Design and Testing of Multistage Centrifugal Compressors With Small Diffusion Ratios

2008 ◽  
Author(s):  
C. Aalburg ◽  
A. Simpson ◽  
M. B. Schmitz ◽  
V. Michelassi ◽  
S. Evangelisti ◽  
...  
Keyword(s):  
Outer Radius ◽  
Maximum Efficiency ◽  
Main Stage ◽  
Outer Diameter ◽  
Large Radius ◽  
Original Design ◽  
Small Diffusion ◽  
Experimental Database ◽  
Baseline Design ◽  
Design And Optimization

Two stators of a multistage centrifugal compressor with progressively smaller outer radii have been designed, built and tested. The aim was to achieve a significant reduction in outer diameter of the compressor stage without compromising performance. The reduction of size was achieved by reducing the diffusion ratio (outer radius/inner radius) of the vaneless diffuser in two steps. In the first step the outer diameter of the entire stage was reduced by 8% compared to the baseline design. In the second stage the outer diameter was reduced by 14%. The outer radius of the smallest design was limited by the impeller exit diameter, which was kept constant, as was the axial length of the stage. The large radius baseline design has been tested on a rotating rig in a 1.5 stage setup. This setup aimed at simulating multistage behavior by applying a pseudo stage upstream of the main stage. The pseudo stage consisted of a set of non-rotating preswirl vanes, in order to mimic an upstream impeller, and was followed by a scaled version of the return channel of the main stage. The experimental database was then used to calibrate a 1D analysis code and 3D-CFD methods for the ensuing design and optimization part. By applying extensive Design-Of-Experiments (DOE), the endwalls as well as the vanes of the stator part were optimized for maximum efficiency and operation range. In order to preserve multistage performance, the optimization was constrained by keeping the circumferentially averaged spanwise flow profiles at the exit of the smaller radius stages within close limits to the original design. The reduced radius designs were then tested in the same 1.5 stage setup as the baseline design. The results indicate that the reduction in size was feasible without compromising efficiency and operation range of the stage.

Design and Testing of Multistage Centrifugal Compressors With Small Diffusion Ratios

2011 ◽  
Vol 134 (4) ◽  
Author(s):  
C. Aalburg ◽  
A. Simpson ◽  
M. B. Schmitz ◽  
V. Michelassi ◽  
S. Evangelisti ◽  
...  
Keyword(s):  
Outer Radius ◽  
Maximum Efficiency ◽  
Main Stage ◽  
Outer Diameter ◽  
Large Radius ◽  
Original Design ◽  
Small Diffusion ◽  
Experimental Database ◽  
Baseline Design ◽  
Design And Optimization

Two stators of a multistage centrifugal compressor with progressively smaller outer radii have been designed, built, and tested. The aim was to achieve a significant reduction in the outer diameter of the compressor stage without compromising performance. The reduction in size was achieved by reducing the diffusion ratio (outer radius/inner radius) of the vaneless diffuser in two steps. In the first step, the outer diameter of the entire stage was reduced by 8% compared with the baseline design. In the second stage, the outer diameter was reduced by 14%. The outer radius of the smallest design was limited by the impeller exit diameter, which was kept constant, as was the axial length of the stage. The large radius baseline design has been tested on a rotating rig in a 1.5 stage setup. This setup aimed at simulating the multistage behavior by applying a pseudostage upstream of the main stage. The pseudostage consisted of a set of nonrotating preswirl vanes in order to mimic an upstream impeller and was followed by a scaled version of the return channel of the main stage. The experimental database was then used to calibrate a 1D analysis code and 3D–computational fluid dynamics methods for the ensuing design and optimization part. By applying an extensive design-of-experiments, the endwalls as well as the vanes of the stator part were optimized for maximum efficiency and operation range. In order to preserve the multistage performance, the optimization was constrained by keeping the circumferentially averaged spanwise flow profiles at the exit of the smaller radius stages within close limits to the original design. The reduced radius designs were then tested in the same 1.5 stage setup as the baseline design. The results indicate that the reduction in size was feasible without compromising the efficiency and operation range of the stage.

