Organizational Unit:

Aerospace Systems Design Laboratory (ASDL)

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https://hdl.handle.net/1853/70744

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Organizational Unit

Daniel Guggenheim School of Aerospace Engineering

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https://finding-aids.library.gatech.edu/agents/corporate_entities/1135

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Publication Search Results

Now showing 1 - 10 of 34

Probabilistic Matching of Turbofan Engine Performance Models to Test Data

(Georgia Institute of Technology, 2005-06-06) Roth, Bryce Alexander ; Doel, David L. ; Cissell, Jeffrey J.

This paper describes the development of an improved method for reliable, repeatable, and accurate matching of engine performance models to test data. The centerpiece of this approach is a minimum variance estimator algorithm with a priori estimates which addresses both deterministic and probabilistic aspects of the problem. Specific probabilistic aspects include uncertainty in the measurements, prior expectations on model matching parameters, and noise in the power setting parameters. The algorithm is able to produce optimal results using any number of measurements and model matching parameters and can therefore take advantage of all measured data to produce the best possible match. This improves on current matching algorithms which require that the number of measured parameters be equal to the number of model matching parameters. This algorithm has been implemented in the Numerical Propulsion System Simulation (NPSS) and tested on a generic high-bypass turbofan model typical of those used in commercial service. The baseline engine model and simulated test data are described in detail. Several exercises are discussed to illustrate results available from this algorithm including the matching of a typical power calibration data set and matching of a typical production engine data set.
Implementation of Engine Loss Analysis Methods in the Numerical Propulsion System Simulation

(Geogia Institute of Technology, 2005-06-06) Roth, Bryce Alexander ; McClure, Erin Kathleen ; Danner, Travis W.

This paper describes the implementation and application of a new set of thermodynamic loss analysis tools in the Numerical Propulsion System Simulation. This analysis tool set is intended to enable fast, accurate estimation of losses in an engine cycle model with minimal effort on the part of the user. The basic thermodynamic concepts and analysis methods are first described. Next, the implementation of the necessary thermodynamic calculation functions is described. These functions are intended to be used in conjunction with a generalpurpose loss analysis element to facilitate estimation of all losses in an engine cycle model. The loss analysis element is described in detail and is subsequently used to analyze a mixed flow turbofan engine. Typical performance and loss results are presented. The resultant detailed loss information is not normally available when using standard cycle analysis methods. The information gained from this analysis is useful in that it yields insight into the underlying losses that contribute to the overall engine performance.
Lost Thrust Methodology for Gas Turbine Engine Performance Analysis

(Georgia Institute of Technology, 2005-06-06) Roth, Bryce Alexander ; de Luis, Jorge

This paper presents and evaluates a lost thrust method for analysis of thermodynamic performance in gas turbine engines. This method is based on the definition of a hypothetical ideal engine that is used as a point of comparison to evaluate performance of the real engine. Specifically, component loss is quantified in terms of decrements in thrust of the real engine relative to the ideal engine having the same design point cycle. These lost thrust decrements provide a basis for accurately evaluating the performance cost of component losses while simultaneously accounting for all component interactions. The analysis algorithm is formally developed in detail and is then demonstrated for a typical separate flow turbofan engine. Various scenarios are examined and the results of these exercises are used to draw conclusions regarding the strengths and weaknesses of this approach to gas turbine performance analysis.
A Work Transfer Perspective of Propulsion System Performance

(Georgia Institute of Technology, 2004-07) Roth, Bryce Alexander

This paper suggests an approach to analysis of propulsion system performance that focuses entirely on thermodynamic work potential (and loss thereof) as a universal basis for gauging engine performance. This work potential may take a variety of forms, including conventionally known exergy analysis. Emphasis is placed on understanding how work potential initially stored in the chemical bonds of the fuel is manifested as useable work potential in an engine, transferred through a collection of components organized as a propulsion system, and ultimately yields useful thrust work. A model for overall propulsion system efficiency is suggested to facilitate the analysis. Component work transfer functions are introduced as a tool for analyzing work transfer and are used in conjunction with standard methods of block diagram algebra. This analysis reveals the fundamental parameter groupings governing propulsion system thermodynamic performance and makes clear how work is transferred thorough various portions of the engine.
Work Transfer Analysis of Turbojet and Turbofan Engines

(Georgia Institute of Technology, 2004) Roth, Bryce Alexander

This paper explores the application of work transfer analysis to turbojet and turbofan engines. Emphasis is placed on understanding and applying the basic analysis method. The relationships between component performance and overall system work transfer are explored and demonstrated for ramjet, turbojet, and turbofan examples. The analysis results obtained via this method are quantified for a separate flow turbofan example. Finally, this paper suggests groupings of parameters of fundamental importance to turbofan engines based on the analysis results developed herein.
Assessment of Uncertainty in Aerospace Propulsion System Design and Simulation

