bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Leakage Modular Regenerators for Gas-Turbine Engines
Authors: Kluka James Anthony , Wilson David Gordon
Published: December 2014

One of the significant problems plaguing regenerator designs is seal leakage resulting in a reduction of thermal efficiency. This paper describes the preliminary design and analysis of a new regenerative heat-exchanger concept, called a modular regenerator, that promises to provide improved seal-leakage performance. The modular regenerator concept consists of a ceramic-honeycomb matrix discretized into rectangular blocks, called modules. Separating the matrix into modules substantially reduces the transverse sealing lengths and substantially increases the longitudinal sealing lengths as compared with typical rotary designs. Potential applications can range from small gas-turbine engines for automotive applications to large stationary gas turbines for industrial power generation. Descriptions of two types of modular regenerators are presented including sealing concepts. Results of seal leakage analysis for typical modular regenerators sized for a small gas-turbine engine (120 kW) predict leakage rates under one percent for most seal-clearance heights.
Rotordynamic Modeling of an Actively Controlled Magnetic Bearing Gas Turbine Engine
Authors: Antkowiak B. M. , Nelson F. C.
Published: December 2014

This paper summarizes the development of a finite element rotordynamic solution used in a closed loop simulation for a magnetic bearing rotor system in a gas turbine engine. A magnetic bearing controlled rotor is analyzed, and the state dynamics matrix [A], the shaft control influence matrix [B], and the sensor matrix [C] are constructed. Bode plots of the state-space transfer function are also constructed and compared to the results of the rotor dynamic model.
Development of a Hydrogen-Fueled Combustion Turbine Cycle for Power Generation
Authors: Bannister Ronald L. , Newby Richard A. , Yang Wen-Ching
Published: December 2014

Consideration of a hydrogen based economy is attractive because it allows energy to be transported and stored at high densities and then transformed into useful work in pollution-free turbine or fuel cell conversion systems. Through its New Energy and Industrial Technology Development Organization (NEDO) the Japanese government is sponsoring the World Energy Network (WE-NET) Program. The program is a 28-year global effort to define and implement technologies needed for a hydrogen-based energy system. A critical part of this effort is the development of a hydrogen-fueled combustion turbine system to efficiently convert the chemical energy stored in hydrogen to electricity when the hydrogen is combusted with pure oxygen. The full-scale demonstration will be a greenfield power plant located sea-side. Hydrogen will be delivered to the site as a cryogenic liquid, and its cryogenic energy will be used to power an air liquefaction unit to produce pure oxygen.

To meet the NEDO plant thermal cycle requirement of a minimum of 70.9%, low heating value (LHV), a variety of possible cycle configurations and working fluids have been investigated. This paper reports on the selection of the best cycle (a Rankine cycle), and the two levels of technology needed to support a near-term plant and a long-term plant. The combustion of pure hydrogen with pure hydrogen with pure oxygen results only in steam, thereby allowing for a direct-fired Rankine steam cycle. A near-term plant would require only moderate development to support the design of an advanced high pressure steam turbine and an advanced intermediate pressure steam turbine.
Flux Density and Air Gap Effects on Rotor Power Loss Measurements in Planar Radial Magnetic Bearings
Authors: Allaire P. E. , Kasarda M. E. F. , Maslen E. H. , Gillies G. T. , Fujita L. K.
Published: December 2014

The rotor power losses in magnetic bearings are due to eddy currents, hysteresis, and windage. The influence of air gap magnetic flux density and air gap thickness is not well understood at this time. This paper presents measured results in two magnetic bearing radial configurations with a laminated rotor. The rotor power losses were evaluated by measuring the rundown speed of the rotor, in air, after the rotor was spun up to speeds of approximately 30,000 rpm in atmospheric air. The kinetic energy of the rotor is converted to heat by magnetic and air drag power loss mechanisms during the run down. A method of separating the hysteresis, eddy current and windage losses is presented. Eddy current effects were found to be the most important loss mechanism in the data analysis. Hysteresis and windage effects did not change much from one configuration to the other. The measured rotor power loss increased significantly as the magnetic flux density increased and also increased significantly as the air gap thickness decreased.
Generic 1D Dynamic Modeling of a Gas Generator Engine
Authors: Solomon A.
Published: December 2014

A physics based one-dimensional generic non linear dynamic model for a gas generator engine which is expected to enable future model based system oriented activities such as system control design, engine dynamic analysts, variable geometry optimization, air bleed extraction optimization, active surge and/or rotating stall avoidance control is presented. The model can be easily partitioned to obtain a one-dimensional compressor dynamic model which can simulate onset and development of surge and demonstrate existence of rotating stall. The notion of surge domain is introduced and it is shown how the dynamic model can quantitatively predict it. Other model predictions such as surge frequency and air bleed extractions are compared with experimental results.
A Magnetic Bearing Suspension System for High Temperature Gas Turbine Applications: Control System Design
Authors: Scholten James R.
Published: December 2014

A practical magnetic-bearing control system has been designed based upon modeling and simulation of the dynamics of a jet engine turbine shaft and bearing system. Simulations include models for flexible rotor dynamics, magnetic actuators, auxiliary touchdown bearings, ordinary and extraordinary external loads, and disturbances from rotor imbalance, stator vibration, and noise. The shaft model includes a motor-generator which acts as an uncontrolled negative stiffness.

