Fluidic Thrust Vectoring Research Articles

Data-Driven Control-Oriented Modeling for Response of Fluidic Thrust Vectoring

Response to control input is of significance to the application of real-time active flow control (AFC). In this paper, a novel data-driven framework is used to discover the underlying physics of the dynamic response process of fluidic thrust vectoring (FTV), a typical application of AFC. In the proposed framework, sparse identification of a nonlinear dynamics (SINDy) algorithm is used to identify the governing equations of the flow control responses of sets of noisy measurement data. The clustering algorithm is then used to seek the generalized coefficients of basis functions for different sets of data, which improve the robustness of the model to noisy measurement data. First, a simulated mechanical system is used to validate the effect of the framework. To simplify the modeling, control performance and characteristics are investigated in a detailed manner. Then a dimensionless parameter ΔCp based on the pressure coefficient is found to exhibit a linear relationship with the vector angle under different working conditions. This parameter is introduced in the proposed framework to model the dynamic process of response to control input. The obtained governing equations can describe the dynamic process accurately based on the validation of testing data. The form of the governing equation is rewritten and analyzed based on the control theory, revealing the physics of this process, which is significant to practical AFC implementation.

Effect of self-excited oscillation of three-dimensional rectangular shock-induced thrust vector nozzle jet

The fluidic thrust vector nozzles including the shock-induced thrust vector nozzles stand out from traditional mechanical thrust vector nozzles used in aeronautics and astronautics due to their simplicity and potential for higher efficiency. However, a significant challenge in the transition from theoretical studies to practical applications is the phenomenon of self-excited oscillation of the nozzle jet, particularly in ramjet and scramjet engines. This oscillation can notably impact the jet control stability, which is critical for the operational reliability, accuracy, and safety of these engines. To investigate the effects of self-excited oscillation of the jet in the three-dimensional rectangular shock-induced thrust vector nozzles, a large eddy simulation approach has been utilized to examine various nozzle pressure ratios and secondary pressure ratios. The simulation data are in good agreement with the experimental data of National Aeronautics and Space Administration Langley Research Center, lending credibility to the simulation results. The research sheds light on the formation and evolution of self-excited oscillation. It does so by examining the interactions between shock waves and boundary layers, as well as bubble dynamics, offering a comprehensive view of the oscillation mechanism in a three-dimensional context. The results demonstrate that the self-excited oscillation of jet mainly belongs to low-frequency oscillation. With the increase in nozzle pressure ratio, the self-excited oscillation of the jet is suppressed because the shock system is pushed out of the shock-induced thrust vector nozzle exit. The variation of secondary pressure ratio only affects the amplitude of jet self-excited oscillation and does not transform the motion pattern.

Numerical investigation of dynamic characteristics of dual throat nozzle and bypass dual throat nozzle in thrust vectoring starting process

The Bypass Dual Throat Nozzle (BDTN) is a novel fluidic Thrust Vectoring (TV) nozzle, it switches to TV state by opening the valve in the bypass. To greatly manipulate the BDTN, the dynamic characteristics in the TV starting process should be analyzed. This paper conducts numerical simulations to grasp the variation processes of performances and the flow field evolution of BDTN and Dual Throat Nozzle (DTN). The dynamic responses of TV starting in typical DTN models are investigated at first. Then, the TV starting processes of BDTN in different Nozzle Pressure Ratio (NPR) conditions are simulated, and the valve opening durations (T) are also considered. Before the expected TV direction is achieved in the DTN, the jet is deflected to the opposite direction at the beginning of the dynamic process, which is called the reverse TV phenomenon. However, this phenomenon disappears in the BDTN. The larger injection width of DTN intensifies unsteady oscillations, and the reverse TV phenomenon is strengthened. In the BDTN, T determines the delay degree of performance variations compared to the static results, which is called hysteresis effect. At NPR = 10, the hysteresis affects the final stable performance of BDTN. This study analyses the dynamic characteristics in DTN and BDTN, laying a foundation for further design of nozzles and control strategies.

