bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and Numerical Investigation on Performance and Flow in the Last Stage Group of a Wet Steam Turbine
Authors: Yang Jiandao , Yang Rui , Shi Liqun , Yang Hong , Li Jun
Published: September 2014

To investigate the performances of the last stage of a huge power and half-rotation speed nuclear steam turbine, a 3-stage wet steam turbine performance test rig is designed. Experiments are carried out to test the performances of the modeled turbine at design and off-design operating points. Frozen-rotor steady-state computations are performed on design point as well as off-design operating points. The calculated massflow rate, power and efficiency are validated with the experimental data and the flow details are discussed. Steam humidity, temperature and pressure are compared with the tested results. With the detailed 3D flow results derived with numerical simulations, it is found that for the investigated steam turbine, the performances of the first two stages only changes slightly when turbine operation point changes, meanwhile, the aerodynamic quantity distribution characteristics also keep nearly almost the same. However, for the last stage, both efficiency and flow details changes significantly when operating point changes. It is also found that for the last stage, flow region with maximum steam humidity is located at downstream of stator near hub and downstream of blade near tip, where water droplets mostly likely to be formed and accumulated.
Model Analysis of Syngas Combustion and Emission for a Micro Gas Turbine
Authors: Liu Chi-Rong , Shih Hsin-Yi
Published: September 2014

The purpose of this study is to investigate the combustion and emission characteristics of syngas fuels applied in a micro gas turbine, which is originally designed for a natural gas fired engine. The computation results were conducted by the commercial CFD software STAR-CD, where the three-dimension compressible k-ε model for turbulent flow and PPDF (Presumed Probability Density Function) model for combustion process were constructed. As the syngas are substituted for methane, the total heat input from the blended fuels and the fuel flow rates are varied with syngas compositions and syngas substitution percentages. The computed results presented the syngas substitution effects on the combustion and emission characteristics at different syngas percentages (up to 80%) for two typical syngas compositions and the conditions where syngas applied at fixed heat input were examined.

Results showed the flame structures varied with different syngas substitution percentages. The high temperature regions were dense and concentrated on the core of the primary zone for H2-rich syngas, and then shifted to the sides of the combustor when syngas percentages were high. The NOx emissions decreased with increasing syngas percentages, but NOx emissions are higher at higher hydrogen content for the same syngas percentage. The CO2 emissions also decreased at 10% syngas substitution, but then increased as syngas percentage increased. Only using H2-rich syngas could produce less carbon dioxide. The detailed flame structures, temperature distributions, and gas emissions of the combustor were presented and compared. The exit temperature distributions and pattern factor were also discussed. Before syngas fuels are utilized as an alternative fuel for the micro gas turbine, further experimental testing are needed as the CFD modeling results provide a guidance for the improved designs of the combustor.
Mullite Whisker Reinforced Zirconia Toughened Alumina for High Temperature Applications
Authors: Robertson Taylor , Huang Xiao , Kearsey Richard
Published: September 2014

Particulate enhanced oxide ceramics are an attractive class of materials for high temperature applications because they possess many of the high temperature capabilities of monolithic ceramics but also have enhanced mechanical properties due to their multi-phase structure. High temperature structural ceramics have the potential to operate above at higher temperatures than current super alloys; however, processing costs and lack of reliability has prevented their commercialization. In this work a particulate reinforced ceramic composed entirely of oxides is proposed as a more oxidation resistant and cost effective structural ceramic which will have potentially improved resistance to environmental degradation. Zirconia Toughened Alumina (ZTA), as the matrix, has enhanced toughness, strength, and creep resistance over single phase alumina or zirconia. ZTA can further be strengthened by the incorporation of SiC type whiskers; however, these whiskers are prone to deterioration at temperatures above 1000°C through oxidation. In this work Mullite, in whisker form, is proposed as the reinforcement to ZTA due to its stability in oxidizing atmospheres at high temperatures. Mullite whiskers are grown through the molten salt method and incorporated into the ZTA matrix using a colloidal processing route in this study. The composition of the ZTA matrix is 15wt% Yttria stabilized Zirconia (YSZ), 85 wt% α-Alumina. The Mullite whiskers make up 20 vol% of the composite, yielding a final composition of 71.6 wt% Alumina, 12.7 wt% YSZ, and 15.6 wt% Mullite. The green compacts are fired in a two stage sintering process incorporating atmospheric pressure sintering to 92% density (seal the pore channels) and then hot isostatic pressure pressing (HIP) to increase the density. Samples have been tested for room temperature flexural strength using a three point bend test and fracture toughness through Gong’s Vickers indentation method. The results of microstructure study and mechanical tests are reported in this paper.
Accuracy Research on the Modeling Methods of the Gas Turbine Components Characteristics
Authors: Peng Shuhong , Sun Bo , Ying Yulong , Wu Keliang , He Lei , Xu Qiang
Published: September 2014

In the process of a gas turbine performance simulation based on component characteristics, the accuracy description of components characteristics is a significant element which affects the accuracy of the results, especially for part-load and startup performance calculation.

