bluuebunny/crossref_metadata_2025 huggingface dataset:
The Design, Development and Testing of a Non-Uniform Inlet Temperature Generator for the QinetiQ Transient Turbine Research Facility
Authors: Chana Kam S. , Hurrion James R. , Jones Terry V.
Published: February 2009

This paper presents the design, development and testing of a non-uniform inlet temperature generator for the QinetiQ Isentropic Light Piston Facility, a short duration turbine research facility. Major modifications were made to the facility to incorporate a non-uniform inlet temperature generator following a pilot study where a two-dimensional inlet section of the facility was replicated. The inlet region was modified to allow injection of cold gas at the hub and casing to generate the radial profile, whereas cold gas was injected from upstream turbulence rods to generate the circumferential variation (hot spots). Two configurations of hot spots were generated and characterised for both temperature and pressure. Heat transfer results at 50% span for the nozzle guide vane aerofoil are presented with and without inlet temperature non-uniformity.
Flame Ionization Sensor Integrated Into Gas Turbine Fuel Nozzle
Authors: Benson Kelly , Thornton Jimmy D. , Straub Douglas L. , Huckaby E. David , Richards Geo. A.
Published: February 2009

Recent advances in lean premix gas turbine combustion have focused primarily on increasing thermodynamic efficiency, reducing emissions, and minimizing combustion dynamics. The practical limitation on increasing efficiency at lower emissions is the onset of combustion instability, which is known to occur near the lean flammability limit. In a laboratory environment there are many sensors available which provide the combustion engineer with adequate information about flame stability, but those sensors are generally too expensive or unreliable for widespread application in the field. As a consequence, engines must be commissioned in the field with adequate stability margin such that normally expected component wear, fuel quality, and environmental conditions will not cause the turbine to experience unstable combustion. Woodward, in cooperation with NETL, is developing a novel combustion sensor which is integrated into the fuel nozzle such that low cost and long life are achieved. The sensor monitors flame ionization, which is indicative of air-fuel ratio, and most importantly flame stability.
Conceptual Investigation of a Small Reheat Gas Turbine System
Authors: Iki Norihiko , Furutani Hirohide , Takahashi Sanyo
Published: February 2009

The mirror gas turbine proposed by Tsujikawa and Fujii extends the applications of turbo machinery. The characteristic component of a mirror gas turbine is a thermal generator, which is a kind of “inverted Brayton cycle”. The operating sequence of the thermal generator is reverse that of an ordinary gas turbine, namely, the hot working fluid is first expanded, and then cooled, compressed, and finally exhausted. In this work, we investigated the theoretical feasibility of inserting a thermal generator to a small reheat gas turbine of 30–100kW classes. Using process simulator software, we calculated and compared the thermal efficiency of this reheat gas turbine to that of a micro gas turbine under several conditions, turbine inlet temperature. This comparison showed that the performances of the both gas turbines are significantly influenced by the performance of the heat exchanger used for the recuperator. The efficiency of the micro gas turbine is also improved by using water injection into the compressor to cool the inlet gas. The resulting thermal efficiency of this reheat gas turbine is about 7% higher than that of a micro gas turbine with the same power unit.
Using Probabilistics and Advanced Software Tools for Reliability and Availability Assessment and Lifting
Authors: Veer Timot , Bolland Olav
Published: February 2009

The authors aim to formulate a methodology and describe a computational tool for predicting degradation, system lifetime as well as reliability and availability (R&A) data for combustion turbines. A further goal of the present work is to put the methodological and software basis to a computer aided performance prognostic system designed for supporting R&A focused operation. In this paper we present the main theoretical basis for the module, define the necessary main concepts and their interdependencies and give an outline to the main structure of such a module. As a starting point we give an overview of the most suitable reliability criteria to be used as characterizing such a system. The authors focus on the gas turbine power plant for electricity or mechanical drive application. The authors give two different alternatives for handling the problem of predicting R&A parameters. The first one overcomes the incertitude of lack of data by combining analytic and statistic expression of the unknowns. The second is based on a time marching simulation over the unknown interim operating conditions of the system.
Application of Genetic Algorithms in the Engine Technology Selection Process
Authors: Roth Bryce , Patel Chirag
Published: February 2009

The objective of this paper is to demonstrate the application of Genetic Algorithms to the engine technology selection process. The “Technology Identification, Evaluation, and Selection” method is discussed in conjunction with Genetic Algorithm optimization as a technique to quickly evaluate the impact of various technologies and select the subset with the highest potential payoff. Techniques used to model various aspects of engine technologies are described, with emphasis on technology constraints and their impact on the combinatorial optimization of technologies. Challenges include objective function formulation and development of models to deal with incompatibilities among different technologies. Typical results are presented for an 80-technology optimization using various visualization techniques to assist in easy interpretation of Genetic Algorithm results. Finally, several ideas for future development of these methods are briefly explored.
Numerical Investigation of Casing Treatment Mechanisms With a Conservative Mixed-Cell Approach
Authors: Yang H. , Nuernberger D. , Nicke E. , Weber A.
Published: February 2009

