ADVANCED FLUIDIC THRUST VECTORING WITH DUAL THROAT NOZZLE: ACHIEVING SUPERIOR THRUST VECTORING ANGLE AND EFFICIENCY WITH DUAL PORT INJECTION

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

<div class="section abstract"><div class="htmlview paragraph">The Dual Throat Nozzle (DTN) is a unique nozzle configuration that enables fluidic thrust vectoring (FTV), improving aircraft maneuverability while reducing the mechanical complexity of traditional vectoring systems. In this study, a two-dimensional DTN was developed based on a validated NASA Langley model, incorporating a newly designed plenum geometry guided by area expansion ratio principles. Numerical simulations were carried out in ANSYS Fluent using a density-based, steady-state solver with the SST k–<i>ω</i> turbulence model to capture key compressible flow features such as shock waves, flow separation, and jet deflection. Secondary injection rates were determined using choked-flow relations, and a 12-case parametric study was conducted to analyze the effects of Nozzle Pressure Ratio (NPR), injection rate, and injection angle on thrust deflection and efficiency. The simulation results at NPR = 4 with 3% injection showed strong agreement with NASA experimental data, validating the computational setup. It was observed that higher NPR values reduced jet deflection but improved overall thrust efficiency, with the best performance achieved at NPR = 2 and a 150° injection angle. The findings provide valuable insight into optimizing DTN design parameters for lightweight, efficient fluidic thrust vectoring systems suited to future supersonic applications.</div></div>

Shock vector control (SVC) is one of the most researched topics in the field of fluidic thrust vectoring (FTV). In SVC, a secondary fluid flows through an injector to deflect the primary flow through the nozzle. However, the losses associated with the secondary injection is significantly high due to engine bleed. Modern research on SVC focuses on the use of bypass passage in order to mitigate this loss. The present study deals with this so-called bypass-SVC on altitude-adaptive double-divergent nozzles (DDNs), which have two diverging sections separated by an inflection point. The inflection Mach number is set to be 1.5. Three different DDN configurations have been studied in this work by varying the lengths of the diverging sections. The steady-state flow-field has been numerically solved using ANSYS Fluent software over a range of nozzle pressure ratios (NPRs), and results have been compared to a single-divergent nozzle (SDN) of the same nozzle area expansion ratio (ε). The results indicate higher pitch thrust vector angle (δp) for the DDNs as compared to the SDN at certain NPRs. Also, the thrust losses (ω) have been observed to be less for the DDNs as compared to the SDN at higher NPRs. In the non-vectored state, the coefficient of thrust (CF) of the DDNs is comparable with that of the SDN.

Dual-throat Nozzle (DTN) is known as one of the most effective approaches of fluidic thrust-vectoring.It is flourishing into a promising technology to implement supersonic and hypersonic thrust-vector control in aircrafts.The main objective of the study is numerical investigation of the effects of secondary injection geometry and the cavity angles on the performance of a planar dual throat thrust-vectoring nozzle.The main contributions of the study is to consider the rate of secondary injection and cavity section with different angle configuration of the DTN, and the impacts is examined.2-D compressible reacting simulations have been conducted in order to resolve the flow field in a dual throat nozzle with Nozzle pressure ratio of 5.The RANS equation, Energy equation is solved along with the standard k - model for the turbulence closure.Parameters such as convergence angle in the cavity & secondary injection angle are invoked to analyze the better thrust vectoring angle.Results reveal that a maximum vector angle of 10.96 degrees is a secondary injection rate equal to 20% of primary flow rate with a cavity convergence angle of 30 degrees.Findings suggest that the higher thrust vectoring is offered by a DTVN with higher cavity convergence angle with lesser percentage of secondary inlet.

Computational studies are conducted on the supersonic nozzle to investigate the possibility of utilizing counter-flow in fluidic thrust vector control. In this work, the design Mach number of the symmetric supersonic nozzle is set to be 2.5. For the validation of methodology, numerical results are compared with experimental data referred from the literature. Two-dimensional numerical simulations are based on well-assessed standard k–ɛ turbulence model with standard wall functions. Second-order accuracy is ensured to reveal more details of flow field. The system thrust ratio, deflection angle, and secondary mass flow ratio were studied for a wide range of nozzle pressure ratios and secondary pressure ratios. The results indicate that deflection angle and secondary mass flow ratio are found to be decreased with increasing nozzle pressure ratio as well as system thrust ratio. The secondary mass flow ratio and deflection angle decrease with the increase of secondary pressure ratio, and system thrust ratio increases with the increasing of secondary pressure ratio. The secondary mass flow rate remains under 2.4% of the primary flow to obtain efficient thrust vector control at high Mach number.

