bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Open Approach to Condition Monitoring, Diagnosis and Decision Support Systems
Authors: Shahroudi K. Eftekhari 
Published: December 2014

In increasing the availability and reducing the maintenance costs of gasturbines in critical applications, there has been an increasing trend towards Condition Monitoring, Diagnostic and Decision Support systems (CMD&D). The idea is to reduce the number of routine preventative maintenance procedures, in favor of techniques that continuously monitor the health and diagnose faults as they develop. Early isolation of the root cause of problems, allows the operators to better plan the corrective maintenance actions, taking into account the gasturbine and the other units with which it collaborates.
Clearly, this requires expertise in many fields such as Data Acquisition, Trending, Aerothermodynamic Performance, Vibration, Emissions, Fault Isolation, etc. In addition, it is increasingly becoming expensive to have experts available at all locations, so the solution obviously lies in (Semi-)autonomous systems. Their task would be to monitor the health and diagnose symptoms of machinery, perhaps in collaboration with junior experts locally and senior experts at a remote center.
This report outlines some of the results of a short but broad technical exploration in the questions of why none of the existing packages have achieved widespread acceptance, and how a turbine control manufacturer can play a significant role. A conceptual solution is presented which can meet the challenging functionality, data abstraction, automation and communication requirements by integration of expertise and modules from different groups. However, details on how to turn the concept into a product have been puposely ommitted in order to safeguard proprietory activity.
A Parametric Study of CHAT Cycle Performance: Thermodynamic and Design Features
Authors: Facchini B. , Ferrara G. , Masi G. 
Published: December 2014

The CHAT (Cascade Humid Air Turbine) cycle introduction has recently been proposed for a more simple and profitable application of the humid air turbine. The very interesting performance announced for this plant has been evaluated in this paper, particular attention is devoted to the multi-stage evaporation process and its thermodynamic limits.
A detailed thermodynamic analysis of the most important cycle parameters, like various pressure levels, fire temperatures and blade coolant bleeding can permit the evaluation of better plant performances. The results show a substantial agreement with other published data and they confirm the good efficiency and high specific power of the CHAT cycle.
Considering the proposed compressor and turbine for the CHAT plant an off design simulation of the plant is also realized to estimate the real behaviour of turbomachinery components.
Moreover this study is based on ESMS code already developed by the authors and the new components model (thermodynamic, design and off-design simulation) introduced for this work are presented.
The Development of a Computer Code for the Estimation of Combustor Exhaust Temperature Using Simple Gas Analysis Measurements
Authors: Bideau Richard J. 
Published: December 2014

Advances in gas turbine technology have led to levels of turbine inlet temperature that preclude the use of thermocouple and simple gas analysis techniques for gas temperature determination. Simple gas analysis schemes rely on the measurement of a very limited range of species in the gas sample, typically CO2, CO and hydrocarbons (UHC). A method of estimating the other important species is required. Simple gas analysis schemes that rely only on elemental mass balance equations to determine the concentration of species are inadequate where high temperature results in significant dissociation.
A method has been developed to enable temperature determination at levels that render simple schemes inaccurate. The procedure is based on the measurement of CO2, CO, UHC and oxides of nitrogen in the exhaust gas. Other species concentrations are calculated using an assumption of partial thermodynamic equilibrium. This allows the calculation of many important combustion parameters. The method has been implemented as a computer code, with an object orientated design approach using the C++ language.
The paper details the theory behind the approach and its implementation. The expected errors for practical applications are discussed and quantified. The method is illustrated by an exhaust temperature pattern factor investigation of an annular combustor. Temperatures determined by thermocouples are compared with those calculated from gas samples.
Improved Model for the Design and Analysis of Centrifugal Compressor Volutes
Authors: Van den Braembussche R. A. , Ayder E. , Hagelstein D. , Rautenberg M. , Keiper R. 
Published: December 2014

This paper describes a new model for the analysis of the flow in volutes of centrifugal compressors. It explicitly takes into account the vortical structure of the now that has been observed during detailed 3D flow measurements. It makes use of an impeller and diffuser response model to predict the non-uniformity of the volute inlet flow due, to the circumferential variation of the pressure at the volute inlet, and is therefore applicable also at off-design operation of the volute.
Predicted total pressure loss and static pressure rise coefficients at design and off-design operation have been compared with experimental data for different volute geometries but only one test case is presented here. Good agreement in terms of losses and pressure rise is observed at most operating points and confirms the validity of the impeller and diffuser response model.
Design of Tubular Humidifiers for Evaporative Gas Turbine Cycles
Authors: Dalili Farnosh , Westermark Mats 
Published: December 2014

