A Parametric Study of Surge and Flow Instabilities in Gas Pipeline Compression Systems: The Effect of Pipe Parameters on Surge Margins

2002 ◽  
Author(s):  
K. Albayrak ◽  
D. Burtaskiray ◽  
O. C. Eralp ◽  
K. M. Akyuzly
Keyword(s):  
Parametric Study ◽  
Gas Flow ◽  
Coupling Effect ◽  
Flow Characteristics ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Pipe Length ◽  
Compression System ◽  
One Dimensional ◽  
Numerical Experimentation

There is a need to understand the effect of coupling of the flow characteristics of a compressor with that of the pipeline and how this coupling effect the stability of the flow in a compression system. This study addresses such a need by carrying out a numerical simulation of the flow in the whole compression system including the compressor, the pipeline, and the other associated flow elements. A nonlinear, one-dimensional mathematical model is adopted for the present study. In this model, the gas flow inside the pipeline is assumed one-dimensional, viscous, and compressible. A parametric study is carried out using the proposed model, with air as the working fluid, to predict the surge margins for a subscale compression system and to study the effect of pipe length and diameter on these margins. Furthermore, the effect of these geometrical parameters on the amplitude and frequency of the flow oscillations are also established by numerical experimentation.

Predictable Model for Characteristics of One-Dimensional Solid-Gas-Liquid Three-Phase Mixtures Flow Along a Vertical Pipeline With an Abrupt Enlargement in Diameter

1999 ◽  
Vol 121 (2) ◽  
pp. 330-342 ◽  
Author(s):  
Natsuo Hatta ◽  
Masaaki Omodaka ◽  
Fumitaka Nakajima ◽  
Takahiro Takatsu ◽  
Hitoshi Fujimoto ◽  
...  
Keyword(s):  
Gas Flow ◽  
Sudden Change ◽  
Flow Characteristics ◽  
Point Of View ◽  
Solid Particles ◽  
Governing Equations ◽  
One Dimensional ◽  
Three Phase ◽  
Experimental Values ◽  
The One

This paper treats the numerical analysis of the rising process of a solid-gas-liquid three-phase mixture along a vertical pipeline with an abrupt enlargement in diameter. The system of governing equations used is based upon the one-dimensional multifluid model and the transitions of gas flow pattern are taken into account in the system of governing equations. For the case of a sudden enlargement in diameter in a coaxial pipeline, the procedure of the numerical calculation to obtain the flow characteristics in the pipeline section after a sudden change in diameter has been established here. Furthermore, in order to confirm the validity of the present theoretical model by the comparison between the calculated and experimental values, the experiments have been made using four kinds of lifting pipes, including the straight one. Thereby, it has been found that the numerical model proposed here gives good fit to the prediction of the flow rates of lifted water and solid particles against that of air supplied for the case of a sudden change in diameter. In addition, the flowing process for each phase has been investigated from a photographic point of view. As a result, we found that the moving process of the solid particles depends strongly upon the volumetric flux of gas-phase as well as the submergence ratio.

Parametric Analysis of a PULSCO Vent Silencer

2014 ◽  
Author(s):  
Usama Tohid ◽  
Chris Genger ◽  
John Kaiser ◽  
Ilaria Accorsi ◽  
Arturo Pacheco-Vega
Keyword(s):  
Mathematical Model ◽  
Parametric Study ◽  
Numerical Results ◽  
Operating Conditions ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Computational Domain ◽  
Hole Size ◽  
Plane Wave Solution ◽  
The Mathematical Model

We have conducted a parametric study via numerical simulations of a PULSCO vent silencer. The overall objective is to demonstrate the existence of an optimum system performance for a given set of operating conditions i.e., temperature, pressure, mass flow-rate and the working fluid, by modifying the corresponding geometry of the device. The vent silencer under consideration consists of a perforated diffuser, the silencer body and a tube module. The tube module consists of a set of tubes through which the working fluid passes. The flow tubes are perforated and surrounded with acoustic packing that is responsible for the attenuation. The mathematical model of the vent silencer is built upon Helmholtz equation for the plane wave solution, and the Delany-Bazley model for the acoustic packing. The geometrical parameters chosen for the parametric study include: the porosity of the diffuser and the flow tubes, the type of packing material used for the tube module, bulk density for the acoustic packing and the hole diameter of the perforated diffuser and flow tubes. The equations of the mathematical model are discretized over the computational domain and solved with a finite element method. Numerical results in terms of transmission loss, for the system, indicate that diffuser hole size of 1/4” with porosity of 0.1, flow tube hole size of 1/8” with porosity of 0.23, packing density of 16 kg/m3 for TRS-10 and 100 kg/m3 for Advantex provided the optimum results for the chosen set of conditions. The numerical results were found to be in agreement with experimental data.