For the traditional modeling method of components, the discrete characteristic maps was integrated into the thermodynamic model in the form of arrays, which present the relationships among IGV opening angle γ, speed, pressure ratio and flow/efficiency of compressor, as well as the relationships among speed, pressure ratio and flow/efficiency of turbine. It’s obvious that fine discrete grids are required in this traditional interpolating method to obtain enough data to reflect the original information accurately. However, the characteristic maps obtained are always sparse, which lead to considerable interpolation error.

With regard to poor accuracy of traditional component characteristics method, we integrate partial least square (PLS) method into reconstructing the components characteristic curves. It doesn’t need the discretization of component characteristic maps, and the reconstruction equation can be solved directly in the simulation process, which avoids the interpolation errors in the traditional processing methods of component characteristics.

The traditional method, BP artificial neural network, PLS of two variables and ternary PLS of three variables was implemented in performance simulation of the same gas turbine. The simulation results of components characteristics and gas turbine thermodynamic performance with different methods were compared with the known performance data of the gas turbine. And the calculation accuracies and their effects on overall performance were analyzed. The implement of PLS in component characteristics simulation could be useful for improving the accuracy of the gas turbine thermodynamic model, and could benefit for gas turbine power plant upgrades and technology improvement because thermodynamic mode is the base of on-line monitoring and fault diagnosis system.
Effect of Airfoil Clocking on Noise of LP Turbines: Part II — Modal Structure Analysis
Authors: Serrano Adolfo , Fernández José Ramón
Published: September 2014

The clocking effect on noise is investigated experimentally in a multistage turbine high speed rig. It consists in a three stages state of the art Low Pressure Turbine (LPT). The work is a continuation of a first part in which efficiency and noise are addressed together for the same test [1]. Due to the large amount of data acquired in the experiment, noise results presented in [1] are based on averaged Sound Pressure Level (SPL) at the exit. The present paper goes beyond that analysis and aims to get the modal structure and its sensitivity to clocking.

Noise measurements are taken ‘in-duct’ immediately downstream the LPT by a continuously and slowly rotating device denominated Noise Measurement Module (NMM). Previous experimental studies [2] [3] demonstrate this as an effective way of characterizing the LPT noise source in an engine, provided that the necessary hot to cold conversions and propagation effects are included.

The rotation of the NMM allows the identification of the spinning modes responsible of the tone noise. The axial dependence acquired by the different sensors along the duct gives the radial structure of the spinning modes. The modal decomposition allows the estimation of the acoustic energy, which is the proper magnitude for observing the clocking dependence. The data reduction process from time history signals to the acoustic power estimation is described in detail. Special attention is paid on the applicability limits and uncertainty analysis.

Results from the first part [1] suggest that efficiency is weakly affected by clocking whereas noticeable influence of some tone noise is observed. The acoustic power and modal structure dependence of the same tones observed in [1] will allow the comprehension of the noise clocking mechanisms in future. Although this is out of the scope, results suggest some physical explanation described here.
Auto-Tuning of Real-Time Dynamic Gas Turbine Models
Authors: Panov V.
Published: September 2014

Real-time gas turbine engine models are integral part of techniques such as model-based control and diagnostics. The use of model based techniques to diagnose and adaptively manage degradation of engine components is crucial for operational effectiveness of gas turbines. Since the gas turbine model represents “nominal” engine, it must be adapted or tuned to the performance of the real engine as it deviates from nominal baseline. Implementation of a method for auto-tuning of dynamic gas turbine engine models was considered in this paper, and a non-linear physics based component level model was facilitated as an on-line gas turbine model. Real-time nonlinear dynamic model of an industrial twin-shaft gas turbine with tracking filter was deployed onto the dedicated hardware platform and integrated with the engine control system.

In presented application the identified gas turbine health parameters were obtained by the performance estimation tool and included in the observer design. The designed observer detects changes in the engine health parameters and generates model tuners. The model tuning process based on Kalman filtering technique was applied to secure robust execution of real-time dynamic models.

Proposed auto-tuning methodology provides a tool for model adaptation, capable of addressing abrupt and gradual degradation of engine performance and at the same time offers a means for model compensation of performance deviation caused by engine-to-engine variation.

