vol #6-20-37 Feb 7, 2005 Softinway Inc.

AxSTREAM in Progress

BladeSlice - A GRAPHIC UTILITY FOR TURBOMACHINERY BLADES REVERSE ENGINEERING

Meeeting the industry needs in simple effective tools for reverse engineering, SoftInWay has developed a new product, namely BladeSlice. This compact tool, specially purposed for blade models graphic reproduction, adds new features to the industry accepted products used for turbomachinery blades reverse engineering , this way facilitating blade redesign and modernization.

Initial model of existing blade reproduced from IGES file

BladeSlice is easy-to-use, fast and convenient tool that strengthens designer capabilities in parameterization and visualization of any existing blade 3D model stored as IGES format file. The latter serves as initial data source for further processing, utilizing BladeSlice capabilities.

Selecting the surface for processing

BladeSlide allows users to:

Import an IGES file;
extract the data stored in IGES file;
process the extracted data, transforming obtained information in the utility structure presenting the objects as pointclouds;
find geometrical parameters, particularly, blade angles, including camber angle, and cross-section profiles;
form blade airfoil cross-sections (as pointcloud) over the airfoil region defined by designer interactively. At this, the sector taken for sectioning shouldn't include fillets near root and near shroud;
extrapolate the data extracted from a taken polygon to an entire airfoil hight selected by designer;
select a design space and the frame of coordinates (designer can select surfaces,curves, points, and axes);
visualize the selected part of blade model or the model in a whole and review it dynamically;
save the model as CURVE format file or text file.

"Select" dialog

"Slice settings" dialog

Boundaries of recognition domains and import areas

Virtually, BladeSlice work with or can be integrated with any CAD/CAE package as a post-processing graphic utility. Now it is integrated with AxSTREAM suite. BladeSlice was verified with Unigraphics, ProEngineer, and CFX BladeGen packages.

For more information, please address info@softinway.com

New Engineering Papers

STATISTICAL MODEL OF CASING TREATMENT INFLUENCE ON COMPRESSOR EFFICIENCY

Dr. Vitaliy Nezym, Professor

ABSTRACT
Circumferential grooves over a rotor blade tips are used for improvement of axial flow compressor performances. Such casing treatment means extend a stable operation range in the most cases, but decrease a compressor efficiency as a rule. There are presented the results of parametric investigation of grooves of traditional configuration. Optimizing groove constructions must permit increase in efficiency. Model on the base of Group Method of Data Handling /GMDH/ may help designing groove constructions with improved performances.

Keywords: compressor, efficiency, casing treatment, entire annular recess

NOTATION
- tip clearance, mm
- change of parameter
- total compressor peak efficiency, %
- number of grooves
- effective tip clearance, mm
- depth /of groove; of flow duct/, mm
- length, mm
- distance of groove location, mm
- rotor outer diameter, mm
- rotor hub/tip patio
- blade aspect ratio
- head coefficient
- flow velocity coefficient
- flow circumferential velocity,
- constant
- correlation coefficient

Subscripts
IGV - inlet guide vane
- rotor
GV - guide vane
- groove
- device
- crosspiece
1 -at the inlet /of groove; of rotor/
2 - at the outlet /of groove; of rotor/
- projection of blade chord
- tip
T - theoretical
- axial
red - reducted
exp - experimental
mod - model

INTRODUCTION
An aerodynamic perfection of multistage axial compressor /Fig. 1/ is one of the important ways for improving gas turbine plants efficiency. Effectiveness of compressor operation depends upon energy loss level in the compressor passages both at design and off-design regimes. The particular role in these processes plays also the presence of aerodynamic wakes after blade, flow distortion occurrence and flow behavior in hub and tip zones. A rotor /R/ row located between guide vanes /GV/ has the most complicated conditions of flow passing. This flow zone features proximity of rotating and fixed blade rows, buildup of endwall boundary layers, interaction of various forms of boundary layers at the blades and casings, the presence of leakage and secondary flows.

