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### Effect of Burn Rate Exponent Variation on Ballistic Performance of Gas Generator with High Burn Rate Propellant

#### Abstract

For Gas Generator Internal Ballistics Prediction, Burn rate is important parameter as it determines the mass flow rate of the Gas Generator, which intern determines the canister pressure and ejection velocity of article launched from the canister by cold launch technique. The elemental law and empirical equation to determine the regression rate experimentally is š=ššcš , in which burn rate exponent ānā is determined from the experimental measurements on actual propellants, different propellant formulations give different regression rate (Burn rate) verses pressure relationships. The burn rate exponent is independent of propellant grain temperature and describes the influence of chamber pressure on burning rate. High values of ānā gives rapid change of burning rate with pressure, which means that even a small change in pressure will result in a substantial change in hot gas produces by Gas Generator. Since the high regression rate (25 mm/s) propellant is being used in the Gas Generator, chamber pressure varies from 10 to 27 MPa due to high mass flow rate requirement. It is important to note that this high regression rate propellant is particularly sensitive to pressure increase due to variation of burn rate exponent, particularly at high pressures. Mathematical coupling forms among pressure, Burt rate exponent (n) and regression rate, which leads to steep raise in chamber pressure after certain threshold pressure, which depends on propellant composition. This paper attempts to study and present the evaluation of burn rate index variation over pressure range 3 to 23 MPa and corresponding effect on ballistic performance of Gas Generator with high burn rate multi perforated propellant grain, which gives continues progressive mass flow rate.

#### Keywords

Gas Generator, Burn rate exponent, thresh hold pressure, ballistic prediction, multi perforated propellant grain and propellant composition.Text

DOI

10.12783/ballistics2019/33039

10.12783/ballistics2019/33039

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