bluuebunny/crossref_metadata_2025 huggingface dataset:
Active Control of Tip Clearance Flow in Axial Compressors
Authors: Bae Jinwoo , Breuer Kenneth S. , Tan Choon S.
Published: February 2009

Control of compressor tip clearance flows is explored in a linear cascade using three types of fluidic actuators; Normal Synthetic Jet (NSJ; unsteady jet normal to the mean flow with zero net mass flux), Directed Synthetic Jet (DSJ; injection roughly aligned with the mean flow), and Steady Directed Jet (SDJ), mounted on the casing wall. The effectiveness of each active control technique is determined in terms of its ability to achieve: (1) reduction of tip leakage flow rate, (2) mixing enhancement between tip leakage and core flow, and (3) increase in streamwise momentum of the flow in the endwall region. The measurements show that the NSJ provides mixing enhancement only, or both mixing enhancement and leakage flow reduction, depending on its pitchwise location. The DSJ and SDJ actuators provide streamwise momentum enhancement with a consequent reduction of clearance-related blockage. The blockage reduction associated with the use of NSJ is sensitive to actuator frequency, whereas that with the use of DSJ is not. For a given actuation amplitude, DSJ and SDJ are about twice as effective as NSJ in reducing clearance-related blockage, Further the DSJ and SDJ can eliminate clearance-related blockage with a time-averaged momentum flux roughly 16% of the momentum flux of the leakage flow. However, achieving an overall gain in efficiency appears to be hard; the decrease in loss is only about 30% of the expended flow power from the present SDJ actuator. Guidelines for improving the efficiency of the directed jet actuation are presented.
Improved Non-Equilibrium Turbulence Closure Modeling for Axial Flow Compressors Simulation
Authors: Borello D. , Rispoli F.
Published: February 2009

The present paper investigates the predictive attitude of three non conventional turbulence closures in simulating the physics pertinent to decelerating turbomachinery flows. The performance of a cubic k-ε model and an algebraic Reynolds stress model adopting a non-linear link between turbulence and velocity gradients have been exploited with reference to their capabilities in predicting anisotropy effects and the sensibility to streamlines curvature. In addition, a modification of the kinetic energy production term in standard isotropic model has been also tested, in accord with Kato and Launder formulation. To put in evidence the predictive capabilities of such models a comparison with the standard Launder and Sharma turbulence closure will be carried out. The authors adopt a multi-level parallel solver developed in the framework of a finite element (FE) method based on a stabilized Petrov-Galerkin formulation. The FE method is here applied on mixed Q2-Q1 element shape functions. The solution scheme is based on a Multigrid (MG) solver properly developed to operate in a parallel environment. To increase the performance of MG schemes in solving self-adjoint elliptic problems a remedial strategy consisting of a LFMG-type scheme named Hybrid Linear Full Multi-Grid technique (HLFMG) has been proposed. The parallel algorithm follows a Single Program Multiple Domains (SPMD) scheme. The subdomains fields for Reynolds Averaged Navier-Stokes problem are generated by the adoption of an original overlapping domain decomposition technique. In the present paper we analyze a two-dimensional leading edge and both a DCA (2D) and NACA65 (3D) compressor cascades. The flows considered for model benchmarking are highly challenging because of the possibly transitional nature of the flow and the existence of three-dimensional phenomena and of significant separation regions. The potential of non-standard closures has been investigated in terms of both velocity and turbulent variables. In the leading edge test-case, the cubic k-ε model is shown to provide a better base-line for nonequilibrium effects simulation with respect to the algebraic stress model. The Kato and Launder modification has shown poor predictive attitude in representing the flow downstream the impingement and it has not adopted for the other test-cases. In the DCA simulation the presence of large transition regions leads to a degradation of the predictions of the cubic model. Algebraic stress model has shown performances comparable to the cubic model ones. The 3D linear cascade flow simulations put in evidence that the standard and algebraic Reynolds stress approaches have similar performance, clearly worse respect to the cubic model.
Modeling of Thermoacoustic Oscillations in Annular Combustor
Authors: Ni Alexander , Jansohn Peter
Published: February 2009

An approach for modeling combustion instabilities in annular combustors is presented. The main feature that distinguishes the method from other existing approaches is the coupled consideration of acoustics of multiple burners in an annular arrangement. The developed method allows modeling of annular combustors with an arbitrary number of different burners. The influence of azimuthal nonuniformities due to different burner characteristics on the combustor pulsations in a gas turbine combustor is investigated. It is shown that the instability growth rate is strongly influenced by the burner arrangement.
H System™ Technology Update
Authors: Pritchard John E.
Published: February 2009

