bluuebunny/crossref_metadata_2025 huggingface dataset:
45° Round-Corner Rib Heat Transfer Coefficient Measurements in a Square Channel
Authors: Taslim M. E. , Lengkong A.
Published: December 2014

Cooling channels, roughened with repeated ribs, are commonly employed as a means of cooling turbine blades. The increased level of mixing induced by these ribs enhances the convective heat transfer in the blade cooling cavities. Many previous investigations have focused on the heat transfer coefficient on the surfaces between these ribs and only a few studies report the heat transfer coefficient on the rib surfaces themselves. The present study investigated the heat transfer coefficient on the surfaces of 45°, round-comer ribs. Three staggered rib geometries corresponding to blockage ratios of 0.133, 0.167 and 0.25 were tested in a square channel for pitch-to-haight ratios of 5, 8.5 and 10, and for two distinct thermal boundary conditions of heated and unhealed channel wall. Comparisons were made between the surface averaged heat transfer coefficients and channel friction factors for sharp- and round-comer ribs and 45° versus 90° ribs, reported previously. Heat transfer coefficients of the furthest upstream rib and that of a typical rib located in the middle of the rib-roughened region were also compared. It was concluded that: a) For the geometries tested, the rib average heat transfer coefficient was much higher than that for the area between the ribs. b) General effect of rounding the rib corners was a decrease in both rib heat transfer coefficient and channel pressure drop. c) For the highest blockage ratio ribs (e/Dh = 0.25), 90° ribs performed superior to 45° ribs. However, this trend reversed for smaller rib blockage ratios. d) Heat transfer coefficients for the two smaller rib geometries (e/Dh = 0.133 and 0.167) did not vary significantly with the pitch-to-height ratio in the range tested. However, the heat transfer coefficient for the high blockage rib geometry increased significantly as the ribs were brought closer to each other. e) Under otherwise identical conditions, ribs in the furthest upstream position produced lower heat transfer coefficients than those in the midstream position. f) Rib thermal performance decreased with the rib blockage ratio. The smallest rib geometry (e/Dh = 0.133) at a pitch-to-height ratio of 10 and the largest rib geometry (e/Dh = 0.25) at a pitch-to-height ratio of 5, both in midstream position, produced the highest and the lowest thermal performances, respectively.
The Effect of Time of Exposure to Elevated Temperatures on the Flammability Limits of Some Common Gaseous Fuels in Air
Authors: Ale B. B. , Wierzba L.
Published: December 2014

The flammability limits of methane, ethylene, propane and hydrogen were determined experimentally at elevated initial mixture temperatures up to 350°C at atmospheric pressure for upward flame propagation in a steel test tube apparatus. The existence of preignition reactions at these levels of temperatures that may influence the value of the flammability limits was also investigated. The fuel-air mixtures were exposed to elevated temperatures over different periods of time before spark ignition (up to 2 hours). It was shown that the flammability limits for methane widened approximately linearly with an increase in the initial mixture temperature over the entire range of temperatures tested and were not affected by the length of the exposure time to these temperatures before spark ignition. However, different behaviour was observed for the flammability limits of the other tested fuels — ethylene, propane and hydrogen. At higher temperatures the flammability limits narrowed and were very significantly affected by the exposure time. The longer was the exposure time of fuel-air mixtures to the elevated temperatures, the narrower were their flammability limits.
Ceramic Stationary Gas Turbine Development Program — Fifth Annual Summary
Authors: Price Jeffrey R. , Jimenez Oscar , Faulder Les , Edwards Bryan , Parthasarathy Vijay
Published: December 2014

A program is being performed under the sponsorship of the United States Department of Energy, Office of Industrial Technologies, to improve the performance of stationary gas turbines in cogeneration through the selective replacement of metallic hot section components with ceramic parts. The program focuses on design, fabrication, and testing of ceramic components, generating a materials properties data base, and applying life prediction and nondestructive evaluation (NDE). The development program is being performed by a team led by Solar Turbines Incorporated, and which includes suppliers of ceramic components, U.S. research laboratories and an industrial cogeneration end user.

The Solar Centaur 50S engine was selected for the development program. The program goals included an increase in the turbine rotor inlet temperature (TRIT) from 1010°C (1850°F) to 1121°C (2050°F), accompanied by increases in thermal efficiency and output power. The performance improvements are attributable to the increase in TRIT and the reduction in cooling air requirements for the ceramic parts. The ceramic liners are also expected to lower the emissions of NOx and CO.

Under the program uncooled ceramic blades and nozzles have been inserted for currently cooled metal components in the first stage of the gas producer turbine. The louvre-cooled metal combustor liners have been replaced with uncooled continuous-fiber reinforced ceramic composite (CFCC) liners. Modifications have been made to the engine hot section to accommodate the ceramic parts.

