Propeller Aircraft Research Articles

Study on the Propeller Characteristics of a Vertical Takeoff and Landing Aircraft

The VTOL (Vertical Takeoff and Landing) aircraft are attractive because they combine the advantages of a helicopter and an airplane. It can hover, take off and land without a take-off strip like a helicopter and simultaneously fly forward at high speed as an aircraft. A notable example of such an aircraft is the Bell Boeing V22 Osprey, which utilizes tilt rotors to alter the aircraft's flight mode by rotating the rotors forward or upward. The Osprey's rotors can be likened to propellers/rotors, serving to generate thrust/lift. Thus, this work aims to explore the aerodynamic characteristics, explicitly focusing on the thrust-produced propeller of a UAV (Unmanned Air Vehicle) during the transition of VTOL from the helicopter to aircraft mode or vice versa, i.e., the effect of the propeller angle on the thrust produced in all three modes of flight viz, aircraft, transition and helicopter. To determine the aerodynamic characteristics of a propeller, an UAV propeller was selected and scanned using a 3D Scanner to get a propeller CAD model with actual twist distribution. Subsequently, computational fluid dynamics (CFD) analysis was conducted using the ANSYS Fluent software to predict the propeller's thrust. Parametric studies were conducted to check the propeller thrust for all three flight modes for different rpm and forward speeds. The simulated results were validated through comparisons with available analytical results. This comprehensive investigation sheds light on the propeller behavior for different flight modes, ultimately contributing to an enriched understanding of VTOL aircraft propeller characteristics.

Aerodynamic Investigation of Fixed - Pitch Aircraft Propeller

An investigation of fixed - pitch propeller aerodynamics is described in this paper. The impetus for the work was to identify the proposed propeller’s efficiency, thrust coefficient, power coefficient, and pressure contours. All computational analyses were performed using Computational Fluid Dynamics (CFD) software called Cradle scFLOW. During the simulation process, velocity was set to 60 knots (30.87 m/s) and the initial RPM (Revolution per Minute) was kept constant at 3100 to specify efficiency. Subsequently, the RPM value was varied to achieve thrust force. According to results, a thrust value of 1700N was achieved and propeller efficiency was found 0.79. Thrust value was then compared with the data obtained from experimental studies and the notable match was achieved. An increase in advance ratio was found to raise propeller efficiency at some point, and then reduction was observed in terms of efficiency due to thrust reduction. After these investigations, the obtained thrust force was compared with experimental data. The CFD results indicated a good agreement with the experimental results.

Study on Aerodynamic Performance of Propeller with Tip Winglet

Based on the Reynolds-averaged Navier-Stokes governing equations and the unstructured grid rotating/stationary sliding surface technology, this paper studies the aerodynamic layout and efficiency enhancement mechanism of the near-space propeller blade tip winglet configuration. First, the feasibility of the configuration is verified by comparing and analyzing different lift propeller layout schemes. Secondly, the aerodynamic layout design of the blade tip winglet propeller is studied by changing the winglet inclination angle and length parameter indicators. Finally, the ANSYS simulation analysis is used to calculate the influence of the winglet design on the propeller velocity vector distribution, blade pressure and propeller aerodynamic efficiency, and the performance influence law of the basic parameters is preliminarily established, and the overall design scheme of the new blade tip winglet propeller design is completed. The study shows that the blade tip winglet propeller layout is a reasonable and feasible technical approach to improve the aerodynamic efficiency in the near-space working environment, and it has a certain reference role in the development of new configuration propeller aircraft.

Methodical and algorithmic aspects of mathematical modeling of a screw aircraft power plant

The article describes the solution of a scientific problem that consists in expanding the functionality of the program “Calculation of the traction-economic and mass-specific characteristics of the power plant and aircraft motion parameters” through the introduction of additional algorithms and mathematical models for calculating the altitude-speed characteristics of screw aircraft power installations. At the same time, an internal calculation of the aircraft propeller thrust is used according to experimental aerodynamic coefficients, which makes it possible to increase the efficiency and reliability of complex theoretical studies of power plants of various types as part of aircraft at the stage of external design. A description is given of the developed algorithms: an algorithm for converting power on the output shaft of a gas turbine engine into thrust of an aircraft power plant; a mathematical model of a propeller that provides calculation of its thrust from experimental aerodynamic coefficients; an algorithm for determining the thrust of the power plant, taking into account the compressibility of the air and the interaction of the propeller and the elements of the airframe of the aircraft. Some features of the mathematical modeling of an aircraft propeller are revealed, in particular, the principle of propeller control by influencing the blade angle and rotational speed depending on the aircraft flight speed and a method for constructing the field of aerodynamic characteristics of an aircraft propeller in a wide range of blade angle and speed coefficient. In conclusion, the results of verification of the modified program are presented with an analysis of the obtained altitude-speed characteristics.