A conservative mixed-cell approach of second-order accuracy is presented and applied to investigate the mechanisms of a self-recirculating casing treatment coupled with a transonic compressor rotor. The mixed cell is a computational cell that may show up at the zonal interface boundary, the face of which is partially solid and partially fluid, if the azimuthal open area of casing treatment does not fully contact with the whole annulus of blade passage. The mixed-cell approach is essentially an extension of the conservative zonal approach by incorporating special mixed-cell handling at the zonal interface and it allows a great flexibility to the grid generation for the patched zones with the best grid topology. The mixed-cell approach is extremely useful for solving the unsteady interaction problems within turbomachinery and its application for simulating the coupled flow through the rotor and the casing treatment is reported. The calculated results and analysis reveal an effective stall margin extension of the casing treatment herein by weakening or even destroying the tip leakage vortex, and expose the different tip flow topologies between the cases with the casing treatment and with the untreated smooth wall. It is found that the casing treatment only slightly decreases the overall efficiency at the design point, but it is beneficial to the overall efficiency at the off-design operating conditions and it can improve the inflow conditions to the downstream stator blade row as well.
Poseidon: The US Navy’s Comprehensive Health Management Software for LM2500 MGTs—Part 1
Authors: Kacprzynski Gregory J. , Krichene Assaad , Deshmukh Saurabh
Published: February 2009

This paper describes the initial features and capabilities of the US Navy’s conceptual condition monitoring software, called Poseidon, for its LM2500 Marine Gas Turbines (MGTs). Poseidon is acomprehensive suite of software modules designed to provide state-of-the-art condition monitoring, diagnostics, prognostics and maintenance reasoning for the fleet of LM2500 MGTs retrofitted with Full Authority Digital Engine Control (FADEC). Poseidon will be capable of performance and vibration diagnostics, sensor fault detection, event archiving, and maintenance reasoning in addition to specific modules for tracking Planned Maintenance System (PMS). This paper will begin with an overview of the Poseidon program and then transition to a technical discussion on the real-time engine model and performance diagnostics, sensor validation methodology, storage and trending, and vibration diagnostics. Finally, the graphical user interface and off-line analysis capabilities of Poseidon will be introduced.
Turbomachinery Flow Measurements Using Long-Nose Probes
Authors: Doukelis A. , Mathioudakis K.
Published: February 2009

The present work provides a detailed account of a pneumatic measuring technique appropriate for flow field measurements in turbomachinery configurations, making use of long-nose 5-hole probes. The way of obtaining flow quantities in a frame of reference on the sensing head of the probe is first addressed. Transformation of velocity co-ordinates from the probe frame to a stationary frame, customary for turbomachinery flows, is then discussed. Sources of error are also discussed, with particular attention on those that can be introduced by the nose geometry and the co-ordinate transformations. The potential of the measuring technique is demonstrated by presenting the application of the technique for measurements in an annular cascade facility. The results are compared to results obtained by a 3-D Laser-Doppler Anemometer.
A Comparison Between Experimental and Predicted Flow Profiles Beneath a Semi-Confined Axisymmetric Impinging Jet
Authors: Cheong C. Y. , Ireland P. T. , Ashforth-Frost S.
Published: February 2009

Theoretical predictions have been compared with experiment for a single semi-confined impinging jet. The turbulent air jet discharged at Re = 20 000 and impinged at nozzle-to-plate spacings (z/d) of 2 and 6.5. Experimental velocity profiles were obtained using hot-wire anemometry. Theoretical velocity profiles were derived using stagnation three-dimensional flow model and viscous flow model for an axisymmetric case. For z/d = 2, velocity profiles in the inviscid region of the near wall flow can be predicted accurately using the stagnation flow model. As the edge of the jet is approached, the flow becomes complex and, as expected, cannot be predicted using the model. Prediction of boundary layer profiles using the viscous flow solution for an axisymmetric case is also reasonable. For z/d = 6.5, the developing impinging jet is essentially turbulent on impact and consequently predictions of near wall flow field, using both the theoretical models, are inappropriate.
Effects of Catalytic and Dry Low NOx Combustor Turbulence on Endwall Heat Transfer Distributions
Authors: Ames F. E. , Barbot P. A. , Wang C.
Published: February 2009

