The Effect of Subgrid Modeling on the In-Cylinder Unsteady Mixing Process in a Direct Injection Engine

2001 ◽  
Author(s):  
Kazuo Sone ◽  
Suresh Menon
Keyword(s):  
Large Scale ◽  
Direct Injection ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Mixing Process ◽  
Simulation Code ◽  
Ic Engine ◽  
Engine Simulation ◽  
Air Mixing ◽  
Linear Eddy Model

Abstract The process of fuel-air mixing in the Direct Injection Spark Ignition (DISI) engine is highly unsteady and three-dimensional with wide cycle-to-cycle variations involving vaporization of droplets and its interaction with large-scale turbulent flow field. Although the majority of the past numerical studies of mixing in an Internal Combustion (IC) engines have employed Reynolds-Averaged Navier-Stokes (RANS) equations with empirical turbulence model, here we have implemented a Large-Eddy Simulations (LES) with the Linear-Eddy Model (LEM) for subgrid scalar mixing into a commercial IC engine simulation code (KIVA-3V). This study shows that when time-accurate effects are included significantly different results are obtained. These differences between the original KTVA-3V and the new KIVALES in predicting the in-cylinder turbulent fuel-air mixing are discussed. LES shows highly unsteady, anisotropic in-cylinder fuel-air mixing process compared to the original KIVA-3V. The implications for combustion is also discussed.

Effect of Subgrid Modeling on the In-Cylinder Unsteady Mixing Process in a Direct Injection Engine

2003 ◽  
Vol 125 (2) ◽  
pp. 435-443 ◽  
Author(s):  
K. Sone ◽  
S. Menon
Keyword(s):  
Direct Injection ◽  
Three Dimensional ◽  
Mixing Process ◽  
Ic Engine ◽  
Eddy Simulation ◽  
Spatial Features ◽  
Air Mixing ◽  
Local Grid ◽  
Mixed Field ◽  
Direct Injection Spark Ignition

Fuel-air mixing in a direct injection spark ignition (DISI) engine occurs in a highly unsteady, turbulent and three-dimensional flow. As a result, any cycle-to-cycle unsteady variation in the mixing process can directly impact the performance of the DISI engine. To study the unsteady process in these engines, we have developed and implemented a large-eddy simulation (LES) approach with an innovative subgrid scalar mixing model based on the linear-eddy mixing (LEM) model into a commercial IC engine code (KIVA-3V). Time-averaged results of the simulations using the new LES version (KIVALES) are compared to the steady-state predictions of the original KIVA-3V. Significantly different in-cylinder turbulent fuel-air mixing is predicted by these two methods. Analysis shows that KIVALES resolves spatial features larger than the grid and that the subgrid kinetic energy adjusts to the LES resolution. As a result, KIVALES captures a highly unsteady, anisotropic fuel-air mixing process whereas a more diffused mixed field is predicted by the original KIVA-3V. This ability of KIVALES is attributed to the subgrid closure which scales the subgrid dissipation with the local grid size and thus, decreases the overall dissipation in the flow.

Experimental Investigation to Study Convective Mixing, Spatial Uniformity, and Cycle-to-Cycle Variation During the Intake Stroke in an IC Engine

1999 ◽  
Vol 122 (3) ◽  
pp. 493-501 ◽  
Author(s):  
Woong-Chul Choi ◽  
Yann G. Guezennec
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Large Scale ◽  
Three Dimensional ◽  
Data Set ◽  
Ic Engine ◽  
Engine Simulation ◽  
Spatial Uniformity ◽  
Intake Stroke ◽  
Advective Mixing

