These abstracts describe a select collection of Concepts NREC technical papers. You may download a copy immediately (PDF version, Acrobat Reader required. Click here to get a free version of the reader) or to receive a full-text version of any of these papers by mail, please contact us.
"Vaneless Diffuser
Advanced Model" (257 KB)
Presented at ASME Turbo Expo 2005: Power for Land, Sea and
Air, June, 2005, Reno-Tahoe, NV
A new vaneless diffuser model is presented. Upon thorough examination
of the change in average total pressure, the average static pressure
and the average flow angle through a vaneless diffuser, it was
discovered that existing models fail to provide useful integrity.
Consequently, a new model was built. It was learned that it was
necessary to use a two-zone model of the flow entering the vaneless
diffuser and to carefully model the two-zone degradation as the
flow passes through the vaneless diffuser. The new model is presented
with detailed testing. The impact upon future design is outlined,
and the expectation is established that various future designs
will require the integrity of the new model; old models can be
used in limited cases with care.
"Turbomachinery Modeling:
Explicit and Implicit Knowledge Capturing" (304 KB)
Presented at ASME Turbo Expo 2005: Power for Land, Sea and
Air, June, 2005, Reno-Tahoe, NV
Design engineers rely on quality performance models to establish
the physical relationship between diverse thermodynamic, geometric,
and fluid dynamic parameters that govern turbomachinery performance.
If these models are based on a rigorous, scientific foundation,
they permit the designer to thoroughly optimize a new configuration
and establish with confidence the performance levels to be expected
when the product is introduced in the market. The process of developing
advanced models has endured more than a full century, and models
of increased complexity have been introduced. However, many aspects
of model development have not received thorough scientific evaluation.
In the turbomachinery field, meanline performance models for axial
turbines have been well developed and widely published; nearly
the same can be said for the field of axial compressors. Beyond
these two examples, there is a need for more model development
and improvement, particularly emphasizing radial and mixed-flow
turbomachines. This paper shows a systematic method, now fully
integrated into a computerized methodology with optimization search
techniques, for extracting the greatest useful knowledge from
diverse datasets suitable for subsequent model development. The
process focuses on modeling eight dependent variables based on
five or six independent variables that have been found to be essential
for understanding the performance of these machines. This paper
emphasizes the scientific and numerical approach taken to process
the data such that advanced models can be developed. The actual
model development is presented in subsequent papers.
"Multi-Variable,
High Order, Performance Models" (609 KB)
PROVISIONAL DRAFT - Paper presented may be different than
paper available here. To be presented at 2005 ASME International
Mechanical Engineering Congress & Exposition, November, 2005 Orlando,
Florida, USA
In the course of developing advanced data processing and advanced
performance models, as presented in companion papers, a number
of basic scientific and mathematical questions arose. This paper
deals with questions such as uniqueness, convergence, statistical
accuracy, training, and evaluation methodologies. The process
of bringing together large data sets and utilizing them, with
outside data supplementation, is considered in detail. After these
questions are focused carefully, emphasis is placed on how the
new models, based on highly refined data processing, can best
be used in the design world. The impact of this work on designs
of the future is discussed. It is expected that this methodology
will allow many designers to move well beyond contemporary design
practices.
"Turbomachinery Performance
Models" (240 KB)
PROVISIONAL DRAFT - Paper presented may be different than
paper available here. To be presented at 2005 ASME International
Mechanical Engineering Congress & Exposition, November, 2005 Orlando,
Florida, USA
Advanced meanline turbomachinery performance models are presented
based on an extensive database for centrifugal and mixed-flow
compressors and pumps. The methodology of processing the data
is briefly discussed here, and in more depth in a companion paper.
In this investigation, the detailed steps of building the highly
non-linear, multi-variable, coupled models are presented. This
modeling includes the impeller, a vaneless diffuser, and/or a
volute. In future papers, diverse classes of diffusers, guide
vanes, and return channels will be added as well. Using genetic
expression programming, models of very high order are developed.
These models are then tested against neural network models that
are built using the same database. Several different classes of
performance models are built to meet global modeling requirements,
specific discipline domain requirements, and to meet specific
designers’ requirements.
"Radial
Turbines: An Integrated Design Approach" (356 KB)
To be presented at the 6th European Turbomachinery Conference
- Fluid Dynamics and Thermodynamics, March 2005, Lille, France
An integrated design system permits rapid and cost-effective
design optimization of radial turbines. A preliminary design and
analysis procedure allows the key turbine dimensions to be specified
and the performance predicted at an early stage. This uses a mean
line model of the turbine that has been extensively calibrated
against test data. Recent developments to the model are described
here. The use of CFD in the design process is also considered.
