Thrust Conditions Research Articles

A Green's Function Wind Turbine Induction Model That Incorporates Complex Inflow Conditions

ABSTRACTIn this work, we develop a new analytical turbine induction model that can incorporate complex inflow conditions including cases where the wind velocity and temperature profiles can vary as functions of height. This induction model is derived from the linearized Navier–Stokes and leads to a second‐order ODE that can be solved using a Green's function formulation. The corresponding Green's function for several configurations are found including the infinite domain, semi‐infinite domain with ground plane, and a power law velocity inflow profile. The results of this approach are then compared with simulations of the turbine induction field using the AMR‐Wind CFD solver with a uniformly loaded actuator disk model. These comparisons show that the Green's function approach captures the centerline blockage, three‐dimensional blockage flow field, and streamwise velocity slow down, with very good agreement for lower thrust conditions and at larger distances away from rotor disk. The effects of shear on the turbine blockage were also compared using a power law inflow profile, and we show that this approach matches the CFD predictions for the cases considered.

Acoustic-based diagnostics for UAV propeller damage using HNR and Gaussian Naive Bayes

PurposeThe purpose of this study is to determine propeller damage based on acoustic recordings taken from unmanned aerial vehicle (UAV) propellers operated at different thrust conditions on a test bench. Propeller damage is especially critical for fixed-wing UAVs to sustain a safe flight. The acoustic characteristics of the propeller vary with different propeller damages.Design/methodology/approachFor the research, feature extraction methods and machine learning techniques were used during damage detection from propeller acoustic data. First of all, sound recordings were obtained by operating five different damaged propellers and undamaged propellers under three different thrusts. Afterwards, the harmonic-to-noise ratio (HNR) feature extraction technique was applied to these audio recordings. Finally, model training and validation were performed by applying the Gaussian Naive Bayes machine learning technique to create a diagnostic approach.FindingsA high recall value of 96.19% was obtained in the performance results of the model trained according to damaged and undamaged propeller acoustic data. The precision value was 73.92% as moderate. The overall accuracy value of the model, which can be considered as general performance, was obtained as 81.24%. The F1 score has been found as 83.76% which provides a balanced measure of the model’s precision and recall values.Practical implicationsThis study include provides solid method to diagnose UAV propeller damage using acoustic data obtain from the microphone and allows identification of differently damaged propellers. Using that, the risk of in-flight failures can be reduced and maintenance costs can be lowered with addressing the occurred problems with UAV propeller before they worsen.Originality/valueThis study introduces a novel method to diagnose damaged UAV propellers using the HNR feature extraction technique and Gaussian Naive Bayes classification method. The study is a pioneer in the use of HNR and the Gaussian Naive Bayes and demonstrates its effectiveness in augmenting UAV safety by means of propeller damages. Furthermore, this approach contributes to UAV operational reliability by bridging the acoustic signal processing and machine learning.

Benchmarking of Aerodynamic Models for Isolated Propellers Operating at Positive and Negative Thrust

Operating a conventional propeller at negative thrust results in the operation of positively cambered blade sections at negative angles of attack, leading to flow separation. Consequently, accurately simulating the aerodynamics of propellers operating at negative thrust poses a greater challenge than at positive thrust. This study offers a comprehensive assessment of the aerodynamic modeling capabilities of numerical methods, spanning low to high fidelity, for computing propeller performance across both positive and negative thrust regimes. Low-fidelity methods, namely, blade-element momentum and lifting line theories, effectively predict propeller performance trends at positive thrust. However, they fail to capture trends at negative thrust beyond the maximum power output point due to the neglect of three-dimensional flow effects. Both steady and unsteady Reynolds-averaged Navier–Stokes (RANS) simulations with y+<1 perform well across both positive and negative thrust conditions, with errors below 2% for both thrust and power magnitudes near the maximum power output point. Lattice-Boltzmann very-large-eddy simulations (LB-VLESs) with y+≤10 exhibit excellent agreement with experimental data with less than 1% error near the maximum power output point but with significant computational costs. Conversely, LB-VLESs with y+≥15 offer a more economical approach to capture general trends with the computational cost of the same order as unsteady RANS. However, wall models introduce errors in modeling flow separation, leading to a 16% overestimation of power magnitude near the maximum power output point. The results highlight the necessity of using tools with increased fidelity levels when considering propeller operation at negative thrust compared to the conventional positive thrust regime.