In the evaporative gas turbine (EvGT) cycle, also referred to as the humid air turbine (HAT) cycle, the compressed air is humidified with water to increase the mass flow through the expander, resulting in high power output and high exhaust heat recovery potential. This paper presents a design methodology for tubular humidifiers, in which pressurized air is led inside of smooth metallic tubes and is brought into contact with a falling water film. The heat required for humidification is mainly taken from exhaust gas from the gas turbine on the shell side and also by recirculating water through the intercooler and the aftercooler.
The most important parameters for designing tubular humidifiers are: heat transfer coefficient on the flue gas side; and mass transfer coefficient for water vapor on the air side. Important design aspects include: proper wetting of the tubes; how to avoid flooding of the tubes; entrainment of water droplets into the air stream; and boiling in the water film.
All calculations in this paper are based on an evaporative gas turbine cycle applied for combined heat and power generation with a partial-flow humidification circuit, where a fraction of the compressed air is humidified while a major part is by-passed directly to the recuperator. It is concluded that the required heat exchanging surface can be reduced if humidification is carried out for only a fraction of the air (20–30 percent). Finned tubes are recommended to enhance the heat transfer per unit tube length.
Calculation of Convective Heat Transfer in Square-Sectioned Gas Turbine Blade Cooling Channels
Authors: Saidi Arash , Sundén Bengt 
Published: December 2014

Internal cooling channels are commonly used to reduce the thermal loads on the gas turbine blades to improve overall efficiency. In this study a numerical investigation has been carried out to provide a validated and consistent method to deal with the prediction of the fluid flow and the heat transfer of such channels with square cross sections. The rotation modified Navier-Stokes and energy equations together with a low-Re number version of the k-ε turbulence model are solved with appropriate boundary conditions. The solution procedure is based on a numerical method using a collocated grid, and the pressure-velocity coupling is handled by the SIMPLEC algorithm. The computations are performed with the assumption of fully developed periodic conditions.
The calculations are carried out for smooth ducts with and without rotation and effects of rotation on the heat transfer are described. Similar numerical calculations have carried out for channels with rib-roughened walls. The obtained results are compared with available experimental data and empirical correlations for the heat transfer rate and the friction factor. Some details of the flow and heat transfer fields are also presented.
Numerical Investigation of the Influence of Specific Vortex Generation on the Mixing Process of Film Cooling Jets
Authors: Vogel Dirk T. 
Published: December 2014

Vortices generated and designed in internal cooling systems of film cooled turbine blades have a significant influence on the aerodynamic mixing process of the coolant and the main flow. Of course the resulting distribution of the film cooling effectiveness is strongly influenced by the behaviour of the coolant mixing. The vortices are generated by a special design of the cooling channel and film cooling holes and by the comparable flow phenomena coming along with the problem of jets in crossflow.
The multi-block Navier-Stokes solver TRACES with special features for the simulation of complex and turbulent mixing phenomena is applied to solve the flow field and the heat fluxes and temperature distribution in the turbine blade structure simultaneously. The code is validated for the simulation of film cooling and heat transfer and was also compared to other codes taking part in the AGARD Working group 26 (Dunham, 1996 [4]) working on the test cases “NASA-Rotor-37” and DLR-Turbine guide vane “VT1B”.
As a result of extensive parameter studies (Vogel, 1996 [18]) a vortex mixing model will be established which describes the existing vortices and their effect on the film cooling mixing process in detail. It was found that vortex generation inside the internal cooling channel with an opposite direction of rotation compared with the main kidney shaped jet vortex system can reduce the amount of coolant air significantly without reducing the film cooling effectiveness. All numerical investigations presented in this paper were carried out using a model geometry. No experimental results were available for this geometry. The validation of the code concerning film cooling mixing was presented in [15], [16], [17] and [18] (Vogel, 1994–1996). The geometries applied in those validations were quite similar to those used in this paper. Nevertheless for credibility some comparisons between experimental and numerical data are presented.
Modified Humid Air Turbine Cycle for Biomass Gasification
Authors: Cavani Adrin 
Published: December 2014

Performance and design data are presented for energy conversion of biomass in modified HAT cycles in a combined heat and power plant. The computations are performed by the heat balance software GateCycle and based on a gas turbine LM 2500 from General Electric. The processing of biomass includes drying of wet biomass fuel, gasification at atmospheric pressure, gas cooling and wet gas cleaning of the product gas and gas compression to pressure requirement of the gas turbine combustion system.
A further problem in biomass fuelled power systems and humidified gas turbine (HAT cycle) is to accomplish stable combustion in a gas turbine combustor with humidified air along with product gas having low heating value. To avoid the problem, the air humidification is performed only on a fraction of the compressed air stream, which makes it possible to use dry air (unhumidified air) for the combustion in the primary zone and humidified air for diluting and cooling. It is shown that part-airflow humidification gives similar or slightly improved performance (specific power and cycle efficiency) and also reduces the need of area for heat exchanging and recuperating.
Applying the Relationship Between the Amount of CO2 and O2 in Flue Gases to Reduce the NOx Emission Measurement Uncertainty
Authors: van Oost M. L. E. 
Published: December 2014

