Abstract: In order to improve the combustion efficiency of paraffin-based fuels in the hybrid rocket motor, the more accurate formula of the combustion efficiency was derived from the combustion heat of propellant, and the effects of the catalysts, injection ways and the length of aft-combustion chamber on the combustion efficiency were studied through the motor ground tests and thermodynamic calculations. The results show that the combustion efficiency is positively correlated with the characteristic velocity efficiency, but the more accurate formula is used by the square of characteristic velocity efficiency. Some catalysts are beneficial to combustion efficiency which was improved by 32.8%, 43.3% and 52.0% by adding Catocene, CuCr₂O₄ and C₃₆H₇₀CoO₄, respectively. The swirl effect of swirling injector is better than turbine rotor injector and spiral injector, so the mixture of the fuel and the oxidizer can be enhanced, which is more beneficial to improve the regression rate and combustion efficiency of the paraffin-based fuel. The combustion efficiency can be improved by increasing the length of the aft-combustion chamber, but the heat loss and flow loss increased for longer aft-combustion chamber, leading to the reduction of specific impulse. The combustion efficiency reached 89.3%, when length of the aft-combustion chamber was 80mm. Therefore, three effective methods to improve the combustion efficiency of paraffin-based fuels are proposed.

Key words: Hybrid rocket motor;Paraffin-based fuel;Combustion efficiency;Combustion organization;Injector

摘要： 为了提高含石蜡燃料在固液混合发动机中的燃烧效率，从推进剂的燃烧热值定义出发推导了燃烧效率表达式，并通过地面试车实验和热力学计算研究了催化剂、氧化剂喷注方式、后燃室容积对燃烧效率的影响。结果表明：推进剂的燃烧效率变化趋势可由特征速度效率表示，但更为精确的燃烧效率表达式应为特征速度效率的平方；燃料中添加卡托辛、亚铬酸铜和硬脂酸钴可使燃烧效率分别提高32.8%,43.3%和52.0%；相比涡轮转子和螺旋喷注器，离心式喷注器的旋流效果更好，可促进燃料与氧化剂掺混，从而更有利于提高含石蜡燃料的退移速率和燃烧效率；增加后燃室长度可提高燃烧效率，但较长的后燃室散热损失和流动损失较高从而导致比冲较低，当后燃室长度为80mm时，燃烧效率可达89.3 %，因此得出了三种有效提高含石蜡燃料燃烧效率的方法。

关键词: 固液混合发动机;含石蜡燃料;燃烧效率;燃烧组织;喷注器