Although most of performance tracking and diagnostic methods are developed for gas turbine operating at steady state, current trend demonstrates increasing interest in diagnostics during transient operation. Devised method estimates dynamic behaviour of gas turbine health parameters enabling in that way performance tracking under transient conditions. Examples of model adaptation during gas turbine engine transient operation are given in the paper.
Unsteady Flow Structure in an Axial Compressor at Windmill Condition
Authors: Goto Takashi , Kato Dai , Ohta Yutaka , Outa Eisuke
Published: September 2014

This study investigates experimentally and numerically unsteady flow fields in an axial compressor operating at high-flow rate in order to understand the flow structure in the stator row operating at windmill condition. The experimental and numerical data are compared by time- and phase-lock-averaged techniques. Additionally, unsteady vortex structure is investigated by numerical technique. At windmill condition, the incidence angle to the stator row becomes extremely negative. Therefore, large separation occurs near pressure surface in the stator passage. The experimental and numerical results indicate that a large vortex is generated in the separation area. According to the numerical results, part of the vortex migrates downstream, and the vortex produces blockage of the main stream of the stator passage. Therefore, net flow area in the stator passage becomes small so that the flow between the vortex and suction side of stator vane is accelerated. As a result, the total pressure deterioration is generated in the stator passage because the high speed flow and the vortex cause high shear.
Rotating Stall Observations in a High Speed Compressor: Part 1 — Experimental Study
Authors: Dodds J. , Vahdati M.
Published: September 2014

In this two part paper the phenomenon of part span rotating stall is studied. The objective is to improve understanding of the physics by which stable and persistent rotating stall occurs within high speed axial flow compressors. This phenomenon is studied both experimentally (part 1) and through the use of unsteady RANS simulations (part 2).

In this paper, the behaviour of an 8 stage high speed compressor is studied during slow acceleration manoeuvres along a fixed working line. Casing mounted pressure transducers and rotor mounted strain gauges are used to examine the spectral content of any unsteadiness in the flow and its behaviour across the operating range.

By deliberate aerodynamic mismatching of the front stages through adjustment of three rows of variable stator vanes, stable rotating stall is initiated. The observed behaviour falls into two ‘families’ of high and low frequency when tracked on the instrumentation. Further analysis based on the Doppler shift between the static and rotating measurements confirms that these respective phenomena are due to rotating stall of high and low cell count. Acoustic modes resulting from stall/rotor interaction are also identified.

Strong correlation of the stall intensity with simple 1D meanline predicted loading parameters suggests that these families of behaviour are independently linked to the stalling of different regions within the compressor.
Numerical Investigation of Axial Compressor Stages With Differing Degrees of Reaction
Authors: Ortmanns Jens
Published: September 2014

In order to increase the efficiency of a compressor module, several loss sources such as aerofoil profile loss, secondary loss and clearance flow phenomena must be taken into account and balanced in the most efficient way. This current document presents the results of a numerical investigation based on a conventionally loaded high pressure compressor stage with different inlet and exit swirls. The effects of changing the degree of reaction on the compressor stage flow pattern is analysed in detail. In general, the correlation between the overall stage efficiency at constant pressure ratio and the degree of stage reaction is low. Nevertheless, the results show a direct impact on the rotor tip leakage flow and the secondary flow phenomena in the stator end-wall region when the degree of reaction is modified which is driven by the change in static pressure rise between the rotor and the stator passages. The balance of these two loss sources might have an impact on the efficiency and the stall behaviour of a multi-stage compressor.
Turbine Endwall Contouring for the Reduction of Endwall Heat Transfer Using the Ice Formation Method Along With Computational Fluid Dynamics
Authors: Winkler Sven , Haase Kristian , Brucker Janosch , Weigand Bernhard
Published: September 2014

Turbine endwall contouring has become very popular for optimizing gas turbines. Increasingly often, three-dimensional contours are applied between turbine airfoils to reduce aerodynamic losses or heat transfer rates. These reductions directly result from the shaping of such contours which modifies the flow and thermal field in their vicinity. Here, we report on the development of novel endwall contours for a generic low pressure vane profile to reduce endwall heat transfer. Using the flat endwall as baseline, different endwall contours were created using the Ice Formation Method. This natural approach imposes only minimum restrictions on the design space and is therefore considered advantageous to other optimization procedures. The created contours were subsequently analyzed by Computational Fluid Dynamics simulations. Results showed that all created contours reduced endwall heat transfer compared to the baseline, the highest reduction being 7% in terms of the averaged endwall Stanton number. For this endwall contour, we performed detailed analyses of the numerically predicted flow and temperature fields to indicate how the shaping of this contour affects the flow and temperature fields and hence causes the observed heat transfer reduction.
Application of Planar Laser-Induced Phosphorescence to Investigate Jet-A Injection Into a Cross-Flow of Hot Air
Authors: Tan Zu Puayen , Lubarsky Eugene , Bibik Oleksandr , Shcherbik Dmitriy , Zinn Ben T.
Published: September 2014

This paper describes the development of the Planar Laser-Induced Phosphorescence (PLIP) technique for mapping the fuel temperature and concentration distributions in a jet-in-cross-flow (JICF) spray study. The spray was produced by injecting cold liquid Jet-A into hot cross-flowing air. The application of PLIP required the seeding of liquid fuel with micron-size thermographic phosphor particles before injection. The resulting spray produced phosphorescence and droplets Mie-scattering signals when illuminated by a 355nm planar UV laser sheet of 0.054J/pulse energy. The technique was investigated as a potential alternative to the use of Jet-A Planar Laser-Induced Fluorescence (PLIF) for the mapping of fuel concentration in sprays, because the low signal intensity of Jet-A’s fluorescence at high T prevents the use of the PLIF approach. In contrast, PLIP provides a strong signal at high T, and allows the simultaneous determination of local T and fuel concentration when two spectral bands of the phosphorescence emission are imaged and their ratio-of-intensities (RI) determined. In addition, the locations where liquid fuel droplets exist were imaged from the UV Mie-scattering of the laser-sheet (which can also be done in PLIF).