Lighter weight, simpler structure, higher vectoring efficiency and faster vector response are recent trends in development of aircraft engine exhaust system. To meet these new challenges, a concept of hybrid SVC nozzle was proposed in this work to achieve thrust vectoring by adopting a rotatable valve and by introducing a secondary flow injection. In this paper, we numerically investigated the flow mechanism of the hybrid SVC nozzle. Nozzle performance (e.g. the thrust vector angle and the thrust coefficient) was studied with consideration of the influence of aerodynamic and geometric parameters, such as the nozzle pressure ratio (NPR), the secondary pressure ratio (SPR) and the deflection angle of the rotatable valve (θ). The numerical results indicate that the introductions of the rotatable valve and the secondary injection induce an asymmetrically distributed static pressure to nozzle internal walls. Such static pressure distribution generates a side force on the primary flow, thereby achieving thrust vectoring. Both the thrust vector angle and vectoring efficiency can be enhanced by reducing NPR or by increasing θ. A maximum vector angle of 16.7 ° is attained while NPR is 3 and the corresponding vectoring efficiency is 6.33 °/%. The vector angle first increases and then decreases along with the elevation of SPR, and there exists an optimum value of SPR for maximum thrust vector angle. The effects of θ and SPR on the thrust coefficient were found to be insignificant. The rotatable valve can be utilized to improve vectoring efficiency and to control the vector angle as expected.

Experimental investigation and numerical analysis on high-efficiency shock vectoring control serpentine nozzles

Dual throat nozzle (DTN) is fast becoming a popular technique for thrust vectoring. The DTN is designed with two throats, an upstream minimum and a downstream minimum at the nozzle exit, with a cavity in between the upstream throat and exit. In the present study, a computational work has been carried out to analyze the performance of a dual throat nozzle at various mass flow rates of secondary flow and nozzle pressure ratios (NPR). Two-dimensional, steady, compressible Navier-Stokes equations were solved using a fully implicit finite volume scheme. The present computational results were validated with available experimental data. Based on the present results, the control effectiveness of thrust-vectoring is discussed in terms of the thrust coefficient and the coefficient of discharge.

The objective of this paper is to investigate the fluidic thrust vectoring (FTV) effects of a secondary jet on the primary flow in a converging-diverging nozzle. The experiments are performed with a nozzle pressure ratio (NPR) of 4-10, a secondary pressure ratio (SPR) of 1 or 2, and two different secondary jet locations. Numerical simulations of the nozzle flow are carried out by solving the Navier-Stokes equation, and the input parameters are set to match the experimental conditions. Computations are performed with and without the secondary jet injection for different combinations of NPR, SPR, and jet location. The thrust pitching moment is also determined to evaluate the FTV performance. It is found that the thrust pitching moment increases with the SPR. The numerical results clearly indicate two FTV mechanisms induce thrust pitching moments with opposite signs.

A Dual Throat Nozzle fluidic thrust vectoring technique that achieves higher thrust-vectoring efficiencies than other fluidic techniques, without sacrificing thrust efficiency has been developed at NASA Langley Research Center. The nozzle concept was designed with the aid of the structured-grid, Reynolds-averaged Navier-Stokes computational fluidic dynamics code PAB3D. This new concept combines the thrust efficiency of sonic-plane skewing with increased thrust-vectoring efficiencies obtained by maximizing pressure differentials in a separated cavity located downstream of the nozzle throat. By injecting secondary flow asymmetrically at the upstream minimum area, a new aerodynamic minimum area is formed downstream of the geometric minimum and the sonic line is skewed, thus vectoring the exhaust flow. The nozzle was tested in the NASA Langley Research Center Jet Exit Test Facility. Internal nozzle performance characteristics were defined for nozzle pressure ratios up to 10, with a range of secondary injection flow rates up to 10 percent of the primary flow rate. Most of the data included in this paper shows the effect of secondary injection rate at a nozzle pressure ratio of 4. The effects of modifying cavity divergence angle, convergence angle and cavity shape on internal nozzle performance were investigated, as were effects of injection geometry, hole or slot. In agreement with computationally predicted data, experimental data verified that decreasing cavity divergence angle had a negative impact and increasing cavity convergence angle had a positive impact on thrust vector angle and thrust efficiency. A curved cavity apex provided improved thrust ratios at some injection rates. However, overall nozzle performance suffered with no secondary injection. Injection holes were more efficient than the injection slot over the range of injection rates, but the slot generated larger thrust vector angles for injection rates less than 4 percent of the primary flow rate.

The dynamic response of a Dual-Throat Nozzle in open and closed-loop control is investigate numerically. Thrust vectoring in fixed, symmetric nozzles is obtained by secondary flow injections that cause local flow separations, asymmetric pressure distributions and the vectoring of primary jet flow. The computational technique is based on a model for the compressible URANS equations. A minimal control system governs the unsteady blowing. Nozzle performances and thrust vector angles have been computed for a wide range of nozzle pressure ratios and secondary flow injection rates. The numerical results are compared with the experimental data available in the open literature. Several computations of the open-loop dynamics of the nozzle under different forcing have been performed in order to investigate the system response in terms of thrust vectoring effectiveness and controllability. These computations have been used to extract ARX models of the nozzle dynamics. The effects of including the actuator dynamics are also discussed. Simple strategies of closed-loop control of the nozzle system by PID regulators are investigated numerically. The closed-loop Model Predictive Control of the system, based on the ARX models, is addressed