The presence of tip clearance between rotor blades and outer casing, increasing tip clearance with time is a significant cause of compressor performance deterioration, and efficiency and stable operation range as well. Applying of abradable inserts /linings/ in the casing above rotating blades permits to reduce this tip clearance and to compensate partially its negative influence. But it is not a complete solution of the problem, the possibilities of performance improvement are not used in a proper way.

There are several ways of energetic influence upon the tip zone flow, so-called active and passive flow control means. An active flow control is attractive one, in particular, due to absence of additional external energy use. One of the progressive means of a passive flow control in a compressor duct is casing treatment.
A casing treatment in the form of various orifices, slots and grooves /Fig. 2/ in compressor casing above rotating blades is used traditionally for extension of compressor stable operation margin [1-5]. Historically, a casing treatment as annular circumferential grooves in a casing over rotor blades with a tip clearance is the most known one. Such construction is featured by very high simplicity.

It is important that in most cases increasing a stable operation range is accompanied by decreasing a compressor efficiency. But the positive results are possible too. For example, in the work [6] seven grooves of 9.5 mm height and 1.6 mm width were used for improving a compressor stage performance. As a result, maximum adiabatic efficiency was increased for the uniform inlet flow: by 0.95% at relative rotor speed 1.0; by 4.76% at 0.9; and by 3.09% at 0.7 relative speed.

Usually, the problem of grounded optimization of a slot size and configuration is rather important . Some results of experimental investigation concerning a variety of annular grooves in an axial compressor casing are presented below.

INVESTIGATION
1 Results of grooves investigation
Groove tests were performed at the special experimental test rig. While testing, the total pressure was measured upstream amd downstream of the rotor by five-duct radial combs installed at chosen fixed points in the circumferential direction. Measurement of the total pressure field after guide vane was performed with the help of five-duct radial comb traversing in the circumferential direction. This procedure was accompanied by averaging of the measurement along the cascade space and the blade height. Test data were obtained and processed with an automated data system. The efficiency was determined with the help of hunting stator usage at ±0.3% accuracy.

The changes in the experimental rotor efficiency were calculated as the follows:

= (%) /1/,

where and - isentropic total compressor peak efficiencies with and without grooves.

A pattern of typical circumferential groove over a rotor blade /Fig. 3/ may be characterized by number of grooves ng, three radial // and five // geometric dimensions. Further, it will be more suitable to use some relative geometric parameters /for example, etc./.
Note: is a blade chord projection and - a blade height at the rotor inlet.

The main geometric parameters of tested objects are presented in Table 1, the main geometric characteristics of applied grooves and results of the investigation - in Tables 2 a, b. Several types of tested groove configurations /1-1, 1-2, 1-3, 1-2.5, 10/ are shown at Fig. 4 /Data of grooves HEMS-1, VI-0, A, B, C are in Tables 2 a, b/. And some conclusions of the tests are as follow:

Change of groove depth from 5 to 15 mm /device HEMS-1 at the compressor stage HEMS/ did not alert practically an efficiency change /see Table 2a/.
Change of an inlet distance of groove location t1/and t2, correspondingly/ was investigated with device VI-0 at the compressor stage AI-24-VI and devices 1-1, 1-2, 1-3, 1-2.5 at the stage AI-24-IX. As it is seen from Fig. 5, it is useful to increase/decrease t1 as to certain range for every stage.
Influence of effective tip clearance in the range from 0.4 mm to 1.5 mm /under constant tip clearance equal 0.4 mm/ was investigated at the compressor rotor AI-24-R-VIII with devices 1-2.5 and 10. The results have the similar quantative character /Fig. 6/. It is useful to decrease -parameter for the compressor efficiency, besides, the device 1-2.5 was more effective one.

Some tests were performed at the compressor rotor AI-24-R-VIII, with devices A1, A2, B and C. The device A1 of typical form was intended for research of the influence of groove depth / =1; 2.5; 5; 10mm/. /. Another one /device A2/ served for testing a groove solidity /lg= lc=1mm in this variant in contrast to lg= lc=2mm in all other variants/. The third and fourth /variants B and C/ were necessary for evaluation of additional groove before and after the origin device /t1=t2=4mm/.

