bluuebunny/crossref_metadata_2025 huggingface dataset:
Researches Concerning Kerosene-to-Landfill Gas Conversion for an Aero-Derivative Gas Turbine
Authors: Popescu Jeni A. , Vilag Valeriu A. , Petcu Romulus , Silivestru Valentin , Stanciu Virgil
Published: January 2011

The aero-derivative gas turbine represents an advanced solution for technologic transfer from aeronautics to industrial applications, including high efficiency, reduced dimensions and high reliability. The paper, as result of a research project, is focused on an application using an aero-derivative gas turbine as an installation for CO2 rich landfill gas valorization. The paper also presents the potential for landfill gas production in Romania, in the context of the requirements imposed by the environmental laws. A calculation is realized based on demographic statistics, showing the most suitable areas in the country for obtaining the landfill gas. The first part is dedicated to a comparative examination of classical liquid fuel, kerosene, and two gaseous fuels, methane and landfill gas with equal volume ratio of methane and carbon dioxide, analyzed from the point of view of their combustion performances in the gas turbine, with the help of CEA program developed by NASA. Considering the nowadays utilization of CFD simulations for design purpose in many activity fields from the engineering domain, the results provided by the CEA program, along with the ones provided by the gas turbine’s producer, were considered input data for the numerical approaches of the combustion process of methane and landfill gas in the known combustion chamber using a commercial CFD code. The main goal of the CFD applications is to determine the optimum geometric configuration of the new injection system in order to obtain a stabilized process and high performances in safety conditions, for low working regimes and nominal regime, as defined by experimental data and producer’s recommendations. Previous successful experimentations on test bench following the combustion simulation of methane gas and the encouraging results from the CFD simulations lead to new experimentations of the gas turbine working on landfill gas in order to validate the numerical approaches, activity described in the third part of the paper. A technological fueling scheme was designed, the geometrical adjustments were made according to previous simulations and the landfill gas was simulated using a homogenization device installed on the fuel line for a forced mixing of the two non-reactive substances, methane and carbon dioxide. The gas turbine was prepared and instrumented for bench testing and stable working was obtained for speeds of 27–63% of the nominal one. The conclusions are related to the execution of an installation allowing experimentation of gas turbines working on landfill gas and future researches focusing on tests for higher working regimes.
Analytical Approach of TMF Prediction for Complex Loading
Authors: Ahdad Farid , Kannusamy Ragupathy , Damodharan B.
Published: January 2011

Many critical components in turbocharger are subjected to rapid temperature changes during operations. Thermal gradient within these components produces internal stresses and the repetition of these thermal cycles may cause a component to fail due to Thermal Mechanical Fatigue (TMF). Turbine Wheel, Turbine Housing and Manifold are subjected to TMF; these are the most expensive components of the turbocharger and have very complex geometric shapes. The maximum exhaust gas temperature could reach 1050°C. To assess TMF failure, it is very critical to accurately estimate metal temperature of these components subjected to complex duty cycles where exhaust gas temperatures vary significantly with time. Evaluating metal temperature and stress components from finite element analysis for complex duty cycles is a very time consuming process, particularly for complex geometries and approximately requires more than 3 weeks of time to complete analysis for different field complex duty cycles (driving conditions: city, highway and road). Several of these analysis cases are required to consider the impact of the real driving condition. In the present work we have developed an analytical methodology that is accurate and faster to predict the metal temperature and stresses in turbocharger components for complex duty cycles. This method was applied to evaluate the fatigue damage of turbine housing under actual condition.
Fully-Cooled Single Stage HP Transonic Turbine: Part II—Influence of Cooling Mass Flow Changes and Inlet Temperature Profiles on Blade and Shroud Heat-Transfer
Authors: Haldeman C. W. , Dunn M. G. , Mathison R. M.
Published: January 2011

