Reaction Jets Research Articles

Numerical Analysis of Postcombustion Effects on the Supersonic Jet Behavior

During the top blowing process of the basic oxygen furnace, the oxygen jet may react with CO before it reaches the surface of the molten bath. This combustion reaction affects the dynamic characteristics of the jet, which, in turn, affects its interaction with the bath. In this study, a numerical model is developed to investigate the transient and steady combustion characteristics of the supersonic jet emitted from the top lance. The transient combustion simulation shows that the CO ratio gradually decreases while the CO2 mole fraction increases at the interaction boundary region between jet and ambient due to the chemical reactions. In addition, the jet profile is changed when the postcombustion is introduced. Due to the flame formation and turbulence change at the jet combustion interface, the axial velocity at height of 2 m (x = 73 re) is 89% higher than that of the noncombustion reaction jet flow. In the results, it is demonstrated that the combustion interface is favorable to reduce the jet decay, resulting a higher dynamic pressure before the jet reaches the bath surface. Furthermore, a higher core temperature and lower density are obtained for the combustion jet compared to that of without combustion reaction.

Fault Tolerant Control of Drone Interceptors Using Command Filtered Backstepping and Fault Weighting Dynamic Control Allocation

This paper proposes a fault tolerant control strategy for drone interceptors with fixed wings and reaction jets subject to actuator faults. The drone interceptors have both continuous and discrete actuators, which pose a challenge to the control system design. The proposed fault tolerant control system consists of two parts, a nonlinear virtual control law and a dynamic control allocator. To deal with system uncertainty and quantization error, a virtual control law with a parameter update law is designed by command filtered backstepping. Then, a fault weighting dynamic control allocation algorithm is developed to distribute the virtual control signal to the actuators on the drone interceptor. When an actuator fault occurs, the proposed fault weighting dynamic control allocation scheme can redistribute the control signals to the remaining actuators. The effectiveness of the proposed algorithm is confirmed by numerical simulation.

Aerodynamic characteristics of co-flow jet wing with simple high-lift devices

Numerical investigations are conducted to explore the aerodynamic characteristics of three-dimensional Co-Flow Jet (CFJ) wing with simple high-lift devices during low-speed takeoff and landing. Effects of three crucial parameters of CFJ wing, i.e., angle of attack, jet momentum and swept angle, are comprehensively examined. Additionally, the aerodynamic characteristics of two CFJ configurations, i.e., using open and discrete slots for injection, are compared. The results show that applying CFJ technique to a wing with simple high-lift device is able to generate more lift, reduce drag and enlarge stall margin with lower energy expenditure due to the super-circulation effect. Increasing the jet intensity can reduce the drag significantly, which is mainly contributed by the reaction jet force. The Oswald efficiency factor is, in some circumstances, larger than one, which indicates the potential of CFJ in reducing induced drag. Compared with clean wing configuration, using CFJ technique allows the aerodynamic force variation less sensitive to the swept angle, and such phenomenon is better observed for small swept angle region. Eventually, it is interesting to know that the discrete slotted CFJ configuration demonstrates a promising enhancement in aerodynamic performance in terms of high lift, low drag and efficiency.

Study on sodium-water reaction jet evaluation model based on engineering approaches with particle method

Study on sodium-water reaction jet evaluation model based on engineering approaches with particle method

Prescribed performance-based adaptive sliding mode control for the autopilot design of missile with lateral jets

A novel prescribed performance-based adaptive sliding mode control is investigated for the autopilot design of missile with lateral reaction jets. An integral sliding mode surface is designed for a class of nonlinear systems such that the prescribed output-tracking behavior is incorporated into the sliding mode dynamics. An adaptive algorithm is developed using the concept of equivalent control to attenuate the chattering effect. Then, the method is applied to the autopilot design where the sliding mode control law is allocated to two sets of actuators according to their respective characteristics. The proposed integral sliding surface guarantees that the missile output can track the given reference command with the prescribed performance indices from the very beginning of the time. Moreover, the adaptation laws allow the reduction of the jets consumption. Several simulations conducted at different set-points show the efficacy of the proposed methods.

