scholarly journals Influence of Holes Manufacture Technology on Perforated Plate Aerodynamics

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6624
Author(s):  
Joanna Grzelak ◽  
Ryszard Szwaba
Keyword(s):  
Gas Turbines ◽  
Perforated Plate ◽  
Flow Characteristics ◽  
Aerodynamic Characteristics ◽  
Physical Models ◽  
Experimental Investigations ◽  
Perforated Plates ◽  
Flow Losses ◽  
Large Numbers

Transpiration flow is a very important and still open subject in many technical applications. Perforated walls are useful for the purpose of “flow control”, as well as for the cooling of walls and blades (effusive cooling) in gas turbines. We are still not able to include large numbers of holes in the numerical calculations and therefore we need physical models. Problems are related also to the quality of the holes in perforated plates. The present transpiration analysis concerns with experimental investigations of the air flow through perforated plates with microholes of 125 and 300 µm diameters. A good accordance of the results with other experiments, simulations and theory was obtained. The received results very clearly show that technology manufacturing of plate holes influences on their aerodynamic characteristics. It turned out that the quality of the plate microholes using laser technology and, consequently, the shape of the hole, can affect the flow losses. Therefore, this effect was investigated and the flow characteristics in both directions were measured, i.e., for two plate settings.

Unsteady 3D-Numerical Investigation of the Influence of the Blading Design on the Stator-Rotor Interaction in a 2-Stage Turbine

2005 ◽  
Author(s):  
Dieter E. Bohn ◽  
Jing Ren ◽  
Christian Tu¨mmers ◽  
Michael Sell
Keyword(s):  
Gas Turbines ◽  
Flow Characteristics ◽  
Computer Code ◽  
Experimental Investigations ◽  
Blade Design ◽  
Test Rig ◽  
3D Flow ◽  
Two Stage ◽  
Flow Phenomena ◽  
Flow Through

An important goal in the development of turbine bladings is improving their efficiency to achieve an optimized usage of energy resources. This requires a detailed insight into the complex 3D-flow phenomena in multi-stage turbines. In order to investigate the flow characteristics of modern highly loaded turbine profiles, a test rig with a two-stage axial turbine has been set up at the Institute of Steam and Gas Turbines, Aachen University. The test rig is especially designed to investigate different blading designs. In order to analyze the influence of the blade design on the unsteady blade row interaction, the 3D flow through the two-stage turbine is simulated numerically, using an unsteady Navier-Stokes computer code. The investigations include a comparison of two bladings with different design criteria. The reference blading is a commonly used cylindrical designed blading. This blade design will be compared with a bow-blading, which is designed to minimize the secondary flow phenomena near the endwall in order to achieve a balanced mass flow through nearly the whole passage height. The investigations will focus on the different loss behavior of the two bladings. Unsteady profile pressure distributions and radial efficiencies of the two blade designs will be discussed in detail. The flow conditions are taken from experimental investigations performed at the Institute of Steam and Gas Turbines. On the basis of the experiments a validation of the code will be performed by comparing the numerical results to the corresponding experimental data at the inlet and the outlet of the blading.

Analysis of Fluid Flow and Heat Transfer in Corrugated Perforated Plate Fin Heat Sinks

2021 ◽  
pp. 1-30
Author(s):  
Shripad A Upalkar ◽  
Saksham Gakhar ◽  
Shankar Krishnan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Dissipation ◽  
Single Channel ◽  
Perforated Plate ◽  
Flow Characteristics ◽  
Flow Distribution ◽  
Optimum Number ◽  
Perforated Plates ◽  
Optimum Diameter

Abstract This paper reports a mathematical model for predicting the fluid and heat flow characteristics of a Z-shaped corrugated perforated plate heat sink. Experiments were carried out to validate overall pressure drop as well as heat transfer predictions. A two-pronged approach was undertaken to design a corrugated perforated fin geometry: (a) macroscopic packaging, where the flow is distributed into conduits before being fed into perforated plates, and (b) microscopic design, where the pores are sized to maximize heat dissipation. A methodology typically used for predicting flow maldistribution is extended for packaging porous perforated plates in the macroscopic approach. An illustrative study is carried that estimates the optimum number of porous perforated plate fins that can be packaged within a given volume under fixed pressure drop constraint. In the microscopic approach, an order of magnitude analysis was carried out to decide the optimum diameter to maximize the heat transfer rate and expression for optimum diameter, and maximum achievable heat flux is proposed. Numerical simulations were carried out by considering full perforated plate porous fin geometry and single-channel geometry, and good agreement in their results was found. Finally, this study elaborates on the importance of achieving uniform flow distribution across the porous perforated plate fins.

