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Classic Gatwick propliners
\"When Ronald Waters bought 90 acres of farmland adjacent to the Gatwick racecourse in 1930 in order to set up a private airfield, little did he know how that airfield would evolve over the next eighty-nine years to become the world's busiest single-runway airport. Back in the 1960s and '70s it became a hub for aircraft enthusiasts and photographers who, thanks to the viewing decks, could get up close to the aircraft and enjoy the eclectic mix of new jetliners and old propeller airliners. Tom Singfield, ex-Gatwick Air Traffic Controller and a fan of all classic airliners, has long dreamt of a book showcasing the glory days of Gatwick's classic airliners. After thirty years of searching out the very best colour images of that time, he is now able to publish the results of his searches in this book. These stunning pictures celebrate those wonderful times and the amazing and much missed 'propliners' that operated from Gatwick for the first twenty years after its reopening in 1958\"--Publisher description.
Book
Aerodynamic analysis of toroidal propellers in forward flight
Research is being conducted to develop a new generation of propellers that can enable quieter and more efficient flight. One promising development in this area are Toroidal propellers, for which the blades are shaped as a closed loop. Studies have been conducted for vertical lift, as well as for marine propulsion systems. Fewer studies have focused on the design and performance of Toroidal propellers for advance ratios, airspeeds and Reynolds number values typically encountered during the forward flight of fixed-wing aircraft. The present work uses Computational Fluid Dynamics to assess the aerodynamic performance of Toroidal propellers in operating conditions having low forward flight speeds and high revolutions per minute. Two Toroidal propeller geometries are designed, using blade chord and pitch angle distributions taken from classical Minimum Induced Loss propellers. The aerodynamic analysis of both designs is conducted over a range of advance ratios between 0.40 and 1.25. Aerodynamic results show that, at fixed advance ratio values, the Toroidal propellers can sustain much higher thrust coefficients compared to both Minimum Induced Loss and commercially available propellers, at comparable efficiencies.
Journal Article
Ship hydrodynamic performance analysis and model construction based on CFD method
CFD method has the advantages of high forecast accuracy, wide applicability, strong stability of calculation results, and low cost, and nowadays it has been widely used in various fields. The CFD method has many advantages when applied to ship hydrodynamic performance analysis, specifically to ship hydrodynamic performance prediction, problem mechanism research, and performance optimization. Based on this, this paper utilizes the CFD method to carry out a model analysis of ship hydrodynamic performance. By analyzing the propeller efficiency, the reasoning force and torque of the double propeller in the symmetric case are decreased. However, the efficiency is improved by 1.4% compared with the asymmetric case, which shows that the method adopted in this paper can effectively improve the ship hydrodynamic force. Through the above research, we aim to provide a certain reference for the improvement of ship hydrodynamic performance.
Journal Article
Development and commissioning of an aeroacoustic test bench for the investigation of single and coaxial propeller noise
This paper describes the design and commissioning of an aeroacoustic test rig for the study of single and coaxial propeller propulsive systems. The size of the propellers matches typical drone applications. The experimental setup, designed and commissioned at the ALCOVES anechoic laboratory of von Karman Institute for Fluid Dynamics, is equipped with aerodynamic sensors for performance analysis and is surrounded by a microphone antenna for the characterization of the noise level and directivity. Thefacility permits varying different parameters such as the longitudinal distance between the rotor planes, and the rotational speed/direction of each propeller. Requirements for the qualification of the test room consist of low-level background noise and minimized turbulence ingestion noise. Two experimental databases have been constituted and are joined to the present paper: (i) for the DJI 9450 two-bladed propeller, verified against data from the literature, and (ii) for single and coaxial contra-rotating Mejzlik two-bladed propellers. The proposed benchmark data will support the validation of low- and high-fidelity numerical methods.
Journal Article
A Study on the Effect of Toroidal Propeller Parameters on Efficiency and Thrust
This paper delves into the effects of a toroidal propeller’s geometrical characteristics on its thrust and efficiency. The focus is on three distinct numerical distributions: the outward inclination angle, the pitch angle, and the number of blades. The Reynolds-Averaged Navier–Stokes (RANS) method is employed to analyze the propeller’s open-water performance, taking into account cavitation flow, and a test bed was constructed to verify the rationality of CFD simulation. The findings reveal that the toroidal propeller’s efficiency and thrust coefficient initially increase with the outward inclination angle, followed by a decline; the angle of maximum efficiency is identified at 23.25°. A reduction in the pitch angle leads to a temporary rise in efficiency, which subsequently falls, accompanied by a continuous decrease in the thrust coefficient. The optimal selection angle should consider this to prevent negative thrust at lower advance coefficients, which could further impact overall efficiency. An increased number of blades elevates the thrust coefficient and reduces the force on each blade, yet has a minimal effect on efficiency. Additionally, the orthogonal test method was utilized to explore the interactions between these three parameters. The outcomes indicate that, in terms of final power, there is no significant interaction among the three parameters under investigation. However, notable interactions are observed between the pitch angle and the number of blades, the outward inclination angle and the pitch angle, and the outward inclination angle and the number of blades. Consequently, the study’s findings facilitate the selection of parameter combinations that yield higher efficiency or thrust coefficients.