The control system is decentralized, running independently for each of the five physical axes of control (1 axial, 4 radial). The fundamental algorithm is classical PID: proportional for broadband stiffness, integrator (with anti-windup) for high load-carrying capacity, and derivative to dampen disturbances. Additional phase lead is provided via a first-order pole-zero pair. The vibration due to rotor imbalance is eliminated by an autobalancing algorithm. Compensation for magnetic actuator non-linearity and varying rotor-stator gap is provided by feedback of sensed magnetic flux, using sensor coils built into the actuator. The control design can be readily implemented using a commercial Digital Signal Processing system. The magnetic bearing actuators will be driven with commercial power amplifiers via customized front-end electronics.

Based upon simulations, the design goal has been achieved of keeping the shaft within two mils of its desired location at the magnetic bearings, under all normal loads. Under extreme external loads, the capacity of the magnetic bearings will be exceeded and touchdown will occur upon backup mechanical bearings. Simulation shows that the control design handles this critical event, which determines the force slew rate required from the actuators.
Real-Time Health Monitoring and Diagnostics for Gas Turbine Engines
Authors: Roemer Michael J. , Atkinson Ben
Published: December 2014

Integrated life, vibration and performance monitoring/diagnostics capable of detecting and classifying developing engine faults is critical to reducing engine operating and maintenance costs while optimizing the life of “hot section” engine components (Troudet and Merrill, 1990). Advanced fault pattern recognition and classification techniques utilizing complex finite-element and empirical models of structural and performance related engine areas can now be accessed in a real-time monitoring environment (Dietz et al., 1989). Integration and implementation of these proven technologies presents a great opportunity to significantly enhance current engine health diagnostic capabilities and safely extend engine component life (Ali and Crawford, 1988).
Experimental Results of an Active Tip Clearance Control System for a Centrifugal Compressor
Authors: Mattern Duane , Jaw Link , Henry Mark , Fagan Bob
Published: December 2014

Increases in compressor efficiency and pressure ratio can be achieved by controlling the blade tip-to-shroud clearance. The design and test results of a fail-safe active tip clearance control system for a centrifugal compressor are presented. An electromagnetic actuator is used to pull the compressor impeller axially to reduce the tip clearance. The actuator acts against a preloaded Belleville spring. The controlled variable is an averaged, tip-to-shroud clearance which is measured with a capacitance displacement sensor and averaging electronics. A scheduled digital PI control law was used to account for the nonlinear effects of the electromagnet with electrical current and gap size. Closed-loop tip clearance control is demonstrated over the clearance range from 0.003 inches (0.127 mm) to 0.012 inches (0.305 mm). A simplified model of the system is presented along with open and closed-loop dynamic test results. Changes in the compressor performance due to tip clearance control are also presented.
Fault Mode Analysis Based on Compositional Modeling
Authors: Winston Howard , Tulpule Sharayu
Published: December 2014

Fault modes are difficult to model because they are often caused by or result in highly-nonlinear or discontinuous changes in an engineered system. These changes will typically invalidate some of the assumptions and simplifications that justify the simulation’s equation model. Thus, a framework for failure simulation should support the dynamic modification of equation models as required by changes in simulated physical conditions.

To address this problem, a framework for simulating failure modes in gas turbine engines has been implemented based on prior work on compositional modeling. We believe this design methodology and simulation architecture can enable scaleable and robust simulations of the precursors, manifestations, and consequences of failure modes in complex engineered devices.

An object-oriented modeling language was implemented to represent devices in terms of primitive and recursively defined compound components. Primitive components can encapsulate equations that always apply to their descriptions. The modeling language also includes objects that represent physical processes (i.e., composeable model fragments) that encapsulate equations that apply when the fragments’ applicability and activation conditions are satisfied. Model fragments may also contain terms that can contribute to the value of component parameters when those fragments are activated.

To interleave model building and simulation, equation models are implemented as constraint networks. This precludes the need to determine explicit solution orders for sets of equations and facilitates the incremental modification of equation models. As a failure scenario unfolds, the simulation can be interrupted, a new set of model fragments can be composed into the constraint network, and the simulation continued. This failure simulation framework is illustrated with a simple multi-stage gas turbine failure scenario.
Characteristics of Tip-Clearance Flows of a Compressor Cascade and a Propulsion Pump
Authors: Lee Y. T. , Laurita M. J. , Feng J. , Merkle C. L.
Published: December 2014