As it is seen, variation of groove depth /from 1 to 10 mm/ has practically constant influence upon efficiency /Table 2b/. Also, it was not observed a significant influence of groove solidity change in two cases /device A2/. An additional groove before blades /device B/ gave more negative and after blades /device C/ - rather low negative effect on a stage efficiency.

2 Use of Group Method of Data Handling
The data resulting from the large amount of testing have enabled compressor designers to utilize casing treatment for improving performance and/or stability of axial flow compressors. However, attempts to optimize a groove configuration have been conducted almost entirely by empirical methods. In particular, there is at present no fundamental theoretical understanding of the mechanism by which the grooves alter the behavior of the compressor. So development and creation of the proper statistical models are rather progressive ways currently.

The obtained experimental data may serve as initial ones for developing a statistical model of groove casing treatment behavior.
Automatic System of Modeling /ASM/ on the base of algorithms of the Group Method of Data Handling /GMDH/ [7, 8] serves for effective models constructing. It is an original method of solving the problems of structure-parametric identification of models or modeling as to experimental data in uncertainty conditions. Such task provides obtaining the mathematical model approximating unknown law of functioning of studied object /process/, information about which contains non-explicitly in the sample /massive/ of existing data. The Group Method of Data Handling differs from other methods by effective applying of principles of the active control of variants and non-finished solutions generation, and then sequential selection due to exterior criteria for constructing of optimal complexity models.

So, the Group Method of Data Handling procedure includes optimization of the model structure and parameters with the help of expedient exhaustive search of automatically generated model variants in the certain class of basic functions and sequent choice of the best models as to exterior criteria based on the sample division.
For the model development it was applied the program of structural identification of algebraic models with orthogonalization of particular descriptions and with regularity external criterion.

The groove geometric parameters in relative form were considered with respect to their influence on compressor efficiency / /. The choice of these parameters was proved by preliminary use of GMDH-algorithms. Relationships between every groove parameter and efficiency change are presented at Fig 7. As it is seen, the experimental results of separate influences have rather large dispersions and low correlation coefficients.

Application of GMDH-method has permitted to unite the influence of several parameters to one relationship /Fig. 8/. It is the direct relationship between experimental ( ) and model ( ) efficiency change (the latter is obtained with the help of GMDH algorithm). This function accounts for the influence of six arguments /parameters/ chosen by GMDH and has relatively low dispersion (2.11) and rather high correlation coefficient (0.80), featuring high accuracy of the model.

Formula of the corresponding relationship for efficiency change:

/2/

where:

- constants.

Test point /small black circle/ features an influence of the groove configuration with the parameters [6]:

As it is seen; the test point is located relatively close to the function line.

And then, special calculations with the help of the developed model formula have permitted to estimate a degree of every parameter influence on the final function. It was concluded that the most effect have and and in the order change. Such results may be useful for a practical casing treatment design.

CONCLUSIONS
1. Circumferential grooves in an axial compressor casing over a rotor blade tips is an effective means for compressor performances improvement.
2. In some cases it is possible to increase compressor efficiency under optimal combination of groove geometry.
3. A significant change of grooves total depth and solidity does not effect considerably upon the performances.
4. The developed statistical model of grooves influence upon compressor efficiency may be useful for a practical designing.
5. and parameters may be considered as especially influencing ones.
6. Perfection of groove casing treatment configurations and models requires new tests and investigations.

