Transient Thermal Analysis of Solid Propellant Rocket Motor

Abstract

Rocket engines convert the chemical energy of propellants into the kinetic energy of projectiles. Consequently, the creation of stable, high-temperature combustion of propellant is critical in itsoperation. Due to the high operating temperature and pressure, it is likely that the structural strength of the rocket’s engine component will deteriorate. Thisis particularly true for small rocket engines, because, unlike large rocket engines, the small oneshas no active cooling system. Heating of engine parts beyond its designed temperature will eventually increase the likelihood of mission failure. Hence, conducting a transient thermal analysis of the components during the design of the rocket engine is critical. The thermal analysis can also be used to estimate the thermal energy distribution in parts that come into contact with the heat flow induced by propellant combustion, aidingin the selection of the correct material and geometry for rocket nozzle construction. The present study is intended to analyse the transient heat transfer by observing the temperature distribution across the material and components of the rocket, including the propellant, inhibitor, nozzle, and outer casing. Besides that, the study was aimed at investigating the rate of temperature rise within a few seconds of rocket firing. A transient analysis package in SOLIDWORKS software was employed for this purpose. A constant temperature of 1326.85 ºCwas imposed onthe inner surface of the propellant, representing the intended peak combustion temperature, while the rest of the engine parts wereset at an ambient temperature of 26.85 ºC. The analysis revealed that the inner surface of the rocket engine casing had reached a temperature as high as 181.8 °C within 0.6 s of the rocket firing. It is also found that the surface temperature increases almost linearly with time.Keywords:Thermal Analysis, Transient Analysis, Heat Transfer, Temperature DistributionNomenclature kpropThermal conductivity of the propellant (W/(m·K))kinhThermal conductivity of the inhibitor (W/(m·K))kcaseThermal conductivity of the casing (W/(m·K))hoHeat transfer coefficient (W/(m2·K))TcombTemperature of the combustion (ºC)Tsurf,initialInitial temperature of the surface (ºC)DADiameter of A (mm)DBDiameter of B (mm)DCDiameter of C (mm)DDDiameter of D (mm)∑RTotal thermal resistance (K/W)LLength (mm)????̇Rate of heat transfer (J/s)ΔToverallSubtraction of TcombwithTsurf,initial(ºC)T1The temperature of the outer surface of KNSu propellant (ºC)T2The temperature of the outer surface of the inhibitorAbbreviations6061(Unified Numbering System (UNS) designation A96061) is a precipitation-hardened aluminium alloy, containing magnesium and silicon as its major alloying elements.T6Solution heat treated and artificially agedPVCPolyvinyl ChlorideKNSuThe potassium nitrate (KNO3)/sucrose (C12H22O11) propellant