Propeller Speed Research Articles

Experimental evaluation of the drag curves of small fixed wing UAVs

Abstract Tight budgets often limit the scope of test campaigns within the development programmes of small uncrewed air vehicles (UAVs). This paper explores a range of combinations of instrumentation suites and protocols for both wind tunnel and flight evaluation, focusing on the key aspect of drawing up the drag curve of the airframe. Through extensive testing of a 5kg maximum take-off mass, fixed wing, twin motor, richly instrumented test platform, we show that automated glides over a range of airspeeds and the slow down manoeuvre are effective ways of determining power-off drag, while estimating thrust from propeller speed, and voltage and current sensing based methods work well for the power-on case. We also seek the most time-efficient and robust mix of the above manoeuvres to yield a given drag curve accuracy level and we find wind condition impacts the manoeuvre makeup of the optimal strategy.

Analysis of Effect of Propeller Rotational Speed Variations on Torque and Power Using Computational Fluid Dynamics (CFD) Method

The speed on the ship is inseparable from a good propeller design in order to get the optimal thrust generated by the propeller motion. The propeller is a very important part in determining the ship's motion. The propeller itself is a tool used to generate thrust that comes from engine power transmitted through the shaft. Computational Fluid Dynamics (CFD) is a very suitable method for analyzing complex systems that are difficult to solve using manual calculations. With these advantages, CFD is often used to analyze a pattern of a system, one of which is the propeller, which in this study uses variations in flow velocity and propeller speed which can affect the value of the torque and power produced by the propeller.

An Enhanced Nonlinear ADRC Speed Control Method for Electric Propulsion System: Modeling, Analysis, and Validation

The electric propulsion system is composed of permanent magnet synchronous motor (PMSM) equipped with propeller load. Due to the strong coupling of propeller speed and load torque, they considerably characterize dynamic response and disturbance suppression capabilities of the speed controller. Traditional nonlinear active disturbance rejection control (NADRC) is less effective in dealing with a step change of command speed and large disturbance. In order to provide faster response and stronger disturbance rejection potential, an enhanced NADRC strategy is proposed in this paper. Initially, a linear extended state observer (LESO) is applied to preliminary estimate the total disturbance. Then, using the designed weight regular function, this estimation is introduced into the nonlinear extended state observer (NESO) with a cascade structure. The convergence, stability and disturbance estimation performance of the proposed strategy are then analyzed. Finally, experimental validation is performed based on a constructed experimental platform. The results show that the proposed method reasonably enhances the speed response and anti-disturbance performances.

The Impact of Slow Steaming on Fuel Consumption and CO2 Emissions of a Container Ship

Modern marine propulsion systems must be reliable, energy efficient, environmentally friendly, and economical. Efforts to reduce fuel costs and carbon dioxide (CO2) emissions per nautical mile have a significant impact on the choice of propulsion system. Considering that there is no alternative for maritime transport, various technical and technological solutions are being considered that aim to improve efficiency and reduce the negative impact on the environment. One of the ways to achieve this goal is slow steaming, which reduces fuel consumption and CO2 emissions. The designed speed of the vessel has a significant impact on the efficiency of slow steaming. Slow steaming is particularly suitable for large container ships with a design speed of more than 20 knots. In this paper, the effects of slow steaming are analyzed using the example of a container ship with diesel-engine propulsion. Propulsion systems with low-speed and medium-speed marine diesel engines with mechanical power transmission are investigated. Data on the required engine power and propeller speed were used for the study, obtained from calculations during testing of the ship’s hull model. The effects of speed reduction on specific fuel consumption and emission reduction were analyzed using numerical models of two-stroke and four-stroke diesel engines. The models were calibrated and validated using data provided by the engine manufacturers. The paper analyses four different cases where one or two low-speed diesel engines, or three or four medium-speed diesel engines, are used for propulsion. The analysis concludes that slow steaming can effectively reduce fuel consumption and CO2 emissions, but the choice of the optimal propulsion system is highly dependent on maritime market conditions in maritime transportation. The choice of propulsion system affects the potential of slow steaming.