In the present investigation, an optical system that imaged two spectral bands of phosphorescence and one wavelength of Mie-scattering was developed. It consisted of three CCD cameras with dichroic beam-splitters and interference narrow bandpass filters. The spray-pattern within a span of ∼80×30 orifice diameters was captured, with spatial resolution of about 0.1mm/px. The investigated jet-in-cross-flow spray was produced by injecting Jet-A fuel from a 0.671mm diameter orifice located on the wall of a rectangular channel (25.4×31.75mm cross-section). The cross-flow air was preheated to temperatures encountered in modern gas turbines (up to 480°C), while the temperature of the injected Jet-A fuel was in the T = 27–80°C range. YVO4:Eu phosphor particles with a median size of 1.8 microns were used to seed the fuel.

Since the emissions of the commonly used Dy:YAG thermographic phosphor were found to be too weak and had wavelengths that overlapped with Jet-A fluorescence signals, YVO4:Eu was used for the JICF studies instead. It was observed that while the emissions of YVO4:Eu were stronger than Dy:YAG, the range of T where it can be applied in the PLIP technique was more limited — just sufficient for the investigated JICF. Preliminary results from the study showed rapid changes in fuel concentration and T from the injector up to z/dinj∼30 for momentum ratios of J = 5, 10 and 20, followed by a more gradual mixing/heat-up downstream. It was also found that deposition of phosphor particles on channel-walls interfered with the spray characterization, reducing the accuracy of the measurements.
Combination of Active and Passive Flow Control in a High Speed Compressor Cascade
Authors: Liesner Karsten , Meyer Robert
Published: September 2014

An experimental study is presented in which passive and active flow control are combined in a way that they complement and support one other. Secondary flow control using boundary layer fences is combined with a boundary layer suction in a compressor cascade at high Mach numbers. Inflow Mach number of 0.67 and Reynolds number (based on chord length) of 560.000 assure realistic conditions. The cascade, equipped with five stator vanes of NACA65 K48 type is used in an ambient condition measurement environment. Pressure measurements form the basis of the experimental investigations, flow visualization is used to obtain insight into the topology of the flow field.

The boundary layer fences installed on the suction side of the vanes create a region of low-loss two dimensional flow in the center of the passage. A region of high flow loss is generated at the side wall between wall and BL fence. This region is treated with through-wall boundary layer suction as used in previous investigations. This helps stabilize the flow near the wall and prevent large separated areas. The total pressure loss is reduced remarkably and the outflow becomes more two-dimensional compared to the reference measurement and even compared to the measurement with suction applied without BL fences. The application of boundary layer fences on flow-suction experiments allows obtaining the same loss reduction gains by using lower amounts of suction.
High-Pressure Compressor Blade Dynamics Under Aerodynamic and Blade-Tip Unilateral Contact Forcings
Authors: Batailly Alain , Legrand Mathias , Millecamps Antoine , Garcin François
Published: September 2014

Recent studies focused on the numerical prediction of structural instabilities that may arise in rotating components of an aircraft engine. These instabilities are commonly classified into two categories: those induced by aerodynamic phenomena (such as the pressure applied on the blade by the incoming air flow) and those related to structural phenomena (such as potential blade/casing contacts). Based on an existing numerical strategy for the analysis of rotor/stator interactions induced by unilateral contacts between rotating and static components, this paper aims at combining both types of instabilities and provides a qualitative analysis of structural interactions that may arise within the high-pressure compressor of an aircraft engine. The aerodynamic pressure on the blade is simplified as a sinusoidal external load whose frequency depends on the number of upstream guide vanes. Results are presented both in time and frequency domains. Detailed bifurcation diagrams and Poincaré maps underline the fundamental differences in the nature of the witnessed interactions with and without aerodynamic loading on the blade.
Experimental Testing of Carbon Brush Seals for Aero Engines Bearing Chambers
Authors: Outirba Bilal , Hendrick Patrick
Published: September 2014

This paper provides the first step in sizing carbon brush seals for aero-engine oil bearing chambers applications.

Recent developments in the aeronautic domain focus strongly on the reduction of aero-engine specific oil consumption. For instance, optimizing the civil aircraft gas turbine engine lubrication oil system is considered as one of the main targets in this research. Specifically, brush seals have shown tremendous leakage performance in sealing secondary flows compared to classic labyrinth seals over the last few decades. Therefore, an attractive idea is to extent their utilization to oil bearing chamber applications.

