bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and Turbine Engine Performance of Three Advanced Rhenium Containing Superalloys for Single Crystal and Directionally Solidified Blades and Vanes
Authors: Broomfield Robert W. , Ford David A. , Bhangu Harry K. , Thomas Malcolm C. , Frasier Donald J. , Burkholder Phil S. , Harris Ken , Erickson Gary L. , Wahl Jacqueline B.
Published: December 2014

Turbine inlet temperatures over the next few years will approach 1650°C (3000°F) at maximum power for the latest large commercial turbo fan engines, resulting in high fuel efficiency and thrust levels approaching 445 kN (100,000 lbs). High reliability and durability must be intrinsically designed into these turbine engines to meet operating economic targets and ETOPS certification requirements.

This level of performance has been brought about by a combination of advances in air cooling for turbine blades and vanes, design technology for stresses and airflow, single crystal and directionally solidified casting process improvements and the development and use of rhenium (Re) containing high γ′ volume fraction nickel-base superalloys with advanced coatings, including full-airfoil ceramic thermal barrier coatings. Re additions to cast airfoil superalloys not only improve creep and thermo-mechanical fatigue strength but also environmental properties, including coating performance. Re dramatically slows down diffusion in these alloys at high operating temperatures.

A team approach has been used to develop a family of two nickel-base single crystal alloys (CMSX-4® containing 3% Re and CMSX®−10 containing 6% Re) and a directionally solidified, columnar grain nickel-base alloy (CM 186 LC® containing 3% Re) for a variety of turbine engine applications. A range of critical properties of these alloys is reviewed in relation to turbine component engineering performance through engine certification testing and service experience.

Industrial turbines are now commencing to use this aero developed turbine technology in both small and large frame units in addition to aero-derivative industrial engines. These applications are demanding, with high reliability required for turbine airfoils out to 25,000 hours, with perhaps greater than 50% of the time spent at maximum power. Combined cycle efficiencies of large frame industrial engines is scheduled to reach 60% in the U.S. ATS programme. Application experience to a total 1.3 million engine hours and 28,000 hours individual blade set service for CMSX-4 first stage turbine blades is reviewed for a small frame industrial engine.
Experience in Applying the New UK Procedure for Creep Rupture Data Assessment to Gas Turbine Materials
Authors: Bullough Chris K.
Published: December 2014

A new procedure being developed in British Standards for the assessment of creep-rupture data is described, and evaluated with trial data sets of gas turbine blading materials. The procedure is applied in phases. An important development by statistical experts is a framework for the main assessment phase which uses maximum-likelihood fitting methods for the treatment of unfailed test points and error variance. The framework selects models from a standard suite (together with any other linear models supplied by the assessor) using statistical criteria, but also incorporates metallurgical judgement. The improved representation of the experimental data compared with previous fitting methods, and the associated statistical tests indicate that the new procedure can be used to derive rupture strength values for gas turbine materials with confidence.
Aero-Thermal Performance Measurements and Analysis of a Two-Dimensional High Turning Rotor Blade
Authors: Arts T. , Duboue J.-M. , Rollin G.
Published: December 2014

The purpose of this contribution is to report on the aerothermal performance measurements and calculations carried out around a high pressure gas turbine rotor blade profile mounted in a two-dimensional linear cascade arrangement. The measurements were performed in the CT-2 facility of the von Karman Institute, allowing a correct simulation of the operating conditions encountered in modern aero-engines. Independent variations of exit Mach (0.8 … 1.3) and Reynolds numbers (5 105 … 2 106), free stream turbulence (1 … 6 %) and incidence angle (−14 … +11 deg) provided the definition of a detailed data base of test results. The measured quantities were the blade velocity and convective heat transfer coefficient distributions. The first objective of the paper is to open and analyze this data base which is one of those used at SNECMA for validation purposes. The paper shows the degree of maturity and reliability SNECMA-ONERA Navier-Stokes solvers have now reached for daily use in turbine airfoil design and analysis.
Effects of a Wake on Turbine Blade Heat Transfer in a Transonic Cascade
Authors: Hale James H. , Diller Thomas E. , Ng Wing F.
Published: December 2014