Tip-leakage flows for a linear compressor cascade and a one-stage shrouded pump rotor are discussed in this paper. A numerical method solving the Reynolds averaged Navier Stokes equations is used to explore various detail features of the tip-leakage flows. Calculation results for the cascade provide an assessment for predicting flow past a non-rotating blade passage with zero and 2% chord clearances. On the other hand, the pump rotor configuration provides a swirling passage flow with the complication of a trailing-edge separation vortex mixed with the tip-clearance and passage vortices and produces a very complex three-dimensional flow in the rotor wake. The physical aspects of the tip-clearance flows are discussed including suction-side reloading and pressure-side unloading due to a tip clearance and formation and transportation of the tip-leakage vortex. Detailed velocity comparisons in the blade passage and the tip gap region are shown to indicate the difficulty of predicting tip-leakage flow. The pressure at the core of the tip vortex is also examined to evaluate the strength of the tip-leakage vortex. Some computational guidelines for design usage are provided for these tip-leakage flow calculations.
Breakdown of Tip Leakage Vortices in Compressors at Flow Conditions Close to Stall
Authors: Schlechtriem Stefan , Lötzerich Michael
Published: December 2014

The breakdown of tip leakage vortices at operating points close to the stability limit of transonic compressor rotors has been detected. The aerodynamic phenomenon is considered to have a major impact on stall inception. Computations have been carried out and a detailed visualization of the phenomenon is given. In addition the connection of vortex breakdown to rotating instabilities and stall is discussed. Furthermore the tip flow field of the axial rotor is compared to the results for a centrifugal and a mixed flow compressor operating at similar tip speeds.
Use of Thermochemical Recuperation in Combustion Turbine Power Systems
Authors: Newby Richard A. , Yang Wen-Ching , Bannister Ronald L.
Published: December 2014

The performance and practicality of heavy duty combustion turbine power systems incorporating thermochemical recuperation (TCR) of natural gas has been estimated to assess the potential merits of this technology. Process models of TCR combustion turbine power systems based on the Westinghouse 501F combustion turbine were developed to conduct the performance evaluation. Two TCR schemes were assessed — Steam-TCR and Flue Gas-TCR. Compared to conventional combustion turbine power cycles, the TCR power cycles show the potential for significant plant heat rate improvements, but their practicality is an issue. Significant development remains to verify and commercialize TCR for combustion turbine power systems.
Anti-Kidney Pair of Vortices in Shaped Holes and Their Influence on Film Cooling Effectiveness
Authors: Haven B. A. , Yamagata D. K. , Kurosaka M. , Yamawaki S. , Maya T.
Published: December 2014

The difference in film cooling effectiveness of three shaped holes is hereby explained by their vortical structures. Highlighted, in particular, are the competing effects of two pairs of vortices present in jets: the so-called kidney-shaped pair of vortices and a newly found anti-kidney pair.

Three shaped holes investigated were referred to as TP2, TP3, and TP4. Except for the difference of how the hole area is increased, they are essentially the same. At the higher blowing ratio, the film cooling effectiveness of TP4 was found to be far superior to those of either TP2 and TP3.

By flow visualization in water, the cause of these differences was investigated and found to be explainable on the basis of different vortical structures. In particular, for TP4 with a better film cooling effectiveness, the kidney- and anti-kidney pairs were found to cancel each other, leading to the improved jet attachment.
AGTSR: A Unique Gas Turbine Consortium
Authors: Fant Daniel B. , Golan Lawrence P.
Published: December 2014

This paper discusses the nationwide impact of the Advanced Gas Turbine Systems Research (AGTSR) consortium which supports the advanced development of land-based gas turbines for future power generation systems. In particular, the paper emphasizes the educational and research missions of AGTSR. The educational program consists of undergraduate fellowships and graduate-level industrial internships at sponsoring company sites. To date, AGTSR has placed twenty interns at some of the major gas turbine facilities throughout the United States. This experience motivates engineering students to pursue gas turbine careers and allows them to gain valuable hands-on experience in an industrial setting. The research arm of AGTSR nurtures collaborative R&D with universities and industry. All the research issues identified by AGTSR are defined by the Industry Review Board (IRB) which is made up of representatives from seven gas turbine/component manufacturers. AGTSR currently supports over thirty research projects covering research needs in the area of combustion, heat transfer, materials, aerodynamics, sensors, alternative fuels, and advanced cycles. This paper highlights the status of the AGTSR consortium and the feedback received from both industry and universities on the effectiveness and impact of the educational and research components of AGTSR.
Experimental Investigation of the Circumferential Static Pressure Distortion in Centrifugal Compressor Stages
Authors: Hagelstein D. , Van den Braembussche R. , Keiper R. , Rautenberg M.
Published: December 2014

The flow in a centrifugal compressor stage is dominated by the geometry of the impeller, the diffuser and the exit collecting chamber. Asymmetries of the flow field in the annular space behind the impeller may create a circumferential pressure distortion, influencing the energy transfer by the impeller in a negative way, creating variable force on the impeller blades and a radial force on the shaft.

Experimental investigations of the circumferential static pressure variations have been carried out on a large radial compressor test stand. Measurements with various impellers, diffusers and collecting chambers show the influence of geometrical modifications on the flow and compressor characteristics.