Analytical Investigation of Propellant Slosh Stability Boundary on a Space Vehicle

The effect of propellant sloshing upon the stability of a liquid-propelled space vehicle in a high-g environment has been studied extensively. For a typical space vehicle with thrust vector control and a single slosh tank, the Bauer slosh danger zone is located between the vehicle center of mass and the center of percussion while ignoring effects, like aerodynamics and axial acceleration. If the slosh mass is located between these two locations, baffles may be required to provide additional damping for stability. Although this criterion is widely used in the launch-vehicle flight control community, its application is limited to the aforementioned configuration and assumptions. In this work, the methodology behind the classic single-tank criteria is extended to other tank configurations and includes previously ignored effects. First, a vehicle with a single centerline tank and a pair of outboard reaction jets, rather than thrust vectoring, for attitude control is studied. Second, the impacts of aerodynamics and vehicle axial acceleration on the classic single-tank criteria are analyzed. Finally, the variation of the classic danger zone for a tandem tank configuration, where the tanks are located along the vehicle centerline or symmetrically offset from the centerline, is investigated.

A simple method for drag estimation for wedge-like fairings in hypersonic flow

ABSTRACTThe addition of wedge-like fairings onto the side of missiles and space launch vehicles, to shield devices such as cameras and reaction jet nozzles, creates additional drag, particularly when in supersonic and hypersonic freestream flow. An experimental and computational study was performed to obtain aerodynamic data on simple representative configurations to test the accuracy of simple theories for the drag increment due to these types of fairings. A semi-empirical method to estimate drag on wedge-shaped projections is presented, which may be used by missile designers to provide predictions of the drag increment due to wedge-like fairings. The method is shown to be valid where the wedge width is much smaller than body diameter, and across the Mach number range 4–8.2 but is likely to be valid for higher Mach numbers. Drag coefficient is found to increase with increasing wedge angle and reducing wedge slenderness, although increasing slenderness tends to increase skin friction drag.

Ignition of nanothermites by a laser diode pulse

Experimental investigation has been carried out for laser ignition and combustion of nanothermites based on aluminum and oxides of copper, bismuth and molybdenum. Ultrasonic mixing of nanosized powders was used to produce compositions. For thermite ignition, initiating laser pulse with a maximum intensity of 770 W/cm2 was generated by a laser diode with a wavelength of 808 nm. The ignition delay times, the minimum initiation energy density, and the average burning rate at various thermite densities and mass fractions of components were determined by recording the emission of radiation of the reaction products using a multichannel pyrometer jointly with a high-speed video camera. The effect of adding carbon black on the threshold parameters of a laser pulse was also studied. Based on the obtained results, certain assumptions were put forward with regard to the mechanism of nanothermites’ ignition by laser radiation and their burning. In particular, the assumptions were made on the two-stage process of the reaction initiation and jet burning mechanism of porous nanothermites.

Compound control method for Anti-Unmanned Aerial Vehicle (UAV) vertical launch missile

A compound control method with aerodynamic canard and reaction jet is proposed for anti-Unmanned Aerial Vehicle (UAV) vertical launch missile. The purpose of this method is to solve the problem of vertical launch with high angle of attack and low dynamic pressure. This paper first introduces the actuator layout and ignition strategy of reaction jet. Then the model of compound control system is established and compared with aerodynamic control in detail. Simulation studies demonstrate the effectiveness of the proposed method.

Study on Sodium-water Reaction Jet Evaluation Model Based on Engineering Approaches with Particle Method

Study on Sodium-water Reaction Jet Evaluation Model Based on Engineering Approaches with Particle Method

Initiation of shaped charge into booster devices

ABSTRACT In this paper, the initiation capacity of shaped charges against booster devices is carefully examined using both experimental and simulation method. A booster device, which consists of insensitive charges, is investigated by shaped charge jet impact test. The results show that the response degree of the booster device with insensitive charge is detonation reaction. The numerical simulation results of jet initiation into booster devices are also compared with the witness board deformation performance. Furthermore, based on the validated numerical models and the corresponding parameters, a series of numerical simulations are performed to investigate the influence of the explosive types of booster devices, the locations of booster devices and the shell materials of booster devices. By assessing the peak pressure, maximum reaction degree and jet velocity, the influences of the key parameters on the booster device initiation are numerically discussed. The results indicate that, compared with traditional charge, the insensitive charge booster device has low jet initiation insensitivity. As the location of booster device changes, the anti-initiation performance of booster device changes. At the angle of 45°, the minimal initiation performance of the booster device is obtained. It is found that the density and strength of shell material have a slight effect on the jet initiation performance under the given thickness booster device. However, variations in the shell material property are found to impart significant effect on the jet penetration velocity, while variations in the strength impart a significant influence on the low-speed jet.

