NUMERICAL ANALYSIS FOR CIRCULATION DISTRIBUTION OF PROPELLER BLADE

A process for numerical analysis of radial circulation distribution of propeller blade is proposed and presented.It is based on the results of numerical simulation of the velocity field around propeller blades and in the wake.The well-known traditional method using tangential velocity data in the wake and applying Stockes＇s theorem was also examined in the investigation.The results from two approaches are compared with each other.It is found that if the traditional way is utilized,in many cases an unexpected ＂hump＂ appears in the circulation distribution at certain outer radius.The authors calculated the circulations directly around blade sections,and it is referred as direct method.The unexpected hump of the circulation distribution disappears in the results of direct method.This article also discusses the reasons of the appearance of the unexpected hump in traditional approach.The direct method is proposed to have a potential in analyzing or verifying the radial road distribution for designed propeller and the numerical analysis instead of experimental validation for circulation distribution can be as a tool in the propeller design process.

Pressure field measurements on large-scale propeller blades using pressure-sensitive paint

Pressure-sensitive paint(PSP)is a global pressure measurement technique.Compared with pressure transducers,PSP has significant advantages such as high spatial resolution and a lack of contact when applied to fast-rotating blades.However,due to the limitations of other pressure measurement techniques,the validation of PSP measurements on fast-rotating blades is generally difficult.In this work,a comprehensive study including PSP measurement,force balance measurement,and simulation was conducted on a 1 m-diameter propeller at the China Aerodynamic Research and Development Center.First,our computational fluid dynamics(CFD)code was validated by comparing the calculated aerodynamic thrust with the results from force balance measurements.Then,the pressure distributions on the propeller blade obtained by PSP were carefully compared with the CFD results under different working conditions.The results of PSP measurements,force balance measurements,and CFD showed good agreement,and the PSP measurement errors were estimated to be less than 5% of the dynamic pressure at the blade tip.Finally,the variations in pressure distribution under different rotating speeds and free-stream velocities were discussed.

Ice-Class Propeller Strength and Integrity Evaluation Using Unified Polar ClassURI3 Rules

A systematic method was developed for ice-class propeller modeling,performance estimation,strength and integrity evaluation and optimization.To estimate the impact of sea ice on the propeller structure,URI3 rules,established by the International Association of Classification Societies in 2007,were applied for ice loading calculations.An R-class propeller(a type of ice-class propeller)was utilized for subsequent investigations.The propeller modeling was simplified based on a conventional method,which expedited the model building process.The propeller performance was simulated using the computational fluid dynamics(CFD)method.The simulation results were validated by comparison with experimental data.Furthermore,the hydrodynamic pressure was transferred into a finite element analysis(FEA)module for strength assessment of ice-class propellers.According to URI3 rules,the ice loading was estimated based on different polar classes and working cases.Then,the FEA method was utilized to evaluate the propeller strength.The validation showed that the simulation results accorded with recent research results.Finally,an improved optimization method was developed to save the propeller constituent materials.The optimized propeller example had a minimum safety factor of 1.55,satisfying the safety factor requirement of≥1.5,and reduced the design volume to 88.2%of the original.

Prediction of propeller non-cavitation noise by superimposing shifted sound signal from an isolated blade

The time-cost of the propeller non-cavitation noise prediction can be greatly re- duced by the isolated blade method, which is validated via hybrid URANS and acoustic analogy, followed by the acoustic characteristics of propeller in time domain are analyzed. Firstly, we predicted the sound of the E779A propeller operating in uniform inflow and found a typical periodic characteristic of the sound pressure distribution on propeller blade as well as the sound signal of the receiver, and the result by the superimposing shifted sound signal from an isolated blade （isolated blade method） agreed well with the result by the integration on total blades, which validated the credibility of the isolated blade method in uniform inflow. Finally, we pre- dicted the sound of a propeller running in the wake of submarine by the isolated blade method, and the result also agreed well with the result by the integration on total blades, which further indicated that the isolated blade method was also applicable for the non-cavitation noise prediction of the propeller running in non-uniform inflow. The noise prediction of the counter-rotating propeller, the pump-jet can also benefit from this method.