It is shown how a concentric exit chamber results in a very large pressure distortion in the diffuser. Although the amplitude of this distortion is increasing towards the diffuser inlet, it has a negligible effect on the pressure distortion upstream of the impeller.

It is further shown how the asymmetry of the flow in the diffuser can be reduced either by using a throttling ring at the diffuser exit, a vaned diffuser or by replacing the constant cross section collector by a volute with circumferentially increasing cross section.
High Freestream Turbulence Simulation in a Scaled-Up Turbine Vane Passage
Authors: Bangert B. A. , Kohli A. , Sauer J. H. , Thole K. A.
Published: December 2014

Quantifying high freestream turbulence effects on surface heat transfer and on blade boundary layer development is important for improving predictions of the thermal loading and aerodynamic losses for gas turbine blades, vanes, and endwalls. To improve our physical understanding as well as improve CFD capabilities, detailed flow and thermal field data is needed in addition to surface data. This paper discusses the development of a turbulence generator that is capable of generating turbulence intensities as high as 20% and yet allow an independent control on the turbulent length scale. The integral length scale at a turbulence intensity of TI = 20% ranged from 2.1 cm to 5.5 cm. The development of the turbulence generator took place in a wind tunnel having a large, constant area, test section. After this development, the turbulence generator was placed upstream of a scaled-up turbine vane. This paper also describes the development of the turbine vane test section that has a central first stage stator vane that was scaled up by a factor of nine. Finally, turbulence measurements, turbulent length scales, and energy spectra measured inside the turbine vane passage are presented and compared to measurements that were made in the constant area test section. The results indicate that in the first 40% of the stator vane passage, the turbulence levels rapidly decrease by a factor of four with the integral length scales having a rapid growth.
The Application of DLN Technology to the Tornado and Tempest Industrial Gas Turbines
Authors: Boyns Michael B. , Patel Rajeshri
Published: December 2014

Dry low NOX combustion technology has been successfully applied to the EGT Tornado and Tempest industrial gas turbines. This lean-premix technology has been based on that being employed in the EGT Typhoon gas turbine, as reported by Norster & De Pietro (1996) but with a number of modifications to suit the individual engines.

The Tornado is a 6.1 MWe machine designed in the late 1970’s for power generation and mechanical drive applications. The worldwide emissions legislation of recent years has provided the requirement to reduce NOX emissions in the exhaust, both for new machines and for those already in operation. Hence a system suitable for retrofitting as well as new production was required. The Tornado utilises similar burners to the Typhoon but with different combustion chambers and a different centre casing from the standard Tornado. Due to the differing cycle conditions, a different reaction zone stoichiometry has been used. A short rig test program followed by engine testing have achieved NOX emissions at base load significantly lower than the initial program target of 42 ppmv and led to the program target being revised to 25 ppmv.

The Tempest, launched into the market in 1995 produces 7.49 MWe in single shaft configuration and is aimed at the electrical power generation market. To comply with current emissions legislation, a DLN system has been developed. The Tempest is a 25% scale up of the Typhoon but its mechanical design incorporates a simplified main and pilot burner arrangement and a fully fabricated combustor. At base load, the Tempest operates at a higher turbine entry temperature than the Typhoon but has been designed such that the equivalence ratio in the reaction zone is slightly lower. A comprehensive test programme has demonstrated hardware which significantly improves upon the target emissions limit of 25 ppmv NOX.
Combustion of Coal-Derived Fuel Gas in an Oxygen-Blown Pressurized Topping Combustor
Authors: Hoppesteyn Peter D. J. , Andries Jans , Hein Klaus R. G.
Published: December 2014

Advanced integrated gasification combined cycle (IGCC) plants promise to be efficient and environmentally friendly systems to utilise solid fuels for the production of electricity and heat. An IGCC system consists of a gasifier, producing a low calorific value (LCV) fuel gas, and a gas turbine in which the LCV fuel gas is being combusted. At this time some demonstration IGCC plants have been commissioned in the United States and Europe. A sound understanding of the interaction between the gasifier and the gas turbine combustor is critical for successful operation of an IGCC system. Reliable theoretical and experimental information on the characteristics of the gas turbine as a whole and the combustor as such, leading to this information is needed prior to commercialisation of these IGCC systems. The combustion of natural gas in gas turbine combustors has been studied extensively. The combustion of coal-derived LCV fuel gas however has been studied in much less detail.

To obtain more fundamental data on the combustion of LCV fuel gas, a 1.5 MW pressurised fluidised bed gasifier (PFBG) with a separate pressurised topping combustor (PTC) has been designed, built and operated at Delft University of Technology (The Netherlands). The maximum system pressure is 10 bar. Experiments have been performed at 8 bar, using recirculated flue gas, steam and oxygen as gasifying agents. The produced LCV fuel gas is combusted in an oxygen blown PTC. In this way a flue gas with a high carbon dioxide concentration can be obtained from which the carbon dioxide can be removed more easily than from flue gases. A numerical model has been constructed to simulate the combustion of the LCV fuel gas in the PTC.