The paper focuses on a computational method for the investigation of Fluidic Thrust Vectoring (FTV). Thrust vectoring in symmetric nozzles is obtained by secondary flow injections that cause local flow separations, asymmetric pressure distributions and, therefore, the vectoring of the primary jet thrust. The methodology proposed here can be applied for studying numerically most of the strategies for fluidic thrust vectoring, as shock-vector control, sonic-plane skewing and the counterflow method. The computational technique is based on a well-assessed mathematical model. The flow governing equations are solved according to a finite volume discretization technique of the compressible RANS equations coupled with the Spalart-Allmaras turbulence model. Second order accuracy in space and time is achieved using an Essentially Non Oscillatory scheme. For validation purposes, the proposed numerical tool is used for the simulation of thrust vectoring based on FTV strategies as the shock vector control and the dual-throat nozzle concept, with a special attention to the latter case. Nozzle performances and thrust vector angles are computed for a wide range of nozzle pressure ratios and secondary flow injection rates. The numerical results obtained are compared with the experimental data available in the open literature.

A computational and experimental study was conducted to investigate the effects of multiple injection ports in a two-dimensional, convergent-divergent nozzle, for fluidic thrust vectoring. The concept of multiple injection ports was conceived to enhance the thrust vectoring capability of a convergent-divergent nozzle over that of a single injection port without increasing the secondary mass flow rate requirements. The experimental study was conducted at static conditions in the Jet Exit Test Facility of the 16-Foot Transonic Tunnel Complex at NASA Langley Research Center. Internal nozzle performance was obtained at nozzle pressure ratios up to 10 with secondary nozzle pressure ratios up to 1 for five configurations. The computational study was conducted using the Reynolds Averaged Navier-Stokes computational fluid dynamics code PAB3D with two-equation turbulence closure and linear Reynolds stress modeling. Internal nozzle performance was predicted for nozzle pressure ratios up to 10 with a secondary nozzle pressure ratio of 0.7 for two configurations. Results from the experimental study indicate a benefit to multiple injection ports in a convergent-divergent nozzle. In general, increasing the number of injection ports from one to two increased the pitch thrust vectoring capability without any thrust performance penalties at nozzle pressure ratios less than 4 with high secondary pressure ratios. Results from the computational study are in excellent agreement with experimental results and validates PAB3D as a tool for predicting internal nozzle performance of a two dimensional, convergent-divergent nozzle with multiple injection ports.

The objectives of this paper are to compare the effect of fluidic thrust vectoring (FTV) parameters on two converging-diverging nozzle models and discuss the relation of evaluation methods between thrust pitching angle and thrust pitching moment. The interaction of a secondary jet with the primary jet flow in two nozzle models is also investigated. Numerical and experimental studies of FTV were done with nozzle model 1 and nozzle model 2. The experiments are carried out with a nozzle pressure ratio (NPR) of 3-10, a secondary pressure ratio (SPR) of 1, 2 and 3, and two different secondary jet locations. Numerical simulations of the nozzle flow are performed with solving the Navier-Stokes equation, and the parameters are the same with the experimental conditions. Combinations of NPR, SPR, and secondary jet location are set to compare the performance of the two nozzle models. The thrust pitching moment and the thrust pitching angle are determined to evaluate the FTV performance. Positive inter-relation betwe...

Shock vector control (SVC) based on transverse jet injection is one of the fluidic thrust vectoring (FTV) technologies, and is considered as a promising candidate for the future exhaust system working at high nozzle pressure ratio (NPR). However, the low vector efficiency (η) of the SVC nozzle remains an important problem. In the paper, a new method, named as the improved SVC, was proposed to improve the vector efficiency (η) of a SVC nozzle, which enhances the vector control of primary supersonic flow by adopting a bypass injection. It needs less secondary flow from high pressure component of an aero-engine and has smaller influence on the working character of an aero-engine. The flow mechanism of the improved SVC nozzle was investigated by solving three-dimensional Reynolds-averaged Navier--Stokes with shear stress transport (SST) κ–ω turbulence model. The shock waves, jets-primary flow interactions, flow separation, and vector performance were analyzed. The influences of aerodynamic and geometric parameters, namely, NPR, secondary pressure ratio (SPR), and bypass injection position (Xj.ad.) on flow characteristics and vector performance were investigated. Based on the design of experiment (DOE), the response surface methodology (RSM) and the simulation model of an aero-engine, a method to estimate the coupling performance of the improved SVC nozzle and an aero-engine was studied, and a new balance relationship between the improved SVC nozzle and an aero-engine was established. Results shows that (1) with the assistance of bypass injection, the jet penetration and the capability of vector control are largely improved, resulting in a vector efficiency (η) of 1.98 deg/%-ω at the designed NPRD = 13.88; (2) in a wide range of operating conditions, larger vector angle (δp), higher thrust coefficient (Cfg), and higher vector efficiency (η) of the improved SVC nozzle were obtained, (3) in the coupling process of the improved SVC nozzle and an aero-engine, a δp of 18.1 deg was achieved at corrected secondary flow ratio of 10% and corrected bypass ratio of 6.98%, and the change of the thrust and the specific fuel consumption (SFC) were within 12%, which is better than the coupling performance of a SVC nozzle and an aero-engine.