Optimal control and stabilization of building maintenance units based on minimum principle

In this paper we present a mathematical model describing the physical dynamics of a building maintenance unit (BMU) equipped with reaction jets. The momentum provided by reaction jets is considered as the control variable. We introduce an objective functional based on the deviation of the BMU from its equilibrium state due to external high-wind forces. Pontryagin minimum principle is then used to determine the optimal control policy so as to minimize possible deviation from the rest state thereby increasing the stability of the BMU and reducing the risk to the workers as well as the public. We present a series of numerical results corresponding to three different scenarios for the formulated optimal control problem. These results show that, under high-wind conditions the BMU can be stabilized and brought to its equilibrium state with appropriate controls in a short period of time. Therefore, it is believed that the dynamic model presented here would be potentially useful for stabilizing building maintenance units thereby reducing the risk to the workers and the general public.

Research on component synthesis active vibration suppression method for flexible spacecraft attitude maneuver with reaction jet actuators

Purpose The purpose of this paper is to design a component synthesis method to suppress the vibration of the flexible spacecraft, which has the constant amplitude force/moment actuator. Design/methodology/approach The authors proposed a method to construct constant amplitude of time delay and composite coefficient sequences based on the principles of the component synthesis vibration suppression (CSVS). The associated design strategy of the CSVS torque control is also developed. The dynamic model consisting of a single axis rotating rigid central body and a fixed flexibility panel is used to validate the proposed method. Constraint modal and free modal method are both tested to analyse the natural frequencies of the panel and dynamic properties of rigid–flexible decoupling system, under the conditions of known and unknown frequencies. The feasibility of constructing CSVS control force based on the constraint modal frequency is also analysed. Findings The proposed method can suppress multistage vibration and has arbitrary order robustness for each order frequencies simultaneously. Simulation results show that only the duration time of the actuator has to be set for the proposed method, reasonable vibration suppression effect can be achieved. Practical implications The method can be used in spacecraft, especially flexible spacecraft to suppress the vibration; the approach is convenient for engineering application and can be easily designed. Originality/value The authors proposed a method to construct constant amplitude of time delay and composite coefficient sequences based on the principles of the CSVS.

Adaptive control of underactuated flight vehicles with moving mass

The configuration of internal moving masses is a key challenge for applying moving mass control technology to flight vehicle control. A novel configuration with a large mass ratio moving mass and reaction jets is proposed for bank-to-turn control. The control system of the proposed configuration consists of the attitude dynamics and the moving mass dynamics, which are coupled by the additional inertia moment of moving mass. To deal with the coupling, the integrated control of an attitude-servo system and a lateral underactuated control based on immersion and invariance theory is presented. To overcome the uncertainties in the flight vehicle model, immersion and invariance theory is employed to design an estimator for the unknown aerodynamic parameters. The estimator has an additional nonlinear term which adjusts the performance of the estimation error. The simulation results show that the proposed attitude-servo controller for the longitudinal subsystem can enhance the response of the system and the underactuated controller of the lateral subsystem can reduce fuel consumption.

Nonlinear Model Predictive Control for Near-Space Interceptor Based on Finite Time Disturbance Observer

This paper proposes a novel nonlinear model predictive control design method based on the finite time disturbance observer (FTDO) and dynamic control allocation (DCA) algorithm for the near-space interceptor (NSI). First, the FTDO is introduced to estimate the mismatched system disturbance. The nonlinear model predictive control scheme based on the estimation value is proposed to obtain the virtual control command, and the mismatched disturbance can be effectively removed from the output channels of the NSI by designing a feed-forward disturbance compensation term with an appropriate compensation gain matrix. Moreover, a new DCA method is given to distribute the above virtual control command among the corresponding actuators (reaction jets and aerodynamic fins). Finally, numerical simulations illustrate that the proposed control scheme can track the command signal with high precision and have strong robustness against the mismatched disturbance.

