摘要 :
The first part of the paper compared the midspan aerodynamics and the secondary flows for a family of three low-pressure turbine (LPT) airfoils at design conditions. However, since a typical engine spends much of its time operatin...
展开
The first part of the paper compared the midspan aerodynamics and the secondary flows for a family of three low-pressure turbine (LPT) airfoils at design conditions. However, since a typical engine spends much of its time operating at off-design conditions, good tolerance of LPT airfoils to off-design operation is desired. The sensitivity of the midspan flow to Reynolds number was examined for the three airfoils in a paper presented at the 2006 ASME-IGTI Turbo-Expo. The present paper examines the performance of the airfoils for three values of incidence: -5, 0, and +5 degrees relative to design. Both the profile and secondary losses are considered. Detailed loading distributions measured at midspan are used to explain the behaviour of the profile flow and the resulting change in losses as the incidence was varied. The secondary flow behaviour is determined as at the design incidence from detailed flowfield measurements made downstream of the trailing edge using a seven-hole pressure probe. The results show that in terms of profile losses the baseline airfoil (which has a Zweifel coefficient Z=1.08) and the front-loaded one with Z=l .37 have comparable losses over the range of incidences examined. However, the aft-loaded airfoil with Z = 1.37 had noticeably higher profile losses than the other two. On the other hand, the front-loaded one has higher secondary losses than its aft-loaded counterpart at all conditions examined. This obviously poses a dilemma for the designer in terms of the choice of loading distribution. It was also noted that the distribution of loading seems to affect the secondary losses more than the loading level (Zweifel coefficient). An interaction of the secondary flows with the suction side separation bubble might be responsible in part for this finding.
收起
摘要 :
A rotordynamic analysis of a large turbo-compressor that models both the casing and supports along with the rotor-bearing system was performed. A three-dimensional (3-D) finite element model of the casing captures the intricate de...
展开
A rotordynamic analysis of a large turbo-compressor that models both the casing and supports along with the rotor-bearing system was performed. A three-dimensional (3-D) finite element model of the casing captures the intricate details of the casing and support structure. Two approaches are presented, including development of transfer functions of the casing and foundation, as well as a fully coupled rotor-casing-foundation model. The effect of bearing support compliance is captured, as well as the influence of casing modes on the rotor response. The first approach generates frequency response functions (FRF's) from the finite element case model at the bearing support locations. A high-order polynomial in numerator-denominator transfer function format is generated from a curve-fit of the FRF. These transfer functions are then incorporated into the rotordynamics model. The second approach is a fully coupled rotor and casing model that is solved together. An unbalance response calculation is performed in both cases to predict the resulting rotor critical speeds and response of the casing modes. The effect of the compressor case and supports caused the second critical speed to drop to a value close to the operating speed and not compliant with API 617 7th edition requirements. A combination of rotor, journal bearing, casing, and support modifications resulted in a satisfactory and API compliant solution. The results of the fully coupled model validated the transfer function approach.
收起
摘要 :
The primary focus of this paper is convective heat transfer in axial flow turbines. Research activity involving heat transfer generally separates into two related areas: predictions and measurements. The problems associated with p...
展开
The primary focus of this paper is convective heat transfer in axial flow turbines. Research activity involving heat transfer generally separates into two related areas: predictions and measurements. The problems associated with predicting heat transfer are coupled with turbine aerodynamics because proper prediction of vane and blade surface-pressure distribution is essential for predicting the corresponding heat-transfer distribution. The experimental community has advanced to the point where time-averaged and time-resolved 3-D heat-transfer data for the vanes and blades are obtained routinely by those operating full-stage rotating turbines. However, there are relatively few CFD codes capable of generating 3-D predictions of the heat-transfer distribution, and where these codes have been applied the results suggest that additional work is required. This paper outlines the progression of work done by the heat transfer community over the last several decades as both the measurements and the predictions have improved to current levels. To properly frame the problem, the paper reviews the influence of turbine aerodynamics on heat transfer predictions. This includes a discussion of time-resolved surface-pressure measurements with predictions and the data involved in forcing function measurements. The ability of existing 2-D and 3-D Navier Stokes codes to predict the proper trends of the time-averaged and unsteady pressure field for full-stage rotating turbines is demonstrated. Most of the codes do a reasonably good job of predicting the surface-pressure data at vane and blade midspan, but not as well near the hub or the tip region for the blade. In addition, the ability of the codes to predict surface-pressure distribution is significantly better than the corresponding heat-transfer distributions. Heat-transfer codes are validated against measurements of one type or another. Sometimes the measurements are performed using full rotating rigs, and other times a much more simple geometry is used. In either case, it is important to review the measurement techniques currently used. Heat-transfer predictions for engine turbines are very difficult because the boundary conditions are not well known. The conditions at the exit of the combustor are generally not well known and a section of this paper discusses that problem. The majority of the discussion is devoted to external heat transfer with and without cooling, turbulence effects, and internal cooling. As the design community increases the thrust to weight ratio and the turbine inlet temperature, there remain many turbine-related heat transfer issues. Included are film cooling modeling, definition of combustor exit conditions, understanding of blade tip distress, definition of hot streak migration, component fatigue, loss mechanisms in the low turbine, and many others. Several suggestions are given herein for research and development areas for which there is potentially high payoff to the industry with relatively small risk.
