ANALYSIS OF COMBUSTION PROCESS OF A CHARGE OF NATURAL GAS IN LABORATORY COMBUSTION CHAMBER
The article contains an analysis of investigation results of the combustion process of a charge of natural gas mixture with air. Investigations were carried for charges of stoichiometric composition and lean ones for various initial pressures in the combustion chamber. Ignition of the mixture was indicated by an ignition plug supplied from a direct ignition device. Measurements comprise a digital record of the pressure course in the chamber. Values of pressure increment in the chamber during the combustion process were analyzed. A diagram of pressure increment values dependent on charge composition and initial pressure in the combustion chamber was elaborated. Evaluation of particular results permits to determine potential possibilities of gas - air charge combustion.
Measurements and Multidimensional Modeling of Gas-Wall Heat Transfer in a S.I. Engine
The computational fluid dynamics codes, which help to predict the behaviour of combusting gas in reciprocating engines, need, as boundary conditions for the momentum and energy equations, to approximate wall frictions and heat transfer between gas and walls. The purpose of this work is to outline the physical parameters which affect the heat transfer in spark ignited engines, and then to validate a multidimensional model which takes these parameters into account
Combustion Diagnostics by Means of Multizone Heat Release Analysis and NO Calculation
In this paper a combustion diagnostic method is presented where measured pressure data is used to calculate the heat release, local temperatures and concentrations of NO and other species. This is done by a multizone model where the lambda value, i.e. 1/equivalence ratio, in each zone can be chosen arbitrarily. In homogenous charge engines lambda is given by the global air/fuel ratio. The local lambdas during initial combustion in stratified charge and diesel engines have to be estimated either as an average value or with a chosen distribution. One new zone of each local lambda is generated and the temperature, volume and species in all old zones are updated at each time step of calculation. In this paper the model is demonstrated by using pressure data from premixed and direct injected stratified charge natural gas SI engines and from a DI diesel engine. The pre-mixed data is used to validate the model as such while the ambition in the stratified charge and diesel cases has been to find the average local lambda that gives the same NOx emission as measured. The emphasis in the latter cases has been to study the influence on average local lambda of the duration of the fuel injection. Early injected fuel seems to burn at slightly leaner mixtures than later injected. (Less)