Optimization of Non-axisymmetric Endwall Contours for the Rotor of a Low Speed, 112-Stage Research Turbine With Unshrouded Blades—Optimization and Experimental Validation

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Jonathan Bergh ◽  
Glen Snedden ◽  
Dwain Dunn
Keyword(s):  
Experimental Results ◽  
Pressure Probe ◽  
Test Case ◽  
Current Case ◽  
Low Speed ◽  
Additional Information ◽  
Measurement Plane ◽  
Direct Laser ◽  
Improved Performance ◽  
Design And Practice

Abstract This paper presents the predicted, as well as final experimental results for the design of an automatically optimized non-axisymmetric endwall and as such, attempts to close the loop between design and practice, providing additional information to other groups involved in the design of endwall contours. The contours designed in this investigation were manufactured using the direct laser sintering rapid prototyping method and installed and tested in the low-speed, 112-stage turbine at the CSIR’s test turbine facility (TTF) in Pretoria, South Africa. Steady-state 5-hole pressure probe traverses were used to characterize the performance and flow profiles upstream, immediately downstream and in a quasi-“mixed-out” sense downstream of the rotor. In addition to the datum (annular) case, both the computed as well as experimental results were compared to the corresponding results generated for a “generically” contoured rotor which was originally designed for a linear cascade test case, but one which used the same blade profile to the current case. The results show that in general both sets of contours performed well, although the added emphasis on flow correction for the contours produced in this investigation resulted in slightly worse performance in terms of loss at the rotor exit (X3) but greatly improved performance in terms of the efficiency and flow angles at the “mixed-out” (X4) measurement plane.

A Turbine Cascade Facility for Secondary Flow Research

2006 ◽  
Author(s):  
D. A. Bagshaw ◽  
D. G. Gregory-Smith ◽  
G. L. Ingram ◽  
M. R. Stokes
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Experimental Results ◽  
Test Case ◽  
Turbine Cascade ◽  
Inlet Flow ◽  
Low Speed ◽  
To Come

This paper outlines some recent major changes to the so-called Durham Cascade that will be of interest to other experimenters working on low speed linear cascades. The Durham Cascade is a popular CFD test case and has also been used extensively for profiled endwall research (Hartland et al. [1]) and more recently for the study of reverse compound lean (Bagshaw et al. [2]). The cascade has recently undergone a complete rebuild, which enables it to provide experimental results of lasting significance for a number of years to come. The improvements described in this paper include, good quality symmetrical inlet flow, a new three-dimensional traverse system and an improved blade cartridge system allowing arbitrary three-dimensional geometries to be tested.

Micro CO2 Sensor Based on Li2CO3, Pt | Li3PO4 | Pt, Li2TiO3-TiO2 Structure

2010 ◽  
Vol 44-47 ◽  
pp. 2747-2751
Author(s):  
Hai Rong Wang ◽  
Jun Qiang Ren ◽  
Guo Liang Sun ◽  
Di Cen
Keyword(s):  
Solid Electrolyte ◽  
Gas Sensor ◽  
Experimental Results ◽  
Al2o3 Substrate ◽  
Reference Electrodes ◽  
Co2 Gas ◽  
Speed Of Response ◽  
Co2 Gas Sensor ◽  
Improved Performance ◽  
Mems Process

This paper presents a micro solid electrolyte CO2 gas sensor in which Li2CO3, Li2TiO3-TiO2 serves as sensing and reference electrodes respectively, and the Li3PO4 film acts as the electrolyte. The sensor was constructed in the sequent layers of O2, CO2, Li2CO3, Pt | Li3PO4 | Pt, Li2TiO3-TiO2, O2, CO2 on the Al2O3 substrate by MEMS process. Experimental results indicate that the micro solid-electrolyte CO2 gas sensor has a relatively rapid speed of response. By discussions, we may find that the improved performance will be realized by optimizing the primary parameters of the sensor.

scholarly journals Improved performance of stellarator coil design optimization

2020 ◽  
Vol 86 (2) ◽  
Author(s):  
Jim-Felix Lobsien ◽  
Michael Drevlak ◽  
Thomas Kruger ◽  
Samuel Lazerson ◽  
Caoxiang Zhu ◽  
...  
Keyword(s):  
Stochastic Optimization ◽  
Design Optimization ◽  
Three Dimensional ◽  
Local Maximum ◽  
Average Field ◽  
Test Case ◽  
Coil Design ◽  
Applied Optimization ◽  
Improved Performance ◽  
Coil Shape