Research on fluidic thrust vector technology based on passive secondary flow with dual inclined walls under low subsonic speed

The application of fluidic thrust vector technology enables active flow control to deflect the jet. At present, hysteresis and abrupt jump phenomena have been found in the control law of fluidic thrust vector technology based on the Coanda effect. To weaken the abrupt jump and eliminate hysteresis phenomena, a new fluidic thrust vectoring nozzle based on passive secondary flow with dual inclined walls (PSDW) was developed. In this paper, the flow thrust vectoring characteristics of the the new fluidic thrust vectoring nozzle were studied by experimental method. By using PSDW, the flow vectoring angle could reach up to 29° and the thrust vectoring angle could be controlled continuously from 0° to 25°. The linearity of vectoring control over the first and the second inclined wall were 65% and 79%, respectively. There were no obvious hysteresis phenomena in the control process. The abrupt jump and hysteresis phenomenon could be eliminated in the thrust vector control law by PSDW, which provides a practical control method for jet deflection.

Determination of Optimum Parameter Space of a Fluidic Thrust Vectoring System based on Coanda Effect Using Gradient-Based Optimization Technique

In the realm of aviation, jet propulsion systems serve to provide enhanced maneuverability and to make sure that the aircraft thrust is accurately and precisely regulated during take-off and landing operations. The movement of aerodynamic control surfaces (flaps, slats, elevators, ailerons, spoilers, wing attachments) determines the mobility of practically all aircraft types. Recognized as dependable components in the aviation world for take-off and landing tasks, these control surfaces are being replaced by fluidic thrust vectoring (FTV) systems, especially in small unmanned aerial vehicles (UAVs) and short or vertical take-off and landing aircraft. The FTV system is capable of directing thrust in any preferred direction without the need for any movable components. This paper numerically examines the FTV system by utilizing computational fluid dynamics (CFD) and an optimization technique based on gradients of the system components to understand the physics of the Coanda effect in FTV systems. This research employs gradient-based optimization for nozzle design in order to optimize the parameter space for different velocity ratios (VR) by calculating the moment around the upper Coanda surface, which is used to represent the jet deflection angle. In that context, four different Coanda surface-pintle pair designs for four different VRs are produced. The parameter space shows significant improvement in all four configurations, and results reveal that all output parameters successfully delay separation on the thrust vectoring system's upper Coanda surface. Finally, four optimum design suggestions are tested at various VRs, and the most efficient and proper design is recommended based on output parameters.

Numerical investigation of a Coandă-based fluidic thrust vectoring system for subsonic nozzles

The numerical investigation of a novel subsonic thrust concept for fluidic thrust vectoring (FTV) of jet engines is the subject of this publication. FTV possibly offers advantages over conventional mechanical thrust vector control such as decreased complexity, mass and maintenance costs. The operating principle of the FTV nozzles under investigation at the Institute of Jet Propulsion is based on the Coandă effect. The applied concept of thrust vectoring uses dedicated secondary flow channels which are mounted in parallel around the nozzle inner cone or the nozzle wall. If required, bleed air, provided by extraction from the engine compressor or from an external source, is injected at a specific nozzle pressure ratio at the nozzle throat A_8 through these secondary ducts, resulting in the redirection of the secondary jet towards the convex Coandă surface. The interaction between the primary mass flow and the secondary jet leads to a redirection of the primary exhaust mass flow of the engine and thus to a vectoring of the exhaust flow. In this paper, the influence of different nozzle geometric parameters and different operating points are investigated within an extensive parametric study applied to a convergent two-dimensional thrust vectoring nozzle using computational fluid dynamics tools. Thrust vector deflection of up to {20}^{circ } at a maximum secondary to primary mass flow ratio of 10 % is achieved. Reducing this mass flow rate to 5 % still yields vectoring angles of up to {15}^{circ } whereby similar deflection angles compared to conventional mechanical thrust vectoring systems are achievable.