Short-term noise annoyance towards drones and other transportation noise sources: A laboratory study.

Noise from unmanned aerial vehicles, commonly referred to as "drones," will likely shape our acoustic environment in the near future. Yet, reactions of the population to this new noise source are still little explored. The objective of this study was to investigate short-term noise annoyance reactions to drones in a controlled laboratory experiment. Annoyance to (i) two quadcopters of different sizes in relation to common contemporary transportation noise sources (jet aircraft, propeller aircraft, helicopters, single car passbys), and (ii) different drone maneuvers (takeoff; landing; high, medium, and low flybys) flown at different speeds and elevations was systematically assessed. The results revealed that, at the same sound exposure level, drones are perceived as substantially more annoying than other airborne vehicles and passenger cars. Furthermore, for drone maneuvers, landings, and takeoffs are more annoying than flybys, as are maneuvers flown at low speed. Different loudness metrics (LAE, LDE, effective perceived noise level, psychoacoustic loudness level) accounted for drone noise annoyance ratings to an equal degree. An analysis of psychoacoustic parameters highlighted the significant link between drone noise annoyance and tonality, sharpness, and loudness level. The results suggest a different perception and an increased annoyance potential of drones, which will likely require specifically tailored legislation.

Technical Note: Analytical Estimate of Rotor Controls Required for a Propeller Wake Disturbance Rejection

During helicopter air-to-air refueling, the aircraft propeller’s jet can engage with the helicopter rotor. The impact on the helicopter rotor thrust and aerodynamic hub moments is solved analytically for the first time, based on blade element momentum theory. The collective and cyclic blade pitch controls needed for disturbance rejection are computed for a typical air-to-air refueling scenario. A propeller jet affecting the retreating side of the rotor requires much more pilot controls to retrim than an impingement on the advancing side.

Aircraft propeller erosion wear and aerodynamic characteristics

Aircraft propeller erosion wear and aerodynamic characteristics

Radar detectability of light aircraft micro‐Doppler modulation

AbstractThe critical role of specifying micro‐Doppler mode performance in the modelling and development of modern radar systems is investigated. The authors focus on the detection of micro‐Doppler modulation from light aircraft, analysing data from eight helicopters and nine propeller aircraft. With the growing need for accurate target classification in radar technology, incorporating micro‐Doppler detection metrics into radar performance specifications has become increasingly important. This research offers a novel approach to measuring the detectability of micro‐Doppler modulation relative to returns from the main fuselage. The investigation covers the impacts of various preprocessing techniques, polarisation, and aspect angle on detection capabilities. Findings reveal that, on average, micro‐Doppler modulation from propellers is detectable at distances between 50% and 100% of the range at which the fuselage is detected. For helicopters, this range decreases to between 30% and 80%. Additionally, the study introduces empirically derived statistical models designed to predict micro‐Doppler detection ranges in relation to fuselage returns, enhancing the predictability and specificity of radar system performance. This novel contribution presents a basis for improving radar system specifications, leading ultimately to more predictable and reliable light aircraft classification.