REFERENCES

1. H. Takata, Y. Tsukuda, Stall Margin Improvement by Casing Treatment - its Mechanism and Effectiveness. Transactions of the ASMR, Journal of Engineering for Power, Vol. A99, No. 1, 1977, pp. 121-133.
2. E. M. Greitzer, J. P. Nikkanen, D. E Haddad., R. S. Mazzawy, H. D. Joslin,
A Fundamental Criterion for the Application of Rotor Casing Treatment. Transactions of the ASME, Journal of Fluids Engineering, Vol. 101, June 1979, pp.237-243.
3. V. N. Yershov, A. P. Efimenko, V. Yu. Nezym, Use of Casing Treatment at Increased Tip Clearances of Compressor, Izvestiya Vysshikh Uchebnykh Zavedenij. Aviatsionnaya Tekhnika, No. 3, 1984, pp. 93-96.
4. G. D. J. Smith, N. A. Cumpsty, Flow Phenomena in Compressor Casing Treatment, Transactions of the ASME, Journal of . Engineering for Gas Turbines and Power, 1984, Vol. 106, No. 3, pp. 532-541.
5. G. N. Zvereva, N. M. Savin, Effectiveness of Casing Treatment Use in Rotor of Axial Flow Compressor, Gas Dynamics of Engines and their Elements, Is. 2, 1983, pp. 96-101.
6. W. M. Osborn, G. W. Jr. Lewis, L. J. Heidelberg, Effect of Several Porous Casing Treatment on Stall Limit and on Overall Performance of an Axial- Flow Compressor Rotor, NASA Lewis RC, TN D-6537, 1971.
7. A. G. Ivakhnenko, Yu. P. Yurachkovsky, Complicated Systems Modelling Using Empiric Data, Radio and Communications, Moscow, 1987, 120pp.
8. Ivakhnenko, A.G., "Articles, papers, books and software on the Group Method of Data

Handling (GMDH)", web-site: www.gmdh.net/articles.

List of figure and table captions
Fig. 1 Typical axial compressor
Fig. 2 Various types of casing treatment configurations
Fig. 3 Main geometric parameters of groove configuration
Fig. 4 Several types of tested groove configurations
Fig. 5 Influence of inlet distance of groove location upon efficiency change
Fig. 6 Influence of effective tip clearance upon efficiency change
Fig 7 Influence of groove geometric parameters upon compressor efficiency changes
Fig. 8 Relationship between experimental and model changes of compressor efficiency
Table 1 Main parameters of tested objects
Table 2 a, b Main geometric parameters and results of investigation of applied groove configurations

Table 1. Main parameters of tested objects

Turbomachinery design with AxSTREAM

AxSTREAM VALIDATION ASPECTS: OEM AVIATION GAS TURBINE

SoftInWay has carried out AxSTREAM validation against the results extracted from OEM axial gas aviation turbine testing.

An aviation full-scale gas turbine purposed for numerical simulation with AxSTREAM is a high-loaded low pressure turbine of the turboshaft engine. One of the study objectives was to perform 1D, 2D, and 3D modeling and validate some results versus the test data obtained by experiment.

The turbine under study featured low flow rate coefficients at high load factors, (Figure 1, left). It belongs to so called low-head turbines and this entails its design and aerodynamic peculiarities such as transition duct of complicated shape at inlet; significant gas path expansion (up to 30 deg); comparatively wide 1st stage diaphragm with height to axial chord ratio h/bx~1.2; high-load stages with 1st and 2nd stages loading factor µ>2.5.

Within the frame of the study, meanline and axisymmetric analyses were performed using AxSTREAM software. General cascade characteristics such as chords, metal and gauging angles, gap and clearing dimensions, operational conditions were taken as initial data for analyses. Resulted was a simplified turbine model shown in Figure 1, right. Principally, AxSTREAM possesses ample capabilities for axial turbine aerodynamic analysis, but in this case, 1D and 2D computations completely met the objectives of the study that was reduced to modeling results validation against the test data obtained for static pressure in the flow path gaps.

Figure 1. Pilot turbine layout (left) and its model obtained with AxSTREAM (right)

The sample of the AxSTREAM, CFX-5.7 computation results and test data comparison is presented in Figure 2. The figure show that computed and extracted from experiment pressure values have a good convergence.

Figure 2. Experimental and computed with AxSTREAM and with CFX5.7 static pressures in axial gaps near hub (left)
and near tip (right)

3D simulation was carried out with CFX-5.7 solver. Figure 3 and Figure 4 depict a final 3D model with streamlines contours and models of 3 stages obtained with CFX-5.7 and with AxSTREAM, respectively.