To-date all first generation designs have been completed. Ceramic components have been fabricated, and are being tested in rigs and in the Centaur 50S engine. Field testing at an industrial co-generation site was started in May, 1997. This paper will provide an update of the development work and details of engine testing of ceramic components under the program.
Preliminary Design of Low Cost Propulsion Systems Using Next Generation Cost Modeling Techniques
Authors: Younghans J. L. , Donaldson R. M. , Wallace D. R. , Long L. L. , Stewart R. B.
Published: December 2014

At GE Aircraft Engines (GEAE), during the preliminary design process for aircraft propulsion systems, the designer has always been concerned about the cost implications of engine architecture and material requirements, which are driven by design specified engine thermodynamic operating conditions. The concern was not only about initial acquisition economics, but about maintenance costs associated with the propulsion life cycle as well as the development costs associated with design and certification of the power plant. The difficulty has been that there was no rapid, accurate cost estimating process to allow the designers ready access to the cost implications of design choices. High cycle pressure ratios and bypass ratios were thermodynamically attractive in reducing SFC. Technology, whether in the form of complex aerodynamic blade shapes to increase efficiency or higher temperature materials to reduce undesirable effects of cooling flows on SFC, was considered without in depth quantitative cost impacts of these design choices.
Development of a Five-Step Global Methane Oxidation–NO Formation Mechanism for Lean-Premixed Gas Turbine Combustion
Authors: Nicol David G. , Malte Philip C. , Hamer Andrew J. , Roby Richard J. , Steele Robert C.
Published: December 2014

It is known that many of the previously published global methane oxidation mechanisms used in conjunction with computational fluid dynamics (CFD) codes do not accurately predict CH4 and CO concentrations under typical lean-premixed combustion turbine operating conditions. In an effort to improve the accuracy of the global oxidation mechanism under these conditions, an optimization method for selectively adjusting the reaction rate parameters of the global mechanisms (e.g., pre-exponential factor, activation temperature and species concentration exponents) using chemical reactor modeling is developed herein. Traditional global mechanisms involve only hydrocarbon oxidation; that is, they do not allow for the prediction of NO directly from the kinetic mechanism. In this work, a two-step global mechanism for NO formation is proposed to be used in combination with a three-step oxidation mechanism. The resulting five-step global mechanism can be used with CFD codes to predict CO, CO2, and NO emission directly. Results of the global mechanism optimization method are shown for a pressure of 1 atmosphere and for pressures of interest for gas turbine engines. CFD results showing predicted CO and NO emissions using the five-step global mechanism developed for elevated pressures are presented and compared to measured data.
Project Optimisation and Construction of Cogeneration Power Plant for a Large Refinery and Petrochemical Complex in India
Authors: Sheikh Ali , Rozewicz Joseph , Kadkol R. V.
Published: December 2014

Configuration and design of cogeneration power plant supplying 374 MW electric power and 1500 t/h process steam for a new Reliance Jamnagar Refinery and Petrochemical Complex have been optimised on the basis of (i) reliability of power and steam supplies, (ii) fuel availability, (iii) capital and operating cost, and (iv) synergy between the refinery and petrochemical complex, and power plant start-up schedules.

The basic equipment of the power plant consists of 8 Gas Turbines of average site rated power output 31.7 MW per unit, 4 Steam Turbines of 30 MW power output each, 8 HRSG with supplementary firing each having capacity of 125 t/h and 4 conventional Steam Generators of capacity 125 t/h each. The steam generation parameters are: pressure 113.8 bar and temperature 510 °C. The cogeneration power plant also supplies for the refinery complex high pressure steam and intermediate pressure steam extracted from steam turbines.

An analysis of various normal and upset operating scenarios of the refinery complex was carried out to achieve optimal selection of the equipment ensuring the required steam and power supply.
Flow and Heat Transfer in a Ribbed U-Duct Under Typical Engine Conditions
Authors: Shih T. I-P. , Lin Y.-L. , Stephens M. A. , Chyu M. K. , Civinskas K. C.
Published: December 2014

Computations were performed to study the three-dimensional flow and heat transfer in a ribbed U-shaped duct of square cross section under operating conditions that are typical of industrial gas turbines. Basically, all walls were maintained at a temperature of 800 K, and the coolant air at the duct inlet had a temperature of 550 K and a pressure of 10 atm. Both rotating and non-rotating cases were investigated. When rotating, the angular speed was 3,600 rpm. The Reynolds number based on the duct hydraulic diameter was set at 350,000, which represents an upper limit in coolant flow. The results obtained in this study were compared with those from previous numerical studies with a lower Reynolds number, namely 25,000, which represents a lower limit in coolant flow.

This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy. Turbulence is modelled by two low-Reynolds number k-ω models: an SST version with isotropic eddy diffusivity and a nonlinear version with anisotropic eddy diffusivity from an explicit algebraic Reynolds stress model. Solutions were generated by using a cell-centered finite-volume method, that is based on flux-difference splitting and a diagonalized alternating-direction implicit scheme with local time-stepping and V-cycle multigrid.
Gas Turbine Uprating Programme Development and Testing of the GT11NM
Authors: Schneider Christoph , Navrotsky Vladimir , Harasgama Prith
Published: December 2014

ABB has approximately 200 GT11N and GT11D type gas turbines currently operating in simple cycle and combined cycle power plants. Most of these machines are fairly mature with many approaching the end of their economic life. In order that the power producer may continue to operate a fleet with improved performance, Advanced Air Cooling Technology and Advanced Turbine Aerodynamics have been utilized to uprate these engines with the implementation of a completely new turbine module.