The effects of a wake generated by a stationary upstream strut on surface beat transfer to turbine blades were measured experimentally in a heated, transonic cascade tunnel. Five pitchwise locations of the upstream strut were tested, while maintaining a constant axial distance between the strut and the leading edge plane of the cascade. Time-resolved unsteady heat flux measurements were made with Heat Flux Microsensors (HFM) at three positions on the suction surface and one position on the pressure surface. In addition, hot-wire surveys were taken along the leading edge plane of the cascade to document the disturbance generated by the upstream strut. Results from the hot-wire surveys show that with the strut placed upstream and near the stagnation point of the turbine blade, the turbulence intensity in the wake was as high as 50%. This high level of turbulence intensity was due to the coupling of the strut wake with the potential flow around the blunt leading edge of the turbine blade. A strong influence on the heat transfer coefficient was seen from the relative pitchwise position of the strut with respect to the leading edge of the test blades. For the suction surface, the maximum increase in average heat transfer coefficient occurred when the upstream strut was placed near the stagnation point of the blade. The heat transfer coefficients were increased by 15, 20, and 10% for the gages located on 10, 22, and 50% chord positions of the suction surface, respectively, compared to the baseline case of no strut. For the pressure side, results show the maximum increase in heat transfer coefficient occurred when the upstream strut was placed along the pitchline near the middle of the blade passage. At 30% chord position on the pressure surface, the heat transfer coefficient was increased by 25 %. Attempts to correlate these increases in mean heat transfer with integral values of the measured unsteadiness of the flow or heat flux were not successful.
Effect of Discrete Surface Disturbances on Vane External Heat Transfer
Authors: Bunker R. S.
Published: December 2014

A transonic linear vane cascade has been utilized to assess the effects of localized surface disturbances on airfoil external heat transfer coefficient distributions, such as those which may be created by the spallation of thermal barrier coatings. The cascade operates at an overall pressure ratio of 1.86, with an inlet total pressure of about 5 atm. Cascade Reynolds numbers based on axial chord length and exit velocity range from 2.2 to 4.8 · 106. Surface disturbances are modeled with the use of narrow trip strips glued onto the surface at selected locations, such that sharp forward facing steps are presented to the boundary layer. Surface locations investigated include the near leading edge region on either side of the stagnation point, the midchord region of the pressure side, and the high curvature region of the suction side. Heat transfer enhancement factors are obtained for disturbances with engine representative height-to-momentum thickness ratios, as a function of Reynolds number. Enhancement factors are compared for both smooth and rough airfoil surfaces with added disturbances, as well as low and high freestream turbulence intensity. Results show that leading edge heat transfer is dominated by freestream turbulence intensity effects, such that enhancements of nearly 50% at low turbulence levels are reduced to about 10% at elevated turbulence levels. Both pressure and suction side enhancement factors are dominated by surface roughness caused effects, with large enhancements for smooth surfaces being drastically reduced for roughened surfaces.
Flow in a Corotation Radial Inflow Cavity Between Turbine Disk and Coverplate
Authors: Liu X.
Published: December 2014

In order to guide the design of the engine air system, a comprehensive CFD analysis has been carried out on the flow in a corotation radial inflow cavity between the turbine disk and the coverplate of a gas turbine engine. Nine different flow cases have been studied. The rotational Reynolds number ranges from 0.79×106 to 3.14×106, and the through flow number ranges from 7×103 to 194×103, which covers the whole envelope of engine operating conditions. The CFD results revealed the complicated source-sink flow physics, and provided detailed variation of pressure, temperature, swirl factor and moment coefficient, etc., which serve as the basis for engine air system modelling. It has been shown that the flow behaves more and more like a free vortex with increasing mass flow, but more and more like a forced vortex with increasing rotational speed. For a good engine air system design, it is preferred to introduce the air into the cavity in such a way that the inlet swirl factor is independent of the mass flow.
Real-Time Fault Identification for Developmental Turbine Engine Testing
Authors: Malloy Donald J. , Chappell Mark A. , Biegl Csaba
Published: December 2014

Hundreds of individual sensors produce an enormous amount of data during developmental turbine engine testing. The challenge is to ensure the validity of the data and to identify data and engine anomalies in a timely manner. An automated data validation, engine condition monitoring, and fault identification process that emulates typical engineering techniques has been developed for developmental engine testing.

An automated data validation and fault identification approach employing engine cycle-matching principles is described. Engine cycle-matching is automated by using an adaptive nonlinear component-level computer model capable of simulating both steady-state and transient engine operation. An automated model calibration process is also described. The model enables automation of traditional data validation, engine condition monitoring, and fault identification procedures. A distributed parallel computing approach enables the entire process to operate in realtime.

The result is a capability to detect data and engine anomalies in realtime during developmental engine testing. The approach is shown to be successful in detecting and identifying sensor anomalies as they occur and distinguishing these anomalies from variations in component and overall engine aerothermodynamic performance.
Thermal Stability of High Temperature Fuels
Authors: Edwards Tim , Atria Joseph V.
Published: December 2014

This paper describes recent results of AF-sponsored research in the thermal stability of high temperature fuels. At temperatures of 550 °C (1000 °F) and above, both thermal -oxidative and pyrolytic deposition are important. A brief discussion of deposition characteristics and mitigation measures is presented.
Combustor Development for 1 MW Industrial Gas Turbine Engine
Authors: Kim Jay-Chul
Published: December 2014

