Thrust Curve Research Articles

Experimental Study and Application Prospects of Coal Dust/Methane/Oxygen Pulse Detonation Performance: Coal Dust Equivalence Ratio and Types.

In order to achieve reliable application of coal in pulse detonation combustion chambers, this study explored the influence mechanism of equivalence ratio and coal type (lignite, anthracite) on the detonation characteristics of coal/methane/oxygen methane-solid two-phase fuel. A high-energy ignition device was used to ignite the preblast methane fuel, and the high-temperature and high-pressure energy generated directly initiated the detonation of coal/methane/oxygen methane-solid two-phase fuel. The experimental results are as follows: (1) The maximum detonation pressure of coal/methane/air fuel is positively correlated with the initial pressure. With the increase of the φglobal, the maximum detonation pressure of the two types of coal gradually increases. To be specific, when the φglobal rises from 0.5 to 1.6, the sensitivity of lignite and anthracite to the maximum detonation pressure with respect to the initial pressure increases from 4.56 to 6.11 and 5.48, respectively; (2) In terms of detonation flame and maximum pressure wave velocity, anthracite shows better dynamic performance than lignite. The maximum velocity of detonation flame and pressure wave is achieved when the φglobal is 1.4. (3) In terms of detonation thrust performance, as the φglobal increases from 0.5 to 1.6, the rate of increase in average thrust of the two types of coal first increases and then decreases. Compared with lignite, anthracite has a wider time domain and higher peak value in the average thrust curve and the generated detonation wave displays a greater impulse. The experimental data and conclusions obtained in this study are of practical significance for realizing the engineering application of pulverized coal detonator power generation.

Aerodynamic Performance of a Hovering Cycloidal Rotor: A CFD Study with Experimental Validation

A three‐dimensional (3D) unsteady Reynolds averaged Navier‐Stokes (URANS) computational fluid dynamics (CFD) toolkit for cycloidal rotors was developed and used to perform a parametric study. It included blade aspect ratio, side disks, pitch mechanism, blade camber, and shaft size. The influence of the pitch rod length showed the importance of the lift distribution between the upstream and downstream parts of the rotor cylinder. The application of blade camber significantly affected thrust and power, while having a limited effect on efficiency. A similar effect was obtained by varying the pitch rod lengths. The presence of a central axis in the rotor had a negligible effect on efficiency. The most significant impact on efficiency came from the side disks, which behaved similarly to winglets on fixed‐wing aircraft. However, changing the aspect ratio of the blades showed a similar response to that of aircraft wings, but with a smaller effect, making it conceivable to fly a square-bladed cyclorotor without side disks. To verify the CFD model, a cycloidal rotor was also built using 3D printed parts and carbon fiber tubing. It was then operated on a test rig where thrust and power were measured for speeds ranging from 408 to 2528 RPM. On the test bench, the blades were pitched with a uniform asymmetric mechanism. The maximum nose‐up pitch angle in upstream of the rotor axis was 34.8°. Due to its rotation around the rotor and its pitching in the opposite direction, the maximum nose‐up pitch angle of the downstream blade was 38.6°. The obtained rotor thrust and power curves and the flow visualization around the rotor confirmed the validity of the CFD toolkit.

On the Multidisciplinary Design of a Hybrid Rocket Launcher with a Composite Overwrapped Pressure Vessel

A multidisciplinary design optimisation (MDO) study of a hybrid rocket launcher is presented, with a focus on quantifying the impact of using composite overwrapped pressure vessels (COPVs) as the oxidiser tank. The rocket hybrid propulsion system (RHPS) consists of a combination of solid fuel (paraffin) and liquid oxidiser (NOx). The oxidiser is conventionally stored in metallic vessels. Alternative design concepts involving composite-based pressure vessels are explored that could lead to significant improvements in the overall performance of the rocket. This design choice may potentially affect parameters such as total weight, thrust curve, and maximum altitude achieved. With this eventual impact in mind, structural considerations such as wall thickness for the COPV are integrated into an in-house MDO framework to conceptually optimise a hybrid rocket launcher.

