<title>Theoretical And Experimental Investigations For The Driving-Mechanism Of A Large-Diameter Shock Simulator</title>

Ensuring pipeline stability is a fundamental aspect of subsea pipeline design and can contribute a significant proportion of project costs in regions with large diameter trunklines, shallow water and severe geotechnical and metocean conditions [1]. Reducing the conservatism and simplifications of existing pipeline stabilisation design methods therefore offers economic benefits to hydrocarbon producers necessary to ensure the ongoing viability of projects in these regions. To realise this potential and reduce the conservatism of the existing design methods, a more accurate understanding of the hydrodynamic loads exerted by waves and currents is required. This paper investigates one of the inherent assumptions incorporated into the existing design methods through the arrangement of previous experimental investigations to determine whether rectilinear motion provides a reasonable approximation to simulate the near seabed orbital particle paths in wind-generated waves. This assumption is based on the flattening of particle paths to ellipsoids with depth and ignores the small vertical velocity components near the seabed. Based on the hydrodynamic forces calculated numerically using a validated Computational Fluid Dynamics (CFD) model for rectilinear and orbital wave modelling it is concluded that pipeline stabilisation requirements calculated in accordance with the DNV-RP-F109 absolute lateral static stability design method and rectilinear wave motion assumption are conservative. It is also concluded that the hydrodynamic force asymmetry in favour of the reverse half wave cycle caused by the vertical velocity components in orbital wave conditions requires further consideration to determine the implication for dynamic lateral stability design methods.

Download Full-text

Experimental Investigation of Steam Bubble Condensation in Flowing Subcooled Water With Two Different Injection Nozzle Geometries

Volume 4: Thermal Hydraulics ◽

10.1115/icone21-16494 ◽

2013 ◽

Author(s):

Suleiman Al Issa ◽

Patricia B. Weisensee

Keyword(s):

Test Section ◽

High Speed ◽

Nuclear Power ◽

Power Plants ◽

Bubble Diameter ◽

Large Diameter ◽

Low Pressure ◽

Test Facility ◽

Experimental Investigations ◽

Subcooled Water

A multiphase flow test facility was built at the Department of Nuclear Engineering at the Technical University Munich. The main goal of this facility is to investigate the condensation of steam bubbles injected into a vertical large diameter pipe (104 mm) with flowing subcooled water (6–15 K) at low pressure conditions (1.1–1.45 bar). Current experimental investigations will contribute to a better understanding of subcooled boiling at low pressures, accidental conditions in nuclear power plants and low-pressure research reactors and correlations for the validation of CFD codes. The test section is a 1 m long transparent pipe that is surrounded by an 18×18 cm rectangular “aquarium” filled with distilled water for refraction correction. High-speed camera (HSC) recording was used to gather data about condensing bubbles including bubble diameter, shape and rising velocity. Steam was injected via two different vertical injection nozzles with an inner diameter of 4 and 6 mm, respectively, directly into the center of the test section. The present experiments were carried out at three different steam superficial velocities, water superficial velocities and water temperatures leading to bubble diameters up to 50 mm and bubble relative velocities around 1 m/s. The measurements enabled the calculation of bubble Reynolds and Nusselt numbers and comparison with correlations given in literature. Even though significant differences could be observed between the two injection nozzles with respect to the bubble’s diameter and velocity, the Nusselt and Reynolds numbers are in the same range of values. The bigger bubbles of the 6 mm with respect to the 4 mm nozzle are almost neutralized by the lower rising velocities.

Download Full-text

Effect of Tip Vortex Reduction on Air-Cooled Condenser Axial Flow Fan Performance: An Experimental Investigation

10.1115/gt2021-58735 ◽

2021 ◽

Author(s):

J. P. Pretorius ◽

J. A. Erasmus

Keyword(s):

Performance Test ◽

Performance Enhancement ◽

Large Diameter ◽

Pressure Coefficient ◽

Axial Flow ◽

Tip Clearance ◽

Flow Coefficient ◽

Tip Vortex ◽

Experimental Investigations ◽

Fan Performance

Abstract Large diameter axial flow fans are used in Air-cooled Condenser (ACC) systems of modern power stations. Efficiency improvements on these fans can significantly reduce the ACC power consumption and increase the net sent-out power to the grid. This study targets fan performance enhancement through blade tip vortex reduction. Experimental investigations are performed on a representative ACC scale fan, where tests consider the effects of tip clearance and two new tip endplate designs on fan performance. Test results confirm the findings of previous studies, showing the negative effect of increasing tip clearance on performance. Despite testing limitations, results from tests incorporating endplates show fan static pressure coefficient and efficiency increases over large ranges of flow coefficient compared to the datum fan. These outcomes agree with observations from literature and warrants further exploration. Future work is recommended to provide confirmation on the presented trends.