Responding to a global market demand for clean, reliable and low-cost energy, GE Power Systems introduced its newest, most advanced generation of gas turbines in 1995. Called the H System™ this technology uses higher efficiency and output to produce electricity at lower costs than any other gas-fired power generation system available today. Efficiency. The H System™ is designed to achieve 60% thermal efficiency, a major milestone in the power generation industry. The most efficient combined-cycle systems currently in operation reach 57–58% efficiency. The use of advanced materials and a unique, steam-cooling system enable the higher firing temperatures required for this increase in efficiency. The integrated closed-loop steam cooling system uses steam from the steam turbine bottoming cycle to more efficiently cool the critical gas turbine parts, and returns the steam to the bottoming cycle where it can produce additional work in the steam turbine. Environmental Performance. The H System™ burns natural gas, a much cleaner fuel than other options such as oil or coal. In addition, the system’s higher efficiency means that less fuel is needed to produce the same amount of power, further reducing emissions of CO2 and NOx. The closed-loop steam cooling system cools both the rotating and stationary gas turbine parts to maintain combustion chamber exit temperatures for low NOx emissions, while permitting the high gas turbine firing temperatures required for increased efficiency and output. Reliability. The H System™ is based on technology proven in millions of hours of GE aircraft engine and power plant service. In particular, the lessons learned throughout the development and 7.1 million hours of worldwide operating experience of GE’s F technology have been applied to the H System™. Status. This technology has been subjected to an extensive validation process. This process includes component, scale, and full size rig testing, Full Speed No Load factory tests, and culminates in Full Speed Full Load characterization testing in a commercial power plant. This paper discusses the validation process and status for the 50 Hz S109H and 60 Hz S107H in more detail.
Separation Control on Low-Pressure Turbine Airfoils Using Synthetic Vortex Generator Jets
Authors: Volino Ralph J.
Published: February 2009

Oscillating vortex generator jets have been used to control boundary layer separation from the suction side of a low-pressure turbine airfoil. A low Reynolds number (Re = 25,000) case with low free-stream turbulence has been investigated with detailed measurements including profiles of mean and fluctuating velocity and turbulent shear stress. Ensemble averaged profiles are computed for times within the jet pulsing cycle, and integral parameters and local skin friction coefficients are computed from these profiles. The jets are injected into the mainflow at a compound angle through a spanwise row of holes in the suction surface. Preliminary tests showed that the jets were effective over a wide range of frequencies and amplitudes. Detailed tests were conducted with a maximum blowing ratio of 4.7 and a dimensionless oscillation frequency of 0.65. The outward pulse from the jets in each oscillation cycle causes a disturbance to move down the airfoil surface. The leading and trailing edge celerities for the disturbance match those expected for a turbulent spot. The disturbance is followed by a calmed region. Following the calmed region, the boundary layer does separate, but the separation bubble remains very thin. Results are compared to an uncontrolled baseline case in which the boundary layer separated and did not reattach, and a case controlled passively with a rectangular bar on the suction surface. The comparison indicates that losses will be substantially lower with the jets than in the baseline or passively controlled cases.
Experimental Surface Heat Transfer and Flow Structure in a Curved Channel With Laminar, Transitional, and Turbulent Flows
Authors: Ligrani P. M. , Hedlund C. R.
Published: February 2009

Heat transfer and flow structure are described in a channel with a straight portion followed by a portion with mild curvature at Dean numbers from 100 to 1084. The channel aspect ratio is 40, radius ratio is 0.979, and the ratio of shear layer thickness to channel inner radius is 0.011. The data presented include flow visualizations, and spanwise-averaged Nusselt numbers. Also included are time-averaged turbulence structural data, time-averaged profiles of streamwise velocity, spectra of longitudinal velocity fluctuations, and a survey of the radial time-averaged vorticity component. Different flow events are observed including laminar two-dimensional flow, Dean vortex flow, wavy Dean vortex flow (in both undulating and twisting modes), splitting and merging of Dean vortex pairs, transitional flow with arrays of Dean vortex pairs, and fully turbulent flow with arrays of Dean vortex pairs. Transitional events generally first appear in the curved portion of the channel at Dean numbers less than 350 in the form of arrays of counter-rotating Dean vortex pairs. At Dean numbers greater than 350, transitional events occur in the upstream straight portion of the channel but then continue to cause important variations in the downstream curved portion. The resulting Nusselt number variations with curvature, streamwise development, and Dean number are described as they are affected by these different laminar, transitional, and turbulent flow phenomena.
Computational Aerodynamic Design Optimization
Authors: Abdel Dayem A. M.
Published: February 2009

Quasi-1D Euler equations have a considerable part of research to allow the prediction of the internal and external flows of the aerodynamic applications. Numerical solving of these equations by a so-called computational fluid dynamics (CFD) finds a very close agreement of the flow solver regarding to the experimental tests. Using CFD in the aerodynamic design is a new area of research that can be a useful addition in this field. Aerodynamic design of a subsonic and transonic converged-diverged nozzle is the task of this work. ARC1D is a robust algorithm used in the aerodynamic numerical simulation area. Developing ARC1D code and an objective function that is constrained by the nozzle axial velocity are considered. The nozzle design is optimized with various numbers of design variables (nozzle cross-sectional area) versus the accuracy and computation time. The discretized flow equations of Quasi-1D Euler equations, finite-difference scheme and optimality conditions are simultaneously solved in a single system of nonlinear equations. KSOPT optimization algorithm was efficiently used in the problem optimization without design constraints. It can be concluded that the code obtained good results regardless the computation time that is not a critical factor in the one-dimensional solution. Also, the finite-difference of the gradient of the objective function was found efficient in the design optimization with accepted computation time.
Rolls Royce/Allison 501-K Gas Turbine: Anti-Fouling Compressor Coatings Shipboard — Phase I
Authors: Caguiat Daniel E. , Zipkin David M. , Patterson Jeffrey S.
Published: February 2009