A detailed description of the test rig will be given. The first experimental results will be described and compared with simulation results obtained with the commercial Computational Fluid Dynamics code Fluent version 4.3. Finally the future work will be described.
An Investigation of Effectiveness and Heat Transfer on a Showerhead-Cooled Cylinder
Authors: Hoffs A. , Drost U. , Bölcs A.
Published: December 2014

An investigation of effectiveness and heat transfer on a cylinder model with showerhead cooling has been conducted in a free jet test facility, using the transient liquid crystal technique. A three- and a four-row configuration, covering a region of ±21°, were chosen to study the cooling behaviour for zero and off-design incidences. Typical engine airfoil leading edge conditions were maintained for the freestream Reynolds and Mach numbers to 1.55e5 and 0.26 for the three-row, and 1.84e5 and 0.30 for the four-row configuration, at a turbulence intensity of 7%. The blowing and momentum rates ware varied from 0.4 to 1.8 and 0.1 to 1.9, at a density ratio of 1.65. At zero incidence it could be observed for both configurations that the highest effectiveness of about 0.3 was achieved at a blowing rate of 0.4. Negative incidence for the four-row configuration resulted in much higher effectiveness, being as high as 0.5 at a blowing rate of 0.9, with an associated high heat transfer. Much lower effectiveness was achieved at positive incidence, where the blowing rate of 0.9 showed the best cooling behaviour. Higher effectiveness — but also increased heat transfer — was in general observed for the four-row configuration, with a 60% higher massflow.
Non Linear Behaviour of Oil Film Bearings and its Relevance in Force Identification Procedures
Authors: Bachschmid Nicolò , Dellupi Riccardo
Published: December 2014

The main differences in the calculated behaviour of an unbalanced rotor on two-lobe oil film bearings, in terms of mean statical position, 1 × rev. and 2 × rev. components in steady-state conditions, between the results obtained by means of the linearized and the non linear oil film models are shown.

The errors introduced by the linearized model are not negligible and can affect significantly the accuracy of results of numerical simulations. This may be unacceptable if one uses the measured vibrations in the bearings for identifying the exciting forces on the rotor in a model based diagnostic approach.

Therefore a method is presented which utilises the linear model of the rotor and the non linear oil-film forces in the identification procedure.
System Evaluation of JP-8+100 Additives at High Bulk Temperatures
Authors: Dieterle Gordon L. , Binns Kenneth E.
Published: December 2014

New tests were established early in the development of JP-8+100 fuel to provide system design information in addition to evaluating the JP-8+100 additives. Preliminary evaluation of the JP-8+100 additives indicated that a thermal stability improvement for JP-8 of 100°F (56°C) was achieved for the wetted wall temperature. Specific tests were conducted to evaluate various, additive concentrations and combinations for meeting the bulk fuel goal. Screening type tests were conducted in the Extended Duration Thermal Stability Test System. The promising additive candidates were then tested in the Advanced Reduced Scale Fuel System Simulator. These test systems were designed to provide information that is directly applicable to aircraft/engine fuel system designs. Based on the tests results of both the Extended Duration Thermal Stability Test and the Advanced Reduced Scale Fuel System Simulator, there were essentially zero deposits experienced at 385°F (196°C) bulk fuel temperatures with recirculation of JP-8+100 fuel. There were slight deposits experienced during tests of this fuel at 400°F (204°C) with recirculation. The description of the test systems and their operating characteristics along with the test results of the additive evaluations will be covered in this paper. A discussion of future fuel system applications and the potential payoff for JP-8+100 fuels will also be included.
Development of a Dry Low-NOx Combustor for the VT100 Automotive Gas Turbine
Authors: Johansson Patrik
Published: December 2014

The design and development of a pilot assisted dry low-NOx LPP (Lean Premix Prevaporized) combustor for the VT100 turbogenerator is described. The combustor was designed for and tested on ethanol, a renewable biofuel chosen to minimize the contribution to atmospheric CO2.

Engine specifications for pressure drop, operability and emissions have been met. The combustor has successfully demonstrated ultra low NOx and CO emissions below 10 and 20 ppmv respectively at the best engine conditions.

The rig testing was performed at reduced inlet temperatures and the fuel flow was scaled to achieve main combustion zone flame temperatures as in the engine. The results show good agreement for NOx vs. flame temperature between the rig and engine tests.

The dry low-NOx combustor for the VT100 turbogenerator meets the emission specification and gives the hybrid propulsion system the potential of meeting the foreseen (2010) NOx emission targets for urban delivery vehicles of 1 g/kWhe compared to today’s 7 g/kWhe.
Rotor Design in Industrial Gas Turbines
Authors: Florjancic Stefan S. , Pross Jörg , Eschbach Urban
Published: December 2014

The various design aspects of an industrial gas turbine rotor need special attention to ensure safe and reliable operation of the entire machine. The rotor has to fulfill the following main criteria and tasks: carry the blading, transmit the torque, define the aerodynamic channel geometry, guide the cooling air, provide sealing and bearing surfaces, and exhibit acceptable rotordynamic behavior. Additional criteria linked to the rotor design can be established, i.e., ease of manufacture and assembly, maintainability (where needed), transient blading tip clearances, rotational inertia, balance of axial thrust, and safety against fault conditions (blade loss, short circuit, hot-gas ingestion, etc.) with possibilities for subsequent repair. Industrial practice shows that there are several design approaches possible.

