Control Vanes Research Articles

Vector ducted propeller aerodynamic modeling and verification testing

The tail-sitter aircraft has the advantages of both high-speed cruise and capability of the take-off and land vertically, high-performance control laws usually rely on the accurate flight mechanics model, while its flight aerodynamic modeling is a complex problem. This paper analytically develops an aerodynamic model of its propelling system based on first principles, including three components of a propeller, a vector duct, and eight slipstream vanes. This model can give the propeller’s induced velocity, power, thrust, and moment, also considers the augmented effect of ducted, and the lift and drag forces of vanes. Moreover, a propelling system test bed is built to measure the forces and moments along the body frame, which is composed of the tail-sitter prototype, power, communication link, upper system, and servo drive device. In addition, experimental results show the effectiveness of the model in estimating the thrust and torque with different angles of control vanes, the measured thrust is consistent with the calculated values, and the steering performance of each vane is further examined. The moments exerted on the two axes are linear with the vanes angles, and the symmetry is also well, which is convenient for flight controller design for this type of tail-sitter aircraft.

Overview of Selected Serpentine Duct Simulations Using Computational Fluid Dynamics

Computational fluid dynamics (CFD) was used to perform simulations of multiple serpentine inlet ducts for comparison to experimental data. The simulations included two baseline duct geometries configured to match their respective wind tunnel tests. Each configuration was tested and simulated with and without flow control vanes. Some of the simulations included the geometric detail of the instrumentation probes at the aerodynamic interface plane. This paper highlights selected issues that impact robustness and accuracy. The topics include far-field boundary conditions and various methods of modeling the instrumentation probes. This paper summarizes discussion topics and recommendations for CFD practitioners preparing to simulate similar cases.

An experimental and numerical analysis of residual stresses in a TIG weldment of a single crystal nickel-base superalloy

The Tungsten Inert Gas (TIG) welding technique is extensively used to join various automobile and aerospace components, such as control arms, rotating blades, and vanes. Highly localized heating followed by rapid cooling during welding exert complex thermal and mechanical loading on the components and give rise to significant residual stress fields which may increase the likelihood of time-dependent failure by promoting crack initiation. In the context of engineering design for structural integrity and reliability of operation, quantitative residual stress evaluation in the finished parts needs to be carried out in a reproducible manner. Samples investigated in this study were TIG fill-in weldments in single crystal superalloy components with nearly cylindrical geometry. The present research employed Focused Ion Beam – Digital Image Correlation (FIB-DIC) micro-ring-core technique for stress evaluation, and a sequentially coupled thermo-mechanical finite element model to assess the residual stress state near the weldment surface in the radial and hoop directions. Good agreement was obtained between experimentally evaluated residual stresses and the refined numerical predictions. The highest hoop and radial tensile residual stresses were both observed near the boundary between the filler metal and base metal, whilst a compressive region was found for hoop stress in the parent metal at the component edge. These observations were discussed in conjunction with the temperature history and residual stress self-equilibration. This research provides the foundation for further investigations of Post Weld Heat Treatment (PWHT) and surface treatment to improve the fatigue performance of weldments.

The influence of control vanes on pneumatic conveying of pulverised fuel at a trifurcator

Distribution of pulverised fuels in pneumatic conveying to conventional boilers is an ongoing research area with the intention of improving the performance of power-generating plants. One of the major challenges is the issue of obtaining an even fuel distribution across the fuel carrying lines to the burners or a customised distribution that satisfies the boiler load demand. A 1/3rd scale pneumatic conveying test rig was tested with inert cenosphere powder in a 3-way split configuration. Flow control vanes, similar to those applied in power plant pulverised fuel conveying lines were fitted into the junction and controlled using pneumatic proportional control actuators to alter the distribution of the powder in the three downstream branch pipes extending from the trifurcator. The measurement of the powder mass flux in each stream was carried out and the sensitivity of the particulate stream was assessed with respect to interference from the vane positions at the trifurcator.

Collocated attitude and vibrations control for square solar sails with tip vanes

This paper is devoted to developing collocated attitude and vibrations controllers for a square solar sail spacecraft containing four pre-tensioned triangular sails supported by flexible diagonal booms and four reflective control vanes at boom tips. Since the control torques for attitude control are created by the solar radiation pressure forces on the tip vanes, the attitude control problem is effectively non-collocated. The present work identifies collocated sensing for the tip vane forces which furnishes a passive input-output model. Various controllers are developed which furnish attitude and vibrations control. A finite-element-based linear structural model is used to evaluate the developed controllers and examine the controller-structure interactions.