A numerical study on the influence of multiple nozzles on the infrared radiation signatures of liquid rocket exhaust plumes

A numerical study was conducted to examine the relationship between the infrared radiation characteristics of liquid rocket engine exhaust plumes under the same thrust conditions and the number and expansion degree of nozzles. This study used the Reynolds-averaged computational fluid dynamics method to simulate the flow field of multiple nozzles. A single-line group combined with the G-C approximation was used to calculate the molecular spectral properties, and a three-dimensional radiation transfer calculation model was established based on the line-of-sight method. The infrared radiation characteristics of the exhaust plume were calculated for single, double, three, and four nozzles. The radiation intensity of two typical bands, 2.7 μm and 4.3 μm, was studied, including spectrum, intensity, and radiation intensity distribution. The results show that the integrated infrared radiation intensity of the double-nozzle plume is 51.36 % lower than the average of the other three nozzle configurations under the over-highly under-expansion state. The radiation difference of the double nozzle reaches up to 38.3 % at different detection angles, whereas the differences between the three and four nozzles are below 10.5 % and 6.1 %, respectively, indicating that the radiation difference at each detection angle gradually decreases with the increase in the number of nozzles.

Assessing the particulate matter emission reduction characteristics of small turbofan engine fueled with 100 % HEFA sustainable aviation fuel

With the continuous increase in global air transportation, the impact of ultrafine particulate matter (PM) emissions from aviation on human health and environmental pollution is becoming increasingly severe. In addition to carbon reduction throughout the lifecycle, Sustainable Aviation Fuels (SAF) also represent a significant pathway for reducing PM emissions. However, due to issues such as airworthiness safety and adaptability, existing research has mostly focused on the emission performance of SAF when blended with traditional fuels at <50 %, leaving the emission characteristics of higher blending ratios to be explored. In this study, using measurement methods recommended by the International Civil Aviation Organization (ICAO), the PM emission reduction characteristics of small turbofan engines fueled with 100 % Hydroprocessed Esters and Fatty Acids (HEFA)-SAF were experimentally evaluated and compared with traditional fuels RP-3 and Diesel, while avoiding the interference of lubricant blending combustion. The results showed that the peak number concentration of particle size distribution (PSD), PM total number, as well as the number and mass concentration of non-volatile particulate matter (nvPM) decreased initially and then increased with rising thrust conditions. HEFA-SAF exhibits PSD with smaller diameters, and the Geometric Mean Diameter (GMD) ranges from 7.7 nm to 20.3 nm under all conditions. Both volatile particulates (vPM) and nvPM from HEFA-SAF are significantly reduced, with nvPM number emission index (EIn) being 92 % and 71 % lower than Diesel and RP-3, respectively. The nvPM mass emission index (EIm) also shows reductions of 96 % and 89 % compared to Diesel and RP-3. Microscopic characterization also indicated that using HEFA-SAF emitted fewer and smaller PMs. This study establishes a foundation for evaluating the effectiveness of 100 % SAF in reducing PM emissions within the aviation sector, and contributes to the airworthiness regulations development related to the use of SAF in a variety of application environments, alongside enhancing environmental protection measures.