Naval Surface Warfare Center Carderock Division (NSWCCD) Gas Turbine Emerging Technologies Code 9334 conducted a land-based evaluation of fouling-resistant compressor coatings for the 501-K17 Ship Service Gas Turbine Generator (SSGTG) [1]. The purpose of this evaluation was to determine whether such coatings could be used to decrease the rate of compressor fouling and associated fuel consumption. Based upon favorable results from the land-based evaluation, a similar coated compressor gas turbine engine was installed onboard a United States Navy vessel. Two data acquisition computer (DAC) systems and additional sensors necessary to monitor and compare both the coated test engine and an uncoated control engine were added. The goal of this shipboard evaluation was to verify land-based results in a shipboard environment. Upon completion of the DAC installation, the two gas turbine engines were operated and initial data was stored. Shipboard data was compared to land-based data to verify validity and initial compressor performance. The shipboard evaluation is scheduled for completion in June 2003, at which time data will be analyzed and results published.
Mild Combustion in a Novel CCGT Cycle With Partial Flue Gas Recirculation
Authors: Camporeale S. M. , Casalini F. , Saponaro A.
Published: February 2009

A novel Combined Cycle Gas Turbine layout is proposed for using heavy fuel oil in a combustion mode called “Mild Combustion”, characterized by a very low adiabatic flame temperature and flat temperature field in the combustion chamber and low pollutant emissions. “Mild Combustion” is obtained by means of the dilution of reactants with inert gas like combustion product resulting in a very low oxygen concentration of the mixture at the ignition. To stabilize the combustion process in such a condition the reactants temperature has to be raised above the self ignition value. In industrial application this particular preconditioning of the reactants can be reached partially before the combustion chamber and finally in process by means of a performed aerodynamic that further dilute and heat-up the mixture. An experimental analysis of the oil combustion behaviour inside the gas turbine exhaust flow has been arranged at Centro Combustione of Ansaldo Caldaie in Gioia del Colle (Italy). The turbine exhaust gases are simulated by mixing those produced in a gas burner with external air preheated at different temperatures in order to have different final oxygen concentrations and temperature levels. The influence of the main combustion parameters regarding the process feasibility and environmental impact are presented and analysed. Good results in terms of NOx emissions and soot formation have been obtained for heavy oil combustion in a 10% oxygen oxidizer concentration requiring a combustion chamber inlet temperature of about 900K. In order to meet these conditions, a novel CCGT cycle in which about 64% of combustion products are re-circulated before entering the combustion chamber, is proposed. The thermodynamic analysis shows that the efficiency that could be achieved by the proposed cycle is a few percent lower than the efficiency of a combined cycle power plant fuelling natural gas, with the same turbine inlet temperature and similar turbine blade cooling technology.
Frequency-Scanning Eddy Current NDE for Duplex Metallic Coatings
Authors: Krzywosz Kenji , Viswanathan Vis
Published: February 2009

EPRI is involved in a multi-year program to test, evaluate, and develop a field-deployable eddy current NDE system for life assessment of blade coatings for advanced gas turbines. An eddy current system was assembled and tested on service-aged 7FA first stage blade buckets, which were coated with GT 33+ duplex metallic coatings. Testing of transverse cutout sections showed presence of normal coating, coating degradation due to β-phase depletion, and cracked coatings with some cracks penetrating into the GTD-111 substrate. By plotting normalized multiple-frequency eddy current coil impedance values, the eddy current technique was able to assess and provide the following coating and airfoil conditions: 1) normal coating; 2) degraded coating; 3) cracked coating; and 4) possible corrosion of GTD-111 substrate. Using a built-in three-layer inversion program, conductivity values of topcoat, bond coat, and GTD-111 substrate were also estimated using aged blade buckets.
Dynamics of a Three Level Rotor System Using Solid Elements
Authors: Rao J. S. , Sreenivas R.
Published: February 2009

This paper discusses the interaction of support structures on the dynamics of a dual rotor system. The system considered is a dual rotor, supported on flexible bearings, which are in turn mounted in a flexible casing. ANSYS® is used for modeling and meshing the dual rotors and the casing. The rotors are modeled using solid elements. The bearings are simulated as springs, wherein the direct and cross coupled stiffness and damping coefficients are applied. The casing is also modeled and meshed in ANSYS® using solid elements. Different spin speeds are applied to the dual rotor system. The casing is also rotated at a zero spin speed. The Stress stiffening and spin softening options are also set on for the dual rotor system. The system natural frequencies are obtained for different spin speeds and the Campbell diagram of the system is plotted. The critical speeds due to per revolution excitations are then extracted from the Campbell diagram.
Modeling Laminar-to-Turbulent Transition in a Low-Pressure Turbine Flow Which Is Unsteady Due to Passing Wakes: Part I — Transition Onset
Authors: Jiang Nan , Simon Terrence W.
Published: February 2009

