Burn rate (chemistry)

About: Burn rate (chemistry) is a research topic. Over the lifetime, 847 publications have been published within this topic receiving 8908 citations. The topic is also known as: Burning rate.

Burning Velocities of a Solid Propellant, via a Microwave Technique, at Elevated Pressures and Pressurization Rates.

Abstract: : Presented are the results of a research effort to directly measure, via a microwave Doppler/phase shift technique, the burning rate of solid propellant in both steady and dynamic elevated pressure environments. The recession velocity of the propellant when it burned planarly within a small rectangular waveguide was directly proportional to the time rate of change of a measured relative phase angle. This relative phase angle was based upon the phase relationship between guided microwave reflections from two surfaces, one a reference plane and the other an effective plane created by the dielectric discontinuity at the burning propellant surface. In the pressure range from 500 t0 10,000 psig, steady-state burning rate tests with a single base nitrocellulose gun propellant, M6, were sucessfully conducted in a large volume combustion fixture which incorporated a coaxial-to-waveguide adapter having unique pressure sealing microwave feedthroughs. in addition to yielding burning rate values intermediate to those from conventional closed chamber and strand burner tests, the experiments established the uncertainty in the proportionality constant linking M6 burning rate and the time derivative of relative phase angle. A one-dimensional theoretical model was formulated and, with the aid of appropriately chosen constants, yielded predictions which agreed very well with the experimentally observed behavior of a solid propellant undergoing planar burning with a waveguide.

Transient chamber flowfield simultation of a rod-and-tube configuration solid rocket motor

Abstract: A transient CFD simulation of the flowfield within a rod-and-tube solid propellant rocket motor has been developed. This model couples the fluid dynamics and heat transfer of the gas flowfield within the rocket port to the nozzle to predict the internal environment within the motor including the regression rate of the propellant. The propellant regression is described with an empirical erosive burning model based on the phenomenological heat transfer approach derived by Lenoir and Robillard 1 . The predicted propellant burn rate and consequently the chamber pressure were found to be significantly increased from the case where propellant regression was described by the simple burning law only. This augmentation of the burn rate, particularly during the early stages of the simulation, was in agreement with the trends observed in small diameter rockets where erosive burning was present. A validation of the model comparing an actual Pressure - Time plot to that predicted by the CFD model was also carried out and achieved a very high degree of correlation.

Combustion Mechanisms of Wide Distribution Propellants

Abstract: : The objective of this research is to describe the effects of oxidizer particle size distribution on the burning rate of solid propellants used in rocket motors. Current models over predict the burning rate of wide distribution (wide distribution denotes two oxidizer modes that have extreme differences in mean diameter) formulations by 40 to 200 percent indicating combustion mechanisms unique to this type of propellant. Four sets of AP/HTPB propellants were formulated to control the physical and chemical heterogenities characteristic of the propellant surface using 400 and 20 microns oxidizer particles. The propellants were tested at pressure levels from 0 to 2000 psig. An optical, distance measurement technique was developed and used to measure the local, non-steady surface deflagration of the propellant burning surface. The method uses a laser beam, synchronous detection, and closed-loop tracking to locate the surface in the hostile combustion environment. An acoustic emission technique determined average burning rates. Combustion phenomena were also accessed using high-speed photography and scanning electron microscopy. Keywords: Particle size distribution, Burning rate, Solid propellants, Rocket motors, Combustion mechanisms, AP/HTPB propellants, Laser diagnostics, Acoustic emissions, Scanning electron.

A Preliminary Study of the Wet Towel Hybrid Rocket Motor.

Abstract: To overcome defects of conventional hybrid rocket motors such as poor mass ratio and low combustion efficiency, the authors propose a new idea of design. The point of this idea is that the motor uses ‘wet towel propellant’, in which liquid oxidizer fills gap space in the fuel bed consisting of plastic fibers or films. Specific impulses of the propellants are estimated theoretically with HAN and LOX as liquid oxidizer. To investigate pressure sensitivity of the burning rates of the propellants, burning rates of LOX-polyaramid propellants are measured in a pressure range of 0.1 to 2MPa with a specially designed strand burner. A striking feature in the experimental results is that the enhancement of the burning rate with ambient pressure is as big as the pressure exponent being larger than one. Further innovation is necessary for realization of the proposed idea.