Structure Design And Analysis Of High Temperature Dynamic Seal

During hypersonic vehicle reentry phase, high pressure hot gas would flow into low pressure gap between control surfaces. If no measure had been taken to heating gap, hot gas ingestion would overheat low-temperature structure and possibly lead to loss of vehicle. Thus control surface dynamic seal structure was important to improve safety and reliability of hypersonic vehicle. During 420s peak heating period, the maximum temperature of X-38 control surface gap exceeded 1000℃. If no thermal protective measures had been taken to hot gap, calculated heat flow at 12.7cm below gap surface reached up to 110Kw. The designed seal must stand severe aerodynamic heating environment and adapt to large changes of gap. The dynamic seal composing of spring, insulation and fiber braided sleeve had good high temperature seal properties, and had a good prospect in control surface seal.Spring was seal structure skeleton, so the mechanical properties of seal structure mainly depended on spring. Spring structure had good resiliency to ensure seal structure always contact with sealing surface. Two kinds of springs had been analyzed. The force versus displacement relationship for each spring had been studied. The influence of canted amplitude, wire diameter and number of coils per unit length on mechanical properties of canted spring had been obtained. The influence of braided parameters on mechanical properties of braided spring had also been studied, and finally the optimization parameters had been given to guide seal structure design.Considering the hot gas flow through the seal structure effects, when heat transfer coefficient was greater than 103 W·m-2·K^-1, the temperature of gas and solid was similar, and 18mm diameter optimal designed seal structure cannot meet the requirements; considering double seal structure, the critical value of gas flow rate 10-3 kg·m^-1·s^-1 had been given. The back wall temperature of seal was 660℃-700℃lower than heat surface of seal in 420s transient heat transfer.Based on the structure design of dynamic seal, dynamic seal samples had been manufactured. Considering environment of dynamic seal, set up ground simulation platform to access dynamic seal performance. Test time was set to 420s,300s and 180s, surface heat flux was 110kw, rudder rotation frequency was 30/min, Maximum deflection angle was 24°, with the seal, the temperature below the seal was 600℃-700℃lower than the heat surface. During experiment process. The back wall temperature of seal rose up slowly, and temperature fluctuations had not occurred, so this structure met high temperature seal requirements.