The objective of the uprating program was to implement the advanced aero/cooling technology into a complete new turbine module with:

• Improved power output for the gas turbine

• Increase the GT cycle efficiency

• Maintain or improve the gas turbine RAM (Reliability, Availability & Maintainability)

• Reduce the Cost of Electricity

• Maintain or reduce the emissions of the gas turbine

The GT11NM gas turbine has been developed based on the GT11N which has been in operation since 1987 and Midland Cogeneration Venture (MCV-Midland, Michigan) was chosen to demonstrate the uprated GT11NM. The upate/retrofit of the GT11N engine was conducted in May/June 1997 and the resulting gas turbine - GT11NM has met and exceeded the performance goals set at the onset of the development program.

The next sections detail the main changes to the turbine and the resulting performance improvements as established with the demonstration at Midland, Michigan.
Compatibility of Advanced Power Generation Technologies With the Independent Power Production
Authors: Susta Miro R. , Luby Peter
Published: December 2014

Traditional philosophy of power producing state-owned utilities has been effected by their anonymous risk-sharing attitude. They needn’t have bothered too much with brand-new technologies. Technological risk with unproved, although excellent nominal performance machinery was born by the end-users.

On the other hand, independent power producers’ (IPP) philosophy is a little bit different. Their attitude is much more effected by risk evaluation. They have pretty good reasons to be risk-averse with technologies lacking a proven operational record. Any failure to obey their contractual liabilities could mean dramatic consequences to them. Consequently, old-fashioned players in the power generation industry may seem to have been pushing industry technical progress more effectively ahead than it would be with modem players - IPPs.

But this is only one side of the coin. Quite opposite reasons for IPPs’ affinity to modern technologies are higher performance parameters which offer better revenues to them, more flexible choice of fuel and prompt readiness to react sensitively to market imbalance and volatilities. Obviously, a hardly-defined, yet sensible equilibrium under which both these trends coexist and inter-act here exists. In this paper we shall analyse factors affecting such equilibrium by presenting real examples of gas turbine-dependent power generation technologies.
Radiation and Convection Heat Flux Sensor for High Temperature Gas Environment
Authors: Martins Nelson , Carvalho Maria da Graça , Afgan Naim , Leontiev Alexander Ivanovich
Published: December 2014

The heat flux measurement is one of the essential parameter for the diagnostic of thermal systems. In the high temperature environment there are difficulties in differentiating between the convective and radiation component of heat flux on the heat transfer surface. A new method for heat flux measurement is being developed using a porous sensing element. The gas stream flowing through the porous element is used to measure the heat received by the sensor surface exposed to the hot gas environment and to control whether or not the sensing element receives the convection component of the total heat flux. It is possible to define a critical mass flow rate corresponding to the destruction of the boundary layer over the sensing element. With subcritical mass flow rate the porous sensing element will receive both the convective and radiative heat fluxes. A supercritical mass flow rate will eliminate the convective component of the total heat flux. Two consecutive measurements considering respectively a critical and a sub-critical mass flow rate can be used to determine separately the convection and radiation heat fluxes.

A numerical model of sensor with appropriate boundary condition has been developed in order to perform analysis of possible options in the design of the sensor. The analysis includes: geometry of element, physical parameters of gas and solid and gas flow rate through the porous element.

For the optimal selection of the relevant parameters an experimental set-up was designed, including the sensor element with corresponding cooling and monitoring system and high temperature radiation source. Applying the respective measuring procedure the calibration curve of the sensor was obtained. The linear dependency of the heat flux and respective temperature difference of the gas was verified. The accuracy analysis of the sensor reading has proved high linearity of the calibration curve and accuracy of ± 5%.
Effect of the Flame Dome Depth and Improvement of the Pressure Loss in the Dump Diffuser
Authors: Honami Shinji , Tsuboi Wataru , Shizawa Takaaki
Published: December 2014

This paper presents the effect of flame dome depth on the total pressure performance and flow behavior in a sudden expansion region of the combustor diffuser without flow entering the dome head. The mean velocity and turbulent Reynolds stress profiles in the sudden expansion region were measured by a Laser Doppler Velocitmetry (LDV) system. The experiments show that total pressure loss is increased, when flame dome depth is increased. Installation of an inclined combuster wall in the sudden expansion region is suggested from the viewpoint of a control of the reattaching flow. The inclined combustor wall is found to be effective in improvement of the diffuser performance. Better characteristics of the flow rate distribution into the branched channels are obtained in the inclined wall configuration, even if the distorted velocity profile is provided at the diffuser inlet.
A New Method for Surge Margin Improvement of Booster Compressors in Modern Aeroengines
Authors: Peitsch Dieter , Kurz Nikolaus , Fiola Roland
Published: December 2014

The subject of this paper is the development and first analysis of the performance of a new booster bleed valve control logic to improve the surge margin of the booster compressor in the new BR715 turbofan.