Two-scale blockage correction for an array of tidal turbines

It has been shown theoretically that tidal fences consisting of multiple turbines placed side-by-side can makeuse of constructive interference (local blockage) effects to raise the energy extraction efficiency of the fenceabove that of the Betz limit applicable to unblocked flow problems. For the two-scale problem of a longarray of turbines partially spanning the width of a much wider channel (vanishing global blockage) theefficiency of energy extraction, normalised on the undisturbed kinetic energy flux, rises from the Betz limitof 0.593 to the partial fence limit of 0.798 [1]. Experiments on pairs of side-by-side turbines at largelaboratory scale [2] have confirmed the important aspects of the underlying partial fence theory and thatsome of the performance benefits offered by constructive interference effects can be achieved in practice.
 Experimental validation in wind tunnels, towing tanks and other laboratory facilities are however prone toglobal blockage effects not seen in full-scale open flows due to the close proximity of flow boundaries to thebody. These global blockage effects modify the thrust and power performance of the turbines, such thatcorrections to experimental curves are necessary to either translate laboratory-scale experimental results tofull-scale conditions, or to calculate the expected loads and power on tidal turbines deployed in blocked-flowconditions [3][4]. The difficulty applying blockage corrections to turbine arrays is the non-linear interactionbetween local and global blockage. These two effects cannot be simply decoupled as for various turbine tip-to-tip spacings (affecting local blockage), changes in the global blockage have a different impact on turbineperformance.
 A number of blockage corrections have been developed for single turbines operating in blocked flowconditions. These corrections typically seek to describe an equivalent free-stream velocity which, in theabsence of global blockage, would result in the same thrust and velocity through the turbine as in the blockedcase. Thrust and power curves are then scaled non-linearly with the ratio of the experimental tank velocityand the equivalent free-stream velocity [5]. These single turbine blockage corrections can however onlyaccount for global blockage, and simplifications must currently be made based on the assumption that globaland local blockage effects can be linearly decoupled [2].
 This work therefore presents an analytical blockage correction for co-planar arrays of tidal turbines based ontwo-scale momentum theory [1]. This correction is then compared to other models, particularly for turbinearray experimental test data. Finally, RANS computations for a turbine array at various global blockageratios is compared to the analytical model, demonstrating its validity. A particularly useful aspect of thetheoretical model is to allow for experimental quantification of the local-blockage effect for finite lengthfences. For instance, doubling the fence length doubles the global blockage, but increases in fence thrust andpower cannot be attributed only to the change in global blockage due to non-linear coupling. This correctionallows for a decoupling of these two effects, such that the local blockage effect can be isolated andquantified.

Research on swimming performance of fish in different species

Manta rays and tunas are outstanding representatives of propulsion by MPF (median and/or paired fin) and BCF (body and/or caudal fin), respectively, and it is an interesting topic to see what kind of fluid effects will be generated when they meet during the swimming process. In the present study, numerical simulations were performed for the individual swimming state of manta ray/tuna and the group swimming of manta ray and tuna in a tandem arrangement. In individual swimming conditions, increasing amplitude helps to improve manta ray thrust and increasing wave number helps to improve manta ray efficiency; increasing frequency, tuna thrust increases monotonically and efficiency increases first and then decreases. In the tandem group swimming state, the manta ray thrust and efficiency are enhanced at most spacings, the smaller the spacing, the greater the enhancement, as seen in the vortex structure, which benefits from the merging of the rear tuna wake. The thrust and efficiency curves of the tuna fluctuate greatly with spacing, which is related to the position of the manta ray wake field where the tuna are located.

Числове моделювання поступальних і обертальних коливань рдтп у стапелі під час вогневих стендових випробувань