Design and Optimization of a Ducted Marine Current Savonius Turbine for Gun-Barrel Passage, Fiji

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Jai Nendran Goundar ◽  
M. Rafiuddin Ahmed ◽  
Young-Ho Lee
Keyword(s):  
Flow Characteristics ◽  
Maximum Efficiency ◽  
Speed Ratio ◽  
Water Stream ◽  
Freestream Velocity ◽  
Design And Optimization ◽  
Gun Barrel ◽  
Marine Current ◽  
Ducted Turbine ◽  
Shaft Power

Marine current energy is a reliable and clean source of energy. Many marine current turbines have been designed and developed over the years. Placement of an appropriately designed duct or shroud around the turbine significantly improves the turbine performance. In the present work, a ducted Savonius turbine (DST) is designed and optimized and its performance analysis carried out. The components of DSTs are simple and easily available and can be manufactured in developing countries like Fiji. A scaled-down model of 1/20 of a DST was fabricated and tested in a water stream at a velocity of 0.6 m/s and the results were used to validate the results from a commercial computational fluid dynamics (CFD) code ANSYS-cfx. Finally, a full-scale DST was modeled to study the flow characteristics in the turbine and the performance characteristics. The maximum efficiency of the turbine is around 50% at the tip speed ratio (TSR) of 3.5 and the maximum shaft power obtained is 10 kW at the rated speed of 1.15 m/s and around 65 kW at a freestream velocity of 2.15 m/s. The stress distribution on the ducted turbine was also obtained.

scholarly journals Multifield Coupling Model and Performance Analysis of a Hydrostatic Mechanical Seal

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5159
Author(s):  
Guiyue Kou ◽  
Xinghu Li ◽  
Yan Wang ◽  
Chunsen Tan ◽  
Kanran Zhou ◽  
...  
Keyword(s):  
Fluid Pressure ◽  
Coupling Model ◽  
Outer Diameter ◽  
Mechanical Seal ◽  
Design And Optimization ◽  
Seal Design ◽  
Mechanical Deformations ◽  
Deformation State ◽  
Inner Diameter ◽  
And Performance

A two-dimensional axisymmetric thermal-fluid-solid coupled mathematical model of a contact mechanical seal is established. The finite difference method is used to solve the control equations for the fluid pressure and temperature of the seal end face, and the finite element method is used to determine the thermal deformation state of the seal. The seal’s performance at different working speeds was studied and verified by experiments. The results show that under the combined actions of thermal and mechanical deformations, the seal end face forms a convergent leakage gap from the outer diameter to the inner diameter. The minimum film thickness is observed on the inner diameter side of the seal end face, and the highest end face temperature coincides with this location. With increasing working speed, the contact force at the inner diameter side increases, the temperature difference between the inner diameter and the outer diameter of the end face increases, and the leakage rate correspondingly increases. The numerical simulation results are in good agreement with the experimental results. The model and calculation method can be applied to other forms of mechanical seal design and optimization.

Investigation on NOx of a Low Emission Combustor Design With Multihole Premixer-Prevaporizer

2004 ◽  
Author(s):  
Yuzhen Lin ◽  
Yunhui Peng ◽  
Gaoen Liu
Keyword(s):  
Great Influence ◽  
Nox Emission ◽  
Emissions Reduction ◽  
Inlet Temperature ◽  
Main Stage ◽  
Nox Emissions ◽  
Baseline Design ◽  
Air Mixing ◽  
Reduction Of Nox ◽  
Two Stages

A low NOx emission combustor design was presented in this paper. The design features the premixer-prevaporizer tube with multihole and two stages arranged radially in line, with the outer stage being pilot stage and inner stage being main stage. The multihole premixer and prevaporizer is a part of main stage. The results of NOx emission were provided and also compared with the baseline design that the premixer and prevaporizer tube without multihole. The double swirler prefilming airblast atomizer was installed in the premixed prevaporized duct entrance. The mean drop size and radial fuel flux distribution were measured to determine proper configurations of the multihole premixer-prevaporizer. NOx emission investigations were carried out using a test combustor with one pilot stage and one main stage under the operating condition of high inlet temperature (800K) and inlet air pressure was atmospheric pressure. The experiment results demonstrated large NOx emissions reduction of the multihole premixer-prevaporizer compared with the baseline design. The more even fuel-air mixing, which was gained by the multiple jets, intensified the fuel and air mixing within the premixer-prevaporizer, resulted in the large reduction of NOx emission. The configurations of multihole premixer-prevaporizer had great influence on NOx emissions reduction.

