Thrust Reduction Research Articles

Adaptive Robust Motion Control for Linear Induction Motor with Electromagnetic Nonlinearity Compensation

AbstractThis paper presents an adaptive robust motion control algorithm for linear induction motor (LIM) with electromagnetic nonlinearity compensation to suppress nonlinear magnetic thrust reduction due to the end effect. The electromagnetic compensation adaptive robust control (ECARC) algorithm is developed to deal with the parametric uncertainties and uncertain nonlinearities that are widely present in LIM. This algorithm employs a discontinuous projection‐type method to estimate the system parameters. The disturbance is bounded by a critical value, which guarantees that the system is exponentially stable. However, due to the magnetic field distortion caused by the opening of primary ends, the relationship between the driving current and the resultant motor thrust is nonlinear. Consequently, electromagnetic thrust and flux are calculated and used for feedback compensation. Different from the traditional vector control and direct torque control, the control algorithm employs electromagnetic thrust and magnetic flux to compensate torque current and magnetic field. Simulation results and comparative experimental results show that current control algorithm is accurate and efficient.

Characterization of Near-Propeller Bubbles and Fluctuation in Thrust Force in a Constant Torque Control Motor Propulsion System

In recent years, power trains that consist of propeller propulsion and motor drive systems have been widely used for battery electric boats, which are gaining popularity as a type of small boats, as well as for diesel electric ships that are renowned for their good maneuverability. The AC motor drive system used for these boats has a response time of just a few milliseconds — much quicker than that of the internal combustion engine. In addition, it is technically possible for the system to accurately monitor motor control signals (current, voltage, torque and rotational speed) in real time. In our previous report, we measured (torque signals, rotational speed signals and bubble behavior around the propeller) in the motor propulsion system under constant torque control in a circulating water channel through such means as analyzing high-speed video images. By analyzing rotational speed signals, we confirmed ahead of other researchers around the world, that it is possible to detect generated bubbles, measure its quantity, monitor the resulting thrust reduction and accurately gauge its magnitude. This report, has verified the results of our experiments theoretically by using the propeller characteristic equation. It has also demonstrated the possibility of improving propulsion efficiency enabled by suppressing the generation of bubbles and stabilizing the motor power output.

Wind tunnel experiments of a pair of interacting vertical-axis wind turbines

Vertical-axis wind turbines (VAWTs) have received a renewed interest in the wind energy research community, mainly for off-shore applications. One advantage is that installing a pair of counterrotating VAWTs on the same floating platform would result in thrust reduction and potential cancellation of the mooring yaw moment. In addition, such configurations could benefit from increased power output and reduced wake losses.In this article, we report on wind tunnel experiments to study the mechanical power output of a reference VAWT scale model, tested individually and in a closely-spaced pair of VAWTs. The power output of the individual VAWT configuration is compared with a pair of VAWTs spaced 1.3 diameters apart for two counterrotating directions. A net power increase in the power coefficient for the paired configuration of up to 17.0% compared with two individual rotors has been observed.

БЕЗЛЕТОВИЩНА ТРАНСПОРТНА АВІАЦІЯ – ПРОБЛЕМИ ТА ПЕРСПЕКТИВИ

The possibility used of the last achievements of fundamental science for creation of the engine for vertical take-off and landing flying platform (FP) are discussed. FP intended for transportation goods and passengers in speed range of 0 - 700 km/hour. It is offered to equip with engine creating flat stream of exhaust. At take-off, landing and patrol FP used the vertical direction nozzle working on the slot-hole ejector amplifier of thrust, on the cruiser mode - the pulling propeller variable pitch airplane type. The design of the engine allows redistributed power between a nozzle and the propeller by means change of gas turbine rotor position. On take-off mode FP the power release on nozzle are needed to be enough for lifting. On transient mode the increasing of the power release is needed to be on propeller at conservation the power release on nozzle. It can be reached by means off the change of propellers pitch. In this case the reduction of vertical thrust it can be compensated by an aerodynamic lift force which arising on wing and hull FP. The engine has a compressor, creating the flat stream of the compressed air, flat combustion chamber and flat nozzle, that is the engine must be executed in linear geometry. The linear compressor made as a twin-rotor Ruts vacuum pump. The brush seals from nanocarbon tube used for preservation of axial clearance between rotors. The shape of helical trilobal rotor provides increased overlap of phases of suck up, carried and injection. The material of gas turbine blades can be made by the method of nonpiston low temperature extrusion. The method allows to simplify substantially one of the most difficult operations the production of shafts and radial blades of turbine of half-open type. Other most details of engine can be made by method of ordinary extrusion also. The seals from nanocarbon may be used for the existing constructions of GTE also. The specific features of engine are the following: work on the slot amplifier of thrust without hydrodynamic losses; choice of optimal speed of rotation of rotors for every stage of compressor; possibility cooling of compressive air and pin zone of brush seals; enhanceable operating manufacturability and cheapness of production.