Download Full-text

Interaction of phase transformation and magneto- and elastocaloric properties of Heusler alloys

MRS Proceedings ◽

10.1557/opl.2013.720 ◽

2013 ◽

Vol 1581 ◽

Cited By ~ 1

Author(s):

Peter Entel ◽

Vladimir V. Sokolovskiy ◽

Vasiliy D. Buchelnikov ◽

Denis Comtesse ◽

Mehmet Acet

Keyword(s):

Monte Carlo ◽

Shape Memory ◽

Ab Initio ◽

Heusler Alloys ◽

Magnetic Ordering ◽

Magnetic Behavior ◽

Experimental Investigations ◽

Driving Mechanism ◽

Magnetic Shape Memory ◽

Magnetic Exchange

ABSTRACTThe structural, electronic and magnetic properties of functional Ni-Mn-(Ga, In, Sn) and Pt-Ni-(Ga, Sn) alloys are studied by first-principles and Monte Carlo tools. The ab initio calculations give a basic understanding of the underlying physics which is associated with the complex magnetic behavior arising from the competition of ferro- and antiferromagnetic interactions for excess Mn atoms in the unit cell. We show that the resulting complex magnetic ordering is the driving mechanism of structural transformations and multifunctional properties of Heusler alloys associated with magnetic shape-memory, magnetocaloric and elastocaloric effects. The thermodynamic properties can be calculated by using the ab initio magnetic exchange parameters in finite-temperature Monte Carlo simulations. Entropy and specific heat changes associated with the magnetic changes and emergence of microstructure across the magnetostructural transition are pointed out. We show how to optimize the functional properties by tuning the compositional changes, for example, a magnetic shape-memory effect of more than 14% can be achieved in Pt-Ni-Mn-Ga alloys. The theoretical studies are accompanied by experimental investigations.

Download Full-text

A Driving Mechanism for High Frequency Combustion Instability in Liquid Fuel Rocket Engines

Journal of the Royal Aeronautical Society ◽

10.1017/s0368393100080433 ◽

1964 ◽

Vol 68 (645) ◽

pp. 633-637 ◽

Cited By ~ 5

Author(s):

P. D. McCormack

Keyword(s):

High Frequency ◽

Liquid Fuel ◽

Low Frequency ◽

Pressure Oscillation ◽

Experimental Investigations ◽

Driving Mechanism ◽

Rocket Engines ◽

High Frequency Oscillations ◽

The Subject ◽

Motor Operation

The problem of combustion pressure oscillation in liquid-fuel rocket motor operation has long been the subject of theoretical and experimental investigations.The low frequency (less than 200 cps) type of oscillation, known as “chugging”, has been thoroughly analysed and the problem solved (see Crocco, 5th Combustion Symposium, p. 164).This Note is concerned with the more complex (and more destructive) high frequency oscillations, covering a range from about 1000 to 6000 cps. Such oscillations can resonate with the acoustical modes of the combustion chamber. Longitudinal, tangential and radial oscillating modes have been observed.

Download Full-text

Numerical and experimental investigations on large-diameter gear rolling with local induction heating process

The International Journal of Advanced Manufacturing Technology ◽

10.1007/s00170-016-9713-y ◽

2016 ◽

Vol 91 (1-4) ◽

pp. 1-11 ◽

Cited By ~ 17

Author(s):

Xiaobin Fu ◽

Baoyu Wang ◽

Xiaoxing Zhu ◽

Xuefeng Tang ◽

Hongchao Ji

Keyword(s):

Induction Heating ◽

Large Diameter ◽

Experimental Investigations ◽

Heating Process ◽

Gear Rolling

Download Full-text

Effect of Tip Vortex Reduction on Air-Cooled Condenser Axial Flow Fan Performance: an Experimental Investigation

Journal of Turbomachinery ◽

10.1115/1.4052234 ◽

2021 ◽

pp. 1-28

Author(s):

J.P. Pretorius ◽

Johan A Erasmus

Keyword(s):

Performance Test ◽

Performance Enhancement ◽

Large Diameter ◽

Pressure Coefficient ◽

Axial Flow ◽

Tip Clearance ◽

Flow Coefficient ◽

Tip Vortex ◽

Experimental Investigations ◽

Fan Performance

Abstract Large diameter axial flow fans are used in Air-cooled Condenser (ACC) systems of modern power stations. Efficiency improvements on these fans can significantly reduce the ACC power consumption and increase the net sent-out power to the grid. This study targets fan performance enhancement through blade tip vortex reduction. Experimental investigations are performed on a representative ACC scale fan, where tests consider the effects of tip clearance and two new tip endplate designs on fan performance. Test results confirm the findings of previous studies, showing the negative effect of increasing tip clearance on performance. Despite testing limitations, results from tests incorporating endplates show fan static pressure coefficient and efficiency increases over large ranges of flow coefficient compared to the datum fan. These outcomes agree with observations from literature and warrants further exploration. Future work is recommended to provide confirmation on the presented trends.

Download Full-text

Development of a digital SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010008609x ◽

1991 ◽

Vol 49 ◽

pp. 358-359

Author(s):

A. Yamada ◽

A. Shibano ◽

K. Harasawa ◽

T. Kobayashi ◽

H. Fukuda ◽

...

Keyword(s):

Large Diameter ◽

Objective Lens ◽

Large Specimen ◽

Backscattered Electrons ◽

Digital Scanning ◽

Junction Type ◽

High Resolution Images ◽

Working Distance ◽

Type Detector ◽

Short Working

A newly developed digital scanning electron microscope, the JSM-6300, has the following features: Equipped with a narrower conical objective lens (OL), it allows high resolution images to be obtained easily at a short working distance (WD) and a large specimen tilt angle. In addition, it is provided with automatic functions and digital image processing functions for ease of operation.Conical C-F lens: The newly developed conical C-F objective lens, having low aberration characteristics over a wide WD range, allows a large-diameter (3-inch) specimen to be tilted up to 60° at short WD, and provides images with low magnifications starting at 10*. On the bottom of the lens, a p n junction type detector is provided to detect backscattered electrons (BE) from the specimen. As the narrower conical 0L increases the secondary electron (SE) detector's field intensity on the specimen surface, high SE image quality is obtained.

Download Full-text