Off-design analysis of the inverted Brayton cycle engine

PurposeThe purpose of this study is to perform an off-design analysis of the inverted Brayton cycle engine.Design/methodology/approachThe off-design analysis equations of the inverted Brayton cycle engine were first derived in this study and the control parameters of the inverted Brayton cycle engine were first determined and investigated.FindingsIt is observed that by controlling the total temperature decrease in cooling section, it is possible to adapt the engine for low specific fuel consumption working conditions or high thrust working conditions. Specific fuel consumption is reduced by 27.1 % by stopping cooling in the cooling section and thrust is increased by 27.6 % by working with full load of the cooling section (500 K temperature decrease in cooling section). It is observed that thrust depending on the flight Mach number increases with an increase in flight Mach number and reaches a peak value at 5.21 flight Mach number and reduces by 80.8 % at 6 flight Mach number relative to the peak value. The specific fuel consumption increases rapidly as the Mach number increases, and the specific fuel consumption is 49.0 g/[kN.s] at Mach 1, reaches 70.4 g/[kN.s] at Mach 5 and increases to 412 g/[kN.s] at Mach 6. The specific fuel consumption increases from 68.1 to 73.0 g/(kN.s) and the thrust decreases from 16.5 to 13.3 kN as the total preburner exit temperature increases from 1,500 to 2,000 K. Specific fuel consumption decreases from 83.1 to 64.8 g/(kN.s) and thrust increases from 4.60 to 11.08 kN depending on afterburner exit total temperature increase from 1,800 to 2,500 K.Research limitations/implicationsThe cooling section reduces total temperature of the gas flow to lower values to increase the compressor total pressure ratio. The compressor increases the total pressure of the gas flow to the optimum total pressure ratios to increase the nozzle exit Mach number and gain more thrust. The afterburner increases the total temperature of the gas flow to increase the sound speed in the nozzle exit to increase thrust. The nozzle expands the gas flow to reduce the static pressure of the gas flow to near the optimum value, atmosphere pressure, to increase thrust and reduce specific fuel consumption.Practical implicationsHypersonic and supersonic air vehicles can use the current engine model for the its own propulsion systems.Social implicationsAfter first heavier than air flight, aero engines was designed for only used for aero vehicle. Internal combustion engines were used for propelled propeller aircraft at the first term of aircraft. However, propeller-propelled aircrafts are not sufficient to increase aircraft velocity to supersonic Mach numbers due to the shock losses of propeller, so the supersonic era was only introduced by revolution in propulsion systems with new concept. A jet engine was developed to be candidate for supersonic flight.Originality/valueOff-design analysis equations of an inverted Brayton cycle engine were first derived in this study. Furthermore, the control parameters of the inverted Brayton cycle engine were first determined and investigated in this paper.

Advanced acoustic simulation of aircraft test environments: integration of the direct field acoustic testing methodology

In aeroacoustic engineering, replicating real-world environments in a controlled setting presents significant opportunities for reduced flight testing but also comes with challenges when precisely simulating the flight environment. This paper introduces an innovative acoustic simulation model that leverages the Boundary Element Method (BEM) and a Direct Field Acoustic Testing (DFAT) simulation module. The primary objective is to virtually reproduce test sound fields that closely mimic the full fluctuating pressure environments aircraft encounter during flight using only loudspeaker arrays. This approach involves virtually reproducing a sophisticated test setup, typically comprising hundreds of drivers actively managed to generate a specific sound field. This setup is designed to virtually replicate various complex pressure environments, such as those produced by a Turbulent Boundary Layer, the complex pressure fields generated by aircraft propellers or jet engines. The use of active noise generation simulation helps determine the feasibility of a given pressure field and the capability of a test facility to simulate it accurately. The virtually reproduced sound fields simulated by this model show remarkable potential in approximating real-world pressure loadings. This capability is particularly useful in establishing pre-test predictions for fuselage testing such as sidewall build-ups: including insulation, and damping treatments, TVAs and TMDs.

Method for Two-Stage Radar Measurement of the Blade Repetition Rate of a Propeller-Driven Aircraft

Introduction. Radar images of aircraft propellers can significantly improve the quality of their recognition and protection against simulating interference. Such images can be obtained using algorithms based on an inverse antenna aperture synthesis. A key factor determining the quality of image acquisition is the accuracy of the rotor blade rotation frequency measurement. In 2019, a method for measuring the blade repetition rate was proposed, which is based on convolution of the "secondary" signal modulation spectrum while simultaneously eliminating the influence of the Doppler frequency of the signal reflected from the aircraft body. In sequential analysis, the number of cycles is determined by the ratio of the maximum blade repetition rate (hundreds of hertz) to the discrete frequency shift (thousandths of hertz). In this case, to solve the measurement problem, the required number of cycles should be hundreds of thousands, which is expensive in terms of practical implementation.Aim. Development of a two-stage method for measuring the blade repetition rate, which allows the number of signal convolution cycles to be reduced by hundreds of times.Materials and methods. The proposed method is aimed at implementing adaptation circuits to an a priori unknown rotor speed of an aircraft, which can be determined based on the blade rotation frequency. The method involves measuring the blade frequency in two stages: a rough measurement of the blade frequency rate followed by its accurate measurement within the limits of the maximum errors of the rough measurement.Results. A method for a two-stage measurement of the blade repetition rate as applied to the construction of radar images of aircraft propellers is proposed. The feasibility of the method is illustrated by the example of a signal reflected from a Mi-8 helicopter. The requirements to the measurement error of the blade repetition rate and to the frequency analysis step at the precise measurement stage are formulated. The requirement to the repetition rate of probing signals is substantiated, the fulfillment of which ensures an unambiguous restoration of the spectrum of "secondary" modulation of the signal reflected from the blades of a propeller-driven aircraft.Conclusion. The developed method for a two-stage measurement of the blade repetition rate ensures the adaptation of algorithms for constructing radar images of aircraft propellers to their rotation frequency.