The availability of fast CFD solutions allows them to be used
early in the design process and to great benefit. Even a relatively
low-resolution CFD solution is able to identify features in the
flow field that inviscid two dimensional solutions miss entirely.
This has now developed to the extent that it is questionable whether
2D solutions still have a role in radial turbine design. However,
CFD remains limited. High resolution solutions are shown able
to predict the loss of a blade row to an accuracy sufficient for
many design purposes, but deviation angles still cannot be accurately
predicted, even for simple two dimensional stator blades.
"Optimization in Turbomachinery
Data Reduction" (350 KB)
Presented at the 10th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery,
Honolulu, Hawaii, March 2004
This paper presents a thirty-year experience in synthesizing quality datasets to reveal basic model trends in
centrifugal pump and compressor stages, with extension also to a few axial stages. The paper first presents a
variety of data types that are available, historical overviews concerning the database development procedure,
and a survey of the accuracy of available data. A careful evaluation of the fluid dynamic parameters that can be
investigated by a study of basic laboratory data follows. In turn, a data synthesis process to model analytically
the trends represented in the data is presented. Detailed examples of studying diffusion and loss, secondary flow,
and deviation within radial wheels, plus skin friction models for vaneless diffusers, plus volute modeling improvement
are presented as typical examples, as well as a discussion of the now wellestablished TEIS model of impeller diffusion/loss.
This work uses optimization search procedures to find the best synthesis of data and design models. Following historical
footnotes of the previous years’ investigations, recommendations for further improvement and conclusions are presented.
"An Evaluation of Neural
Networks for Meanline Model Development" (502 KB)
Presented at the 10th International Symposium on Transport
Phenomena and Dynamics of Rotating Machinery, Honolulu, Hawaii,
March 2004
A large database of meanline performance modeling parameters,
covering a wide array of centrifugal compressors and pumps, plus
a few axial machines, has been assembled by Concepts NREC. Neural
Networks are one tool that might be used to extract substantive
relationships from prior design and test experience. This paper
presents an early investigation of neural network models applied
to the available database. Resulting lessons are shared, and several
resulting examples are given. Suggestions for future development
are offered.
"Optimization in Component
Design and Redesign" (1.77 MB )
Presented at the 10th International Symposium on Transport
Phenomena and Dynamics of Rotating Machinery, Honolulu, Hawaii,
March 2004
A unique method for the design of industrial compressors and pumps
has been created, which brings a thoroughly integrated system
of advanced technology to the fingertips of design engineers.
The Expedited Agile System (EASy!™) integrates initial
meanline design, sophisticated three-dimensional blading design,
and the essentials of modern Computational Fluid Dynamics (CFD)
procedures. Using the optimization code, iSight, one is able to
develop specific vane shapes in comparatively short time. Thorough
use is made of past design experience and historical performance
data through a Knowledge-Based Engineering (KBE) system while
guiding designers to proven design technique, as well as to validate
and calibrate design tools for current applications. A detailed
design example is included.
"Opportunities in University
Collaboration for Turbomachinery Development: A Turbomachinery
Perspective on Engineering Education" ( 292 KB)
Presented at the 10th International Symposium on Transport
Phenomena and Dynamics of Rotating Machinery, Honolulu, Hawaii,
March 2004
A specific industrial perspective is given on possibilities to
enhance teaching of turbomachinery in academia and in industry
with a view towards preparing engineers for an industrial career
in this area. Additionally, opportunities for research investigations
are presented and prospects to sustain quality research with industrial
collaboration are reviewed. Finally, opportunities for student
involvement in the ongoing research and development aspects of
work at Concepts NREC (the Company) are summarized and presented.
It is not suggested that this presentation is broadly based; generally,
industry and universities have limited collaboration. However,
this presentation does draw on several successful experiences
shared between the Company and different universities. In this
spirit, suggestions for further collaboration in a complex international
society are offered.
"Application of a New
Turbine Design System to Rocket Turbopumps" (1.21 MB)
Presented at the U.S. Joint Army, Navy, NASA, Air Force (JANNAF)
Conference, Colorado Springs, December 2003
This paper describes the preliminary design process for turbines
used in rocket propulsion applications. Two sample turbopump cases
are discussed to illustrate the key aero design considerations
for both reaction and impulse designs. A new reduced order through-flow
solver algorithm serves as the foundation for various meanline
analysis functions, such as flow path sizing, performance optimization,
and investigation of design parameter sensitivities. This modeling
approach is shown to provide a versatile and accurate preliminary
analysis for rocket turbopump turbines. It has been integrated
into a comprehensive blade design system, called the
Agile Engineering Design System®, that enables the smooth
evolution of a design from initial conceptual studies to final
detailed design.