The booster compressor is driven by the LP spool of the two spool engine, comprising an aerodynamically tuned system out of fan root and booster compressor. The flow delivered at the exit of the booster compressor must be accepted by the following HP compressor. This matching is not always possible, since the rates of change of the spool speeds during transients behave differently as do pressure rise and mass flow. Hence the transient handling of the booster compressor is difficult with respect to its surge stability. To aid in this situation it is a common practice to position a booster bleed valve after the booster compressor, which passes bleed air into the bypass duct.

The BR715 jet engine takes advantage of a newly developed logic driving this valve. Monitoring input parameters such as spool and flight speeds as well as altitude, the logic provides the capability of appropriately positioning the valve, thereby maintaining an optimum performance of the engine throughout the whole operating range. Furthermore the logic allows for reaction on thrust reverser deployment or more serious events such as surge and foreign object damage.

Much effort has been put into the development of the newly designed transient valve logic, which in its main part is based on the rate of change of the pressure at the exit of the HP compressor. This logic ensures a sufficient surge margin in case of deceleration or reslams of the engine.

A simulation of the logic was set up, connected to a synthesis program for the two spool engine and used for the development. After this basic testing, the logic was implemented in the BR715 engine, which first ran in April 1997. The actual data from basic handling tests performed with this engine were analysed and checked against simulation results. The paper describes the logic in detail and contains first results. They prove a proper working of the logic and show the strong effect of the booster bleed valve.
Effects of High Freestream Turbulence Levels and Length Scales on Stator Vane Heat Transfer
Authors: Radomsky R. W. , Thole K. A.
Published: December 2014

Gaining a good understanding of how high freestream turbulence augments heat transfer is important for predicting thermal loadings for turbine blades and vanes. This study was aimed at documenting the surface heat transfer and the highly turbulent flowfield around a stator vane. The effects of turbulence levels between 11% and 24% were studied. At the highest turbulence level, two different Reynolds numbers (Reex = 6 × 105 and 1.2 × 106) and two different length scales were also studied. Three-component laser Doppler velocimeter measurements of the velocity fluctuations indicated that downstream of the active grid there was an initial decay of the turbulent kinetic energy which then leveled off at about one leading edge radius upstream of the vane. Inside the vane passage the turbulent kinetic energy increased slightly and then decayed through the passage. The surface heat transfer showed the largest augmentations on the pressure side of the vane with higher augmentations at higher turbulence levels, smaller length scales, and higher Reynolds numbers.
Comparison of Measurement Data at the Impeller Exit of a Centrifugal Compressor Measured With Both Pneumatic and Fast-Response Probes
Authors: Roduner C. , Köppel P. , Kupferschmied P. , Gyarmathy G.
Published: December 2014

The main goal of these investigations was the refined measurement of unsteady high-speed flow in a centrifugal compressor by using the advanced FRAP® fast-response aerodynamic probe system. The present contribution focusses on the impeller exit region and shows critical comparisons between fast-response (time-resolving) and conventional pneumatic probe measurement results.

Three probes of identical external geometry (1 fast and 2 pneumatic) were used to perform wall-to-wall traverses close to the impeller exit. The data shown refer to a single running condition near the best point of the stage.

The mass flow obtained from different probe measurements and from the standard orifice measurement were compared. Stage work obtained from temperature rise measured with a FRAP® probe and from impeller outlet velocity vectors fields by using Euler’s turbine equation are presented.

The comparison in terms of velocity magnitude and angle distribution is quite satifactory, indicating the superior DC measurement capabilities of the fast-response probe system.
Simulation of Vortex Shedding in a Turbine Stage
Authors: Sondak Douglas L. , Dorney Daniel J.
Published: December 2014

Vortex shedding in a turbomachine blade row is affected by the passing of blades in the adjacent downstream blade row, but these effects have not been examined in the literature. A series of flow simulations has been performed to study vortex shedding in a turbine stage, and to quantify the blade interaction effects on the unsteady pressure response.

The numerical issues of spatial order of accuracy and the use of Newton subiterations were first investigated. Second order spatial accuracy was shown to be inadequate to accurately model the shedding frequency response and time-averaged base pressure. For the small time step employed for temporal accuracy, Newton iterations were shown to be unnecessary.

The effects of the adjacent blade row were examined by comparing the shedding frequency response for the stage simulations to the response for isolated cascades. The vane shedding was shown to occur exactly on a series of harmonics of the blade passing frequency for the stage case, compared to a single predominant frequency for the isolated cascade.