The open literature on modeling transition to turbulence of boundary layer flows in low-pressure turbines is reviewed. Included are the separated flow transition onset models of Mayle and of Davis et al. and the attached flow transition onset models of Mayle, Abu-Ghannam and Shaw and Drela. Their results are applied against data previously taken at the University of Minnesota (UMN) to assess their performance for use on the suction surface of a turbine blade in the presence of passing wakes. The data show measurements of velocity, turbulence level, intermittency and spatial and temporal acceleration resolved in space and phase angle within the wake passing period. In a “quasi-static” comparison, the input values to the models are values taken from the experiment, resolved in phase angle within the wake-passing period. Predictions from the models (the flow states with regard to transition throughout the wake-passing period) are compared with instantaneous intermittency values taken from the experiment. The Mayle separated and attached flow onset models are shown to be successful for the case investigated when applied in that fashion. The Abu-Ghannam and Shaw and Drela transition onset models predict onset locations which are somewhat downstream of where the data indicate the transition onset to be. Unique characteristics regarding transition observed at different times in a wake passing cycle are discussed. Some reasons are given to explain the differences between experimental results and model predictions. Transition onset modeling is addressed in the present paper and transition path modeling is addressed in a companion paper (part II).
The Impact of Fuel Flexible Gas Turbine Control Systems on Integrated Gasification Combined Cycle Performance
Authors: Shilling Norman Z. , Jones Robert M.
Published: February 2009

Interest in Integrated Gasification Combined Cycle (IGCC) is developing from a need for fuel diversification as a hedge for natural gas price and availability. In IGCC, the gas turbine combustion system is critical to meeting this need. The combustion system also needs to achieve superior environmental performance. This paper discusses specific requirements for IGCC combustion systems that derive from characteristics of gasification fuels and integration with the gasification process. Tradeoffs between system physical design parameters and control strategies must be evaluated in terms of overall functionality of the IGGC process. The key metrics for evaluating “goodness” of design are reliability, availability, maintainability (RAM), robustness to process variability, response to upsets and trips, time to synchronization and startup and shutdown automation. For IGCC, high availability is achieved from the capability of the turbine to robustly co-fire low-calorific synthesis gas with supplementary fuels. Co-firing compensates for shortfalls in gasifier output and maintains continuity of power service during servicing of the gasification plant. Controls need to provide seamless transfers between varying levels of syngas and supplementary fuel, and over the widest range of fuel mixes and power levels. Low calorific fuels provide special challenges to control system design. Variability in syngas composition, temperature and pressure will impact the minimum and maximum nozzle pressure drops and controllability. The effect of fuel constituents on controllability is captured in the modified Wobbe index. Stability and margin against flameout is captured in the upper-to-lower flammability ratio. The paper discusses the restrictions on these parameters for IGCC combustion systems. Control hardware and manifolding necessary with low calorific fuel can potentially conflict with accessibility to the gas turbine. Safe transfers from natural gas to syngas and shutdowns require purge strategies that account for residual energy in ductwork. Finally, the design of the Exxon Singapore IGCC control system is described which provides an extended range of cofiring and load control.
The Impact of Forward Swept Rotors on Tip-Limited Low-Speed Axial Compressors
Authors: McNulty G. Scott , Decker John J. , Beacher Brent F. , Khalid S. Arif
Published: February 2009

This paper presents an experimental and analytical study of the impact of forward swept rotors on tip-limited, low-speed, multi-stage axial compressors. Two different configurations were examined, one with strong tip-clearance flows and the other with more moderate levels. Evaluations were done at multiple rotor tip clearance levels to assess differences in clearance sensitivity. Both configurations are low-speed models of the rear stages of modern aircraft engine high pressure ratio compressors. Compared to conventionally stacked (radial) rotors, the forward swept blades demonstrated improvements in stall margin, efficiency and clearance sensitivity. The benefits were more pronounced for the configuration with stronger tip-clearance flows. Detailed flow measurements and 3-D viscous CFD analyses are used to investigate the responsible flow mechanisms. Forward sweep causes a spanwise redistribution of flow toward the blade tip and reduces the tip loading in terms of static pressure coefficient. This results in reduced tip-clearance flow blockage, a shallower (more axial) leakage/freestream interface angle and a smaller region of reversed flow in the clearance gap.
Review of Titanium Application in Gas Turbine Engines
Authors: Elrod Charles W.
Published: February 2009