Method for improving the bank‐to‐turn missile manoeuvrability

This study addresses the autopilot design problem for a bank-to-turn missile to improve the manoeuvrability. A modified dynamic model is introduced by adding new reaction jet inputs to provide extra manouvrability. The H_ index, which is defined as the minimum singular value of the transfer function, is utilised to assess the manoeuvrability and the autopilot design problem is then transformed to a problem of H_ index controller design. An iterative linear matrix inequality algorithm is presented to obtain the control law. Simulation results illustrate the effectiveness of the proposed approach.

Dynamic analysis and control of novel moving mass flight vehicle

In terms of the moving mass control technology, the configuration of internal moving masses is a key challenge. In order to reduce the complexity of configuring these moving masses in a flight vehicle, a combination bank-to-turn control mode with the single moving mass and reaction jet is proposed in this paper. To investigate the dynamics and the potential of the control mechanism, an attitude dynamic model with single moving mass is generated. The dynamic analysis indicates that the control stability, control authority and dynamic behavior of the pitch channel are determined by the mass ratio of the moving mass to the system and the difference between the mass center of the moving mass and the mass center of the vehicle body. Interestingly, control authority increases proportionally with increasing mass ratio and also with decreasing the magnitude of the static margin. To deal with the coupling caused by the additional inertia moment which is generated by the motion of the moving mass, an adaptive control law by using dynamic inversion theory and the extended state observer is designed. Also, a compensator is designed for eliminating the influence of the servo actuator's dynamics on attitude of the flight vehicle. Finally, the simulation results validate the quality of the proposed adaptive controller which ensures a good performance in the novel configuration with internal moving mass.

Attitude control of reentry vehicle with a pitch-control single moving mass

Since the point moving mass configuration cannot be implemented in engineering applications, a novel configuration of moving mass with large mass ratio and reaction jet is proposed. This configuration has a great advantage in engineering application as well as improving the vehicle’s maneuverability. According to the dynamic analysis, the moving mass with large mass ratio leads to the coupling between the attitude and the deflection angle of moving mass and the dynamic behavior of flight vehicle can be affected by the momentum exchange. Therefore, the moving mass cannot be regarded as a point mass. A disturbance observer is investigated for this strong coupling nonlinear system, which estimates the total disturbance which contains the nonlinear couples and un-modeled disturbances. Then, a control law based on feedback linearization is used for compensation. The simulation results show that the proposed configuration is feasible and validate the quality of the adaptive controller which ensures a good performance.

Robust adaptive sliding sector control and control allocation of a missile with aerodynamic control surfaces and reaction jets

Based on L2 optimal control allocation, an autopilot design approach is proposed for the missile with aerodynamic control surfaces and reaction jets. The control system involves a control allocator and a virtual control law. A robust sliding sector with a parameter update law is proposed to deal with unmatched parameter uncertainties and unknown disturbances in the system. Then a control law is designed to produce virtual control effort signals by using the robust adaptive sliding sector. In order to distribute the virtual signals to the aerodynamic control surfaces and reaction jets on the missile, a control allocator is designed by L2 optimal control allocation strategy. Simulation results show that the missile control system tracks the acceleration command fast and smoothly. In the tracking process, aerodynamic control surfaces cooperate with reaction jets, verifying the effectiveness of the proposed approach.

Multi-model soft switching tracking control for near-space interceptor based on the disturbance observer

A disturbance observer–based multi-model soft switching tracking control design is proposed for the near-space interceptor. Initially, based on the Takagi–Sugeno modeling approach, a slow–fast loop soft switching model is employed to approximately describe the nonlinear dynamics of the near-space interceptor. Subsequently, a disturbance observer is constructed to estimate the unknown disturbance. Based on the disturbance observer, a descriptor system approach is proposed to solve the multi-model soft switching tracking control design problem. The suggested controller can not only ensure the stability of the closed-loop near-space interceptor system but also provide an upper bound of the cost function. Moreover, a robust least-squares weighted control allocation algorithm is employed to distribute the virtual control command among the redundant actuators (the aerodynamic fins and reaction jets). Finally, simulation results demonstrate the effectiveness of the proposed control scheme.