Losses were also examined in the wake region. It was shown that close to the trailing edge, losses were mainly due to wake mixing. Farther downstream of the trailing edge, losses were predominantly due to the trailing edge shock wave.
Excitation Mechanism for Standing Stall of Centrifugal Compressors
Authors: Chen Y. N. , Hagelstein D. , Haupt U. , Rautenberg M.
Published: December 2014

The standing stall of the centrifugal compressors appears with pulsating or switching pattern at operating points slightly away from the stall line. It is a weak form of the rotating stall and stands still in the absolute frame. The reverse flow of the compressed warm fluid travelling from the impeller’s outlet along the shroud surface towards the inlet is not yet powerful enough to generate rotating stall. The experimental investigations revealed that in the low-flow-rate off-design region, the inlet flow to the impeller has a large positive incidence angle. Nose bubbles are formed on the suction surface of the blade after the leading edge. Once the reverse flow as a pressure wave reaches the inlet of the blades, the nose bubble is stagnated to an enlarged size. The corresponding disturbance sends a rarefaction wave in the forward direction into the impeller. This wave of cool fluid meets the reverse pressure wave of the warm fluid at a circular front around the circumference of the impeller. Since this circular front has a weak baroclinicity, it cannot develop into Rossby waves which initiate the rotating stall. Instead it will either pulsate concentrically or switch linearly. We then experience a standing stall with the corresponding pattern.
Effect of Unsteady Wake With Trailing Edge Coolant Ejection on Film Cooling Performance for a Gas Turbine Blade
Authors: Du Hui , Ekkad Srinath V. , Han Je-Chin
Published: December 2014

The effect of unsteady wakes with trailing edge coolant ejection on surface heat transfer coefficients and film cooling effectiveness is presented for a downstream film-cooled turbine blade. The detailed heat transfer coefficient and film effectiveness distributions on the blade surface are obtained using a transient liquid crystal technique. Unsteady wakes are produced by a spoked wheel-type wake generator upstream of the five-blade linear cascade. The coolant jet ejection is simulated by ejecting coolant through holes on the hollow spokes of the wake generator. For a blade without film holes, unsteady wake increases both pressure side and suction side heat transfer levels due to early boundary layer transition. Adding trailing edge ejection to the unsteady wake further enhances the blade surface heat transfer coefficients particularly near the leading edge region. For a film-cooled blade, unsteady wake effects slightly enhance surface heat transfer coefficients but significantly reduces film effectiveness. Addition of trailing edge ejection to the unsteady wake has a small effect on surface heat transfer coefficients compared to other significant parameters such as film injection, unsteady wakes, and grid generated turbulence, in that order. Trailing edge ejection effect on film effectiveness distribution is stronger than on the heat transfer coefficients.
Rotating Stall Control in a High-Speed Stage With Inlet Distortion: Part I — Radial Distortion
Authors: Spakovszky Z. S. , Weigl H. J. , Paduano J. D. , van Schalkwyk C. M. , Suder K. L. , Bright M. M.
Published: December 2014

This paper presents the first attempt to stabilize rotating stall in a single-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Research Center on a single-stage transonic core compressor inlet stage. An annular array of 12 jet-injectors located upstream of the rotor tip was used for forced response testing and to extend the compressor stable operating range. Results for radial distortion are reported in this paper.

First, the effects of radial distortion on the compressor performance and the dynamic behavior were investigated. Control laws were designed using empirical transfer function estimates determined from forced response results. The transfer functions indicated that the compressor dynamics are decoupled with radial inlet distortion, as they are for the case of undistorted inlet flow. Single-input-single-output (SISO) control strategies were therefore used for the radial distortion controller designs.

Steady axisymmetric injection of 4% of the compressor mass flow resulted in a reduction in stalling mass flow of 9.7% relative to the case with inlet distortion and no injection. Use of a robust H∞ controller with unsteady non-axisymmetric injection achieved a further reduction in stalling mass flow of 7.5%, resulting in a total reduction of 17.2%.
Active Control of Combustion Instability in a Liquid–Fueled Low–NOx Combustor
Authors: Cohen Jeffrey M. , Rey Nancy M. , Jacobson Clas A. , Anderson Torger J.
Published: December 2014

A practical active control system for the mitigation of combustion instability has been designed and demonstrated in a lean, premixed, single -nozzle combustor at realistic engine operating conditions. A full -scale engine fuel nozzle was modified to incorporate a simple fuel flow actuator. Results indicate that the system was capable of reducing pressure fluctuations by 82% (15 dB or 5.6X) while maintaining or reducing NOx and CO emissions levels.
Current Status of the CGT301, Ceramic Gas Turbine
Authors: Taoka Tomoki , Tanaka Shinya , Tatsuzawa Masashi , Sakida Takeshi
Published: December 2014

CGT301 ceramic gas turbine is being developed under a contract from NEDO as a part of the New Sunshine Program of MITI to improve the performance of gas turbine for co-generation through the replacement of the hot section components with ceramic parts.

CGT301 is a recuperated, single-shaft ceramic gas turbine. We have been developing some unique technologies, such as the “hybrid” rotor, composed of a metal disk and inserted ceramic blades, considering the future applicability to larger gas turbines.

