A. Alexiou

Development of Gas Turbine Performance Models Using a Generic Simulation Tool

An approach for gas turbine engine modelling using a general purpose object-oriented simulation tool is described. A commercially available such tool that can be adapted to different fields, through the creation of reusable modelling component libraries representing parts or equipment of a physical system, is employed. Libraries are developed using an object-oriented language. The possibility for quick implementation of new models and rapid analysis of results, through the use of a graphical user interface is demonstrated. A turbofan model, developed for both steady state and transient performance simulation, is used to illustrate the advantages offered by this approach. Results are presented and compared to those produced by an industry-accepted model. The flexibility of incorporating particular features into a model is demonstrated by presenting the implementation of adaptive features and a study of engine frequency response.Copyright

Advanced Capabilities for Gas Turbine Engine Performance Simulations

This paper describes the integration of advanced methods such as component zooming and distributed computing, in an object-oriented simulation environment dedicated to gas turbine engine performance modelling. A 1-D compressor stage stacking method is used to demonstrate three approaches for integrating numerical zooming in an engine model. In the first approach a 1-D compressor model produces a compressor map that is then used in the engine model in place of the default one. In the second approach the results of the 1-D analysis are passed to the 0-D component through appropriate ‘zooming’ scalars. In the final approach the 1-D compressor component directly replaces the 0-D one in the engine model. Distributed computing is realized using Web Services technology. The implementation steps for a distributed scenario are presented. The standalone compressor stage stacking method, in the form of a shared library, is placed in a remote site and can be accessed over the internet through a Web Service Operation (server side). An engine simulation is set up containing a 1-D compressor component which acts as the client for the Web Service operation. Future development of the tool’s advanced capabilities is finally discussed.© 2007 ASME

Turbofan Engine Health Assessment From Flight Data

The paper presents the use of different approaches to engine health assessment using on-wing data obtained over a year from an engine of a commercial short-range aircraft. The on-wing measurements are analyzed with three different approaches, two of which employ two models of different quality. Initially, the measurements are used as the sole source of information and are post-processed utilizing a simple “model” (a table of corrected parameter values at different engine power levels) to obtain diagnostic information. Next, suitable engine models are built utilizing a semi-automated method which allows for quick and efficient creation of engine models adapted to specific data. Two engine models are created, one based on publicly available data and one adapted to engine specific on-wing “healthy” data. These models of different detail are used in a specific diagnostic process employing model-based diagnostic methods, namely the Probabilistic Neural Network (PNN) method and the Deterioration Tracking method. The results demonstrate the level of diagnostic information that can be obtained for this set of data from each approach (raw data, generic engine model or adapted to measurements engine model). A sub-system fault is correctly identified utilizing the diagnostic process combined with the engine specific model while the Deterioration Tracking method provides additional information about engine deterioration.Copyright

GAS TURBINE ENGINE PERFORMANCE MODEL APPLICATIONS USING AN OBJECT- ORIENTED SIMULATION TOOL

Engine performance models are used throughout the life cycle of an engine from conceptual design to testing, certification and maintenance. The objective of this paper is to demonstrate the use and advantages of an engine performance model, developed using an object-oriented simulation tool, for the following applications: • Building an engine model from existing engine components and running steady state and transient calculations. • Development and integration of a new cooled turbine component in the existing engine model. • Accessing the engine model from an external application. • Using an external legacy routine in the engine model.Copyright

Modelling Contra-Rotating Turbomachinery Components for Engine Performance Simulations: The Geared Turbofan With Contra-Rotating Core Case

This paper presents a method of modelling contra-rotating turbomachinery components for engine performance simulations. The first step is to generate the performance characteristics of such components. In this study, suitably modified one-dimensional mean line codes are used. The characteristics are then converted to three-dimensional tables (maps). Compared to conventional turbomachinery component maps, the speed ratio between the two shafts is included as an additional map parameter and the torque ratio as an additional table. Dedicated component models are then developed that use these maps to simulate design and off-design operation at component and engine level.Using this approach, a performance model of a geared turbofan with a Contra-Rotating Core (CRC) is created. This configuration was investigated in the context of the European program NEWAC (NEW Aero-engine core Concepts). The core consists of a seven-stage compressor and a two-stage turbine without inter-stage stators and with successive rotors running in opposite direction through the introduction of a rotating outer spool. Such a configuration results in reduced parts count, length, weight and cost of the entire HP system. Additionally, the core efficiency is improved due to reduced cooling air flow requirements.The model is then coupled to an aircraft performance model and a typical mission is carried out. The results are compared against those of a similar configuration employing a conventional core and identical design point performance. For the given aircraft-mission combination and assuming a 10% engine weight saving when using the CRC arrangement over the conventional one, a total fuel burn reduction of 1.1% is predicted.Copyright

Concentrated solar power components toolbox in an object oriented environment

Abstract A toolbox for modeling solar components for gas and steam turbine Solar Thermal Power Plants (STPPs) is presented. It has been created in order to supplement the PROOSIS modeling environment that covers the power production parts. Solar and power production parts are both represented at a similar level of fidelity. The toolbox contains components for simulating all the individual solar elements used in STPPs in order to materialize Brayton, Rankine and Combined Cycles. Functionalities for computing solar irradiation properties as well as working fluid thermodynamic properties are included. The use of the toolbox is demonstrated through simulation cases at component and plant level, while its features, capabilities and merits are discussed. The developed capabilities offer the possibility to perform plant design optimization, operational support through performance prediction at various operating modes as well as assessment of the effect of components malfunctions.

Assessing Alternative Fuels for Helicopter Operation

At present, nearly 100% of aviation fuel is derived from petroleum using conventional and well known refining technology. However, the fluctuations of the fuel price and the vulnerability of crude oil sources have increased the interest of the aviation industry in alternate energy sources. The motivation of this interest is actually twofold: firstly, alternative fuels will help to stabilize price fluctuations by relieving the worldwide demand for conventional fuel. Secondly, alternative fuels could provide environmental benefits including a substantial reduction of emitted CO2 over the fuel life cycle. Thus, the ideal alternative fuel will fulfill both requirements: relieve the demand for fuels derived from crude oil and significantly reduce CO2 emissions. In the present paper, the effects of various alternative fuels on the operation of a medium transport/utility helicopter are investigated using performance models of the helicopter and its associated turboshaft engine. These models are developed in an object-oriented simulation environment that allows a direct mechanical connection to be established between them in order to create an integrated model. Considering the case of a typical mission for the specific helicopter/engine combination, a comparative evaluation of conventional and alternative fuels is then carried out and performance results are presented at both engine and helicopter levels.

Short and Long Range Mission Analysis for a Geared Turbofan With Active Core Technologies

A novel engine concept, for reducing the environmental impact of gas turbines, is the Geared Turbofan with Active Core technologies (GTAC), investigated in the context of the European program NEWAC (New Aero Engine Core Concepts). Two performance models of this engine are created for short and long range aircraft applications and matched to manufacturer specifications. The engine performance data are used in a mission analysis module simulating typical aircraft applications. Compared to missions using Year 2000 in service engines, the results show a significant reduction in fuel consumption and noise levels. A significant reduction in NOx emissions requires the application of new technology combustor designs as developed e.g. in NEWAC.Copyright