Full-Scale Turbofan Demonstration of a Deployable Engine Air-Brake for Drag Management Applications1

This paper presents the design and full-scale ground-test demonstration of an engine air-brake (EAB) nozzle that uses a deployable swirl vane mechanism to switch the operation of a turbofan's exhaust stream from thrust generation to drag generation during the approach and/or descent phase of flight. The EAB generates a swirling outflow from the turbofan exhaust nozzle, allowing an aircraft to generate equivalent drag in the form of thrust reduction at a fixed fan rotor speed. The drag generated by the swirling exhaust flow is sustained by the strong radial pressure gradient created by the EAB swirl vanes. Such drag-on-demand is an enabler to operational benefits such as slower, steeper, and/or aeroacoustically cleaner flight on approach, addressing the aviation community's need for active and passive control of aeroacoustic noise sources and access to confined airports. Using NASA's technology readiness level (TRL) definitions, the EAB technology has been matured to a level of six, i.e., a fully functional prototype. The TRL-maturation effort involved design, fabrication, assembly, and ground-testing of the EAB's deployable mechanism on a full-scale, mixed-exhaust, medium-bypass-ratio business jet engine (Williams International FJ44-4A) operating at the upper end of typical approach throttle settings. The final prototype design satisfied a set of critical technology demonstration requirements that included (1) aerodynamic equivalent drag production equal to 15% of nominal thrust in a high-powered approach throttle setting (called dirty approach), (2) excess nozzle flow capacity and fuel burn reduction in the fully deployed configuration, (3) acceptable engine operability during dynamic deployment and stowing, (4) deployment time of 3–5 s, (5) stowing time under 0.5 s, and (6) packaging of the mechanism within a notional engine cowl. For a typical twin-jet aircraft application, a constant-speed, steep approach analysis suggests that the EAB drag could be used without additional external airframe drag to increase the conventional glideslope from 3 deg to 4.3 deg, with about 3 dB noise reduction at a fixed observer location.

Влияние технологических погрешностей на кинематику вращательного перемещения осевого редуктора с горизонтальной реактивной тягой в групповом тяговом приводе локомотива

Objective: To obtain analytical responses of linear and angular movements of horizontal jet thrust and axial reduction unit, appearing in the process of their production and group tractive drive assembly, occurring as a result of vertical wheelset and engine’s undercarriage frame shifts during engine movement. The given responses are the basis for identifying its velocity, acceleration, and dynamic loads on drive components, as well as searching for methods to boost drive components reliability, taking into account its constructive specificities and running conditions. Methods: Analytical responses were identified on the basis of higher mathematics, the laws of theoretical mechanics as well as trigonometry knowledge application. Results: Analytical responses of kinematic spatial movements of horizontal jet thrust and an axial reduction unit with instrument accuracy of a group tractive drive were obtained from vertical engine’s undercarriage frame shifts and locomotives wheelset. Boundary conditions of jet thrust slopes were detected, as well as center lines of axial reduction units. The analysis of established relations was performed. Possible scheme variants of spatial movements of horizontal jet thrust and a wheel set axial reduction unit in engine’s undercarriage frame were presented with possible discrepancies of linear dimensions from production tolerance. Characteristic curves of vertical shifts of actual towline constructions from vertical shifts of undercarriage frame during locomotive’s movement were graphed. Practical importance: On the basis of obtained relations the analysis of linear displacement, angular velocities and accelerations of jet thrusts and wheel set axial reduction units is possible, as well as the generation of rational and robust wheel set cardan tractive gear constructions for locomotives with minimal dynamic load on its elements. The results of analytical research might be applied in the designing of new engines with high dynamic parameters.