RANS-Based Aerodynamic Shape Optimization of a Wing with a Propeller in Front of the Wingtip

Accounting for propeller–wing interaction allows for the design of more efficient propeller aircraft through strategic propulsion integration. In this paper, the cruise drag of a wing with a propeller located in front of the wingtip is minimized using twist and airfoil-shape design variables. Reynolds-averaged Navier–Stokes computational fluid dynamics with an actuator-disk approach is used for the flow simulations, and a gradient-based algorithm is used for the optimization. Changing the rotation direction of the propeller and optimizing the twist and airfoil shapes of the wing are found to impact the aerodynamic performance significantly, as expected. However, optimizing the wing while accounting for the propeller slipstream during optimization provides little benefit over optimizing it without accounting for the propeller slipstream—a difference of less than one drag count.

Adaptive maintenance window-based opportunistic maintenance optimization considering operational reliability and cost

Opportunistic maintenance (OM) reduces maintenance costs by combining the maintenance of multiple components. It has recently been widely used in complex systems. However, few studies have considered that advance maintenance results in the insufficient utilization of reliability. Besides, the applicable conditions for advance and postpone maintenance are ignored in existing literature. In this paper, the economic benefits and failure risk of advance and postpone maintenance are evaluated to fully utilize component's reliability. In addition, all maintenance types (preventive maintenance, corrective maintenance, and replacement) and programs (advance and postpone maintenance) for critical components and non-critical components are discussed based on the degree of overlap of the components’ maintenance windows. Then, an operational reliability (OR) model based on system availability is established to reflect the operating state of the system under damage and maintenance. In order to maximize OR and minimize maintenance costs, a multi-objective optimization model for an OM strategy based on adaptive maintenance window is proposed. Finally, a case study of a propeller aircraft system is conducted to verify the proposed model. It proves superior to the traditional OM and other models in terms of cost and OR.

ПОРІВНЯЛЬНИЙ АНАЛІЗ МАЛОГАБАРИТНИХ ВИСОКОШВИДКІСНИХ СИНХРОННИХ МАГНІТОЕЛЕКТРИЧНИХ ДВИГУНІВ

Using the methods of mathematical modeling, a comparative analysis of the characteristics of three variants of small-sized high-speed synchronous magneto-electric motors (SMD) with permanent magnets on the rotor, which are intended for driving the propeller of quadcopter-type aircraft, was investigated and carried out. Namely: SMD with external grooved stator and internal rotor; SMD with internal grooved stator and external rotor; SMD with internal clear-pole stator and external rotor. On the example of an aircraft with a total mass of 4 kg, a comparative analysis of the amount of power developed by the specified engine variants under the same operating conditions: the same overall dimensions, rotor speed, current in the stator winding and volume of permanent magnets was carried out. An assessment of the magnitude of electromagnetic moment pul-sations is given. It was established that although an SMD with an internal clear-pole stator is the most technologically simple, but under the same other conditions, it is inferior in power to an SMD with an internal slotted stator and an external rotor. References 7, Figures 4.

Research on the Calculation Method of Propeller 1P Loads Based on the Blade Element Momentum Theory

Aircraft propellers produce relatively large in-plane loads, called propeller 1P loads, during maneuvers such as turning, diving, and lifting, and these loads can negatively affect the flight and control of the aircraft. In order to study the change rule of 1P aerodynamic loads, in this paper, a mathematical model of the propeller 1P aerodynamic loads has been developed based on the blade element momentum theory. This mathematical model was then corrected using the Pitt–Peters incoming flow correction method, the Prandtl tip correction method, and the propeller root flow correction method. Based on this mathematical model, a calculation procedure for the propeller 1P aerodynamic loads was developed using MATLAB software, and the accuracy of the procedure was verified by comparing the results with CFD simulation results. Numerical simulations show that the results calculated based on the proposed mathematical model for the coefficients of thrust, power, bending moment, and the tangential force of the propeller have an error of less than ±6.00% compared to the CFD simulation results. For a small inflow angle, the coefficients of bending moment and tangential force of the whole propeller fluctuate in a small range. But, as the inflow angle increases, the fluctuation range of the aerodynamic characteristic parameters of the propeller increases and the fluctuation becomes more complicated. Through numerical calculations, it has been shown that the mathematical model presented herein is reliable and accurate. In addition, it greatly shortens the calculation time and improves the calculation efficiency. It is expected that the proposed model can provide a certain help for the strength design of the propeller structure and the study of the aerodynamic performance of the whole aircraft.