(Georgia Institute of Technology, 2003-12) Mavris, Dimitri N. ; Roth, Bryce Alexander

The subject of uncertainty analysis in complex systems design is a broad and bourgeoning field of study. This paper focuses on only three very specific areas of current propulsion research wherein uncertainty plays a pivotal role in the problem formulation. The first is probabilistic approaches to matching engine cycle models to test data. Engine cycle models must have a high confidence of representing the actual engine performance accurately. These models must be matched in the presence of measurement, manufacturing, and other sources of uncertainty. Moreover, the optimal model match tends to change with time such that the problem is stochastic in nature. Current efforts are focusing on using Bayesian statistics to enable a comprehensive (stochastic) treatment of the problem. The second research area of interest is probabilistic analysis methods for estimation of part life in life-limited gas turbine engines. There are many sources of uncertainty in estimating part life, including material properties, material cleanliness/flaw size, part loads, and usage profile. Moreover, life limited parts are subject to accumulated damage over time, and the damage accumulation rate is a strong function of vehicle mission profile and usage. Current efforts are therefore aimed at linking detailed part analysis (finite element and materials models) with higher-level system and mission-level parameters to enable rapid and accurate analysis with the least possible effort. Finally, the role of uncertainty in engine materials selection and insertion is discussed. The materials development process for critical turbine engine parts is very lengthy and subject to considerable uncertainty with regards to the optimal balance of materials properties required for a given application. This is an area of research that will benefit from the development of materials selection methods designed to yield robust materials applicable to the greatest possible number of engines.
Estimation of Turbofan Engine Performance Model Accuracy and Confidence Bounds

(Georgia Institute of Technology, 2003-09) Roth, Bryce Alexander ; Mavris, Dimitri N. ; Doel, David L.

This paper explores the application of Inference and Bayesian Updating principles as a means to efficiently incorporate probabilistic data into the turbine engine status model matching process. This approach allows efficient estimation of nominal model match parameters from test data and also enables quantification of model accuracy and confidence bounds. The basic concepts are developed in detail and formulated into a status matching approach. This method is then applied to a simple surrogate matching problem using a cantilever beam matching exercise to illustrate the methods in a clear and easy-to-understand way. Typical results are presented and are directly analogous to status matching of a gas turbine engine cycle model.
The Role of Thermodynamic Work Potential in Aerospace Vehicle Design

(Georgia Institute of Technology, 2003) Roth, Bryce Alexander

Thermodynamic performance is a prime consideration in the design of vehicles. This is because all vehicles operate by transforming the stored work potential contained in fuel into useful work. This work output is then used to overcome various loss mechanisms in the engine, drivetrain, and vehicle systems. A significant part of vehicle engineering is finding means to minimize losses integrated through the design mission in order to minimize costs. This paper discusses how thermodynamic work potential can be used as a vehicle analysis tool to minimize losses and improve performance. The foundation of this method is the second law of thermodynamics. This approach provides a
A Method for Thermodynamic Work Potential Analysis of Aircraft Engines

(Georgia Institute of Technology, 2002-07) Roth, Bryce Alexander ; McDonald, Robert Alan ; Mavris, Dimitri N.

The objective of this paper is to provide a tool to facilitate the application of thermodynamic work potential methods to aircraft and engine analysis. This starts with a discussion of the theoretical background underlying these methods, which is then used to derive various equations useful for thermodynamic analysis of aircraft engines. The work potential analysis method is implemented in the form of a set of working charts and tables than can be used to graphically evaluate work potential stored in high-enthalpy gas. The range of validity for these charts is 300 to 36,000 oR, pressures between 0.01 and 100 atm, and fuel-air ratios from zero to stoichiometric. The derivations and charts assume mixtures of Jet-A and air as the working fluid. The thermodynamic properties presented in these charts were calculated based upon standard thermodynamic curve fits.
Performance Characterization of Turboshaft Engines Via Availability and Second Law Analysis

(Georgia Institute of Technology, 2002-06) Riggins, David W. ; Wilson, Christopher D. ; Roth, Bryce Alexander ; McDonald, Robert Alan

This paper develops and describes work potential analysis methods applicable to turboshaft engine flow-fields. These methods are based on the second-law of thermodynamics and enable a unified, comprehensive assessment of performance at the part, component, and engine levels. The focus herein is on using gas specific power as a work potential figure of merit in analyzing turboshaft engines. This is shown to be a useful tool for assessing local performance potential in a gas turbine flow-field. The fundamental relationships between heat, work, and irreversibility in turboshaft engines are developed and the relationship of flow irreversibility to engine performance losses is discussed. These theoretical ideas are then formulated in a method that enables characterization of performance losses in terms of engine spatial location and loss mechanism. This method is then demonstrated at the engine system level via cycle analysis, at the component level via quasi 1-D analysis, and at the part level via a stator row multi-dimensional CFD simulation analyzed in terms of irreversible entropy production.