Development of a Flight Stage Command System Pressure Regulator and Modeling Using LMS IMAGINE AMESIM

摘要

Command system is an integral part of any flight or ground test stage of a launch vehicle. High pressure command gas is stored in gas bottles at either ambient or cryogenic temperatures and then expanded using single or multi-stage pressure regulation system. Prediction of pressure regulator behavior during transient and steady state is of great importance. There had been many efforts earlier to predict pressure regulator behavior using governing differential equations and solving them by either numerical techniques or standard MATLAB/FORTRAN commands, but stability and performance of these models are highly dependent on various factors like friction coefficients, damping, inertia and real gas behavior, etc. The ability and accuracy of modeling tools for prediction of system dynamics and its behavior at various operating conditions have increased to a greater extent and becoming extremely popular these days. This paper presents a dynamic model, generated using LMS IMAGINE AMESIM as a modeling tool. This model is used for generating and optimizing various design parameters, i.e., Coulomb friction, size of damping orifice, reference spring load, biased spring load and inertia of moving parts, etc. Dynamic model is generated using standard modules available in software library, and each sub-module represents either a pneumatic chamber or a physical phenomenon like inertia of moving elements, friction and/or inherent damping of the system. Design parameters thus generated are then utilized to develop an actual flight worthy pressure regulator. Comparison of simulation results with actual hardware test results shows a close match during the transients and in steady phase. A series of tests including flow and slam tests were conducted and the performance of pressure regulator is captured using continuous data acquisition system on various hardware's and a comparison of results is also presented here. Parametric study on regulator stability by varying various system parameters is also conducted. The model is found to be very helpful in understanding behavior of flight stage command system pressure regulator and can be further utilized to generate system-level models. It can also be utilized in understanding behavior of pressure regulators in series and parallel, which is otherwise very complicated. An extension to this model can be a plausible system-level model, which will further augment understanding of entire command system and also unravel many system related queries.