Techniques of Fluidic Thrust Vectoring in Jet Engine Nozzles: A Review

Thrust vectoring innovations are demonstrated ideas that improve the projection of aerospace power with enhanced maneuverability, control effectiveness, survivability, performance, and stealth. Thrust vector control systems following a variety of concepts have been considered for modern aircraft and missiles to enhance their military performance. Short Take-off and Landing (STOL) and control effectiveness at lower aircraft speeds can be achieved by employing Fluidic Thrust Vectoring Control (FTVC). This paper summarizes a range of ideas for FTVC that have been designed and tested both computationally and experimentally to determine the thrust vectoring performance of supersonic propulsion system nozzles. The conventional method of thrust vectoring involves mechanical means to deflect the direction of flow of the exhaust gases, whereas the most recent method involves fluidic-based thrust vectoring techniques. Fluid-based thrust vectoring has the advantages of simplicity and low weight over mechanical-based thrust vectoring, which has complex geometry and adds extra weight to the aircraft. The fluidic vectoring control nozzles are divided into seven categories: shock vector, bypass shock vector, counterflow, co-flow, throat skewing, dual throat, and bypass dual throat nozzle control. This paper provides a summary of each fluidic thrust vectoring technique with its characteristics, design, classification, and different operational criteria developed to date and compares the intrinsic characteristics of each technique. Based on the present literature, it is concluded that among all the fluidic control techniques, the bypass dual-throat nozzle control can achieve better thrust vectoring performance with large vector angles and low thrust loss.

Mathematical Modelling and Fluidic Thrust Vectoring Control of a Delta Wing UAV

Pitch control of an unmanned aerial vehicle (UAV) using fluidic thrust vectoring (FTV) is a relatively novel technique requiring no moving control surfaces, such as elevators. In this paper, the authors’ previous work on the characterization of a static co-flow FTV rig is further validated using the free to pitch dynamic test bench. The deflection of a primary jet after injection of a high-velocity secondary jet was captured using the tuft flow visualization technique, along with the experimental recording of subsequent normal force impinged on the Coanda surface resulting in the pitching moment. The effect of primary and secondary flow velocities on exhaust jet deflection, as well as on the pitch angle of the aircraft, is examined. Aerodynamic gain as well as the inertia of a delta wing UAV test bench are computed through experiments and fed into the equation of motion (e.o.m). The e.o.m developed aided in the design of a model-based PID controller for pitch motion control using the multi-parameter root locus technique. The root locus tuned controller serves as a benchmark controller for performance evaluation of the genetic algorithm (GA) and particle swarm optimization (PSO) tuned controllers. Furthermore, the frequency domain metric of gain and phase margins were also employed to reach a robust control design. Experiments conducted in a simulation environment reveal that PSO-PID results in a better response of the UAV in comparison to the baseline pitch controller.

Fluidic Thrust Vector Control of Aerospace Vehicles: State-of-the-Art Review and Future Prospects

Abstract An efficient propulsion system holds the key to the smooth operation of any aerospace vehicle over different flight regimes. Apart from generating the necessary thrust, emphasis has also been laid on vectoring the direction of thrust. The primitive modes of thrust vectoring chiefly focused on mechanical means such as the use of gimbals or hinges. The current state-of-the-art technologies demand more efficient methods for thrust vectoring, which minimize the use of mechanical components. These methods termed fluidic thrust vector control methods, employ secondary jets for achieving the required attitude, and trajectory of the aerospace vehicles such as aircraft, rockets, and missiles. Such methods have greatly helped in reducing vehicle weight, vehicle maintenance requirements, and enhancement of stealth characteristics of such vehicles. This work presents a review of the various fluidic thrust vectoring systems, starting with a brief overview of traditional thrust vectoring systems, followed by a discussion on the various aspects of fluidic thrust vectoring systems. It also highlights the effect of the various geometrical and operating conditions on the performance parameters of the thrust vectoring system such as the thrust vector angle, system thrust ratio, and thrust vectoring efficiency among others. For ensuring the comprehensive character of this work, synthetic jet vectoring techniques have also been included due to their nonmechanical nature and similarities with purely fluidic thrust vectoring techniques.