This paper describes major results of combustor envelopment activities conducted under 1 MW industrial engine (Turbo Green 1200) program at Samsung Aerospace. The program was initiated in 1992 partially supported by Korean government. The main application of the industrial engine is a standby duty unit with a future derivative engine considered for a cogeneration unit. During the engine development, various tests of the engine and its components were carried out to confirm the performance target or the engine. This paper concentrates on the component test activities of the combustion section.
Low NOx Combustor Research for a Mach 3 Turbojet Concept Validation Test Results
Authors: Kinoshita Y. , Oda T. , Kitajima J.
Published: December 2014

A unique idea of premixture jet swirl combustor (PJSC) was proposed for the ultra low NOx combustor of a Mach 3 turbojet. The combustor installed six simple premixing chambers which were arranged at certain angles to the center axis also to the circumference axis on the combustor dome. This arrangement formed large and strong recirculating flows necessary to stabilize flame at lean fuel air ratio conditions. The fuel mixing study revealed that the radial fuel injectors inserted in a premixing chamber exhibited a high degree of uniformity. Single can combustors of PJSC with three types of main fuel injectors were manufactured for the high temperature and high pressure combustion test program. All combustors performed stable combustion for a wide range of FAR and obtained combustion efficiency of 99.9 % at Mach 3 cruise conditions, namely inlet temperature of 1008 K, inlet pressure of 830 kPa and fuel air ratio of 0.0223. HTHPC-01 combustor, which installed the radial fuel injectors and had long mixing length, presented the best NOx emissions and achieved emission index of 2 g/kg fuel at that design condition. PJSC met the emission goal of HYPR project, and concept validation test was completed in success.
Effect of Unsteady Wake on Detailed Heat Transfer Coefficient and Film Effectiveness Distributions for a Gas Turbine Blade
Authors: Du Hui , Han Je-Chin , Ekkad Srinath V.
Published: December 2014

Unsteady wake effects on detailed heat transfer coefficient and film cooling effectiveness distributions from a gas turbine blade with film cooling are obtained using a transient liquid crystal technique. Tests were performed on a five-blade linear cascade at a axial chord Reynolds number of 5.3 × 105 at cascade exit. Upstream unsteady wakes are simulated using a spoke-wheel type wake generator. The test blade has three rows of film holes on the leading edge and two rows each on the pressure and suction surfaces. Air and CO2 were used as coolants to simulate different coolant-to-mainstream density ratio effect. Coolant blowing ratio for air injection is varied from 0.8 to 1.2 and is varied from 0.4 to 1.2 for CO2. Results show that Nusselt numbers for a film-cooled blade are much higher compared to a blade without film injection. Particularly, film injection causes earlier boundary layer transition on the suction surface. Unsteady wakes slightly enhance Nusselt numbers but significantly reduce film cooling effectiveness on a film-cooled blade compared with a film-cooled blade without wakes. Nusselt numbers increase slightly but film cooling effectiveness increases significantly with an increase in blowing ratio for CO2 injection. Higher density coolant (CO2) provides higher effectiveness at higher blowing ratios (M = 1.2) whereas lower density coolant (Air) provides higher effectiveness at lower blowing ratios (M = 0.8).
WR21 Water Wash Development Approach for the Intercooled Recuperated (ICR) Gas Turbine Engine
Authors: Janton Jay T. , Widdows Kevin
Published: December 2014

The WR21 Intercooled Recuperated (ICR) Gas Turbine Engine is being developed as the prime power plant for future US and Foreign Navy ship applications. The development test program started in July 1994 and is still ongoing. One of the many challenges of the ICR design is the development of the compressors and intercooler (IC) wash system. The integration of the IC between the intermediate pressure compressor (IPC) and high pressure compressor (HPC) is unique to current US Navy applications and has introduced new design considerations from traditional wash development programs that must be addressed. Significant increase in wetted surface area of the heat exchanger (HX) matrix and the radial flow are two design aspects unique to the WR21.

This paper reviews the design of the WR21 engine and the challenges it offers to developing both crank and on-line compressor/IC wash systems. The baseline design of the water wash systems are discussed, in addition to the water wash test program and its integration into the overall WR2I development program. Details are also given of the off-engine wash delivery system and salt injection systems in place at the test site. Crank wash test results to date are also presented.
Economically Optimized Loading of a Combined Heat and Power Facility
Authors: Griffin Patrick R. , Elmasri Maher
Published: December 2014

An optimizing software system was developed to predict technically feasible, economically optimum operating points for a multi-faceted combined heat and power facility. The software combines detailed technical performance with a flexible purchase and sale model to predict equipment load levels that optimize net plant revenue subject to operational constraints. The optimization technique is iterative and relies on successive linear approximation of the true nonlinear behavior of the plant. Detailed production capability of each plant component is pre-simulated over the entire range of operation using a widely-accepted, commercially-available simulation package. Pre-simulated results are stored in look-up tables for fast evaluation during optimization calculations. Sensitivity of predicted optimum load point is analyzed using further constrained optimization runs. This paper provides description of the optimization technique, its implementation, and numerical sensitivity analysis, as well as insightful example cases.
Dynamic Behavior of Geared Rotors
Authors: Shiau T. N. , Rao J. S. , Chang J. R. , Choi Siu-Tong
Published: December 2014

