Supercavitating Propellers-design Theory and Experimental Evaluation PDF Download
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Author: Bohyun Yim
Publisher:
ISBN:
Category : Propellers
Languages : en
Pages : 0
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Author: Bohyun Yim
Publisher:
ISBN:
Category : Propellers
Languages : en
Pages : 0
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Author: Richard A. CUMMING
Publisher:
ISBN:
Category :
Languages : en
Pages : 55
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An experimental investigation of three methods of increasing the leading-edge thickness of supercavitating propeller sections was conducted. The purpose of the investigation was to determine which method could be used that would result in the least impairment of the hydrodynamic performance for a given increase of the leading-edge thickness. The three methods were: (1) arbitrary thickening of the section beyond the bounds of the theoretical cavity; (2) use of a greater angle of attack to increase the thickness of the theoretical cavity and, hence, the allowable section thickness; and (3) addition of a parabolic thickness to both the face and back of the section. Five supercavitating propeller models incorporating these three methods of increasing the section thickness were tested in a water tunnel, for a range of various cavitation numbers and advance coefficients. The results indicate that parabolic thickening of the cavity is superior to the arbitrary thickening of the section beyond the theoretical cavity boundary. Use of an increased angle of attack leads to a greater loss of performance than do the other two methods, but it has excellent resistance to face cavitation and, therefore, is recommended where resistance to face cavitation is of great improtance. (Author).
Author: Richard Hecker
Publisher:
ISBN:
Category : Propellers, Supercavitating
Languages : en
Pages : 318
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In order to evaluate the TMB design method for supercavitating (SC) propellers, and the validity of the theoretically calculated supercavitating design charts, several supercavitating propellers were built and tested in the TMB 24-inch water tunnel. The test results are given. Comparisons between the predicted performance and the test results showed that the predictions are adequate enough to warrant the use of the TMB supercavitating series charts. Parts of the theory used in the design method are inadequate, however, and improvements in the theory can be expected to lead to more accurate predictions. Calculations were performed using nonlinear lift coefficients and cavitating corrections, but only a small improvement was obtained. Finally, it is concluded that a rational lifting surface theory is needed. (Author).
Author: David W. Taylor Naval Ship Research and Development Center
Publisher:
ISBN:
Category : Shipbuilding
Languages : en
Pages : 356
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Author: Okitsugu Furuya
Publisher:
ISBN:
Category :
Languages : en
Pages : 67
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The original objective of the present work was to develop an analytical tool for predicting the off-design performance of supercavitating propellers over a wide range of operating conditions. Due to the complex nature of the flow phenomena, a lifting line theory simply combined with the two-dimensional supercavitating cascade theory was selected. Results of this simple method provided surprisingly accurate predictions for the performance at fully developed cavitating conditions. It was indicative that the fully-developed, supercavitating propellers had strong cascade effects on their performance, and also that the three-dimensional, propeller geometry corrections could properly be made by the lifting-line theory. As was expected, however, the predicted thrust and power coefficient curves with this propeller theory showed a significant deviation from experimental data in the range of advance speeds J's larger than designed advance speeds where the partially cavitating conditions are expected to occur. effort was then made to improve the prediction capability of the above propeller theory at partially cavitating conditions. A new nonlinear partially cavitating cascade theory was developed to provide a proper 2-D loading basis under such conditions. A slight improvement on the prediction capability of the propeller theory was achieved with the new set of data, but not to a satisfactory extent.
Author:
Publisher:
ISBN:
Category : Weights and measures
Languages : en
Pages : 234
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Author: John J. Nelka
Publisher:
ISBN:
Category : Cavitation
Languages : en
Pages : 84
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Results are given showing the experimental effect of propeller-blade warp on open-water performance, cavitation performance, unsteady field-point pressures, and unsteady propeller loading for a series of warped propellers. Blade warp is defined as the angular displacement at the midchord point of the blade section from the blade reference line in the plane of rotation. Open-water results indicate that at the design thrust-loading coefficient and shaft horsepower the warped propellers are as much as 4.5 percent less than the design rpm. Cavitation results show a widening of the cavitation-free bucket with increasing warp; however, there is some crossover in the inception of back cavitation and tip-vortex cavitation. Field-point pressures and the unsteady propeller forces and moments have been found to decrease with increasing warp to reductions previously achieved with blade skew. (Author).
Author: United States. National Bureau of Standards
Publisher:
ISBN:
Category : Hydraulic engineering
Languages : en
Pages : 260
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Author: Justin H. McCarthy
Publisher:
ISBN:
Category : Propellers
Languages : en
Pages : 52
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Static stresses were obtained in laboratory experiments for a destroyer propeller, having aerofoil blade sections, and a super-cavitating propeller, having wedge-shaped blade sections, using specially constructed pressure chambers that allowed the blade faces to be loaded under air pressure. A new method for applying beam theory is presented that closely predicts the magnitude and distribution of radial stresses on the destroyer propeller blade. For the supercavitating propeller, neither the proposed beam-theory method nor a particular computerized-shell analysis can be considered entirely satisfactory for prediction of blade stresses. (Author).
Author:
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 908
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