Influence of Hole-To-Hole Interaction On the Acoustic Behavior of Multi-Orifice Perforated Plates

2021 ◽  
Author(s):  
Alireza Javareshkian ◽  
Alexis Dancelme ◽  
Hongyu Chen ◽  
Thomas Sattelmayer
Keyword(s):  
Resonance Frequency ◽  
Interaction Effect ◽  
Gas Turbines ◽  
Acoustic Radiation ◽  
Three Dimensional ◽  
Perforated Plate ◽  
Optimized Design ◽  
Perforated Plates ◽  
Aero Engines ◽  
Hole Interaction

Abstract The acoustic liner's optimized design is critical for developing low-emission combustion systems in modern gas turbines and aero-engines. Several models are available in the literature for the acoustic impedance of perforated acoustic liners. Most of these models neglect the interaction effect between orifices. Generally, orifices are closely distributed such that the interactions between acoustic radiation from neighboring orifices can affect their acoustical behavior. The hole-to-hole interaction effect may change the resonator's resonance frequency due to the nonplanar wave creation in the vicinity of area jumps. Considering this effect may help to predict the resonator's resonance frequency accurately. In this work, a three-dimensional (3D) analytical approach is developed to consider the nonplanar wave creation in the cavity and orifices on the perforated plate. The proposed 3D analytical method is employed to determine the hole-to-hole interaction end-correction of multi-orifice perforated plates. The hole-to-hole interaction end-correction from a series of perforated plates with different orifice radii and spacings is obtained via the Finite Element Method (FEM). Perforated plates with different center-to-center hole spacing are tested using an impedance tube. Experimental results show a shift in the resonance frequency towards a lower frequency with decreasing holes' spacing. The comparison with the experiments shows that the available end-correction models in the literature cannot capture the hole-to-hole interaction effect observed in experiments. In contrast, the proposed model can reproduce measurements with high quality.

scholarly journals Features of subsonic air flow around perforated plates

2020 ◽  
Author(s):  
A.G. Golubev ◽  
E.G. Stolyarova ◽  
M.D. Kalugina
Keyword(s):  
Normal Force ◽  
Air Flow ◽  
Angle Of Attack ◽  
Vertical Plane ◽  
Perforated Plate ◽  
Aerodynamic Characteristics ◽  
Perforated Plates ◽  
Subsonic Speed ◽  
Solid Plate ◽  
Zero Degree

The paper considers the process of flow around a flat plate with rounded front and side edges at various degrees of surface perforation. The flow patterns were studied both near the plate with zero degree of perforation, and at the surface of plates with a perforation degree of more than 20%. The features of air flow directly inside the holes at various values of the angle of attack are considered. Isobars of pressure distribution in the vertical plane of the flow over a solid plate are given. A simulation of the flow around a perforated plate at subsonic speed of the incoming air flow is performed, aerodynamic characteristics are obtained and graphical dependencies of the aerodynamic coefficients of longitudinal and normal force on the angle of attack are presented. Special attention is paid to the comparative analysis of aerodynamic characteristics for solid (with zero degree of perforation) and perforated plates.

Influence of Hole-to-Hole Interaction on the Acoustic Behavior of Multi-Orifice Perforated Plates

2021 ◽  
Author(s):  
Alireza Javareshkian ◽  
Alexis Dancelme ◽  
Hongyu Chen ◽  
Thomas Sattelmayer
Keyword(s):  
Wave Propagation ◽  
Resonance Frequency ◽  
Interaction Effect ◽  
Gas Turbines ◽  
Perforated Plate ◽  
Wall Region ◽  
Optimized Design ◽  
Perforated Plates ◽  
Proposed Model ◽  
Hole Interaction

