Study And Design Of A Rocket Motor Inner Flow Field Simulation For The Case Of Dual Pulse Motor

Solid rocket propulsion is still until today the most used propulsion technique,and this is because it presents a lot of advantages over its traditional competitor(liquid rocket propulsion)mainly the design simplicity and compactness,operational readiness and longer storage times.But although this is oldest propulsion technique,the research in this field is still ongoing until today because unlike liquid propellants combustion,the solid propellants combustion cannot be modulated over time to create a real time desired thrust.Although there are ways to change the thrust such as changing the burning surface area or using different propellants,when it comes to more requiring applications,these techniques fall short.One of the techniques that gained momentum recently is to create different thrust periods called pulses by separating different propellant grains inside the case by means of a Pulse Separation Device(PSD),thus using the 1st grain for boost,and the other grain for a later sustain or boost.The kind of rocket motors relying on this technique are called Dual Pulse Motors(DPMs).In this research project,at a first stage a preliminary modulated design of a dual pulse solid rocket motor allowing its division into several fundamental units(or modules)and facilitating its manufacturing process has been proposed.At a later stage,one phase steady state numerical simulations were performed to study the influence of the PSD(Pulse Separation Device)type(two types were considered,axial and radial)and the propellant grain internal diameter on the internal flow features.The simulations were carried out on the ANSYS Fluent commercial code platform using density-based solver.The k-ω-SST model was chosen for turbulence modelling with the combustion products assumed to be a perfect gas.The results show that there are almost no differences during the 1St pulse operation,but when it comes to the 2nd pulse operation the analysis of streamlines,pressure distribution,turbulent kinetic energy,axial velocity profiles and axial shear stress shows much more significant differences.As a matter of fact,the axial PSD type case shows more aggressive flow environment in the beginning of operation considering higher turbulence kinetic energy and axial velocity levels near wall at the immediate downstream of the PSD,later these levels fall dramatically to levels comparable to those of no PSD presence case.On the opposite side,the radial PSD type case shows stable levels of the previously mentioned parameters throughout the entire operation of the rocket motor.