Thruster Performance Research Articles

Unmanned Aircraft Systems Performance in a Climate-Controlled Laboratory

Despite many research studies focus on strategies to improve autopilot capabilities and bring artificial intelligence onboard Unmanned Aircraft Systems (UAS), there are still few experimental activities related to these vehicle performance under unconventional weather conditions. Air temperature and altitudes directly affect thrust and power coefficients of small scale propeller for UAS applications. Reynolds numbers are usually within the range 10,000 to 100,000 and important aerodynamic effects, such as the laminar separation bubbles, occur with a negative impact on propulsion performance. The development of autonomous UAS platforms to reduce pilot work-load and allow Beyond Visual Line of Sight (BVLOS) operations requires experimental data to validate capabilities of these innovative vehicles. High quality data are needed for a deep understanding of limitations and opportunities of UAS under unconventional flight conditions. The primary objective of this article is to present the characterization of a propeller and a quadrotor capabilities in a pressure-climate-controlled chamber. Mechanical and electrical data are measured with a dedicated test setup over a wide range of temperatures and altitudes. Test results are presented in terms of thrust and power coefficient trends. The experimental data shows low Reynolds numbers are responsible for degraded thrust performance. Moreover, details on brushless motor capabilities are also discussed considering different temperature and pressure conditions. The experimental data collected in the test campaign will be leveraged to improve UAS design, propulsion system modelling as well as to provide guidelines for safe UAS operations in extreme environments.

Control-oriented quasi-one dimensional modeling method for scramjet

Abstract The scramjet model used in the control system needs to consider both accuracy and real-time requirements. In this paper, a quasi-one dimensional component level model method for scramjet is proposed. Under the premise of meeting the real-time requirement, this modeling method has higher calculation accuracy, and can obtain higher thrust performance without exceeding the limits. In order to improve the calculation accuracy of the scramjet model, the boundary layer correction and the interaction between shock wave and boundary layer are considered in the inlet and isolator modeling process by using reference temperature method. For the scramjet compression components, the inlet and isolator models are simplified based on shock train theory to improve real-time performance. Meanwhile, the combustor model and nozzle model are established and the combustor model is established with the combination of equal area and isothermal based on temperature limitation. Considering the boundary layer correction, the accuracy of the inlet and isolator model is improved by 8.79 and 7.9% respectively. Compared with the equal area combustion mode, the combined combustion mode can get higher thrust. In the C + + simulation environment, the average calculation time of each state point is about 25 ms which meets the real-time requirements.

Study on static performance of gas-lubricated thrust bearing based on multi-microporous stainless steel plate

A new type of multi-microporous stainless steel plate has been developed, and it has a lot of interconnected micropores on its surface and inside. The test results show that the pore size ranges from 0.1 to 15 μm and has regular shape. It is found that the plate has good air permeability by gas permeation test. The porous aerostatic thrust bearing is prepared by using this material, and the test results show that the bearing has high static bearing capacity. In FLUENT, the static characteristics of the porous gas hydrostatic bearing are simulated, and the simulation result is highly consistent with the experimental data, which verifies the correctness of the simulation and provides convenience for the study of the static characteristics of the porous gas hydrostatic bearing. The multi-microporous stainless steel plate can be used in ultra-high speed and ultra-precision instruments such as air lubricated motorized spindle and air bearing guide rail.

Coupled plasma transport and electromagnetic wave simulation of an ECR thruster

An electron-cyclotron resonance thruster (ECRT) prototype is simulated numerically, using two coupled models: a hybrid particle-in-cell/fluid model for the integration of the plasma transport and a frequency-domain full-wave finite-element model for the computation of the fast electromagnetic (EM) fields. The quasi-stationary plasma response, fast EM fields, power deposition, particle and energy fluxes to the walls, and thruster performance figures at the nominal operating point are discussed, showing good agreement with the available experimental data. The ECRT plasma discharge contains multiple EM field propagation/evanescence regimes that depend on the plasma density and applied magnetic field that determine the flow and absorption of power in the device. The power absorption is found to be mainly driven by radial fast electric fields at the electron-cyclotron resonance region, and specifically close to the inner rod. Large cross-field electron temperature gradients are observed, with maxima close to the inner rod. This, in turn, results in large localized particle and energy fluxes to this component.

