A study of combustion improvement for flame propagation in a tube by using combination flow and mixture injection

Experiments on combustion of lean mixtures in the vicinity of flammability limit have acquired importance from the viewpoint of development of new kinds of combustion system with low fuel consumption and low emissions. It is well known that the combustion characteristics near the lean limit are instability and low heat release rate. Therefore, it is necessary to improve the combustion behaviour by using several techniques. Experiments have been carried out to examine the influence of combination flow and mixture injection on flame behaviour and flame propagation speed for lean premixed propane-air mixtures in a combustion tube. The mail conclusions are as follows: 1) The Average flame speed with the swirl flow is remarkably increased as compared with the case of laminar flow. 2) The Average flame speed by using the combination flow is bigger than that of the swirl flow. 3) By changing the combination flow intensity, it is possible to control the flame speed. 4) The flame speed by using injection of premixed mixture to flame front is higher than that of laminar flame speed without the mixture injection. 5) The most suitable conditions exit for combustion improvement near the flammability limit by using the mixture injection.