Endwall heat transfer distributions taken in a large-scale low speed linear cascade facility are documented for mock catalytic and dry low NOx (DLN) combustion systems. Inlet turbulence levels range from about 1.0 percent for the mock catalytic combustor condition to 14 percent for the mock dry low NOx combustor system. Stanton number contours are presented at both turbulence conditions for Reynolds numbers based on true chord length and exit conditions ranging from 500,000 to 2,000,000. Catalytic combustor endwall heat transfer shows the influence of the complex three-dimensional flow field, while the effects of individual vortex systems are less evident for the mock dry low NOx cases. Turbulence scales have been documented for both cases. Inlet boundary layers are relatively thin for both the mock catalytic and DLN combustor cases. Inlet boundary layer parameters are presented across the inlet passage for the three Reynolds numbers and both the mock catalytic and DLN combustor inlet cases. Both midspan and 95 percent span pressure contours are included. This research provides a well-documented database taken across a range of Reynolds numbers and turbulence conditions for assessment of endwall heat transfer predictive capabilities.
Demonstration of a Reheat Combustor for Power Production With CO2 Sequestration
Authors: Chorpening Ben , Richards Geo A. , Casleton Kent , Woike Mark , Willis Brian , Hoffman Larry
Published: February 2009

Concerns about climate change have encouraged significant interest in concepts for ultra-low or “zero”-emissions power generation systems. In a concept proposed by Clean Energy Systems, Inc., nitrogen is removed from the combustion air and replaced with steam diluent. In this way, formation of nitrogen oxides is prevented, and the exhaust stream can be separated into concentrated CO2 and water streams. The concentrated CO2 stream could then serve as input to a CO2 sequestration process. In this study, experimental data are reported from a fullscale combustion test using steam as the diluent in oxy-fuel combustion. This combustor represents the “reheat” combustion system in a steam cycle that uses a high and low-pressure steam expansion. The reheat combustor serves to raise the temperature of the low-pressure steam turbine inlet, similar to the reheat stage of a conventional steam power cycle. Unlike a conventional steam cycle, the reheat enthalpy is actually generated by oxy-fuel combustion in the steam flow. This paper reports on the unique design aspects of this combustor, as well as initial emissions and operating performance.
Performance Analysis of Twin-Spool Water Injected Gas Turbines Using Adaptive Modeling
Authors: Roumeliotis I. , Aretakis N. , Mathioudakis K.
Published: February 2009

The development of an adaptive performance model for multi-spool gas turbines, equipped with the possibility of water injection is described. The model covers water injection at engine inlet, between the compressors and at the compressor exit. The selection of modification factors and the procedure for adapting component characteristics to overall performance data is discussed. A case of adaptation to overall performances is presented. The use of the model for studying overall engine and components performance is demonstrated. It is shown how operation with water injection modifies component operation, a fact that allows the identification of a wider range of the performance characteristics, in comparison to dry operation. This fact may also increase the diagnostic ability of techniques employing adaptive models. The sensitivity of diagnostic procedures to the different modes of operation of a gas turbine of the type described in the paper is also discussed.
Thermodynamic Performance of Wet Compression and Regenerative (WCR) Gas Turbine
Authors: Zheng Qun , Li Minghong , Sun Yufeng
Published: February 2009

Thermodynamic performance of wet compression and regenerative (WCR) gas turbine are investigated in this paper. The regenerative process can be achieved by a gas/air (and steam) heat exchanger, a regenerator, or by a heat recovery steam generator and then the steam injected into the gas turbine. Several schemes of the above wet compression and regenerative cycles are computed and analyzed. The calculated results indicate that not only a significant specific power can be obtained, but also is the WCR gas turbine an economic competitive option of efficient gas turbines.
Quantification and Measurement of Heavy-Duty Gas Turbine Combustion Emissions During Startup and Shutdown Operations
Authors: Willey Lawrence , Davi Michael , Smith Gordon , Almstead John , Richani Brahim , Chalfin Joel , Venkataraman Krishna
Published: February 2009

Quantification and measurement of startup and shutdown (SU/SD) emissions for heavy-duty combustion gas turbines, along with many associated significant issues, are examined in this paper. Included are the regulatory drivers that have prompted increased requests to Original Equipment Manufacturers (OEMs) from gas turbine operators, now required to account for SU/SD emissions in their power plant air permit applications. Also discussed are the complex array of influence parameters for the most popular gas turbine combustors relative to power plant installation and operability characteristics. These issues are presented along with additional background to support a recommended total mass of pollutant per SU/SD event criteria. The complexity of the Continuous Emissions Monitoring Systems (CEMS) equipment used to accurately measure transient emissions is also examined. This assessment of CEMS is designed to help gas turbine users and regulators understand the basic difficulties and complications in formulating which—if any—SU/SD emissions compliance criteria should be included in air permits.
Annular Recuperator Development and Performance Test for 200kW Microturbine
Authors: Kang Yungmo , McKeirnan Robert
Published: February 2009

Capstone Turbine Corporation developed and rig tested a new annular type primary surface recuperator for a 200kW microturbine. Rig testing was conducted for performance verification. The first development recuperator core is scheduled for assembly with a 200kW microturbine engine in 2003. This recuperator is designed using internally developed analytical and 2D & 3D CFD models. The analytical model is used to determine the heat transfer and pressure drop of the recuperator in the microturbine engine. CFD models were used to optimize the flow distributions in the recuperator core and the manifold sections. The prototype recuperator core segments were assembled and tested with the flow condition of the 200kW microturbine engine. The mass flow rate, temperatures, and pressures were measured to obtain effectiveness and pressure drops. Design goal of 90% effectiveness and 2.5% total relative pressure drop was achieved with some margin. The model predictions also agreed well with the rig test results.
Adaptive Importance Latin Hypercube Sampling
Authors: Beachkofski Brian K. , Grandhi Ramana V.
Published: February 2009