We could attain the good engine performance with the primary type CGT at a TIT of 1,200°C. The reliability of the hybrid rotor was confirmed at a TIT of 1,350°C on the test rig.

We conducted preliminary tests using the primary type CGT to extract the possible problems derived from the higher TIT. Some modifications were made and the engine operation at a TIT of 1,280°C was conducted successfully.

On the basis of those experiences we finished the design and fabrication of the pilot CGT.

This paper presents the progress in the development of CGT301.
Renewable Fuels Turbine Project
Authors: Ali Sy A. , Parks William P.
Published: December 2014

An increasing demand for efficient and environmentally clean use of biomass and wood waste byproducts as fuel requires major developments in gas turbines. Gas turbines are designed primarily to handle either natural gas or in some cases diesel fuels. Introducing low BTU, contaminants containing biofuels into a gas turbine would require proper understanding of fuel characteristics, combustor capability to burn these fuels, compressor surge margins, and ability of the turbine section to withstand deposition, erosion and corrosion.

Allison Engine Company (Allison), in cooperation with the U.S. Department of Energy and other partners, has initiated a bioturbine development project which would lead to commercialization of a bioturbine to operate on major categories of biofuels. The project will address six key issues:

• Quantify chemical, physical and combustion characteristics of biofuels, gasifiers, and the mass volume

• Conduct emission modeling of existing combustor with low BTU fuels

• Conduct rig tests

• Modify current design of the combustor to handle low BTU fuels

• Evaluate compressor surge margins to handle increased mass flows

• Conduct full scale engine field test

The total cost of this two and a half years project is approximately $8 million. The DOE will contribute over $3 million. Allison and partners will contribute the remaining $5 million.

There is an additional vital task which must be performed, but is not a part of the current project. The capability of the turbine to withstand deposition, erosion and corrosion must also be evaluated in order to protect the turbine, and provide long term, uninterrupted operation of the gas turbine on biofuels.

An important first step is to obtain quantitative data on gasified biofuels, including the contaminants. This information will be used in combustor modeling and to develop rig tests. The combustor will then be modified and made capable of handling these fuels. Allison will use the 601-K engine combustor (similar to the RB211 DLE combustor), and modify its hardware and software as required. The combustor modification will involve modeling, rig test, hardware and software modifications, and final engine test The entire project is expected to be complete during the second half of 1999.

Concurrent with these tasks, Allison will evaluate the options available to increase the capability of engine mass flow due to low BTU fuels. A parallel task of “ruggedizing” the turbine section is also planned. The resulting turbine is expected to be comparable to natural gas fired commercial gas turbines in performance, durability, reliability and major overhaul cycles.
Numerical Investigation of Internal Flow Field for Modified Design of Eckardt Backswept Impeller
Authors: Oh JongSik
Published: December 2014

The three dimensional blade shape of Eckardt’s backswept impeller was modified, expecting better aerodynamic performance of the internal flow field. Blade angle distributions and parts of the meridional contours were changed, while impeller diameter, blade number, blade thickness and blade inlet and exit angles remained unchanged. The casing contour in the vaneless diffuser is additionally changed in a smooth manner to obtain 15% pinched flow channel at the exit. With the help of the three dimensional compressible Navier-Stokes analysis method, some improvements in the aerodynamic characteristics of the internal flow field were found; a more uniform flow field in the circumferential direction at impeller discharge was established, and a more favorable rise of static pressure near the casing in the impeller passage was made. A more effective increase of static pressure in the vaneless diffuser was also found. But a less uniform flow field in the spanwise direction at impeller exit resulted. The same levels of total-to-total pressure ratio and isentropic efficiency of the compressor were obtained, while an increase of choking flow rate was obtained due to increased throat area.
Vibration Measurement Techniques on an Industrial Gas Turbine Rotor Train
Authors: Florjancic Stefan S. , Franklin Wes , Lively Noel
Published: December 2014

The rotordynamic behavior of an industrial gas turbine rotor train was assessed on site, and the sensitivity to unbalance was quantified. An outline of the measurement procedure is given.

Differential data reduction with test unbalances was undertaken to minimize the influence of measurement uncertainty. A test unbalance was installed for one run and then shifted by 180° for the consecutive run. With differential data, the effective dynamic properties of the rotor - support - system can be estimated more accurately.

A rotordynamic model was used to identify the support system parameters based on measured data. For the analysis, the anisotropic, elliptical vibration orbits were decomposed into two counter-rotating circular orbits, and the support system parameters identified match the originally predicted values well.

