Development of computer based tools (such as expert system) for the kinetics of combustion reactions which will be used to generate data on reaction kinetics. Experimental work carried out under contract JOUE-CT90-0036 will be used as input for the development of this expert system.
On the basis of experience gained regarding the pyrolytic reactions of hydrocarbons, the process of partial combustion of light hydrocarbons was studied. This was done by completing an existing kinetic diagram by the addition of the elementary kinetic acts, which are significant and important defining the interactions of radicals and oxygenated compounds. Although containing considerable kinetic simplifications, the diagram which was developed features approximately 60 chemical species and over 1000 elementary reactions. It can describe pyrolysis and partial oxidation, define the limits of ignition and characterise the combustion of light hydrocarbons.
Elementary reactions of propane oxidation have been studied to give the main reaction classes of combustion processes. Propane gives clear evidence of the competing alternatives of decomposition, oxygen addition, isomerisation and cyclisation to form C3H6O. From experimental data on neopentane oxidation, it is possible to define rate values for elementary reaction steps and standard kinetic parameters for oxygen addition and internal isomerisation of alkyl and peroxy radicals. This can then be extended to heavier hydrocarbons and main reaction classes. The analysis shows the strong correlations between knocking properties and fuel structures. Methyl transfer and methyl shift reactions seem to be particularly important when fuel hydrocarbon contains quaternary and tertiary carbon atoms.
KINGAS, a computer code for use in modelling gas flows, has been developed which enables the appropriate Arrhenius parameters to be estimated.
The kinetics and mechanisms of elementary chemical reactions in combustion are vital components for the understanding of efficiency and pollution-free energy generation. A combined project has therefore been set up (KEENEX) where KEENEX-COMMODEX (contract JOUE-CT90-0035) will develop computer based tools for kinetics in combustion processes and KEENEX-CHEMCOM (contract JOUE-CT90-0036) will carry out extensive experimental work in this field which will serve as an input for the modelling tasks in KEENEX-COMMODEX. The resulting computer-based tools will be very useful for the generation of thermal kinetic data as required in research related to combustion technologies (engines, gas turbines, ovens, kilns, furnaces).
Work in this part of the project mainly consists of the development of computer tools which can derive data on reaction mechanisms, thermodynamic properties and kinetic parameters of reaction rates which are needed to simulate combustion processes. The most important part is the generation of reaction mechanisms. An expert system will be developed for exhaustive mechanism design and thermal kinetic parameters determination: on the other hand automatic methods will be designed for simplification of detailed mechanisms in order to derive kinetic schemes the size of which is suitable for numerical simulation within flow models.
Further on data on thermodynamic properties of molecules and radicals will be needed as input in the expert system. In addition for each elementary reaction in the expert system the best available value of rate parameters will be established.
The developed computer tools will be tested to demonstrate their abilities in application cases relevant to internal combustion engines. The combustion process will be modelled using various kinetic schemes and flow models in order to compare solutions obtained with different schemes and to estimate the computer tools abilities for ideal reactor operating conditions as close as possible to engine operation.
Funding SchemeCSC - Cost-sharing contracts
92078 Paris La Défense