Automatically Controlled Frequency-Tunable rf Plasma Thruster: Ion Beam and Thrust Measurements

A fast and automatically controlled frequency-tunable radiofrequency (rf) system is installed in an rf plasma thruster consisting of a stepped-diameter insulator source tube wound by a single-turn loop antenna and a solenoid providing a magnetic nozzle, and immersed in vacuum. The frequency and the output power are controlled so as to minimize the reflection coefficient and to maintain the net power corresponding to the forward minus reflected powers at a constant level. The reproducibility of the impedance matching and the stability of the net rf power are assessed, showing the fast impedance matching within about 10 msec and the long and stable delivery of the rf power to the thruster. When increasing the rf power up to 500 W, discontinuous changes in the source plasma density, the imparted thrust, and the signal intensity of the ion beam downstream of the thruster are observed, indicating effects of the discharge mode on the thruster performance and the ion energy distribution.

Experimental investigation on current modes of ionic liquid electrospray from a coned porous emitter

The ionic liquid electrospray-based propulsion system is one of the most promising candidates for space micro-propulsion, which is in urgent need with the rapid development of micro/nano satellites. The current mode in the electrospray process directly dominates the performance of ionic liquid electric thruster. Hence, in order to study the general current modes of ionic liquid electrospray, a series of experiments have been conducted with a coned porous nickel emitter. With the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate as propellant, both the time-varying voltage-current curves and corresponding optical images of the electrospray process are obtained. Firstly, based on the voltage-current curves and optical images, the classification of current mode was discussed, which showed that the current is a result of basic-mode composition in time and space and the mode transition is dominated by the electric field strength. Secondly, the liquid flow at the tip of coned porous emitter was studied based on the images, which is found to be a combination of porous media flow and liquid film flow influenced by the electric field. The projected area of meniscus can be much larger than the pore size, which indicates that the emission can span several pores in our system. As the electric voltage increases, the size of meniscus decreases and three-site emission is optically captured, which explains the spatial composition of the current mode. Finally, the onset delay is calculated from the time-varying current curves. Based on the observation that the meniscus size is variable, an onset delay model is developed, whose prediction agrees well with the experimental results. Since a single emitter is a basic element for array porous emitters, this work is valuable to the design of efficient ionic liquid electric thruster.

A CFD Simulation on the Performance of Slotted Propeller Design for Various Airfoil Configurations

The usage of slots has gained renewed interest in aerospace, particularly on propeller design. Most of the works have focused on improving the aerodynamic performance and efficiency. Modern research on propeller design aims to design propellers with high thrust performance under low torque conditions without any weight penalty. Although research on slotted design has been done before, none has been done to understand its impact on different airfoils on the propeller blade. Thus, this study aims to provide extensive research on slotted propeller design with various airfoil of different properties such as high Reynolds number, low Reynolds number, symmetrical, asymmetrical high lift, and low drag. This work has been investigated using computational fluid dynamics method to predict propeller performance for a small-scale propeller. The slotted blade designs' performance is presented in terms of thrust coefficient, power coefficient, efficiency, and thrust to power ratio. Here, the slotted APC Slow Flyer propeller blade's performance has been investigated for diverse types of airfoils with the shape and position of the slot is fixed which is a square-shaped at 62.5% of the chord length. The flow simulations are performed through three-dimensional computational fluid dynamic software (ANSYS Fluent) to determine the thrust coefficient, power coefficient, efficiency, and thrust to power ratio measured in advancing flow conditions. Findings show that the slotted propeller design composed of symmetrical, high Reynolds number, high lift airfoils can benefit the most with slots' implementation. These improvements were 19.49%, 69.13%, 53.57% and 111.06% in terms of thrust, power, efficiency and trust to power ratio respectively.

Kinematic Analysis of Water Polo Player in the Vertical Thrust Performance to Determine the Force-Velocity and Power-Velocity Relationships in Water: A Preliminary Study.

Background: To date, studies on muscle force and power-velocity (F-v and P-v) relationships performed in water are absent. Aim: The goal of this study is to derive the F-v and P-v regression models of water polo players in water vertical thrust performance at increasing load. Methods: After use of a control object for direct linear transformation, displacement over the water and elapsed time was measured, by using a high-speed 2D-videoanalysis system, on 14 players involved in the study. Results: Intra-operator and player’s performance interclass correlation coefficient (ICC) reliability showed an excellent level of reproducibility for all kinematic and dynamic measurements considered in this study with a coefficient of variation (CV) of less than 4.5%. Results of this study have shown that an exponential force-velocity relationship seems to explain better the propulsive force exerted in the water in lifting increasing loads compared to the linear one, while the power and velocity have been shown to follow a second-order polynomial regression model. Conclusion: Given the accuracy of the video analysis, the high reliability and the specificity of the results, it is pointed out that video analysis can be a valid method to determine force-velocity and power-velocity curves in a specific environment to evaluate the neuromuscular profile of each water polo player.

