bluuebunny/crossref_metadata_2025 huggingface dataset:
Internal Flow Structure of a Pressure-Swirl Atomizer at Two Different Density Ratios
Authors: Wang Dexin , Ma Zhanhua , Jeng San-Mou , Benjamin Michael A.
Published: August 2014

The flow fields of large-scale simplex nozzles were investigated by 2-D back-scattered Laser Doppler Velocimetry (LDV). The internal flow structures of a simplex nozzle at two different density ratios of the working fluid and the ambient medium were obtained. The effects of the density ratio, Reynolds Number and orifice geometry on the flow structure were examined. The results revealed that the density ratio only affects the internal flow field in the region where the radius is smaller than the orifice radius. The density ratio and Reynolds Number have stronger influence on the internal flow structure of a sudden contraction and 45° expansion orifice configuration than on that of a 45° contraction and sudden expansion orifice configuration. When the density ratio is one, the effect of the contraction geometry from swirl chamber to orifice on the internal flow is very small compared to the effect of the expansion geometry.
Evaluation of Advanced Two-Phase Flow and Combustion Models for Predicting Low Emission Combustors
Authors: Klose G. , Schmehl R. , Meier R. , Meier G. , Koch R. , Wittig S. , Hettel M. , Leuckel W. , Zarzalis N.
Published: August 2014

The development of low emission aero engine combustors strongly depends on the availability of accurate and efficient numerical models. The prediction of the interaction between two-phase flow and chemical combustion is one of the major objectives of the simulation of combustor flows.

In this paper, predictions of a swirl stabilized model combustor are compared to experimental data. The computational method is based on an Eulerian two-phase model in conjunction with an Eddy Dissipation (ED) and a presumed-shape-PDF (JPDF) combustion model.

The combination of an Eulerian two-phase model with a JPDF combustion model is a novelty. It was found to give good agreement to the experimental data.
Use of Chromium Containing Fuel Additive to Reduce High Temperature Corrosion of Hot Section Parts
Authors: Stalder Jean-Pierre , Huber Peter A.
Published: August 2014

The use of “clean” fuel is a prerequisite at today’s elevated gas turbine firing temperature, modern engines are more sensitive to high temperature corrosion if there are impurities present in the fuel and/or in the combustion air. It is a common belief that distillate grade fuels are contaminant-free, which is often not true. Frequently operators burning distillates ignore the fuel quality as a possible source of difficulties. This matter being also of concern in plants mainly operated on natural gas and where distillate fuel oil is the back-up fuel. Distillates may contain water, dirt and often trace metals such as sodium, vanadium and lead which can cause severe damages to the gas turbines. Sodium being very often introduced through contamination with seawater during the fuel storage and delivery chain to the plant, and in combination, or with air borne salt ingested by the combustion air. Excursions of sodium in treated crude or heavy fuel oil can occur during unnoticed malfunctions of the fuel treatment plant, when changing the heavy fuel provenience without centrifuge adjustment, or by inadequate fuel handling. For burning heavy fuel, treatment with oil-soluble magnesium fuel additive is state of the art to inhibit hot corrosion caused by vanadium. Air borne salts, sodium, potassium and lead contaminated distillates, gaseous fuels, washed and unwashed crude and residual oil can not be handled by simple magnesium based additives. The addition of elements like silicon and/or chromium is highly effective in reducing turbine blade hot corrosion and hot section fouling.

This paper describes field experience with the use of chromium containing fuel additive to reduce high temperature corrosion of hot section parts, as well as the interaction of oil-soluble chromium and magnesium-chromium additives on material behaviour of blades and vanes, and their economical and environmental aspects.
Numerical Simulation of Swirl-Stabilized Premixed Flames With a Turbulent Combustion Model Based on a Systematically Reduced 6-Step Reaction Mechanism
Authors: Bohn Dieter E. , Lepers Joachim
Published: August 2014

This paper presents the application of a detailed combustion model for turbulent premixed combustion to a swirl-stabilized premix burner. Computations are carried out for atmospheric pressure and elevated pressure of 9 atm. Results of computations for atmospheric pressure are compared to experimental data.

The combustion model is of the joint-pdf type. The model is based on the characteristics of turbulent combustion under conditions typical for gas turbine burners. It incorporates a systematically reduced 6-step reaction mechanism yielding direct computation of radical concentrations via transport equations or steady-state assumptions. The model is able to simulate combustion of fuel gases containing methane, carbon monoxide, hydrogen, carbon dioxide and water. It is therefore applicable to both methane and low-BTU fuel gas combustion.