scholarly journals Disc Thickness and Spacing Distance Impacts on Flow Characteristics of Multichannel Tesla Turbines

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 44 ◽  
Author(s):  
Wenjiao Qi ◽  
Qinghua Deng ◽  
Yu Jiang ◽  
Qi Yuan ◽  
Zhenping Feng
Keyword(s):  
High Efficiency ◽  
Flow Characteristics ◽  
Aerodynamic Performance ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Spacing Distance ◽  
One To One ◽  
The One ◽  
High Level ◽  
Isentropic Efficiency

Tesla turbines are a kind of unconventional bladeless turbines, which utilize the viscosity of working fluid to rotate the rotor and realize energy conversion. They offer an attractive substitution for small and micro conventional bladed turbines due to two major advantages. In this study, the effects of two influential geometrical parameters, disc thickness and disc spacing distance, on the aerodynamic performance and flow characteristics for two kinds of multichannel Tesla turbines (one-to-one turbine and one-to-many turbine) were investigated and analyzed numerically. The results show that, with increasing disc thickness, the isentropic efficiency of the one-to-one turbine decreases a little and that of the one-to-many turbine reduces significantly. For example, for turbine cases with 0.5 mm disc spacing distance, the former drops less than 7% and the latter decreases by about 45% of their original values as disc thickness increases from 1 mm to 2 mm. With increasing disc spacing distance, the isentropic efficiency of both kinds of turbines increases first and then decreases, and an optimal value and a high efficiency range exist to make the isentropic efficiency reach its maximum and maintain at a high level, respectively. The optimal disc spacing distance for the one-to-one turbine is less than that for the one-to-many turbine (0.5 mm and 1 mm, respectively, for turbine cases with disc thickness of 1 mm). To sum up, for designing a multichannel Tesla turbine, the disc spacing distance should be among its high efficiency range, and the determination of disc thickness should be balanced between its impacts on the aerodynamic performance and mechanical stress.

scholarly journals One-Dimensional Numerical Analysis of Cross-Sectional Area Variation Effects on Flow through the Gas Turbine Diffuser

2019 ◽  
Author(s):  
Nima Zamani Meymian ◽  
Reza Khodadadi
Keyword(s):  
Mach Number ◽  
Boundary Conditions ◽  
Gas Turbine ◽  
Cross Section ◽  
Gas Flow ◽  
Flow Characteristics ◽  
Time Step ◽  
Cross Sectional ◽  
One Dimensional ◽  
Length Changes

In the paper, a one-dimensional compressible flow of gas inside the gas turbine’s diffuser has been simulated. The modeling has been performed to the aim of obtaining boundary conditions of outlet gas from diffuser and inlet gas to the combustion chamber. Depending on working flow regimes of fluid including subsonic, transonic, and supersonic flows, changes of diffuser cross-section have different effects on gas flow characteristics. For these effects to be correctly imposed, Mach number of the gas flow in each time-step affected by changes of cross-section would be determined, depending on the local Mach number in the same time-step. Obtaining distribution of Mach number along diffuser length, changes in other main characteristics of flow such as pressure, temperature, speed, and density for all of the points along diffuser length would be obtained. In order to verify the validity of the numerical algorithm used, the gas flow would be solved in a divergent nozzle and compared to other numerical methods. In the end, using gas turbine diffuser’s geometrical information, compressible gas flow inside it would be studied using the actual boundary conditions for a 25 MW gas turbine.