Investigation on spray and flame stabilization of a LOX/methane swirl coaxial injector

Variable-thrust cryogenic propellant rocket engines are gaining significant research interest in space exploration. However, low-frequency unstable combustion is still a challenging scenario, especially in fuel-rich preburner and low-thrust operating conditions of deep variable thrust. To deeply understand the mechanism of low-frequency unstable combustion, chemiluminescence images of CH* and background light images of the spray were obtained synchronously by chemiluminescence imaging and laser background light imaging, respectively. Both the spray and flame stabilization of liquid oxygen/methane swirl coaxial injector were studied through the continuous regulation of liquid oxygen mass flow rate. The results showed that low-frequency unstable combustion occur in both the start-up stage and the throttled stage under the fuel-rich condition at a frequency of 39.1∼48.1 Hz and an amplitude of 30% of the average combustor pressure. It is found that the two-phase flow instability of liquid oxygen is likely to induce spray and flame instability, resulting in low-frequency unstable combustion. The dimension subcooling degree of liquid oxygen is an important factor affecting unstable combustion. When the dimensionless subcooling degree is larger than 0.7, the low-frequency unstable combustion is suppressed. On the other hand, as the mixing ratio decreases, the flame oscillation mode gradually transforms from the longitudinal oscillation mode to contraction/expansion mode. Flame filling up and flashback processes can be observed in both flame oscillation modes, and the entropy coupling mechanism of the oscillation mode is explained in detail. Furthermore, an oscillation period is determined to include four processes: propellants filling up and flame liftoff; heat release of the combustion products and entropy disturbance; acceleration of the entropy wave through the nozzle creating an acoustic disturbance; and flame flashback, in which the heat release time of combustion products and entropy disturbance is the longest.

Soot aerosols from commercial aviation engines are poor ice-nucleating particles at cirrus cloud temperatures

Abstract. Ice-nucleating particles catalyze ice formation in clouds, affecting climate through radiative forcing from aerosol–cloud interactions. Aviation directly emits particles into the upper troposphere where ice formation conditions are favorable. Previous studies have used proxies of aviation soot to estimate their ice nucleation activity; however, investigations with commercial aircraft soot from modern in-use aircraft engines have not been quantified. In this work, we sample aviation soot particles at ground level from different commercial aircraft engines to test their ice nucleation ability at temperatures ≤228 K as a function of engine thrust and soot particle size. Additionally, soot particles were catalytically stripped to reveal the impact of mixing state on their ice nucleation ability. Particle physical and chemical properties were further characterized and related to the ice nucleation properties. The results show that aviation soot nucleates ice at or above relative humidity conditions required for homogeneous freezing of solution droplets (RHhom). We attribute this to a mesopore paucity inhibiting pore condensation and the sulfur content which suppresses freezing. Only large soot aggregates (400 nm) emitted under 30 %–100 % thrust conditions for a subset of engines (2 out of 10) nucleate ice via pore condensation and freezing. For those specific engines, the presence of hydrophilic chemical groups facilitates the nucleation. Aviation soot emitted at thrust ≥ 100 % (sea level thrust) nucleates ice at or above RHhom. Overall, our results suggest that aviation soot will not contribute to natural cirrus formation and can be used in models to update impacts of soot–cirrus clouds.

