Technical Papers
Technical Papers
These abstracts describe a select collection of Concepts NREC technical papers. Any complete full-text version may be downloaded as a PDF file (Acrobat Reader required*). You may also contact Concepts NREC to receive a full-text version of any of these papers by mail.
*Click here to download a free version of Acrobat Reader
"Meanline Modeling of Radial Inflow Turbine with Variable Area Nozzle"
Presented at ASME Turbo Expo 2009: Power for Land, Sea and Air GT2009
June 8-12, 2009, Orlando, Florida USA
A meanline model of a radial inflow turbine with a variable geometry nozzle is presented. The existence of a clearance gap in a variable geometry nozzle presents a significant challenge in the prediction of turbine performance. First, the nozzle clearance carries a portion of the flow that is not turned by the nozzle vanes. The amount of flow in the clearance region is related to the size of the clearance as well as the nozzle setting angle or the throat area. This under-turned flow influences the power output and turbine efficiency. Furthermore, the maximum flow rate that is allowed to pass the nozzle is increased because of the presence of the clearance, altering the turbine map in turbine operation.
(Download PDF)
"Turbomachinery Performance Modeling"
David Japikse, Concepts NREC
Analytical modeling of turbomachinery components and systems has been used for more than a century to develop new machines and understand internal flow states. Flow modeling basics are reviewed in this survey including a summary of the flow processes observed in nature. The development of a variety of different loss, blockage, and deviation models is reviewed, and the complexity of mathematical data processing and model development is presented. Examination of different modeling philosophies is given with critique of the consequences. Examples of data matching, modeling for design work, and modeling uncertainty are given. Suggestions for future improvements are offered.
(Download PDF)
"Optimization of Turbomachinery – Validation Against Experimental Results"
2009 – Current Trends in Design and Computation of Turbomachinery
The long-term objective of engineering design software, or indeed any modeling technique, is to improve the performance of the end product and to reduce the time and cost for the project. This is particularly true in the case of testing, which can substantially increase time and costs. Every analysis method, with the possible exception of Direct Numerical Simulation, requires empirically based models to close the equations and render the problem tractable. For this reason, and to confirm the soundness of the basic implementation, comprehensive validation is required to ensure accurate results.
(Download PDF)
"A Meanline Model for Impeller Flow Recirculation"
Presented at ASME Turbo Expo 2008: Power for Land, Sea and Air
June 9-13, 2008, Berlin, Germany
Flow recirculation at the impeller inlet and outlet is an important feature that affects impeller performance, especially the power consumption at a very low flow rate. Although the mechanisms for this flow phenomenon have been studied, a practical model is needed for meanline modeling of impeller off-design performance.
(Download PDF)
"Performance Prediction for High Pressure-Ratio Radial Inflow Turbines"
Presented at ASME Turbo Expo 2007: Power for Land, Sea and Air
May 14-17, 2007, Montreal, Canada
This paper describes the latest developments in a method for predicting the design and off-design performance of radial inflow turbines, using a one-dimensional analysis. As such, it is suitable for preliminary design purposes and also for turbine map generation as an aid to the modelling of systems including such turbines. Previous development work has resulted in methods of loss correlation allowing the power output and efficiency to be predicted with confidence. The focus of this paper is on extending the calculation method to high-pressure ratios, and the accurate prediction of flow capacity for unchoked and choked conditions.
(Download PDF)
"CFD-Based Throughflow Solver in a Turbomachinery Design System"
Presented at ASME Turbo Expo 2007: Power for Land, Sea and Air
May 14-17, 2007, Montreal, Canada
Throughflow analysis is a critical component for the multistage axial turbomachine design. The Euler throughflow approach has been developed over the last couple of decades, but has been less successful than its early peer, the streamline curvature approach. In this paper an Euler throughflow approach is described for engineering applications. It includes the steps needed to construct the stream surface, such as modifications for the incidence and deviation, and the throat area correction. The flow angle difference at the trailing edge and in the downstream nonbladed gap stations is resolved, and the numerical loss from solving the Euler equation is removed as well.