With the continuing desire to make engines with a high thrust to weight advantage, titanium is the metal of choice for the gas turbine engine. The use of titanium in the engine must be considered with reasonable care. The metal has been known to combust under certain conditions. The Air Force conducted a number of studies to evaluate the use of titanium in the engine and in other environments. As a result of the studies the effects the environment, the alloying, the thickness and burn rate were among the conditions evaluated. Also the studies were conducted to determine the self-sustained combustibility of titanium and its alloys in the various situations that were established for the evaluations. The studies considered fifty-four different titanium alloys, which included a sample of most of the current materials, some of the advanced materials and a number of unusual alloys. This effort resulted in the identification of easy to burn, harder to burn and very difficult to burn alloys. With this information we can now look at issues related to where certain alloys would benefit the compressor the most. For example, Ti 6Al4V would most likely be used in the fan section of the compressor, due to the thickness of the blade, the low pressure in that section and the gap above the blade. The compressor has a number of issues that can be partially resolved with the use of titanium in a manner that is consistent with safe procedures. This report will examine these issues and present some considerations that should be considered when applying titanium to the gas turbine engine. This paper will look into the turbine engine and examine those areas where the potential for compressor fires are likely and make suggestions on ways to limit the potential for catastrophic damage and in the long run make the engine more resilient in the future. This paper will examine the problems that have followed the engine development with titanium as one of the major players in the selection process. We will describe some of the technology which makes the use of titanium safer. Titanium will be with the engine technology for some time and the goal of most design and research studies should be to make that time as safe and reliable as possible. This paper will show how research can provide the valuable link from basic studies to engine design.
Active Flow Separation Control of a Stator Vane Using Surface Injection in a Multistage Compressor Experiment
Authors: Culley Dennis E. , Bright Michelle M. , Prahst Patricia S. , Strazisar Anthony J.
Published: February 2009

Active flow control has been applied to the suction surface of stator vanes in a low speed axial compressor. Injection from the suction surface has been shown to reduce separation on vanes that were induced to separate by increasing the vane stagger angle by 3°. Various configurations were investigated including injector geometry (slots versus holes) and type of injection (steady versus unsteady). Unsteady injection was realized using two different approaches; external actuation through a high frequency valve and embedded actuation using a fluidic device internal to the vane. Using total pressure loss through the vane passage as a metric, reductions in area-averaged loss of 25% were achieved using injected massflow rates on the order of 1% of compressor through flow. The development of a tracking control algorithm was also explored for the purpose of closed-loop control. A reliable method of detecting surface separation was implemented using unsteady pressure measurements on the compressor casing near the vane suction surface.
On-Line Hydrocarbon Dew Point Monitoring in Fuel Gas
Authors: Newbound T. D. , Wagiealla W. S.
Published: February 2009

Hydrocarbon dew point in fuel gas has become a recent concern for Saudi Aramco and Saudi Electricity Company (SEC). Together they operate more than 150 land based industrial and aeroderivative combustion gas turbines (CGTs) on natural gas produced in the Eastern Province of Saudi Arabia. Automated on-line hydrocarbon dew point monitoring conducted over the past two years has revealed wide variations in the hydrocarbon dew points of the fuel gas that supply these turbines. During winter months at some locations, hydrocarbon dew points are now known to rise to, and slightly above ambient gas temperatures. Daily variations in dew point temperature average about 12–14 °F (7–8 °C) in winter months with highs occuring in late morning hours. More dramatic changes (60 °F, 33 °C) were recorded and attributed to operational changes in two major gas plants. At a major power generation facility, hydrocarbon dew point data was referenced in time with inlet fuel temperature and inlet fuel pressure recorded from a turbine control system. This data reveals evidence that liquid hydrocarbon was entering the CGT fuel intake. Damage to hot gas path components from liquids in natural gas fuel has cost Saudi Aramco several million dollars over a 10 year period (1985–1995). The estimates are much higher now with expanded use of natural gas into the Central and Western Provinces of Saudi Arabia. The new sources of gas, new processing facilities and longer transmission distances all contribute to greater potential for liquids formation, while upgrades to higher firing temperatures also increases the sensitivity of some CGTs to liquids in the fuel. With dew point monitoring, we will be able to recommend the necessary fuel conditioning equipment and fuel preheating temperatures that will be needed to prevent costly distress to CGTs due to the passage of liquids in the fuel gas.
Regenerative Heat Exchangers for Microturbines and an Improved Type
Authors: Wilson David Gordon
Published: February 2009

The principle of operation of regenerative heat exchangers (“regenerators”) is explained, and the characteristics are compared with those of recuperators. The design rules for heat exchangers in general are stated, and the particular design rules forregenerators are discussed in more detail. Problems in past regenerators have led to an improved type, which is described. Design studies of a regenerator for a typical microturbine at three different effectivenesses are given, and leakage rates estimated. At the highest regenerator effectiveness, and using the improved compressor and turbine design permitted by this effectiveness, it is estimated that a 300-kW microturbine should achieve 50% electrical efficiency.
Investigation of Film Cooling Effectiveness of Full-Coverage Inclined Multihole Walls With Different Hole Arrangements
Authors: Lin Yuzhen , Song Bo , Li Bin , Liu Gaoen , Wu Zhiyong
Published: February 2009