Isolated propeller aeroacoustics at positive and negative thrust

Using propellers in negative thrust conditions can potentially result in many benefits, such as a steeper descent, a reduced landing run, reduced community noise, energy regeneration, etc. However, the aerodynamics and aeroacoustics of propellers in this regime are not well understood. This paper presents an aeroacoustic analysis of an isolated propeller operating in both positive and negative thrust conditions, using scale-resolved lattice-Boltzmann very large eddy simulations and the Ffowcs Williams & Hawkings analogy. The propeller was operated at a constant tip Mach number so that any differences in tonal noise between positive and negative thrust conditions were due to changes in blade loading. Results showed that the flow separation around the blades in the negative thrust case led to a 2 to 6 times higher standard deviation in integrated thrust compared to the positive thrust case. The blade loading in the negative thrust case shows the amplitude of fluctuations up to 18% for inboard sections and up to 30% near the blade tip compared to the time-averaged loads. The noise in the propeller plane is 10 dB higher in the positive thrust regime than in the negative thrust regime at a given absolute thrust level of |TC|=0.08. The lower noise at negative thrust is caused by two factors: the lower magnitude of the negative torque compared to the positive torque at a given thrust level and the shift of the blade loading inboard in the negative thrust condition due to the stall of the blade tip. Along the propeller axis, the negative thrust regime has 13-15 dB higher noise because of the increased broadband noise generated by the flow separation. In the negative thrust case, the noise along the propeller axis (89 dB) and propeller plane (92 dB) are comparable. However, this is not the case for the propulsive case. The comparison of noise in the vicinity of the propeller plane showed that using the propellers in negative thrust conditions allows for a steeper and quieter descent compared to a conventional descent; as long as the magnitude of the negative torque produced is equal to or less than the torque required to operate the propeller in a conventional landing.

Numerical analysis on thermal environment of reusable launch vehicle during supersonic retropropulsion

Developing reusable launch vehicles (RLV) is an effective way to significantly reduce space transportation costs. However, in the return stage of the vehicle, especially the supersonic retropropulsion (SRP), the first stage is partially submerged in the hot exhaust plume and faces severe convective heating at the base plate and sidewalls. As a rule of thumb, the layout of nozzles at the rocket base significantly affects the heat load. In order to evaluate the influence of heat load under different nozzle configurations during SRP (33 km–22 km), the thermal environment of RLV was studied through numerical investigation for three typical nozzle configurations. Using Reynolds-averaged Navier–Stokes equations (RANS)-based computational methods and the k−ω SST turbulence model, the flowfield is characterized at different trajectory points during retropropulsion. Results showed that the high heat flux is mainly concentrated in the baseplate's center area and the sidewall's near base area during SRP. In general, activating engines in the radial position is beneficial for the thermal protection system of a reusable launch vehicle while the thrust is identical. Base heating primarily results from high-temperature counterflows due to plume interactions, while sidewall heating is predominantly a result of high-temperature recirculation zones generated by plume-induced flow separation. During the supersonic retropropulsion phase, the 3-nozzle-180°, a non-closed nozzle configuration, has significantly lower heat loads on the baseplate and the sidewall than that of the 4-nozzle-90° and the 3-nozzle-120°. In addition, reducing the number of engines is also an effective solution under the same conditions of thrust. Studying the layout of the working engine without changing the original layout has important guiding significance for improving the reusability and safety factor of the RLV.

Aeroacoustic measurements of a contra-rotating UAV vehicle

The aerodynamic sound linked to the increasing presence of Unmanned Aerial Vehicles (UAVs) is becoming a societal concern. Assessing the aeroacoustics of these vehicles is of utmost importance, as it enables the evaluation and mitigation of the associated noise emissions. An experimental wind-tunnel investigation is carried out with an octo-quad multi-rotor model UAV with 4 sets of contra-rotating propellers, representative of a heavy-lifting drone, to assess the acoustic emissions of the vehicle under different flow and thrust conditions. The experiments are performed in the Open Jet Facility of the Delft University of Technology. The acoustic measurements from several microphones are combined to create the noise signature of the UAV, while the data from a balance are processed to compute the thrust. The results of this research demonstrate that it is possible to reduce the noise emissions of the drone by varying the operating input between the fore and aft motors. In particular, an attenuation in the overall sound pressure level of 5 to 8 dBA can be achieved if the RPM of the fore motors is decreased while that of the aft motors is increased.