Reconstruction of Nizhne-Svirskaya HPP hydroturbines using propeller blade runners with variable rotation speed

Reconstruction of axial-flow hydroturbines through installation of variable speed propeller blade runners is considered. Using daily information about water head, capacity, and suction height of Nizhne-Svirskaya HPP units, topograms of hydro equipment operating conditions were created. For obtaining a regular pattern of unit capacity usage in power grid, those topograms were redesigned into histograms of relative duration of normalized capacity. Using aforementioned histograms enabled to substantiate the possibility of application of propeller blade runners for HPP reconstruction. The most dangerous unit operating conditions were identified in terms of cavitation. The upper limit for turbine cavitation coefficient was established. Methodologies were presented and a choice was made from several blade angles using analysis of efficiency levels, maximum normalized capacity, and turbine cavitation coefficient. Based on empirical dependencies, approximate losses in water parts induced by differences in geometry of old and reconstructed turbines were considered. With specifics of the propeller blade runner and losses in elements of the turbine water part taken into account, an estimated model hill chart of a hydroturbine with a new blade runner was created. This was used to plot an estimated prototype hill chart of the reconstructed hydroturbine operating with variable rotation speed. Three main operating zones are highlighted on the prototype hill chart. Simultaneously with achieving higher values of capacity compared to those of a Kaplan turbine, the operating range has been widened compared to traditional propeller turbines with a constant speed.

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.

Analysis of water gap membrane distillation process with an internal gap circulation propeller

A novel propeller-aided water gap membrane distillation (P-WGMD) system has been investigated through detailed mathematical modeling, and its performance was compared with that of a baseline/conventional WGMD system. The proposed system contains a rotating propeller blade, which improves mass and heat transfer within the gap space. The installed propeller and its modeling within the gap chamber represent the novelty of the present work. The influences of various design variables, including propeller diameter, propeller material, propeller thickness, position of the propeller, and the thickness of the gap on the distillate production and the specific thermal energy consumption (STEC) of the proposed propeller-aided P-WGMD system, are investigated. In addition, the effects of different operating parameters such as feed water temperature, coolant temperature, feed water flowrate, and coolant flowrate on the performance of the baseline WGMD and propeller-aided P-WGMD processes were examined. Results revealed that propeller material and propeller thickness showed marginal effects on the system's performance, especially when the thermal conductivity of the propeller material exceeded 100 W/m K. The propeller position has a strong influence on the system performance, and placing the propeller away from the membrane surface improves the system performance. Larger propeller diameters and higher propeller speeds exhibit better system performance. Propeller speed and propeller diameter are found to be the most dominant design factors affecting the performance of the proposed system. Furthermore, the P-WGMD system exhibits superior performance over the baseline WGMD system under the same operating conditions, where the flux of the P-WGMD system could reach a maximum value of 322 kg/m2h at a feed flowrate of 10 L/min, propeller speed of 1000 rev/min, feed temperature of 70 °C, coolant temperature of 20 °C, and coolant flowrate of 2.5 L/min. The presence of a propeller within the gap chamber reduces the resistance to heat transfer from about 0.002057 m2K/W to 0.0001144 m2K/W, reflecting the enhancement gained in the proposed system. Freshwater costs from the proposed system vary between 8.243 $/m3 and 11.57 $/m3 while those from the baseline system fall between 9.971 $/m3 and 21.11 $/m3.

Analysis of Thrust & Torque B-Series Propeller using CFD: Variation of Blade and nProp

T he propeller is an important part of determining the ship's maneuverability. The propeller itself is a tool to produce thrust that comes from engine power which is transmitted through the shaft . At their defined radial position, Propeller thrust (N) and torque (Nm) are formed from propeller blade foil sections at the local lift and drag. Particularly, the total propeller thrust will be integrated into an axial lift vector for the sections from root to tip . The selection of a good propulsion device will affect the force of the ship. One way to choose the propulsion of the ship is the selection the type of propeller and the provision of new propeller variations to produce maximum thrust. For that reason, this study aims to analyze of thrust and torque of B-series propellers using CFD by varying the number of blades: 3, 4, and 5 blades; and the propeller speed (nProp) i.e., 325, 525, and 725 rpm. The numerical analysis using computational fluid dynamics (CFD) was conducted to identify the thrust (N) and force (Nm) of the propeller. The CFD simulation consists of three main steps: pre-processor, solver manager, and post-processor. The results show that the thrust and torque significantly increased at the higher number of blades and nProp.

Monitoring of the cavitation inception speed and sound pressure level of the model propeller using accelerometer attached to the model ship in the cavitation tunnel

The naval vessel uses sonar to detect and identify the enemy under the water. Therefore, it is necessary to reduce the noise of the own ship to detect the enemy ship, and also to avoid detection by the enemy's sonar system. To reduce the noise of the ship, cavitation of the propeller should be prohibited; and when engaged in anti-submarine warfare operations, the ship must sail below the cavitation inception speed. Therefore, the cavitation inception speed and sound pressure radiating from the propeller should be monitored in real time. In this research, an algorithm is developed for the condition-based monitoring of the propeller sound using an accelerometer on the hull above the propeller.

