Experimental and theoretical study on characteristics of pulse excitation in T-burners

Pulse excitation is the key to measure the pressure-coupling response function of composite propellant. It is also a key trigger factor for nonlinear combustion instability. This paper aims at understanding characteristics of pulse excitation in T-burners. Pulse excitation is provided by black powder (BP). D² law is used to calculate BP burning properties. Firstly, the experimental pressure history of a pulse excitation is analyzed. Pressure pulse and mean pressure increment are introduced to describe pulse excitation. Secondly, the modified zero-dimension model and one-dimension model of pressure pulse are established based on energy conservation and modification. The results of models indicate that the modified zero-dimensional model can accurately predict the pressure pulse. The modified zero-dimension model demonstrates that the pressure pulse is determined by pulse build-up time threshold, volume coefficient, effective weight fraction of BP, weight of BP et. al. When burning time of BP is larger than the threshold, volume coefficient is equal to 2, and effective weight fraction of BP is less than 1. The pressure pulse is approximately linear correlation with weight and effective weight fraction of BP. Otherwise, volume coefficient is larger than 2, and effective weight fraction of BP is equal to 1. The pressure pulse is approximately linear correlation with volume coefficient and BP weight. Thirdly, a zero-dimensional prediction model of mean pressure is established based on conservations of energy and mass. The prediction models of pressure pulse and mean pressure are validated by T-burner experiments. Finally, effects of BP burning properties on pressure pulse and mean pressure increment are studied. The results show that both pressure pulse and mean pressure increment increase with increasing BP weight, linearly. The pressure pulse is more sensitivity to the variations of burning time of BP. As burning time of BP decreases, the mean pressure increment gradually increases to the maximum, and the pressure pulse can become a very large value.