| In this thesis,the numerical simulation of non-premixed hydrogen/air rotating detonation combustion was conducted.Firstly,the model design of non-premixed rotating detonation combustor was carried out,and the streamline form of laval nozzle is determined.On this basis,the mixing characteristics of fuel and air in non-premixed rotating detonation combustor are studied,and the influence of combustion chamber structure parameters and boundary conditions on mixing quality is mastered.Finally,under the guidance of the influence law of mixing quality in cold flow field,the model structure of rotating detonation combustor was optimized,and the boundary conditions were defined.The specific work contents are as follows:(1)In order to improve the mixing quality of the mixture in the rotating detonation combustor and accumulate the mixture heights suitable for the stable propagation of rotating detonation wave,the model design of the non-premixed rotating detonation combustor was carried out under the conditions of total inlet pressure of 0.2MPa,total temperature of 300 K,air mass flow rate of 0.1kg/s and equivalence ratio of 1.Combined with Bykovskii empirical formula,the dimensions of annular combustor are designed as follows: annular chamber width 5mm,inner diameter 90 mm,outer diameter 100 mm and axial length 50 mm.Considering the uniformity of the flow field,the laval nozzle streamline with straight line and arc transition is adopted: the inlet width of laval nozzle is 2.4mm,the throat width is 0.7mm,the outlet width is the same as the annular chamber width of 5mm,the transition arc radius is half of the width of the section position,and the contraction and expansion half angle are 10 °respectively.(2)In order to further improve the cold mixing quality of rotating detonation combustor,the influence of structural parameters and boundary conditions(such as the expansion angle of laval nozzle,fuel injection position,inlet mass flow rate and combustor outlet back pressure)on the mixing characteristics of fuel and air in rotating detonation combustor was studied.The results show that the mixing quality of cold flow field can be improved by decreasing the angle of laval nozzle and moving forward the injection position of fuel.However,when the inlet mass flow exceeds the rated inlet flow rate or the back pressure at the exit of the combustor is lower than the design pressure(1atm),the distance required for fuel air mixing increases and the fuel mixing quality decreases.(3)In order to explore the formation and propagation characteristics of rotating detonation wave under non-premixed condition,the physical model and boundary conditions with the best mixing quality were selected to simulate the hot flow field of rotating detonation combustion.The results show that stable single wave is formed in the rotating detonation combustor under the physical model and boundary conditions.The formation of non-premixed rotational detonation wave requires detonation,collision,quenching,re-initiation and stabilization.The reason why the non-premixed rotating detonation wave can re-detonate is related to the local high pressure zone on the outer wall.After the detonation wave is stabilized,the average thrust at the exit of the combustor is 63.2N and the specific impulse is 2213.36 s. |