This paper is concerned with the dynamic behavior of geared rotor systems supported by squeeze film dampers, wherein coupled bending torsion vibrations occur. Considering the imbalance forces and gravity, it is shown that geared rotors exhibit chaotic behavior due to non linearity of damper forces. The route to chaos in such systems is established. In geared rotor systems, it is shown that torsional excitation can induce lateral vibrations. It is shown that squeeze film dampers can suppress large amplitudes of whirl arising out of torsional excitation.
Viscous Flow Field Computations for a Transonic Axial-Flow Compressor Blade Using Different Turbulence Models
Authors: Lenke L. J. , Simon H.
Published: December 2014

New blading concepts as used in modern transonic axial-flow compressors require improved calculation methods. Here the turbulence modelling has great influence. Therefore a quasi-three-dimensional compressor blade with subsonic inlet conditions is calculated using different turbulence models. A low-Reynolds number k-ϵ, the k-ω model and an explicit algebraic Reynolds stress model are considered in this investigation.

The results from these calculations in form of comparisons between the predicted isentropic Mach number distributions, profile losses and exit flow angles with experimental data are presented in this paper. They demonstrate the differences between the models in the prediction of the separation behavior of blade surface boundary layer especially which are introduced by shocks. For the high inlet Mach numbers the models differ also in the prediction of losses and deviation angles at design and off-design conditions.
A Review of Analysis Techniques for Blade Tip-Timing Measurements
Authors: Heath S. , Imregun M.
Published: December 2014

This paper aims at evaluating the performance of the analysis methods currently used for the interpretation of vibration data measured at turbomachinery rotor blade tips using optical laser probes. The methods are classified by the form of the vibration which they can identify, namely asynchronous and synchronous with respect to rotor speed. Both actual assembly measurements and simulated response data are used during the investigation. In the latter case, synchronous vibration data are obtained via a multi-degree-of-freedom numerical simulator, which includes the structural and geometric properties of the bladed-disk assembly, the external forcing terms and the characteristics of the optical probe. The results of the tip timing analysis are compared to those obtained from standard strain-gauge tests and the relative merits of the two approaches are discussed with emphasis on the effects of blade mistuning. Existing industry-standard tip-timing analysis techniques are found to exhibit a number of inherent limitations and suggestions were made to address these deficiencies. A detailed tip-timing case study for a steam turbine rotor is presented in some detail and other potential application areas are explored. Finally, future analysis methods and possible future developments in tip-timing systems are discussed.
Simultaneous Hot Desulfurization and Improved Filtration in Coal Utilization Processes Using Waste Material
Authors: Patel Parul C. , Zievers James F. , Eggerstedt Paul M. , Zievers Elizabeth C.
Published: December 2014

Ceramic candle filtration is one of the few technologies for high temperature particulate removal which can meet both gas turbine manufacturer’s inlet particulate requirements and U.S. Clean Air Act requirements. Similarly, advances made in sorbent technology, especially metal oxide sorbents, have resulted in effective sulfur emissions mitigation. Current use of metal oxide sorbents, however, has focused on, regenerable formulations which have excellent sulfur affinity but high physical attrition, resulting in poor overall economics.

This paper suggests the use of spent metal oxide and calcium based materials for use in sulfur removal as an alternative to regenerable metal oxide sorbents. It becomes even more attractive when used in combination with ceramic candle filtration technology. When such sorbents are classified to a desired particle size and injected into a high temperature coal utilization process, such a “once-through” sorbent can effectively remove sulfur and simultaneously increase the permeability of dust collected at a downstream ceramic filter station, in a highly cost effective manner.
Aspects of Jet Fuel Oxidation
Authors: Zabarnick Steven , Whitacre Shawn D.
Published: December 2014

A quartz crystal microbalance (QCM)/Parr bomb system with a headspace oxygen sensor is used to measure oxidation and deposition during thermal oxidative stressing of jet fuel. The advantages of the oxygen sensor technique in monitoring fuel oxidation is demonstrated. Simultaneous measurement of deposition using the QCM shows a strong correlation between oxidation and deposition in jet fuels. Studies performed over the temperature range 140 to 180°C show that surface deposition peaks at an intermediate temperature, while bulk deposition increases with temperature, in studies of jet fuel antioxidants, we find that rapid increases in oxidation rate occur upon consumption of the antioxidant. The antioxidant appears to be consumed by reaction with alkylperoxy radicals. In studies of metal deactivator (MDA) additives, we find that MDA is consumed during thermal stressing, and this consumption results in large increases in the oxidation rate of metal containing fuels. Mechanisms of MDA consumption are hypothesized.
Comparison of Predicted and Experimental Heat Transfer on a Film-Cooled Rotating Blade Using a Two-Equation Turbulence Model
Authors: Garg Vijay K.
Published: December 2014

