Primary air entrainment characteristics for a self-aspirating burner: Model and experiments

Experimental and theoretical investigations of primary air entrainment characteristics of a self-aspirating burner are presented. Emphasis was made on experiments, which were performed using both hot and cold tests; and a correlation between them is proposed. The level of primary air entrainment is measured using an oxygen sensor and a particle image velocimetry system. Experimental results are used to validate the predicted ones, which are obtained by constructing a theoretical model basing on simple momentum and energy conservation principles. It is found that the model predictions agree with the experimental data for a similar system. Primary air entrainment is a function of fuel gas flow rate, fuel gas type, injector geometry, mixing tube geometry, and burner port geometry. The level of primary air entrainment increases with increasing momentum rate of the fuel gas. The hot test gives about a 22 percentage point (37% relative) lower PA value than that of the cold test because of the preheating effect caused by combustion. A first correlation between the hot test and the cold one for primary air entrainment is proposed. It is recommended that the preheating effect caused by combustion in a self-aspirating burner not be neglected when designing the burner.