air flow movement strengthen in the combustion chamber, but also enhances the maximum transient swirl ratio, and the retentivity of swirl flow movement is satisfying.

scholarly journals The Development of the Mean Flow and Turbulence Structure in an Annular S-Shaped Duct

1994 ◽  
Author(s):  
K. M. Britchford ◽  
J. F. Carrotte ◽  
S. J. Stevens ◽  
J. J. McGuirk
Keyword(s):  
Reynolds Stress ◽  
Laser Doppler Anemometry ◽  
Reynolds Shear Stress ◽  
Turbulence Models ◽  
Test Facility ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Mean Velocity ◽  
Curvature Effects ◽  
The Mean

This paper describes an investigation of the mean and fluctuating flow field within an annular S-shaped duct which is representative of that used to connect the compressor spools of aircraft gas turbine engines. Data was obtained from a fully annular test facility using a 3-component Laser Doppler Anemometry (LDA) system. The measurements indicate that development of the flow within the duct is complex and significantly influenced by the combined effects of streamwise pressure gradients and flow curvature. In addition CFD predictions of the flow, using both the k-ε and Reynolds stress transport equation turbulence models, are compared with the experimental data. Whereas curvature effects are not described properly by the k-ε model, such effects are captured more accurately by the Reynolds stress model leading to a better prediction of the Reynolds shear stress distribution. This, in turn, leads to a more accurate prediction of the mean velocity profiles, as reflected by the boundary layer shape parameters, particularly in the critical regions of the duct where flow separation is most likely to occur.

Intake Valve and In-Cylinder Flow Development in a Reciprocating Model Engine

1986 ◽  
Vol 200 (2) ◽  
pp. 143-152 ◽  
Author(s):  
C Vafidis ◽  
J H Whitelaw
Keyword(s):  
Flow Field ◽  
Laser Doppler Anemometry ◽  
Axial Flow ◽  
Normal Stresses ◽  
Intake Valve ◽  
Inlet Valve ◽  
Piston Bowl ◽  
Flow Development ◽  
Model Engine ◽  
Cylinder Flow

Measurements of three velocity components have been obtained by laser Doppler anemometry at the exit plane of the intake valve and inside the cylinder of a model engine motored at 200 r/min with a compression ratio of 7.7 and both axisymmetric and off-centre valves with flat and bowl-in-piston configurations. The results indicate that during early intake the valve flow is influenced by piston geometry and its proximity to the cylinder head. With the flat piston the TDC flow field is influenced by the intake-generated axial flow pattern but not by the tangential motion, induced by the off-centre valve, which decays around inlet valve closure. The breakdown of the intake-generated vortices is accompanied by redistribution of the normal stresses which, during compression, tend towards homogeneity. Inside the piston bowl, a vortex is induced during early intake and decays later in the induction stroke to a uniform flow field which is transformed during late compression by the squish effect.

Study of a Gas Turbine Combustion Chamber: Influence of the Mixing on the Flame Dynamics

2004 ◽  
Author(s):  
Christophe Duwig ◽  
Laszlo Fuchs
Keyword(s):  
Flow Field ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
New Technologies ◽  
Mean Flow ◽  
Flamelet Model ◽  
Demand Growth ◽  
Eddy Simulation ◽  
Flame Dynamics ◽  
Gas Turbine Combustion

The new challenge of the Gas Turbine industry is to develop new technologies for meeting electricity demand growth and reducing harmful emissions. Thus a better understanding of the combustion phenomenon and an improvement in simulation capabilities are needed. Large Eddy Simulation tools brought the hope of meeting these two conditions and enabling the design of safe and clean burners. In the present paper, the influence of the unsteady mixing on the flame in a Lean Premixed Pre-vaporized combustor have been investigated. A premixed combustion flamelet model has been extended to non-uniform fuel/air mixtures cases. Extra terms in the equations, their effects and the modeling issues are discussed. Additionally, the effects of mixing on the flow field in an industrial gas turbine combustion chamber have been investigated. The mean flow field has been found to be weakly sensitive to the mixing effects. It is deduced that the modeling of the mixing and the combustion can be decoupled in the RANS framework. Regarding the flame dynamics, all runs show similar characteristic frequencies. However, different details of models lead to differences in the temperature fluctuations. This suggests that a rigorous modeling of the thermo-acoustic sources (e.g. heat-release fluctuations) requires accurate modeling of the mixing/combustion coupling, for handling accurately the dynamics of the flame.

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