The research presented here describes the numerical optimization of a multi-step ignition model to predict the auto-ignition of dimethyl ether (DME) in a rapid compression machine. The multi-step modeling concept is aimed at capturing the ignition behavior of new oxygenated fuel blends, where detailed or reducedmechanisms are not available. Experimental data for the ignition ofDME/O2/N2mixtures...

This dissertation: (i) develops a novel numerical method for DNS/LES of compressible, turbulent reacting flows, (ii) performs several validation simulations, (iii) studies auto–ignition of a hydrogen vortex ring in air and (iv) studies a hydrogen/air turbulent diffusion flame. The numerical method is spatially non-dissipative, implicit and applicable over a range of Mach numbers. The compressib...

This thesis deals with numerical simulations of the turbulent combustion process in Homogeneous Charge Compression Ignition (HCCI) engines. An accurate and computationally efficient Large Eddy Simulation (LES) model was developed and used throughout this thesis to investigate the development of in-cylinder turbulence, temperature stratification, onset of auto-ignition, and development of the re...

The Homogeneous Charge Compression Ignition (HCCI) combustion concept lacks direct ignition timing control, instead the auto ignition depends on the operating condition. Since auto ignition of a homogeneous mixture is very sensitive to operating conditions, a fast combustion timing control is necessary for reliable operation. Hence, feedback is needed and the crank angle of 50% burnt (CA50) has...

A new phenomenological model, the TP (Temperature Phase) model, is presented to carry out optimization calculations for turbulent diffusion combustion in a high-pressure common rail diesel engine. Temperature is the most important parameter in the TP model, which includes two parts: an auto-ignition and a soot model. In the auto-ignition phase, different reaction mechanisms are built for differ...

reduction of exhaust emissions is a major research task in diesel engine development in view of increasing concerns regarding environmental protection and stringent exhaust gas regulations. simultaneousreduction of nox emissions and particulate matter is quite difficult due to the soot/nox trade-off and isoften accompanied by fuel consumption penalties. towards this aim, automotive engineers ha...

Combustion in homogeneous charge compression ignition (HCCI) engine is controlled auto ignition of well-mixed fuel, air and residual gas. Since onset of HCCI combustion depends on the auto ignition of fuel/air mixture, there is no direct control on the start of combustion process. Therefore, HCCI combustion becomes unstable rather easily especially at lower and higher engine load. Charge strati...

where DZ is the diffusion coefficient of the mixture fraction. The scalar dissipation rate appears in many models for turbulent non-premixed combustion as, for instance, the flamelet model (Peters (1984), Peters (1987)), the Conditional Moment Closure (CMC) model (Klimenko & Bilger (1999)), or the compositional pdf model (O’Brien (1980), Pope (1985)). In common technical applications, it has be...

homogenous charge compression ignition (hcci) is a mode of combustion in ic engines in which premixed fuel and air are ignited spontaneously. there is a belief that hcci engines have a great potential to improve fuel consumption and reduce nox emissions. in this study, a single zone, zero dimensional, thermo-kinetic model has been developed and a computer program with matlab software is used to...