Probabilistic methods currently require many function evaluations or do not provide a mathematically robust confidence interval. The proposed method searches to find the Most Probable Point (MPP) using a Hasofer-Lind-Rackwitz-Fiessler (HLRF) algorithm, and then estimates reliability with Latin Hypercube Sampling (LHS) evaluating only those points outside of the MPP. Repeated samples provide several estimates of the reliability, which are aggregated to find a reliability estimate with a confidence interval. The computational efficiency is much better than standard LHS sampling and improves as the failure probability decreases. The method is applied to two example problems, each showing a statistically significant reduced confidence interval.
Investigation of an Inversely Designed Centrifugal Compressor Stage: Part 1 — Design and Numerical Verification
Authors: Zangeneh M. , Schleer M. , Plo̸ger F. , Hong S. S. , Roduner C. , Ribi B. , Abhari R. S.
Published: February 2009

In this paper the 3D inverse design code TURBOdesign-1 is applied to the design of the blade geometry of a centrifugal compressor impeller with splitter blades. In the design of conventional impellers the splitter blades normally have the same geometry as the full blades and are placed at mid-pitch location between the two full blades, which can usually result in a mis-match between the flow angle and blade angles at the splitter leading edge. In the inverse design method the splitter and full blade geometry is computed independently for a specified distribution of blade loading on the splitter and full blades. In this paper the basic design methodology is outlined and then the flow in the conventional and inverse designed impeller is compared in detail by using CFD code TASCflow. The CFD results confirm that the inverse design impeller has a more uniform exit flow, better control of tip leakage flow and higher efficiency than the conventional impeller. The results also show that the shape of the trailing edge geometry has a very appreciable effect on the impeller Euler head and this must be accurately modeled in all CFD computations to ensure closer match between CFD and experimental results. Detailed measurements are presented in part 2 of the paper.
Analysis of Transient Performance of a Compressed Air Energy Storage Plant
Authors: Arnulfi Gianmario L. , Marini Martino
Published: February 2009

Electrical energy storage might become a strategic topic if distributed generation will be matched with stochastic sources as wind or sun. Compressed Air Energy Storage (CAES) is one of the most promising options today: energy is stored as pressurized air in a cavern. Transient phenomena, occurring during the charging process, are analyzed in this paper. Two kinds of systems are considered with or without pressure compensation; in fact a water column can be used to link the cavern to a pond in order to compensate the pressure oscillations. A lumped parameter model has been adjusted by the authors to simulate the initial charging and the subsequent surge. The obtained results supply some insight about the safe working conditions and also the surge operation.
Foreign Object Damage of Two Gas-Turbine Grade Silicon Nitrides in a Thin Disk Configuration
Authors: Choi Sung R. , Pereira J. Michael , Janosik Lesley A. , Bhatt Ramakrishna T.
Published: February 2009

Foreign object damage (FOD) behavior of two commercial gas-turbine grade silicon nitrides, AS800 and SN282, was determined at ambient temperature through post-impact strength testing for thin disks impacted by steel-ball projectiles with a diameter of 1.59 mm in a velocity range from 115 to 440 m/s. AS800 silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness (KIC). The critical impact velocity in which the corresponding post-impact strength yielded the lowest value was Vc ≈ 440 and 300 m/s for AS800 and SN282, respectively. A unique lower-strength regime was typified for both silicon nitrides depending on impact velocity, attributed to significant radial cracking. The damages generated by projectile impact were typically in the forms of ring, radial, and cone cracks with their severity and combination being dependent on impact velocity. Unlike thick (3 mm) flexure bar specimens used in the previous studies, thin (2 mm) disk target specimens exhibited a unique backside radial cracking occurring on the reverse side just beneath the impact sites at and above impact velocity of 160 and 220 m/s for SN282 and AS800, respectively.
Robust Design Analysis of a Gas Turbine Component
Authors: Wallace Jon M. , Wojcik Stephanie , Mavris Dimitri N.
Published: February 2009

System quality and reliability are becoming increasingly more important for maintaining market place competitiveness and customer satisfaction. The objective of this paper is to demonstrate the application of the Taguchi Method as a straightforward means of improving product quality using simulation based predictions of the operating life of a critical gas turbine component. The method is applied to statistically select a set of creep life simulations that will illuminate a bucket design which is least sensitive to component and operating environment variation. Implications of this method to improving turbine component quality at the design level are discussed. The results of the Taguchi Method are compared to a robust design solution found using the more time consuming, yet more accurate Response Surface Monte Carlo method. Apparent advantages and limitations of the Taguchi method as applied to turbine component design are discussed.
Experimental Investigations Into the Nonuniform Flow in a 4-Stage Turbine With Special Focus on the Flow Equalization in the First Turbine Stage
Authors: Bohn Dieter E. , Funke Harald H.-W.
Published: February 2009