Based on computed radical concentrations, a post-processor for NOx-formation is applied. This post-processor considers thermal formation of nitrogen oxides and NO-formation via the nitrous-oxide path.
Design Study of Helium Turbine for the 300MW HTGR-GT Power Plant
Authors: Muto Yasushi , Ishiyama Shintaro , Fukuyama Yoshitaka , Okumoto Junji , Kishibe Tadaharu , Yamada Seiya
Published: August 2014

This paper describes the design of a 300MW HTGR-GT power plant which was completed in the framework of the HTGR-GT feasibility study project. The project is assigned to JAERI by the Science and Technology Agency of Japan. The inlet and outlet gas temperatures in the reactor are 550°C and 900°C, respectively. Helium gas pressure is 6MPa. The turbine system is a recuperative intercooled direct cycle one. Designs of helium turbine, LP and HP compressors and generator are presented, whose adiabatic efficiencies are 93.09, 89.92 and 90.25%, respectively. A horizontal single-shaft configuration was adopted whose rotor dynamics is given.
Performance Assessment of Semi-Closed Chemically Recuperated Gas Turbine Systems
Authors: Cau Giorgio , Cocco Daniele
Published: August 2014

The paper is concerned with thermochemical recuperation in semi-closed gas turbine systems. Semi-closed turbines use CO2 as the main working fluid and the combustion process takes place with pure oxygen, allowing the CO2 produced to be easily removed. On the other hand, the exhaust heat recovery through thermochemical recuperation offers interesting capabilities in terms of high conversion efficiency and low polluting emissions.

System analysis and performance evaluation of the semi-closed, chemically recuperated gas turbine systems has been conducted and their performance assessed. A comparative analysis of semi-closed and open gas turbine cycles, with and without thermochemical recuperation, has been also carried out.

The results of the analysis show that thermochemical recuperation in semi-closed gas turbine systems can allow to remove the CO2 with high cycle efficiency and specific power.
Estimation of the Operating Characteristics of the Adjustable Speed Gas Turbine Power Generation System During Partial Load Operation
Authors: Nagafuchi Naoyuki , Kobayashi Nariyoshi , Utamura Motoaki
Published: August 2014

This paper proposes an application of the simple cycle adjustable speed gas turbine power generation system for use as an independent power producer combined with a heavy duty gas turbine (output power 25MW, turbine inlet temperature 1400K class) having adjustable speed generators. Comparison results for a method to improve the thermal efficiency of this system using low NOx combustors are obtained.

The results of a performance study of the static characteristics for the system using forced IGV (Inlet Guide Vane) opening control during partial load adjustable speed operation, show an effect on thermal efficiency improvement. Comparison of the dynamic characteristics for the system using existing controllers and the system using the proposed controllers shows, the latter is able to restrain fluctuation of the fuel to air mass ratio during a transient changing the target rotational speed, under restricted operating conditions.
Effects of Slot Bleed Injection Over a Contoured Endwall on Nozzle Guide Vane Cooling Performance: Part I — Flow Field Measurements
Authors: Burd Steven W. , Simon Terrence W.
Published: August 2014

Film cooling and secondary flows are major contributors to aerodynamic losses in turbine passages. This is particularly true in low aspect ratio nozzle guide vanes where secondary flows can occupy a large portion of the passage flow field. To reduce losses, advanced cooling concepts and secondary flow control techniques must be considered. To this end, combustor bleed cooling flows introduced through an inclined slot upstream of the airfoils in a nozzle passage were experimentally investigated. Testing was performed in a large-scale, high-pressure turbine nozzle cascade comprised of three airfoils between one contoured and one flat endwall. Flow was delivered to this cascade with high-level (∼9%), large-scale turbulence at a Reynolds number based on inlet velocity and true chord length of 350,000. Combustor bleed cooling flow was injected through the contoured endwall upstream of the contouring at bleed-to-core mass flow rate ratios ranging from 0 to 6%. Measurements with triple-sensor, hot-film anemometry characterize the flow field distributions within the cascade. Total and static pressure measurements document aerodynamic losses. The influences of bleed mass flow rate on flow field mean streamwise and cross-stream velocities, turbulence distributions, and aerodynamic losses are discussed. Secondary flow features are also described through these measurements. Notably, this study shows that combustor bleed cooling flow imposes no aerodynamic penalty. This is atypical of schemes where coolant is introduced within the passage for the purpose of endwall cooling. Also, instead of being adversely affected by secondary flows, this type of cooling is able to reduce secondary flow effects.
The Influence of the Boundary Layer State and Reynolds Number on Film Cooling and Heat Transfer on a Cooled Nozzle Guide Vane
Authors: Reiss Hans , Bölcs Albin
Published: August 2014

Film cooling and heat transfer measurements were carried out on a cooled nozzle guide vane in a linear cascade, using a transient liquid crystal technique. Three flow conditions were realized: the nominal operating condition of the vane with an exit Reynolds number of 1.47e6, as well as two lower flow conditions: Re2L = 1.0e6 and 7.5e5. The vane model was equipped with a single row of inclined round film cooling holes with compound angle orientation on the suction side. Blowing ratios ranging form 0.3 to 1.5 were covered, all using foreign gas injection (CO2) yielding an engine-representative density ratio of 1.6. Two distinct states of the incoming boundary layer onto the injection station were compared, an undisturbed laminar boundary layer as it forms naturally on the suction side, and a fully turbulent boundary layer which was triggered with a trip wire upstream of injection.