Abstract A key factor for developing low-emission combustion systems in modern gas turbines and aero-engines is the acoustic liner’s optimized design. Several models are available in the literature for the acoustic impedance of perforated acoustic liners. Most of these impedance models neglect the interaction effect between the orifices. In practice, the orifices are generally closely distributed such that the interactions between acoustic radiation from neighboring orifices can affect their acoustical behavior. The hole-to-hole interaction effect may change the resonance frequency of the resonator due to the nonplanar wave propagation in the cavity, the orifices in the perforated plate, and the near-wall region in the combustor. Considering this effect may help to predict the resonance frequency of the resonator accurately. In this work, a three-dimensional (3D) analytical approach is developed to account for the nonplanar wave propagation in the cavity and orifices on the perforated plate. The present study employs the proposed 3D analytical method to determine the hole-to-hole interaction end-correction of multi-orifice perforated plates. Additionally, the hole-to-hole interaction end-correction from a series of perforated plates with different orifice radii and spacings is obtained via the Finite Element Method (FEM). Perforated plate specimens with different center-to-center hole spacing are tested using an impedance tube. Experimental results show that the resonance frequency is shifted towards a lower frequency with decreasing holes’ spacing. The resulting model is compared with the experiments and the end-correction models available in the literature. The comparison shows that the available end-correction models cannot capture the hole-to-hole interaction effect, which is observed in experiments. In contrast, the proposed model can reproduce measurements with high quality. The resulting model demonstrates that the acoustic end-correction length for orifices is closely related to the perforated plate’s porosity ratio and orifice radius. The proposed model is readily applicable in the design of multi-orifice perforated plates.

COMPUTATIONAL AND EXPERIMENTAL INVESTIGATIONS OF FLOW CHARACTERISTICS IN A CURVILINEAR INLET CHANNEL

2017 ◽  
Vol 48 (4) ◽  
pp. 357-362
Author(s):  
Denis Vyacheslavovich Anokhin ◽  
Evgenia Sergeevna Dyagileva ◽  
Oleg Petrovich Minin ◽  
Dmitrii Aleksandrovich Olishevskii ◽  
Sergei Grigorievich Shevel'kov
Keyword(s):  
Flow Characteristics ◽  
Experimental Investigations ◽  
Inlet Channel

Scoundrels or Stars? Theory and Evidence on the Quality of Workers in Online Labor Markets

2016 ◽  
Vol 92 (1) ◽  
pp. 93-114 ◽  
Author(s):  
Anne M. Farrell ◽  
Jonathan H. Grenier ◽  
Justin Leiby
Keyword(s):  
Labor Markets ◽  
Data Availability ◽  
Accounting Research ◽  
Research Participants ◽  
Large Numbers ◽  
Research Designs ◽  
Online Labor Markets ◽  
Online Labor ◽  
Low Pay

ABSTRACT Online labor markets allow rapid recruitment of large numbers of workers for very low pay. Although online workers are often used as research participants, there is little evidence that they are motivated to make costly choices to forgo wealth or leisure that are often central to addressing accounting research questions. Thus, we investigate the validity of using online workers as a proxy for non-experts when accounting research designs use more demanding tasks than these workers typically complete. Three experiments examine the costly choices of online workers relative to student research participants. We find that online workers are at least as willing as students to make costly choices, even at significantly lower wages. We also find that online workers are sensitive to performance-based wages, which are just as effective in inducing high effort as high fixed wages. We discuss implications of our results for conducting accounting research with online workers. Data Availability: Contact the authors.

Animal Models and Alternatives in the Quality Control of Vaccines: Are In Vitro Methods or In Vivo Methods the Scientific Equivalent of the Emperor's New Clothes?

1995 ◽  
Vol 23 (1) ◽  
pp. 61-73
Author(s):  
Coenraad Hendriksen ◽  
Johan van der Gun
Keyword(s):  
Quality Control ◽  
Test Methods ◽  
In Vitro Test ◽  
Large Numbers ◽  
Alternative Approach ◽  
Inactivated Vaccines ◽  
Vitro Test

In the quality control of vaccine batches, the potency testing of inactivated vaccines is one of the areas requiring very large numbers of animals, which usually suffer significant distress as a result of the experimental procedures employed. This article deals with the potency testing of diphtheria and tetanus toxoids, two vaccines which are used extensively throughout the world. The relevance of the potency test prescribed by the European Pharmacopoeia monographs is questioned. The validity of the potency test as a model for the human response, the ability of the test to be standardised, and the relevance of the test in relation to the quality of the product are discussed. It is concluded that the potency test has only limited predictive value for the antitoxin responses to be expected in recipients of these toxoids. An alternative approach for estimating the potency of toxoid batches is discussed, in which a distinction is made between estimation of the immunogenic potency of the first few batches obtained from a seed lot and monitoring the consistency of the quality of subsequent batches. The use of animals is limited to the first few batches. Monitoring the consistency of the quality of subsequent batches is based on in vitro test methods. Factors which hamper the introduction and acceptance of the alternative approach are considered. Finally, proposals are made for replacement, reduction and/or refinement (the Three Rs) in the use of animals in the routine potency testing of toxoids.

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