The work described in this paper focuses on experiments to quantify the initial fuel mixing and gross fuel distribution in the cylinder during the intake stroke and its relationship to the large-scale convective flow field. The experiments were carried out in a water analog engine simulation rig, and, hence, limited to the intake stroke. The same engine head configuration was used for the three-dimensional PTV flow field and the PLIF fuel concentration measurements. High-speed CCD cameras were used to record the time evolution of the dye convection and mixing with a 1/4 deg of crank angle resolution (and were also used for the three-dimensional PTV measurements). The captured sequences of images were digitally processed to correct for background light non-uniformity and other spurious effects. The results are finely resolved evolution of the dye concentration maps in the center tumble plane. The three-dimensional PTV measurements show that the flow is characterized by a strong tumble, as well as pairs of cross-tumble, counter-rotating eddies. The results clearly show the advection of a fuel-rich zone along the wall opposite to the intake valves and later along the piston crown. It also shows that strong out-of-plane motions further contribute to the cross-stream mixing to result in a relatively uniform concentration at BDC, albeit slightly stratified by the lean fluid entering the cylinder later in the intake stroke. In addition to obtaining phase-averaged concentration maps at various crank angles throughout the intake stroke, the same data set is processed for a large number of cycle to extract spatial statistics of the cycle-to-cycle variability and spatial non-uniformity of the concentration maps. The combination of the three-dimensional PTV and PLIF measurements provides a very detailed understanding of the advective mixing properties of the intake-generated flow field. [S0742-4795(00)00103-4]

Numerical Simulation of Porous Medium Internal Combustion Engine

2011 ◽  
Author(s):  
Arash Mohammadi ◽  
Ali Jazayeri ◽  
Masoud Ziabasharhagh
Keyword(s):  
Combustion Engine ◽  
Direct Injection ◽  
Combustion Process ◽  
Three Dimensional ◽  
Internal Combustion ◽  
Flammability Limits ◽  
Ic Engine ◽  
Operational Conditions ◽  
Engine Simulation ◽  
Homogeneous Combustion

Porous media (PM) has interesting advantages compared with free flame combustion due to the higher burning rates, the increased power range, the extension of the lean flammability limits, and the low emissions of pollutants. Future internal combustion (IC) engines should have had minimum emissions level, under possible lowest fuel consumption permitted at all operational conditions. This may be achieved by realization of homogeneous combustion process in engine. In this paper, possibility of using PM in direct injection IC engine, with cylindrical geometry for PM to have homogeneous combustion, is examined. A three-dimensional numerical model for the regenerative engine is presented in this study based on a modified version of the KIVA-3V code that is very popular for engine simulation. Methane as a fuel is injected directly inside hot PM that is assumed mounted in cylinder head. Very lean mixture is formed and volumetric combustion occurs in PM. Mixture formation, pressure, temperature distribution in both phases of PM and in-cylinder fluid with the production of pollutants CO and NO, in the closed part of the cycle is studied.

Unsteady Three-Dimensional Analysis of Inlet Distortion in a Transonic Fan

2006 ◽  
Author(s):  
Peng Sun ◽  
Guotal Feng
Keyword(s):  
Shock Wave ◽  
Total Pressure ◽  
Large Scale ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Inlet Distortion ◽  
Flow Loss ◽  
Large Scale Vortex ◽  
Total Temperature ◽  
Transonic Fan

A time-accurate three-dimensional Navier-Stokes solver of the unsteady flow field in a transonic fan was carried out using "Fluent-parallel" in a parallel supercomputer. The numerical simulation focused on a transonic fan with inlet square wave total pressure distortion and the analysis of result consisted of three aspects. The first was about inlet parameters redistribution and outlet total temperature distortion induced by inlet total pressure distortion. The pattern and causation of flow loss caused by pressure distortion in rotor were analyzed secondly. It was found that the influence of distortion was different at different radial positions. In hub area, transportation-loss and mixing-loss were the main loss patterns. Distortion not only complicated them but enhanced them. Especially in stator, inlet total pressure distortion induced large-scale vortex, which produced backflow and increased the loss. While in casing area, distortion changed the format of shock wave and increased the shock loss. Finally, the format of shock wave and the hysteresis of rotor to distortion were analyzed in detail.