This article dwells on results of firing bench testing of the solid-propellant rocket engine (SPRE), fastened to the thrust-measuring assembly stand. It is shown that when engine enters the steady-state mode of operation, plane (forward and rotation) vibrations of the SPRE can take place in the assembly stand due to the sudden pattern of thrust generation and displacement of the center of mass of the vibrating system from the engine axis. These vibrations distort measured values of engine thrust and pattern of its change versus time. The purpose of this work is to simulate the oscillating processes of the engine atop the assembly stand to single out in the distorted values of the measured thrust the components related to the processes in the engine and components, which are introduced into the thrust measurement by the oscillating processes in the system “assembly stand – engine”. Model of vibrating system is suggested, which consists of two rigidly connected bodies, containing elastic links, enabling forward and rotary motion and limited by the rigidity of the links. Mathematical model of the vibrating system is developed. Internal forces and moments acting in oscillatory system are defined. Method of numerical simulation of plane vibrations within the limits of the developed model is suggested. Plane vibrating motion and elastic force curve (curve based on force sensor readings) were simulated in thrust-measuring system for different cases of thrust curve and values of vibrating system parameters. Resonance condition was simulated and mutual influence of elastic parametrical link between forward and rotary vibrations was established. Impact of thrust-measuring system rigidity on peak values of force sensor readings was found out. Elastic force vibrations in thrust-measuring system with vibrating system parameters were simulated including variant of thrust change versus time, implemented during firing bench tests of one of the SPRE. It is shown that registered simulation results recreate thrust measurement results in pattern and values obtained by the force sensor during the firing bench tests, and owing to this, it was concluded that oscillating process parameters, assumed in the model, meet the actual ones. It is concluded that simulation provides objective interpretation of the thrust curve, reliable and comprehensive analysis of engine run during firing bench tests, more detailed and exact design of the assembly stand. Key words: vibrating system, plane vibrations, forward vibrations, rotary vibrations, resonance, thrust measurement.

Vertical Axis Wind Turbine Layout Optimization

Vertical Axis Wind Turbines (VAWTs) are not mature enough yet for offshore wind farms, but they offer benefits compared to conventional Horizontal Axis Wind Turbines (HAWTs). Higher power densities, reduced wakes, lower center of mass, and different power and thrust curves make VAWTs an interesting option to complement existing wind farms. The optimization of wind farm layouts—finding the optimal positions of wind turbines in a park—has proven crucial to extract more energy from conventional wind farms. In this study, we build an optimizer for VAWTs that can consider arbitrarily shaped layouts as well as obstacles in the area. We adapt a recent model for the wakes of VAWTs considering a Troposkien design. We can then model and optimize a large VAWT park in a real wind scenario and assess for the first time its performance operating Troposkien VAWTs. In addition, we present a novel model for wind farm optimization that considers the clockwise and counterclockwise rotation of turbines. This optimization exploits the asymmetric wakes of VAWTs, thus increasing the total energy production. We benchmark our optimization on realistic instances and compare VAWTs and HAWTs wind farm layouts, showing that VAWTs can achieve higher density and power production than HAWTs in the same area. Finally, the wake loss reduction is compared to the literature.

Analysis of 5 MW Blade Two-Way Fluid-Structure Interaction Characteristics

A CFD-CSD coupled method was employed to establish an aeroelastic model of the NREL 5 MW wind turbine. The two-way fluid-structure interaction (FSI) simulation was carried out for this aeroelastic model. The response curves of blade tip flapwise, edgewise, and torsional deformation under normal operating conditions was obtained. The results show that the blade deformation shows a trend of increasing and then decreasing from the cut-in wind speed to the cut-out wind speed with the rise in wind speed. The maximum deformation appears in the vicinity of rated working conditions. Furthermore, the difference in aerodynamic performance between two-way FSI and one-way FSI has been studied to reveal the influence of the aeroelastic effect on performance. The two-way FSI that considers the blade deformation causes significant periodic fluctuations in the torque and thrust curves, with a maximum deviation of 3.75% in the average torque at 20 m/s. Therefore, the two-way FSI that introduces the aeroelastic effect can predict the aerodynamic performance more accurately.