A three-dimensional Navier-Stokes code has been used to compare the heat transfer coefficient on a film-cooled, rotating turbine blade. The blade chosen is the ACE rotor with five rows containing 93 film cooling holes covering the entire span. This is the only film-cooled rotating blade over which experimental data is available for comparison. Over 2.278 million grid points are used to compute the flow over the blade including the tip clearance region, using Coakley’s q-ω turbulence model. Results are also compared with those obtained by Garg and Abhari (1996) using the zero-equation Baldwin-Lomax (B-L) model. A reasonably good comparison with the experimental data is obtained on the suction surface for both the turbulence models. At the leading edge, the B-L model yields a better comparison than the q-ω model. On the pressure surface, however, the comparison between the experimental data and the prediction from either turbulence model is poor. A potential reason for the discrepancy on the pressure surface could be the presence of unsteady effects due to stator-rotor interaction in the experiments which are not modeled in the present computations. Prediction using the two-equation model is in general poorer than that using the zero-equation model, while the former requires at least 40% more computational resources.
Gas Turbine Technology for Steel Mill Gas and Syngas Applications
Authors: Luessen H. Peter
Published: December 2014

Recent market place activity over the past years has shown a renewed trend in using steel mill waste gas for combustion in gas turbines. To effectively use steel mill gas, as well as other industrial off gases and syngas from gasification, more than just the combustion process has to be considered. With steel mill gases some of the more critical areas involve gas clean up and compression, as well as integration with the steam system of the host industrial plant.

This paper will summarize some of the special considerations for applying a gas turbine/combined cycle power plant to a steel mill. Due to the similarities of the fuels, this paper will also discuss how this is common to other industrial gases applications. GE has substantial experience in combustion of low calorific fuels as well as industrial process gases and more recently steel mill gases.
A Plastic Fracture Mechanics Analysis of Small Case B Fatigue Cracks Under Multiaxial Loading Conditions
Authors: Wang Y. , Pan J.
Published: December 2014

The near-tip fields of small Case B cracks in power-law hardening materials are investigated under generalized plane-strain and general yielding conditions by finite element analyses. The results for two different crack orientations are examined and compared. The results indicate that the plastic deformation patterns near the tips of the cracks of two different orientations are remarkably similar in terms of the global coordinates. The results of the J integral from the finite element analyses are used to correlate to a fatigue crack growth criterion for Case B cracks. The trends of constant ΔJ contours on the Γ-plane for two cracks of different orientations are virtually the same. Further, the trends are compared reasonably well with those of the experimental results of constant fatigue life and constant fatigue crack growth rate.
A Mechanical Start System for U. S. Navy Destroyer Generator Sets
Authors: Overton Leonard L. , Masincup William E. , Halsey Jack E.
Published: December 2014

A mechanical start system has been developed to start the Ship’s Service Gas Turbine Generators (SSGTG) on board U.S. naval destroyers. The current starting system uses either stored high pressure air or bleed air from another running turbine. The U.S. Navy has reviewed the high pressure air system and found it to be a costly system for both ship construction and maintenance. As a result, the Navy is requiring an alternative starting method that will replace high pressure air. It should be noted that any alternative that introduces compressed air to start the SSGTG depends on the start air regulating assembly and the pneumatic starter.

The Redundant Independent Mechanical Start System (RIMSS) consists of an Allison Model 250 turboshaft engine mounted above the SSGTG main reduction gearbox. The turboshaft power take off is connected to the pinion shaft of the reduction gearbox by means of a parallel shaft auxiliary transfer gearbox. The transfer gearbox connection to the reduction gearbox replaces the pneumatic starter adapter pad but provides a means to also connect the pneumatic starter. As a result, the pinion shaft can be driven either pneumatically by the air turbine or mechanically by the Model 250 engine. This provides an alternative starting mode which is totally independent of the present means of starting. This will increase the reliability and availability of the SSGTG since it can still be started even if the pressure regulator or the pneumatic starter is not functional. This system has undergone testing at the Naval Surface Warfare Center Carderock Division facility in Philadelphia.
Future Material Needs for Low Emissions Gas Turbines
Authors: Mehta Jayesh M. , Askew James
Published: December 2014