Experimental Investigation of Detonation Propagation Modes and Thrust Performance in a Small Rotating Detonation Engine Using C2H4/O2 Propellant

A small rotating detonation engine (RDE) model and the corresponding experimental setup were constructed for the experimental investigation of the detonation propagation characteristics and thrust performance of a circular RDE. Experiments were conducted at a range of 0.3–2.5 equivalence ratio with a total mass flow rate of less than 180.0 g/s using a C2H4/O2 mixture. Irregularly unstable detonative combustion occurs immediately after the detonation initiation, which includes initiation, propagation, decaying, and the merging of detonation waves. Following this, periodically unsteady detonative combustion occurs in the circular channel, resulting in the stable operation of the RDE. During stable operation, two detonation waves are predominant, rotating along the wall at a speed lower than the Chapman–Jouguet (CJ) detonation speed. The characteristic velocity efficiency is approximately 73% on average. The low characteristic velocity efficiency is presumed to be caused by the unoptimized combustion channel and the poor mixing efficiency owing to the two-dimensional injector configuration. The effect of the RDE component design and the RDE flow field characteristics need to be further investigated for improving the performance of the RDE.

Low power thrust measurements of the water electrolysis Hall effect thruster

We propose that a Hall effect thruster could be modified to operate on the products of water electrolysis. Such a thruster would exploit the low cost and high storability of water while producing gaseous hydrogen and oxygen in-situ as they are required. By supplying the anode with oxygen and the cathode with hydrogen, the poisoning of the cathode is mitigated. The water electrolysis Hall effect thruster (WET-HET) has been designed to demonstrate this concept. The dimensions of the WET-HET have been optimized for oxygen operation using PlasmaSim, a zero-dimensional particle in cell code. We present the first direct thrust measurements of the WET-HET. A hanging pendulum style thrust balance is used to measure the thrust of the WET-HET while operating in the Boltzmann vacuum facility within the Imperial Plasma Propulsion Laboratory. For this test the beam was neutralized using a filament plasma bridge neutralizer operating on krypton. We find thrust, specific impulse, and thrust efficiency all increase linearly with power for values between 400 and 1050 W. Increasing the mass flow rate from 0.96 to 1.85 mg/s increases thrust at the expense of specific impulse. Changing mass flow rate was found to have little impact on the thrust efficiency over this range. An optimal radial magnetic flux density of 403 G at the exit plane is found. Further increases to the magnetic field beyond this point were found to decrease the thrust, specific impulse and thrust efficiency, whereas the discharge voltage increased monotonically with increasing magnetic field for a given input power. It was found that the experimental thruster performance was lower than the simulation results from PlasmaSim. However, the general trends in performance as a function of power and propellant mass flow rate were preserved. We attribute a portion of this discrepancy to the inability of the simulation to model the energy absorbed by the covalent bond of the oxygen molecule. For the powers and mass flow rates surveyed we measured thrust ranging from 4.52pm 0.18, to 8.45pm 0.18,mN, specific impulse between 324pm 12, and 593pm 12,s, and anode thrust efficiencies between 1.34pm 0.10, and 2.34pm 0.10,%.

Fish without Tail Fins-Exploring the Function of Tail Morphology of the First Vertebrates.