(Download PDF)
"A New Slip Factor Model for Axial and Radial Impellers"
Presented at ASME Turbo Expo 2007: Power for Land, Sea and Air
May 14-17, 2007, Montreal, Canada
This paper proposes a unified slip model for axial, radial, and mixed flow impellers. For many years, engineers designing axial and radial turbomachines have applied completely different deviation or slip factor models. For axial applications, the most commonly used deviation model has been Carter’s rule or its derivatives. For centrifugal impellers, Wiesner’s correlation has been the most popular choice. Is there a common thread linking these seemingly unrelated models? This question becomes particularly important when designing a mixed-flow impeller when one has to choose between axial or radial slip models.
(Download PDF)
"Vaneless Diffuser Advanced Model"
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.
(Download PDF 257 KB)
"Turbomachinery Modeling: Explicit and Implicit Knowledge Capturing"
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.
(Download PDF 304 KB)
"Multi-Variable, High Order, Performance Models"
PROVISIONAL DRAFT - Paper presented may be different than paper available here. 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.
(Download PDF 609 KB)
"Turbomachinery Performance Models"
PROVISIONAL DRAFT - Paper presented may be different than paper available here. 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.
(Download PDF 240 KB)
"Radial Turbines: An Integrated Design Approach"
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 meanline 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.
(Download PDF 356 KB)
"Optimization in Turbomachinery Data Reduction"
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.
(Download PDF 350 KB)
"An Evaluation of Neural Networks for Meanline Model Development"
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.
(Download PDF 502 KB)
"Optimization in Component Design and Redesign"
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.
(Download PDF 1.77 MB)
"Opportunities in University Collaboration for Turbomachinery Development: A Turbomachinery Perspective on Engineering Education"
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.
(Download PDF 292 KB)
"Application of a New Turbine Design System to Rocket Turbopumps"
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.
(Download PDF 1.21 MB)
"The Reduced Order Through-Flow Modeling of Axial Turbomachinery "
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.
(Download PDF 663 KB)
"Hydrodynamic Analysis of Two 3D Axial Flow Pumps"
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.
(Download PDF 1.12 MB)
"Multidisciplinary Optimization Applied to a Turbocharger Compressor Impeller"
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.
(Download PDF 1 MB)
"Application and Validation of CFD in a Turbomachinery Design System"
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.
(Download PDF 1.8 MB)
"Multidisciplinary Optimization of a LH2 Turbopump Design in an Agile Engineering Environment"
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.
(Download PDF 811 KB)
"Radial and Mixed-Flow Turbine Options for High Boost Turbochargers"
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.
(Download PDF 694 KB)
"Thermo-Mechanical Turbopump Design and Analysis Tools"
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.
(Download PDF 694 KB)
"Decisive Factors in Advanced Centrifugal Compressor Design and Development"
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.
(Download PDF 488 KB)
"Design Study of a Low-Cost LOX Turbopump"
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.
(Download PDF 138 KB)
"Sidestream Optimization Through The Use of Computational Fluid Dynamics and Model Testing"
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 users 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.
(Download PDF 789 KB)
"Correlation of Annular Diffuser Performance with Geometry, Swirl, and Blockage"
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.
(Download PDF 111 KB)
"Application of Design for Manufacture and Assembly Methodologies to Complex Aerospace Products"
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.
(Download PDF 473 KB)
"Characteristics of a Radial Inflow Turbine with Internal Component Measurements, Part 1: Data Review"
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.
(Download PDF 530 KB)
"The Validation of Rapid CFD Modeling for Turbomachinery"
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.
(Download PDF 627 KB)
"A Meanline Prediction Method for Radial Turbine Efficiency"
Presented at the 6th International Conference on Turbocharging and Air Management Systems, I Mech E, 3-5, November 1998. Paper No. C554-6.
A meanline loss system is described that is capable of predicting the efficiency of radial turbine stages at both on- and off-design conditions. The system is based on the well-known approach introduced by NASA in the 1960s, but includes many developments and refinements which arise from a physical understanding of the turbine rotor flow processes. The model has been tested against a database of thirty turbine tests covering a wide range of configurations and geometries.
(Download PDF)