To perform the experimental part of the study, a test rig has recently been built at ULB. This test rig will be described in this paper. A parametrical study has been performed in stationary conditions, and at very low rotation speed. A particular attention was given to the air consumption and the torque friction losses. Finally, a test simulating the effects of a rotor excursion on the brush seal performance has been made.
Development and Implementation of Alternative Repair Processes for Reconditioning of Fr7FA+e, 1st Stage Nozzles
Authors: Miglietti Warren , Summerside Ian
Published: September 2014

The 60 Hz, Frame 7F engine has been in commercial operation for more than two decades now with approximately 800 Frame 7 (F, FA, FA+ and FA+e models) machines existing in North America and a total of over 1100 F-class machines throughout the world. Of importance to operators/users and owners of this gas turbine engine is the ability to not only recondition the turbine “hot-end section” components, in order to support maintenance requirements, but also to reduce the life cycle costs of these components.

Stage 1 nozzles are a cast doublet, manufactured from FSX-414 Co-based superalloy. There are 24 nozzles in an engine set. As a result of the extreme turbine inlet temperatures at the 1st stage nozzle, these components experience severe thermal fatigue cracking. On one particular OEM engine set inspected, over 600 cracks were identified on each nozzle after engine operation. As a consequence, the stage 1 nozzles when compared to the other components in the engine exhibits the worst degradation and is therefore a focus point of reconditioning for those in the industry.

The technical objective is to describe the development of a repair scheme for the stage 1 nozzle that can successfully address and repair this level of severe cracking and oxidation, with 0% scrap/fallout for a heavy repair, after a normal duty cycle. Special processes have been established for these components repairs, including but not limited to removal of the damaged and oxidized trailing edges by machining, high frequency Gas Tungsten Arc Welding (GTAW) of new trailing edge coupons.

This technical paper describes the repair process development and implementation of the different stages of the repair schemes and shows metallurgical and mechanical characteristics of the repaired regions of the component. As a result of successfully executing these special processes, although a heavy repair workscope was implemented; all the nozzles were successfully repaired without any scrap.
Wind Turbine Gearbox Planetary Stage Gear Damage Detection Using Vibration Data
Authors: Hanna Jesse , Luo Huageng
Published: September 2014

Effective vibration based condition monitoring applied to the planetary stage of a wind turbine gearbox has been historically difficult. Numerous complications associated with the low speed and variable speed nature of a wind turbine gearbox as well as the many sources of vibration signal modulation and poor vibration transmission paths within the planetary stage itself have presented complex challenges around effectively monitoring the health of planetary stage components. The focus of this paper is the vibration behavior of planetary stage gear related damage and how this behavior can be accurately identified using vibration data. The theory behind this behavior and a case history showing the successful detection of planet gear damage and ring gear damage is presented. The damage detailed in this case is clearly identifiable in the data provided by the ADAPT.Wind condition monitoring system. Although this type of damage requires a gearbox replacement, prompt detection is important to avoid the risk of splitting the gearbox casing and damaging additional wind turbine components.
Scaling of Film Cooling Performance From Ambient to Engine Temperatures
Authors: Greiner Nathan J. , Polanka Marc D. , Rutledge James L.
Published: September 2014

The present study employs Computational Fluid Dynamics (CFD) to explore the complexities of scaling film cooling performance measurements from ambient laboratory conditions to high temperature engine conditions. In this investigation, a single shaped hole is examined computationally at both engine and near ambient temperatures to understand the impact of temperature dependent properties on scaling film cooling performance. By varying select flow and thermal parameters for the low temperature cases and comparing the results to high temperature flow, the parameters which must be matched to scale film cooling performance are determined.

The results show that only matching the density and mass flux ratios is insufficient for scaling to high temperatures. In accordance with convective heat transfer fundamentals, freestream and coolant Reynolds numbers and Prandtl numbers must also be matched to obtain scalable results. By virtue of the Prandtl number for air remaining nearly constant with temperature, the Prandtl number at ambient conditions is sufficiently matched to engine temperatures. However, laboratory limitations can prevent matching both the freestream and coolant Reynolds numbers simultaneously.

By examining this trade-off, it is determined that matching the coolant Reynolds number produces the best scalability. It is also found that by averaging the adiabatic effectiveness of two experiments in which the freestream and coolant Reynolds number are matched respectively results in significantly better scalability for cases with a separated coolant jet.
Analysis of Middle Bearing Failure in Rotor Jet Engine Using Tip-Timing and Tip-Clearance Technique
Authors: Rokicki Edward , Majewski Paweł , Rzadkowski Romuald , Szczepanik Ryszard , Spychała Jarosław , Drewczyński Marcin
Published: September 2014