Investigation of fluidic thrust vectoring for scramjets

Fluidic thrust vectoring (FTV) offers a novel approach to aerodynamic control, circumventing some of the issues associated with mechanical systems. One method is shock vector control which involves injecting a fluid into the exhaust nozzle of an engine to redirect the gases and thus, produce a control force. An experimental model which incorporated FTV was designed and tested at Mach 6 in the Oxford high density tunnel (HDT). The model was a simplified two-dimensional scramjet geometry with two different configurations to compare an internal and external exhaust nozzle. The FTV injection system consisted of a slot at the rear edge of the exhaust nozzle fed from an internal plenum. In the experimental campaign, a range of gas injection pressures and free stream stagnation pressures were tested to assess the effectiveness of both configurations. Two new measurement methods were successfully implemented in the HDT: pressure sensitive paint and a 6-axis load cell. The FTV system has been shown to be effective with observable increases in lift and pitching moment. A linear relation between the injection pressure ratio and the control forces could be observed for both configurations.Graphical abstract

Influence of Amplitude of Excited Secondary Flow on the Direction of Jets

In this research, a method for direction control of a primary jet with a Coanda surface is investigated as part of a fundamental study of fluidic thrust vectoring. The effect of the velocity amplitude ratio (i.e., ratio of time-averaged velocity to velocity fluctuation amplitude) of the secondary flow on the flow characteristics of the jet was experimentally investigated. It was determined that the jet deflection angle was maximized under the suction condition wherein the secondary flow exhibited velocity fluctuation. The relationship between the jet deflection angle and the momentum ratio between the primary jet and the secondary flow is presented, in which the dimensionless frequency of the secondary flow was used as a parameter. Although the jet deflection angle depended on the dimensionless frequency and the momentum ratio, it was difficult to adjust this parameter using only the momentum ratio in the hypothetical saturated region where this ratio is large. In addition, unsteady characteristics were also discussed for several conditions.

Fluidic Thrust, Propulsion, Vector Control of Supersonic Jets by Flow Entrainment and the Coanda Effect

Thrust, propulsion, vector control of supersonic jets has been applied to jet and rocket engines, ejectors, and other many devices. In general, there are two approaches to this type of control, namely mechanical moving systems and fluidic thrust vector control systems without moving parts, with mechanical moving systems being the most common. However, generally speaking, these systems are very complicated, and more simple methods and devices are desired. In this study, an extremely simple method for the thrust vector control of a supersonic jet by a fluidic Coanda nozzle (FC-nozzle) using the entrainment of the surrounding fluid and Coanda effect is newly proposed. The FC-nozzle consists of a pipe nozzle (Pi-nozzle), spacer, and linearly expanded Coanda nozzle (Co-nozzle) with eight suction pipes (Su-pipes) installed to surround the jet from the Pi-nozzle. The jet from the Pi-nozzle flows straight with the entrainment flow of the surrounding fluid. When some Su-pipes are closed, the pressure between the jet and Co-nozzle wall decreases, and subsequently, the jet deflects to the closed side of the Su-pipe and reattaches to the wall by the Coanda effect. The flow characteristics and deflection characteristics of the supersonic jet from the FC-nozzle are examined by the visualized flow pattern using the Schlieren method and measurements of the velocity distribution. As a result, it is shown that by changing the number of Su-pipes and the locations at which they are closed, the deflection angle and circumferential position of the jet from the Pi-nozzle can be easily controlled.

