The main focus of this study is to utilize the laser Doppler velocimetry technique to measure the velocity of the particles which are emerging out from the propellant burning surface in the gas phase zone under steady state. The experiments are conducted under the high mean chamber pressure with incorporation of servomechanism feedback system to maintain the relative distance between the laser probe volume and the propellant regression surface. It is clear from the literature that only limited work has been reported on LDV of solid propellants and hardly there is any work reported on characterizing aluminized solid propellants at high mean chamber pressure using the LDV technique, which has high spatial and temporal resolution features. In order to accomplish this task, a high pressure window bomb is designed and fabricated with multiple optical access quartz windows. These quartz windows serve multiple purpose of visualizing the propellant burning with the help of camera and allow the laser beam to align over the propellant surface. Two windows in the chamber are in-line with each other so that the He-Ne laser can pass for facilitating feedback loop system. An actuation system is designed which comprises of an actuator that is capable to withstand 6800 N of the dynamic loading and attached to the propellant holder and propellant feed shaft. The actuation system is operated under two modes, viz., open loop mechanism and closed loop mechanism. In open loop mechanism, the actuator shaft is continuously advanced in the upward direction based on the burning rate data obtained using combustion photography. The combustion photography is performed up to the mean chamber pressure of 7 MPa for A2 aluminized composite solid propellants, which is the industrial grade propellant provided by the DRDL, Hyderabad. In the combustion photography method, videos are captured and processed using the MATLAB code to trace the frame-by-frame displacement of the regression surface of the solid propellant. For the actuator operations, an Arduino code is written in the Arduino workbench platform for controlling the electronic equipment. The Arduino code is written to monitor as well as record the actuator position data. The following points summarize the LDV technique implemented to measure the velocity of the particle in the gas phase of the solid propellant:
Design and fabrication of the high pressure window bomb setup and propellant holder with the propellant feed shaft to make it suitable for the laser diagnostics of the solid propellant.
An aluminized composition, A2 is tested with the open loop mechanism using LDV.
Combustion photography for the A2 compositions is done to measure the burning rate up to mean chamber pressure of 7 MPa and the burning rate data from combustion photography is used as input for the actuation system under open loop system.
Deducing the mean burning rate from the ensemble measured velocity of the particles in the gas phase zone.
Mean burning rate from LDV have shown good agreement when compared with combustion photography and the strand burning data provided by DRDL Hyderabad.
It can be concluded that the LDV of solid propellant has shown promising result for the aluminized propellant burning rate estimation under steady state combustion at high mean chamber pressure. The full thesis will include LDV data under open loop and closed loop mechanism for different aluminized propellant composition, viz., A1, A2, A3 and comparison of open loop and closed loop LDV data with combustion photography and strand burning rate data.