Shape Of Propeller Blades Research Articles

CFD Prediction of Ship Propeller-induced Underwater Radiated Noise

As the negative impact of man-made underwater radiated noise (URN) on marine life is recognized by the scientific community, guidelines and initiatives are proposed by port authorities and international organizations for monitoring and reducing URN from ship operations. In medium to large-size ships, propellers are often the dominating URN source as compared to on board machinery and flow turbulence. Within this paper, URN from cavitating flow around a ship propeller in behind-hull condition is predicted by a high-fidelity CFD solver, coupled with an acoustic analogy method. The noise sources are hydrodynamic flow fields around propeller and rudder models, simulated by CFD with a multi-phase flow model. Far-field acoustic noise is calculated by the permeable Ffowcs-Williams Hawkings (FWH) acoustic analogy method. Unsteady cavitation patterns and URN levels from the numerical predictions are validated against experimental results from a cavitation tunnel test. The propeller blade shape is optimized for minimum cavity volume by parametric design variations and performance evaluations based on steady CFD simulations with a simplified hull wake model. The URN predictions from unsteady CFD-FWH simulations demonstrate that the cavity volume reduction for the optimized blade design can lead to considerable decrease of low-frequency tonal noise.

The impact of curved-tip propeller geometry on hovering drone performance for air quality monitoring

The success or failure of a drone mission depend on several elements, including the drone’s mass and payload, the surrounding environment, the battery’s state, and the propulsion system’s performance. Several studies have been undertaken addressing the propeller performance of this final component, particularly for fixed-wing or quad copter drones with ducted propellers. However, the shape of propeller blades used on tiny civil drones has not drawn as much attention. In this research work, the performance characteristics of a 10 × 4.7-inch curved tip propeller were explored, with the Advanced Precision Composite drone propeller serving as a design reference. This study seeks an alternative to ducted propellers when mass or size limitations prevent their use. The Computational Fluid Dynamics model was confirmed by comparing simulation results to the experimental propeller data source established by the University of Illinois at Urbana-Champaign, starting with a standard type propeller and using thrust coefficient as the key performance indicator. Moreover, the data analysis for the bended tip propeller replicating the well-established model, revealed the benefits as well as the drawbacks of such propellers on the mission profile and the battery lifespan of a quad copter Unmanned Air Vehicle.

Analysis of the mechanism for the three-dimensional hydrofoil and propeller contacting the ice body

Polar propellers working in frozen waters would suffer the threaten of ice loads. However, the complex shape of the blade brings difficulties to the correlation analysis of the propeller-ice contacting phenomena and ice loads. This paper utilized a three-dimensional wing structure to simplify the propeller blade shape to a certain extent. The three-dimensional wing was constructed by selecting a foil profile at 0.75R of a certain PC3 level ice-class propeller (IACS, 2016) and extended the profile in the spanwise direction. Then a propeller-ice contacting model and a wing-ice contacting model were established based on the state-based peridynamics theory. The established models are verified by the model tests results. The hydrofoil shape-controlling parameters, including the attack angle, the thickness distribution, and the bow distribution of the hydrofoil were further studied in the research to investigate their effects on the propeller-ice contacting proceedings.

Blade shape optimization of an aircraft propeller using space mapping surrogates

Propeller performance greatly influences the overall efficiency of the turboprop engines. The aim of this study is to perform a propeller blade shape optimization for maximum aerodynamic efficiency with a minimal number of high-fidelity model evaluations. A physics-based surrogate approach exploiting space mapping is employed for the design process. A space mapping algorithm is utilized, for the first time in the field of propeller design, to link two of the most common propeller analysis models: the classical blade-element momentum theory to be the coarse model; and the high-fidelity computational fluid dynamics tool as the fine model. The numerical computational fluid dynamics simulations are performed using the finite-volume discretization of the Reynolds-averaged Navier–Stokes equations on an adaptive unstructured grid. The optimum design is obtained after few iterations with only 56 computationally expensive computational fluid dynamics simulations. Furthermore, an optimization method based on design of experiments and kriging response surface is used to validate the results and compare the computational efficiency of the two techniques. The results show that space mapping is more computationally efficient.

船尾変動圧力に及ぼすチップレーキの影響

The authors propose a practical method to estimate the reduction rate of propeller-induced pressure fluctuations due to the backward rake around the blade tip. The designed geometrical shape of propeller blades decisively affects the propeller performance and the cavitation characteristics as well. The propeller designers try to reflect positive effects of the geometrical parameters to propeller design to enhance the propeller performance and to reduce the negative effects of cavitation behavior. In the present study, the cavitation tests and the measurement of pressure fluctuations induced by the respective propellers with five kinds of backward tip rake distribution working in the wake distribution behind an inland ship are performed systematically. The effects of the backward rake distribution on the pressure fluctuation signals are clearly demonstrated. The systematic analysis of the measured pressure fluctuations derives a practical formula to estimate the reduction rate of the pressure fluct uations due to the effective backward tip rake. Finally this formula is applied to the measured results of pressure fluctuations on other backward tip raked propellers working in the wake of a large low-speed ship to confirm its effectiveness. The results show that the present simple and practical method is promising but further validation is encouraged through the practical applications.

