Thermal Insulation Design of a Nozzle with Blast Tube and Calculation of effective Thickness

The role of the nozzle in stability and guidance is very basic and the type of nozzle design has a great impact on the performance of the missile. In the present study, in order to create stability and easier control of the missile and to use the space created to add subsystems, it is intended to add blast tube and thermal insulation and calculate its thickness. For this purpose, a sample nozzle of the existing solid fuel rocket has been considered to add a blast tube and has been numerically analyzed. Then, two new designs of nozzles with and without using blast tube are presented and Using the existing relations analytically, the thickness of the insulators in each case is calculated and The simulation is based on it. Finally, a transient two-dimensional heat transfer analysis was performed in cylindrical coordinates for points inside the nozzle shell (behind the liner and insulation). The results show that increasing the thickness of insulation to a certain extent reduces the temperature of the nozzle shell. In the convergent-divergent nozzle designed with blast tube, this value is 0.11 in the convergent part, 0.07 in the blast tube, 0.068 in the throat and 0.11 in the divergent part. The results also show that unlike the convergent part of the nozzle, in the throat, blast and divergent parts, after passing the effective insulation thickness, the passage of time no longer has a significant effect on the nozzle shell temperature.