Control stage turbines are in widespread use to control turbine power output in power generation and industrial applications. Depending on the point of operation and the turbine design the inflow to the multi-stage turbine is highly non-uniform. It is important to know how the inhomogeneities in mass flow and temperature distribution develop and attenuate inside a multistage flow passage. The object of this study is to experimentally measure and report the inhomogeneous flow structure and attenuation in a multistage turbine, especially in the first turbine stage. In a scaled down original turbine consisting of a control stage with cross-over channel and a 4-stage turbine velocities, pressures and temperatures are extensively measured at the 360° circumference at the inlet, within the first stage and at the outlet of the multistage turbine part. By closing a 20% sector of the control stage a circumferential flow inhomogeneity with significant pressure, velocity and temperature gradients is created at the inlet of the multistage turbine. For analyzing the equalization of the mass flow distribution in the first stage, the experimental results are normalized with a reference case at full admission in order to separate flow phenomena created by the turbine geometry. The results show that the flow inhomogeneity at the inlet of the multistage part is significant, but the flow is basically equalized after the third stage. Most of the flow equalization takes place within the first turbine stage while the guide vane is the main driver for this process. In opposite to this the temperature inhomogeneity does not attenuate significantly within the multistage turbine part.
Application of a Bank of Kalman Filters for Aircraft Engine Fault Diagnostics
Authors: Kobayashi Takahisa , Simon Donald L.
Published: February 2009

In this paper, a bank of Kalman filters is applied to aircraft gas turbine engine sensor and actuator fault detection and isolation (FDI) in conjunction with the detection of component faults. This approach uses multiple Kalman filters, each of which is designed for detecting a specific sensor or actuator fault. In the event that a fault does occur, all filters except the one using the correct hypothesis will produce large estimation errors, thereby isolating the specific fault. In the meantime, a set of parameters that indicate engine component performance is estimated for the detection of abrupt degradation. The proposed FDI approach is applied to a nonlinear engine simulation at nominal and aged conditions, and the evaluation results for various engine faults at cruise operating conditions are given. The ability of the proposed approach to reliably detect and isolate sensor and actuator faults is demonstrated.
Three-Dimensional Conjugate Heat Transfer Simulation of an Internally-Cooled Gas Turbine Vane
Authors: York William D. , Leylek James H.
Published: February 2009

A conjugate numerical methodology was employed to predict the metal temperature of a three-dimensional gas turbine vane at two different engine-realistic operating conditions. The vane was cooled internally by air flowing through ten round, radially-oriented channels. The conjugate heat transfer approach allows the simultaneous solution of the external flow, internal convection, and conduction within the metal vane, eliminating the need for multiple, decoupled solutions, which are time-consuming and inherently less accurate when combined. Boundary conditions were specified only for the inlet and exit of the vane passage and the coolant channels, while the solid and fluid zones were coupled by energy conservation at the interfaces, a condition that was maintained throughout the iterative solution process. Validation of the methodology was accomplished through the comparison of the predicted aerodynamic loading curves and the midspan temperature distribution on the vane external surface with data from a linear cascade experiment in the literature. The superblock, unstructured numerical grid consisted of nearly seven million finite-volumes to allow accurate resolution of flowfield features and temperature gradients within the metal. Two models for turbulence closure were used for comparison: the standard k-ε model and a realizable version of the k-ε model. The predictions with the realizable k-ε model exhibited the best agreement with the experimental data, with maximum differences in normalized temperature of less than ten percent in each case. The present study shows that the conjugate heat transfer simulation is a viable tool in gas turbine design, and it serves as a platform on which to base future work with more complex geometries and cooling schemes.
Probabilistic Analysis of Geometric Uncertainty Effects on Blade Modal Response
Authors: Brown Jeffrey M. , Slater Joeseph , Grandhi Ramana V.
Published: February 2009

This paper investigates the effect of manufacturing variations on the modal response of a transonic low aspect ratio fan. A simulated set of coordinate measurement machine measurements from a single rotor, representative of actual manufacturing variations, are used to investigate geometric effects. Principal component analysis is used to statistically model spatial geometry variations and reduce variable space dimensionality. Statistics from this analysis are used with Monte Carlo sampling to generate random blades realizations that are used to predict response distributions for a simulated fleet of 1000 blades. An existing approach to approximate blade frequency response is extended to include modal displacement and stress. These approximations are based on eigensensitivity analysis and first order Taylor series approximations. An approximation error analysis is conducted to quantify accuracy. The effect of small geometry variations on blade natural frequency, mode shape, and modal stress is investigated with results showing that small variations on the order of mils can cause significant variations in both scale and location of free and forced response.
Potential and Viscous Interactions for a Multi-Blade-Row Compressor
Authors: Lee Yu-Tai , Feng JinZhang
Published: February 2009

