Enhanced Method for Analyzing Pogo Stability of Liquid Rockets with Uncertain-But-Bounded Parameters

The traditional pogo analysis method while dealing with the liquid rocket with parametric uncertainty has a large calculation workload and poor accuracy, especially for heavy rockets. To remedy the deficiency, this paper presents an enhanced method applicable for any type of liquid rocket with parametric uncertainty based on the improved Rubin's model and interval analysis method. Firstly, the pogo analysis model is established by the improved Rubin's method. The uncertain parameters are viewed as variables in a bounded interval, and the upper and lower bounds of the damping ratio in the pogo analysis system can be expressed as a function of the uncertain parameters with the help of the Taylor series expansion. The coefficients in the Taylor series are derived by the orthogonality of left and right eigenvectors and Nelson's method. For the enhance method, the upper/lower bound and sensitivity of Pogo stability can be sought; in addition, an index evaluating the influence of various uncertain parameters on pogo stability is given for reducing calculation burden. The numerical simulations are provided to verify the high efficiency and accuracy of the proposed method and exhibit the effects of various parameter variations on pogo stability.