scholarly journals Exact Optimum Design of Segmented Thermoelectric Generators

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
M. Zare ◽  
H. Ramin ◽  
S. Naemi ◽  
R. Hosseini
Keyword(s):  
Maximum Efficiency ◽  
Thermoelectric Generators ◽  
Approximate Methods ◽  
Design And Optimization ◽  
Compatibility Factor ◽  
Maximum Conversion Efficiency ◽  
Design Characteristics ◽  
Exact And Approximate Methods ◽  
And Performance ◽  
Theoretical Results

A considerable difference between experimental and theoretical results has been observed in the studies of segmented thermoelectric generators (STEGs). Because of simplicity, the approximate methods are widely used for design and optimization of the STEGs. This study is focused on employment of exact method for design and optimization of STEGs and comparison of exact and approximate results. Thus, using new highly efficient thermoelectric materials, four STEGs are proposed to operate in the temperature range of 300 to 1300 kelvins. The proposed STEGs are optimally designed to achieve maximum efficiency. Design and performance characteristics of the optimized generators including maximum conversion efficiency and length of elements are calculated through both exact and approximate methods. The comparison indicates that the approximate method can cause a difference up to 20% in calculation of some design characteristics despite its appropriate results in efficiency calculation. The results also show that the maximum theoretical efficiency of 23.08% is achievable using the new proposed STEGs. Compatibility factor of the selected materials for the proposed STEGs is also calculated using both exact and approximate methods. The comparison indicates a negligible difference in calculation of compatibility factor, despite the considerable difference in calculation of reduced efficiency (temperature independence efficiency).

Optimization of a Large Injection System for Steam Turbines

2015 ◽  
Author(s):  
Leonardo Nettis ◽  
Enzo Imparato ◽  
Lorenzo Cosi
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Flow Distribution ◽  
Low Pressure ◽  
Total Pressure Loss ◽  
Injection System ◽  
Steam Turbines ◽  
Original Design ◽  
Design And Optimization ◽  
Large Injection

Steam turbines are applied in production plants characterized by very large injections of low pressure steam. For this reason the design and optimization of the injection section is fundamental to obtain an adequate level of turbine efficiency and ensure uniform flow at the inlet of the low pressure stages downstream the injection. This paper illustrate the optimization performed on a Steam Turbine injection system for a unit in which injection flow is 80% of the total outlet mass flow. Optimization was performed varying the shape of the original steam guide with the twofold objective of minimizing the total pressure loss and uniform the circumferential flow distribution. The analysis has been performed using RANS 2D and 3D CFD solver. The design process has been structured in 3 different steps: i) Axisymmetric CFD screening based on DOE ii) 3D-CFD verification of the profile shape previously obtained with the additional estimation of the flow uniformity on 360° iii) 3D-CFD of the injection module including the reaction stage upstream and the first LP stage downstream, with the stator modeled on 360°. The main outcomes are presented in terms of total pressure loss and uniformity of circumferential flow, both strongly reduced with respect to the original design. Moreover in order to characterize the excitation associated with flow non-uniformity an analysis in the frequency domain of the flow distribution has been performed.

Design and Optimization of Mechanically Resonant Torsional Spring Mechanism for Laser Light Dispersion Applications

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
Loke Kean Koay ◽  
Horizon Gitano-Briggs
Keyword(s):  
Laser Light ◽  
Geometric Optimization ◽  
Geometrical Parameters ◽  
Analysis Model ◽  
Original Design ◽  
Element Analysis ◽  
Design And Optimization ◽  
Torsional Spring ◽  
The Finite Element Analysis ◽  
Spring Mechanism

A laser light scanning device consisting of an electronically driven mechanically resonant torsional spring-mirror system was developed for display applications. The original design suffers fatigue failure due to the repeated rotation of the torsional spring. The torsional spring design is investigated and analyzed to attain the lowest possible stress level while maintaining a constant resonant frequency. The finite element analysis model of the torsional spring was created and the stress was minimized by changing the geometrical parameters of the spring. Spring geometric optimization resulted in a maximum stress of 0.632 GPa, that is 12% reduction in stress from the original design, which should give an extended life span of 1 month for the intended application.

