EFFECTS OF DROPLET BREAKUP, HEATING AND EVAPORATION ON AUTOIGNITION OF DIESEL SPRAYS. S. Martynov 1 , S. Sazhin 2 , C. Crua 2 , M. Gorokhovski 3 , A. Chtab 4 , E. Sazhina 2 , K. Karimi 2 , T. Kristyadi 2 , M. Heikal 2
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S. Martynov1, S. Sazhin2, C. Crua2, M. Gorokhovski3, A. Chtab4,
E. Sazhina2, K. Karimi2, T. Kristyadi2, M. Heikal2
1Departmentof Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK
2 Sir Harry Ricardo Laboratories, Internal Combustion Engines Group, University of Brighton, Brighton, BN2 4GJ, UK
3LMFA UMR 5509 CNRS Ecole Centrale de Lyon, 36 avenue Guy de Collongue, 69131 Ecully Cedex, France
4CORIA UMR 6614 CNRS University of Rouen, 76 801 Saint-Etienne du Rouvray, France
Models for heating and evaporation of droplets
Shell autoignition model
Spray breakup models
Initiation: CnH2m + O2 2R*
Propagation: R* R* + P
R* R* + B
R* R* + Q
R* + Q R* + B
Branching: B 2R*
Termination: R* out
where R* is the radical,
B is the branching agent,
Q is the intermediate product,
P is the final product, consisting of
CO, CO2, H2O.
The pre-exponential constant for the reaction rate for the production of the branching agent was set to Af4= 3 106 (Sazhina et al, 2000).
where B1,eq = 10 is the break-up time of the conventional WAVE model, and a+ is a dimensionless acceleration parameter.
Validation test cases
Results – autoignition delay time
Effect of droplet heating and evaporation models Effect of breakup model Effect of the Shell model constant Effect of the fuel temperature Effect of the gas temperature Effect of grid size
Predicted and experimentally measured ignition delay times versus in-cylinder pressure; in base-line computations mesh with 20 x 48 cells was used, 1000 droplet parcels were injected at pressure 160MPa into a cylinder with initial pressure 6.2MPa. If not stated otherwise, the temperature of injected fuel was 375K, the initial gas temperature wais 750K, the modified WAVE breakup model, ETC liquid phase model and AS gas phase model were used.
Results – local spray properties
time = 0.98 ms time = 1.49 ms time = 1.73 ms time = 1.98 ms
Spatial distribution of droplets (top row) and gas temperature field (bottom row) at four moments of time. Mesh with 20 x 48 cells was used; 1000 droplet parcels with initial temperature 375K were injected at 160MPa into air at 6.2MPa and 750K; the modified WAVE breakup model, ETC liquid phase model and AS gas phase model were used. Droplets are shown with diameters magnified 500 times.
The authors are grateful to the European Regional Development Fund Franco-British INTERREG IIIa (Project Ref 162/025/247) and the Indonesian Government (TPSDP, Batch III) for financial support