Effects of number of blades on propeller noise

This paper presents the effect of the number of blades on the aeroacoustic characteristics and aerodynamic performance of propellers utilized in urban air mobility vehicles through an extensive experimental study. A detailed parametric study is conducted for two, three, and five-bladed propellers. Investigations are carried out under static thrust conditions and incoming axial flow velocities for various rotational speeds. The spectra and directivity of the far-field noise are studied in detail for broadband and tonal components. Results show that two-bladed propellers produce higher tonal noise levels than other blade numbers for the same tip speed, while five-bladed propellers produce the highest broadband noise levels. The highest level of noise radiation is noted in the upstream and downstream directions for broadband noise, whereas tonal noise is radiated mainly in the plane of rotation. Results also indicate that high-frequency broadband humps are observed for higher advance ratios, likely caused by the formation of laminar separation bubbles, and that amplitude increases with blade numbers. The results of this study provide valuable insight for further investigations of propeller noise and aerodynamic performance.

Investigation on interfacial bonding strength between aluminum hub and CFRP bonded joints exposed to accelerated aging conditions

Marine propellers are frequently exposed to the corrosive effects of seawater, which can significantly reduce their performance and durability. As a result, high corrosion-resistant materials are used in the fabrication of the propellers. Fiber-reinforced polymers (FRPs) have recently taken over as the material of choice when it comes to creating corrosion-resistant structure. To get the desired mechanical properties and performance, it is necessary to combine FRP composites with other materials, such as steel or aluminum. The present work deals with evaluating the bond strength between Aluminum hub and carbon fiber reinforced polymer (CFRP) propeller blade profile. Araldite 2011 adhesive was used to establish the bond between the aluminum hub and CFRP propeller blade profile. A universal testing machine(UTM) was used to evaluate the bond strength of CFRP propeller blade profile-Al hub bonded joint specimens. The Al hub and CFRP propeller blade profile were subjected to axial thrust conditions. The surface interaction values obtained from the experiments were given as input data in Finite Element (FE)-model for complex geometry. The von-Mises stress criterion was used to assess the bond strength between Al hub and CFRP blade profile. In addition, bonded joint specimens were also subjected to cyclic aging at intervals of 0, 30, 60, and 90 days, respectively. The cyclic aged specimens were mechanically characterized using UTM. The Fourier transform infrared (FTIR)spectrum was used to analyze the aging behavior of adhesive (Araldite 2011), and the surface of the fractured specimens was analyzed using scanning electron microscopy (SEM). The extended aging period affects the Al hub/adhesive interface in bonded joints, leading to lower load joint failure.

Noise Reduction on a Model Helicopter Rotor Using Dielectric Barrier Discharge Plasma Actuators

Noise reduction was studied on a model helicopter rotor using pulsed dielectric barrier discharge (DBD) plasma actuators mounted at the blades’ leading edges. The evaluation was performed in a fully anechoic chamber, where thrust and torque were measured concurrently with the acoustic signature using an array of 15 microphones. Acoustic measurements were made for both baseline and actuated cases at a fixed collective pitch angle under conditions of constant thrust. Actuation produced broadband and tonal noise reductions of up to 8 and 3 dB, respectively, while simultaneously increasing the rotor figure of merit by 25%. Broadband noise reductions were due to control of the otherwise separated boundary layer, resulting in smaller and weaker turbulent eddies in the wake and the tip-vortex and, therefore, smaller turbulent surface pressure fluctuations. Noise reduction directivity associated with the blade passing frequency of up to 3 dB was consistent with rotational noise theory. At most of the observer angles, both the plasma pulsation and ionization frequencies were not visible in the spectra above the motor self-noise signature. Peaks in the second harmonic were observed at specific observer angles and were assumed to be due to the geometric mounting of the actuator and amplification of the pulsations in the laminar separation bubble.