An experimental and numerical investigation of adiabatic film cooling effectiveness was conducted on four full-coverage inclined multihole walls with different hole arrangements. The hole geometrical patterns and the test conditions were chosen to be representative of film cooling designs for modern aeroengine combustor liners. The four hole arrangements were grouped into two types based on lateral hole pitch ( P ) and streamwise row spacing ( S ). One type included two test plates which had the same S and P (S/P = 2) and compound angle (β = 0 deg) but different hole inclination angles ( α ) (30 and 150 deg ). The other type included two test plates which had the same S and P (but S/P = 1) and inclination angle (α = 30 deg) but different compound angles (0 deg and 50 deg). Heat-mass transfer analogy method was employed to investigate the adiabatic film cooling effectiveness of these multihole walls with typical blowing ratios for aeroengine combustors. The numerical simulation was performed to characterize the flowfield and temperature distribution, aiming to further understand the film cooling mechanisms. The experimental results indicated that blowing ratio within the range from 1 to 4 had negligible influence on adiabatic film cooling effectiveness (η) in the case of concurrent coolant injection while hole arrangement had large effect on η. But the blowing ratio within the range from 1 to 4 had large effect on the film cooling effectiveness for the counterflow film cooling scheme. The numerical results were compared with experimental data and fairly good agreement was obtained. The numerical simulation revealed the flow structure, particularly exhibiting significant influence of the interaction between mainstream flow and coolant jets on η. With validation by experimental data, film cooling numerical simulation seems quite helpful in selecting optimum multihole arrangement for modern combustor liner design.
Heat Transfer in Rotating Rectangular Channels (AR = 4:1) With V-Shaped and Angled Rib Turbulators With and Without Gaps
Authors: Lee Eungsuk , Wright Lesley M. , Han Je-Chin
Published: February 2009

An experimental study was performed to measure the regionally averaged heat transfer distributions in a rotating ribbed channel with an aspect ratio of 4:1. The Reynolds number, based on a hydraulic diameter, varies from 5,000 to 40,000. The rotation number ranges from 0 to 0.3, and the inlet coolant-to-wall density ratio (Δρ/ρ) is maintained around 0.122. Six different configurations of ribs, oriented at an angle of 45° to the direction of flow, are placed on both the leading and trailing surfaces: parallel and staggered V-shaped ribs without gaps, parallel and staggered angled ribs without gaps, parallel V-shaped ribs with gaps, and parallel angled ribs with gaps are considered. The rib height-to-hydraulic diameter ratio (e/Dh) is 0.078, and the rib pitch-to-height ratio (P/e) is 10. The channel orientation with respect to the plane of rotation is 135°. The results show that V-shaped rib configuration produces more heat transfer enhancement than the angled rib configurations. It is also shown that there is only negligible difference between the heat transfer enhancement due to the staggered V-shaped ribs without gaps and the enhancement due to the parallel V-shaped ribs without gaps. The same is true for the staggered and parallel angled ribs without gaps. Also, the parallel V-shaped ribs without gaps produce more heat transfer enhancement than the V-shaped ribs with gaps, while the parallel angled ribs with gaps experience overall greater heat transfer enhancement than the angled ribs without gaps. Finally, all surfaces undergo heat transfer enhancement by rotating the channel compared to the stationary channel for all cases.
Verification of an EBC’s Protective Capability by First-Stage Evaluation in a High Temperature, High-Pressure Furnace
Authors: More Karren L. , Tortorelli Peter F. , Walker Larry R.
Published: February 2009

High-temperature, high-pressure exposure furnaces (commonly referred to as Keiser Rigs) have been used successfully to evaluate the ability of environmental barrier coatings (EBCs) on continuous fiber-reinforced ceramic matrix composites and monolithic Si3N4 to protect the underlying substrate at high temperatures and H2O pressures. The ORNL rig provides for a relatively inexpensive way to conduct high sample throughput, first-stage evaluation of an EBCs protective capability on small ceramic specimens under a range of temperatures, pressures, and H2O contents. The exposure of the EBCs in the Keiser Rig is coupled with extensive microstructural analysis to evaluate EBC failure and degradation mechanisms.
Engine Test Experience and Characterization of Self Sealing Ceramic Matrix Composites for Nozzle Applications in Gas Turbine Engines
Authors: Bouillon Eric P. , Spriet Patrick C. , Habarou Georges , Arnold Thibault , Ojard Greg C. , Feindel David T. , Logan Charles P. , Rogers Kimberly , Doppes Glenn , Miller Robert J. , Grabowski Zbigniew , Stetson Doug P.
Published: February 2009