Following up on earlier work which demonstrated an improved numerical stellarator coil design optimization performance by the use of stochastic optimization (Lobsien et al., Nucl. Fusion, vol. 58 (10), 2018, 106013), it is demonstrated here that significant further improvements can be made – lower field errors and improved robustness – for a Wendelstein 7-X test case. This is done by increasing the sample size and applying fully three-dimensional perturbations, but most importantly, by changing the design sequence in which the optimization targets are applied: optimization for field error is conducted first, with coil shape penalties only added to the objective function at a later step in the design process. A robust, feasible coil configuration with a local maximum field error of 3.66 % and an average field error of 0.95 % is achieved here, as compared to a maximum local field error of 6.08 % and average field error of 1.56 % found in our earlier work. These new results are compared to those found without stochastic optimization using the FOCUS and ONSET suites. The relationship between local minima in the optimization space and coil shape penalties is also discussed.

Modelling the Axial-Flow Compressors for Calculating Starting of Turbojet Engines

1985 ◽  
Author(s):  
Yan De-You
Keyword(s):  
Excellent Agreement ◽  
Axial Flow ◽  
Structural Formula ◽  
Experimental Results ◽  
Low Speed ◽  
Structural Formulae ◽  
Axial Flow Compressors

This paper provides a method of modelling the axial-flow compressors in the low speed starting regime of an engine from windmilling to idling. A structural formula for the model is established by means of reference (1). A method of step-by-step regression is provided by the author for determining the coefficient matrices of the structural formulae. Excellent agreement was obtained between the computational and experimental results.

Software Product Line Testing Based on Feature Model Mutation

2017 ◽  
Vol 27 (05) ◽  
pp. 817-839 ◽  
Author(s):  
Johnny Maikeo Ferreira ◽  
Silvia Regina Vergilio ◽  
Marcos Quinaia
Keyword(s):  
Software Product Line ◽  
Product Line ◽  
Experimental Results ◽  
Feature Model ◽  
Test Case ◽  
Test Cases ◽  
Mutation Operators ◽  
Software Product ◽  
Pairwise Testing ◽  
Feature Management

The Feature Model (FM) is a fundamental artifact of the Software Product Line (SPL) engineering, used to represent commonalities and variabilities, and also to derive products for testing. However, the test of all features combinations (products) is not always possible in practice. Due to the growing complexity of the applications, only a subset of products is usually selected. The selection is generally based on combinatorial testing, to test features interactions. This kind of selection does not consider different classes of faults that can be present in the FM. The application of a fault-based approach, such as mutation-based testing, can increase the probability of finding faults and the confidence that the SPL products match the requirements. Considering that, this paper introduces a mutation approach to select products for the feature testing of SPLs. The approach can be used similarly to a test criterion in the generation and assessment of test cases. It includes (i) a set of mutation operators, introduced to describe typical faults associated to the feature management and to the FM; and (ii) a testing process to apply the operators. Experimental results show the applicability of the approach. The selected test case sets are capable to reveal other kind of faults, not revealed in the pairwise testing.

Rigid Mode Vibration Control and Dynamic Behavior of Hybrid Foil–Magnetic Bearing Turbo Blower

2016 ◽  
Vol 139 (5) ◽  
Author(s):  
Sena Jeong ◽  
Doyoung Jeon ◽  
Yong Bok Lee
Keyword(s):  
Vibration Control ◽  
Dynamic Pressure ◽  
Magnetic Bearing ◽  
Experimental Results ◽  
Low Speed ◽  
Vibration Stability ◽  
Turbo Blower ◽  
Foil Bearing ◽  
Vibration Responses ◽  
Aerodynamic Instability

In this study, experimental and analytical analyses of the vibration stability of a 225 kW class turbo blower with a hybrid foil–magnetic bearing (HFMB) were performed. First, critical speed and unbalance vibration responses were examined as part of the rotordynamic research. Its shaft diameter was 71.5 mm, its total length was 693 mm, and the weight of the rotor was 17.8 kg. The air foil bearing (AFB) utilized was 50 mm long and had a 0.7 aspect ratio. In the experiments conducted, excessive vibration and rotor motion instability occurred in the range 12,000–15,000 rpm, which resulted from insufficient dynamic pressure caused by the length of the foil bearing being too short. Consequently, as the rotor speed increased, excessive rotor motion attributable to aerodynamic and bearing instability became evident. This study therefore focused on improving rotordynamic performance by rectifying rigid mode unstable vibration at low speed, 20,000 rpm, and asynchronous vibration due to aerodynamic instability by using HFMB with vibration control. The experimental results obtained were compared for each bearing type (AFB and HFMB) to improve the performance of the vibration in the low-speed region. The experimental results show that the HFMB technology results in superior vibration stability for unbalance vibration and aerodynamic instability in the range 12,000–15,000 rpm (200–250 Hz). The remarkable vibration reduction achieved from vibration control of the HFMB–rotor system shows that oil-free turbomachinery can achieve excellent performance.