Reduction of Radial Thrust by Using Triple-Volute Casing Centrifugal Pump

Reduction of Radial Thrust by Using Triple-Volute Casing Centrifugal Pump

Fuel Contamination on the Large Transport Airplanes

There have been different cases of aircraft accidents, due to the water contamination in the aviation fuel. Since large transport airplanes fly at very high altitudes, where ambient temperature can reach -6°C, water may freeze causing blockages in the fuel lines, filters, booster pumps, etc., and lead to engine thrust reduction and or engine shut down. Microbiological contamination of the fuel, due to microbial growth in the fuel, it can result in fuel tank structure corrosion, and in turn, leads to fuel leak. Fuel leak on hot engine surfaces or hot brakes can result into fire or explosion. In addition, the biological microorganisms in aviation fuel, can cause other technical problems such as it leads to fuel quantity gauge malfunctions, and fuel filter clogging. Therefore, it is important to eliminate or reduce the presence of the water and microbial growth in the in the fuel. The aim of this paper is to increase flight safety by minimizing the effect of water and biological contamination in the jet fuel. The proposed methodology, water contamination is eliminated by extracting water from fuel by using water/fuel separator and in addition, microbial contamination eliminated by uses the ultrasonic technology to destroy the bacteria in the fuel. Several experiments performed by taking fuel samples checked for presence of microbes, and then subjected to ultrasonic waves. The fuel sample located in a stainless steel and where it subjected to the ultrasonic externally (ultrasonic transmitter) located outside the tank and not on direct contact with fuel. The result show ultrasonic can heat up the fuel, and destroy the microorganisms effectively. During the experiments it has been observed that, for every five minutes of subjecting the fuel sample of 600 milliliters to ultrasonic of 42 KHz with power intensity of 50 watts, the fuel temperature increased by an average of about 6.2°C.

Design and Evaluation of Dynamic Positioning Controllers With Parasitic Thrust Reduction for an Overactuated Floating Platform

We investigate which control technique is the most suitable for the dynamic positioning of an overactuated platform. To this end, we develop a backstepping and a model predictive controller (MPC). The presence of redundant control inputs makes the stabilization of the position and the orientation of the platform challenging. Settling delays in the actuator thrust and angle, thrust saturation bounds, and jet rotational velocity bounds contribute to the challenge of the problem. To reduce energy consumption, we propose a technique for restricting the parasitic thrust effect. The significant energy reduction due to parasitic thrust restriction is illustrated in tables. The performance of the controllers is demonstrated by simulations, under realistic environmental disturbances, and is compared with that of a model-based PID controller previously developed, while the platform accomplishes two typical tasks. The evaluation criteria include energy consumption, robustness, and accuracy of the dynamic positioning. Results show the superiority of the MPC.

Thrust calculation of electric solar wind sail by particle-in-cell simulation

Abstract. In this study, thrust characteristics of an electric solar wind sail were numerically evaluated using full three-dimensional particle-in-cell (PIC) simulation. The thrust obtained from the PIC simulation was lower than the thrust estimations obtained in previous studies. The PIC simulation indicated that ambient electrons strongly shield the electrostatic potential of the tether of the sail, and the strong shield effect causes a greater thrust reduction than has been obtained in previous studies. Additionally, previous expressions of the thrust estimation were modified by using the shielded potential structure derived from the present simulation results. The modified thrust estimation agreed very well with the thrust obtained from the PIC simulation.

Infrared Signature of Aircraft Engine with Choked Converging Nozzle

Incorporation of an infrared suppressor is generally accompanied by a compromise in engine performance, which indirectly reduces the effectiveness of infrared signature suppression. This investigation illustrates the percentage increase in the infrared signature level in the and bands resulting from an increase in engine backpressure in a jet engine due to a reduction in the exit area of a choked converging nozzle. The effectiveness of optically blocking the hot engine parts by reducing the choked nozzle-exit area is estimated. Thermodynamic offdesign point analysis of the jet engine is done using GasTurb software to evaluate the percentage reduction in thrust and the net change in infrared signature level for the reduced choked converging nozzle-exit area relative to that for the design point.

The effect of friction and impact angle on the spermatozoa–oocyte local contact dynamics

Although a large proportion of biomolecules involved in spermatozoa–oocyte interaction has been discovered so far, many details of fertilization mechanism remain unknown. Both biochemical and biomechanical components exist in the fertilization process. Mammalian sperm evolved a ZP (zona pelucida) thrust reduction penetration strategy probably in response to the ZP resilient elasticity.Using a biomechanical approach and FEM analysis, local contact stress, ZP deformations during impact and attempt of sperm head penetration relative to different sperm impact angles (SIA) were studied. The sperm–oocyte contact was defined as non-linear frictional contact. A transient structural analysis at 37°C revealed that, from the mechanical standpoint there are SIA that are more favorable for possible ZP penetration due to larger equivalent stress of ZP. An “slip-stick” resembling effect was identified for almost all examined SIA. The sperm head–ZP contact area increases as SIA decreases. Favorable ZP-stress state for sperm penetration regarding SIA are discussed.

