The issue of abnormal high initial-pressure inside the launch tube in a small-scale ejector was discussed. A calculation method based on a zero-dimensional internal-ballistics model was proposed,considering the combustion heat-release reaction of the rich gas,and the method has the advantages of simple principles,small calculation amount and fast calculation speed. A calculation program was developed using the Matlab. The effectiveness and accuracy of the numerical model were validated by comparing with ejection test results. Based on the above research,the phenomena of secondary combustion in the launch tube were further studied. The study shows that the time-curves of the pressure of launch tube and the acceleration of missile exhibit obvious double-peak effects whether secondary combustion occurs or not. Additionally,the secondary-combustion effect not only significantly increases the peak value of the first peak but also leads to a decrease in the peak value of the second peak. Furthermore,a sharp drop of pressure in the launch tube to a low value occurs after the peak value of the first peak,and the secondary-combustion effect also significantly affects the ejection velocity and the missile ejection-time. Further research shows that by increasing the initial volume of the launch tube and reducing the rich gas content,the effect of secondary combustion on the low-pressure chamber pressure and missile acceleration can be reduced. This study provides theoretical support for the design of internal ballistics in ejector system,and has a certain degree of universality and reference value.
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