No abstract

Ecole Nationale Supé rieure de Mé canique et d'Aé rotechnique, Futuroscope Chasseneuil Cedex, FranceThis work presents results of quenching distance and heat flux measurements during the head-on quenching of transient laminar stoichiometric methane=air flame in the pressure range 0.05-1.7 MPa. The results of direct visualization have been used to measure the quenching distance and to prove the relationship relating the quenching distance and heat flux to the wall over the global combustion reaction rate. It is shown that quenching distance decreases from 0.43 to 0.016 mm with pressure rise from 0.05 to 1.7 MPa. The maximum wall heat flux increases nonlinearly from 0.35 to 2.3 MW=m 2 with pressure rise from 0.05 to 1.7 MPa. The dimensionless value of the heat flux depends only slightly on the pressure and decreases from 0.3 to 0.2 with rise of pressure in this pressure range. Flame-wall interaction time is about constant and equal to 0.15-0.155 ms in all ranges of pressure variation.

No abstract

Experimental and modelling studies of ion formation during combustion of propane/air mixtures are presented. The positive and negative ions mass/charge spectra in propane/air stoichiometric flame at atmospheric pressure are recorded in the range from 0 to 512 atomic mass units. The C 2 H 3 O + and HCO − 2 ions are found to be the most abundant ionic species in the flame front region. By increasing the distance from the flame front the ion composition changes significantly. In the burnt gas region the H 3 O + , NO + , CO − 3 , HCO − 3 ions are found to be the major charged species. To explain the experimental results the extended kinetic model describing the ion formation in flame and in the extraction system of the mass-spectrometer as well as ion-soot interaction is developed. It is shown that the ionic clusters, which are observed experimentally, form during the adiabatic expansion in the extraction system, and the presence of soot particles may change the total positive and negative ion concentrations in the gas phase.

No abstract

No abstract

In this work, spark plug and corona discharge of 3-20 ms in duration have been used for ignition of stoichiometric and lean fuel methane= air mixtures. Comparison of spark plug and corona ignition abilities shows that corona discharge allows more efficient ignition with less discharge energy. It is proved experimentally that corona ignition provides faster combustion due to larger discharge volume, generation of turbulence around the discharge electrodes promoting combustion and assistance to the flame front propagation through the combustion chamber. In our experimental conditions corona allows ignition and flame propagation regime in quiescent extremely lean fuel mixture of equivalence ratio 0.52 that cannot be realized using more powerful spark.

No abstract