The aerodynamic flow field is characterized in terms of profile Mach number distribution, and the associated heat transfer coefficients around the uncooled airfoil are presented. Both detailed and spanwise averaged results of film cooling effectiveness and heat transfer coefficients are shown on the suction side, which indicate considerable influence of the state of the incoming boundary layer on the performance of a film cooling row. The influence of the mainstream flow condition on the film cooling behavior at constant blowing ratio is discussed for three chosen injection regimes.
Heat Transfer Measurements and Predictions on a Power Generation Gas Turbine Blade
Authors: Giel Paul W. , Bunker Ronald S. , Van Fossen G. James , Boyle Robert J.
Published: August 2014

Detailed heat transfer measurements and predictions are given for a power generation turbine rotor with 129 deg of nominal turning and an axial chord of 137 mm. Data were obtained for a set of four exit Reynolds numbers comprised of the design point of 628,000, −20%, +20%, and +40%. Three ideal exit pressure ratios were examined including the design point of 1:378, −10%, and +10%. Inlet incidence angles of 0 deg and ±2 deg were also examined. Measurements were made in a linear cascade with highly three-dimensional blade passage flows that resulted from the high flow turning and thick inlet boundary layers. Inlet turbulence was generated with a blown square bar grid. The purpose of the work is the extension of three-dimensional predictive modeling capability for airfoil external heat transfer to engine specific conditions including blade shape, Reynolds numbers, and Mach numbers. Data were obtained by a steady-state technique using a thin-foil heater wrapped around a low thermal conductivity blade. Surface temperatures were measured using calibrated liquid crystals. The results show the effects of strong secondary vortical flows, laminar-to-turbulent transition, and also show good detail in the stagnation region.
Analysis of Flow and Heat Transfer in the End-Wall Region of a Turbine Blade Passage
Authors: Xiao Yumin , Amano R. S.
Published: August 2014

A numerical study has been performed to predict a three-dimensional turbulent flow and end-wall heat transfer in a blade passage. The complex three-dimensional flow in the end-wall region has an important impact on the local heat transfer. The leading edge horseshoe vortex, the leading edge corner vortices, the passage vortex, and the trailing edge wake cause large variations in the entire end-wall region. The heat transfer distributions in the end-wall region are calculated and the mechanism for the high heat transfer region has been revealed. The calculations show that the algebraic turbulence model lacks the ability to predict the heat transfer in the transition region, but it is valid in other flow region. The local high heat transfer downstream of the trailing edge is enhanced by the wake downstream of the trailing edge. The horseshoe vortex results a high heat transfer region near the leading edge and induces the leading edge corner vortices which cause high heat transfer on the end-wall at both sides of blade end-wall corner.
Measurements in a Turbine Cascade Over a Contoured Endwall: Discrete Hole Injection of Bleed Flow
Authors: Oke Rohit A. , Simon Terrence W. , Burd Steven W. , Vahlberg Rickard
Published: August 2014

Thermal and flow field measurements taken within a cascade passage are presented. The cascade has two passages between three airfoils and two endwalls, one flat and one contoured. Measurements were done on and near the contoured endwall. The main objective is to document the effectiveness of cooling the contoured endwall with bleed flow that emerges through two rows of staggered, discrete holes on the contoured endwall, upstream of the airfoils. Similar studies have been performed in our lab with bleed flow emerging from slots upstream of the same contoured endwall. Both those and the present studies are with high free stream turbulence intensity, TI ∼ 9%, of the approach flow. This is characteristic of the approach flow to first stage vanes in most operating engines. In the experiments, the bleed flow is heated slightly above the main stream flow and downstream temperature fields are documented. Three bleed flow rates are tested. It is shown that at a lower flow rate (1.5% of the core flow) the cascade endwall cross-flow carries coolant towards the suction side. However, as the coolant rate is increased, the coolant attains sufficient momentum that no suction-side coolant migration is seen. Velocity measurements taken with triple-sensor, hot-wire anemometry document migration of the bleed flow by way of showing regions of stronger shear, and help describe mixing of the passage flow with the bleed flow. At higher coolant flow rates, strong blockage and mixing effects become evident.
Experimental Investigation on Impingement Heat Transfer From Rib Roughened Surface Within Arrays of Circular Jets: Correlation
Authors: Chang Haiping , Zhang Jingyu , Huang Taiping
Published: August 2014

Impingement heat transfer is one of the useful cooling methods for high temperature gas turbine blades and/or guide vanes in aeroengines. After the cooling jet impinges on the leading edge of the turbine blade and/or guide vane, it flows downstream and turns to be the initial crossflow for the aft row of impinging jet. The process of impingement heat transfer is quite complicated, especially when the target surface is rib roughened.