A computationally efficient time-accurate vortex method for unsteady incompressible flows through multiple blade row systems is presented. The method represents the boundary surfaces using vortex systems. A local coordinate system is assigned to each independently moving blade row. Blade shed vorticity is determined from two generating mechanisms and convected using the Euler equation. The first mechanism of vorticity generation is a potential mechanism from a nonlinear unsteady pressure-type Kutta condition applied at the blade trailing edges. The second mechanism is a viscous mechanism from a viscous wake vorticity (VWV) model implemented to simulate the viscous shear layers on the blade pressure and suction sides. Two different two-blade-row compressor systems, a rotor/stator (R/S) system and a stator/rotor (S/R) system, were used to investigate the interaction forces on each blade row. Computational results of the potential and viscous interaction forces are presented and compared to measurements. The comparison suggests that the viscous wake interaction accounts for 25–30% of the peak loading for an axial spacing of 10% chord length between the blade rows. The efficient computational method is particularly attractive for blade indexing study. Therefore a three-blade-row rotor/stator/rotor (R1/S/R2) compressor system is used to demonstrate the indexing calculations between the two rotor positions. Resultant forces on each blade row are presented for ten rotor indexing positions and three axial gap sizes for the gaps between R1 and S and between S and R2. The unsteady peak-to-peak force can reach 10–15% of inflow dynamic head for the gap spacing investigated. The minimum-to-maximum variation of the unsteady force can account for 40–50% of averaged unsteady force.
Modeling and Cost Optimization of Combined Cycle Heat Recovery Generator Systems
Authors: Zhao Yongjun , Chen Hongmei , Waters Mark , Mavris Dimitri N.
Published: February 2009

The combined cycle power plant is made up of three major systems, the gas turbine engine, the heat recovery steam generator and the steam turbine. Of the major systems the gas turbine engine is a fixed design offered by a manufacturer, and the steam turbine is also a fairly standard design available from a manufacturer, but it may be somewhat customized for the project. In contrast, the heat recovery steam generator (HRSG) offers many different design options, and its design is highly customized and integrated with the steam turbine. The objective of this project is to parametrically investigate the design and cost of the HRSG system, and to demonstrate the impact on the overall cost of electricity (COE) of a combined cycle power plant. There are numerous design parameters that can affect the size and complexity of the HRSG, and it is the plan for the project to identify all the important parameters and to evaluate each. For this study, the design parameter chosen for evaluation is the exhaust gas pressure drop across the HRSG. This parameter affects the performance of both the gas turbine and steam turbine and the size of the heat recovery unit. Single-pressure, two-pressure and three-pressure HRSGs are all investigated, with the tradeoffs between design point size, performance and cost evaluated for each system. A genetic algorithm is used in the design optimization process to minimize the investment cost of the HSRG. Several system level metrics are employed to evaluate a design. They are gas turbine net power, steam turbine net power, fuel consumption of the power plant, net cycle efficiency of the power plant, HRSG investment cost, total investment cost of the power plant and the operating cost measured by the cost of electricity (COE). The impacts of HRSG exhaust gas pressure drop and system complexity on these system level metrics are investigated.
Assessment of RQL Trapped Vortex Combustor for Stationary Gas Turbines
Authors: Straub Douglas L. , Casleton Kent H. , Lewis Robie E. , Sidwell Todd G. , Maloney Daniel J. , Richards Geo. A.
Published: February 2009

This paper describes the evaluation of an alternative combustion approach to achieve low emissions for a wide range of fuel-types. This approach combines the potential advantages of a staged Rich-burn, Quick-mix, Lean-burn (RQL) combustor with the revolutionary Trapped Vortex Combustor (TVC) concept. Although RQL combustors have been proposed for low-BTU fuels, this paper considers the application of an RQL combustor for high-BTU natural gas applications. This paper will describe the RQL/TVC concept and experimental results conducted at 10 atmospheres (1013 kPa or 147 psia) and an inlet-air temperature of 644K (700°F). The results from a simple network reactor model using detailed kinetics are compared to the experimental observations. Neglecting mixing limitations, the simplified model suggests that NOx and CO performance below 10 parts-per-million could be achieved in an RQL approach. The CO levels predicted by the model are reasonably close to the experimental results over a wide range of operating conditions. The predicted NOx levels are reasonably close for some operating conditions, however, as the rich-stage equivalence ratio increases, the discrepancy between the experiment and the model increases. Mixing limitations are critical in any RQL combustor, and the mixing limitations for this RQL/TVC design are discussed.
Effect of the Exit System on the Performance of a Low Specific Speed Industrial Centrifugal Compressor Stage
Authors: Di Liberti Jean-Luc
Published: February 2009

