Numerical investigation on regression rate and thrust regulation behaviors of a combined solid rocket motor with aluminum-based fuel

This paper focuses on investigating “combustion instability,” a phenomenon that mainly involves the interaction of the propellant flames with the acoustic oscillations prevalent in full-scale rocke...

Mean Burning Rate Variation in Composite Propellant Combustion Due to Longitudinal Acoustic Oscillations

The present work involves the use of Laser Doppler Velocimetry (LDV) technique to measure the acoustic admittance of aluminized composite solid propellant (AP/HTPB/Al) by experimentally measuring the instantaneous velocities of the particles of solid propellant during burning while the acoustic pressure oscillations are being imposed. Both velocity fluctuations and pressure fluctuations are measured synchronously. The probe volume of the laser is maintained at a constant distance from the burning surface by using a linear actuator. Tests were conducted for two aluminized composite solid propellants at low frequency ranges (130-312 Hz) of the longitudinal acoustic modes and mean chamber pressures ranging from 1 to 4 MPa. A rotary valve is designed to acoustically excite the chamber to the required resonant frequency. It was found that admittance rises with frequency and peaks around 260 Hz and then falls. The use of linear actuator mechanism significantly improves the velocity data rate (number of data points). Maintaining the probe volume at 800 to 900 µm above the propellant surface is very crucial to determine the admittance accurately. Test results revealed that a good agreement between the steady state mean burning rates with the window bomb experiments is achieved. The measured mean burn rates under imposed acoustic pressure oscillations shows the augmentation up to 55%. The admittance measured for the metallized composite propellant using this technique and the comparison with T-burner shows good agreement. The comparison of responses with LDV and T-burner and the augmentation factor due to acoustic oscillations using LDV are reported for the first time.

Measurement of admittance and acoustic augmentation of burning rate of composite solid propellants using Laser Doppler Velocimetry

Experiments have been carried out to investigate the effect of cowl length variation on performance characteristics of a single expansion ramp nozzle. The performance parameters were estimated for ...

Cowl Length Variation on Performance Characteristics of a Single Expansion Ramp Nozzle

Acoustic pressure oscillation effects on mean burning rates of plateau propellants

Oscillatory Pressure Effect on Mean Burning Rates of Solid Propellant Combustion at Low Frequency Conditions

The present investigation has been made in an attempt to improve the off design SERN performance using secondary injection. SERN provides an optimum performance at cruise hypersonic Mach number, but at low Nozzle pressure Ratio (NPR), the nozzle flow is strongly over-expanded which gives rise to large downward-directed gross thrust vectors resulting strong nose up pitching moment which affects the stability of the vehicle and also there is large frictional drag inside the nozzle. Wall static pressure were measured to estimate the various performance parameters such as surface axial force, normal force, pitching moment. Schlieren flow visualization technique was adopted to qualitatively understand the effect of injection in SERN. While comparing between baseline nozzle (without injection) and SERN with injection, an oblique shock is generated by the influence of injection which impinges over the ramp surface and separate the unfavorable over-expanded flow. As a result, the favorable gross thrust over the ramp surface aids to reduce the frictional drag, specifically at NPR 6, the increase of axial thrust is twice than that of without injection case. Moreover, the downward directed gross thrust and the thrust vector angle is decreased, therefore the downward directed normal force is reduced consequently diminishes the pitching moment value. The increase in injection mass flow rate results in increasing the angle and strength of the oblique shock slightly which cause the minor improvement in performance parameters is observed between the 2% and 3% injectant mass flow rate. 

Balusamy Kathiravan

Papers

Mean Burning Rate Variation in Composite Propellant Combustion Due to Longitudinal Acoustic Oscillations

Oscillatory Pressure Effect on Mean Burning Rates of Solid Propellant Combustion at Low Frequency Conditions

Cowl Length Variation on Performance Characteristics of a Single Expansion Ramp Nozzle

Acoustic pressure oscillation effects on mean burning rates of plateau propellants

Performance Characteristics of Single Expansion Ramp Nozzle with Secondary Injection