Vertical Structure of PM2.5 and CO2 Concentrations in The Greater Bandung Air Basin

The Greater Bandung air basin, surrounded by mountains and hills, has a unique topography that could block the horizontal displacement of pollutants. Consequently, air pollution in these areas is affected by the vertical-spread pattern of pollutants. Previous studies identified that PM2.5 and CO2 concentrations in Telkom University Bandung have a similar trend data vertically up to 30 m above the ground. Therefore, this study was conducted to observe and analyze the distribution of pollutants in the vertical direction and broaden the measurement points using drones. A drone was chosen considering the available high building is limited, also to minimalize the spatial differences. The measuring parameters are PM2.5 and CO2 concentrations and meteorological conditions (temperature/T, relative humidity/RH, and pressure/P). Two different times are chosen that are at day time (August 31, 2019) and nighttime (September 30, 2019), at altitudes up to ~80m. During measurements, it was indicated that the change of the rotor or the drone’s propeller speed affected the airflow. Results show that there are indications of PM2.5 deposition in the morning, which decreases to ~20 μg/m3 after the height of >40 m. The PM2.5 concentrations have been lifting and mixing evenly from the afternoon to the evening, increasing at night to ~15 μg/m3. As for CO2, concentrations level up to ~80 m altitude do not have a significant or relatively stable change.

Dynamic Event-Triggered Path-Following Control of Underactuated Surface Vehicle With the Experiment Verification

This paper investigated the dynamic event-triggered control scheme for the path-following activity of underactuated surface vehicle (USV) subject to actuator saturation and gain uncertainties. Specifically, a dynamic event-triggered mechanism with the adjustable threshold is developed to reduce the communication burden and the execution wear of actuators. Unlike most existing event-triggered results, in which the threshold parameters are always fixed, the developed mechanism can ensure that the triggering thresholds are updated online in an adaptive manner, so as to achieve better resource efficiency. Furthermore, taking the practical measurable variables (i.e., revolving speed of propeller and rudder angle) as the control input, an auxiliary system is designed to deal with the influence of actuator saturation, which is distinct from most existing saturation-tolerant methods for USV. For merits of the neural damping technique, both the internal and external uncertainties are remodeled and only four adaptive parameters require to be updated online. Considerable effort has been made to guarantee the semi-globally uniform ultimate bounded (SGUUB) stability. Finally, the numerical simulation and physical experiment are illustrated to demonstrate the remarkable performance of the proposed algorithm.

A systematic investigation on the manoeuvring performance of a ship performing low-speed manoeuvres in adverse weather conditions using CFD

The International Maritime Organisation (IMO) requirements for the control of greenhouse gas (GHG) emissions of shipping have raised interest in ship manoeuvrability in adverse weather conditions when compliance is accomplished simply by reducing the main engine power. In response, the IMO has adopted the guidelines for determining minimum propulsion power to maintain the manoeuvrability of ships in adverse conditions. In the present paper, a systematic investigation on the manoeuvrability of a ship with different low advance speeds in adverse weather conditions was conducted by means of an unsteady Reynolds-Averaged Navier-Stokes solver. The numerical results demonstrated the contribution of low advance speeds to the course-keeping and turning circle manoeuvre, providing a practical insight into the manoeuvring performance of a ship with minimum propulsion power in adverse weather conditions. For the course-keeping control, the ship experienced more aggressive steering as the propeller revolution decreased in the oblique waves, while it appeared that the difference in the rudder deflection according to the change in the propeller speed in the head, beam, and following waves is negligible. The difficulty of the low speed turning manoeuvre was clearly noted when the direction of the incident wave was opposite to the direction towards which the ship intended to turn. It is believed that this paper can also be impactful in improving the guidelines of minimum powering of ships for safe navigation in adverse weather conditions.

Design Automation and Optimization Methodology for Electric Multicopter Unmanned Aerial Robots

