CFD Modeling of IC Engines

( Introduction of Engine Models 

in Star CCM, FLUENT and OpenFOAM)

1. Scope of CFD Modeling for IC Engine

  • CFD modeling of IC engines is essential to asses the combustion of new mechanism of fuel and air inlets and emissions are reduced at lower cost of analysis
  • CFD) simulations are important for development of modern IC engine:spark-ignited, two-stroke, diesel injection, homogeneous charge compression ignition (HCCI) and dual-fuel reciprocating engines.
  • CFD analysis helps to optimize engine performance using commercial CFD software
  • CFD results provides insights for further improvements in engine technologies

 2. CFD Softwares for Engine Modeling 

  • CFD modeling some IC Engine problem is challenging  like  in-cylinder simulation.
  • It comprises combination of high-speed flows with complex combustion phenomenon
  •  For CFD modeling,  mesh motion need a very high level of mass conservation with  very small time scales (fractions of a crank-angle degree (milliseconds)
  • The numerical have to be selected properly to achieve stable residuals with reasonable time step.
  • Selection turbulence model and thermal radiation model
  • Selection of complex physics models is essential
    • Fuel injection Model : Lagrangian spray, droplet-wall interactions, wall films
    • Combustion Model: Ignition, flame propagation, emissions formation, knock

 1) Star CCM 

    1. Star ICE module is used for IC Engine Modeling
    2. Star CCM IC engine provies Automatic meshing
    3. Cold Flow to maximize trapped air mass
    4. Charge motion to improve mixing of inducted air and injected fuel
    5. Design Exploration is used to automatically optimize engine performance
    6. Validation of some results with correlation and experimental data
    7. Combustion Set up








3. Step for Modeling of IC Engines

Step 1: Create the  Solid Model of of IC Engines which includes cylinder, inlet and outlet manifolds

Step 2: Generate mesh in ANSYS mesher or ANSYS poly hexmesher

Step 3: Set the boundary conditions by selecting IC Engine modules

  • Specify the engine parameters crank position, compression ratio, piston time, intake and outlet valve positions


3.1 CAD Model of IC Engine

  • For making geometries of SI/CI engines, any CAD tools can bee used
  • Select the CFD domain as per scope of analysis considering inlet and outlet ducts

3.2 Meshing of IC Engine:

  • Generally tetrahedral elements are generally used around the valves and dynamic hexa-hedral element inc dynamic (moving) part of cylinder
  • Advanced Poly hex meshing  can be used for less computational cost

Polyhex Meshing of Combustion Engine

Multiphase Meshing of Diesel Engine Combustion

3.3 Boundary Conditions and Selection of Combustion models

  • Select the appropriate boundary conditions at the inlet or outlet
  • For SI engine:
    •  you can define stoichiometric air and fuel mixture at the inlet
    • Define ignition energy required the combustion
    • Define the outlet as pressure outlet
    • Select SI engine models
    • Select turbulence model and energy equations
    • Select suitable premixed combustion models
    • Using the UDF, define the piston position with dynamic mesh and crank parameters
  • For  Diesel (CI) engine :

    •  you can define air  at the inlet
    • Define suitable spray models
    • Define the outlet as pressure outlet
    • Select CI engine models
    • Select turbulence model and energy equations
    • Select multi-phase model ( Eulerian and Lagrangian)
    • Select suitable non-premixed combustion models
    • Using the UDF, define the piston position with dynamic mesh and crank parameters
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5.4 Results and Analysis

  • Using CFD simulation, we can get  the contours of velocity, pressure and temperature for different position of crank
  • CFD results can be compared with theoretical or experimental results

References on CFD Modeling of IC Engines:


2 thoughts on “CFD Modeling of IC Engines”

  1. The present paper provides a contribution to the CFD modelling of reacting flows in IC engines fueled with natural gas. Despite the fact that natural gas has been widely investigated into in the last decades, the literature still lacks reliable models and correlations to be exploited so as to efficiently support the design of internal combustion engines. The paper deals with the development of an accurate CFD model, capable of capturing the effects of the engine working conditions and mixture compositions on the combustion process.
    The CFD model is based on the Extended Coherent Flame Model (ECFM) combustion model coupled to a laminar flame speed one through a user subroutine, which replaces the commonly adopted empirical correlations. The flame speed values have been derived from the application of a reaction mechanism for natural gas-air-residual gases mixtures.


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