Experimental Studies on Cooling Effectiveness of the Double-Decker Air Jet Impingement With Film Outflow

Experiments were carried out to investigate the cooling effectiveness of a lamellar double-decker impingement/effusion structure. Infrared radiation (I.R.) thermal camera was used to measure the temperature on the outside surface of the lamellar double-decker. Experimental results were obtained for a wide range of governing parameters (blowing rate M (0.0017∼0.0066), the ratio of the jet impingement distance to the diameter of film hole H/D (0.5∼1.25), the ratio of the distance between the jet hole and film hole to the diameter of the film hole P/D (0, 3, 4), and the material of double-decker (Steel and Copper)). It was observed that the local cooling effectiveness η varies with all these parameters in a complicated way. All the results show that higher cooling effectiveness η is achieved in larger blowing rate cases. A certain range of H/D and P/D can be designed to result in the maximum cooling effectiveness η. And η is less sensitive to the material type compared with those parameters such as H/D, M and P/D.

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Experimental investigations of a double-decker jet impingement/film structure's cooling effectiveness

Heat Transfer-Asian Research ◽

10.1002/htj.20199 ◽

2008 ◽

Vol 37 (4) ◽

pp. 232-239

Author(s):

Zhenxiong Liu ◽

Junkui Mao ◽

Wen Guo ◽

Hefu Jiang

Keyword(s):

Jet Impingement ◽

Experimental Investigations ◽

Cooling Effectiveness ◽

Double Decker

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A New Analytical Model of a Centrifugal Compressor and Validation by Experiments

Journal of Mechanics ◽

10.1017/s1727719100003701 ◽

2010 ◽

Vol 26 (1) ◽

pp. 37-45 ◽

Cited By ~ 1

Author(s):

H. Pourfarzaneh ◽

A. Hajilouy-Benisi ◽

M. Farshchi

Keyword(s):

Conceptual Design ◽

Centrifugal Compressor ◽

Experimental Studies ◽

Design Tool ◽

Operating Conditions ◽

Experimental Results ◽

Design Phase ◽

Robust Model ◽

Conceptual Design Phase ◽

Wide Range

AbstractIn the conceptual design phase of a turbocharger, where emphasis is mainly on parametric studies, before manufacturing and tests, a generalized and robust model that implies over a wide range properly, is unavoidable. The critical inputs such as compressor maps are not available during the conceptual design phase. Hence, generalized compressor models use alternate methods that work without any supplementary tests and can operate on wide range. One of the common and applicable modeling methods in design process is the ‘Dimensionless Modeling’ using the constant coefficient scaling (CCS). This method almost can predict the compressor characteristics at design point. However, at off design conditions, error goes up as mass flow and speed parameters increase. Therefore, the results are not reliable at these points. In this paper, a variable coefficient scaling (VCS) method is described. Then, a centrifugal compressor is modeled using the VCS method. To evaluate the model and compare it with the experimental results, some supplementary experiments are performed. Experimental studies are carried out on the compressor of a S2B model of the Schwitzer turbocharger in the turbocharger Lab., at Sharif University of Technology. The comparison between the experimental results and those obtained by the VCS method indicates a good agreement. It also suggests that the present model can be used as an effective design tool for all operating conditions.

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Elastohydrodynamic Film Thickness in Concentrated Contacts: Part 2: Correlation of Experimental Results with Elastohydrodynamic Theory

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/pime_proc_1986_200_117_02 ◽

1986 ◽

Vol 200 (3) ◽

pp. 219-226 ◽

Cited By ~ 1

Author(s):

R J Chittenden ◽

D Dowson ◽

C M Taylor

Keyword(s):