In this paper, the correlation of the impingement heat transfer characteristics has been analyzed based on thousands of experimental data in different parameter matching conditions (Ref = 7000∼20000, Gc/Gj = 0∼0.5, Xn = 5∼15, Zn = 1.5∼5, p/e = 5∼12 and e/d = 0.5∼1.5). The impingement heat transfer characteristics can be generally expressed as a functional formulation with the exponential functions of Ref, Zn, Xn, e/d and p/e, and a polynomial function of Gc/Gj. The interaction among the parameters are reflected in the exponents i, j, k, n, etc. and the weighing coefficients. By the regression processing to the experimental data, the exponents and the weighing coefficients are determined. The correlation equation of impingement heat transfer characteristics to the parameters has been finally concluded. Comparison shows that the correlation results are in good agreement with the experimental data.
Experimental Heat Transfer and Bulk Air Temperature Measurements for a Multipass Internal Cooling Model With Ribs and Bleed
Authors: Thurman Douglas , Poinsatte Philip
Published: August 2014

An experimental study was made to obtain heat transfer and air temperature data for a simple 3-leg serpentine test section that simulates a turbine blade internal cooling passage with trip strips and bleed holes. The objectives were to investigate the interaction of ribs and various bleed conditions on internal cooling and to gain a better understanding of bulk air temperature in an internal passage. Steady state heat transfer measurements were obtained using a transient technique with thermochromic liquid crystals. Trip strips were attached to one wall of the test section and were located either between or near the bleed holes. The bleed holes, used for film cooling, were metered to simulate the effect of external pressure on the turbine blade. Heat transfer enhancement was found to be greater for ribs near bleed holes compared to ribs between holes, and both configurations were affected slightly by bleed rates upstream. Air temperature measurements were taken at discreet locations along one leg of the model. Average bulk air temperatures were found to remain fairly constant along one leg of the model.
Influence of Injection Type and Feed Arrangement on Flow and Heat Transfer in an Injection Slot
Authors: Cho Hyung Hee , Ham Jin Ki
Published: August 2014

An experimental investigation is conducted to improve a slot film cooling system used for the cooling of a gas turbine combustor liner. The tangential slots are constructed of discrete holes with different injection types which are the parallel, vertical and combined to the slot lip. The investigation is focused on the coolant supply systems of normal-, inline-, and counter-flow paths to the mainstream flow direction. A naphthalene sublimation technique has been employed to measure the local heat/mass transfer coefficients in a slot wall with various injection types and coolant feeding directions. A numerical simulation is also conducted to help understand the flow patterns inside the slot for different injection types.

The velocity distributions at the exit of slot lip for the parallel and vertical injection types are fairly uniform with mild periodical patterns with respect to the injection hole positions. However, the combined injection type increases the nonuniformity of flow distribution with the period equaling twice that of hole-to-hole pitch due to splitting and merging of the ejected flows. The dimensionless temperature distributions at the slot exits differ little with blowing rates, injection types and secondary flow conditions.

In the results of heat/mass transfer measurements, the best cooling performance inside the slot is obtained with the vertical injection type among the three different injection types due to the effects of jet impingement. The lateral distributions of heat/mass transfer coefficients with the inline- and counter-flow paths are more uniform than the normal-flow path. The average heat/mass transfer coefficients with the injection holes are about 2∼5 times higher than that of a smooth two-dimensional slot path.
Effects of Showerhead Injection on Film Cooling Effectiveness for a Downstream Row of Holes
Authors: Polanka Marc D. , Ethridge Marcia I. , Cutbirth J. Michael , Bogard David G.
Published: August 2014

There have been numerous studies of film cooling performance for the downstream coolant holes on a turbine airfoil using test geometries ranging from flat plates to airfoils. Most of these studies simulate a relatively unperturbed boundary layer flow approaching the coolant holes. This stimulated the current inquiry into the effects of realistic upstream conditions for downstream coolant holes. To investigate this, a series of experiments were performed focussing on the first downstream row of holes on the pressure side of a typical turbine vane. The film cooling effectiveness for this pressure side row of holes was determined subject to no showerhead blowing, and to showerhead blowing with varying blowing rates. Furthermore, tests were conducted with low and high freestream turbulence levels. For this investigation, a leading edge showerhead array of six film cooling rows was utilized, with coolant from three of these rows being directed towards the pressure side of the vane. For all experiments a coolant to freestream density ratio of nominally DR = 1.8 was used. Adiabatic effectiveness was determined from surface temperature measurements for a nominally adiabatic surface using an infrared camera for spatially resolved mapping of the surface temperature. This study showed that showerhead injection had a dominant influence on the adiabatic effectiveness performance of downstream cooling. Showerhead injection appeared to cause a significant increase in coolant jet dispersion, presumably by increased levels of turbulence. Even when the freestream turbulence level at the pressure side coolant holes was increased to 17%, showerhead injection caused a significant degradation in the film cooling performance of the pressure side row of holes. Because of the increased dispersion caused by the showerhead injection for the pressure side coolant jets, the superposition model failed to correctly predict adiabatic effectiveness levels for combined showerhead and pressure side coolant injection.
Measurement of Local Heat Transfer Coefficient and Film Cooling Effectiveness Through Discrete Holes
Authors: Martinez-Botas R. F. , Yuen C. H. N.
Published: August 2014

An efficient steady-state wide band liquid crystal technique is used to study the film cooling performance of a variety of geometries in a flat plate: a single row of holes, a double row of holes (both in-line and staggered), and a single cooling hole. This method allows temperature information to be captured in one image, without the difficulty involved in a transient experiment. The streamwise inclinations tested are 30°, 60°, and 90°. The freestream is maintained at 13m/s, and at ambient temperature. The range of blowing ratios varied from 0.33 to 2.0. Both heat transfer coefficient and adiabatic cooling effectiveness are measured for all the cases. Air is used to produce a density ratio near unity.