Study of Ship Propeller Cut and Effecting on Main Engine Running Parameters

Attempt to reduce the CO2 emission from ships and sailing cost, the rate of propeller cut is calculated by established models of propeller diameter cut and propeller blade shape cut. According to the results, after cutting the edge of propeller under equal power, the rev is increased, but the open water efficiency and the speed both are decreased. However, the increase of the rev is quicker than the decrease of the speed. And the AVL BOOST is used to simulate MAN B&W 5S60MC main engine. The main running parameters under the 25%, 50%, 75% and 85% load are calculated. The result indicates that cutting the edge of propeller can increase the rev, improve lubricating and vibrating, reduce oil consumption and improve the economical efficiency.

Self-assembled quantum-dot molecules by molecular-beam epitaxy

Self-assembled InAs quantum-dot (QD) molecules having high dot density and aligned dot set structure, which is defined by nanotemplates, were realized by thin capping and regrowth technique in a molecular-beam epitaxy process. Thin capping of GaAs on InAs QDs leads to the creation of nanoholes having a camel-like nanostructure due to anisotropic strain fields along the [11¯0] crystallographic direction and anisotropic surface diffusion accompanying the QD collapse. Regrowth of InAs QDs on the nanohole templates initially results in the formation of QDs with good size uniformity in the middle of features with the shape of propeller blades. This takes place at the regrowth thickness of 0.6 monolayer (ML). The strain at propellers’ edge starts to play its role, creating sets of quantum dots surrounding the initial and centered dots at the regrowth thickness of 1.2 ML. The elongated configuration of propellers’ blades defines the pattern of QD sets having five to six dots on each side. The dot density of the QD molecules is 3×1010cm−2, one order of magnitude higher than that of initial dot density (2×109cm−2).

저레이놀즈수 영역의 초소형비행체 프로펠러 설계 및 해석

초소형 비행체(MAV) 프로펠러에서 깃 익형의 공기역학적 특성은 매우 중요한 사항이다. 이를 위해서 저레이놀즈수 익형의 성능예측에 층류에서 난류로의 천이과정을 포함하는 XFOIL을 이용하여 프로펠러 깃 익형 단면의 양력과 항력 분포를 해석하였다. 익형모델은 저레이놀즈수 프로펠러 익형에 주로 이용되는 ARA-D 6%을 선택하였다. 계산된 익형의 공력 변수들과 최소에너지손실 조건을 이용하여 시위길이와 피치각 분포를 변화시킴으로써 초소형비행체의 설계조건에 적합한 가장 효율적인 프로펠러 형상을 구하였고, 현재 운용중인 Black Widow의 프로펠러 형상과 같은 설계조건에서 비교하였다. 설계결과 초소형비행체의 프로펠러에 적합하게 제공될 수 있음을 확인하였다. The performance of MAV(Micro Air Vehicles) propellers is highly affected by the aerodynamic characteristics of a 2-D blade airfoil shapes. XFOIL is used to predict the lift and drag coefficients in low Reynolds Number flows. ARA-D 6%, which shows a good performance in low Reynolds Number regions, is selected as a blade airfoil. The 3-D propeller blade shape is optimized with the minimum energy loss condition, and the distribution of aerodynamic coefficients of ARA-D 6% is calculated. The designed optimal blade is compared with the Black Widow's propeller blade shape in the same conditions. The results indicate that the designed propeller installed in MAV can provide a good performance.

Propeller blade shape optimization for efficiency improvement

A numerical optimization technique has been developed to determine the optimum propeller blade shape for efficiency improvement. The method satisfies the constraints of the constant power coefficient and the activity factor. A lifting line theory (vortex lattice method) and a lifting surface theory (3-D panel method) are used to calculate aerodynamic performance parameters of propellers. Both lifting theories use rigid helical wake models. The design variables are twist angle and chord length at mid points of vortex lattices for vortex lattice method and nodes of panels for the 3-D panel method. The optimization code is validated by comparing the results with other numerical schemes. Twist angle and chord length distributions are optimized for various propellers. SR-3 and SR-7 propfan blade shapes are also optimized using the 3-D panel method for aerodynamic load calculation.

Computer Aided Design Methods for Propeller Fillet Gages

One of the most complicated forms encountered in engineering design is that of the marine propeller. The complexities arise from the complicated hydrodynamic surfaces of the propeller blades and the complicated manner in which the blades are oriented with and attached to the hub. Where propeller blades are attached to the hub, the blade shape is blended into the shape of the hub. The geometry of this region is particularly complicated. The shape of the blend is called a fillet, and the blending region is called the fillet region. Sheet metal gages conforming to various blade surface contours are used in the manufacture and inspection of propellers. Five different types of gages define the shape of the propeller in different regions. Fillet gages are such gages that define the shape of propeller blades in the fillet region. This paper describes a new computer-aided method for designing fillet gages. Previous methods of fillet gage design required the designer to follow a complicated layout procedure of determining where a particular unfilleted blade contour intersected the hub. The design of the fillet was then done in another layout procedure. Newly developed numerical procedures incorporated in a computer program have reduced the time required to design a complete set of gages (including fillet gages) from up to several weeks to hours.