This paper describes the general requirements and how to assess the strength and the dynamic behavior under transient and steady state conditions. Additionally, the individual existing main design principles, i.e., stacked discs with individual centering and tie rod types, and monolithic or welded integral rotor design, are compared. Differences in levels of loading and in the dynamic behavior are outlined. Finally, an assessment of the individual rotor designs under fault conditions is given, and critical areas of the component under such conditions are discussed.
On-Site Liquid Gas Turbine Fuel Analysis for Trace Metal Contamination
Authors: Lukas M. , Anderson D. P.
Published: December 2014

Contamination levels of liquid fuel entering the combustor of a gas turbine must be low to avoid high temperature corrosion and fuel system fouling. Accordingly, each of the major industrial gas turbine manufacturers has strict contamination limits which must be met in order to comply with the warranty of the turbine. The responsibility to assure compliance lies with the owner of the power plant and can only be guaranteed with on-site fuel analysis for contaminants and ash-forming metals.

This paper discusses the various fuel analysis techniques available to the gas turbine user. It will review each technique’s ability to meet the need for fast and precise on-site analytical data. It will be demonstrated that the rotating disc electrode (RDE) atomic emission technique is the preferred analytical method for on-site fuel analysis. Actual field experience will be used to illustrate and discuss compromises that may be necessary to meet the objectives of the gas turbine user, fuel treatment supplier and turbine manufacturer.
Computation of Discrete-Hole Film Cooling: A Hydrodynamic Study
Authors: Berhe Mulugeta K. , Patankar Suhas V.
Published: December 2014

Hydrodynamic plots are presented from a numerical study conducted on a three dimensional film cooling geometry that includes the main flow, injection hole, and the plenum. The fully elliptic Navier-Stokes equations were solved over a body fitted grid using the control volume method. Turbulence closure was achieved using the k-ε turbulence model. The results presented include contour plots of the resultant velocity at hole exit, as well as streamwise mean velocity and turbulence intensity contours at several cross-stream planes. Computations were performed for blowing ratios of 0.5 and 1.0, and a density ratio of 2. The injection hole was 12.7 mm in diameter, 3.5 diameters long, and inclined at 35° to the streamwise direction. Results obtained from this analysis are compared with the available experimental results. Whereas the overall agreement is good, important differences were found. Compared to the experimental jet, the computed jet showed (a) a larger vertical velocity at hole exit, (b) a smaller lateral spread in the downstream region, especially at low blowing ratios.
The Computation of Adjacent Blade-Row Effects in a 1.5 Stage Axial Flow Turbine
Authors: Emunds Rolf , Jennions Ian K. , Bohn Dieter , Gier Jochen
Published: December 2014

This paper deals with the numerical simulation of flow through a 1.5 stage axial flow turbine. The 3-row configuration has been experimentally investigated at the University of Aachen where measurements behind the first vane, the first stage and the full configuration were taken. These measurements allow single blade row computations, to the measured boundary conditions taken from complete engine experiments, or full multistage simulations. The results are openly available inside the framework of ERCOFTAC 1996.

There are two separate but interrelated parts to the paper. Firstly, two significantly different Navier-Stokes codes are used to predict the flow around the first vane and the first rotor, both running in isolation. This is used to engender confidence in the code that is subsequently used to model the multiple bladerow tests, the other code is currently only suitable for a single blade row. Secondly, the 1.5 stage results are compared to the experimental data and promote discussion of surrounding blade row effects on multistage solutions.
A Numerical Investigation of Transonic Axial Compressor Rotor Flow Using a Low Reynolds Number k-ε Turbulence Model
Authors: Arima Toshiyuki , Sonoda Toyotaka , Shirotori Masatoshi , Tamura Atsuhiro , Kikuchi Kazuo
Published: December 2014

We have developed a computer simulation code for three-dimensional viscous flow in turbomachinery based on the time-averaged compressible Navier-Stokes equations and a low Reynolds number k-ε turbulence model. It is described in detail in this paper. The code is used to compute the flow fields for two types of rotor (a transonic fan NASA Rotor 67 and a transonic axial compressor NASA rotor 37), and numerical results are compared to experimental data based on aerodynamic probe and laser anemometer measurements. In the case of Rotor 67, calculated and experimental results are compared under the design speed to validate the code. The calculated results show good agreement with the experimental data, such as the rotor performance map and the spanwise distribution of total pressure, total temperature, and flow angle downstream of the rotor. In the case of Rotor 37, detailed comparisons between the numerical results and the experimental data are made under the design speed condition to assess the overall quality of the numerical solution. Furthermore, comparisons under the part speed condition are used to investigate a flow field without passage shock. The results are well predicted qualitatively. However, considerable quantitative discrepancies remain in predicting the flow near the tip. In order to assess the predictive capabilities of the developed code, computed flow structures are presented with the experimental data for each rotor and the cause of the discrepancies is discussed.
Nonlinear Separated Inviscid–Viscous Analysis of Oscillating Cascade Aerodynamics Using an Inverse Integral Method
Authors: Wolff James M. , Fleeter Sanford
Published: December 2014