Figure 3. 3D model of the flow path and streamline contours obtained with CFX-5.7

Figure 4. Models of the flow path and streamline contours obtained with AxSTREAM for 3 stages

Figure 2 explicitly demonstrates a sufficiently good convergence of the data extracted from experiment and computed with the help of AxSTREAM and CFX-5.7 solvers for all kinds of simulation applied, i.e. for unidimensional, axisymmetric and three-dimensional modeling.

Please address tech_support@softinway.com for more information.

Openings in SoftInWay

Welcome to join SoftInWay Incorporate! We invite you to explore the vacancies presented below:

CAE Software Developer

This individual should have experience in development of complex engineering software projects and a strong background in CAE tools. Excellent understanding of FEA and / or CFD methods and issues. It is essential that the individual has a strong desire to learn and explore new technologies and is able to demonstrate good problem solving skills.

Requirements:

• B.Sc., or M.Sc., or Ph.D. in Mechanical Engineering, Applied Math or Physics with respectfully 5+, or 3+ , or 0-1 years of experience in engineering software development (C, C++, FORTRAN);

• Thorough knowledge of FEA and / or CFD methods;

• Hands on experience with at least one of the following tools: ANSYS, MSC.Software, ABAQUS, I-Deas, CATIA, Fluent, or CFX. Experience with SolidWorks and / or Pro/E is a plus.

Project Manager, Engineering Consulting
This individual will be responsible for all-round technical preparation and evaluation of project proposals in FEA-based CFD, Heat Transfer, Stress- Strain areas. Recommending improvements, the project’s technical issues coordination including problems’ review, sophisticated model description, precise boundary conditions evaluation, and gathering and analysis of other data required for providing further non-stop development process.

Also responsible for building and maintaining development schedules and fulfilling project deliverables on time, from inception to client sign-off. Beyond this, the candidate needs to have very sharp analytical skills, which s/he will use through the project life cycle, including detailed pre-development proposal analysis, projects feasibility estimation, and user requirements analysis.

Requirements:

Masters Degree or Bachelors in Mechanical Engineering with significant related experience at Power Generation Machinery oriented companies like GE, Pratt & Whitney, Rolls-Royce, Alstom. Computed Science Degree is desirable.
5+ years of complex Mechanical Engineering project management, engineering application development, design, and implementation experience.
Experience in FEA-contained packages’ implementation like ANSYS and/or similar toolkits is required.
Principle knowledge in CFD, Heat Transfer, Stress-Strain, Machine Design is extremely appreciated.
Must be strongly focused and extremely organized.
Proven experience in writing specifications, quality assurance, project complexity, labor effort estimation, and risk analysis skills.
Exceptional oral and written communications skills are essential.
PMI certification is a plus.

Sales Engineer/Project Manager

The essential job function of this person is business development and sales of engineering/software development consulting services including:

- forecast development to achieve national sales goals,

- developing and implementing a strategic sales plan to achieve national sales goals;

- identify, close and maintain key accounts;

- provide information to marketing to improve products and profitability;

- monitor and assess major competitors' activities and products.

The person will perform sales work inside and outside in support of SoftInWay's engineering services for diverse industries including Aerospace, Power Generation, Automotive, Energy, Petrochemical, Utilities, Gas, etc. He/She will prepare proposals or service contracts for SoftInWay's engineering services with deep understanding of customer requirements and company's team Design and Engineering abilities in FEA-based CFD, Heat Transfer, and Structural applications development. Coordinate and schedule marketing activity. Serve as Project Manager for various projects, both temporary and ongoing.

Requirements:

• Minimum 4 year Degree in Mechanical Engineering or related areas with significant related experience at Power Generation Machinery oriented companies like GE, Pratt & Whitney, Rolls-Royce, Alstom.
• 5 - 8 years experience of surpassing sales quotas in selling consulting services to C-level executives in engineering and scientific.
• Principle knowledge in CFD, Heat Transfer, Stress-Strain, Machine Design, CAD/CAE, and Visualization is appreciated. Knowledge of MS Office and MS Project is a plus.

• Excellent prospecting and presentation skills .
• Must be strongly focused and extremely organized.

• Exceptional oral and written communications skills are essential.