The reported problem is the failure of the middle bearing in an aircraft rotor engine. Tip-timing and tip-clearance and variance analyses are carried out on a compressor rotor blade in the seventh stage above the middle bearing. The experimental analyses concern both an aircraft engine with a middle bearing in good working order and an engine with a damaged middle bearing. A numerical analysis of the seventh stage blade free vibration are conducted to explain the experimental results. This appears to be an effective method of predicting middle bearing failure. The blade vibration variance increases when there is bearing failure.
Improvement of Flat-Plate Film Cooling Performance by Double Flow Control Devices: Part I — Investigations on Capability of a Base-Type Device
Authors: Funazaki Ken-ichi , Nakata Ryota , Kawabata Hirokazu , Tagawa Hisato , Horiuchi Yasuhiro
Published: September 2014

This paper deals with effects of double flow control devices (DFCDs) on flat plate film cooling performance. Aiming for further improvement of film effectiveness of discrete cooling holes, this new type of controlling method is invented and recently patented by the authors. The performance of base-type DFCDs, installed just upstream of cooling holes with conventional round or fan-shaped exits, is thoroughly investigated and reported in this study. Effects of the hole pitch are examined. Three hole-pitch cases, 3.0d, 4.5 d and 6.0 d are examined in this study to explore a possibility of reducing the cooling air by the application of DFCDs, where d is a hole diameter. In order to investigate the film effectiveness, a transient method using a high-resolution infrared camera is adopted. At the downstream of the cooling hole, the time-averaged temperature field is captured by a thermocouple rake and the time-averaged velocity field is captured by 3D Laser Doppler Velocimeter (LDV), respectively. Furthermore, the aerodynamic loss characteristics of the cooling hole with and without DFCDs are measured by a total pressure probe rake. The experiments are carried out for two blowing ratios, 0.5 and 1.0. It is found that DFCDs are quite effective in increasing the film effectiveness not only for round but also the fan-shaped holes.

Starting from the base-type device, a robust optimization using Taguchi Method has been made by the present authors and will be reported as Part II.
Experimental Study of Effects of Bowed Blade on the Flow Field in a Cantilevered Stator Passage
Authors: Luo Ju , Hu Jun , Wang Zhiqiang , Tu Baofeng
Published: September 2014

This paper presents experimental investigation conducted on a 2-stage low speed axial research compressor with cantilevered stator vanes. Flow fields at four different axial locations in the radial stacking and bowed stator passage were measured at maximum flow point and near stall point using 4 five-hole pressure probes. The aim of the work is to study the effects of the bowed stators with hub clearance on the flow field of compressor blade passage. The investigations were conducted with the first stage of the compressor. The hub clearances of both original and bowed stators are 1.1% of span. The results show that the scale of the separation vortex, the hub leakage vortex and the lower passage vortex in the bowed blade passage becomes much smaller and the hub leakage vortex is closer to the suction side at near stall point, which causes a much smaller mixing loss in the blade passage.
Combined Effects of Perforated Blockages and Pin Fins in a Trailing Edge Internal Cooling Duct
Authors: Kan Rui , Ren Jing , Jiang Hongde
Published: September 2014

Pin fin arrays and perforated blockages are both important methods for gas turbine trailing edge cooling. Perforated blockages result in higher heat transfer coefficients with larger pressure loss penalty. For enhanced heat transfer with medium pressure loss, we installed a perforated blockage at the inlet of pin fin arrays and studied the combined effects between impingement and pin fin. Heat transfer coefficients were measured with the transient liquid crystal method and the lumped capacitance model. Flow field was investigated using the RNG k-ε model. Six configurations with different flow area ratio, hole distribution and hole aspect ratio were examined at duct Reynolds number between 9,000 and 20,000. The results reveal that under impingement condition, Nusselt number for the first two rows of pin fins near the stagnation point is 2∼3 times larger than the baseline case without impingement. The most important parameter for heat transfer and friction loss is the area ratio. The average Nusselt number increases 20%∼50% with impingement, and the friction factor increases 4∼20 times. Heat transfer and friction loss for the combined configurations satisfy the correlation Nu = 0.1766Re0.702f0.188.
Experimental Investigations of SYCEE Film Cooling Performance on a Plate and a Tested Vane of an F-Class Gas Turbine
Authors: Han Chang , Ren Jing , Jiang Hongde
Published: September 2014

Film cooling is widely used in modern gas turbines for the protection of the hot components against hot gases from the combustion process. Film cooling directly influences the thermal efficiency of the gas turbine, as the cooling gas is extracted from the compressor and mixed with the mainstream in the hot component. Huge efforts by industry as well as research organizations have been undertaken to improve the film cooling effectiveness. It can been concluded that there are two key points for the improvement of film cooling effectiveness, constraining the blow-off of cooling ejection and extending the lateral coverage of cooling gas. The paper presents a new cooling technology, which reaches high film-cooling effectiveness as a result of a well-designed cooling hole, named SYCEE film cooling technology (SFCT). Plate film cooling experiments of SYCEE tested by pressure sensitive paint (PSP) are carried out in this work, and traditional shape-hole are included as well for baselines. It is resulted that SFCT has a better film cooling performance than shape-hole in the same conditions, and the gap of the averaged film cooling effectiveness between them continuously enlarges as the blowing ratio increases.