URANSE simulation of an active variable-pitch cross-flow Darrieus tidal turbine: Sinusoidal pitch function investigation

This article describes a 2D CFD simulation implementation of a crossflow tidal turbine, the blades of which have their pitch modified during revolution. Unsteady flow around the turbine is computed with an URANSE method, using the solver ANSYS-CFX. Spatial and temporal discretizations have been studied. The pitch motion of the blades is obtained through mesh deformation, and the main rotation is implemented through sliding boundaries, with general grid interface model. The turbulence model used is kω SST. Langtry Menter transition model was tried but showed high discrepancies with experimental results. Five experimental cases were used to assess the accuracy of the simulation. It provided accurate computed forces for a wide range of tip speed ratios, and proved to be suitable for exploratory simulations. Harmonic pitch control was thus implemented for a tip speed ratio of 5, close to an operational value for a crossflow turbine. First, second and third harmonics pitch function were tested. It was shown that an improvement of more than 50% could be achieved with the second harmonics, with a large reduction in thrust. The flow inside the turbine and close to the blade was examined so that the case of performance improvement due to pitch control could be clearly understood. It was observed that turbine efficiency improvement requires a very slight recirculation and an angle of attack decrease on the upstream part of the turbine, and an angle of attack increase on the downstream part. The flow deceleration through the turbine was found to be a primary factor in pitch function as well. Moreover the hydrodynamic torque and thus the energy required to control the pitch were found to be insignificant.

ELECTROSTATIC ION THRUSTERS - TOWARDS PREDICTIVE MODELING

For satellite missions, thrusters have to be qualified in large vacuum vessels to simulate space environment. One caveat of these experiments is the possible modification of the beam properties due to the interaction of the energetic ions with the vessel walls. Impinging ions can produce sputtered impurities or secondary electrons from the wall. These can stream back into the acceleration channel of the thruster and produce co-deposited layers. Over the long operation time of thousands of hours, such layers can modify the optimized geometry and induce changes of the ion beam properties, e.g. broadening of the angular distribution and thrust reduction. To study such effects, a Monte Carlo code for the simulation of the interaction of ion thruster beams with vessel walls was developed. Strategies to overcome sputter limitations by additional baffles are studied with the help of this Monte-Carlo erosion code.<br /><br />

Numerical investigations on the aerodynamic performance of wind turbine: Downwind versus upwind configuration

Although the upwind configuration is more popular in the field of wind energy, the downwind one is a promising type for the offshore wind energy due to its special advantages. Different configurations have different aerodynamic performance and it is important to predict the performance of both downwind and upwind configurations accurately for designing and developing more reliable wind turbines. In this paper, a numerical investigation on the aerodynamic performance of National Renewable Energy Laboratory (NREL) phase VI wind turbine in downwind and upwind configurations is presented. The open source toolbox OpenFOAM coupled with arbitrary mesh interface (AMI) method is applied to tackle rotating problems of wind turbines. Two 3D numerical models of NREL phase VI wind turbine with downwind and upwind configurations under four typical working conditions of incoming wind velocities are set up for the study of different unsteady characteristics of the downwind and upwind configurations, respectively. Numerical results of wake vortex structure, time histories of thrust, pressure distribution on the blade and limiting streamlines which can be used to identify points of separation in a 3D flow are presented. It can be concluded that thrust reduction due to blade-tower interaction is small for upwind wind turbines but relatively large for downwind wind turbines and attention should be paid to the vibration at a certain frequency induced by the cyclic reduction for both configurations. The results and conclusions are helpful to analyze the different aerodynamic performance of wind turbines between downwind and upwind configurations, providing useful references for practical design of wind turbine.

Simulation study of the plasma-brake effect

Abstract. Plasma brake is a thin, negatively biased tether that has been proposed as an efficient concept for deorbiting satellites and debris objects from low Earth orbit. We simulate the interaction with the ionospheric plasma ram flow with the plasma-brake tether by a high-performance electrostatic particle in cell code to evaluate the thrust. The tether is assumed to be perpendicular to the flow. We perform runs for different tether voltage, magnetic-field orientation and plasma-ion mass. We show that a simple analytical thrust formula reproduces most of the simulation results well. The interaction with the tether and the plasma flow is laminar (i.e. smooth and not turbulent) when the magnetic field is perpendicular to the tether and the flow. If the magnetic field is parallel to the tether, the behaviour is unstable and thrust is reduced by a modest factor. The case in which the magnetic field is aligned with the flow can also be unstable, but does not result in notable thrust reduction. We also correct an error in an earlier reference. According to the simulations, the predicted thrust of the plasma brake is large enough to make the method promising for low-Earth-orbit (LEO) satellite deorbiting. As a numerical example, we estimate that a 5 km long plasma-brake tether weighing 0.055 kg could produce 0.43 mN breaking force, which is enough to reduce the orbital altitude of a 260 kg object mass by 100 km over 1 year.