We use a series of hydrodynamic experiments on abstracted models to explore whether primitive vertebrates may have swum under various conditions without a clearly-differentiated tail fin. Cambrian vertebrates had post-anal stubby tails, some had single dorsal and ventral fins, but none had yet evolved a clearly differentiated caudal fin typical of post-Cambrian fishes, and must have relied on their long and flexible laterally-compressed bodies for locomotion, i.e., by bending their bodies side-to-side in order to propagate waves from head to tail. We approach this problem experimentally based on an abstracted model of Metaspriggina walcotti from the 506-million-year old Burgess Shale by using oscillating thin flexible plates while varying the tail fin geometry from rectangular to uniform, and finally to a no tail-fin condition. Despite a missing tail fin, this study supports the observation that the abstracted Metaspriggina model can generate a strong propulsive force in cruise conditions, both away from, and near the sea bed (in ground effect). However, when the abstracted Metaspriggina model moves in ground effect, a weaker performance is observed, indicating that Metaspriggina may not necessarily have been optimized for swimming near the sea bed. When considering acceleration from rest, we find that the Metaspriggina model's performance is not significantly different from other morphological models (abstracted truncate tail and abstracted heterocercal tail). Statistical analysis shows that morphological parameters, swimming modes, and ground effect all play significant roles in thrust performance. While the exact relationships of Cambrian vertebrates are still debated, as agnathans, they share some general characteristics with modern cyclostomes, in particular an elongate body akin to lampreys. Lampreys, as anguilliform swimmers, are considered to be some of the most efficient swimmers using a particular type of suction thrust induced by the traveling body wave as it travels from head to tail. Our current experiments suggest that Metaspriggina's ability in acceleration from rest, through possibly a similar type of suction thrust, which is defined as the ability to generate low pressure on upstream facing sections of the body, might have evolved early in response to increasing predator pressure during the Cambrian Explosion.

Electrohydrodynamic thrust with no combustion emissions and noises in a centimeter-scale point-to-grid configuration

Alternative propulsion systems are needed to overcome the combustion emissions and noises caused by the fossil-fuel combustion-based gas turbines and propeller-driven propulsion systems. The electrohydrodynamic (EHD) thrust produced by the corona induced ionic wind is an attractive choice because its generation needs no mechanical moving part and emits no combustion emissions and noises. In this investigation, the electrohydrodynamic thrust provided by the positive point-to-grid corona discharge at the centimeter scale is theoretically and experimentally analyzed. The previous one-dimensional theory is reviewed to understand the fundamental characteristics of the EHD thrust. The thrust performance of a 4.1 mg, centimeter-scale, laser-micromachined EHD thruster is experimentally quantified. The measured thrust reaches up to 0.68 mN, corresponding to a thrust density of 8.7 N/m2, a thrust-to-weight ratio of 17 and a thrust-to-power ratio of 2.1 N/kW.

CFD-Based Investigation on Effects of Orifice Length–Diameter Ratio for the Design of Hydrostatic Thrust Bearings

Orifice-restricted hydrostatic thrust bearings are broadly employed in ultra-precision machine tools, aerospace industries, and so forth. The orifice length–diameter ratio (OLDR) is one of the significant geometrical parameters of the orifice-restricted hydrostatic thrust bearing, which directly affects the performance of the bearing. To accurately guide the design of the hydrostatic thrust bearing, the effect of the OLDR on the performance of the hydrostatic thrust bearing needs to be thoroughly and scientifically investigated, especially for ultra-precision machine tools. In this paper, the influences of various OLDRs are comprehensively studied using the computational fluid dynamics (CFD) approach on the pressure pattern, velocity, turbulent intensity, and vortices, as well as the load capacity, stiffness, volume flow rate, and orifice flow resistance of the hydrostatic thrust bearing under identical operating conditions. The obtained results show that there are differences in performance behaviors of the hydrostatic thrust bearing caused by different OLDRs. Some new findings are obtained, particularly in the second-order small vortices which appear in the annular recesses with all OLDRs except that of 2, and the flow resistance does not always increase with increasing OLDRs. Finally, the proposed CFD approach is experimentally validated.

Impulse bit and ablation characteristics of double cylindrical pulsed plasma thruster

Previous studies have shown that the performance of coaxial pulsed plasma thrusters depends on the ratio of propellant surface area-to-cavity volume. In this work, a double cylindrical propellant was introduced to increase the operation ratio compared to coaxial propellants; the results demonstrated that the geometric parameter obtained by dividing the ratio by the hollow diameter greatly influences the impulse bit. Also, direct observations and mass shot measurements revealed a higher density of the ablation gas from the cylindrical part than from the hollow part.