Furthermore, an application of SFCT on the first stage vane of an F-class gas turbine is studied as well. A two-dimension cascade has been employed to measure the cooling performance of SFCT using pressure sensitive paint (PSP) as well, and the tested vanes separately with round-hole and shape-hole are considered again for baselines. The different kinds of film holes separately locate on the pressure and suction side, while the showerhead in different cases are kept the same, arranged with round-holes. The cooling air is ejected at inclination angle 45° with compound-angle 90° in the showerhead and inclination angle 35°∼45° without compound-angle on the pressure side and suction side. The detailed local cooling effectiveness distributions as well as the span-averaged effectiveness over the vane surface are presented. As expected, the film cooling performance of round-hole is the worst due to the lift-off of the cooling ejection. SFCT has better film cooling performance than shape-hole on the pressure side, but the advantage decreases along the mainstream direction. However, the span-averaged film cooling effectiveness of SYCEE is similar with that of the shape-hole on the suction side. This may be due to enhanced impact of mainstream flow derived from the pressure gradient in the turbine passage, and consequently weakening the effect of film hole on the suction side.
Effect of CO2 Capture on Combined Cycle Gas Turbine Efficiency Using Membrane Separation, EGR and OEA Effects on Combustion Characteristics
Authors: Cabot G. , Calbry M. , Xavier P. , Vandel A. , de Persis S. , Belaissaoui B. , Favre E. , Pillier L.
Published: September 2014

In an energetic world of fossil fuel, there is a need to reduce the CO2 emission released to the atmosphere. CO2 Capture and Sequestration (CCS) is one of the solutions.

To optimize the CO2 capture cost, thermodynamic cycles of power plants have to be modified, and resulting new designs inevitably lead to new combustion modes [1][2][3]. CO2 capture of post combustion gases can be performed using membrane processes, but its efficiency is interesting only if the CO2 concentration in the combustion process exhaust gases is higher than 30% [4]. Unfortunately, in classical combustion processes (e.g. gas turbine), diluted Exhaust Gases (EG) contain no more than 5 % of CO2 because combustion products are strongly diluted in air. Our objective consists in increasing the EG CO2 concentration, by using both Oxygen-Enriched Air (OEA) combustion and exhaust gas recirculation (EGR). Our approach is based on numerical simulations and on experimental work. First, operating parameters which minimize the CO2 capture cost are calculated and compared with the reference capture cost [5] (achieved by amine absorption of CO2). In parallel, experiments and additional calculations are performed in order to check the quality and the operability of such combustion mode.

This paper is organized as follows: the first part presents the optimization of a new thermodynamic GTCC cycle, using OEA and EGR to increase EG CO2 concentration and capturing it in post-combustion with membrane separator. The effects of pressure and membrane selectivity will be studied in terms of CO2 capture cost, avoided CO2, implemented membrane surface, EGR rate and OEA quality.

The second part is dedicated to the experimental and calculation [6] studies of combustion met in this type of configuration. A premixed swirl flame is fed first with Air, CH4 and CO2, then with OEA, CH4 and EGR. To neglect the thermal aspect of NOx production, measurements are performed at constant adiabatic flame temperature. The flame structure, combustion instability and pollutant emissions are presented as a function of the EGR rate dilution.
Sequential vs Multidisciplinary Coupled Optimization and Efficient Surrogate Modelling of a Last Stage and the Successive Axial Radial Diffuser in a Low Pressure Steam Turbine
Authors: Cremanns Kevin , Roos Dirk , Graßmann Arne
Published: September 2014

In order to meet the requirements of rising energy demand, one goal in the design process of modern steam turbines is to achieve high efficiencies. A major gain in efficiency is expected from the optimization of the last stage and the subsequent diffuser of a low pressure turbine (LP). The aim of such optimization is to minimize the losses due to separations or inefficient blade or diffuser design. In the usual design process, as is state of the art in the industry, the last stage of the LP and the diffuser is designed and optimized sequentially. The potential physical coupling effects are not considered. Therefore the aim of this paper is to perform both a sequential and coupled optimization of a low pressure steam turbine followed by an axial radial diffuser and subsequently to compare results. In addition to the flow simulation, mechanical and modal analysis is also carried out in order to satisfy the constraints regarding the natural frequencies and stresses. This permits the use of a meta-model, which allows very time efficient three dimensional (3D) calculations to account for all flow field effects.
Simultaneous Robust Design and Tolerancing of Compressor Blades
Authors: Dow Eric A. , Wang Qiqi
Published: September 2014

The manufacturing processes used to create compressor blades inevitably introduce geometric variability to the blade surface. In addition to increasing the performance variability, it has been observed that introducing geometric variability tends to reduce the mean performance of compressor blades. For example, the mean adiabatic efficiency observed in compressor blades with geometric variability is typically lower than the efficiency in the absence of variability. This “mean-shift” in performance leads to increased operating costs over the life of the compressor blade. These detrimental effects can be reduced by using robust optimization techniques to optimize the blade geometry. The impact of geometric variability can also be reduced by imposing stricter tolerances, thereby directly reducing the allowable level of variability. However, imposing stricter manufacturing tolerances increases the cost of manufacturing. Thus, the blade design and tolerances must be chosen with both performance and manufacturing cost in mind.