A low specific speed stage was tested with two different size volutes and a return vane system. The stage was instrumented with pressure probes at various locations, including the inlet and discharge flanges, diffuser inlet, diffuser exit, and return vane inlet. Cobra probes were positioned at the diffuser inlet and the return vane inlet for the return vane configuration to measure the flow angles. High frequency transducers were installed in the diffuser. This paper presents the test results showing the effect of two different volute sizes and of the return vane system on surge margin, rotating stall onset, and overall rotor and stage performance. Rotating stall criteria are reviewed, since this stage was previously tested with a different diffuser pinch. The performance is compared with some CFD analysis.
Aerodynamic and Thermo-Chemical Assessment of a Post-Catalyst Burnout Zone Liner
Authors: Nickolas Sarento G. , Vilayanur Suresh R. , Spencer Mark J. , Watts Anthony , Hamer Andrew
Published: February 2009

A Kawasaki Heavy Industries M1A-13X engine equipped with a Xonon® Cool Combustion System was used to assess the “effectiveness” of a post-catalyst burnout zone liner. The engine is currently installed at the City of Santa Clara’s Silicon Valley Power municipal electrical generating stations and connected to the grid. Post-catalyst burnout zone liner aero-thermal design and inlet boundary conditions play an important role in achieving low CO emissions. In this particular study, these parameters have been evaluated to minimize CO emissions (by maximizing CO burnout). An aero thermal analysis was conducted using Computational Fluid Dynamics (CFD) simulations of the liner for two distinct engine configurations. The analysis includes characterization of the inlet boundary conditions, heat transfer analysis, ignition delay time, liner residence time and the aerodynamic flow field. In addition, engine tests were used to measure and evaluate the impact of design features on CO emissions. Tests were conducted using new seal design and catalyst liner interface configurations. Results from both of these investigations were then used to determine the “effectiveness” of the liner. The CFD analysis and engine test data identified potential regions of improvement to maximize CO burnout in the Burn out Zone (BOZ) liner. These improvements included changing the inlet boundary conditions as well as modifying the BOZ geometry. Ultimately, a solution scheme was selected and changes were made to the catalyst seal design as well as the catalyst to container interface. Upon implementation, these changes yielded an improved effectiveness and extended the operating range of the engine by minimizing CO emissions.
Performance of a Novel Semi-Closed Gas Turbine Refrigeration Combined Cycle
Authors: Boza Joseph J. , Lear William E. , Sherif S. A.
Published: February 2009

A thermodynamic performance analysis was performed on a novel cooling and power cycle that combines a semi-closed gas turbine called the High Pressure Regenerative Turbine Engine (HPRTE) with an absorption refrigeration unit. Waste heat from the recirculated combustion gas of the HPRTE is used to power the absorption refrigeration cycle, which cools the high-pressure compressor inlet of the HPRTE to below ambient conditions and also produces excess refrigeration depending on ambient conditions. Two cases were considered: a small engine with a nominal power output of 100kW, and a large engine with a nominal power output of 40 MW. The cycle was modeled using traditional one-dimensional steady-state thermodynamics, with state-of-the-art polytropic efficiencies and pressure drops for the turbo-machinery and heat exchangers, and curve-fits for properties of the LiBr-water mixture and the combustion products. The small engine was shown to operate with a thermal efficiency approaching 43% while producing 50% as much 5°C refrigeration as its nominal power output (roughly 50 tons) at 30 °C ambient conditions. The large engine was shown to operate with a thermal efficiency approaching 62% while producing 25% as much 5°C refrigeration as its nominal power output (roughly 20,000 tons) at 30 °C ambient conditions. Thermal efficiency stayed relatively constant with respect to ambient temperature for both the large and small engine. It decreased by only 3–4% as the ambient temperature was increased from 10 to 35 °C in each case. The amount of external refrigeration produced by the engine decreased sharply in both engines at around 35 °C, eventually reaching zero at roughly 45°C in each case for 5°C refrigeration. However, the evaporator temperature could be raised to 10°C (or higher) to produce external refrigeration in ambient temperatures as high as 50°C.
Field Methods for Identification of Bearing Support Parameters: Part II — Identification From Rotor Dynamic Response Due to Imbalances
Authors: De Santiago Oscar C. , San Andre´s Luis
Published: February 2009

This paper describes a procedure suitable for field implementation that allows identification of synchronous bearing support parameters (force coefficients) from recorded rotor responses to imbalance. The experimental validation is conducted on a test rotor supported on two dissimilar bearing supports, both mechanically complex, each comprising a hydrodynamic film bearing in series with a squeeze film damper and elastic support structure. The identification procedure requires a minimum of two different imbalance distributions for identification of force coefficients from the two bearing supports. Presently, the test rotor responses show minimal cross-coupling effects, as also predicted by analysis, and the identification procedure disregards cross-coupled force coefficients thereby reducing its sensitivity to small variations in the measured response. The procedure renders satisfactory force coefficients in the speed range between 1,500 and 3,500 rpm, enclosing the rotor-bearing system first critical speed. The identified direct force coefficients are in accordance with those derived from the impact load excitations presented in a companion paper [1].
Incipient Fault Detection and Diagnosis in Turbine Engines Using Hidden Markov Models
Authors: Menon Sunil , Uluyol O¨nder , Kim Kyusung , Nwadiogbu Emmanuel O.
Published: February 2009