收起
摘要 :
Many of the challenges that limited aero-engine operation in the 1950s, 60s, 70s and 80s were static in nature: hot components exceeding temperature margins, stresses in the high-speed rotating structure approaching safety limits,...
展开
Many of the challenges that limited aero-engine operation in the 1950s, 60s, 70s and 80s were static in nature: hot components exceeding temperature margins, stresses in the high-speed rotating structure approaching safety limits, and turbomachinery aerodynamic efficiencies missing performance goals. Modeling tools have greatly improved since and have helped enhance jet engine design, largely due to better computers and improved simulations of the fluid flow and supporting structure. The situation is thus different today, where important problems encountered past the design and development phases are dynamic in nature. These can jeopardize engine certification and lead to major delays and increased program cost. A real challenge is the characterization of damping and the related dynamic behavior of rotating and stationary components and assemblies, and of the fluid-structure interactions and coupling. The theme of this lecture is instability in the broadest sense. A number of problems of technological interest in aero-engines are discussed with focus on dynamical system modeling and identification of the underlying mechanisms. Future perspectives on outstanding seminal problems and grand challenges are also given.
收起
摘要 :
An experiment was conducted to investigate the effect that a planar surface located near a jet flow has on the noise radiated to the far-field. Two different configurations were tested: 1) a shielding configuration in which the su...
展开
An experiment was conducted to investigate the effect that a planar surface located near a jet flow has on the noise radiated to the far-field. Two different configurations were tested: 1) a shielding configuration in which the surface was located between the jet and the far-field microphones, and 2) a reflecting configuration in which the surface was mounted on the opposite side of the jet, and thus the jet noise was free to reflect off the surface toward the microphones. Both conventional far-field microphone and phased array noise source localization measurements were obtained. This paper discusses phased array results, while a companion paper discusses far-field results. The phased array data show that the axial distribution of noise sources in a jet can vary greatly depending on the jet operating condition and suggests that it would first be necessary to know or be able to predict this distribution in order to be able to predict the amount of noise reduction to expect from a given shielding configuration. The data obtained on both subsonic and supersonic jets show that the noise sources associated with a given frequency of noise tend to move downstream, and therefore, would become more difficult to shield, as jet Mach number increases. The noise source localization data obtained on cold, shock-containing jets suggests that the constructive interference of sound waves that produces noise at a given frequency within a broadband shock noise hump comes primarily from a small number of shocks, rather than from all the shocks at the same time. The reflecting configuration data illustrates that the law of reflection must be satisfied in order for jet noise to reflect off of a surface to an observer, and depending on the relative locations of the jet, the surface, and the observer, only some of the jet noise sources may satisfy this requirement.
收起
摘要 :
The U.S. Department of Energy (DOE) Office of Fossil Energy has established projects to develop highly efficient turbines for coal-based fuels in integrated gasification combined-cycle applications. These fuels include coal-derive...