A method has been found to reduce the high measurement uncertainty of NOx emissions of gas turbines.
Calculation of the measurement uncertainty of NOx emission measurements shows that the high uncertainty is not only due to the uncertainty of the NOx emission measurement itself but is also due to the correction to 15 % O2 in the flue gases.
A second, independent method to determine the percentage oxygen in the flue gases is introduced in addition to the direct sampling method. This second method provides additional information resulting in a significant reduction of the measurement uncertainty.
The solution found has the advantage that the additionally required measurement equipment is kept to a minimum.
Experience with the new method in field tests are excellent.
A Prediction Model for Separated-Flow Transition
Authors: Hatman Anca , Wang Ting 
Published: December 2014

The present study formulates an improved approach for analyzing separated-flow transition that differentiates between the transition process in boundary layers which are laminar at separation and those which are already transitional at separation.
The paper introduces new parameters that are necessary in classifying separated-flow transition modes and in accounting for the concomitant evolution of transition in separated shear layer and the average effect of periodic separation bubble build-up and vortex shedding. At least three separated-flow transition modes are positively distinguished: (a) transitional separation, with the transition starting upstream of the separation point and developing mostly as natural transition, (b) laminar separation - short bubble mode, with the onset of transition induced downstream of the separation point by inflexional instability and with a quick transition completion, and (c) laminar separation - long bubble mode, with the onset of transition also induced downstream of the separation point by inflexional instability, and with the transition completion delayed. Passing from one mode to another takes place continuously through a succession of intermediate stages.
The location of maximum bubble elevation has been proved to be the controlling parameter for the separated flow behavior. It was found that, downstream of the separation point, the experimental data expressed in terms of distance Reynolds number Rex can be correlated better than momentum or displacement thickness Reynolds number data. For each mode of separated-flow transition, the onset of transition, the transition length, and separated flow general characteristic are determined. This prediction model is developed mainly on low free-stream turbulence flat plate data and limited airfoil data. Extension to airfoils and high turbulence environment requires additional study.
External Heat Transfer Predictions in a Highly-Loaded Transonic Linear Turbine Guide Vane Cascade Using an Upwind Biased Navier-Stokes Solver
Authors: Gehrer Arno , Jericha Herbert 
Published: December 2014

External heat transfer predictions are performed for two-dimensional turbine blade cascades. The Reynolds-averaged Navier-Stokes equations with algebraic (Arnone and Pacciani, 1996), one-equation (Spalart and Allmaras, 1994) and two-equation (low-Re k-ε, Biswas and Fukuyama, 1994) turbulence closures are solved with a fully-implicit time-marching finite volume method.
Comparisons with measurements (Arts et al., 1990, 1994) for a highly-loaded transonic turbine nozzle guide vane cascade show good agreement in some cases, but also reveal problems with transition prediction and turbulence modeling.
Special attention has been focused on the low-Re k-ε model concerning the influence of the inlet boundary condition for the ε-equation and problems in the stagnation point region.
Sub-Scale Demonstration of the Active Feedback Control of Gas-Turbine Combustion Instabilities
Authors: Sattinger Stanley S. , Neumeier Yedidia , Nabi Aharon , Zinn Ben T. , Amos David J. , Darling Douglas D. 
Published: December 2014

Described are sub-scale tests that successfully demonstrate active feedback control as a means of suppressing damaging combustion oscillations in natural-gas-fueled, lean-premix combustors. The control approach is to damp the oscillations by suitably modulating an auxiliary flow of fuel injected near the flame. The control system incorporates state observer software that can ascertain the frequency, amplitude, and phase of the dominant modes of combustion oscillation, and a sub-scale fuel flow modulator that responds to frequencies well above 1 kHz.
The demonstration was conducted on a test combustor that could sustain acoustically coupled combustion instabilities at preheat and pressurization conditions approaching those of gas-turbine engine operation. With the control system inactive, two separate instabilities occurred with combined amplitudes of pressure oscillations exceeding 70 kPa (10 psi). The active control system produced four-fold overall reduction in these amplitudes. With the exception of an explainable control response limitation at one frequency, this reduction represented a major milestone in the implementation of active control.
Combustion System Damping Augmentation With Helmholtz Resonators
Authors: Gysling D. L. , Copeland G. S. , McCormick D. C. , Proscia W. M. 
Published: December 2014