Experimental investigation on a side-by-side twin rotor system in pusher configuration

Growing interest in electric propulsion, together with the increased deployment of unmanned aerial vehicles, results in the consequent need for a clear understanding of the physical phenomena under propeller interactions which represent a primary noise source in multi-rotor configurations. To this purpose, the effect of rotor-to-rotor interactions of a twin pusher propeller configuration at static thrust conditions was experimentally investigated through aerodynamic and aeroacoustic measurement campaigns. The propellers tested refer to the APC-8x45MR rotor with an 8 inches diameter. The aerodynamics and aeroacoustics of several configurations were investigated using PIV technique, Pitot tube acquisitions, and microphone measurements performed in an anechoic environment. The propeller speed was varied within a typical range in the applications for both co-rotating and counter-rotating layouts. To define critical relative positions, many tip-to-tip separation distances were considered highlighting the general effects. Owing to the deformation exhibited by the rotor wakes due to their proximity, the pressure and velocity signals were conditioned to inspect the driving mechanisms responsible for the noise emission. Results provide a deeper insight into the physics involved and show different types of interaction effects on the fluid-dynamic field as a function of the propeller position, allowing the identification of the main critical configurations.

Orbit Determination for All-Electric GEO Satellites Based on Space-Borne GNSS Measurements

Orbit accuracy of the transfer orbit and the mission orbit is the basis for the orbit control of all-electric-propulsion Geostationary Orbit (GEO) satellites. Global Navigation Satellite System (GNSS) simulation data are used to analyze the main factors affecting GEO satellite orbit prediction accuracy under the no-thrust condition, and an electric propulsion calibration algorithm is designed to analyze the orbit determination and prediction accuracy under the thrust condition. The calculation results show that the orbit determination accuracy of mission orbit and transfer orbit without thrust is better than 10 m using onboard GNSS technology. The calibration accuracy of electric thrust is about 10−9 m/s2 and 10−7 m/s2 with 40 h and 16 h arc length, respectively, using the satellite self-positioning data of 100 m accuracy to calibrate the electric thrust. If satellite self-positioning data accuracy is at the 10 m level, the electric thrust calibration accuracy can be improved by about one order of magnitude, and the 14-day prediction accuracy of the transfer orbit with thrust is better than 1 km.

Vibration characteristics of hard rock cutterhead under spatial distribution load

During the actual operation of the full-face tunnel boring machine (TBM), the vibration of the mainframe system is very strong, leading to the failure of key parts. Therefore, the vibration characteristics of TBM Cutter head under the maximum thrust condition are analyzed by ANSYS finite element software, and the effects of Cutter head panel thickness, Cutter head baseplate thickness, and support plate thickness on Cutter head vibration are analyzed. Subsequently, the optimal solution of the system is obtained by analyzing the data with orthogonal tests. It provides a reference for vibration reduction and parameter matching of Cutter head.

Optimization design in single wagon-wheel fuel grain of hybrid rocket motor

The grain design of hybrid rocket motor is a design of proper fuel grain geometry and flow adjustment scheme based on the total impulse, thrust, chamber pressure, length and outer diameter of combustion chamber. And the laws of various parameters in the working process of motor are obtained through the internal ballistic calculation. Based on the overall indicators of the upper stage motor of launch vehicles, the grain design process of single wagon-wheel and the internal ballistic calculation of adjusting the oxidizer flow according to the thrust feedback under the preset thrust condition are established. According to the indicators of power system, the constant thrust is F=11kN, the total impulse is I≥1100kN·s, the outer diameter is Dt≤400mm and the chamber length is L≤1000mm. Furthermore, the comparison and optimization design on star-shaped and single wagon-wheel grain are carried out. The oxidizer is 98% hydrogen peroxide (HP), the fuel is hydroxyl-terminated polybutadiene (HTPB) based fuel (including 58% Al), and the optimal oxygen-fuel ratio (O/Fopt) is 1.3. According to the theory of constant regression rate of the burning surface, the changes of the burning line length and channel area of the single wagon-wheel grain with the regression of the combustion surface are calculated. The results show that when the expansion ratio is 100 and average combustion chamber pressure is 5 MPa, the burning area of single wagon-wheel grain increases by 16.9% compared with the star-shaped grain, the O/F is reduced during motor operation, and the average specific impulse of the engine is increased by nearly 2%. In this paper, a typical uniform-thickness single wagon-wheel fuel grain is adopted. According to the optimization design, when the spokes number is 6, the average specific impulse of the motor is the largest. With increasing the spokes angle coefficient, increasing the height of the spokes, and reducing the angle of the spokes, the burning area is increased and the channel area is reduced, thereby the regression rate and fuel flow are increased and the O/F is reduced during the working process. Then the average specific impulse and overall performance are improved. This research provides a reference for single wagon-wheel fuel grain of hybrid rocket motor, calculation of interior ballistic performance under preset thrust, and flow adjustment by thrust feedback.