The modern low emissions gas turbines operate under some of the most challenging operating conditions as more demands are exercised on their performance. For example, the future engines will have higher thrust-to-weight ratio, improved fuel efficiencies, and high overall pressure ratios. Furthermore, the environmental safety needs will dictate many of the future low emissions combustor designs to be either Lean-Premixed (LP), Lean Direct Injection (LDi), Rich-burn-Quick quench-Lean burn (RQL) or catalytic. These will impose additional demands on developing unique high temperature materials that can survive in oxidizing and reducing environments, under high temperature and pressure conditions, and have other material properties such as superior strength and stiffness. In this paper, first we discuss the salient features of advanced low-emissions gas turbines and their needs for unique material technology development. Next, we discuss the state-of-the-art material technology development as it is applied to current gas turbines. And, finally we review the material developments that will be needed for the future gas turbine engines.
Flow Measurements in a Reactive Model of a Gas Turbine Combustion Chamber
Authors: Fiaschi D. , Manfrida G. , Bonciani L.
Published: December 2014

The results of the investigation of the flow in a transparent (quartz tube) downscaled (≈1:3) model of a lean-premix type gas turbine combustion chamber are presented and discused. The model was tested at atmospheric pressure in reacting conditions; flow measurements were taken by a two-channel fiber-optic laser doppler velocimeter, using Al2O3 seeding of the air flowrate. The measurements cover a wide flow field inside the combustion chamber, including flame development and recirculating regions. Long-time samples (10–20 s) were used in order to achieve a good accuracy in the measurement of average flow conditions over the whole flow field; this involved a limited capability of representation of high-frequency components of turbulence, which could be locally obtained with optimization of the data rate and seeding conditions. Fast measurements were also locally performed where the seeding conditions were favourable. Integral variables and power spectra for reacting conditions show some distinctive aspects for the turbulence structure of reacting turbulent flows in confined spaces. Further measurements cover the outlet throat section of the premix combustor, demonstrating the persistence of a radial flow component on account of wall curvature effects and a certain degree of asimmetry in the inlet velocity distribution.
A Detailed Analysis of Film Cooling Physics: Part IV — Compound–Angle Injection With Shaped Holes
Authors: Brittingham Robert A. , Leylek James H.
Published: December 2014

The flow physics of film cooling with compound–angle shaped holes is documented for realistic gas turbine parameters. For the first time in the open literature, the combined effects of compound–angle injection and hole shaping are isolated and the dominant mechanisms are examined. Results provide valuable insight into the flowfield of this class of film–cooling jets. Computational and experimental results are presented for a row of holes injected at 35° on a flat plate with three distinct geometric configurations: (1) streamwise injected cylindrical holes (reference case); (2) 15° forward–diffused holes injected at a 60° compound angle; and (3) 12° laterally–diffused holes injected at a 45° compound angle. Detailed field and surface data, including adiabatic effectiveness (η) and heat transfer coefficient (h), of the two compound–angle shaped holes are provided and compared to: (i) the reference streamwise cylindrical case; (ii) results from Part II detailing the compound–angle flowfield for cylindrical holes; (in) results of Part III detailing the streamwise injected shaped–hole flowfield; and (iv) experimental data. The 60° compound–angle forward–diffused holes provided excellent lateral coolant distribution, but suffered from crossflow ingestion at the film–hole exit plane. The 45° compound–angle lateral–diffused hole had much steeper lateral effectiveness variations. A previously documented and validated computational methodology was utilized. Computations were performed using a multi–block, unstructured–adaptive grid, fully–implicit pressure–correction Navier–Stokes code with multi–grid and under–relaxation type convergence accelerators. All simulations had fixed length–to–diameter ratio of 4.0, pitch–to–diameter ratio of 3.0, nominal density ratio of 1.55 and film–hole Reynolds number of 17350, which allowed isolation of the combined effects of compound–angle injection and hole shaping for nominal blowing ratios of 1.25 and 1.88. The results demonstrate the ability of the prescribed computational methodology to accurately predict the complex flowfield associated with compound–angle shaped–hole film–cooling jets.
Time Dependent Crack Initiation and Growth in Ceramic Matrix Composites
Authors: Begley Matthew R. , Cox Brian N. , McMeeking Robert M.
Published: December 2014

Matrix cracking in ceramic matrix composites with fine grained fibers at high temperatures will be governed by fiber creep, as relaxation of the fibers eliminates crack tip shielding. Using a time dependent bridging law which describes the effect of creeping fibers bridging a crack in an elastic matrix, crack growth initiation and history have been modeled. For a stationary crack, crack tip stress intensity factors as a function of time are presented to predict incubation times before subcritical crack growth. Two crack growth studies are reviewed: a constant velocity approximation for small-scale bridging, and a complete velocity history analysis which can be used to predict crack length as a function of time. The predictions are summarized and discussed in terms of identifying various regimes of crack growth initiation, subcritical growth, and catastrophic matrix cracking.
Reliability of a Conceptual Ceramic Gas Turbine Component Subjected to Static and Transient Thermomechanical Loading
Authors: DiMascio Paul S. , Orenstein Robert M. , Rajiyah Harindra
Published: December 2014