Advanced materials are targeting durability improvement in gas turbine engines. One general area of concern for durability is in the hot section components of the engine. Ceramic matrix composites offer improvements in durability at elevated temperatures with a corresponding reduction in weight for nozzles of gas turbine engines. Building on past material efforts, ceramic matrix composites using a carbon and a SiC fiber with a self-sealing matrix have been developed for gas turbine applications. Prior to ground engine testing, a reduced test matrix was undertaken to aggressively test the material in a long-term hold cycle at elevated temperatures and environments. This tensile low cycle fatigue testing was done in air and a 90% steam environment. After completion of the aggressive testing effort, six nozzle seals were fabricated and installed in an F100-PW-229 engine for accelerated mission testing. The C fiber CMC and the SiC Fiber CMC were respectively tested to 600 and 1000 hours in accelerated conditions without damage. Engine testing is continuing to gain additional time and insight with the objective of pursuing the next phase of field service evaluation. Mechanical testing and post-test characterization results of this testing will be presented. The results of the engine testing will be shown and overall conclusions drawn.
Tailored Structural Design and Aeromechanical Control of Axial Compressor Stall: Part I — Development of Models and Metrics
Authors: McGee O. G. , Graf M. B. , Fre´chette L. G.
Published: February 2009

This two-part paper presents general methodologies for the evaluation of passive compressor stabilization strategies using tailored structural design and aeromechanical feedback control (Part I), and quantitatively compares the performance of several aeromechanical stabilization approaches which could potentially be implemented in gas turbine compression systems (Part II). Together, these papers offer a systematic study of the influence of ten aeromechanical feedback controllers to increase the range of stable compressor operation, using static pressure sensing and local structural actuation to postpone modal stall inception. In this part, the stability of aeromechanically compensated compressors was determined from the linearized structural-hydrodynamic equations of stall inception. New metrics were derived, which measure the level of aeromechanical damping, or control authority of aeromechanical feedback stabilization. They indicate that the phase between the pressure disturbances and the actuation is central to assess the impact of aeromechanical interactions on compressors stability.
Tip Leakage Flows Near Partial Squealer Rims in an Axial Flow Turbine Stage
Authors: Camci Cengiz , Dey Debashis , Kavurmacioglu Levent
Published: February 2009

This paper deals with an experimental investigation of aerodynamic characteristics of full and partial-length squealer rims in a turbine stage. Full and partial-length squealer rims are investigated separately on the pressure side and on the suction side in the “Axial Flow Turbine Research Facility” (AFTRF) of the Pennsylvania State University. The streamwise length of these “partial squealer tips” and their chordwise position are varied to find an optimal aerodynamic tip configuration. The optimal configuration in this cold turbine study is defined as the one that is minimizing the stage exit total pressure defect in the tip vortex dominated zone. A new “channel arrangement” diverting some of the leakage flow into the trailing edge zone is also studied. Current results indicate that the use of “partial squealer rims” in axial flow turbines can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction side partial squealers are aerodynamically superior to the pressure side squealers and the channel arrangement. The suction side partial squealers are capable of reducing the stage exit total pressure defect associated with the tip leakage flow to a significant degree.
Restricted Complexity Controller Design via Multi-Objective Optimization
Authors: Yan Wenjun , Cao Yi
Published: February 2009

The problem of restricted complexity controller synthesis is recast into a multiple objective optimization problem. The general H∞ synthesis approach is introduced first to reveal the limitation of this method. Using nonlinear least square and minimax optimization algorithms, sub-optimal controllers have been developed to satisfy specifications of the frequency performance and transient performance. The simulation and experiment results illustrate that these two methods are very effective in finding low order controllers.
Lubricating Oil Consumption Measurements on an EMD 16-645E Locomotive Diesel Engine
Authors: Froelund Kent , Fritz Steve , Smith Brian
Published: February 2009

Real-Time Oil Consumption (RTOC-III™) measurements were made on a 1,500 kW EMD 16-645E locomotive diesel engine, as part of a program to evaluate commercially available cylinder kits that hold the potential to reduce lubricating oil consumption and hence reduce exhaust particulate matter emissions. The RTOC technique uses sulfur dioxide (SO2), as measured in the exhaust gas stream, as a tracer for oil consumption. The engine was operated on an ultra-low sulfur diesel fuel and commercially available SAE grade 20W40 mineral-based lubricating oil. Knowing the SO2 concentration in the exhaust, the air and fuel flow rates, the lubricating oil consumption rate can be calculated in real-time, i.e. on a second-to-second basis. Use of RTOC on the locomotive engine application has proven to be a cost-effective tool for mapping steady-state lubricating oil consumption rate. Where traditional volumetric oil consumption measurement techniques can take several days to obtain the oil consumption rate from a single operating point, the RTOC technique takes only about 10 minutes per operating mode. Applying this technique, the test duration can thus be tremendously compressed, as compared to the volumetric technique. In addition to cost savings, the repeatability of the data is much improved by applying this novel technique. In this program, steady-state oil consumption was determined at 10 steady-state operating conditions typical of North American freight locomotive operation.
A Laminar Burning Velocity Correlation for Hydrogen/Air Mixtures Valid at Spark-Ignition Engine Conditions
Authors: Verhelst Sebastian , Sierens Roger
Published: February 2009