The traditional multicopter design method usually requires a long iterative process to find the optimal design based on given performance requirements. The method is uneconomical and inefficient. In this article, a practical method is proposed to automatically calculate the optimal multicopter design according to the given design requirements including flight time, altitude, payload capacity, and maneuverability. The proposed method contains two algorithms, including an off-line algorithm and an online algorithm. The off-line algorithm finds the optimal components (propeller and electronic speed controller) for each motor to establish its component combination, and subsequently, these component combinations and their key performance parameters are stored in a combination database. The online algorithm obtains the multicopter design results that satisfy the given requirements by searching through the component combinations in the database and calculating the optimal parameters for the battery and airframe. Subsequently, these requirement-satisfied multicopter design results are obtained and sorted according to an objective function that contains evaluation indexes, including size, weight, performance, and practicability. The proposed method has the advantages of high precision and quick calculating speed because parameter calibrations and time-consuming calculations are completed offline. Experiments are performed to validate the effectiveness and practicality of the proposed method. Comparisons with the brutal search method and other design methods demonstrate the efficiency of the proposed method. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —The proposed method is fast and practical to obtain an optimal solution by only using a low-performance web server, and the algorithm has been published online at <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">http://www.flyeval.com/recalc.html</uri> to provide an online optimization design service for users. To make it convenient to apply the proposed method to multicopter designs, the propulsion system combination database obtained by our off-line algorithm is released along with the article. This database includes more than 1500 experimentally calibrated propulsion combinations, which are adequate for readers to use the proposed optimization algorithms to design multicopters with weights (sizes) ranging from 0.2 to 50 kg.

Simulation Analysis of Power Consumption and Mixing Time of Pseudoplastic Non-Newtonian Fluids with a Propeller Agitator

In order to study the effect of a high twist rate propeller on the flow field characteristics of pseudoplastic non-Newtonian fluids, the numerical simulation method was used to analyze the mixing flow field of pseudoplastic non-Newtonian fluids at different concentrations in this paper. By changing the rotational speed and the blade installation height, the vorticity, turbulent energy, mixing power consumption, mixing time and mixing energy of the flow field were analyzed. By analyzing and comparing the research results, it was found that increasing the mixing propeller speed can effectively improve the mixing effect. Single-layer arrangement of mixing propeller is not suitable to be placed close to the bottom of the tank, and the mixing of the upper flow field is weaker. Under the same conditions, when the viscosity of pseudoplastic non-Newtonian fluid is increased, the high vorticity and high turbulence energy area is reduced to the mixing propeller area, and the time required for mixing 1.25% CMC solution is 246 times longer than that for mixing 0.62% CMC solution and the required mixing energy also increases sharply. The accuracy of the numerical simulation was verified by experiments. Considering the mixing effect and the mixing power consumption, the single-layer arrangement propeller is more suitable for mixing pseudoplastic non-Newtonian fluids with mass fraction of 0.62% CMC or below. This study can provide a reference for the practical application of propeller mixers to mix pseudoplastic non-Newtonian fluids.

Propeller-integrated airfoil heater system for small multirotor drones in icing environments: Anti-icing feasibility study

Atmospheric icing is one of the most common and hazardous environmental challenges for aircraft operations. So far, only large passenger aircraft, a few general aviation aircraft, and specialized rotorcraft are equipped with ice protection systems because of their additional energy consumption and weight. The emerging markets of small electric aircraft like Urban Air Mobility and Unmanned Aerial Vehicles for transportation, logistics, search and rescue, and other specialized operations will require efficient, lightweight and all-electric ice protection systems in order to allow operations in ice and snow conditions. In this work, an electrothermal ice protection system with an average heat power density of 1Wcm−2 was designed and developed for use on small multirotor drones. Commercially available propeller blades with diameters of 33cm were retrofitted with lightweight multilayer heating foils independently powered by super-capacitors. The heated propellers were tested in close-to-real icing conditions in a small-scale icing wind tunnel. Thrust, rotational speed, and power consumption of a non-heated reference propeller and a heated propeller were compared. In glaze ice conditions at air temperatures > −5°C the thrust of the non-heated propeller fluctuated between 60 and 90% with frequent cycles of ice accretion and shedding for the entire duration of the test. The heated propeller maintained a thrust of >95% in the same icing conditions. In rime ice conditions at air temperatures < −8°C the heating was not sufficient and the thrust of the non-heated and heated propellers similarly decreased over time. Heat flux calculations along the span of the propeller were made for different icing conditions and compared to the heat power density distribution of the tested ice protection system.

Sharp Profile for Icebreaking Propellers to Improve Their Ice and Hydrodynamic Characteristics

Stern-first operation under severe ice conditions (ridges) is one of the most effective modes to increase the operating efficiency of icebreakers and ice ships. However, when a ship overcomes the ridge astern, the propellers continuously interact with ice blocks, and ice moment affects the propeller and the main engine. This leads to propeller speed drop and propeller thrust reduction. Propeller stop is also possible. This is the reason why the propeller ice moment needs to be decreased. Blade profiles with a sharp leading edge are used for this purpose because their thickness is significantly less than that of a traditional icebreaking profile. The application of sharp profiling makes it possible to significantly reduce the ice moment (ice loads) on the propeller, reduce the drop in its speed, and increase the hydrodynamic thrust. The main task when installing blades with sharp profiles is to ensure the strength of their leading edges exposed to ice pressure. In this article, the authors tackle upon some methods of assigning integral and local ice loads on propellers. Solutions for ensuring the local strength of the blade edges were developed and presented. The influence of sharp profiling on the hydrodynamic and cavitation characteristics of ice propellers was considered. The article presents examples of calculating the hydrodynamic propeller thrust and moment, as well as ice loads on a propeller with a sharp and traditional profile, when an ice ship moves through a ridged ice isthmus with its stern first.