CONVERGENT AND DIVERGENT ANGLES OF A SOLID-FUEL ROCKET NOZZLE AND ITS INFLUENCES ON THE MOTOR’S THRUST CURVE

The main goal of this work is to investigate how the angles of a convergent-divergent rocket nozzle influence the thrust curve of a solid-propulsion rocket. The work has been conducted within an academic rocketry team. As there is not clear reasoning on how to define these angles, the present research provides insights on how these geometrical parameters influence the performance of a rocket motor. A 2D-axisymmetric CFD domain is considered, comprising the fluid domain inside and outside the nozzle, to give room for the shock waves to happen and also accommodate the flow. The study comprises a baseline geometry and twelve modified designs, varying the convergent and the divergent angles of the nozzle. Since the convergent diameter must match the chamber diameter, it is fixed. For the divergent diameter, there is no such restriction; therefore, there are two possibilities: a divergent section with the same divergent diameter or with the same length as the baseline. The benchmark thrust curve is generated with a MATLAB code based on solid-fuel modeling and the De Laval theory. The curve is divided into six steady-state simulations, using boundary conditions of mass flow, pressure and temperature at the inlet and pressure and temperature at the outlet. The baseline geometry is simulated in Ansys Fluent and normalized by the MATLAB benchmark. A mesh study selects which mesh and turbulence model to use based on this normalization. The modified geometries are then compared to the baseline. The main quantity of interest is the thrust but quantities such as static pressure and average velocity at the nozzle exit aid the understanding of the changes in thrust.

Investigation Effect of Magnet Skew on Thrust Force in Linear Brushless Direct Current Motor with FEM

This study is concerned with the reduction of ripple in the thrust force produced in a linear Brushless Direct Current Motor (BLDC). To reduce the ripples in the generated thrust force, different methods such as structural solutions are applied both in the control part and in the production phase of the motor. In this study, skew application, which is one of the mechanical methods, is proposed. For this reason, the changes in the thrust force of a BLDC motor with a surface magnet-placed translator are investigated by applying different levels of skew to the magnets. First, a 3D solid model of the motor was created. A pole on the translator of the linear BLDC motor is composed of 3 equal magnet groups. For each skew level, the magnets were shifted 3 mm independently of each other and the thrust force values were examined. For this process, a 3D magnetostatic analysis of the linear BLDC motor was performed. The results obtained show that the skewing process applied to the magnets reduces the ripples in the thrust curve up to a certain point, after which no significant improvement in the ripple is observed, while the average force value decreases significantly.

Simulating Rocket Trajectory Using JSBSim and Optimal Thrust Profile for maximizing altitude of sounding rocket

Solid rocket boosters are commonly used for launching sounding rockets due to their simplicity and power-ness. The shape and geometry of the propellant grain determine the thrust-time profile which has a significant effect on rocket performance. In practical application, the thrust profile has three typical curves; regressive, neutral, and progressive. A great deal of studies has been focused on optimizing the trajectory based on various state variables in which the profile of the thrust-time curve was not among those variables. In this research, design variables were the thrust profile, the object function was maximizing the altitude subjected to constraints of a fixed amount of fuel. The trajectory was found by solving the equations of motion. For comparison purposes, the trajectory was also found using JSBSim, an open-source flight dynamic simulator. In the final results of the optimization process, the input thrust-time curve was evolved into an unusual shape, the letter “V” shaped. In this type of profile, the thrust curve starts regressively until reaches zero value at the middle of the burning time and then continues progressively until the end. This behavior can be satisfied only by two-stage boosters. Thus, these results show that two-stage boosters perform better than single-stage. The improvement is obtained by consuming the solid propellant more efficiently allowing fewer energy losses. This reason is added to the fact that two-stage boosters allow reducing the total masses due to the casste separation.

The Control of PMSM Motor to Drive Propeller in Ship Propulsion System

Electric propulsion has advantages such as high maneuverability, good safety and reliability, being able to operate optimally with a control system. It is a future green technology which is environmentally friendly. The application of electric propulsion for ship is that the propeller is driven by using electric motor by regulating speed and/or torque. in this research, an permanent magnet synchronous motor (PMSM) is used to drive propeller of ship propulsion. The controller of proportional integral (PI) scheme is proposed to drive electric motor. The method of Ziegler Nichols stability margin tuning rule algorithm is performed to search the controller parameters. The optimal working point of propeller is determined by the cross intersection between the propeller loading curve to the coefficient of thrust curve of open water test propeller. The speed from the result of propeller working point analysis is set as control input reference. Based on the results of simulation, the proposed control of electric propulsion using PMSM motor is able to achieve the reference of speed.