Incipient fault detection and diagnosis in turbine engines is key to effective maintenance and improved availability of systems dependent on these engines. In this paper, we present a novel method for incipient fault detection and diagnosis using Hidden Markov Models (HMMs). In particular, we focus on engine faults that are manifest in transient operating conditions such as engine startup and acceleration. HMMs are stochastic signal models that are effective in modeling transient signals. They are developed with engine data collected under nominal operating conditions. Engine data representing different fault conditions are used to develop the fault HMMs; a separate model is developed for each of the faults. Once the nominal and fault HMMs are developed, new engine data collected from the engine are evaluated against the HMMs and a determination is made whether a fault is indicated. Here, we demonstrate our HMM-based fault detection and diagnosis approach on engine speed profiles taken from a real engine. Further, the effectiveness of the HMM-based approach is compared with a neural-network-based approach and a method based on using principal component analysis in conjunction with a neural network approach.
Applicability of Temperature Sensitive Paints for Measurement of Surface Temperature Distribution
Authors: Liu Q. , Kapat J. S. , Douglass C. J. , Qiu J.
Published: February 2009

Temperature sensitive fluorescent paints (TSP) provide a non-intrusive method for surface temperature measurement. The objective of this research is to identify application and operational parameters that have impact on the TSP calibration curve and demonstrate the method on a jet impingement experiment. In particular, the effects of painting process and lighting and viewing conditions are reported in this paper. TSPs are made by dissolving a polymer and fluorophore in a common solvent. The resulting liquid can be sprayed or brushed onto a surface. A calibration procedure and apparatus have been devised to calibrate the emission intensity of the fluorescent paints as a function of temperature. TSP has been calibrated between room temperature and 63°C. It is found that over this temperature range, calibration curves are within ± 0.8°C of each other irrespective of the number of paint coats (provided at least 3 coats are applied) and viewing and lighting angles. The TSP technique has been applied to a hot jet impinging on a transparent acrylic plate. The impingement side of the acrylic plate is coated with TSP that determines the instantaneous surface temperature distribution. The target plate was placed at 6 jet diameters from the nozzle. The temperature distribution obtained from the TSP clearly shows the stagnation area and flow transition of jet impingement flow.
Aerodynamic and Aeroacoustic Performance of a Skewed Rotor
Authors: Cai Na , Xu Jianzhong , Benaissa Azemi
Published: February 2009

This paper presents an experimental investigation and numerical simulation of the aerodynamic and aeroacoustic performance of an axial-flow fan with skewed rotating blades in the design and off-design operation. The blade is designed with a forward skew angle for which the stacking line is directed towards the rotating direction on the circumferential section. A detailed investigation of a three-dimensional flow field in the inter-blade row and passage using five-hole probes and a hot-wire anemometer at the upstream and downstream locations of the rotors has been carried out and compared with a fan with unskewed rotor blades. Noise testing was performed in the anechoic chamber. The experiments were performed at three rotating speeds. Aerodynamic curves show that the performance of the skewed blade increased at a higher pressure rise of 13.1% and gave a larger flow rate of about 5% and a higher efficiency of more than 3%. The higher efficiency in the skewed rotor was due to the practical and advantageous spanwise redistribution of aerodynamic parameters, a greater boundary movement into the main flow, a secondary flow reduction and the thinness of the rotor wake. Aeroacoustic performance and frequency spectra in almost the whole frequency domain showed a noise reduction of 2 to 4 dBA in the skewed fan. Lower noise in the skewed blade comes from the broadband noise reduction owing to a thinner wake layer, a phase difference in rotor radiation and tip leakage noise reduction. A wider stall margin for more than 20% is obtained in the skewed blade due to the proportional distribution of aerodynamic parameters. The three-dimensional Navier-Stokes approach is simulated in the inner blade flow.
Feasibility Analysis for the Rotordynamic Performance of API617
Authors: Ahn Hyeong-Joon , Maslen Eric H. , Iwasaki Tetsuya
Published: February 2009

The rotordynamic performance of API 617 standards provides two primary requirements. First, the standard stipulates system damping near the expected operating speed range. Second, the standard requires a specific bound of the worst case unbalance response. The problem this poses for machine designers is 1) feasibility: can bearings be designed for a given rotor to meet API 617 and 2) if so, how can these bearings be designed? Our primary effort in this research is to convert the API requirements to a control design objective for a bearing. This permits direct assessment of the feasible design problem as well as providing a means to synthesize optimal bearing dynamics. In addition to providing synthesis of magnetic bearings, the resulting bearing transfer functions give direct guidance to selection of more conventional fluid film or rolling element bearings.