Effects of Varying Geometrical Parameters on Boiling From Microfabricated Enhanced Structures

2003 ◽  
Vol 125 (1) ◽  
pp. 103-109 ◽  
Author(s):  
C. Ramaswamy ◽  
Y. Joshi ◽  
W. Nakayama ◽  
W. B. Johnson
Keyword(s):  
Heat Dissipation ◽  
Layer Structure ◽  
Single Layer ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Small Range ◽  
Two Phase ◽  
Wall Superheat

The current study involves two-phase cooling from enhanced structures whose dimensions have been changed systematically using microfabrication techniques. The aim is to optimize the dimensions to maximize the heat transfer. The enhanced structure used in this study consists of a stacked network of interconnecting channels making it highly porous. The effect of varying the pore size, pitch and height on the boiling performance was studied, with fluorocarbon FC-72 as the working fluid. While most of the previous studies on the mechanism of enhanced nucleate boiling have focused on a small range of wall superheats (0–4 K), the present study covers a wider range (as high as 30 K). A larger pore and smaller pitch resulted in higher heat dissipation at all heat fluxes. The effect of stacking multiple layers showed a proportional increase in heat dissipation (with additional layers) in a certain range of wall superheat values only. In the wall superheat range 8–13 K, no appreciable difference was observed between a single layer structure and a three layer structure. A fin effect combined with change in the boiling phenomenon within the sub-surface layers is proposed to explain this effect.

Gas flow characteristics in shale fractures after supercritical CO2 soaking

2021 ◽  
Vol 88 ◽  
pp. 103826
Author(s):  
Yiyu Lu ◽  
Jiankun Zhou ◽  
Honglian Li ◽  
Jiren Tang ◽  
Lei Zhou ◽  
...  
Keyword(s):  
Supercritical Co2 ◽  
Gas Flow ◽  
Flow Characteristics

Axial guided wave characteristics in functionally graded one-dimensional hexagonal piezoelectric quasi-crystal cylinders

2021 ◽  
pp. 108128652110134
Author(s):  
B. Zhang ◽  
X.H. Wang ◽  
L. Elmaimouni ◽  
J.G. Yu ◽  
X.M. Zhang
Keyword(s):  
Coupling Effect ◽  
Energy Conversion Efficiency ◽  
Guided Wave ◽  
Functionally Graded ◽  
Phonon Modes ◽  
One Dimensional ◽  
Longitudinal Modes ◽  
Wave Characteristics ◽  
Piezoelectric Effects ◽  
Hollow Cylinders

In one-dimensional hexagonal piezoelectric quasi-crystals, there exist the phonon–phason, electro–phonon, and electro–phason couplings. Therefore, the phonon–phason coupling and piezoelectric effects on axial guided wave characteristics in one-dimensional hexagonal functionally graded piezoelectric quasi-crystal (FGPQC) cylinders are investigated by utilizing the Legendre polynomial series method. The dispersion curves and cut-off frequencies are illustrated. Wave characteristics in three hollow cylinders with different quasi-periodic directions are comparatively studied. Some new wave phenomena are revealed: the phonon–phason coupling and piezoelectric effects on the longitudinal and torsional phonon modes ( N = 0) vary as the quasi-periodic direction changes; the phonon–phason coupling effect on flexural–torsional modes in the r-, z-FGPQC hollow cylinders, and on flexural–longitudinal modes in ϑ-FGPQC hollow cylinders increases as N increases. The corresponding results obtained in this work lay the theoretical foundation for the design and manufacture of piezoelectric transducers with high resolution and energy-conversion efficiency.

scholarly journals Special Finite Elements with Adaptive Strain Field on the Example of One-Dimensional Elements

2021 ◽  
Vol 11 (2) ◽  
pp. 609
Author(s):  
Tadeusz Chyży ◽  
Monika Mackiewicz
Keyword(s):  
Finite Elements ◽  
Strain Field ◽  
Main Idea ◽  
Deformation Field ◽  
Geometrical Parameters ◽  
Single Element ◽  
One Dimensional ◽  
New Type ◽  
Self Adaptation ◽  
Adaptation Method

The conception of special finite elements called multi-area elements for the analysis of structures with different stiffness areas has been presented in the paper. A new type of finite element has been determined in order to perform analyses and calculations of heterogeneous, multi-coherent, and layered structures using fewer finite elements and it provides proper accuracy of the results. The main advantage of the presented special multi-area elements is the possibility that areas of the structure with different stiffness and geometrical parameters can be described by single element integrated in subdivisions (sub-areas). The formulation of such elements has been presented with the example of one-dimensional elements. The main idea of developed elements is the assumption that the deformation field inside the element is dependent on its geometry and stiffness distribution. The deformation field can be changed and adjusted during the calculation process that is why such elements can be treated as self-adaptive. The application of the self-adaptation method on strain field should simplify the analysis of complex non-linear problems and increase their accuracy. In order to confirm the correctness of the established assumptions, comparative analyses have been carried out and potential areas of application have been indicated.

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