A three year program to evaluate the feasibility of using monolithic silicon nitride ceramic components in gas turbines was conducted. The use of ceramic materials may enable design of turbine components which operate at higher gas temperatures and/or require less cooling air than their metal counterparts. The feasibility evaluation consisted of three tasks: 1) Expand the material properties database for candidate silicon nitride materials, 2) Demonstrate the ability to predict ceramic reliability and life using a conceptual component model and 3) Evaluate the effect of proof testing on conceptual component reliability. The overall feasibility goal was to determine whether established life and reliability targets could be satisfied for the conceptual ceramic component having properties of an available material. Fast and delayed fracture reliability models were developed and validated via thermal shock and tensile experiments. A creep model was developed using tensile creep data. The effect of oxidation was empirically evaluated using four-point flexure samples exposed to flowing natural gas combustion products. The reliability- and life-limiting failure mechanisms were characterized in terms of temperature, stress and probability of component failure. Conservative limits for design of silicon nitride gas turbine components were established.
Throughflow Design Using an Automatic Optimisation Strategy
Authors: Cravero C. , Dawes W. N.
Published: December 2014

A procedure has been developed to optimise the design of an axial turbine stage. A standard, streamline curvature throughflow code, with standard loss correlations, was combined with a simple parameterisation of the geometry and a standard, constrained minimisation routine. An analytic differentiation of the loss correlations was also carried out to provide insight into the influence of each of the flow variables on the stage performance. The complete procedure has been demonstrated on a single high pressure axial steam turbine stage. The initial and optimised configurations for the stage were then analysed using a 3D Navier-Stokes solver. The results confirm the improved performance and give some additional insight into the origin of the benefits.
A CFD Benchmark Study: Leading Edge Film-Cooling With Compound Angle Injection
Authors: Martin C. A. , Thole K. A.
Published: December 2014

This paper presents a blind CFD benchmark of a simulated leading edge for a turbine airfoil. The geometry studied was relevant for current designs with two rows of staggered film-cooling holes located at the stagnation location (θ = 0°) and at θ = 25°. Both rows of cooling holes were blowing in the same direction which was 90° relative to the streamwise direction and had an injection angle with respect to the surface of 20°. Realistic engine conditions were simulated including a density ratio of DR = 1.8 and an average blowing ratio of M = 2 for both rows of cooling holes. This blind benchmark coincided with an experimental study that took place in a wind tunnel simulation of a quarter cylinder followed by a flat afterbody. At the stagnation region, the CFD calculation overpredicted the adiabatic effectiveness because the model failed to predict a small separation region that was measured in the experiments. Good agreement was achieved, however, between the CFD predictions and the experimentally measured values of the laterally averaged adiabatic effectiveness downstream of the stagnation location. The coolant pathlines showed that flow passed from the first row of holes over the second row of cooling holes indicating a waste of the coolant.
A Fast-Response High Spatial Resolution Total Temperature Probe Using a Pulsed Heating Technique
Authors: Buttsworth D. R. , Jones T. V.
Published: December 2014

This paper discusses the operation of a fast-response total temperature probe based on transient thin film heat flux gauge technology. The probe utilizes two thin film gauges located close to the stagnation point of a hemispherically-blunted fused quartz cylinder. Development of the present total temperature probe was motivated by the need for a fast-response device with a high spatial resolution. The diameter of the probe was 2.8 mm and the two films were separated by a distance of less than 1 mm. Measurement of the flow total temperature requires the films to operate at different temperatures. In the present work, the temperature difference was generated using a current pulse (approximately 70 mA with a duration of around 1 s) to heat one of the thin film resistance gauges. With this technique, temperature differences between the hot and cold films of around 120 K were achieved. The interpretation of the transient surface temperature measurements is discussed, and the validity and utility of the technique are demonstrated with reference to total temperature and convective heat transfer coefficient measurements in a compressible free jet. The results demonstrate that accurate total temperature and convective heat transfer coefficient measurements with high spatial and temporal resolution can be obtained with the present device.
Combustion Noise at Elevated Pressures in a Liquid-Fueled Premixed Combustor
Authors: Darling Douglas , Radhakrishnan Krishnan , Oyediran Ayo
Published: December 2014

