Search

The fluidic-throat nozzles will encounter a new problem when they are applied to solid rocket motors. In order to improve the specific impulse of solid rocket motors, metal powders are often added to the propellant; the particle phase in the gas flow will cause the disturbance on the fluidic throat and change nozzle performance. Therefore, it is necessary to reveal the influence of the gas–particle two-phase flow on the performance of a fluidic-throat nozzle in the design. The disturbance of the particle phase on the primary flow and the secondary flow is divided into two aspects. On the one hand, due to the inertia of the particle phase, there is a speed difference between the gas phase and the particle phase. Generally, the particle phase lags behind the gas phase, so the particle phase will drag the gas phase. On the other hand, there is also a temperature difference between the particle phase and the gas phase, and the temperature of the particle phase is higher than that of the gas phase, so there is heat exchange between the two phases.

This chapter mainly discusses the flow details and characterization performance of gas–gas fluidic throat, including the effective throat area of fluidic throat, the analytical methods for steady aerodynamic characteristics, flow characteristics of fluidic, relationship between secondary flow rate ratio and total pressure ratio, relationship between secondary flow parameters and effective throat area, effect of the main nozzle parameters, and comparison of secondary flow injection schemes in the fluidic throat.

This chapter mainly discusses the injector arrangement concepts with the combined secondary flow vector control, including work modes and TVC manners. The following issues are also discussed and introduced: performance characterization of TVC, six-component forces tests of secondary flow TVC, injector positions and TVC characters, influences of fluidic-throat jet on TVC, and arrangement concepts of round-hole injectors.

For a thrust-adjustable rocket motor, to avoid unstable combustion, we not only need to consider nozzle damping before thrust adjustment, but also need to consider nozzle damping variation thereafter, and it is important to learn about the influence of nozzle damping before, and after, thrust adjustment. This chapter discusses wave attenuation method for predicting nozzle damping of the fluidic nozzle, validation of numerical prediction method for nozzle damping, and gives the nozzle damping variation with different secondary flow parameters.

This chapter discusses the time-dependent thrust modulation process of the fluidic throat for engineering applications. It is necessary to learn the thrust modulation of the fluidic throat and the unsteady process of the mainstream flux. It is directly related to the thrust modulation characteristic of the fluidic-throat nozzle and its proper operating mode. Typical internal ballistic results under different operating conditions are introduced in the following sections, including calculation method of internal ballistics, modulation process at fixed mass flow rates, unsteady process for the axial-gap fluidic throat, and thrust modulation for the hole-type fluidic throat in hot test conditions.

In the engine, if the secondary flow is a liquid that can react with the fuel gas, the gas–liquid fluidic throat in the nozzle can be roughly divided into four regions: an extrusion zone of secondary flow, a gasification zone, a chemical reaction zone, and a mainstream area. The liquid phase state injected through the secondary flow injector, such as a liquid belt or droplet, directly affects the extrusion of the gas–liquid fluidic throat and the size of the gasification zone. If the liquid secondary flow is well atomized at the nozzle to form fine droplets, in addition to its own volume extrusion, the interaction of the droplets with the mainstream flow will increase, increasing the flow resistance of the mainstream flow. In addition, the surface area of the liquid secondary flow increases after the formation of the droplets, the evaporation enhances, and the gasification zone enlarges. The mixing rate of the gas phase in the reaction zone and the reaction rate are also dependent on the atomization and evaporation of the secondary flow at the nozzle. The effect of different injectors on the atomization characteristics under conditions with different ratios of secondary flow rate to mainstream flow rate in different secondary flow injection modes is introduced in this chapter.

The nozzle-throat insert of an engine is the most important part of the nozzle. In high-performance engines, the nozzle-throat insert cannot only resist high-speed and high-temperature (up to 3,000 K) gas with metal particles, but also produce extremely high-temperature gradient and thermal stress. In order to ensure pressure of the combustion chamber to guarantee the performance of engines, it is necessary to strictly control the ablation of the nozzle-throat insert. This chapter discusses the throat erosion of the fluidic-throat nozzle, and proposes an active thermal protection technology and the throat lining surface compensation technology based on the fluidic throat.

The characterization function and thrust efficiency are discussed in this chapter. A linear characterization function is applied. It is convenient to learn the parameters which affect the throttling capability obviously, by comparing the fitting slope of characteristic function curves from combining the results of hot firing tests, cold-flow tests, and simulations. Besides, the linear form of the characteristic function curve is convenient for engineering application and reference, which results in less experiments and simulations than before. The relationship between secondary flow parameters and thrust efficiency is also discussed.