The methods of differential data reduction, rotor train mode shape presentation, elliptical orbit decomposition, and the link of measurement to analytical models with parameter definition are described. Examples from on-site measurements are included for illustration.
Experimental Development of a Jet Injection Model for Rotating Stall Control
Authors: Vo Huu Duc , Paduano James D.
Published: December 2014

The effectiveness of jet actuation for active modal control of rotating stall is investigated experimentally. The dominant physical effects of injection, such as momentum and mass addition, are elucidated. The results indicate that several of the theoretical assumptions used in past studies of jet injection for rotating stall control must be revised. An updated model of the compression system with jet actuation which allows for the effect of control feedback dynamics to be adequately characterized is developed and verified with forced response measurements. It predicts the right trends of movement of the critical pole. Preliminary active control results are presented, among which is a 5.5% range extension in downstream flow coefficient.
Influence of an Aluminide Coating on the TMF Life of a Single Crystal Nickel-Base Superalloy
Authors: Affeldt Ernst E.
Published: December 2014

TMF tests were conducted with bare and aluminide coated single crystal nickel-based superalloy specimens. Temperature cycling was between 400°C and 1100°C with a phase shift (135°) which is typical for damaged locations on turbine blades. Stress response is characterized by a constant range and the formation of a tensile mean stress as a result of relaxation in the high temperature part of the cycle which is in compression. Bare specimens showed crack initiation from typical oxide hillocks. Coated specimens showed life reduction with respect to the bare ones caused by brittle cracking of the coating in the low temperature part of the cycle. Isothermal bending tests of coated specimens confirmed the low ductility of the coating at tempeatures below 600°C but quantitative correlation with the TMF test results failed.
Large-Scale Handling and Use of Solid Biofuels
Authors: Schmidt Erik Ravn , Clausen Jens Christian , Luxhøi Fritz
Published: December 2014

Utilising biomass in the CHP production is not without difficulties: the chemical and physical characteristics of the biofuels; corrosion, slagging and fouling; and working environment. An in-situ high-temperature corrosion monitoring test system was successfully developed. Furthermore, activities have been launched to develop a straw pre-processing method separating the aggressive substances from straw.

As a result of the gasification projects (straw, coal-straw, wood chips) it was concluded that it is possible to gasify straw — probably for 100% straw and definitely for 50/50 blends, although with some difficulties — and for wood chips deposit formation was a major obstacle. Further R&D is definitely needed, but with the limited international interest the gasification technology seems to have reached a dead end in Denmark.

Another focal point is the working environment, where care must be taken to limit any potential health hazards resulting from the handling of long-term stored biofuels.
Design Features of Gas Turbine Systems Applied to Floating Production Storage and Off-Loading (FPSO) Vessels
Authors: Waldhelm Chris , Baron Peter
Published: December 2014

Application of gas turbines in the off-shore oil and gas market has been successful for many years, utilizing both industrial gas turbines, as well as, aeroderivative types. Today, many operators in this market are pursuing the use of converted oil tankers and purpose-built barges — called Floating Production Storage and Off-Loading vessels (FPSO) — and semi-submersible or tension-leg platforms as alternative means of drilling for and production of oil and gas in much deeper waters than before, gaining flexibility of operation and reduced overall costs.

Due to the special requirements of extreme conditions experienced on board a FPSO vessel, each application involves a considerable amount of pre-design to determine the gas turbine package required capability to satisfy needed reliability. Additionally, international and local maritime regulatory bodies and classification societies concurrence/approval generally are required to authorize vessel operation. The intent of the “Code of Construction and Equipment of Offshore Drilling Units” is to recommend design criteria, construction standards, and other safety measures in order to minimize risk to the vessels, platforms, personnel and to the environment.

To incorporate these requirements into a standardized cost effective gas turbine system, this paper outlines the design features of such a package for installation on FPSO vessels.
A Combined Cycle Power Generation/Alfalfa Processing System: Part 1 — Development and Testing
Authors: Brushwood John S. , Campbell Ken , Hanson C. V. , Horvath Andras , Vivenzio Thomas
Published: December 2014

The Minnesota Valley Alfalfa Producers (MnVAP), a farmer owned cooperative, is developing a 75 MW combined cycle power plant integrated with alfalfa processiag facilities in southwestern Minnesota. The Minnesota Agri-Power (MAP) project is supported by the U. S. Department of Energy and a project development team that includes Stone & Webster, the University of Minnesota, United Power Association, Carbona Corporation/Kvaerner Pulping Inc. and Westinghouse. Alfalfa processing facilities separate the fibrous stem material from the protein-rich leaf fraction. The resulting alfalfa leaf meal (ALM) is further processed into a variety of valuable livestock feed products. Alfalfa stem material is gasified using air-blown fluidized bed technology to produce a hot, clean, fuel gas. The fuel gas is fired in a combustion turbine and the exhaust heat is used to produce steam to power a steam turbine. At base load, the electric power plant will consume 1000 tons per day of biomass fuel. This paper briefly describes the project development activities of the alfalfa feed trials and the combined cycle power plant. This commercial scale demonstration represents an important milestone on a continuing pathway towards environmentally and economically sustainable energy systems.
The Effect of Heat Exchanger Effectiveness and Exergy Loss in the Estimation of Cycle Efficiency
Authors: Horlock J. H.
Published: December 2014

The effect of heat exchanger effectiveness on cycle efficiency is well known. But the relationship between exergy loss in heat exchangers and the effectiveness is less well documented. In this paper the relationship is explored; it is shown how the exergy loss in the heat exchanger is changed as effectiveness is altered. It is also shown how the exergy losses in other components of the recuperative gas turbine cycle are changed, together with the overall cycle performance, as the effectiveness is varied.
Transient Analysis of a Small Gas Turbine to be Used in an Evaporative Cycle
Authors: Gustafsson Jan-Olof , von Heiroth Paul , Lindquist Torbjörn
Published: December 2014

Static process calculations done by various institutions have shown competitive thermal efficiencies for the evaporative cycle, also known as the HAT-cycle, when compared to the combined gas and steam cycle. The cycle seems also attractive from other standpoints such as lower investment costs and excellent part load performance. With this background several companies and organisations in Sweden have jointly started an evaporative gas turbine project.