During the development of a quasi-dimensional simulation programme for the combustion of hydrogen in spark-ignition engines, the lack of a suitable laminar flame speed formula for hydrogen/air mixtures became apparent. A literature survey shows that none of the existing correlations covers the entire temperature, pressure and mixture composition range as encountered in spark-ignition engines. Moreover, there is ambiguity concerning the pressure dependence of the laminar burning velocity of hydrogen/air mixtures. Finally, no data exists on the influence of residual gases. This paper looks at several reaction mechanisms found in the literature for the kinetics of hydrogen/oxygen mixtures, after which one is selected that corresponds best with available experimental data. An extensive set of simulations with a one-dimensional chemical kinetics code is performed to calculate the laminar flame speed of hydrogen/air mixtures, in a wide range of mixture compositions and initial pressures and temperatures. The use of a chemical kinetics code permits the calculation of any desired set of conditions and enables the estimation of interactions, e.g. between pressure and temperature effects. Finally, a laminar burning velocity correlation is presented, valid for air-to-fuel equivalence ratios λ between 1 and 3 (fuel-to-air equivalence ratio 0.33 < φ < 1), initial pressures between 1 bar and 16 bar, initial temperatures between 300 K and 800 K and residual gas fractions up to 30 vol%. These conditions are sufficient to cover the entire operating range of hydrogen fuelled spark-ignition engines.
The New AVL Medium Speed Single Cylinder Engine
Authors: Kling Wolfgang H. , Greylinger Wilhelm
Published: February 2009

For many years engine researchers and development specialists have appreciated the benefits offered by performing engine development and testing on Single Cylinder Engines (SCEs). The SCE essentially isolates the cylinder, providing a powerful tool for detailed combustion research, while mitigating the possibility of misleading data results due to cylinder-to-cylinder interactions. Single Cylinder Engines also offer increased accessibility to key components, allowing for rapid changes, thereby expediting the testing process. Furthermore, SCE testing becomes a practical necessity for large engines with bores greater than 150 mm, where a very large multi-cylinder engine installation becomes very facility limited and impractical. AVL has a long history of design and development of engines in the medium speed range. In addition to well-proven analytical techniques AVL has developed a number of Single Cylinder Engines for testing to support both internally-funded and customer-supported research programs. Since individual customer requirements for single cylinder research may vary considerably, SCEs have typically been unique builds, designed, structurally validated, machined and assembled from “the ground up.” Whilst this approach usually results in a final product which meets the customer’s needs, it is costly, extremely time consuming, prone to numerous design iterations and is often inapplicable for other engine design applications. In seeking a solution to this problem, AVL has come up with an approach which results in an SCE which is quickly, yet inexpensively developed and built. It is durable yet adaptable to specific customer requirements. AVL’s approach has been to develop a successful base engine platform for medium speed single cylinder test engines, and then modify the unit as necessary to meet customer requirements using the customer-provided power cylinder, fuel injection equipment (FIE) and other “upper end” components. This approach results in a robust, reliable, proven design at low cost, which will meet specific customer research needs for many years.
Torsional Vibration and Admissible Limits in Marine Propulsion Installations
Authors: Jenzer Jean , Keller Heinz
Published: February 2009

The torsional vibration calculation (TVC) of new marine installations (propeller driven by diesel engines) is requested by the Classification Societies. The aim of this paper is to shortly introduce the basic knowledge of TVC, to present the validation process of the model and parameters (stiffness, inertia, excitation and damping) and the PC program used at Wa¨rtsila¨ (example of calculation including comparison with measurement). Moreover, the special situation regarding the admissible limits of the torsional stresses given by the Classification Societies is shown (different limits between various societies, for given intermediate and propeller shafts). A proposal to harmonize these limits is presented.
Application of Dual-Fuel™ Engine Technology for On-Highway Vehicles
Authors: Erickson Ryan A. , Campbell Kevin , Morgan David L.
Published: February 2009

Dual-Fuel™ technology combines compression-ignition efficiency with natural gas emissions to create a popular platform for heavy-duty, on-highway, low-emission vehicles. This paper will summarize that technology for on-highway vehicles, benefits to the customer, and commercial issues and trends. Clean Air Partner’s lean-burn Dual-Fuel technology includes electronic control of multi-point, port gas injection, pilot diesel timing and quantity, and lambda (excess air ratio) on a compression-ignition platform. Performance benefits include low emissions plus diesel-like efficiency, power, and torque. There are approximately 1500 CAP Dual-Fuel vehicles on the road in nine countries on four continents. Stringent environmental regulations require new approaches; CAP has developed, adopted, and acquired several technologies to meet this challenge. CAP has also transferred the core Dual-Fuel™ technology from low emissions vehicles to stationary engines for the power generation market.
3-D Shafting Calculations for Marine Installations: Static and Dynamic
Authors: Schiffer Wilfried , Jenzer Jean
Published: February 2009

Due to the particular geometry of the crankshaft of two-stroke diesel engines and the rotational degree of freedom torsional vibrations may be calculated with a 1-D mathematical model, but all other kinds of vibrations have to be calculated with a 3-D model. This concerns also static problems. In this paper the influence of coupled vibrations on ship vibration is explained and illustrated with an example for axial vibrations and an example for external vertical forces and moments. Another example for the use of the 3-D model is the calculation of crank deflection and jack load. It can be shown that such calculations are suitable for daily work.