Film Thickness ◽

Experimental Studies ◽

Elastohydrodynamic Lubrication ◽

Operating Conditions ◽

Experimental Results ◽

Experimental Techniques ◽

Dimensionless Parameters ◽

Wide Range ◽

Theoretical Predictions ◽

Computational Procedures

The existence of a coherent film of lubricant between highly loaded machine elements has been recognized for many years. Over this period of time measurements of film thickness have gone hand in hand with theoretical analyses in the field now known as elastohydrodynamic lubrication. The experimental techniques of capacitance, electrical resistance and X-ray measurement have been supplemented by the use of optical interferometry while the analytical expressions obtained with the use of elegant simplifications have been superseded by those developed from extensive and comprehensive computational procedures. These developments in experimental techniques have yielded a substantial number of measurements of both minimum and central film thickness. Likewise, the advent of the digital computer has allowed the derivation of a large number of solutions to the problem of elastohydrodynamic lubrication of concentrated contacts. All these results, covering a wide range of geometrical conditions, are to be found in the literature, yet little attempt appears to have been made to assemble a representative set of experimental data to permit a detailed evaluation of the theoretical formulae for elliptical contacts. The second part of this paper therefore considers the correlation between a number of experimental studies covering a wide range of operating conditions and geometries, and the predictions of recent elastohydrodynamic theory. Some of the important aspects of each set of experimental results are then considered and examples are provided which illustrate the following points: 1. Good estimates of lubricant film thickness may be obtained from the theoretical expressions recently derived, even when the dimensionless parameters involved are outside the ranges considered in the derivation of the formulae. 2. The discrepancies which exist between theoretical predictions and some of the measured film thicknesses are nevertheless quite large, even when the dimensionless parameters are within their usual limits. On the whole there is good agreement between experiment and theory, while the general trend of the results indicates that theoretical predictions may underestimate the minimum film thickness by about 10 per cent and the central film thickness by about 25 per cent. This measure of agreement is quite remarkable when the extreme difficulty of interpreting the magnitudes of effective and very thin mean film thicknesses between machined components in various forms of experimental equipment is considered.

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Measurement Errors and Uncertainty Quantification of a 2D-PIV Experimental Setup for Jet Flow Characterization

ASCE-ASME J Risk and Uncert in Engrg Sys Part B Mech Engrg ◽

10.1115/1.4047649 ◽

2020 ◽

Author(s):

Flavia Barbosa ◽

Carlos Costa ◽

Senhorinha Teixeira ◽

Jose Carlos Teixeira

Keyword(s):

Heat Transfer ◽

Uncertainty Quantification ◽

Measurement Errors ◽

Jet Impingement ◽

Velocity Fields ◽

Mean Velocity ◽

Air Jets ◽

Air Jet ◽

High Heat Transfer ◽

Wide Range

Abstract The study of the flow interaction and the heat transfer between air jets and a surface is of paramount importance in industrial processes that apply air jet impingement. To ensure a good performance of the process, high heat transfer rates and uniformization of the flow over the target plate are required. To perform this analysis, a PIV technique was implemented for the measurement of the flow velocity fields. However, as any real experiment, the values recorded by the PIV method are subjected to several errors that compromise the reliability and accuracy of the measurements. These errors can have different sources, from the installation and alignment to the particles seeding and calibration procedure. To maximize the accuracy of the experimental results, this paper focus on the identification of measurement errors and uncertainty quantification of an experimental set up specially built for the analysis of the interaction between air jets and a target surface. This work presents an analysis of the system, and the source of errors are identified, quantified and, when possible, corrected. The particle seeding is characterized and its efficiency for the flow tracking is analyzed. The setup was tested to fully characterize the flow field in terms of mean velocity profile and turbulence intensity over a wide range of Reynolds numbers and temperature. Several velocity fields are then measured until convergence of the flow quantities is reached. The combination of these measurements with high spatial resolution and low measurement errors allow to obtain accurate and precise measurements.