Wind Tunnel Investigation of Transient Propeller Loads for Non-Axial Inflow Conditions

Recent developments in electrical Vertical Take-off and Landing (eVTOL) vehicles show the need for a better understanding of transient aero-mechanical propeller loads for non-axial inflow conditions. The variety of vehicle configurations conceptualized with different propellers in terms of blade geometry, number of blades, and their general integration concept results in aerodynamic loads on the propellers which are different from those on conventional fixed-wing aircraft propellers or helicopter rotors. Such varying aerodynamic loads have to be considered in the vehicle design as a whole and also in the detailed design of their respective electric propulsion systems. Therefore, an experimental approach is conducted on two different propeller blade geometries and a varying number of blades with the objective to explore the characteristics at non-axial inflow conditions. Experimental data are compared with calculated results of a low-fidelity Blade Element Momentum Theory (BEMT) approach. Average thrust and side force coefficients are shown to increase with inflow angle, and this trend is captured by the implemented numerical method. Measured thrust and in-plane forces are shown to oscillate at the blade passing frequency and its harmonics, with higher amplitudes at higher angles of inflow or lower number of blades.

Turbulence ingestion noise generation in rotating blades

The interaction between ingested turbulence and rotating blades is a key source of broadband noise in engineering applications. In this paper, a far-field noise model accounting for source correlation across the span of the blade and between blades is developed and applied to the study of homogeneous isotropic turbulence ingestion by a model cooling fan, wind turbine and aircraft propeller. The widely used theory of Amiet is revisited and it is shown that previous works produce conflicting results when attempting to account for blade-to-blade correlation. Central to the model is the calculation of the time between blade chops of the same turbulent eddy as heard by the observer. In this paper it is shown that, when derived correctly, Amiet's theory accounts for correlated sources between blades and, thus, can predict haystacking tones. Comparisons with the new rotational formulation and with experimental data enable us to show that Amiet's theory can be used to accurately predict turbulence ingestion noise from open rotors. In particular, it is found that the infinite-span assumption in strip theory and the neglect of correlation effects across the span do not undermine the accuracy of this theory. This is of great importance because, unlike Amiet's theory, models which treat rotational effects and source correlation exactly are expensive to evaluate routinely at high frequencies due to the slow convergence of infinite series with Bessel functions.

Control system for noise-resistant electronic speed controller of a brushless electric motor for an unmanned aerial vehicle

Objectives. The high demand for unmanned aircraft and their efficiency makes the production of their components a matter of relevance. One of these components is the speed controller of the brushless electric motor of the propeller motor group. At the current time, Russian industry, however, does not mass-produce them. In order to start production, control methods and algorithms for the hardware and software parts of devices of this type are needed. Criteria for selecting the main components also need to be formalized. The aim of this work is to develop a method for the software control of electric motors. This includes block diagrams and invariant algorithms and methods for the calculated selection of parameters of the main microcontroller of the electronic speed controller.Methods. Methods of algorithmization, expert assessments, linear computational processes and experimental studies were used.Results. The paper presents the theoretical basis for controlling the required motors. It proposes a block diagram of the implementation of the controller, and a technique for switching windings when controlling with a trapezoidal signal is proposed. Examples are given in the form of an oscillogram. Based on theoretical research, an invariant algorithmic apparatus was developed for building software for various types of microcontrollers. Block diagrams of all the main modules of the software are also presented. The main ones include: the event switching algorithm; and the main endless loop of the microcontroller. The requirements for microcontrollers to create the various types of speed controllers are formalized herein and presented in the form of a set of mathematical expressions. They enable the number of required peripheral devices and microcontroller ports to be calculated according to the requirements for the microcontroller, as well as the computing power of the core used.Conclusions. Experimental studies show the reliability of the theoretical research presented herein. The results obtained can be used to select the optimal element base and develop software for speed controllers of electric motors of the propellers of unmanned aircraft.

Aspects of choosing the number of slots for an electric machine to drive an aircraft propeller

Aspects of choosing the number of slots for an electric machine to drive an aircraft propeller

Technical Note: Analytical Estimate of Rotor Controls Required for a Propeller Wake Disturbance Rejection

During helicopter air-to-air refueling, the aircraft propeller's jet can engage with the helicopter rotor. The impact on the helicopter rotor thrust and aerodynamic hub moments is solved analytically for the first time, based on blade element momentum theory. The collective and cyclic blade pitch controls needed for disturbance rejection are computed for a typical air-to-air refueling scenario. A propeller jet affecting the retreating side of the rotor requires much more pilot controls to retrim than an impingement on the advancing side.