Comparison of computational methods for hydrodynamic performance prediction of oscillating marine propulsors

The biomimicry of fish fins has been suggested as an efficient and low-noise approach to propulsion for remotely operated and autonomous underwater vehicles. Propulsion of this type is achieved through the use of fin-like propulsors that undergo oscillatory motions. Two computational approaches of differing fidelity and computational space/time requirements have been used to calculate thrust and efficiency of oscillating marine propulsors in order to determine the region where each method is most appropriate for design applications. The higher fidelity and computational cost method is an unsteady Navier–Stokes approach. The lower fidelity and computational cost method is a lifting-surface potential flow method supplemented with strip theory to account for viscous effects. In comparison with two-dimensional experimental results, both methods were able to accurately capture magnitudes and trends in light to moderate thrust conditions (CT<0.7) assuming no dynamic stall occurs. Under these operating conditions, computational savings for three-dimensional analysis on the order of 5,000 processor-hours are achieved by using the lower fidelity method, making it the more appropriate choice for design applications. At high thrust conditions (CT>0.7) and in conditions where dynamic stall effects are prevalent (αmax>20∘, low Strouhal numbers), the higher fidelity method is required to achieve sufficient predictive accuracy.

Preliminary Experimental Characterization of a Microwave Discharge Cusped Field Thruster

The cusped field thruster has become a candidate thruster in next-generation space science missions due to its low complexity and potential long life over a wide range of thrust conditions. However, the reduction of propellant utilization and, as a result, the total performance degradation has emerged in works on cusped field thruster downscaling. In this work, a coaxial resonator is utilized to feed the microwave (MW) into the near-anode region of the cusped field thruster, which contributes to ionization at a relatively low mass flow rate. With a LaB6 thermionic emission cathode, the thruster can operate in two modes: MW excited mode and the MW-DC mixed mode. The results show that the thruster can operate with a minimum mass flow rate minimum of 0.004 mg/s and achieves a continuously adjustable thrust from 1.9 μN to 30.8 μN. The performance variation characteristics over the three control parameters (anode voltage, mass flow rate, and MW power) are considered. Additionally, a plume plasma diagnosis is performed with a Faraday probe and a retarding potential analyzer to analyze the discharge performance and plasma characteristics with different operating conditions.

유인드론용 생체모사 익형의 공력 및 소음특성에 대한 연구

In this paper, the experimental and numerical research on the aerodynamic and noise characteristics of a biomimetic airfoil is reported for the purpose of manned drone propeller design. Through the CFD analysis the aerodynamic performances for four types of airfoil are compared in order to search for the most desirable airfoil platform for the manned drone, and the experiment for the fore-mentioned airfoils were performed to verify their aerodynamic and noise characteristics. The CFD and the experiments show that the eagle wing mimetic airfoil has the maximum lift coefficient of 25 % higher than the other standard airfoil. In the manned drone propeller model test, the eagle model results in the thrust performance of 28.3 % higher than the other standard model. The comparison of sound pressure levels at the same thrust condition shows that the eagle model produces the noise level of 1.9 dB<SUB>A</SUB>lower than that of the conventional NACA-based model. The biomimetic eagle-wing airfoil can be effectively applied to the manned drone system which requires both the high payload and the reliability.