Tolerance-Based Layer Setup Optimization for Layered Manufacturing

2010 ◽  
Author(s):  
Jack Szu-Shen Chen ◽  
Hsi-Yung Steve Feng
Keyword(s):  
Layer Thickness ◽  
Maximum Error ◽  
Layered Manufacturing ◽  
Design Model ◽  
Maximum Efficiency ◽  
Original Design ◽  
Allowable Deviation ◽  
Number Of Layers ◽  
Build Time ◽  
Model Geometry

This paper introduces a new tolerance-based method to generate the optimum layer setup required to build layered manufacturing (LM) end-user parts for maximized efficiency. To achieve this, the deviation between the final polished LM part geometry and the original design model are formulated and controlled. Maximized layer thicknesses are then realized through optimization of each layer position with respect to the design and final geometry and maximization of the allowable deviation for each layer, which consequently leads to minimization of the build time. Current LM layer setup methods do not take into account of the final part during layer setup generation, rendering layer thickness selection to operator-deemed-best. Without the ability to predict the final geometry and to optimize the layer setup accordingly, layer thickness selection is often overly conservative, causing more layers than necessary to be used. Since the LM build time increases exponentially with an increase in the number of layers, efficiency is greatly reduced with conservative layer setup. To achieve maximum efficiency, this paper proposes a new method based on error compensation and minimization to solve for the optimum layer setup necessary to allow the resulting final physical part to reliably approximate the design model geometry according to a user specified tolerance limit. Case studies have been performed in order to validate that the proposed method is able to minimize the number of layers for constructing an LM part while controlling the maximum error for tolerance conformance.

scholarly journals Lightweight Threshing Rack under Multisource Excitation Based on Modal Optimization Method

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Haotian Zhang ◽  
Zhong Tang ◽  
Yu Li ◽  
Xin Liu ◽  
Hui Ren
Keyword(s):  
Structural Design ◽  
Excitation Frequency ◽  
Optimization Method ◽  
Mode Shapes ◽  
Stress And Strain ◽  
Original Design ◽  
Design And Optimization ◽  
Finite Element Software ◽  
Combine Harvester ◽  
Stress And Strain Distribution

Crawler rice combine harvester threshing rack excited by different frequencies of multiple working parts would cause strong vibration response. In this paper, the rack-type rice combine harvester threshing rack was taken as research objective, and then the static analysis of the existing threshing rack was carried out by ANSYS Finite Element software. The topology of the rack structure was optimized according to the stress and strain distribution of the threshing rack. Based on solving the 6 natural frequencies and mode shapes of the threshing rack of combine harvester, the morphological test of threshing rack was carried out and the reliability of the modal analysis was verified. Finally, the multivibration source was assembled on the rack for simulation to test and verify the optimization effectiveness. Results showed that the 1st to 6th natural frequency of threshing rack after modal optimization could avoid the excitation frequency of the working part. Compared with the original design, the optimized threshing rack had a weight reduction of 13.7%. This study can provide a theoretical reference for the structural design and optimization of combine harvester threshing rack.

On the Predicted Performance of Oil Lubricated Thrust Collars in Integrally Geared Compressors

2014 ◽  
Author(s):  
Luis San Andrés ◽  
Travis A. Cable ◽  
Karl Wygant ◽  
Andron Morton
Keyword(s):  
High Speed ◽  
Hydrodynamic Lubrication ◽  
Axial Stiffness ◽  
Outer Diameter ◽  
Damping Force ◽  
Design And Optimization ◽  
Process Gas ◽  
Simple Geometry ◽  
Mechanical Elements ◽  
Stiffness And Damping

Integrally geared compressors (IGCs) comprise of single stage impellers installed on the ends of pinion shafts, all driven by a main bull gear (BG) and shaft system. When compared to single shaft multistage centrifugal compressors, the benefits of IGCs include better thermal efficiency, reduced footprint and simple foundation, dispensing with a high speed coupling, as well as better access for maintenance and overhauls. In IGCs the compression of the process gas induces axial loads on the pinion shafts that are transmitted via thrust collars (TCs) to the main drive shaft and balanced by a single thrust bearing. The TCs, located on either side of pinion gears, slightly overlap with the BG outer diameter to form lentil-shaped lubricant-wetted regions. Archival literature on the design and optimization of TCs is scant, in spite of their widespread usage as they are comprised of simple geometry mechanical elements. This paper presents an analysis of the hydrodynamic film pressure generated in a lubricated TC due to the rotation of both thrust collar and bull gears and specified taper angles for both bodies. The model solves the Reynolds equation of hydrodynamic lubrication to predict the operating film thickness that generates a pressure field reacting to impellers’ thrust loads; these forces being a function of the pinion speed and the process gas physical properties. The model also predicts performance parameters such as power loss and axial stiffness and damping force coefficients. A parametric study brings out the taper angles in the TC and BG that balance the transmitted load with a lesser friction factor and peak pressure, along with large axial stiffness and damping.

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