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Book Experimental Determination of Unsteady Forces on Contrarotating Propellers for Application to Torpedoes

Download or read book Experimental Determination of Unsteady Forces on Contrarotating Propellers for Application to Torpedoes written by and published by . This book was released on 1981 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents results of measurements of unsteady forces and moments on 4x4 and 4x5 bladed sets of contrarotating propellers in uniform flow and in a 4-cycle wake for application to torpedo propeller design. The uniform flow measurements were made to check earlier results that had been in disagreement with the results from calculations based on propeller theory. The uniform flow results confirmed the earlier results in showing larger forces on the forward propeller which is contrary to the prediction of existing theory. The results of the experiments in the 4-cycle wake showed unsteady forces on the forward propeller due to the effect of the wake along with the interaction forces between the two propellers. No theoretical calculations are available for comparison with the wake results. The present procedure for conducting unsteady force and moment measurements on contrarotating propellers continues to be tedious and easily subject to error. Consequently, it is recommended that no further experiments be conducted using this procedure. It is recommended that for future experiments on contrarotating propellers the shafts be locked together mechanically and that a second dynamometer be used so that unsteady measurements can be made on both propellers simultaneously. (Author).

Book Experimental Investigation of the Unsteady Forces Acting on a Reactangular Flat Plate Due to the Action of a Propeller

Download or read book Experimental Investigation of the Unsteady Forces Acting on a Reactangular Flat Plate Due to the Action of a Propeller written by August F. Lehman and published by . This book was released on 1968 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study was undertaken in a water tunnel to determine the effect of propeller blade thickness, operating KT value, propeller tip-plate clearance and plate width on the forces, moments and pressure induced on a flat plate. The plate was oriented so as to be parallel with the rotational axis of the propeller. Propellers having three blades were tested, with one propeller design having blade thicknesses double that of the other but with both propellers having equal thrust - RPM performance. Plate widths were equal to 1 and 3 propeller radii, with the length of the plate constant at 6 propeller radii. The pressure was measured by a small flush mounted transducer located in the center of the plate surface and directly over the propeller. A comparison of certain theoretical predictions with the experimental force and pressure data resulted in generally good agreement. (Author).

Book Unsteady Propeller Loading Measurement Correlation With Theory and Parametric Study

Download or read book Unsteady Propeller Loading Measurement Correlation With Theory and Parametric Study written by Robert J. Boswell and published by . This book was released on 1968 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Objectives of the present study are to measure the unsteady forces and moments on a series of marine propellers due to circumferentially nonuniform inflow; to correlate the measured unsteady thrust and torque with calculated values, based on various proposed theories; and to investigate variation of unsteady thrust and torque over a range of pertinent parameters, using the method determined from those described to be the best available for calculating unsteady loading. Experimental blade-frequency thrust and torque were compared with values calculated by the following techniques: quasi-steady, two-dimensional unsteady, combination quasi-steady two-dimensional unsteady, and three-dimensional unsteady. The three-dimensional unsteady theory yields the best correlation with experiment; however, the numerical techniques employed breakdown for narrow-bladed propellers and for propellers with blade overlap.

Book Government Reports Announcements Index

Download or read book Government Reports Announcements Index written by and published by . This book was released on 1982 with total page 1262 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Experimental Determination of Propeller induced Shaft Forces

Download or read book Experimental Determination of Propeller induced Shaft Forces written by J. van der Kooij and published by . This book was released on 1980 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Measurement of Multiple Blade Rate Unsteady Propeller Forces

Download or read book Measurement of Multiple Blade Rate Unsteady Propeller Forces written by Stuart D. Jessup and published by . This book was released on 1990 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation of unsteady propeller forces was conducted using model propellers operating in idealized axial wakes. Three-bladed propellers were operated behind 3-, 6-, 9- and 12-cycle wake screens generating blade rate and multiple axial wake inflow harmonics. The axial wake distributions were measured using a Pitot tube. Unsteady propeller bearing thrust and torque were measured with an unsteady force dynamometer. Measurements were compared to calculations using unsteady propeller lifting surface theory. Also, Laser Doppler Velocimetry (LDV) was used to measure the unsteady flow field about the propeller. LDV measurements were used to evaluate the effect of the propeller on the incoming wake. Keywords: Marine propellers; Unsteady loads; Bearing forces; Model tests; Propeller blades. (edc).

Book An Optimization Method for the Reduction of Propeller Unsteady Forces

Download or read book An Optimization Method for the Reduction of Propeller Unsteady Forces written by Thomas S. Mauther and published by . This book was released on 1988 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on the work of Greenblatt (1978), an enhanced optimization technique for the reduction of propeller unsteady forces and the determination of skew distributions has been developed. The current method provides an efficient propeller design tool capable of determining a variety of cubic or quadratic skew distributions, subject to constraints, which minimize the unsteady forces produced by the various harmonic components of the input wake. The original skew optimization method was extended to include higher order harmonics, and the original force calculation method was replaced by an extended version of the method developed by Thompson (1976). Calculation of forces and skew distributions associated with a representative propeller show that acceptable reduction of unsteady forces can be obtained without having to place severe restrictions on the model constraints. The problem considered herein is the generation of propeller noise due to non-uniform inflow velocity fields. This has been still is an issue of research in the area of marine propellers, and it is felt that a recently developed method of calculating unsteady forces may also be applicable in the design and analysis of aircraft propellers. Angle-of-attack fluctuations result in unsteady blade loadings and the generation of propeller noise, and the noise sources are characterized by three types of unsteady force mechanisms: a) turbulence injection; b) vortex shedding; and c) blade-rate.

