The Reduction Method Based On Eigenvalue Analysis For Combustion Mechanisms And Its Applications

As the development of computer and numerical calculation theory, the numericalsimulation became important research tool in combustion science and engin-eering. Butbecause of the large quantity of calculation, the computational fluid dynamicssoftware can only coupling small mechanisms to calculate the multidimensionalcomplex combustion models. And the combustion kinetic mechanisms of hydrocarbonsbecame more and more complicated as the increase of the fuels’molecular weight, oftenincluding hundreds of species. The common mechanisms with several steps are toosimple to obtain accuracy result and provide enough information to satisfy the demandin engineering application. As a result, the mechanisms reduction is an important project incombustion science and engineering applications.This paper reduced detail mechanisms with the idea which contains skeletalreduction and global reduction. A new eigenvalue analysis-based method is presentedfor the construction of skeletal reduced mechanisms from complex chemical reactionmechanisms. This method considered the impact of the timescales to the whole reactionsystem in the formulation of the simplification procedure. a reduced mechanism of21species and83elementary reactions for combustion of methane–air was generated fromdetailed mechanism GRI-1.2. Two reduced mechanism with26species,120reactionsand30species,140reactions were generated from GRI-3.0under different errorthreshold. The reduced skeletal mechanisms agreed favorably with the detailed modeland also agreed experiments results with high accuracy. The method of computationalsingular perturbation was chosen for the global reduction of complicated chemicalmechanisms. This method has been simply introduced in this paper, including thecorrection of this method. The global reduced mechanisms for the combustion ofhydrogen, methane and ethylene were generated respectively. The contrasts ofcalculated results between global reduced mechanisms and detail mechanisms provedthe feasibility of this method in small molecular hydrocarbon fuels.Decane is an important component used in surrogate formulations of kerosene. Adetail mechanism with118species and527reactions was used in this paper. It was firstreduced into a skeletal mechanism with70species and327reactions. Then we reducedthe skeletal mechanism by computational singular perturbation method. we discussed the differences of this method between before and after modification. The modifiedmethod was used to generated two global mechanisms. The two global mechanismswere based on different operating conditions: low temperature ignition process and hightemperature burning process. The simulate result was verified against experimentsrespectively. On that basis, a synthetically global mechanism with38species and34reaction was obtained which show good agreement with experiment in both ignition andburning flame process. The reduction and result indicated that the mechanisms reducedby the eigenvalue analysis skeletal reduction method and the modified computationalsingular perturbation method had good agreement with detail mechanisms andexperiments, and also reduced the computation time. All this was the foundation offurther application in engineering.