展开
The U.S. Department of Energy (DOE) Office of Fossil Energy has established projects to develop highly efficient turbines for coal-based fuels in integrated gasification combined-cycle applications. These fuels include coal-derived synthesis gas and pure hydrogen. The projects, with both General Electric and Siemens, have specific performance goals they must strive to attain. In order to ascertain the actual performance improvements that must be realized in these projects to reach the project goals, existing turbine baseline performance must be established. This paper will present the work conducted to establish the baseline performance parameters, and the values of these parameters. Performance parameters and values reported in the open literature will be presented. Parameters that are not available in the literature are also reported and were obtained by using ASPEN PLUS (Aspen Technology, Inc.) and GT-PRO (Thermoflow, Inc.) simulation software. A survey was conducted to obtain available process conditions and parameters related to Simple-Cycle (SC) and Combined-Cycle (CC) gas turbine performance in integrated gasification combined-cycle (IGCC) applications that use coal as the primary fuel source. Information sources include commercial IGCC plants funded through the Clean Coal Technology (CCT) Demonstration Program, a proposed greenfield IGCC plant, NETL system studies, and other open literature sources. The report results can be employed to assist DOE in establishing a "Baseline IGCC Plant Performance Model" for comparisons with future improvements. The year 2010 IGCC performance goals include 45-50% HHV efficiency, $1,000 / kW total capital costs, and near-zero emissions. Contributions toward this goal are provided by DOE's Gasification and Advanced Turbines programs. Contributions from the Turbines program are targeted to provide 2-3 percentage points improvement in combined-cycle performance by 2010 for synthesis gas applications, and 3-5 percentage points (total) by 2015 for hydrogen fuels. The results are summarized in a series of tables that highlight the information identified that includes gas turbine type, turbine simple-cycle and combined-cycle efficiencies, turbine temperatures (e.g., firing temperature, exhaust temperature), pressure ratio, diluents, fuel composition, ASU integration, coal analysis, emissions, and the overall plant efficiency. The turbines and plants assessed to determine this baseline performance included the U.S.-based GE 7F frame turbines at the Wabash IGCC, Tampa IGCC, and Ashtabula IGCC (Nordic Energy - proposed 2002, Ashtabula, Ohio), as well as two European IGCC plants based on Siemens-Westinghouse V94.2 / V94.3 frame turbines located at the Buggenum IGCC (Netherlands) and Puertollano IGCC (Spain).
收起
摘要 :
The U.S. Department of Energy (DOE) Office of Fossil Energy has established projects to develop highly efficient turbines for coal-based fuels in integrated gasification combined-cycle applications. These fuels include coal-derive...
展开
The U.S. Department of Energy (DOE) Office of Fossil Energy has established projects to develop highly efficient turbines for coal-based fuels in integrated gasification combined-cycle applications. These fuels include coal-derived synthesis gas and pure hydrogen. The projects, with both General Electric and Siemens, have specific performance goals they must strive to attain. In order to ascertain the actual performance improvements that must be realized in these projects to reach the project goals, existing turbine baseline performance must be established. This paper will present the work conducted to establish the baseline performance parameters, and the values of these parameters. Performance parameters and values reported in the open literature will be presented. Parameters that are not available in the literature are also reported and were obtained by using ASPEN PLUS (Aspen Technology, Inc.) and GT-PRO (Thermoflow, Inc.) simulation software. A survey was conducted to obtain available process conditions and parameters related to Simple-Cycle (SC) and Combined-Cycle (CC) gas turbine performance in integrated gasification combined-cycle (IGCC) applications that use coal as the primary fuel source. Information sources include commercial IGCC plants funded through the Clean Coal Technology (CCT) Demonstration Program, a proposed greenfield IGCC plant, NETL system studies, and other open literature sources. The report results can be employed to assist DOE in establishing a "Baseline IGCC Plant Performance Model" for comparisons with future improvements. The year 2010 IGCC performance goals include 45-50% HHV efficiency, USD1,000/kW total capital costs, and near-zero emissions. Contributions toward this goal are provided by DOE's Gasification and Advanced Turbines programs. Contributions from the Turbines program are targeted to provide 2-3 percentage points improvement in combined-cycle performance by 2010 for synthesis gas applications, and 3-5 percentage points (total) by 2015 for hydrogen fuels. The results are summarized in a series of tables that highlight the information identified that includes gas turbine type, turbine simple-cycle and combined-cycle efficiencies, turbine temperatures (e.g., firing temperature, exhaust temperature), pressure ratio, diluents, fuel composition, ASU integration, coal analysis, emissions, and the overall plant efficiency. The turbines and plants assessed to determine this baseline performance included the U.S.-based GE 7F frame turbines at the Wabash IGCC, Tampa IGCC, and Ashtabula IGCC (Nordic Energy - proposed 2002, Ashtabula, Ohio), as well as two European IGCC plants based on Siemens-Westinghouse V94.2/V94.3 frame turbines located at the Buggenum IGCC (Netherlands) and Puertollano IGCC (Spain).
收起
摘要 :
Given the maturity of the gas turbine engine since its invention and also considering the limited and flattened level of resources expected to be allocated for NASA aeronautics research and development, we ask the question are NAS...