RBF network based adaptive sliding mode control for solar sails

PurposeThe purpose of this paper is to resolve complex nonlinear dynamical problems of the pitching axis of solar sail in body coordinate system compared with inertial coordinate system. And saturation condition of controlled torque of vane in the orbit with big eccentricity ration, uncertainty and external disturbance under complex space background are considered.Design/methodology/approachThe pitch dynamics of the sailcraft in the prescribed elliptic earth orbits is established considering the torques by the control vanes, gravity gradient and offset between the center-of-mass (cm) and center-of-pressure (cp). The maximal torques afforded by the control vanes are numerically determined for the sailcraft at any position with any pitch angle, which will be used as the restriction of the attitude control torques. The finite/infinite time adaptive sliding mode saturation controller and Bang–Bang–Radial Basis Function (RBF) controller are designed for the sailcraft with restricted attitude control torques. The model uncertainty and the input error (the error between real input and ideal control law input) are solved using the RBF network.FindingsThe finite true anomaly adaptive sliding mode saturation controller performed better than the other two controllers by comparing the numerical results in the paper. The control torque saturation, the model uncertainty and the external disturbance were also effectively solved using the infinite and finite time adaptive sliding mode saturation controllers by analyzing the numerical simulations. The stabilization of the pitch motion was accomplished within half orbit period.Practical implicationsThe complex accurate dynamics can be approximated using the RBF network. The controllers can be applied to stabilization of spacecraft attitude dynamics with uncertainties in complex space environment.Originality/valueAdvanced control method is used in this paper; saturation of controlled torque of vane is resolved when the orbit with big eccentricity ration is considered and uncertainty and external disturbance under complex space background are settled. Moreover, complex and accurate nonlinear dynamical model of pitching axis of solar sail in body coordinate system compared with inertial coordinate system is provided.

Dynamic modeling and analysis of a flexible sailcraft

The coupled orbit, attitude and structural dynamics is very important for an orbiting sailcraft because the orbit is determined by the attitude, and the attitude and structural vibrations are affected mutually. Thus it is critical to derive the coupled dynamics and analyze how the vibrations are excited by the attitude motions, and how the orbit and attitude motions are affected by the vibrations. To solve this problem, the coupled orbit, attitude and structural dynamics is established for the sailcraft modeled by the Euler beam with large deformations merely experiencing the pitch motion in this paper. The Von-Karman’s nonlinear strain-displacement relation is adopted to consider the sailcraft with large transverse deformations, moderate rotations and small strains. The external loads include the torques by the control vanes, the offset between the center-of-mass (cm) and center-of-pressure (cp) and the gravity gradient force. The full nonlinear coupled dynamics denoted by “model 1” is established using Lagrange equation method based on the calculation of the kinetic energy, strain energy, the dissipation function and the external loads respectively. “model 2, 3” are obtained by neglecting the geometrically nonlinear terms, the second and higher terms including the vibration displacement, velocity and acceleration in “model 1” respectively, and “model 4” is a rigid body model. A 90deg pitch maneuver will be performed for the sailcraft initially on the geostationary (GEO) orbit for all the four models. The control torque generated by the control vanes is obtained based on the nonlinear optimal proportional–integral controller considering the saturation problem of the control vanes. The attitude, orbit and vibration responses are presented and compared to see the differences between the four models, some discussions and conclusions on the dynamics and control are also given, all based on the dynamics simulations.

On the development of the Anuloid, a disk-shaped VTOL aircraft for urban areas

This paper deals with the early development of the Anuloid, an innovative disk-shaped VTOL aircraft. The Anuloid concept is based on the following three main features: the use of a ducted fan powered by a turboshaft for the lift production to take-off and fly; the Coanda effect that is developed through the circular internal duct and the bottom portion of the aircraft to provide further lift and control capabilities; the adoption of a system of ducted fixed and swiveling radial and circumferential vanes for the anti-torque mechanism and the flight control. The early studies have been focused on the CFD analysis of the Coanda effect and of the control vanes; the flyability analysis of the aircraft in terms of static performances and static and dynamic stability; the preliminary structural design of the aircraft. The results show that the Coanda effect is stable in most of the flight phases, vertical flight has satisfactory flyability qualities, whereas horizontal flight shows dynamic instability, requiring the development of an automatic control system.

