AN OPEN-SOURCE FRAMEWORK FOR ADVANCED TURBULENT COMBUSTION AND RADIATION MODELLING IN IC ENGINES
Open Access
- Author:
- Paul, Chandan
- Graduate Program:
- Mechanical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 08, 2018
- Committee Members:
- Daniel C. Haworth, Dissertation Advisor/Co-Advisor
Daniel C. Haworth, Committee Chair/Co-Chair
Robert Santoro, Committee Member
Stephen R. Turns, Committee Member
Philip J. Morris, Outside Member - Keywords:
- Radiative heat transfer
Compression-ignition engine
Spectral radiation modeling
Turbulence-radiation interaction
Stochastic modeling
Stepwise-gray spectral model
Transported probability density function (tPDF) method - Abstract:
- Detailed radiation modelling in advanced high-efficiency piston engines is recently getting attention due to their higher operating pressures and higher levels of exhaust gas recirculation (EGR), which make molecular gas radiation more prominent (absorption coefficient proportional to participating species concentration). Advanced high-efficiency engines also are expected to function closer to the limits of stable operation, where even small perturbations to the energy balance can have a large influence on system behavior. Here several different spectral radiation property models (including line-by-line – LBL) and radiative transfer equation (RTE) solvers (including photon Monte Carlo – PMC) have been implemented in an OpenFOAM-based engine CFD code. The influence of turbulence-radiation interactions (TRI) is determined by comparing results obtained using local mean values of composition and temperature to compute radiative emission and absorption with those obtained using a particle-based transported probability density function (tPDF) method. Simulations have been performed for full-load (peak pressure ~200 bar) and part-load (peak pressure ~85 bar) operation of a heavy-duty diesel engine with different levels of EGR. Differences in computed temperature fields, NO and soot levels, and wall heat transfer rates are shown for cases with and without TRI. Computed radiative emission and reabsorption with TRI are higher compared to those obtained without TRI for the same operating condition. However, with TRI, the increase in radiative reabsorption is greater than the increase in radiative emission. Hence, with consideration of TRI, the net radiative heat loss is lower than for the no-TRI case for the same operating condition. Finally, guided by results from PMC/LBL (PMC RTE solver with LBL spectral model) radiation model on Volvo 13-liter heavy-duty diesel engine, a simplified stepwise-gray spectral model in combination with P1 RTE solver is proposed. Using this proposed model, radiative emission, reabsorption and radiation reaching the walls are computed at part-load and full-load operating conditions with different levels of EGR and soot. The results are compared with those of PMC/LBL, P1/FSK and P1/Gray radiation models to assess the proposed model’s accuracy and computational cost. The results show that the proposed P1/StepwiseGray model can calculate reabsorption locally and globally with less than 10% error (with respect to PMC/LBL) at a small fraction of the computational cost of PMC/LBL (a factor of 30) and P1/FSK (a factor of 15). In contrast, error in computed reabsorption by the P1/Gray model is as high as 60%. It is expected that the simplified model should be broadly applicable to high-pressure hydrocarbon-air combustion systems, with or without soot.