展开
Given the maturity of the gas turbine engine since its invention and also considering the limited and flattened level of resources expected to be allocated for NASA aeronautics research and development, we ask the question are NASA technology investments still needed to enable future turbine engine-based propulsion systems? If so, what is NASA's unique role to justify NASA's investment? To address this topic, we will first review the accomplishments and the impact that NASA Glenn Research Center has made on turbine engine technologies over the last 78 years. Specifically, this paper discusses NASA's role and contributions to turbine engine development, specific to both 1) NASA's role in conducting experiments to understand flow physics and provide relevant benchmark validation experiments for Computational Fluid Dynamics (CFD) code development, validation, and assessment; and 2) the impact of technologies resulting from NASA collaborations with industry, academia, and other government agencies. Note that the scope of the discussion is limited to the NASA technology contributions with which the author was intimately associated, and does not represent the entirety of the NASA contributions to turbine engine technology. The specific research, development, and demonstrations discussed herein were selected to both 1) provide a comprehensive review and reference list of the technology and its impact, and 2) identify NASA's unique role and highlight how NASA's involvement resulted in additional benefit to the gas turbine engine community. Secondly, we will discuss current NASA collaborations that are in progress and provide a status of the results. Finally, we discuss the challenges anticipated for future turbine engine-based propulsion systems for civil aviation and identify potential opportunities for collaboration where NASA involvement would be beneficial. Ultimately, the gas turbine engine community will decide if NASA involvement is needed to contribute to the development of the design and analysis tools, databases, and technology demonstration programs to meet these challenges for future turbine engine-based propulsion systems.
收起
摘要 :
The Numerical Propulsion System Simulation (NPSS) code was created through a joint United States industry and National Aeronautics and Space Administration (NASA) effort to develop a state-of-the-art aircraft engine cycle analysis...
展开
The Numerical Propulsion System Simulation (NPSS) code was created through a joint United States industry and National Aeronautics and Space Administration (NASA) effort to develop a state-of-the-art aircraft engine cycle analysis simulation tool. Written in the computer language C++, NPSS is an object-oriented framework allowing the gas turbine engine analyst considerable flexibility in cycle conceptual design and performance estimation. Furthermore, the tool was written with the assumption that most users would desire to easily add their own unique objects and calculations without the burden of modifying the source code. The purpose of this paper is twofold: first, to present an introduction to the discipline of thermodynamic cycle analysis to those who may have some basic knowledge in the individual areas of fluid flow, gas dynamics, thermodynamics, and turbomachinery theory but not necessarily how they are collectively used in engine cycle analysis. Second, this paper will show examples of performance modeling of gas turbine engine cycles specifically using Numerical Propulsion System Simulation concepts and model syntax. Current practices in industry and academia will also be discussed. While NPSS allows both steady-state and transient simulations and is written to facilitate higher orders of analysis fidelity, the pedagogical example will focus primarily on steady-state analysis of an aircraft mixed flow turbofan at the 0-D and 1-D level. Ultimately it is hoped that this paper will provide a starting point by which both the novice cycle analyst and the experienced engineer looking to transition to a superior tool can use NPSS to analyze any kind of practical gas turbine engine cycle in detail.
收起
摘要 :
The confluence of market demand for greatly improved compact power sources for portable electronics with the rapidly expanding capability of micromachining technology has made feasible the development of gas turbines in the millim...
展开
The confluence of market demand for greatly improved compact power sources for portable electronics with the rapidly expanding capability of micromachining technology has made feasible the development of gas turbines in the millimeter-size range. With airfoil spans measured in 100's of microns rather than meters, these "microengines" have about 1 millionth the air flow of large gas turbines and thus should produce about 1 millionth the power, 10-100 W. Based on semiconductor industry derived processing of materials such as silicon and silicon carbide to submicron accuracy, such devices are known as micro-electro-mechanical systems (MEMS). Current millimeter-scale designs use centrifugal turbomachinery with pressure ratios in the range of 2:1 to 4:1 and turbine inlet temperatures of 1200-1600 K. The projected performance of these engines are on a par with gas turbines of the 1940's. The thermodynamics of MEMS gas turbines are the same as those for large engines but the mechanics differ due to scaling considerations and manufacturing constraints. The principal challenge is to arrive at a design which meets the thermodynamic and component functional requirements while staying within the realm of realizable micromachining technology. This paper reviews the state-of-the-art of millimeter-size gas turbine engines, including system design and integration, manufacturing, materials, component design, accessories, applications, and economics. It discusses the underlying technical issues, reviews current design approaches, and discusses future development and applications.
收起
原文获取