This paper describes an analytical and experimental investigation to enhance combustion system operability using side branch resonators. First, a simplified model of the combustion system dynamics is developed in which the large amplitude pressure oscillations encountered at the operability limit are viewed as limit cycle oscillations of an initially linear instability. Under this assumption, increasing the damping of the small amplitude combustion system dynamics will increase combustor operability. The model is then modified to include side branch resonators. The parameters describing the side branch resonators and their coupling to the combustion system are identified, and their influence on system stability is examined. The parameters of the side branch resonator are optimized to maximize damping augmentation and frequency robustness.
Secondly, the model parameters for the combustor and side branch resonator dynamics are identified from experimental data. The analytical model predicts the observed trends in combustor operability as a function of the resonator parameters and is shown to be a useful guide in developing resonators to improve the operability of combustion systems.
Near Term Gas Turbine Program to Enable the Use of “Renewable” Fuels
Authors: Moritz Robert R. 
Published: December 2014

To be suitable for gas turbine use, renewable energy resources are typically processed to produce a cleaned gaseous fuel which tends to be of low energy density relative to natural gas. Depending on the process and source, the derived fuel gas may also contain a large fraction of Hydrogen. Such gases may require enrichment to permit stable combustion and also carry some hazard of flashback due to the Hydrogen content. Previous experience also suggests that even small traces of ash which could be carried through the gas cleaning have the potential to cause airfoil fouling.
Allison Engine Company produces engines for electric power generation in the range up to 7 MW and expects to offer derivatives up to 12 MW by the year 2000. Two series of engines are involved, offering different virtues and challenges in renewable fuels use. It is planned to extend the range of renewable fuels utilized by all these engines by carrying out a rig and engine demonstration program. A major goal is to operate a gas turbine using the product gas from a high quality biomass gasifier.
Preliminary Assessment of Advanced Gas Turbines for CVX
Authors: Bannister Ronald L. , Horazak Dennis A. 
Published: December 2014

To support the propulsion and electrical requirements of an all-electric CVX, the use of heavy-duty power generation gas turbines could be considered as a viable alternative to conventional steam propulsion. A 300 MWe total plant baseload capacity is needed for an all-electric ship requiring 200 MWe for propulsion and a peak electric catapult power requirement of 200 MWe.
Applications of advanced marine gas turbines to provide electric power to an all-electric CVX have a major advantage in that the gas turbines do not have to be located in the same area as the electric propulsion motors. The possibility of locating the turbine-generators topside to minimize the ship impacts associated with long runs of large intake and exhaust ducts was briefly studied and is discussed herein.
An Exergy Analysis of Novel Power Generation Systems
Authors: Neto Alcides Codeceira , Pilidis Pericles 
Published: December 2014

The present paper describes the application of the exergy method to several power cycles of current interest in the Brazilian power scene. The ability of the exergy method to highlight component irreversibilities is of particular interest in this investigation.
In this paper the exergy analysis for a simple gas turbine cycle, a combined gas/steam cycle, a combined gas/steam/freon cycle and a chemically recuperated gas turbine have been performed.
As a yardstick for comparison a standard gas turbine engine with and without a steam bottoming cycle has been employed. The fuel considered is natural gas. The analysis of this system has been carried out using the exergy method.
For the simple gas turbine cycle a biomass fuel has been employed as an alternative. The attraction of this fuel is its low impact on the environment and its plentiful supply in many regions in Brazil.
Improved Approach to an Endwall Heat Transfer Analysis: A Linear Guide Vane and a Curved Duct
Authors: Khalatov A. 
Published: December 2014

This paper consists of two sections. The first section of the paper illustrates successful application of the improved approach developed by author to the endwall heat transfer data analysis in a low speed linear guide vane and in a curved duct. Effects of a three dimensional turbulent flow, a horseshoe vortex, a passage vortex, as well as an entry boundary layer thickness have been considered in both passages and as a result the common experimental correlation on a local heat transfer have been derived for the H/t = 1.0 ratio. All affected factors are presented as a superposition of the linear correction functions in the basic experimental correlation for a flat plate heat transfer.
In the second section the common correlation is used as the reference correlation to establish effect of the span-to-pitch ratio on the endwall heat transfer in both passages. It was found that variation in the H/t ratio affects slightly the freestream velocity; the most important result which came from the heat transfer study is that in contrast to a curved duct a heat transfer rate in a blade passage is reduced while the H/t ratio decreases.
Comparison of the experimental data obtained by the author with results of the two-dimensional heat transfer prediction confirms that it is very important to take a three-dimensional heat transfer nature into account in design of the endwall convective cooling system. It has been demonstrated that distinction between the results of two- and three dimensional approach to the endwall heat transfer can achieve up to 70% at the passage’s inlet area.