Flow Characteristics in a Three-Dimensional Rectangular Channel With a Pair of Ribs Placed Symmetrically at the Channel Walls

2000 ◽  
Author(s):  
M. Singh ◽  
P. K. Panigrahi ◽  
G. Biswas
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Energy Equations

Abstract A numerical study of rib augmented cooling of turbine blades is reported in this paper. The time-dependent velocity field around a pair of symmetrically placed ribs on the walls of a three-dimensional rectangular channel was studied by use of a modified version of Marker-And-Cell algorithm to solve the unsteady incompressible Navier-Stokes and energy equations. The flow structures are presented with the help of instantaneous velocity vector and vorticity fields, FFT and time averaged and rms values of components of velocity. The spanwise averaged Nusselt number is found to increase at the locations of reattachment. The numerical results are compared with available numerical and experimental results. The presence of ribs leads to complex flow fields with regions of flow separation before and after the ribs. Each interruption in the flow field due to the surface mounted rib enables the velocity distribution to be more homogeneous and a new boundary layer starts developing downstream of the rib. The heat transfer is primarily enhanced due to the decrease in the thermal resistance owing to the thinner boundary layers on the interrupted surfaces. Another reason for heat transfer enhancement can be attributed to the mixing induced by large-scale structures present downstream of the separation point.

scholarly journals Large-Scale Flow in Micro Electrokinetic Turbulent Mixer

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 813 ◽  
Author(s):  
Keyi Nan ◽  
Zhongyan Hu ◽  
Wei Zhao ◽  
Kaige Wang ◽  
Jintao Bai ◽  
...  
Keyword(s):  
Flow Field ◽  
Electric Conductivity ◽  
Large Scale ◽  
Three Dimensional ◽  
Mixing Process ◽  
Mean Flow ◽  
Velocity Fluctuations ◽  
Two Fluids ◽  
Large Scale Flow ◽  
Particle Imaging

In the present work, we studied the three-dimensional (3D) mean flow field in a micro electrokinetic (μEK) turbulence based micromixer by micro particle imaging velocimetry (μPIV) with stereoscopic method. A large-scale solenoid-type 3D mean flow field has been observed. The extraordinarily fast mixing process of the μEK turbulent mixer can be primarily attributed to two steps. First, under the strong velocity fluctuations generated by μEK mechanism, the two fluids with different conductivity are highly mixed near the entrance, primarily at the low electric conductivity sides and bias to the bottom wall. Then, the well-mixed fluid in the local region convects to the rest regions of the micromixer by the large-scale solenoid-type 3D mean flow. The mechanism of the large-scale 3D mean flow could be attributed to the unbalanced electroosmotic flows (EOFs) due to the high and low electric conductivity on both the bottom and top surface.

Turbulence Evaluation Within the Secondary Flow Region of a Turbine Cascade

1992 ◽  
Author(s):  
D. G. Gregory-Smith ◽  
Th. Biesinger
Keyword(s):  
Large Scale ◽  
Energy Equation ◽  
Three Dimensional ◽  
Flow Region ◽  
Velocity Fields ◽  
Navier Stokes ◽  
Turbine Cascade ◽  
Mean Velocity ◽  
Turbulent Kinetic Energy Equation ◽  
Transition Modelling

Three-dimensional turbulent and mean velocity fields have been measured within a large-scale axial turbine cascade. The results indicate a complex turbulent flow field especially within the secondary vortex. The turbulence is shown to he significantly non-isotropic, and the production and dissipation terms in the turbulent kinetic energy equation have been evaluated in order to illustrate the unusual turbulence behaviour. Comparisons with a Navier-Stokes computation indicate areas for improvement in turbulence and transition modelling.

Potential Flow Field Generated by Downstream Moving Bars and Propagated on a Turbine Blade at Low Reynolds Number

2011 ◽  
Author(s):  
Ve´ronique Penin ◽  
Pascale Kulisa ◽  
Franc¸ois Bario
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Numerical Study ◽  
Three Dimensional ◽  
Potential Effect ◽  
Navier Stokes ◽  
Turbine Cascade ◽  
Wake Interaction ◽  
Rotor Stator Interaction ◽  
The Stability

During the last few decades, the size and weight of turbo-machinery have been continuously reduced. However, by decreasing the distance between rows, rotor-stator interaction is strengthened. Two interactions now have the same magnitude: wake interaction and potential effect. Studying this effect is essential to understand rotor-stator interactions. Indeed, this phenomenon influences the whole flow, including the boundary layer of the upstream and downstream blades, ergo the stability of the flow and the efficiency of the machine. A large scale turbine cascade followed by a specially designed rotating cylinder system is used. Synchronised velocity LDA measurements on the vane profile show the flow and boundary layer behavior due to the moving bars. To help the general understanding and to corroborate our experimental results, numerical investigations are carried out with an unsteady three dimensional Navier-Stokes code. Moreover, the numerical study informs about the potential disturbance to the whole flow of the cascade.

