It is necessary to carry out research on acceleration effects

 

The aluminum-containing composite propellant burns in the acceleration field, which is divided into a dynamic process and a steady-state process. In the dynamic process, when the combustion starts, the ignition temperature of AP is low and burns first. The heat released makes the HTPB binder in a molten state, and the heat is transferred to the depth of the combustion surface of the grain to preheat the aluminum particles and form in AP The accumulation and phase change process is completed in the pocket of aluminum, and aluminum particles collide with adjacent aluminum particles to bond together to form agglomerated aluminum particles that are many times larger than the original aluminum particles, which are also called aluminum balls.

Studies have shown that the lower part of the aluminum ball close to the combustion surface has a lower flow velocity, while the upper part of the aluminum ball has a higher flow velocity. According to Bernoulli’s theorem, the pressure p on the lower surface of the aluminum ball is higher than the pressure pc on the upper surface, so the aluminum ball has a total The pressure difference F exists. It is also known that the acceleration force acting on the aluminum ball is F, which plays the role of the differential pressure lifting force. It overcomes the acceleration force a and lifts the aluminum ball to fly away from the combustion surface; when F plays the role of differential pressure resistance , That is, F overcomes Fpdt and forces the aluminum ball to stay on the combustion surface and form a pit on the combustion surface. There is a small air gap λ between the aluminum ball and the bottom of the pit, as if the aluminum ball floats in the pit. Since the temperature of the aluminum ball is close to the gas temperature, and the temperature of the combustion surface is much lower than that of the aluminum ball, the heat energy is fed back to the combustion surface through the air gap λ. Therefore, the aluminum ball staying on the combustion surface to form a heat source is an important reason for the increase in the burning rate. The greater the acceleration value, the higher the aluminum powder content, the smaller the static burning rate, the more aluminum particles stay on the combustion surface, the more heat feedback, the higher the effect burning rate r value, and the average burning rate The ratio r value is also greater. The combustion performance of 2010 propellant is very sensitive to acceleration. Under the condition of acceleration of 70g, the average effect burning rate ratio r is as high as 1.515, which is mainly caused by two factors: high aluminum powder content and low static burning rate. The acceleration sensitivity of the propellant is mainly manifested as the increase of the burning rate of the propellant, which in turn induces the increase of the pressure in the combustion chamber, the shortening of the combustion time and the change of the internal ballistic performance. The results of this study are of practical significance for evaluating propellant formulations and predicting the internal ballistic performance of solid rocket motors. The acceleration sensitivity of the burning rate poses a threat to the safety of the rocket in flight. It is necessary to carry out further research on acceleration effects.

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