From the range of blowing ratios tested, the most effective film cooling is achieved at a value close to 0.5, for near unity density ratio. It has been revealed that film cooling effectiveness is improved when the jet remains attached to the surface, however, this is generally coupled with an augmentation in heat transfer owing to the disturbance the attached jet causes to the boundary layer. The 30° inclined holes show to be the most effective. Results demonstrate the full coverage capability of liquid crystal thermography.
Heat Transfer Analysis in a Modern DLN Combustor
Authors: Ferrara Giovanni , Innocenti Luca , Migliorini Giacomo , Facchini Bruno , Dean Anthony J.
Published: August 2014

The increasingly stringent emissions standards in recent years have mandated low gas turbine emissions and thus changed the approach to combustion chamber design. In particular, lean burners based on highly premixed fuel-air flows have become more important. These combustors, termed Dry Low NOx (DLN), can now achieve emissions of 25 ppm and below in commercial operation.

This development together with the inlet turbine temperature increase has resulted in less cooling air for combustion chambers and turbine blade cooling systems. The designer now needs to optimise cooling air flows that control the wall temperature of the components that confine the hot gases. Moreover, much of the air coming from the compressor is used to premix the fuel and only a smaller fraction is now available for cooling processes. In annular combustor configurations the air available for cooling the combustion chamber walls sometimes also has to cool the first stage nozzle. So the pressure loss along the combustor cooling passages has to be limited in order to assure a suitable supply pressure for these downstream cooling passages.

We analysed the cooling air flow around the liner of an annular combustion chamber and we investigated the thermal flux and friction losses. In this paper we show the development of a calculation model that allows the critical components heat transfer analysis of a typical annular combustion chamber. The code developed is based on the generalised 1–D flow treatment. We have used experimental correlations for convection, film cooling and impingement borrowed from works found in literature. The code is provided with a graphical interface that helps the user during the calculation. This code was used in practical application to optimize the PGT5B combustion chamber cooling.
Flow Characteristics Inside Circular Injection Holes Normally Oriented to a Crossflow: Part I — Flow Visualizations and Flow Data in the Symmetry Plane
Authors: Lee Sang Woo , Park Sang Won , Lee Joon Sik
Published: August 2014

Experimental results are presented which describe flow behavior inside circular injection holes with a sharp square-edged inlet. Oil-film flow visualizations and mean flow data are obtained in the flow symmetry plane of injection holes which are normally oriented to a crossflow. Additional visualizations inside inclined holes are also performed for inclination angles of 30 and 60 degrees. Data are presented for three different length-to-diameter ratio values of L/D = 0.5, 1.0 and 2.0. The blowing ratio is fixed at M = 2.0 in the flow visualizations and takes the values M = 0.5, 1.0 and 2.0 in the flow measurements. The normal-injection flow visualization in the case of L/D = 2.0 clearly demonstrates the existence of four distinct near-wall flow regions: an inlet separation region, a reattachment region, a developing region, and a near-exit flow region. When L/D = 1.0 and 2.0, an inlet separation bubble is apparent with a clear imprint of recirculating flow traces especially on the windward side, even though it is not so well organized on the opposite side. For a short hole such as L/D = 0.5, however, the separation bubble with flow recirculation seems to be suppressed by the crossflow. Due to the presence of the inlet separation bubble, actual flow passage is in the form of a converging-diverging channel, regardless of the L/D values. In general, the crossflow stabilizes the inside flow on the leeward side, meanwhile destabilizes it on the windward side. On the contrary, the inclination of the injection hole in the leeward direction of the crossflow stabilizes the flow near the windward wall but destabilizes it near the leeward wall. Relatively short holes such as L/D = 0.5 and 1.0 do not allow the boundary-layer development on the wall. Particularly in the case of L/D = 0.5, a direct interference is observed between the complicated inlet and exit flows. The inlet flow, however, seems to be isolated from the exit flow for a long hole such as L/D = 2.0. It is also found that the potential-core inside the normal injection hole comprises a converging flow region, a diverging flow region, a developing flow region and a deflected flow region by the crossflow.
Turbine Separation Control Using Pulsed Vortex Generator Jets
Authors: Bons Jeffrey P. , Sondergaard Rolf , Rivir Richard B.
Published: August 2014