A SDNN-MPC method for power distribution of COGAG propulsion system

In order to solve the problems of power distribution taking a long time and large fluctuation of propeller speed in the process of COGAG propulsion system switching operating patterns, model predictive control (MPC) is introduced to control power distribution and a SDNN-MPC method is proposed. Discrete incremental LPV model is established as the prediction model and MPC for power distribution process is designed. In order to make MPC suitable for COGAG, which is a nonlinear time-varying system with short sampling period, a simplified dual neural network (SDNN) with simplified constraints is used to solve the quadratic programming in MPC. A large number of simulation results show that the established LPV model has high prediction accuracy and SDNN is helpful to shorten the execution time of MPC. The softening factor and weight factors in MPC can affect the performance of power distribution control. Two principles are summarized to choose weight factors and the recommended range of the softening factor is 0.026–0.034. Compared with the PI controller, based on the SDNN-MPC the time of power distribution process is shortened and the fluctuation of propeller speed is reduced. The maneuverability and stability of the vessel are improved.

Investigation of the Effect of Rope Cutter on Water Flow behind Ship Propellers Based on CFD Analysis

Small vessels operating in coastal waters are susceptible to propeller failure because of the entanglement of marine debris. Secondary accidents such as the injury of divers may also occur when removing entangling material. Rope cutters are devices used to prevent marine litter from entangling the propeller of small ships. However, installing rope cutters on propeller shafts might affect the working of the propeller. In this study, three-dimensional simulations were performed to investigate the effect of a rope cutter on flow characteristics behind the propeller. The Computational fluid dynamics (CFD) models were validated by particle image velocimetry (PIV) experiments performed in a rope cutter performance testing tank. The study results showed that the installation of a rope cutter on the propeller shaft led to an insignificant reduction in water flow velocity magnitude behind the propeller. Additionally, the effects of the rope cutter on the reductions of thrust (0.87%) and torque (0.76%) of the propeller were also negligible. However, it is very interesting to note that rope cutter installation resulted in a lower vortex formation, leading to a significant reduction in the turbulence intensity behind the propeller by 27.12%, 37.50%, and 47.29% at 100, 150, and 200 rpm propeller speed, respectively. Based on the study results, it can be concluded that rope cutters help to reduce propeller entanglements without significantly affecting the propeller’s working.

Air-floating seismic isolator using propellers

In recent years, studies of the air-floating seismic isolator have been conducted. In these methods, an air compressor is used to supply compressed air to the gap between the seismic isolator and base. When a house should be floated, we do not have to care about space for an air compressor. However, when a work of art or a small precision apparatus should be floated, an air compressor is too large for the seismic isolator. Therefore, we propose a seismic isolator using propellers instead of an air compressor. Four motors and four propellers are used in the proposed seismic isolator. Motors rotate propellers and air is supplied to the duct where air is held in. Then, pressure in the duct increases and the proposed seismic isolator floats like a hovercraft. In order to theoretically determine the relationship between the propeller speed and pressure in the duct, Bernoulli's theorem and equation of continuity are used based on the aerodynamics of the propeller when the propeller and base are far apart. The theoretically derived floating force of the seismic isolator was validated through simulations and experiments. The effectiveness of the proposed seismic isolator was verified through experiments using sine and seismic waves.

Recurrent neural networks for nonparametric modeling of ship maneuvering motion

A Recurrent Neural Network (RNN) model is presented in this paper to predict the ship maneuvering motion. Inputs to the model are the orders of rudder angle and its variation as well as the propeller speed (ship speed) and also the recursive outputs velocities of surge, sway and yaw. The past values for the velocities are retained in the inputs to indicate the influence of historical state of motion on the maneuvering prediction. The KRISO Container Ship (KCS) is taken as the study object. The data obtained from a manoeuvring mathematical model and free-running model test are respectively used to train the neural network. Tactical circles and zigzags are simulated by the RNN, the prediction for maneuvers not involved in the training set shows that the RNN in this paper has good generalization performance. The concept of uncertainty is proposed to be considered in the further work through the analysis.