"The
Reduced Order Through-Flow Modeling of Axial Turbomachinery
" (663 KB)
Presented at the International Gas Turbine Congress (IGTC),
Tokyo, November 2003
A new reduced order through-flow analysis system for the preliminary
design of axial turbomachines is presented. It has flexible models
for losses, deviation, blockage, etc., uses real gas/liquid thermodynamics
and handles flow and geometry at three spanwise locations. It
is applicable to both compressors and turbines of either subsonic
or supersonic flow type. The essential features of the system,
including a comparison of its predictions with test data, are
presented in the paper.
"Hydrodynamic
Analysis of Two 3D Axial Flow Pumps" (1.12 MB)
Presented at the International Mechanical Engineering Congress
& Exposition (IMechE), November 2003
A study of two industrial axial flow pumps using the same impeller,
but with one employing a 90° elbow upstream and the other
with a 90° elbow downstream, has been conducted. Common design
tools, ranging from 1D to fully 3D non-axisymmetric, time-dependent,
have been employed. Significant value has been gathered at each
level of evaluation and the quandary over the 90° elbow upstream
versus downstream has been resolved.
"Multidisciplinary Optimization
Applied to a Turbocharger Compressor Impeller" (1 MB)
Presented at the IXth International Conference on Rotary Fluid-Flow
Machines, October, 2003, Rzeszow, Poland
The multidisciplinary optimization (MDO ) design of a compressor
impeller was completed after replacing titanium with aluminum.
A two-step optimization method was used. Loop 1 combined quasi-3D
aerodynamic methods and blade-alone FEA models, with reduced blade
stress goals while matching blade loadings. Loop 2 used a 3D pie-slice
FEA model with a decreased bore stress goal. The redesigned aluminum
impeller has acceptable stresses with only one point efficiency
fall. Practical MDO work is now possible. Designers must establish
design goals/weighting factors and assemble proper optimization
plans for time-effective optimization schemes.
"Application and
Validation of CFD in a Turbomachinery Design System"
(1.8 MB)"
Presented at ASME International Mechanical Engineering Congress
and R&D Expo, November 2003, Washington, D.C.
CFD has enjoyed widespread use in the turbomachinery industry
for some time. When coupled with other solvers, such as meanline
and streamline curvature, it can be an integral part of a comprehensive
design and analysis system. The Pushbutton CFD product is the
CFD component of Concepts NREC's Agile Engineering Design System.
It is a structured grid CFD flow solver optimized for turbomachinery
analysis.
Concepts NREC has made an extensive validation effort over a wide range of diverse turbomachinery stages including, compressors, pumps, and turbines for both radial and axial machines. Detailed comparison to test data of 10 different stages is shown in this paper and clearly demonstrates the high performance of Pushbutton CFD in quantifying fluid dynamic losses and pressure changes over a wide range of geometries and flow conditions.
"Multidisciplinary Optimization
of a LH2 Turbopump Design in an Agile Engineering Environment"
(811 KB)
Presented at the American Institute of Aeronautics and Astronautics
Joint Propulsion Conference and Exhibit Von Braun Center, Huntsville,
Alabama, July 2003.
The subject of this paper is the multidisciplinary optimization
of an upper stage liquid hydrogen turbopump designed for private
launch applications, handling 14 lbm/sec mass flow at 77,900 rpm
[1,2]. The paper describes the preliminary meanline and quasi-3D
hydrodynamic analyses, which were performed to determine a starting
point for the design. The baseline hydrodynamics, stress, vibration,
and weight are presented and the design targets are discussed.
In this paper, the liquid hydrogen turbopump is taken from the
preliminary design phase through several steps of design optimization.
The paper describes the hierarchical optimization process, and
demonstrates that the multidisciplinary set of objectives was
met and discusses how significant gains over previous designs
were realized.
"Radial and Mixed Flow
Turbine Options for High Boost Turbochargers" (694 KB)
Presented at the 7th International Conference on Turbochargers
and Turbocharging, May 2002
This paper demonstrates that there are definite and predictable
limits to the boost pressure obtainable when the turbocharger
compressor is driven by a conventional single stage radial turbine.
Present engine requirements go beyond these limits. The usual
solution is a series turbocharging arrangement which brings additional
complexity and parts count. Alternative single stage turbines
for high boost pressures are investigated. It is shown that mixed
flow turbine concepts can achieve stage loadings that are about
20% greater than those of a conventional radial turbine, without
any increase in blade speed and maintaining structural integrity.
The design of such a turbine is described. Current developments
in new turbine rotor materials offer an alternative route to this
goal, and the prospects for this are also considered.
"Thermo-Mechanical Turbopump Design and Analysis Tools" (694 KB)
The design and analysis tools developed in this project improve the turbopump design process through data synthesis of component models, encompassing information from pump and turbine designs, in addition to shafts, bearings, seals, and internal flows. The combined toolset provides the ability to
address static, quasi-static, and transient thermo-mechanical requirements sooner in the design process, improving the design cycle time and overall life and reliability of the turbopump system.
