EVALUATION OF CAVITATION PERFORMANCE OF AN AXI-SYMMETRIC BODY WITH PUMPJET PROPULSOR

2021 ◽  
Vol 152 (A3) ◽  
Author(s):  
Ch Suryanarayana ◽  
M Nageswara Rao ◽  
B Suryanarayana ◽  
K Ramji
Keyword(s):  
Technology Development ◽  
Development Program ◽  
Suction Side ◽  
Model Tests ◽  
Test Results ◽  
Cavitation Inception ◽  
Cavitation Performance ◽  
Study Evaluation ◽  
Cavitation Tunnel ◽  
Face Side

A Pumpjet (PJP) was designed for an underwater body (UWB) with an axi-symmetric configuration as part of a technology development program for design and development of pumpjet. Its propulsive and cavitation performances were predicted through CFD study. The propulsor design was evaluated for its propulsion characteristics through model tests conducted in a Wind Tunnel. In the concluding part of the study, evaluation of the cavitation performance of the pumpjet was undertaken in a Cavitation Tunnel (CT). In order to assess the cavitation free operational speeds and depths of the vehicle with respect to pumpjet, cavitation tests of the PJP were carried out in behind condition at CT to determine the cavitation inception numbers for rotor, stator and cowl. The model test results obtained were corrected for full scale Reynolds number and subsequently analyzed for cavitation inception speeds at different operating depths. This entire exercise facilitated the development of an innovative testing technique and a special test setup for finding cavitation performance of pumpjet propulsor. The technique was evaluated by comparative corroboration of inception position and depth obtained from CFD analysis. From the model tests it was also found that the cavitation inception of the rotor takes place on the tip face side at higher advance ratios and cavitation shifts towards the suction side as the shaft rotation rate increases whereas the stator and cowl are free from any cavitation.

scholarly journals Analysis of Bulb Turbine Hydrofoil Cavitation

2021 ◽  
Vol 11 (6) ◽  
pp. 2639
Author(s):  
Andrej Podnar ◽  
Marko Hočevar ◽  
Lovrenc Novak ◽  
Matevž Dular
Keyword(s):  
Regression Model ◽  
Flow Characteristics ◽  
Suction Side ◽  
Cavitation Number ◽  
Design Parameters ◽  
Cavitation Inception ◽  
Measuring Station ◽  
Runner Blade ◽  
Cavitation Tunnel ◽  
Bulb Turbine

The influence of a bulb runner blade hydrofoil shape on flow characteristics around the blade was studied. Experimental work was performed on a bulb turbine measuring station and a single hydrofoil in a cavitating tunnel. In the cavitation tunnel, flow visualization was performed on the hydrofoil’s suction side. Cavitation structures were observed for several cavitation numbers. Cavitation was less intense on the modified hydrofoil than on the original hydrofoil, delaying the cavitation onset by several tenths in cavitation number. The results of the visualization in the cavitation tunnel show that modifying the existing hydrofoil design parameters played a key role in reducing the cavitation inception and development, as well as the size of the cavitation structures. A regression model was produced for cavitation cloud length. The results of the regression model show that cavitation length is dependent on Reynolds’s number and the cavitation number. The coefficients of determination for both the existing and modified hydrofoils were reasonably high, with R2 values above 0.95. The results of the cavitation length regression model also confirm that the modified hydrofoil exhibits improved the cavitation properties.

scholarly journals Influence of wall roughness on cavitation performance of centrifugal pump

2021 ◽  
Vol 43 (6) ◽  
Author(s):  
Weihui Xu ◽  
Xiaoke He ◽  
Xiao Hou ◽  
Zhihao Huang ◽  
Weishu Wang
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Internal Flow ◽  
Wall Roughness ◽  
Blade Surface ◽  
Centrifugal Pumps ◽  
Three Dimensional Model ◽  
Cavitation Inception ◽  
Cavitation Performance ◽  
Critical Cavitation

AbstractCavitation is a phenomenon that occurs easily during rotation of fluid machinery and can decrease the performance of a pump, thereby resulting in damage to flow passage components. To study the influence of wall roughness on the cavitation performance of a centrifugal pump, a three-dimensional model of internal flow field of a centrifugal pump was constructed and a numerical simulation of cavitation in the flow field was conducted with ANSYS CFX software based on the Reynolds normalization group k-epsilon turbulence model and Zwart cavitation model. The cavitation can be further divided into four stages: cavitation inception, cavitation development, critical cavitation, and fracture cavitation. Influencing laws of wall roughness of the blade surface on the cavitation performance of a centrifugal pump were analyzed. Research results demonstrate that in the design process of centrifugal pumps, decreasing the wall roughness appropriately during the cavitation development and critical cavitation is important to effectively improve the cavitation performance of pumps. Moreover, a number of nucleation sites on the blade surface increase with the increase in wall roughness, thereby expanding the low-pressure area of the blade. Research conclusions can provide theoretical references to improve cavitation performance and optimize the structural design of the pump.