Dual Synthetic Jets Actuator and Its Applications—Part II: Novel Fluidic Thrust-Vectoring Method Based on Dual Synthetic Jets Actuator

A novel fluidic thrust-vectoring (FTV) control method based on dual synthetic jets actuator (DSJA) is proposed and evaluated. Numerical simulations are governed by the compressible Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations. According to the results, DSJA is capable of deflecting a primary jet with a velocity of 100 m/s and a height of 50 mm by approximately 18 degrees with a momentum coefficient of 1.96%. It produces comparatively linear control characteristics in almost all deflection angles evaluated (0~23 degrees). The low pressure generated by DSJA, the ejecting enhanced by DSJA, and the co-flow effect produced by the accelerated secondary jet all play roles in the deflection of the primary jet. Since the primary jet is strong enough, the potential of DSJA to provide thrust vector control is revealed.

Computational Investigation of Effects of Side-Injection Geometry on Thrust-Vectoring Performance in a Fuel-Injected Dual Throat Nozzle

Dual-throat Nozzle (DTN) is known as one of the most effective approaches of fluidic thrust-vectoring. It is gradually flourishing into a promising technology to implement supersonic and hypersonic thrust-vector control in aircrafts. The main objective of the present study is numerical investigation of the effects of secondary injection geometry on the performance of a fuel-injected planar dual throat thrust-vectoring nozzle. The main contributions of the study is to consider slot and circular geometries as injector cross-sections for injecting four different fuels; moreover, the impact of center-to-center distance of injection holes for circular injector is examined. Three-dimensional compressible reacting simulations have been conducted in order to resolve the flowfield in a dual throat nozzle with pressure ratio of 4.0. Favre-averaged momentum, energy and species equations are solved along with the standard k- ε model for the turbulence closure, and the eddy dissipation model (EDM) for the combustion modelling. Second-order upwind numerical scheme is employed to discretize and solve governing equations. Different assessment parameters such as discharge coefficient, thrust ratio, thrust-vector angle and thrust-vectoring efficiency are invoked to analyze the nozzle performance. Computationally predicted data are agreed well with experimental measurements of previous studies. Results reveal that a maximum vector angle of 17.1 degrees is achieved via slot injection of methane fuel at a secondary injection rate equal to 9% of primary flow rate. Slot injection is performing better in terms of discharge coefficient, thrust-vector angle and thrust-vectoring efficiency, whereas circular injection provides higher thrust ratio. At 2% secondary injection for methane fuel, vector angle and vectoring efficiency obtained by slot injector is 8% and 34% higher than the circular injector, respectively. Findings suggest that light fuels offer higher thrust ratio, vector angle and vectoring efficiency, while heavy fuels have better discharge coefficient. Increasing center-to-center distance of injector holes improves thrust ratio, while having a negative effect on discharge coefficient, vector angle and vectoring efficiency. A comparison between fuel injectant of current study and inert injectant in the previous studies indicates that fuel reaction could exhibit substantial positive effects on vectoring performance. Secondary-to-primary momentum flux ratio is found to play a crucial role in nozzle performance.

Performance of a turbojet engine with fluidic thrust vectoring

AbstractThe objective of the present work is to estimate the performance of a turbojet engine during Fluidic Thrust Vectoring (FTV) employed by injecting the secondary-jet at the throat of a convergent nozzle. The nozzle performance maps and effective nozzle throat area obtained from experiments are coupled with the performance of a conventional engine (without FTV) using an iterative algorithm developed as a part of this work. The performance is estimated for different flow rates of secondary-jet sourced either from a separate compressor or the engine’s compressor. During FTV, the operating point shifted towards the surge line with increased turbine entry temperature. The desired and obtained vector angles and thrust magnitudes are different. At high secondary-jet flow rates, the turbine operation moved out of its performance map. These aspects should be incorporated while integrating the FTV at the system level, thus, asserting the importance of FTV studies coupled with engine performance.

