Solid Propellant Burning Rate Measurement in a Closed Bomb
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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Experiments show that the burning rate of solid propellants is a function of the pressure under which the burning takes place. An often used method to determine that burning rate function is to burn a sample of the propellant in a closed container and to register the corresponding pressure-time data. With the aid of formulas from thermodynamic theory these observations can be manipulated to yield the desired parameters of the burning rate function. This analysis is typically done under a number of restrictive assumptions, e.g., the assumption of constant temperature in the container throughout the experiment. In spite of such assumptions the corresponding algorithms published are complicated and an error analysis of the results has apparently never been reported. In the present paper new formulas are derived under relaxed assumptions. With the aid of these formulas the data analysis is reduced to a curve fitting task. For such tasks standard theories and computer programs are available, which furnish the unknown parameters of the burning rate function together with estimates of their variances and co-variances. The new formulas can be replaced by simpler ones under conditions, which are controllable by the design of the experiment. It is found that for such simplifications the temperatures behavior is not relevant. In general the simplifications are permissible if the maximum pressure achieved during the experiment remains essentially smaller than the chemical energy released per unit volume of the propellant. The latter is typically of the order of 10 to 10th power Pa 10 to 5th power. An example illustrates the application of the new algorithm.
- Test Facilities, Equipment and Methods
- Ammunition and Explosives
- Combustion and Ignition