A fully cooled transonic HP turbine stage is utilized to investigate the combined effects of turbine stage cooling variation and vane inlet temperature profile on heat transfer to the blades with the stage operating at the proper design corrected conditions. For this series of experiments, both the vane row and the blade row were fully cooled. The matrix of experimental conditions included varying the cooling flow rates and the vane inlet temperature profiles to observe the overall effect on airfoil heat-transfer. The data presented in Part I focused on the aerodynamics of the fully cooled turbine for a subset of the cases investigating two vane inlet temperature profiles (uniform and radial), and three different cooling levels (none, nominal and high) for the high Reynolds number condition. This part of the paper focuses on the time-average heat-flux measurements on the blade and shroud region for the same cooling mass flow rates and vane inlet temperature profiles. The cooling effects are shown to be small and are centered primarily on the suction side of the airfoil. This relatively small influence is due to the ratio of the cooling gas to metal temperature being closer to 1 than the design value would dictate. The vane inlet temperature profile effects are more dominant, and using a Net Stanton Number Reduction Factor to compare the cases, an effect on the order of about 0.25 is demonstrated. This effect is due primarily to the change in the reference temperature used for the Stanton number calculation. The differences due to profile effects are small, but observable towards the trailing edge of both the blade and rotor shroud. This data set forms an excellent baseline for heat-flux calculations, as the variation in the main input conditions are well documented and do not produce large changes in the heat-flux. It provides insight into the flow physics of an actual engine and guidelines about proper normalization of variables for a cooled turbine stage, supporting further development of computational heat-flux modeling techniques.
Fully-Cooled Single Stage HP Transonic Turbine: Part I—Influence of Cooling Mass Flow Variations and Inlet Temperature Profiles on Blade Internal and External Aerodynamics
Authors: Haldeman C. W. , Dunn M. G. , Mathison R. M.
Published: January 2011

A fully cooled turbine stage is utilized to investigate the combined effects of turbine stage cooling variation and HPT vane inlet temperature profile on the aerodynamics and heat transfer of the turbine stage operating at the proper design corrected conditions. Part I of this paper describes the overall experimental matrix, the influence of the cooling mass flows, and temperature profiles from an aerodynamic perspective. The measurements include internal and external pressures for the blade airfoil. Part II of this paper focuses on the influence of these parameters on the heat transfer to the blade airfoil and the stationary blade shroud. The major results show that cooling levels do not significantly affect the external pressure distributions over the majority of the blade and vane. However, aerodynamic effects of cooling levels and temperature profiles are seen for the vane and blade pressure loading on the suction surfaces. The magnitude of these effects range from 5 to 10% of the local measurement for the reference case, which is the uniform inlet profile with nominal cooling for this study. Inlet temperature profiles and cooling levels have comparable impacts on pressure loading, but their relative influence changes with location, Reynolds number and corrected speed variations have the lowest impact on pressure loading changes, with changes below 5% of the local measurements. Another important result is that unlike un-cooled experiments, the proper normalizing variable for pressures aft of the vane is not the inlet pressure but a “Rotor Reference Pressure”, which adjusts the total inlet pressure by the increase in pressure resulting from the additional cooling mass flows. For the rotor, this consists primarily of the vane trailing edge cooling flows. This simplified model accounts for the effects of the vane cooling, and isolates the changes due to blade cooling. The spread of the cooling flows through the stage is important to the surface heat flux, and has an impact on pressure loadings on the suction surface. The data establishes important guidelines for modelers of cooling flows. The changes observed on the suction side of the airfoils are real, but quite small from an engineering design perspective. Thus the pressure levels are stable and relatively independent of cooling levels, which is critical for good heat-transfer predictions.
Effects of Combustion Chamber Geometry Deviations Upon Exit Temperature Profiles for Populations With Varied Service Limitations
Authors: Kotzer Clayton , LaViolette Marc , Allan William , Asghar Asad
Published: January 2011

The purpose of this continuing research was to investigate the effects of combustion chamber geometry on exit temperature fields using a validated ambient pressure test rig. Rig test conditions were set to simulate an engine operating condition of 463 km/h (250 knots) at 7 620 m (25,000 ft) by matching Mach number, equivalence ratio and Sauter mean diameter of the fuel spray. Using a thermocouple rake, high resolution temperature measurements were obtained in the combustion chamber exit plane. Following the previously published procedures, a three-dimensional laser scanning system was used to quantify geometric deviations from two populations of combustion chambers. These populations differed in that one had a significantly higher allowable engine operating temperature for continuous cruise condition. Geometric deviations of both populations were compared to the reference model. The relationship between combustion chamber exit temperature profile and geometric deviation of each population was then compared. The main conclusion of this research was that the temperature profile degradation of both populations due to geometric deviations followed similar trends. These results highlighted that the difference in operating limitations of these populations did not significantly affect component performance.
Flashback Propensity of Syngas Flames at High Pressure: Diagnostic and Control
Authors: Daniele S. , Jansohn P. , Boulouchos K.
Published: January 2011

