I. Roumeliotis

Evaluation of Interstage Water Injection Effect on Compressor and Engine Performance

The present paper examines the effect of water injection at the compressor inlet or between stages, on its operation. A wet compression model coupled with an engine performance model is used. The wet compression model produces the compressor performance map when water is present and consists of a one-dimensional stage stacking model, coupled with a droplet evaporation model. The effect of water injection on overall performance and individual stage operation is examined. The map-generation procedure is embedded in an engine performance model and a study of water injection effect on overall engine performance is undertaken. The possibility to evaluate the effect on various parameters such as power, thermal efficiency, surge margin, as well as the progression of droplets through the stages is demonstrated. The results indicate that water injection causes significant stage rematching, leading the compressor toward stall and that the performance enhancement is greater as the injection point moves towards compressor inlet.

Water Injection Effects on Compressor Stage Operation

In the present paper, experimental work concerning the effect of water injection on a compressor stage is presented. The effect on compressor stage performance and stability is examined for water injection up to 2%. The behavior of the airflow in the blade rows is examined through aerodynamic measurements. The results indicate that although the water injection appears to not have any significant effect on the flow pattern and to stage pressure rise and stall margin, there is a measurable effect on compression efficiency, which seems to result mainly from losses of a mechanical nature and water acceleration. The efficiency degradation is proportional to the water ratio entering the engine.

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

Performance Analysis of Twin-Spool Water Injected Gas Turbines Using Adaptive Modeling

The development of an adaptive performance model for multi-spool gas turbines, equipped with the possibility of water injection is described. The model covers water injection at engine inlet, between the compressors and at the compressor exit. The selection of modification factors and the procedure for adapting component characteristics to overall performance data is discussed. A case of adaptation to overall performances is presented. The use of the model for studying overall engine and components performance is demonstrated. It is shown how operation with water injection modifies component operation, a fact that allows the identification of a wider range of the performance characteristics, in comparison to dry operation. This fact may also increase the diagnostic ability of techniques employing adaptive models. The sensitivity of diagnostic procedures to the different modes of operation of a gas turbine of the type described in the paper is also discussed.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

Modelling and Assessment of Compressor Faults on Marine Gas Turbines

Any prime mover exhibits the effects of wear and tear over time, especially when operating in a hostile environment. Marine gas turbines operation in the hostile marine environment results in the degradation of their performance characteristics. A method for predicting the effects of common compressor degradation mechanisms on the engine operation and performance by exploiting the “zooming” feature of current performance modelling techniques is presented. Specifically a 0D engine performance model is coupled with a higher fidelity compressor model which is based on the “stage stacking” method. In this way the compressor faults can be simulated in a physical meaningful way and the overall engine performance and off design operation of a faulty engine can be predicted. The method is applied to the case of a twin shaft engine, a configuration that is commonly used for marine propulsion.In the case of marine propulsion the operating profile includes a large portion of off-design operation, thus in order to assess the engine’s faults effects, the engine operation should be examined with respect to the marine vessel’s operation. For this reason, the engine performance model is coupled to a marine vessel’s mission model that evaluates the prime mover’s operating conditions. In this way the effect of a faulty engine on vessels’ mission parameters like overall fuel consumption, maximum speed, pollutant emissions and mission duration can be quantified.Copyright