Journal Article
Modal stress parameters-based methods for defect localization on the propeller blade edges
The stress mode shapes are highly sensitive to the local state of the structure, e.g., holes, cracks, and grooves. In this paper, two new defect indices based on stress mode shapes are developed to locate single or multiple local structural defects with different severity levels on the marine propeller blade edge. A stress modal analysis was performed on the intact model of the blade and the different models of the defective blade. The first four stress mode shapes along the propeller blade edge were calculated for every model of the blade. The new defect indices called modal stress flexibility change and defect index based on stress modal energy were calculated for each stress mode shape. Firstly, the ability of the two new defect indices calculated for each mode to locate a single defect was investigated. Secondly, the effectiveness of the defect indices calculated from the combination of the first four stress mode shapes is investigated for single and multiple defect localization considering different severity levels. Through the numerical investigation, the modal stress flexibility and defect index based on stress modal energy are promising to locate single or multiple defects in real structures such as marine propeller blades.
Journal Article
Analysis of quadcopter propeller vibration based on laser vibrometer
An unbalanced propeller can affect a quadcopter’s performance due to vibration, also decreasing its thrust’s yield. Analyses were conducted to determine the correlation between vibration in the dynamic movement of a balanced and an imbalanced propeller using a laser vibrometer (portable digital vibrometer) PDV-100, to determine the correlation between propeller rotational speed and its vibration, as well as to determine the propeller’s maximum rotational speed to avoid over-vibration. The vibration analysis was conducted on a carbon fiber 2-blade propeller by comparing the results of vibration tests with the propeller blade contour. The vibration response of the propeller has been analyzed at three points, respectively the hub, the center, and the tip of the blade, to determine the point having the largest value of the vibration on the propeller running at a maximum rotation speed of 7000 rpm. The same analysis was made on two propellers: the first one of type 1340 with a diameter of 13 inches and the second one of type 1447 with a diameter of 14 inches. The vibration was reduced by propeller’s static balancing, thus increasing the propeller stability. The result showed that an imbalanced propeller generated a decrease in the rotational speed and higher vibration values compared to the balanced propeller. The vibration values showed a linear dependency to the rotor speed; the higher the speed, the bigger the vibration. The limit of rotational speed for the balanced model of the 1340 type propeller was 5000 rpm whilst the corresponding value for the 1447 type propeller was 4500 rpm. Finally, the result was used to optimize the propeller’s overall performance.
Journal Article
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.
Journal Article
Propeller Open-Water Test Method for Hybrid Contra Rotating Propeller
The Hybrid Contra Rotating Propeller is a developing propulsion system that combines a conventional single-shaft propeller with a POD propeller to achieve high energy-saving performance through a Contra Rotating Propeller. In this paper, a new towing tank test method for the Hybrid Contra Rotating Propeller was suggested. By conducting seven patterns of propeller open-water tests and measuring the individual propeller performance and the interaction between the propeller and the POD, the propeller’s mutual interaction can be obtained. Towing tank tests for a study ship were conducted, and the analyzed results are shown. There exists the effect of the wake of the propeller open boat at an unusual (reversed) test layout, which simulates the Hybrid Contra Rotating Propeller, and this effect must be removed for the accurate estimation of the ship’s performance. In conventional towing tank test methods, this effect on the front propeller was obtained and used to correct the performance of the total unit of the Hybrid Contra Rotating Propeller. The presented method allows for the correct removal of the open boat effect on the performance of each propeller and the propeller mutual interaction, resulting in more accurate power estimation. Furthermore, by using the individual performance of two propellers and interaction terms, the presented method enables us to conduct a power estimation at an arbitrary revolution rate of two propellers.
Journal Article
Vibration transmission suppression for propeller-shaft system by hub-embedded damping ring under broadband propeller force
To suppress the vibration of propeller blades and vibration transmission from the blades to bearings under broadband propeller force, a damping ring placed under the propeller hub is proposed. The configuration of the damping ring is introduced first. Then the analytical dynamic model of the damping ring is established. The dynamic model of the propeller-shaft-multiple bearings system with and without the damping ring is developed based on the modal properties of the propeller-shaft-multiple bearings system, the damping ring and friction interface characteristics between them. Node-to-node contact elements are introduced with both normal and tangential relative displacements. The dynamic model is solved by the Duhamel integration of single-degree-of-freedom system and then by employing the superposition method. It is shown that the damping ring can suppress the responses of the propeller blades and the force transmitted to the foundation at the in-phase blade modes of an integrated forming propeller and the longitudinal mode of the propeller-shaft-bearings system. The suppression mechanism is energy dissipation due to the friction phenomena on the interface. The time histories of the contact variables (tangential relative forces) of given contact points on the hub/ring interface are given to illustrate the local behavior of the contact interface. Parametric analysis is carried out to investigate the influence of the inherent damping of the coupled system, rotation speed, tangential stiffness and friction coefficient on the interface. It is shown that the tangential stiffness and friction coefficient on the interface are two key parameters. The theoretical study will provide some references on designing the damping ring for propellers.
Journal Article