The application of pulsed vortex generator jets to control separation on the suction surface of a low pressure turbine blade is reported. Blade Reynolds numbers in the experimental, linear turbine cascade match those for high altitude aircraft engines and aft stages of industrial turbine engines with elevated turbine inlet temperatures. The vortex generator jets have a 30 degree pitch and a 90 degree skew to the freestream direction. Jet flow oscillations up to 100 Hz are produced using a high frequency solenoid feed valve. Results are compared to steady blowing at jet blowing ratios less than 4 and at two chordwise positions upstream of the nominal separation zone. Results show that pulsed vortex generator jets produce a bulk flow effect comparable to that of steady jets with an order of magnitude less massflow. Boundary layer traverses and blade static pressure distributions show that separation is almost completely eliminated with the application of unsteady blowing. Reductions of over 50% in the wake loss profile of the controlled blade were measured. Experimental evidence suggests that the mechanism for unsteady control lies in the starting and ending transitions of the pulsing cycle rather than the injected jet stream itself. Boundary layer spectra support this conclusion and highlight significant differences between the steady and unsteady control techniques. The pulsed vortex generator jets are effective at both chordwise injection locations tested (45% and 63% axial chord) covering a substantial portion of the blade suction surface. This insensitivity to injection location bodes well for practical application of pulsed VGJ control where the separation location may not be accurately known a priori.
A Study on Models to Simulate Boundary Layer Transition in Turbomachinery Flows
Authors: Müller M. , Gallus H. E. , Niehuis R.
Published: August 2014

The objective of this paper is to investigate the modeling of transition in turbomachinery flows. Under steady state conditions four modes of transition can be identified. One of them, reverse transition, can be modeled sufficiently well by turbulence models. For the other modes — natural, bypass and separated-flow transition — specific models have to be applied. These transition models are either based on stability analysis or a statistic approach that describes the production and growth of turbulent spots in the intermittent flow.

This paper focuses on separated flow transition. Different models are presented and a classification is attempted. Based on these findings specific models are chosen and implemented into a Navier-Stokes solver to be studied in more detail. First an annular compressor cascade is computed two-dimensionally and the results are compared with experiments. In a second step three-dimensional computations are performed and the effect of transition modeling is analysed.
Numerical and Experimental Investigation of Low Reynolds Number Effects on Laminar Flow Separation and Transition in a Cascade of Compressor Blades
Authors: Enomoto Shunji , Hah C. , Hobson G. V.
Published: August 2014

The results of an experimental and numerical comparison of the effects of low Reynolds number on flow separation and transition in a controlled-diffusion compressor cascade are presented. The flow separation and subsequent flow transition are associated with low Reynolds number effects in the compressor blade rows. Current steady-state Reynolds-averaged Navier-Stokes codes with available turbulence and transition models do not calculate the current flow phenomena properly. An unsteady three-dimensional Navier-Stokes calculation that applies a third-order accurate upwind method has been performed and the numerical results are compared to the measurements in detail. The results from the current numerical procedure agree very well with the measurements in terms of laminar flow separation, reattachment, and subsequent flow transition at low Reynolds numbers. The present study indicates that flow separation and flow transition inside compressor blade rows at low Reynolds number are phenomena dominated by relatively larger eddies near the wall and can be simulated with the current type of unsteady numerical procedure.
Gas Turbine Field Performance Determination: Sources of Uncertainties
Authors: Pinelli M. , Spina P. R.
Published: August 2014

This paper presents an analysis of the uncertainties in the determination of gas turbine health, which arise by using a method of Gas Path Analysis. This method uses field measurements to estimate, through a mathematical model of the gas turbine thermodynamic cycle, the characteristic geometric and performance parameters, which are indices of gas turbine health.

The investigated sources of uncertainties are the inaccuracy of measurements and the necessity of fixing a priori a number of characteristic parameters. This fact implies that variations occurring on these parameters in the actual gas turbine cause an estimation error on the characteristic parameters used as problem variables.

The analysis leads to the selection of the appropriate measurements to be used in the gas turbine health determination and identification of both the most critical measurements and parameters.
The Design and Implementation of a PLC Based Gas Turbine Controller for a Shipboard Application
Authors: Tolotta Vincent P.
Published: August 2014

A paper will be presented describing the design and development of the Gas Turbine Local Controller replacement used on the Magnetic Minesweeping Gas Turbine Generator (MMGTG) on the US Navy MCM-1 Class of ships. The advent of processor based controllers including PLCs has provided a low cost alternative for control system upgrades when faced with increasing maintenance costs and obsolescence issues of analog and hard relay logic control systems. The replacement controller is a Programmable Logic Controller (PLC) based system linked to a flat panel display and a supervisory control system.

A MMGTG during pulsing operations applies a severe load transient cycle to the gas turbine for the fuel control to meet in a stable and safe manner. The algorithms which employ an adaptive Proportional Integral Derivative (PID) loop control structure with internal limiting constraints based on engine state are used to manage these transients, power turbine entry temperature and a wide range of steady state operation. The controller includes logic for alarming, start/stop and automatic shutdown. The design of the hardwired automatic shutdown logic integrated to the PLC will be presented.