Anisotropic Eddy Viscosity in the Secondary Flow of a Low-Speed Linear Turbine Cascade

2011 ◽  
Author(s):  
G. D. MacIsaac ◽  
S. A. Sjolander
Keyword(s):  
Turbulent Flow ◽  
Secondary Flow ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Leading Edge ◽  
Boussinesq Approximation ◽  
Pressure Probe ◽  
Turbine Cascade ◽  
Low Speed ◽  
Sst Turbulence Model

The final losses within a turbulent flow are realized when eddies completely dissipate to internal energy through viscous interactions. The accurate prediction of the turbulence dissipation, and therefore the losses, requires turbulence models which represent, as accurately as possible, the true flow physics. Eddy viscosity turbulence models, commonly used for design level computations, are based on the Boussinesq approximation and inherently assume the eddy viscosity field is isotropic. The current paper compares the computational predictions of the flow downstream of a low-speed linear turbine cascade to the experimentally measured results. Steady-state computational simulations were performed using ANSYS CFX v12.0 and employed the shear stress transport (SST) turbulence model with the γ-Reθ transition model. The experimental data includes measurements of the mean and turbulent flow quantities. Steady pressure measurements were collected using a seven-hole pressure probe and the turbulent flow quantities were measured using a rotatable x-type hotwire probe. Data is presented for two axial locations: 120% and 140% of the axial chord (Cx) downstream of the leading edge. The computed loss distribution and total bladerow losses are compared to the experimental measurements. Differences are noted and a discussion of the flow structures provides insights into the origin of the differences. Contours of the shear eddy viscosity are presented for each axial plane. The secondary flow appears highly anisotropic, demonstrating a fundamental difference between the computed and measured results. This raises questions as to the validity of using two-equation turbulence models, which are based on the Boussinesq approximation, for secondary flow predictions.

Magnetic Suspension for Low-Speed Vehicles

1978 ◽  
Vol 100 (4) ◽  
pp. 333-342 ◽  
Author(s):  
P. K. Sinha
Keyword(s):  
High Reliability ◽  
Suspension System ◽  
Urban Transport ◽  
Magnetic Suspension ◽  
Experimental Results ◽  
Performance Criteria ◽  
Transport Systems ◽  
Vehicle Suspension ◽  
Low Speed ◽  
Capital Costs

Several forms of novel suspension systems for passenger-carrying vehicles are currently being investigated throughout the world. Most of these, however, are aimed at high-speed, intercity transport systems, and comparatively less development work has been undertaken to provide a new form of low-speed system for urban-transportation. The possibility of using controlled direct-current electromagnets for low-speed (up to 70 kph) vehicle suspension has been explored in this paper. This system, also known as ferromagnetic or attraction suspension system, offers a very attractive combination of design simplicity, low operating and maintenance costs, high reliability and virtually silent operation. This system is also considered to have capital costs comparable with alternative forms of urban-transport systems and could be designed to fit into the existing fabric of cities and towns. The feasibility of the d-c system is illustrated here through analytical and experimental results of the ride and track-clearance characteristics for a single-degree of freedom suspension system. These results are used to formulate a procedure for designing a multimagnet vehicle suspension system. Main design and performance criteria for maglev vehicles are discussed in the context of experimental results obtained from test vehicles. Engineering aspects of some of the system components have been presented with a view to evaluating their suitability for low-speed systems.

Standard test case for a low-speed, turbulent junction vortex flow

AIAA Journal ◽  
1991 ◽  
Vol 29 (1) ◽  
pp. 14-15 ◽  
Author(s):  
F. J. Pierce
Keyword(s):  
Vortex Flow ◽  
Standard Test ◽  
Test Case ◽  
Low Speed
Sign in / Sign up

Export Citation Format

Share Document