Experimental and numerical analysis of hovering multicopter performance in low-Reynolds number conditions

Unmanned Aircraft Systems (UAS) are state of the art in the aerospace industry and are involved in many operations. Although initially developed for military purposes, commercial applications of small-scale UAS, such as multicopters, are abundant today. Accurate engineering tools are required to assess the performance of these vehicles and optimize power consumption. The thrust and power curves of the rotors used by small-scale UAS are essential elements in designing efficient aircraft. The scarcity of experimental data and sufficiently accurate prediction models to evaluate rotor aerodynamic performance in the flight envelope are primary limitations in UAS science. In addition, for small-scale rotors at usual rotation rates, chord-based Reynolds numbers are typically smaller than 100,000, a flow regime in which performance tends to degrade. In this paper, experimental data on small-scale multicopter propulsion systems are presented and combined with a Computational Fluid Dynamics (CFD) model to describe the aerodynamics of these vehicles in low Reynolds numbers conditions. We use the STAR-CCM+ software to perform CFD simulations adopting both a dynamic-grid, time-accurate analysis and a static-grid, steady-state technique that solves the Navier-Stokes equations in a suitable framework. Comparing numerical simulation results on a conventional UAS propeller with related experimental data suggests that the proposed approach can correctly describe the thrust and torque coefficients in the range of Reynolds numbers characterizing the UAS flight envelope.

On the Use of Fluorine‐Containing Nano‐Aluminum Composite Particles to Tailor Composite Solid Rocket Propellants

AbstractThe burning rate of solid propellants is an important factor for optimizing rocket motors and improving performance. The enhanced burning rate can increase thrust and reduce a propulsion system‘s overall size and weight. In this study, a novel nano‐aluminum/THV composite additive was prepared and introduced into a solid ammonium perchlorate/polybutadiene composite solid rocket propellant to enhance its burning rate. The morphology of the composite particle additive and its effects on combustion were characterized. The use of small quantities (<15 wt.%) of the additive resulted in a burning rate enhancement of up to 2.1 times that of the conventional coarse aluminized propellant with a specific impulse loss of only 3 seconds, and as much as 4.7 times enhancement with a predicted loss of 22 seconds in theoretical specific impulse. Some of this loss may be recovered by the improved combustion efficiency in smaller rocket motors because the additive was shown to significantly reduce the aluminum agglomeration at the propellant burning surface and reduce the size of reaction products which may reduce two‐phase flow losses. The additive also provides wide burning rate tailorability, favorable for motor, grain, and thrust curve design. The burning rate enhancement mechanism is thought to be a physical cratering mechanism governed by the burning rate disparity between the binder/oxidizer system and the nano‐aluminum/fluoropolymer additive and not a chemical catalytic effect.

The attitude control optimization of small rocket

In this article, an optimization method for attitude calculation and vector control of small rocket is proposed, which reduces the performance requirements and costs of gyroscopes. Dynamic model parameters such as engine thrust curve and rocket body moment of inertia are added to the traditional filtering and control algorithm, which can reduce the hardware performance requirements of sensors and the cost of rocket control system. This method has achieved good results in the test, and is of great significance for the promotion of small rockets.

Study of Model Uncertainties Influence on the Impact Point Dispersion for a Gasodynamicaly Controlled Projectile.

The article presents the analysis of the impact point dispersion reduction using lateral correction thrusters. Two types of control algorithms are used and four sources of uncertainties are taken into account: aerodynamic parameters, thrust curve, initial conditions and IMU errors. The Monte Carlo approach was used for simulations and Circular Error Probable was used as a measure of dispersion. Generic rocket mathematical and simulation model was created in MATLAB/Simulink 2020b environment. Results show that the use of control algorithms greatly reduces the impact point dispersion.