Book Marine Propellers and Propulsion

Download or read book Marine Propellers and Propulsion written by John Carlton and published by Butterworth-Heinemann. This book was released on 2018-11-30 with total page 612 pages. Available in PDF, EPUB and Kindle. Book excerpt: Marine Propellers and Propulsion, Fourth Edition, offers comprehensive, cutting edge coverage to equip marine engineers, naval architects or anyone involved in propulsion and hydrodynamics with essential job knowledge. Propulsion technology is a complex, multidisciplinary topic with design, construction, operational and research implications. Drawing on experience from a long and varied career in consulting, research, design and technical investigation, John Carlton examines hydrodynamic theory, materials and mechanical considerations, and design, operation and performance. Connecting essential theory to practical problems in design, analysis and operational efficiency, the book is an invaluable resource, packed with hard-won insights, detailed specifications and data. - Features comprehensive coverage of marine propellers, fully updated and revised, with new chapters on propulsion in ice and high speed propellers - Includes enhanced content on full-scale trials, propeller materials, propeller blade vibration, operational problems and much more - Synthesizes otherwise disparate material on the theory and practice of propulsion technology from the past 40 years' development, including the latest developments in improving efficiency - Written by a leading expert on propeller technology, essential for students, marine engineers and naval architects involved in propulsion and hydrodynamics

Book Experimental Investigation of the Effect of Propeller Blade Pitch on Propeller produced Unsteady Bearing Forces and Moments

Download or read book Experimental Investigation of the Effect of Propeller Blade Pitch on Propeller produced Unsteady Bearing Forces and Moments written by D. T. Valentine and published by . This book was released on 1976 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Measurements of Propeller Induced Unsteady Surface Force and Pressures

Download or read book Measurements of Propeller Induced Unsteady Surface Force and Pressures written by and published by . This book was released on 1986 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results of an experimental investigation carried out in the 24-inch water tunnel are presented for the cavitating propeller-induced surface pressures and a reference-area surface force measured on a flat plate boundary representation of a nearby ship hull. Newly designed apparatus for the measurement of surface force on an instrumented disc is described in detail. It involves special dynamometry that can be used in a reverse mode so that the force disc can be driven as a mechanical shaker. A model of a seven-bladed propeller was run in a screen-generated simulation of the steep axial wake velocity distribution for a single screw ship. Results are displayed for the longitudinal and transverse distribution of the first three blade rate harmonic components of the unsteady pressure amplitudes and the unsteady disc force amplitudes at the blade tip clearances of 0.26 (diameter) and 0.41D, over a range of cavitation numbers. The unsteady pressure pulse amplitudes obtained in this work compare reasonably will with measured values obtained previously in a large water tunnel experiment using a complete scale model of the ship hull. The experimentally inferred blade rate harmonic component of cavity volume velocity from the reciprocity measurement agrees approximately with the prediction by the PUF-3 propeller anlaysis scheme. Keywords: Pressure amplitude; Surface force; Propeller excavitation; Reciprocity experiment; Cavity volume velocity; PUF (propeller-induced unsteady forces).

Book Analysis and Experiments for Contra rotating Propeller

Download or read book Analysis and Experiments for Contra rotating Propeller written by Eyal Kravitz and published by . This book was released on 2011 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contra-rotating propellers have renewed interest from the naval architecture community, because of the recent development of electric propulsion drives and podded propulsors. Contrarotating propulsion systems have the hydrodynamic advantages of recovering part of the slipstream rotational energy which would otherwise be lost utilizing a conventional screw propeller system. The application of this type of propulsion becomes even more attractive with the increasing emphasis on fuel economy and the improvement of the propulsive efficiency. OPENPROP is an open source propeller design and analysis code that has been in development at MIT since 2007. This thesis adds another feature to the project with the off design analysis of a contra-rotating propeller set. Based on this code, the thesis offers a comparative analysis of two types of propulsors: a single propeller and a contra-rotating propeller set, which were designed for the DDG-51 destroyer class vessel. This thesis also presents the method for using these off-design analysis results to estimate ship powering requirements and fuel usage. The results show the superiority of the contra-rotating propeller over the traditional single propeller, with increased propeller efficiency of about 9% at the design point and up to 20% at some of the off design states. The annual fuel consumption savings for the DDG-51 equipped with a CRP was a total of 8.8% fuel savings.

Book Unsteady Force Measurement Using Small Piezoelectric End Sensors

Download or read book Unsteady Force Measurement Using Small Piezoelectric End Sensors written by Margalit Goldschmidt and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Most marine propellers operate in a nonuniform flow field. Understanding the unsteady lift generated on the propeller blades by these upstream wakes is important in order to reduce vibration and noise and therefore develop more efficient turbomachines. Currently, complex instrumentation involving unsteady dynamometry and pressure sensor arrays are utilized to characterize the unsteady pressures across propeller blades. New, simpler sensors have been designed to replace current instrumentation. These sensors take advantage of the oscillating nature of the unsteady lift, as at increasing inflow harmonics the rapidity of the unsteady lift fluctuations suggests that the lift nearly cancels out over the blade radius, and that the total unsteady force across a propeller blade can be found from parameters at the root and tip. These parameters were determined from an approximation provided by the Method of the Stationary Phase. Using this method, new sensors were designed and optimized to work universally. The newly designed sensors will be validated in a future experiment.