"Decisive Factors in Advanced Centrifugal Compressor Design and Development" (488 KB)
Presented at the International Mechanical Engineering Congress & Exposition (IMechE), November 2000
The design of advanced turbomachinery has been practiced in the last half of the previous century with increasing degrees of sophistication while continuously advancing levels of efficiency and regimes of stable operation. This trend of development is not complete; products have not reached a level of full maturity. There is considerable room for further development of most turbomachinery products today when looked at with the perspective of the broadest possible design world. Modern design no longer concerns itself only with efficiency and stability, but adds significant issues of weight, life, cost of manufacturing, marketability, and so forth. Decisive factors in each area are considered in this paper and consideration is given to developing trends.
"Design Study of a Low-Cost LOX Turbopump" (138 KB)
Presented at the Thermal & Fluids Analysis Workshop (TFAWS), August 2000
A preliminary design study, focusing on potential component selections and Design for Manufacturing and Assembly (DFMA®) analysis, is presented. The investigation was focused on a low-cost liquid oxygen turbopump suitable for a private launch class vehicle. Utilizing a "turbocharger-like" design philosophy, preliminary feasibility studies of the basic pump design class, the rotordynamic design class, and the turbine design class were conducted with associated DFMA evaluations. Reasonable cost levels and sensible levels of product assurance have been established.
"Sidestream Optimization
Through The Use Of Computational Fluid Dynamics And Model Testing" (789 KB)
Presented at the 29th Turbomachinery Symposium, Sept. 2000.
The development of sidestreams for industrial centrifugal compressors
presents many difficult challenges for aerodynamic designers.
Most often, past practice dictated the configurations used for
new applications. However, as end user's demanded higher performance
and improved predictability, better design methodologies had to
be developed. More effective use of computational fluid dynamics
(CFD) codes was an obvious solution. However, to properly use
such codes, they must be calibrated or validated against available
test data. To this end, the OEM funded an extensive project combining
model testing with detailed CFD analyses. The goal was to establish
more rigorous design and analysis guidelines for incoming sidestreams.
"Correlation of Annular
Diffuser Performance with Geometry, Swirl, and Blockage" (111 KB)
Presented at the Thermal & Fluids Analysis Workshop (TFAWS),
August 2000
A correlation set of annular diffuser performance relationships
has been developed. The relationships are based on all of the
experimental data available from the known open literature and
covers basic diffuser geometry, inlet aerodynamic swirl, and inlet
aerodynamic blockage. A sensible baseline correlation has been
established which is suitable for preliminary design of some turbine
systems. It has also been established, however, that the world's
existing technical literature is deficient in a number of important
variables and a resultant level of data variance has been established
which should be reduced in future investigations. This paper establishes
a baseline for current work and goals for future development.
"Application of Design for Manufacture and Assembly Methodologies to Complex Aerospace Products" (473 KB)
Presented at the 36th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, July 2000
Design for manufacture and assembly methods have been in widespread use in consumer product industries for over a decade. Principal benefits have been reduction of product development cost and an increase in product quality and competitiveness. Current research is focused on the application of design for manufacture and assembly to the lower-volume production of highly engineered products, such as those found in the aerospace industry. This paper presents highlights of a case study under way on a turbopump designed by NASA's Marshall Space Flight Center under the Low Cost Boost Technology Project.
"Characteristics of a Radial Inflow Turbine with Internal Component Measurements, Part 1: Data Review" (530 KB)
Presented at the IGTI Turbo Expo, May 2000
The design and off-design performance of a radial inflow turbine has been carefully measured with both internal component and overall stage data. Observations have been made concerning instrumentation methods, appropriate correlating variables, and resultant component performance. The use of internal measurements changes the conclusions reached concerning component performance. Recommendations for further analysis are given.
"The Validation of Rapid CFD Modeling for Turbomachinery" (627 KB)
Presented to the Institution of Mechanical Engineers, December 1999
Good CFD calculations can be made to guide advanced turbomachinery design and development. The computing time and storage requirements, however, differ greatly from one computational approach to another and the resultant accuracy may well be debated. One specialist has suggested that most of the important effects in a turbomachinery blade row might be resolved using a coarse grid of only 30,000 nodes, while others insist on grids with ten times this node count. Arguments abound concerning the use of a wall law function as an engineering expedient. The present study draws on a set of seven different stages, for which much measured data are available, and provides answers of sufficient depth to guide engineers in the economical utilization of their CFD tools. A base for rapid calculations is established; it is expected that the design future will focus intensely on agile, easy CFD as a base for advanced design development.