The control system design will be described in terms of its integration to a supervisory network, local control functionality and shipboard considerations. The Human Machine Interface screens of the flat panel display and their design are also considered.
Gas Turbine Control System Integration for Royal Caribbean Millennium Class Cruise Liner
Authors: Olsheski David J. , Schulke William W.
Published: August 2014

Traditionally commercial marine propulsion needs have been met with direct drive reciprocating prime movers. In order to increase efficiency, simplify installation and maintenance accessibility, and increase cargo / passenger capacity; indirect electric drive gas and steam turbine combined cycle prime movers are being introduced to marine propulsion systems. One such application is the Royal Caribbean Cruise Line (RCCL) Millennium Class ship. This commercial vessel has two aero-derivative gas turbine generator sets with a single waste heat recovery steam turbine generator set. Each is controlled by independent microprocessor based digital control systems. This paper addresses only the gas turbine control system architecture and the unique safety and dynamic features that are integrated into the control system for this application.
Italian Navy Evaluation Concerning the Use of Electronic Fuel Control and Hydraulic Starters for Fiat - GE LM2500 Gas Turbine
Authors: Maggini Massimo , Giuliano Michele
Published: August 2014

The LM2500 gas turbine has been used on Italian Navy (ITN) ships for more than twenty years. The first engines were installed onboard the “Lupo” class Frigates during the second half of the 1970’s.

These gas turbines are operated by means of a Hydro-Mechanical Fuel Control (HMFC) system and started by a pneumatic starter. However, it is known that in some of the latest applications of the LM2500 gas turbines, (e.g. direct drive and water jet systems - Military Sealift Command LMSR cargo vessels and Tirrenia Ferries), electronic fuel control systems and hydraulic starters are used to improve the control and maintenance of the engine, and to reduce the number of air bottles and compressors that have to be installed.

The ITN is now evaluating the convenience of using the electronic fuel control systems and hydraulic starters in future surface combatant applications (cruisers, destroyers & frigates) of FIAT GE LM2500 gas turbines.

This paper describes the comparison between the different systems that have been carried out by the ITN in the following fields: operations, maintenance and cost effectiveness.
The Effect of Primary Axis and Low Angle Boundary Misorientation on CMSX-10K Mechanical Properties
Authors: Patel Yakin , Browning Paul F. , Fitzpatrick Michael D. , Schmiedechnekt Dean , Price Allen , Simpson Tammy , Erickson Gary , Harris Ken
Published: August 2014

The U. S. Department of Energy’s Advanced Turbine Systems (ATS) program supports the development of high efficiency gas turbines for industrial and power generation applications. As part of this program, CMSX-10K, a third generation single crystal Ni-base superalloy, is being considered for use in turbine blade applications in an ATS engine. In support of the design and casting process development of CMSX-10K, assessment of component tolerance to casting defects was performed.

Single crystal specimens with primary axis orientation between 4 and 26 degrees and bicrystal specimens with low angle boundaries (LABs) having between 0 and 18 degrees of misorientation were used. The effects of primary axis misorientation and LABs on critical mechanical properties were evaluated. Primary axis misorientation of greater than 15 degrees reduced tensile and high-cycle fatigue properties. Similarly, stress rupture properties were reduced for primary axis misorientation of greater than 20 degrees. LABs having greater than 10 degrees of misorientation caused significantly reduced stress rupture life. LABs having greater than 12 degrees of misorientation also resulted in reduced tensile and high-cycle fatigue properties.
Advanced Oil Debris Monitoring for Pipeline Mechanical Drive Gas Turbines
Authors: Kitaljevich Duka , van Veldhuizen Gerrit J.
Published: August 2014

Gas turbines are a critical component of many pipeline operations. Gas turbine component failures are very costly both in terms of unit down time as well as repair. These costs are significantly amplified in situations where the outage is unplanned and component failure causes secondary damage. This statement is particularly relevant for rotor bearing failures, which can rapidly lead to heavy damage to the turbomachinery components if not detected in time. This paper describes a new advanced technology online device, which is designed to monitor the lubrication oil system of the engine and detect the presence of metallic debris in real time. These particles are present in the oil only when there is damage occurring in the engine bearings or gear train. This monitor has recently been applied to engines in the pipeline, power generation, marine propulsion and aviation industries worldwide and has been proven to provide early warning of bearing failure allowing for repair during scheduled outages and before causing expensive secondary damage to the engine.
Microphone Probe for In-Duct Measurement of Gas Turbine Exhaust Noise
Authors: Sacks M. P. , Kawall J. G. , Behboudi R. , Buttell J.
Published: August 2014

A new probe has been developed for Bruel & Kjaer 6.35 mm (1/4″) microphones in order to allow in-duct measurements in high temperature gas turbine exhaust ducts without exposing the microphone to excessive temperatures. The motivation for this design was the need for a probe system that is easily transported and installed on site.

The new probe is made from readily available 6.35 mm (1/4″) o.d. tubing and compression fittings. It consists of a stem to sample the in-duct acoustic field, a shut off valve, a “T” connector to provide a microphone port remote from the hot gas and an anechoic termination.

The termination provides a true anechoic response down to 20 Hz. The probe provides a smooth, resonant free response between 20 Hz and 20 kHz allowing for accurate calibration and measurement.