Dynamics of highly-flexible solar sail subjected to various forces

Solar sail is a novel spacecraft and has the potential applications in the near future. The large amplitude vibration should be considered because it is characterized by its huge and lightweight structure. In this paper, the supporting beam of solar sail is regarded as the most important structure and used to model the sailcraft as it accounts for most of the mechanical energies when it is in deformed configuration, also as the Euler beam can model the bending motion dominant sailcraft when it experiences attitude motions. The structural dynamics of solar sail supporting beam with geometric nonlinearity undergoing the forces generated by solar radiation pressure, sliding masses and control vanes are presented. The axial and transverse vibration equations with the properties of strong coupling, nonlinearity and time-varying coefficient matrices are obtained by using Lagrange equation method after calculating the related energies and works. The vibration equations are transformed into nonlinear algebraic equations utilizing implicit unconditionally stable Newmark-β algorithm for each time step. The nonlinear algebraic equations are solved by Newton-iterative algorithm. We compute and analyze the linear and nonlinear vibration responses affected by the mass and velocity of the sliding mass, the angular velocity of the force generated by control vane in detail. The computational results indicate that the mass and velocity of sliding mass affect the vibration responses (including the vibration frequency), but the angular velocity of the force generated by control vane hardly affects the vibration responses. Moreover, the linear and nonlinear vibrations are distinct obviously by comparing the linear and nonlinear responses. It is demonstrated that the geometric nonlinearity of the highly-flexible structure should be considered for performing vibration analysis exactly, and the vibration responses excited by the prescribed motion of the attitude control actuators should be analyzed carefully.

Assessment of ice plugging of a cooling water intake by a numerical model

American Electrical Power's Conesville plant had historically prevented ice buildup at a water intake by routing warm water from a once-through cooling system to the intake. In 2012, this system was retired and warm water was no longer available for de-icing. A numerical study was conducted to evaluate design alternatives to reduce ice transport to the intake. An Eulerian–Lagrangian model was used to predict the hydrodynamics and ice trajectories. A porous media model accounted for the ice accumulation in the trash racks. The model was capable of predicting the observed flow pattern. Predicted velocities compared well with measurements using large-scale particle image velocimetry (LSPIV). According to the model, sediment control vanes, placed in front of the intake to alleviate sediment ingestion, favour the ice transport to the intake. Based on model results, a mitigation plan to be implemented during several phases was elaborated.

Dynamics and Control of a Flexible Solar Sail

Solar sail can merely make use of solar radiation pressure (SRP) force as the thrust for space missions. The attitude dynamics is obtained for the highly flexible solar sail with control vanes, sliding masses, and a gimbaled control boom. The vibration equations are derived considering the geometric nonlinearity of the sail structure subjected to the forces generated by the control vanes, solar radiation pressure (SRP), and sliding masses. Then the dynamic models for attitude/vibration controller design and dynamic simulation are obtained, respectively. The linear quadratic regulator (LQR) based and optimal proportional-integral (PI) based controllers are designed for the coupled attitude/vibration models with constant disturbance torques caused by the center-of-mass (cm)/center-of-pressure (cp) offset, respectively. It can be concluded from the theoretical analysis and simulation results that the optimal PI based controller performs better than the LQR based controller from the view of eliminating the steady-state errors. The responses with and without the geometrical nonlinearity are performed, and the differences are observed and analyzed. And some suggestions are also presented.

Robust Model for the Design of Controller in Saucer UAV

The saucer UAV (Unmanned Aerial Vehicle) features both helicopter and traditional fixed-wing airplane, is capable of hovering, takeoff and landing vertically. The configuration of the UAV in this paper which is comprised of a propeller and there pairs of control vanes enclosed in the duct is new-style aircraft. In order to research the attitude control of the saucer UAV, this paper mainly focuses on the dynamic analysis and control model design of the vehicle. The dynamics of all the components of the UAV configuration is analyzed respectively first and then the complete nonlinear model is constructed from the forces and moments analysis of the vehicle. The model is simplified in the flight node of hovering. After that a robust model is designed to handle the parameter uncertainty and disturbance while in the hovering condition, and the simulation results are presented at last. Simulated results show the controller designed can guarantee the saucer UAV has good stable feature for operation and certain robustness.

Boundary-Layer-Ingesting Inlet Flow Control

An experimental study was conducted to provide the first demonstration of an active flow control system for a flush-mounted inlet with significant boundary-layer ingestion in transonic flow conditions. The effectiveness of the flow control in reducing the circumferential distortion at the engine fan-face location was assessed using a 2.5% -scale model of a boundary-layer-ingesting offset diffusing inlet. The inlet was flush mounted to the tunnel wall and ingested a large boundary layer with a boundary-layer-to-inlet height ratio of 35%. Different jet distribution patterns and jet mass-flow rates were used in the inlet to control distortion. A vane configuration was also tested. Finally, a hybrid vane/jet configuration was tested leveraging strengths of both types of devices. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass-flow rates through the duct and the flow control actuators. The distortion and pressure recovery were measured at the aerodynamic interface plane. The data show that control jets and vanes reduce circumferential distortion to acceptable levels. The point-design vane configuration produced higher distortion levels at off-design settings. The hybrid vane/jet flow control configuration reduced the off-design distortion levels to acceptable ones and used less than 0.5% of the inlet mass flow to supply the jets.