A mathematical model is developed to analyze the unsteady flow through an harmonically oscillating cascade of airfoils, including separated flow. The model incorporates an inverse integral boundary layer solution with the time–marching Euler analysis NPHASE. An embedded composite grid formulation is incorporated, specifically a deforming C–grid embedded in a Cartesian H–grid, thereby simplifying grid generation. To reduce computational requirements, Fourier series unsteady periodic boundary conditions are implemented. The integral turbulent boundary layer model is closed with steady correlations adopted in a quasi–steady manner. To couple the inviscid and viscous solutions, the viscous effect is modeled in the unsteady Euler solution in a quasi–steady manner by a transpiration boundary condition. An isolated airfoil is used to compare the steady interaction model with experimental data. Then a flat plate cascade is used to verify the unsteady flow solver with linear theory predictions. An experimental unsteady aerodynamics data set of a loaded cascade with separated meanflow executing torsional oscillations compared favorably with the analysis. The code is then utilized to study the effect of flow separation on the unsteady aerodynamics.
Research and Development of 300kW Class Ceramic Gas Turbine Project in Japan
Authors: Arakawa Hironori , Suzuki Takayuki , Saito Kazufumi , Tamura Shigeru , Kishi Shinsuke
Published: December 2014

The ceramic gas turbine (CGT) engine can achieve higher thermal efficiency, lower pollutant emissions, and has a wider fuel tolerance compared to conventional gasoline and diesel engines. Accordingly, research and development of a 300kW class ceramic gas turbine has been performed in Japan as a national project since FY 1988, under the Agency of Industrial Science and Technology (AIST), which is an agency of the Ministry of International Trade and Industry (MITI). The final target of the project is to achieve 42% thermal efficiency at a Turbine Inlet Temperature (TIT) of 1350°C.

At present, two different types of ceramic gas turbines (CGT 301 and CGT 302) are under development and operating tests of prototype engines are being carried out. The CGT 301 features removable ceramic blades joined to a metal rotor disk. This 37 blade hybrid rotor of the high pressure stage was hot spin tested at a TIT of 1350°C and the burst of the blades did not occur at the rated speed. A thermal efficiency of 26.4% was achieved at a TIT 1200°C during the first year of prototype operation. Improvement in component parts is ongoing and as a result, improvements in thermal efficiency are forthcoming.

The CGT 302 features a lean premixed low-NOx combustor having a primary diffusion burner, a set of main pre-mixed burners, single fuel injector, and air bypass to control combustion. This combustor showed a lower pressure loss and NOx emissions of 5ppm (O2 = 16%), which is less than the allowable value of 70ppm. Recent operating tests of this engine showed a maximum output power and thermal efficiency of 228kW and 36%, respectively, as of November 1996.

For both the CGT 301 and CGT 302, more focused research on CGT materials and components, as well as operating tests at 1350°C TIT, are being carried out in order to reach the final target values.
Axial Compressor Stage Analysis Through a Multi-Block 3-D Navier-Stokes Solution Method
Authors: Politis E. S. , Giannakoglou K. C. , Papailiou K. D.
Published: December 2014

A method for the analysis of low-speed flows in compressor stages through a steady, 3-D, multi-block, Navier-Stokes solver is presented. For a complete stage, two pairs of 3-D grid blocks, one for the rotor and one for the stator, are used. The combination of two grids per row aims at the accurate modelling of the flow in the clearances between blade tips of finite thickness and annular walls. Thus, with such a numerical tool, the effect of rotor tip-clearance on the downstream stator performance, can be studied. Within each grid block, governing equations are solved in a segregated manner through the inversion of a single scalar coefficient matrix for all but the continuity equation. For the latter, a pressure correction equation is solved using a generalized residual minimization scheme. The interfaces between rows are treated through a simple mixing approach, based on the communication of circumferentially area-averaged quantities. The interfaces between grid blocks in the same row are treated by means of fake cells. Both interfacing schemes do not badly affect the convergence of the code. The method is used for the analysis of the third stage of a four-stage, low-speed compressor, for which unsteady flow phenomena do not dominate the physics of the flow. Numerical predictions are compared to data from experimental work carried out at the Cranfield University test rig.
Prediction of 3D-Unsteady Flow in an Air Turbine and a Transonic Compressor Including Blade Gap Flow and Blade Row Interaction
Authors: Jung Alexander R. , Mayer Jürgen F. , Stetter Heinz
Published: December 2014