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COLUMN BUCKLING TESTS OF 420 MPA HIGH STRENGTH STEEL SINGLE EQUAL ANGLES

International Journal of Structural Stability and Dynamics ◽

10.1142/s0219455412500691 ◽

2013 ◽

Vol 13 (02) ◽

pp. 1250069 ◽

Cited By ~ 21

Author(s):

H. Y. BAN ◽

G. SHI ◽

Y. J. SHI ◽

Y. Q. WANG

Keyword(s):

High Strength Steel ◽

Experimental Studies ◽

High Strength ◽

Experimental Results ◽

Test Results ◽

Design Strength ◽

Buckling Modes ◽

Wide Range ◽

Current Design ◽

Design Values

This paper presents the results of the experimental studies conducted on the buckling behavior of 420 MPa high strength steel, hot-rolled, equal angle columns, numbering a total of 66 specimens with a wide range of column slenderness and section sizes. Based on the test results, the buckling modes and capacities were analyzed and the nondimensional buckling strengths were obtained and compared with the design strength predicted from Eurocode 3, ANSI/AISC 360-10 and Chinese standards GB50017-2003. The experimental results in previous studies were also employed in the comparison. The effect of width to thickness ratio of legs of an angle on buckling modes and strengths were investigated. It was found that the buckling strengths from test results were much higher than the corresponding design values and current design approaches were too conservative. Based on present and previous experimental results, a new design approach is suggested for the design of angle columns with 420 MPa high strength steel.

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Numerical Study on Performance of Surface Piercing Propeller using RANS Approach

10.5957/fast-2015-044 ◽

2015 ◽

Author(s):

Kohei Himei ◽

Hajime Yamaguchi

Keyword(s):

Standardized Test ◽

Numerical Study ◽

High Reliability ◽

Experimental Studies ◽

Performance Estimation ◽

Experimental Results ◽

Ventilated Cavitation ◽

Wide Range ◽

Physical Phenomena ◽

Surface Piercing Propeller

Surface Piercing Propeller (SPP) can achieve high propulsive efficiency on high-speed vessels planing to reduce the frictional resistance of hull. It has the characteristic blade section and works partially submerged condition. The blades repeat entry to and exit from the water free surface and the suction sides and trailing edge of blades are exposed to ventilated cavitation while they are under the water. And interface near SPP is severely deformed by the high rotating blades. This working condition of SPP, therefore, makes it hard that propeller open characteristics are estimated with high reliability. Because SPP is unusual propeller having above difficulty of the performance estimation, the studies for SPP are few compared with large sized propellers for merchant ships. Although the various model tests had been carried out to understand the physical phenomena around various SPPs and their effects on propeller performances, they were not universal approach with standardized test conditions and propeller shape, as mentioned in 23th ITTC report and recommendation (2002). In applying the conventional calculation based on potential theory to SPP, there are many difficulties to model the physical phenomena theoretically. In calculations by Furuya (1984, 1985), thickness of blade and ventilated cavitation were non-consideration, and it was assumed that the suction side of the blade was fully ventilated in the water. In calculations by Young and Kinnas (2001), the interface deformation near SPP was not modeled theoretically. Therefore, they attributed the difference from experimental results to the effect of incompleteness of numerical modeling. On the other hand, CFD analysis can treat the effects of physical phenomena including thick ventilated cavitation and the sharp deformation of interface around SPP. In addition, the characteristic blade shape is modeled accurately without the geometric limitation in CFD. In this paper, typical SPP with experimental results open to the public is analyzed by CFD-RANS approach using Volume of Fluid (VOF) method based on interface-capturing algorithm at wide range of propeller advance coefficient J. Regarding propeller open characteristics, the 6-component force/moment fluctuations by blade rotations, and ventilation patterns, analyses results are compared with measured values. Moreover, the results of simulations in various Froude numbers and Weber numbers are evaluated whether their effects were negligible when they are sufficiently high, in the same manner as the results found by the other’s experimental studies (Shiba, 1953; Brandt, 1973).