This paper describes the probe design and installation details, probe frequency response calibration, probe flanking limit and performance of the anechoic termination. The paper also compares the probe response to theoretical predictions. Relative to other potential in-duct measurement probe systems the new design is seen to be lightweight, compact and inexpensive.
A Demonstration of Artificial Neural Networks Based Data Mining for Gas Turbine Driven Compressor Stations
Authors: Botros K. K. , Kibrya G. , Glover A.
Published: August 2014

This paper presents a successful demonstration of application of Neural networks to perform various data mining functions on an RB211 gas turbine driven compressor station. Radial Basis Function networks were optimized and were capable of performing the following functions: a) Backup of critical parameters, b) Detection of sensor faults, c) Prediction of complete engine operating health with few variables, and d) Estimation of parameters that cannot be measured. A Kohonen SOM technique has also been applied to recognize the correctness and validity of any data once the network is trained on a good set of data. This was achieved by examining the activation levels of the winning unit on the output layer of the network. Additionally, it would also be possible to determine the suspicious, faulty or corrupted parameter(s) in the cases which are not recognized by the network by simply examining the activation levels of the input neurons.
Three Practical Examples of Magnetic Bearing Control Design Using a Modern Tool
Authors: Spirig M. , Schmied J. , Jenckel P. , Kanne U.
Published: August 2014

The use of magnetic bearing in industrial applications has increased due to their unique properties. Nowadays efficiency and predictability in handling rotors on magnetic bearings is asked with the same standard as conventional rotors on oil or roller bearings.

First of all one must be aware of the special technical properties of magnetic bearing designs. The dynamic behaviour of the rotor combined with requirements of the application define the desired bearing characteristic. With modern tools /1/, covering the mechanical aspects as well as the electronic controllers and their digital implementation on a DSP, these properties can be designed.

However, despite the use of such efficient tools engineering practice is needed. Therefore this paper summarises the major steps in the control design process of industrial applications. Three rotors supported on magnetic bearing with their specific dynamic behaviour are presented:

• A very small high speed spindle (120000 rpm),

• a small, industrial turbo molecular pump rotor (36000 rpm) and

• a large multi-stage centrifugal compressor (600 to 6300 rpm).

The results of the analyses and their experimental verification are given.
Comparison of Soft Magnetic Alloys for High Temperature Magnetic Bearings
Authors: Kondoleon Anthony S. , Kelleher William P.
Published: August 2014

Magnetic bearings are a prime technology that will lead the next generation of gas turbines into the 21st century. Before magnetic bearings can be utilized, fundamental properties of materials used to fabricate these components must be known at the intended operating temperatures and stress levels found in gas turbine applications. This paper presents results of recent work carried out on the development of a radial magnetic bearing for a high temperature gas turbine application. Mechanical and magnetic data on proposed soft magnetic materials intended for use in the magnetic bearing design are presented at both room and operating temperature (550C). The effect which long-term exposure to high temperature has on these properties is included. The use of this data for the development of the radial bearing is explained along with the proposed design of a magnetic bearing.
The Effect of Slot Length on Flux Distribution and Rotordynamic Coefficients in Magnetic Actuators Using a Boundary Perturbation Method
Authors: Stephens Lyndon S. , Casemore Mark A.
Published: August 2014

In previous work (Stephens and Casemore, 1999), the authors presented an analytical method to compute the flux distribution and negative stiffness of magnetic actuators. The method uses Fourier series expansions to model current distributions and permanent magnets as sources of magnetomotive force (MMF) on the air gap boundary and then solves the Dirichlet boundary value problem (BVP) in the eccentric annulus for the MMF within the permanent magnet and air gap regions. The method is applicable to many common magnetic actuator designs but is limited to those with MMF sources that are located opposite of a smooth (unslotted) boundary. In this paper, the method is extended to remove this limitation and include the effect of slot length on flux distribution and rotordynamic coefficients. This is accomplished by adding a boundary perturbation step to the solution that accounts for the additional reluctance of the slots. The method is applied to a sample problem and is benchmarked against a finite element model. The results show good agreement between the two models up to a certain critical slot length. This critical slot length is shown to correspond to the traditional infinite slot length (that slot length beyond which no appreciable change in flux distribution occurs). The results indicate that slots in the stator have a significant impact on the negative stiffness and that the infinite slot length assumption is valid even for shallow and wide slots.
Control of Surge for Centrifugal Compression System by Using a Bouncing Ball
Authors: Mizuki Shimpei , Tsujita Hoshio , Hishinuma Yumin
Published: August 2014

An experimental study for the control of surge in a centrifugal compression system by using a bouncing ball was tried. The bouncing ball was placed on a hole outside of the upper wall of a plenum installed to a delivery of a compressor. The hole was surrounded by a tube and had the conical slope toward the hole. When surge occurred, the ball bounced by the fluctuating pressure force in an irregular manner.

By the irregular fluctuation of the bouncing ball, the frequency of surge was suppressed. The peak in the spectrum caused by surge disappeared. Thus, the simple method to control surge by using the bouncing ball was shown to be effective.