Numerical Simulation of Direct Injection Engine With Using Porous Medium

2012 ◽  
Author(s):  
Arash Mohammadi ◽  
Ali Jazayeri ◽  
Masoud Ziabasharhagh
Keyword(s):  
Porous Medium ◽  
Direct Injection ◽  
Combustion Process ◽  
Packed Bed ◽  
Published Data ◽  
Mixture Formation ◽  
Flammability Limits ◽  
Ic Engine ◽  
Engine Simulation ◽  
Wide Range

Porous media (PM) has interesting advantages in compared with free flame combustion due to the higher burning rates, the increased power range, the extension of the lean flammability limits, and the low emissions of pollutants. Future clean internal combustion (IC) engines should have had minimum emissions level (for both gaseous and particulate matter) under possible lowest fuel consumption permitted in a wide range of speed, loads and having good transient response. These parameters strongly depend on mixture formation and combustion processes which are difficult to be controlled in a conventional engine. This may be achieved by realization of homogeneous combustion process in engine. This paper deals with the simulation of direct injection IC engine equipped with a chemically inert PM, with cylindrical geometry to homogenize and stabilize the combustion of engine. A 3D numerical model for PM engine is presented in this study based on a modified version of the KIVA-3V code. Due to lack of any published data for PM engines, numerical results of thermal and combustion wave propagation in a porous medium are compared with experimental data of lean methane-air mixture under filtration in packed bed and very good agreement is seen. For PM engine simulation methane as a fuel is injected directly inside hot PM that is assumed, mounted in cylinder head. Lean mixture is formed and volumetric combustion occurs in PM and in-cylinder. Mixture formation, pressure and temperature distribution in both phases of PM and in-cylinder fluid with the production of pollutants CO and NO and also effects of injection time in the closed part of the cycle are studied.

Computational Studies on Charge Stratification and Fuel-Air Mixing in a New Two-Stroke Engine

2005 ◽  
Author(s):  
Shamit Bakshi ◽  
T. N. C. Anand ◽  
R. V. Ravikrishna
Keyword(s):  
Initial Conditions ◽  
Computational Study ◽  
Three Dimensional ◽  
The State ◽  
Operating Conditions ◽  
Injection System ◽  
Critical Parameters ◽  
Mixing Process ◽  
Air Mixing ◽  
Stroke Engine

In this paper, detailed computational study is presented which helps to understand and improve the fuel-air mixing in a new direct-mixture-injection two-stroke engine. This new air-assisted injection system-based two-stroke engine is being developed at the Indian Institute of Science, Bangalore over the past few years. It shows the potential to meet emission norms such as EURO-II and EURO-III and also deliver satisfactory performance. This work proposes a comprehensive strategy to study the air-fuel mixing process in this engine and shows that this strategy can be potentially used to improve the engine performance. A three-dimensional compressible flow code with standard k–ε turbulence model with wall functions is developed and used for this modeling. To account for the moving boundary or piston in the engine cylinder domain, a non-stationary and deforming grid is used in this region with stationary cells in the ports and connecting ducts. A flux conservation scheme is used in the domain interface to allow the in-cylinder moving mesh to slide past the fixed port meshes. The initial conditions for flow parameters are taken from the output of a three-dimensional scavenging simulation. The state of the inlet charge is obtained from a separate modeling of the air-assisted injection system of this engine. The simulation results show that a large, near-stoichiometric region is present at most operating conditions in the cylinder head plane. The state of the in-cylinder charge at the onset of ignition is studied leading to a good understanding of the mixing process. In addition, sensitivity of two critical parameters on the mixing and stratification is investigated. The suggested parameters substantially enhance the flammable proportion at the onset of combustion. The predicted P–θ from a combustion simulation supports this recommendation.

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