Optimal propeller blade design, computation, manufacturing and experimental testing

PurposeModern unmanned air vehicles (UAVs) are usually equipped with rotors connected to electric motors that enable them to hover and fly in all directions. The purpose of the paper is to design optimal composite rotor blades for such small UAVs and investigate their aerodynamic performances both computationally and experimentally.Design/methodology/approachArtificial intelligence method (genetic algorithm) is used to optimize the blade airfoil described by six input parameters. Furthermore, different computational methods, e.g. vortex methods and computational fluid dynamics, blade element momentum theory and finite element method, are used to predict the aerodynamic performances of the optimized airfoil and complete rotor as well the structural behaviour of the blade, respectively. Finally, composite blade is manufactured and the rotor performance is also determined experimentally by thrust and torque measurements.FindingsComplete process of blade design (including geometry definition and optimization, estimation of aerodynamic performances, structural analysis and blade manufacturing) is conducted and explained in detail. The correspondence between computed and measured thrust and torque curves of the optimal rotor is satisfactory (differences mostly remain below 15%), which validates and justifies the used design approach formulated specifically for low-cost, small-scale propeller blades. Furthermore, the proposed techniques can easily be applied to any kind of rotating lifting surfaces including helicopter or wind turbine blades.Originality/valueBlade design methodology is simplified, shortened and made more flexible thus enabling the fast and economic production of propeller blades optimized for specific working conditions.

Wind Farm Yield and Lifetime Optimization by Smart Steering of Wakes

Wake steering has an impact on both the wind farm energy yield and turbine loads. We evaluate these effects based on yaw-corrected power and thrust curves and tabulated turbine load simulation results. In a first step, wind direction and wind speed dependent yaw angles were determined by maximization of the wind farm power for an example wind farm. Secondly, the optimizations were repeated for the objective of minimal flapwise blade fatigue loads. The results were then combined such that the power optimized yaw angles dominate the partial load region while the load optimized results were chosen for higher wind speeds. We find that this combination increases the annual energy production in an example wind rose while simultaneously reducing the lifetime damage equivalent loads. The analysis was repeated including wind direction uncertainty into the optimization. This significantly reduced the benefit of wake steering on AEP but caused only a mild decrease of the overall load reduction.

Hydrokinetic turbine design through performance prediction and hybrid metaheuristic multi-objective optimization

Small wind turbines (SWT) and hydrokinetic turbines (HT) are affordable ways to distribute power generation from renewable resources. In order to better harness such available sources and to design future equipment as efficient as possible, this paper aims to develop a layout optimization. Firstly, the Blade Element Momentum (BEM) method is applied to validate the aerodynamic models from literature with experimental data. It intends to replicate turbine operation and its performance. The power and thrust curves could be well-predicted according to tip-speed ratio (TSR) variation. Secondly, meta-heuristic algorithms based on natural behaviour are used to find the best hydrokinetic turbine design in a hypothetical environment subjected to a single person's electricity demand. Later, an analysis of a higher power supply will also be made. The optimization was carried out concerning power and blade inertia, and the layout parameters used as input were the rotor diameter, the number of blades, and the rotational speed. Cavitation effect was taking into account and tried to be avoided at chord calculation. The most efficient algorithm could find a turbine with a power coefficient 18% lower than the Betz Limit.

Forced Motion CFD Simulation and Load Refinement Evaluation of Floating Vertical-Axis Tidal Current Turbines

Abstract Simulation of the hydrodynamic performance of a floating current turbine in a combined wave and flow environment is important. In this paper, ANSYS-CFX software is used to analyse the hydrodynamic performance of a vertical-axis turbine with various influence factors such as tip speed ratio, pitching frequency and amplitude. Time-varying curves for thrust and lateral forces are fitted with the least squares method; the added mass and damping coefficients are refined to analyse the influence of the former factors. The simulation results demonstrate that, compared with non-pitching and rotating turbines under constant inflow, the time-varying load of rotating turbines with pitching exhibits an additional fluctuation. The pitching motion of the turbine has a positive effect on the power output. The fluctuation amplitudes of thrust and lateral force envelope curves have a positive correlation with the frequency and amplitude of the pitching motion and tip speed ratio, which is harmful to the turbine’s structural strength. The mean values of the forces are slightly affected by pitching frequencies and amplitudes, but positively proportional to the tip speed ratio of the turbine. Based upon the least squares method, the thrust and lateral force coefficients can be divided into three components, uniform load coefficient, added mass and damping coefficients, the middle one being significantly smaller than the other two. Damping force plays a more important role in the fluctuation of loads induced by pitching motion. These results can facilitate study of the motion response of floating vertical-axis tidal current turbine systems in waves.