Noise generated in gas turbine combustors can exist in several forms — broadband noise, sharp resonant peaks, and regular or intermittent non-linear pulsing. In the present study, dynamic pressure measurements were made in several JP-5-fueled combustor configurations, at various mean pressures and temperatures. The fluctuating pressure was measured at mean pressures from 6 to 14 atm and inlet temperatures from 550 K to 850 K. The goal of the present work was to study the effect of changes in mean flow conditions on combustor noise: both broadband noise and sharp tones were considered. In general, the shape of the broadband noise spectrum was consistent from one configuration to another. The shape of the spectrum was influenced by the acoustic filtering of the combustion zone. This filtering ensured the basic consistency of the spectra. In general, the trends in broadband noise observed at low mean pressures were also seen at high mean pressures; that is, the total sound level decreased with both increasing equivalence ratio and increasing inlet temperature. The combustor configurations without a central pilot experienced higher broadband noise levels and were more susceptible to narrow peak resonances than configurations with a central pilot. The sharp peaks were more sensitive to the mean flow than was the broadband noise, and the effects were not always the same. In some situations, increasing the equivalence ratio made the sharp peaks grow, while at other conditions, increasing the equivalence ratio made the sharp peaks shrink. Thus, it was difficult to predict when resonances would occur, however, they were reproducible. Noise was also observed near lean blow out. As with other types of noise, lean blow out noise was affected by the combustion chamber acoustics, which apparently maintains the fluctuations at a uniform frequency. However, the actual conditions when this type of noise was experienced appeared to simply follow the lean blow out limit, as it varied with mean temperature and pressure.
Characterizing the Effects of Air Injection on Compressor Performance for Use in Active Control of Rotating Stall
Authors: Behnken Robert L. , Leung Mina , Murray Richard M.
Published: December 2014

Previous work has developed an air injection controller for rotating stall based on the idea of a shifting compressor characteristic and the Moore-Greitzer three state compressor model. In order to demonstrate this form of control experimentally, a series of open loop tests were performed to measure the performance characteristics of a low speed axial flow compression system when air is injected upstream of the rotor face. The position of the air injection port relative to the hub and the rotor face and the angle relative to the mean axial flow were varied. The tests show that the injection of air has drastic effects on the stalling mass flow rate and on the size of the hysteresis loop associated with rotating stall. The stalling mass flow rate was decreased by 10% and the hysteresis loop was completely eliminated under some conditions. The results of the open loop parametric study were then used to implement a closed loop control strategy based on a shifting characteristic.
Impingement Heat Transfer From Rib Roughened Surface Within Arrays of Circular Jet: The Effect of the Relative Position of the Jet Hole to the Ribs
Authors: Haiping Chang , Dalin Zhang , Taiping Huang
Published: December 2014

Impingement heat transfer from rib roughened surface within two-dimensional arrays of circular jet has been investigated experimentally. After the jet impinges on the rib roughened surface parallel to the jet plate, it is constrained to exit in a single direction along the channel formed by the jet plate and the rib roughened surface. An initial crossflow is present which approaches the arrays through an upstream extension of the channel. The configurations considered are intended to simulate the impingement cooling midchord region of the gas turbine aerofoils in case where an initial crossflow is also present. The study covered four different relative positions of the jet hole to the ribs: jet hole before the rib (−p/4), jet hole on the rib, jet hole behind the rib (+p/4) and jet hole between the ribs (midst,+p/2). The tests were performed for Reynolds number Re = 8000 and 15000, and the nondimensional jet-to-surface spacing z/d = 1.4, 2.0 and 3.0. The test results show that the impingement heat transfer from the rib roughened surface can be considerably improved by adequately arranging the relative position of the jet hole to the ribs.
Calculation of a Premixed Swirl Combustor Using the PDF Method
Authors: Hsu A. T. , Anand M. S. , Razdan M. K.
Published: December 2014

The evolution probability density function (PDF) method provides a framework for the simulation of both diffusion and premixed turbulent flames. With this method, the chemical reaction rates are treated without approximation. In contrast, the conventional Reynolds-average methods need to model the mean reaction rates in turbulent flame calculations. In addition, conventional methods require special models for premixed flames that are developed under restrictive assumptions and rely on ad hoc expressions for the rate of reaction progress. The present work demonstrates the capability of the PDF method in realistic combustor design calculations. A lean premixed flame swirl combustor is simulated using the scalar PDF method, and the results are compared with experimental data. It is shown that the PDF method can correctly predict the turbulent flame speed and location of the flame. The ability of the PDF method to handle finite-rate complex chemistry of any number of reaction steps makes it an ideal candidate for emissions predictions in low emission combustor designs.
The Effect of Shaping Inclined Slots on Film Cooling Effectiveness and Heat Transfer Coefficient
Authors: Farmer J. P. , Seager D. J. , Liburdy J. A.
Published: December 2014

The objective of this paper is to evaluate the performance of two inclined slot jets when used in a film cooling application. The coolant gas was injected onto a flat plate in a subsonic wind tunnel. The two geometries used are a 35° inclined slot and a shaped 35° inclined slot. A density ratio of 1.55 was created by using foreign gas (carbon dioxide) injection. In order to determine heat transfer, a thin stainless steel foil was used as a resistance heater to create a constant heat flux. Using a transient method, the heat transfer coefficient was calculated downstream of the two-dimensional slots. In addition, the adiabatic effectiveness was measured. Shaping the slot improves overall performance, with an increased effectiveness and a slight reduction in heat transfer coefficient, particularly far downstream of the slot.