Search

The report presents a detailed uncertainty analysis for a podded propulsor open water test. A brief overview of the uncertainty analysis methodology has been provided, with a particular focus on the elements that are unique to the experiments with podded propulsors. The method used follows that of the American National Standards Institute (ANSI) and American Society of Mechanical Engineers (ASME) standard on Measurement uncertainty and the approach described by Coleman and steele in their 1999 book Experimental and Uncertainty Analysis for Engineers. The variables of interest in the podded propulsors uncertainty analysis were propeller thrust, unit thrust, propeller torque, forces and moments on the propulsor in the three orthogonal directions, propeller shaft rotational speed, carriage advance speed, azimuthing angle, water density (function of water temperature) and propeller diameter. The uncertainty analysis results of the experiments conducted using the NSERC-NRC dynamometer system were compared to that of a very high quality, well-established equipment (tests done in the IOT towing tank) used to measure the performance of some bare podded propellers and the results from the previous similar tests using the same equipment. Comparison of the results showed that the podded propulsor tests using the NSERC-NRC pod instrumentation in the current phase of tests provided the level of accuracy comparable with the established equipment. The uncertainty levels observed in the propeller thrust and unit thrust in the podded propulsor tests were found to be higher than the thrust uncertainty for the baseline tests, but less than the corresponding uncertainties found in the previous tests done on the same podded propulsors with same operating conditions with the same equipment. For majority of the cases, the primary element of the uncertainty of the performance coefficients was the bias error (90% or more on the total uncertainty). To reduce the overall uncertainty in the final results, the primary focuses should be to reduce the bias error in the equipment. The uncertainty analysis results provided strong evidence that the experimental data obtained using the NSERC-NRC dynamometer system presented the true performance characteristics of the model scale podded propulsors under consideration., yes

This study presents the experimental study of some podded propellers with different hub geometry. The experiments were conducted in the cavitation tunnel at Institute for Ocean Technology (IOT), NRC Canada. Four model propellers having the same blade sections but different hub geometry were designed and manufactured and tested at different cavitating conditions. The objective was to investigate the variations of propulsive performance and cavitation characteristics of the propellers because of different hub geometry. Tests were done in various combinations of flow velocity, propeller rotational speed and tunnel pressure. All of the propellers were tested in a wide range of advance coefficients and cavitation numbers to measure propeller thrust and torque. Reynolds Number effects on performance at design cavitation number, effect of hub taper angle on cavitation inception and comparison of performance under various cavitation conditions were investigated. The study gives a suitable basis for comparison of pusher and puller propellers' performance (propeller only case) under cavitating conditions. It is concluded that the puller configuration propellers had better performance than the pusher configuration propellers under majority of test conditions. Results also show that hub taper angle does not have noticeable effect on visual cavitation inception and desinence.

The aim of the paper is to describe the influences of conventional and azimuthing podded propulsion on passenger ferry maneuvering, particularly turning circle and zig-zag maneuvers. The MATLAB-simulink program was used to simulate the turning circle and the zig-zag maneuvers. The program was developed based on the mathematical model for ferry maneuvering. The model involved the setting-up of a 4-DOF in a modular of the Mathematical Modelling Group (MMG) of the hull, propellers-rudder or pod system. The simulation includes separating components of the hull equations, propeller-rudder or pod systems as well as the interaction between them. The results indicated that the azimuthing podded propulsion has an advantage for turning circle performance, meanwhile conventional propulsion is beneficial for zig-zag maneuvers. The 1st and 2nd overshoot times of conventional propulsion of the sea trial are higher than the simulation; but the turning cirles of the sea trial are lower.

The following is a report detailing the procedure, analysis, and results of seven sets of tests conducted on podded propellers. The tests were conducted on either a single pod or dual pods running along side one another. Two sets of tests were conducted on a propeller of 270mm while the remainder were on a prop of 200mm. Two of the cases were numerical.Not much is known about the performance characteristics of podded propellers to this date. This is reason behind the current study. With the data already collected along with future tests planned researchers will gain valuable knowledge about podded propellers and will be able to engineer future pods more efficiently and effectively.

When multiple dynos are integrated into a system, calibration is required to minimize error due to cross-talk, etc. These calibrations are performed by calculating the theoretical static load on each dyno and then comparing the value with the actual measured load.A calibration matrix is constructed as a means of transformation from measured to theortetical loads in the hopes of accounting for much of the existing error. These matrices are evaluated on the basis of residual value magnitude.The included matrices have been passed on to the research officers in charge of applying them directly to collected ice test data.

Ever since their first appearances, azimuthing podded propulsors have become increasingly popular. In a parallel development, there has been an increasing interest in arctic shipping. Hence, the number of vessels with azimuthing podded propulsors being capable of navigating in arctic conditions is increasing. The aim of this study is to help the understanding of ice effects on this type of propulsors. The knowledge generated could then be used in updating the regulations governing the design of vessels for arctic navigation, including the podded propulsion systems, by the International Association of Classification Societies. The paper describes the preliminary experimental results obtained in this study so far. The setup designed and built at NRC-IOT, Canada, has the capabiligy of measuring the loads on a podded propeller system operating in ice. It is able to measure loads on the entire model, propeller shaft bearing loads and clade loads. The results suggested that the bearings undergo cyclic loading conditions during the encounters with ice., 1st International Conference on Technological Advances in Podded Propulsion, 14th-16th April 2004, University of Newcastle, UK