Consolidation of cement-treated sewage sludge using vertical drains

2005 ◽  
Vol 42 (2) ◽  
pp. 528-540 ◽  
Author(s):  
J Chu ◽  
M H Goi ◽  
T T Lim
Keyword(s):  
Sewage Sludge ◽  
Land Reclamation ◽  
Model Tests ◽  
Waste Materials ◽  
Test Results ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Treated Sewage ◽  
The World

The disposal of sewage sludge and other waste materials has become a problem in many cities around the world. A study on the use of sewage sludge and other waste materials for land reclamation has been conducted. One of the methods studied is to dispose of the sludge after it has been mixed with binders or other waste materials and then to consolidate the mixture on site using surcharge and prefabricated vertical drains (PVDs). To study the consolidation behaviour of the sludge–binder mixtures around PVDs, model tests using a fully instrumented consolidation tank were conducted. Some of the test results are presented in this paper. The study shows that PVDs are effective in consolidating the sludge and binder mixtures, provided that the PVDs used can sustain large bending and resist corrosion by the chemicals in the sludge.Key words: consolidation, geoenvironmental, land reclamation, prefabricated vertical drains.

scholarly journals Emission Reduction of Fuel-Staged Aircraft Engine Combustor Using an Additional Premixed Fuel Nozzle

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Takeshi Yamamoto ◽  
Kazuo Shimodaira ◽  
Seiji Yoshida ◽  
Yoji Kurosawa
Keyword(s):  
Technology Development ◽  
Pressure Ratio ◽  
Aircraft Engine ◽  
Development Project ◽  
Civil Aviation ◽  
Test Results ◽  
Technology Development Project ◽  
Fuel Nozzle ◽  
Conducting Research ◽  
Japan Aerospace Exploration Agency

The Japan Aerospace Exploration Agency (JAXA) is conducting research and development on aircraft engine technologies to reduce environmental impact for the Technology Development Project for Clean Engines (TechCLEAN). As a part of the project, combustion technologies have been developed with an aggressive target that is an 80% reduction over the NOx threshold of the International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP)/4 standard. A staged fuel nozzle with a pilot mixer and a main mixer was developed and tested using a single-sector combustor under the target engine's landing and takeoff (LTO) cycle conditions with a rated output of 40 kN and an overall pressure ratio of 25.8. The test results showed a 77% reduction over the CAEP/4 NOx standard. However, the reduction in smoke at thrust conditions higher than the 30% MTO condition and of CO emission at thrust conditions lower than the 85% MTO condition are necessary. In the present study, an additional fuel burner was designed and tested with the staged fuel nozzle in a single-sector combustor to control emissions. The test results show that the combustor enables an 82% reduction in NOx emissions relative to the ICAO CAEP/4 standard and a drastic reduction in smoke and CO emissions.

Launching of Ships and Floating Structures from Horizontal Berth by Tipping Table

1998 ◽  
Vol 14 (04) ◽  
pp. 265-276
Author(s):  
Ivo Senjanovic
Keyword(s):  
Structural Dynamics ◽  
Review Paper ◽  
Offshore Structures ◽  
Model Tests ◽  
Full Scale ◽  
Strength Analysis ◽  
Test Results ◽  
Floating Structures ◽  
Measurement Results

This review paper covers extensive investigations which were undertaken in order to verify the idea of launching of ships and other floating structures from a horizontal berth by a set of turning pads. This includes structural dynamics during launching, model tests and strength analysis of the structure and the launching system. The most important results, which were used for the design of the launching system, are presented. The preparation of a barge for side launching is described, and the full-scale measurement results are compared with the test results. The advantages of building ships and offshore structures on a horizontal berth are pointed out in the conclusion.

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