Aeroelastic stability analysis of a bridge deck with added vanes using a discrete vortex method

A two dimensional discrete vortex method (DIVEX) has been developed at the Department of Aerospace Engineering, University of Glasgow, to predict unsteady and incompressible flow fields around closed bodies. The basis of the method is the discretisation of the vorticity field, rather than the velocity field, into a series of vortex particles that are free to move in the flow field that the particles collectively induce. This paper gives a brief description of the numerical implementation of DIVEX and presents the results of calculations on a recent suspension bridge deck section. The results from both the static and flutter analysis of the main deck in isolation are in good agreement with experimental data. A brief study of the effect of flow control vanes on the aeroelastic stability of the bridge is also presented and the results confirm previous analytical and experimental studies. The aeroelastic study is carried out firstly using aerodynamic derivatives extracted from the DIVEX simulations. These results are then assessed further by presenting results from full time-dependent aeroelastic solutions for the original deck and one of the vane cases. In general, the results show good qualitative and quantitative agreement with results from experimental data and demonstrate that DIVEX is a useful design tool in the field of wind engineering.

Application of a discrete vortex method for the analysis of suspension bridge deck sections

A two dimensional discrete vortex method (DIVEX) has been developed to predict unsteady and incompressible flow fields around closed bodies. The basis of the method is the discretisation of the vorticity field, rather than the velocity field, into a series of vortex particles that are free to move in the flow field that the particles collectively induce. This paper gives a brief description of the numerical implementation of DIVEX and presents the results of calculations on a recent suspension bridge deck section. The predictions for the static section demonstrate that the method captures the character of the flow field at different angles of incidence. In addition, flutter derivatives are obtained from simulations of the flow field around the section undergoing vertical and torsional oscillatory motion. The subsequent predictions of the critical flutter velocity compare well with those from both experiment and other computations. A brief study of the effect of flow control vanes on the aeroelastic stability of the bridge is also presented and the results from DIVEX are shown to be in accordance with previous analytical and experimental studies. In conclusion, the results indicate that DIVEX is a very useful design tool in the field of wind engineering.

Application of the DRBEM to model ablation characteristics of a thrust vector control vane

A dual reciprocity boundary element method (DRBEM) is implemented to predict ablation in model thrust vector control (TVC) vanes. A moving front algorithm is described. Experimental data are available from tests performed on scaled vanes. Numerical results for recession of quarter-scale and half-scale vanes compare well with experimental data. Future work includes full coupling of the flowfield and conduction solutions.

Active Stabilization of Rotating Stall in a Three-Stage Axial Compressor

A three-stage, low-speed axial research compressor has been actively stabilized by damping low-amplitude circumferentially traveling waves, which can grow into rotating stall. Using a circumferential array of hot-wire sensors, and an array of highspeed individually positioned control vanes as the actuator, the first and second spatial harmonics of the compressor were stabilized down to a characteristic slope of 0.9, yielding an 8 percent increase in operating flow range. Stabilization of the third spatial harmonic did not alter the stalling flow coefficient. The actuators were also used open loop to determine the forced response behavior of the compressor. A system identification procedure applied to the forced response data then yielded the compressor transfer function. The Moore-Greitzer two-dimensional stability model was modified as suggested by the measurements to include the effect of blade row time lags on the compressor dynamics. This modified Moore-Greitzer model was then used to predict both the open and closed-loop dynamic response of the compressor. The model predictions agreed closely with the experimental results. In particular, the model predicted both the mass flow at stall without control and the design parameters needed by, and the range extension realized from, active control.

On the stability of a dirigible body

When the Magnus effects are completely absent the oscillatory motion of a dirigible body is said to be plane-yawing. Such bodies are stabilised by attaching fins or control vanes at their rear ends. Initial choice of the fin-size is made, depending on a static stability condition: JM < O, where JM is the normalised overturning aerodynamic moment coefficient. A proper fin-size requirement should normally be found from an appropriate dynamic stability condition. Under the very severe aerodynamic restriction stipulated above, one would expect, if the static stability condition is liberally satisfied by attaching over calibre fins, perhaps dynamic stability requirements could be met. This, however, may considerably reduce the ballistic range of the body. One would, therefore, need some sort of an upper majorant for JM consistent with the dynamic stability of the body and this should be a function of the other associated aerodynamic forces. In the present note a suitable majorant function for JM has been worked out. For this purpose, the aerodynamic coefficients are assumed to be slowly ranging functions of the path length as is usually stipulated. The stability problem has been solved using certain known results in the oscillation theory of differential equations.