Influence of secondary flow with a Coanda surface on the direction of jets

Abstract We propose a method for fluidic thrust vectoring by studying the effect of excited secondary Coanda flow on the direction of jets. The primary flow is the steady continuous jet, while the the secondary flow is synthetic jet or continuous flow. In this experiment, speaker is used to adjusted the frequency and velocity amplitude of synthetic jets, while a blower is used to adjust the continuous jet and suction flow.We visualize and compare the primary flow under the influence of various secondary flows. Additionally, computational fluid dynamics is used to investigate the flow characteristics, including the deflection angle. The main results of this study is that both synthetic jets and continuous suction flow are capable of deflection.

Thrust Vectoring of a Fixed Axisymmetric Supersonic Nozzle Using the Shock-Vector Control Method

The application of the Shock Vector Control (SVC) approach to an axysimmetric supersonic nozzle is studied numerically. SVC is a Fluidic Thrust Vectoring (FTV) strategy that is applied to fixed nozzles in order to realize jet-vectoring effects normally obtained by deflecting movable nozzles. In the SVC method, a secondary air flow injection close to the nozzle exit generates an asymmetry in the wall pressure distribution and side-loads on the nozzle, which are also lateral components of the thrust vector. SVC forcing of the axisymmetric nozzle generates fully three-dimensional flows with very complex structures that interact with the external flow. In the present work, the experimental data on a nozzle designed and tested for a supersonic cruise aircraft are used for validating the numerical tool at different flight Mach numbers and nozzle pressure ratios. Then, an optimal position for the slot is sought and the fully 3D flow at flight Mach number M∞=0.9 is investigated numerically for different values of the SVC forcing.

Schlieren Visualization of Coflow Fluidic Thrust Vectoring Using Sweeping Jets

Reducing the consumption of secondary flow is of significance to future development of fluidic thrust vectoring (FTV) technology. A new coflow FTV control method based on sweeping jet (SWJ) excitation is proposed for the deflection of primary jets, and its performance is comparatively examined against conventional steady jet (SJ) excitation. Schlieren visualization using a high-speed camera is applied to provide insights into the flowfields. The results show that at the same mass flow rate of the secondary coflow injection and for Mach numbers of primary flow up to 0.35 SWJ excitation achieves a larger primary flow deflection angle than the SJ excitation does. To examine the flow control mechanisms, clear flow structures are extracted from noisy images by using robust principal component analysis. Moreover, dynamic mode decomposition is applied to investigate the flow dynamics of the primary flow. The SWJ is found to be more capable of enhancing the flow mixing than the SJ is. Furthermore, the SWJ ensures that the primary jet attaches to the nozzle surface and produces a larger deflection angle, which leads to the higher efficiency in coflow vectoring control.

A fluidic thrust vector control using the bypass flow in a dual throat nozzle

A fluidic thrust vector control using the bypass flow in a dual throat nozzle

Jet direction control using secondary flows

In recent years, studies on the fundamental principle of thrust vectoring using jets have been conducted with the aim of application to next-generation aircraft. Consequently, the improvement of aircraft motion performance is expected. Previously, a method using secondary flow with a Coanda surface was proposed for the direction control of the primary jet, and some valuable results were reported. The effect of ejection or suction on the traveling direction of the primary jet was examined. However, as many physical quantities dominate the phenomenon in this complicated situation, parametric studies are insufficient. The present study is a fundamental study of fluidic thrust vectoring. The effect of secondary injection or suction flow near the Coanda surface on the travel direction of primary jets was investigated parametrically using the momentum ratio, nozzle width ratio, etc. without changing the nozzle geometry. A larger deflection of the primary jet was observed because of the suction rather than ejection at the same momentum ratio. Furthermore, the effect of the slot width ratio on the dead zone where the traveling direction of the second jet does not depend on the momentum of the secondary flow was studied.