This paper presents the results of three-dimensional unsteady Navier-Stokes simulations of the flow in a transonic compressor stage with inlet guide vanes and an axial flow air turbine stage with two identical stators for which detailed unsteady experimental data are available. Various unsteady flow phenomena are shown. The focus in the computations are stator/rotor interaction effects. Of special interest are their influences on the flow field downstream of the interface regions. The secondary flow effects are visualized via vector plots. The numerical results are compared with the experimental results. Although there is a good agreement in the major flow phenomena local deviations can be observed.
Entropy Generation in a 2-D Cascade at Different Angles of Attack: A Numerical Study
Authors: Natalini Gianni , Sciubba Enrico
Published: December 2014

This paper presents the results of an entropy generation calculation made on a representative gas turbine rotor blade; in particular, the numerical study has dealt with the different flowfields which are encountered when the angle of attack is varied in a two-dimensional cascade on axial, internally cooled gas turbine rotor.

The analysis takes into consideration a two-dimensional cascade at medium Reynolds number (Rechord = 225000), sub-sonic Mach number (Main = 0.27), and steady state. The full Navier-Stokes equations of motion for a turbulent compressible viscous flow, together with the appropriate energy equation, are solved via a standard finite elements code with a k-ε closure, so that complete velocity- and temperature fields are obtained (including boundary-layer effects, via proper wall functions). These fields are then used to compute the entropy generation rates corresponding to the viscous- (Ṡv) and thermal (Ṡr) dissipation.

Several configurations have been numerically tested, the reference one being at design conditions, and the remaining being obtained from it by varying the angle of attack α (defined as the angle, measured ccw, between the relative velocity vector W1 and the tangent to the blade chord at impingement point), to simulate volume flowrate variations.

A commercial finite-element code (FIDAP, by FDI Inc.) has been modified to allow for the calculation of the local values of the entropy generation rates, the thermal- and viscous portions of which have been computed separately.

The results at design point are shown to agree well with the available cascade performance data.

The entropy generations rates are then used to compute the so-called entropy loss coefficient (a better name for which would be that of irreversibility coefficient, ζ, defined as:ζ=T0Δsh1s-h2iwhere T0 is the reference ambient temperature, Δs is the total local entropy generation rate (sum of the viscous- and thermal components), and h1i and h2i are the stagnation enthalpy upstream of the rotor and the ideal exit enthalpy respectively.

The results are shown under the form of cp - and ζ graphs computed for different angles of attack α (from −4.4 to +7.6 degrees), and are representative of realistic situations which could arise in actual gas turbine rotors. The loss coefficient ζ is shown to attain a minimum value at design point.

Integral values for the entropy generation rates are also computed, and total entropy losses are thus computed for the various configurations. Maps of the viscous- and thermal entropy generation rates are shown for each angle of attack, where of interest.
Engine Representative Discharge Coefficients Measured in an Annular Nozzle Guide Vane Cascade
Authors: Rowbury D. A. , Oldfield M. L. G. , Lock G. D.
Published: December 2014

This paper discusses measurements of the discharge coefficients of gas turbine nozzle guide vane film cooling holes under fully engine representative conditions. These unique experiments were carried out in a large scale annular blowdown cascade which models the three-dimensional external, flow patterns found in modern aero-engines, including all secondary flow phenomena. Furthermore, the coolant system design allows the coolant-to-mainstream density ratio and blowing parameter to be matched to engine values, although they can be independently varied.

The results confirm that the discharge coefficients of film cooling holes are significantly altered by external crossflow. The discharge coefficient is usually reduced by external crossflow, but under certain external flow conditions it can be increased over the non-crossflow case. This previously unhightighted phenomenon has been termed ‘the crossover effect’, and, although an initially surprising result, is of importance to aero-engine designers as taking account of it should lead to improved predictions of coolant consumption. As a consequence, more uniform blade cooling should be achieved and, in turn, the attainment of greater component durability will be possible.
Three Dimensional Unsteady Pressure Measurements for an Oscillating Turbine Blade
Authors: Bell D. L. , He L.
Published: December 2014

A complete set of unsteady blade surface pressure measurements is presented for a single turbine blade oscillating in a three dimensional bending mode. Results are provided for five spanwise sections at 10%, 30%, 50%, 70% and 90% of span. Steady blade pressure measurements and five-hole probe traverses at the inlet and exit planes of the test section, are also included.

The test facility operates at low speed and the working section consists of a single turbine blade mounted in a profiled duct. A rigid blade with constant section was used, and a three dimensional bending mode realised by hinging the blade at root and driving the tip section. The low speed and scale of the test facility allowed low oscillation frequencies (5 to 20 Hz) to be employed, in order to match realistic reduced frequencies. This enabled the unsteady blade surface pressure response to be recorded with externally mounted pressure transducers. The validity of this technique is examined. Results from the test facility demonstrate a noticeable three dimensional behaviour of the unsteady flow.