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On the nominal transverse shear strain to characterize the severity of creasing

TAPPI Journal ◽

10.32964/tj17.04.231 ◽

2018 ◽

Vol 17 (04) ◽

pp. 231-240

Author(s):

Douglas Coffin ◽

Joel Panek

Keyword(s):

Shear Strain ◽

Transverse Shear ◽

Elastic Limit ◽

Experimental Results ◽

Transverse Shear Strain ◽

Maximum Strain ◽

Machine Direction ◽

Engineering Approach ◽

Wide Range ◽

Analytic Expression

A transverse shear strain was utilized to characterize the severity of creasing for a wide range of tooling configurations. An analytic expression of transverse shear strain, which accounts for tooling geometry, correlated well with relative crease strength and springback as determined from 90° fold tests. The experimental results show a minimum strain (elastic limit) that needs to be exceeded for the relative crease strength to be reduced. The theory predicts a maximum achievable transverse shear strain, which is further limited if the tooling clearance is negative. The elastic limit and maximum strain thus describe the range of interest for effective creasing. In this range, cross direction (CD)-creased samples were more sensitive to creasing than machine direction (MD)-creased samples, but the differences were reduced as the shear strain approached the maximum. The presented development provides the foundation for a quantitative engineering approach to creasing and folding operations.

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GENERATION AND PROPERTIES OF INFRARED RADIATION

Computational nanotechnology ◽

10.33693/2313-223x-2019-6-2-101-137 ◽

2019 ◽

Vol 6 (2) ◽

pp. 101-137

Author(s):

RUSTAM KHAKIMOVICH RAKHIMOV

Keyword(s):

Electromagnetic Radiation ◽

Infrared Radiation ◽

Radiation Spectrum ◽

Laws Of Nature ◽

Primary Source ◽

Ceramic Materials ◽

Experimental Results ◽

Ir Radiation ◽

Scattering Of Light

The article presents the main basic laws of nature and modern theories of the nature of electromagnetic radiation, its generation, characteristics, and laws of reflection, absorption and scattering of light. The principle of transformation of the radiation spectrum of the primary source using the developed ceramic materials are shown, as well as experimental results of the interaction of IR radiation with matter and various mechanisms of influence on various objects and processes are described.

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Image Statistics Preserving Encrypt-then-Compress Scheme Dedicated for JPEG Compression Standard

Entropy ◽

10.3390/e23040421 ◽

2021 ◽

Vol 23 (4) ◽

pp. 421

Author(s):

Dariusz Puchala ◽

Kamil Stokfiszewski ◽

Mykhaylo Yatsymirskyy

Keyword(s):

Statistical Analysis ◽

Image Encryption ◽

Experimental Studies ◽

Quality Measures ◽

Input Image ◽

Jpeg Compression ◽

Image Statistics ◽

Compression Stage ◽

Wide Range ◽

The Impact

In this paper, the authors analyze in more details an image encryption scheme, proposed by the authors in their earlier work, which preserves input image statistics and can be used in connection with the JPEG compression standard. The image encryption process takes advantage of fast linear transforms parametrized with private keys and is carried out prior to the compression stage in a way that does not alter those statistical characteristics of the input image that are crucial from the point of view of the subsequent compression. This feature makes the encryption process transparent to the compression stage and enables the JPEG algorithm to maintain its full compression capabilities even though it operates on the encrypted image data. The main advantage of the considered approach is the fact that the JPEG algorithm can be used without any modifications as a part of the encrypt-then-compress image processing framework. The paper includes a detailed mathematical model of the examined scheme allowing for theoretical analysis of the impact of the image encryption step on the effectiveness of the compression process. The combinatorial and statistical analysis of the encryption process is also included and it allows to evaluate its cryptographic strength. In addition, the paper considers several practical use-case scenarios with different characteristics of the compression and encryption stages. The final part of the paper contains the additional results of the experimental studies regarding general effectiveness of the presented scheme. The results show that for a wide range of compression ratios the considered scheme performs comparably to the JPEG algorithm alone, that is, without the encryption stage, in terms of the quality measures of reconstructed images. Moreover, the results of statistical analysis as well as those obtained with generally approved quality measures of image cryptographic systems, prove high strength and efficiency of the scheme’s encryption stage.

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