The participating organisations agreed to design and erect a pilot plant at the Lund Institute of Technology. In co-operation with the Royal Institute of Technology in Stockholm various tests will be performed with the overall goal to verify efficiency improvements and functional performance. The test schedule started with the gas turbine in dry stand alone operation. From this initial phase the process will be developed, first step is the introduction of a recuperator. The final process includes a water circuit and condensing of water vapour in exhaust gases for recycling to the humidifier.

This paper presents a dynamic model of the gas turbine unit with and without the recuperator. Algebraic models are used for the gas turbine components combined with conservation equations in differential forms for volumes. The approximation used for volumes is the lumped parameter model meaning that properties within the volume are uniform. Heat flow between gas and solid structure is included in the recuperator model but is elsewhere neglected. A comparison between measurements and calculations is presented for the gas turbine without recuperator.
Fast CE™ — A Radical Approach to Concurrent Engineering
Authors: Barbeau Dennis E.
Published: December 2014

This paper describes the status and potential for a fast time-to-market concurrent engineering process. The principles have been developed by the author over a 25 year learning process and used effectively on a variety of programs. Fast CE™ is fundamentally predicated on integration of the manufacturing and engineering processes at the conceptual design phase. Commencement at this early date is critical — 80 to 90% of the inherent production unit cost is locked in place during this process. Subsequent to development of an integrated design strategy, both producibility and functional product development evolve in parallel using a “model-centric” approach to maintain the integrity of all elements of the program. Fast CE™ not only eliminates the use of drawings, it requires that they not be used in any capacity except as a convenience reference. This provides tight control over a common data base that directly links all of the activities necessary to design and produce a product. The result is a significant reduction in cost and schedule, with gains in all of the processes required to bring a product to market. Drawing elimination in itself can amount to a savings of as much as one third of the total design cost. The activities previously supported by drawings — quality assurance, for example — are managed through simpler, more functionally oriented processes.

The author describes the elements of Fast CE™ and the radical changes required in certain areas. Historical background traces development of the processes, providing perspective on the strategies and the issues faced and overcome, and leading to the issues currently faced in attainment of its full potential. The cost and schedule gains identified require cultural as well as operational changes. The more radical of these changes present a management challenge to any organization intent on gaining the full spectrum of benefits.
Affordable Nozzles Employing the Fixed Aperture Design Approach
Authors: Schuster Ernie , Smereczniak Phil , Luffy Ron , Scavo Steve
Published: December 2014

Fixed aperture (FA) nozzles offer the potential to significantly reduce the complexity and cost of afterburning turbine engine exhaust nozzles. This is accomplished by utilizing secondary air from an ejector system to control primary jet expansion at low nozzle pressure ratios and thereby eliminating the variable position divergent flaps and associated actuators, linkages, and hydraulics. The relatively cool ejector air flowing over the hot nozzle surfaces, combined with the gapless external airframe interfaces enabled by the fixed divergent section, offer the possibility for concurrent reductions in infrared and radar signatures. The installed aerodynamic performance of FA-based ejector nozzles has been analyzed with several engine cycles to explore these potential benefits.
Effects of Variable Inlet Guide Vane Settings on Axial Compressor Blade Vibration in an Industrial Gas Turbine
Authors: Blaswich Michael , Taylor Derek J.
Published: December 2014

This paper describes an experiment on a GHH BORSIG Type THM 1304-10 Gas Turbine engine to test the effects of variable vane setting on the vibration behaviour of the blades in all 10 stages of the axial compressor. The rotor was fitted with a network of strain-gauges. An analogue telemetry system was arranged using standard hardware and special application software to display in real-time and to log the full range of frequencies and amplitudes for all instrumented blades. The data acquisition system is described together with a presentation of the live display which allowed engineers to interact with measured results to maximise the benefits of the test whilst all strain-gauges were still functional. Tests were arranged to maximise the vibration data collected at all points before gauge mortality was experienced. Prior to the test, blades were vibrated statically to determine shapes of the first four vibration modes. The paper discusses the fixing techniques for the gauges, the modal shape measurement technique and the calibration of the strain-gauges. The telemetry system architecture and multiplexing arrangement are described together with examples of typical test data and the conclusions concerning the effects on blade vibration of different variable inlet guide vanes (IGV) settings.