Experimental Characterization of Nozzle Performance at Low Reynolds Numbers for Water Microthrusters

This study directly measures the performance of a thruster nozzle using water vapor as propellant in the Reynolds number below 1000. Because of its properties, water is suitable as a propellant for small satellites, often with a low-Reynolds-number flow using a micronozzle. The low Reynolds number of the flow and the phase changes in supersonic vapor flow should affect nozzle performance. It is essential to measure thrust performance and consider the flow dynamics inside the nozzle, but to date there have been few direct thrust measurements at low Reynolds numbers from 100 to 600 and different temperatures of the vapor from 290 to 400 K. In this study, nozzle performance is evaluated using two dimensionless numbers: the discharge coefficient and the specific impulse efficiency. The results presented here are specific to water vapor. The discharge coefficient remains almost the same under these conditions and higher than those of argon and nitrogen. The specific impulse efficiency depends on the degree of superheating above Reynolds numbers of about 250, but shows little dependence below Reynolds numbers of about 250 owing to the combined effects of viscosity and phase change.

Theoretical Analysis of Performance Parameters in Oscillating Plasma Thrusters

Conventional expressions and definitions describing performance of plasma thrusters, including the thrust, specific impulse, and the thruster efficiency, assume a steady-state plasma flow with a constant flow velocity. However, it is very common for these thrusters that the plasma exhibits unstable behavior resulting in time variations of the thrust and the exhaust velocity. For example, in Hall thrusters, the ionization instability leads to strong oscillations of the discharge current (so-called breathing oscillations), plasma density, ion energy, and as a result the ion flow. This paper revisits the formulation of the thrust and the thrust efficiency to account for time variations of the ion parameters, including the phase shift between the ion energy and the ion flow. For sinusoidal oscillations it was found that thrust can potentially change more than 20%. It is shown that, by modulating ion energy at specific amplitudes, thrust can be maximized in such regimes. Finally, an expression for the thruster efficiency of the modulating thruster is derived to show a mechanism for inefficiencies in such thrusters.

Influences of Magnetic Flux Density on Discharge Characteristics of Low-Power Hall Thruster

ABSTRACT The design of the magnetic field is crucial to the performance of the hall thruster. This paper investigates the effects of magnetic field on the discharge characteristics of the low-power hall thruster in the method of combining simulation and experiment. Based on a 40-mm-diameter hall thruster (LHT-40) operating with hundreds of Watts, a two-dimensional axisymmetric model is established in fluid method to investigate the mechanism, how the magnetic field influences the performance of the thruster, and the experiments are also carried out to investigate the performance effected by magnetic field. Both the numerical and the experimental results indicate that there is an optimal magnetic flux density in which the thruster could achieve a higher efficiency compared with other conditions. And in order to maintain its high efficiency, the line of magnetic-curve inflexion inside the discharge channel should coincide with the center line of the channel to decrease the interaction between the plasma and the wall. The LHT-40 could generate about 12.2 mN of thrust at an optimal efficiency of 27% when the maximum magnetic flux density along the center line of the channel is about 200 Gs.

Application of a Pulsating Voltage Drive to an Anode-Layer-Type Hall Thruster

Hall thrusters typically exhibit a discharge-current oscillation with a few tens of kilohertz, which negatively affects the power supply and induces electromagnetic interference (EMI). A pulsating boost chopper power supply (chopper PS), which applies a varying voltage to the Hall thrusters, was developed to shift the discharge-current frequency to an acceptable frequency because discharge-current oscillation is unpredictable and can emit EMI. In this study, a 1-kW anode-layer-type Hall thruster was driven with a chopper PS to evaluate the dependence of performance on the chopping frequency because past investigations tested the chopper PS with only magnetic-layer-type Hall thrusters. The experiments showed that the thruster using a conventional DC power supply induced discharge-current oscillation at 32 kHz (i.e., thruster-originated natural frequency). Meanwhile, the chopper-PS drive shifted the discharge-current frequency to the chopping frequency unless the chopping frequency was more than 52 kHz. Conversely, for a chopping frequency over 52 kHz, the dominant frequency of the discharge current returned to the thruster-originated natural frequency. Moreover, the thruster performance above the 40-kHz chopping frequency was comparable to that using a conventional DC power-supply drive. Furthermore, the chopper-PS drive successfully suppressed amplitudes of discharge-current oscillation and ion wall loss to the guard ring by 50%.

Influence of the Solidity and Blade Number on the Performance and Internal Flow of Ship Side Thrusters

Influence of the Solidity and Blade Number on the Performance and Internal Flow of Ship Side Thrusters

Influence of acceleration grid voltage and anode flow rate on the performance of ion thruster*

Influence of acceleration grid voltage and anode flow rate on the performance of ion thruster*