火箭发动机涡轮泵轴电解扩孔加工技术

Electrochemical machining of rocket engine turbopump shaft

某型液体火箭发动机涡轮泵轴内腔采用台阶式深长孔结构,需将长度424 mm的深孔直径由φ71.8 mm扩孔至φ89 mm,采用常规机械加工,存在刀具易振颤、散热条件差等难题,加工难度极大,成本高昂。提出一种工件旋转、阴极可调整式随动进给电解加工方法解决大深径比深孔扩孔难题,借助流场电场仿真技术手段,完成了内喷式工具阴极刃的刃口优化设计、长阴极刃的电解液喷口结构设计与优化、过渡圆弧的阴极轮廓设计与优化;并完成了加工装置的适应性改制,进行了电解扩孔技术的电解加工参数优选。在电解液浓度20%(硝酸钠溶液)、电解液温度29~33℃、电解液入口压力0.3 MPa、电压20 V、阴极进给速度0.02 mm/min、电机转速8 r/min的加工条件下,借助超声波测厚仪在机检测剩余壁厚,对阴极进行动态调整,加工出圆度及同轴度优于φ0.02 mm、直径精度优于0.2 mm的轴深孔结构。

A liquid rocket engine turbopump shaft cavity adopts stepped deep hole structure, the diameter of deep hole with length of 424 mm was needed to be enlarged from φ71.8 mm to φ89 mm. Using conventional machining, there are problems such as easy to shake the tool, poor heat dissipation conditions, processing extremely difficult, high cost etc. A workpiece rotation, the cathode adjustable type servo feed electrochemical machining methods was proposed to solve deep hole reaming problem with large depth to diameter ratio, with the aid of flow field simulation technology. Which was completed within the edge of the tool cathode blade optimization design, long blade cathode electrolyte nozzle structural design and optimization, transition arc cathode contour design and optimization, the adaptability of restructuring and finished the processing device. Electrolytic reaming technology of electrolytic machining parameters optimization was present in the electrolyte concentration of 20%(sodium nitrate solution), electrolyte temperature 29-33 ℃, electrolyte inlet pressure 0.3 MPa, voltage 20 V, cathode feeding speed 0.02 mm/min, motor speed 8 r/min processing conditions, with the ultrasonic thickness measuring instrument in the machine to detect the remaining wall thickness. The cathode was dynamically adjusted to produce a shaft deep hole structure with roundness and coaxiality better than φ0.02 mm and diameter accuracy better than 0.2 mm.