Combustion Instability in a 175mm Gun Firing Chamber,
ARMY ARMAMENT COMMAND ROCK ISLAND ILL
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On the basis of a previously unpublished work, and an unpublished report that heat transfer to a gun tube was decreased in the presence of additives, and varied according to the type of additive, it was hypothesized that 1 All combustion is inherently unstable, and that therefore instabilities would be found in gun chamber combustion. 2 Heat transfer to the walls is enhanced by combustion instabilities. 3 Inert additives are often used to control instabilities in similar conditions in rocket motors, and that therefore wear and erosion additives might have the same role in this case, in controlling the instabilities and thus heat transfer. 4 Alternatively, inert additives have purely a passive role of shielding the walls to give a lower heat transfer. To initiate a test of this hypothesis, it was found that a M113 Gun was available which had provision to measure amplitude and type of pressure waves occurring during combustion, and in which the effect of additives on instabilities could be observed. This paper reports the results of these tests.