This paper presents a computational framework for performing simultaneous robust design and tolerancing of compressor blades subject to manufacturing variability. The manufacturing variability is modelled as a Gaussian random field with non-stationary variance to simulate the effects of spatially varying manufacturing tolerances. The statistical performance of the compressor blade system is evaluated using the Monte Carlo method. A gradient based optimization scheme is used to determine the optimal blade geometry and distribution of manufacturing tolerances.
Film Cooling With Swirling Coolant Flow on a Flat Plate and the Endwall of High-Loaded First Nozzle
Authors: Takeishi Kenichiro , Oda Yutaka , Kondo Shinpei
Published: September 2014

This paper describes an experimental study on the film cooling effectiveness of circular and fan-shaped film cooling holes with a swirling film coolant injected through a flat plate and the endwall of a high-loaded first nozzle. The experiments were conducted using a flat plate wind tunnel and a two-dimensional vane cascade, which is designed based on the first-stage vane of an Energy Efficient Engine (E3) studied under a NASA project. The film cooling effectiveness on a flat plate wind tunnel and the endwall of the enlarged first nozzle of the E3 turbine was measured using pressure sensitive paint (PSP) techniques. The experimental results indicate that the film cooling effectiveness of a circular hole improved by increasing the angle θ of two impinging jets inside the cavity, which are used both for cooling the internal wall and generating a swirling motion in the film coolant. In contrast, it was found that there exist optimal jet angles of θ = 20° for a circular film cooling hole, θ = 5–10° for a flat plate wind tunnel test, and θ = 15° for the cascade test conducted using a fan-shaped film cooling hole. Thus the new film cooling method using swirling cooling air has been demonstrated to maintain high film cooling effectiveness even under such a complicated flow field.
Investigation on Material’s Creep Strength Variation Among Different Locations of Directional Solidified Turbine Blades
Authors: Zhang Kai , Yan Xiaojun
Published: September 2014

In order to obtain higher creep strength, the Directional Solidification (DS) Nickel-based turbine blades have been widely used in aero engines, because this advanced casting technology can improve the blade’s creep performance along the principal stress direction by forming columnar grains parallel to this direction. However, the grain structures at different regions of turbine blade are likely to be different, because the temperature field during casting process is affected by the different abrupt geometrical changes. Therefore, a variation in the creep performances at these regions is caused. To study the variation in creep strength among different regions of a DS turbine blade, this work designed and manufactured three types of DS specimens which have the geometry features of the platform, the shroud and the body part of DS turbine blade. Creep tests on these specimens were conducted under a stress level of 608MPa and temperature of 850 °C. The creep rupture life of platform-like and shroud-like specimens are about 93% and 73% of that of the body-like specimen respectively, which support that there exists a certain variation of creep strength among different regions in a DS turbine blade. It is suggested that the material’s creep strength variation among different locations of DS turbine blades should be considered in future turbine blade life design and prediction.
Co-Firing of Hydrogen and Natural Gases in Lean Premixed Conventional and Reheat Burners (Alstom GT26)
Authors: Wind Torsten , Güthe Felix , Syed Khawar
Published: September 2014

Addition of hydrogen (H2), produced from excess renewable electricity, to natural gas has become a new fuel type of interest for gas turbines. The addition of hydrogen extends the existing requirements to widen the fuel flexibility of gas turbine combustion systems to accommodate natural gases of varying content of higher hydrocarbons (C2+). The present paper examines the performance of the EV and SEV burners used in the sequential combustion system of Alstom’s reheat engines, which are fired with natural gas containing varying amounts of hydrogen and higher hydrocarbons. The performance is evaluated by means of single burner high pressure testing at full scale and at engine-relevant conditions.

The fuel blends studied introduce variations in Wobbe index and reactivity. The latter influences, for example, laminar and turbulent burning velocities, which are significant parameters for conventional lean premixed burners such as the EV, and auto-ignition delay times, which is a significant parameter for reheat burners, such as the SEV. An increase in fuel reactivity can lead to increased NOx emissions, flashback sensitivity and flame dynamics. The impact of the fuel blends and operating parameters, such as flame temperature, on the combustion performance is studied. Results indicate that variation of flame temperature of the first burner is an effective parameter to maintain low NOx emissions as well as offsetting the impact of fuel reactivity on the auto-ignition delay time of the downstream reheat burner. The relative impact of hydrogen and higher hydrocarbons is in agreement with results from simple reactor and 1D flame analyses. The changes in combustion behaviour can be compensated by a slightly extended operation concept of the engine following the guidelines of the existing C2+ operation concept and will lead to a widened, safe operational range of Alstom reheat engines with respect to fuel flexibility without hardware modifications.