Research On Combined Nozzle Flow Regulation And Thrust Vector Technology For Ducted Rocket Motor

An innovative conceptual combined nozzle and its two innovative technologies, combined nozzle flow regulation and thrust vector, applicable to solid fuel integral ducted-rocket are presented to solve current ducted-rockets' deficiencies in high speed cruise performance and maneuverability. Within entire missile speed range, these technologies not only improve thrust performance by regulating nozzle flow, but also realize missile direct thrust control through constructing vectored thrust. Unlike conventional fixed geometry nozzle that can not be regulated, this work made a breakthrough by establishing a combined nozzle flow regulation technology, which not only has great scientific significance by enriching ducted-rocket design theory, but also has great value in engineering applications.Systematic researches on combined nozzle and its flow regulation, as well as thrust vector technologies are carried out in this dissertation. First, by analyzing and summarizing current status of solid fuel integral ducted rocket technology in detail, the problem that unable to regulate nozzle causes severe degradation in ducted rocket high speed cruise performance is identified, and its flow mechanisms are clarified and its causes are traced back to design philosophy and technical approaches. Therefore, technical roadmap of current study, which emphasizes on improving high speed cruise performance, uses high speed cruise and high maneuverability tactic, and adopts simple cruciform axisymmetric configuration to reduce difficulties in flight control design, is established. To fully utilize structural space within inlet cowl, conformal structural design of combined nozzle and missile aerodynamic configuration is also carried out.Based on the working principles of solid fuel ducted rocket and gas dynamics theory, as well as appropriate engineering experiences and approximations, the computation method and analytical model of combined nozzle flow regulation and thrust vector design are established. And design case study is also performed using these models. The mechanisms that conventional fixed geometry nozzle limits ducted rocket performance are demonstrated quantitatively. And the solution, detailed combined nozzle concept, is proposed and discussed. The performance advantages of combined nozzle and its flow regulation are analyzed and evaluated quantitatively also. In addition, easy to implement nozzle regulation strategies and thrust vector construction methods are also explored.Finally, advanced CFD numerical simulations are carried out in design validations, revealing the physic natures of combined nozzle flow and its regulation, proving the correctness of current design idea and technology approach, and correcting minor deficiencies of design theory and computational models. Based on numerical simulations, detailed flow behaviors inside combined nozzle are depicted, and the phenomenon of flow loss caused by combined nozzle and secondary combustion chamber branching is also revealed, providing guides for further optimization.In particular, from simulation results, an important conclusion can be drawn:Only the simplest two stage control strategy, i.e., auxiliary nozzles are fully opened below design speed, and are fully closed above design speed, is required for the combined nozzle concept to significantly improve thrust performance of solid fuel integral ducted rocket. Compared to conventional design, the proposed design improves thrust by 18.51% at Ma 2 relay point, and by 26.57% at Ma 2.8 design point. At Ma 3.5 high speed cruise, the thrust is improved by as high as 27.95%, and thrust coefficient is increased from 0.5612 to 0.7438. It clearly shows the loss caused by unregulatable nozzle. However, this loss can be avoided by the proposed concept, so that the ducted rocket has good performance in both high speed cruise and low speed relay.In conclusion, the principle design studies and technical validations of combined nozzle and its flow regulation, as well as thrust vector technologies are completed successfully. The concept is not only feasible theoretically, but also easy to implement, having great prospects in engineering application.