Computational Exploration of a Two-Spool High Bypass Turbofan Engine's Component Deterioration Effects on Engine Performance

Aircraft engines are exposed to degradation due to several factors such as environmental air pollution, fuel content and ageing or degradation of engine’s components, which are experienced within specified time. While the turbofan in operation, its components deteriorate and consequently affect its performance. This study is aimed to computationally investigate the effect of components degradation on engine performance. A high bypass turbofan engine operated at cruise is selected for this evaluation and the simulation was performed using the Gas Turbine Simulation Program (GSP). The affected components considered are turbines and compressors with deterioration rate ranging from 0% to 5%. The effect of selected deterioration rate on engine thrust and thrust specific fuel consumption (TSFC) is studied. Results obtained show an agreement with literature where reduction in engine thrust and TSFC are observed. Turbine’s fouling has been found to be more severe than erosion in terms of power and efficiency losses. However, in terms of the overall performance, the erosion effect is more severe than fouling.

Propulsive performance of unsteady tandem hydrofoils in a side-by-side configuration

Experimental and analytical results are presented on two identical bio-inspired hydrofoils oscillating in a side-by-side configuration. The time-averaged thrust production and power input to the fluid are found to depend on both the oscillation phase differential and the transverse spacing between the foils. For in-phase oscillations, the foils exhibit an enhanced propulsive efficiency at the cost of a reduction in thrust. For out-of-phase oscillations, the foils exhibit enhanced thrust with no observable change in the propulsive efficiency. For oscillations at intermediate phase differentials, one of the foils experiences a thrust and efficiency enhancement while the other experiences a reduction in thrust and efficiency. Flow visualizations reveal how the wake interactions lead to the variations in propulsive performance. Vortices shed into the wake from the tandem foils form vortex pairs rather than vortex streets. For in-phase oscillation, the vortex pairs induce a momentum jet that angles towards the centerplane between the foils, while out-of-phase oscillations produce vortex pairs that angle away from the centerplane between the foils.

Phasing issues in the seismic response of yielding, gravity-type earth retaining walls – Overview and results from a FEM study

An overview of past and recent developments on the subject of seismic earth pressures on yielding, gravity-type walls, retaining cohesionless backfill, is first presented, focusing on available data on the issue of phase difference that develops between the peak values of wall inertia and seismic earth thrust increment. The results of a FEM parametric study are next presented regarding the dependence on the resulting dynamic earth thrust reduction – acting on the time of peak wall inertia – on backfill rigidity, wall height, and shaking characteristics. The reliability of the numerical analyses was verified by modeling centrifuge tests reported by Nakamura [24] and successfully comparing measured vs. computed behavior. The results of the parametric analyses indicate that the seismic active earth thrust, acting on the wall at the time of maximum wall inertia, is significantly reduced (compared to its peak value) with increasing shaking intensity of backfill, increasing wall displacements, increasing wall height, and decreasing backfill rigidity. No systematic dependence on the ratio of input motion frequency to the natural frequency of the backfill (f/f1) was observed. The above findings: (1) verify earlier experimental and numerical results, (2) explain the reported lack of damage to retaining walls under strong ground shaking, and (3) indicate the need for revising the pertinent provisions of current seismic codes. Graphs summarizing the results of the numerical analyses are presented which may be used as a guide for selecting the magnitude of seismic active earth thrust that needs to be taken into account in the design of the examined type of earth retaining walls.

Periodically plunging foil near a free surface

Experiments were performed to investigate the effects of amplitude and depth on the drag reduction of a NACA 0012 airfoil plunging near a free surface for a range of frequencies. Beyond the effect of the free surface, at low Strouhal numbers based on amplitude, Sr A, the drag reduction follows a parabolic trend with greater effect for greater amplitude, similar to the Garrick predictions. At Sr A ≈ 0.08, larger amplitudes break from this trend due to leading-edge vortex formation. As a result, smaller amplitudes become preferable for Sr A > 0.12. In addition, for the first time, vortex lock-in is documented experimentally. The effect of depth is twofold; firstly with decreasing depth, there is a general departure from the Garrick trends. Secondly, a reduction in thrust is observed around a constant unsteady parameter of τ = U ∞ 2πf/g ≈ 0.25; around this value significant free-surface waves form that detract from thrust creation. For depths greater than two chord lengths, there is negligible free-surface effect.