Nowadays, the establishment of IGCC (integrated gasification combined cycle) plants, prompts a growing interest in synthetic fuels for gas turbine based power generation. This interest has as direct consequence the need for understanding of flashback phenomena for premixed systems operated with H2-rich gases. This is due to the different properties of H2 (e.g. reactivity and diffusivity) with respect to CH4 which lead to higher flame speeds in the case of syngases (mixtures of H2-CO). This paper presents the results of experiments at gas turbine like conditions (pressure up to 15 bar, 0.2 < Φ < 0.7, 577K < T0 < 674K) aimed to determine flashback limits and their dependence on the combustion parameters (pressure, inlet temperature and inlet velocity). For the experimental facility used for this work the back propagation of the flame is believed to happen into the boundary layer of the fuel/air duct. Flashback propensity was found to have an appreciable dependence on pressure and inlet temperature while the effects of inlet velocity variations are weak. Explanations for the dependence on these three parameters, based on consideration on laminar and turbulent flame speed data (from modeling and experiments), are proposed. Within the frame of this work, in order to avoid major damages, the experimental facility was equipped with an automatic control system for flashback described in the paper. The control system is able to detect flame propagation into the fuel/air supply, arrest it and restore safe operating conditions by moving the flame out of the fuel/air section without blowing it out. This avoids destruction of components (burner/mixing) and time consuming shut downs of the test rig.
A New Type of Self-Adaptive Casing Treatment for a Centrifugal Compressor
Authors: Wang Tong , Xu Wei , Gu Chuangang , Xiao Jun
Published: January 2011

Enhancing compressor stall and surge margin is very important for the development of turbo compressors. Casing treatment is an effective method to expand the stall margin and thus the stable operation range but it generally comes with a drop in efficiency. A new type of casing treatment with self-adaptivity for an unshrouded centrifugal impeller is presented in this paper. The idea of the self-adaptive casing treatment is to automatically control the bleeding flow rate through a set of round holes on the stationary shroud casing. When stall is approached, the casing treatment system will redirect the low-momentum fluid to improve the flow in the impeller and to extend its stable range. However, the system will not bleed or bleed a little flow when the operating point is far from the stall point. This decreases the bleeding-recirculation loss and increases the efficiency compared to bleed-slot casing treatment used before. The experimental results show that the centrifugal compressor with the new casing treatment can extend stable range by about 20% while the efficiency over the whole operating range increases by 0.2 to 1.5%. The theoretical results using CFD analyses agree with the experimental ones in the tendency for both pressure ratio and efficiency. Moreover some possible reasons for further enhancing the stable range are suggested in the paper. Based on our experiences, there should be existed a proper combination of impeller rotating speed, position and numbers of bleed port and other parameters that will maximize both surge margin range and efficiency.
Gas Turbine Starting Systems Used Aboard U.S. Navy Large Surface Combatants
Authors: Greve Alex C. , Miller Nathaniel P. , Shaw Jesse D.
Published: January 2011

There are various methods used to start marine gas turbine engines on large naval surface combatants. Methods include pneumatic, mechanical, hydraulic, and electric starting systems. This paper gives an overview of basic starting requirements, describes each method used on large surface combatants, and identifies which systems are used on many of the U.S. Navy surface combatants.
CFD Simulation of Biomass Pyrolysis Syngas vs. Natural Gas in a Microturbine Annular Combustor
Authors: Fantozzi Francesco , Laranci Paolo , Bidini Gianni
Published: January 2011

Biomass to energy conversion is particularly attractive on the microscale were internal combustion engines such as microturbines may be utilized coupled to an indirect gasification system. The authors have developed the IPRP technology based on rotary kiln pyrolisys and a pilot plant was built in Italy powered by an 80 kWEl microturbine fired by pyrolysis biomass syngas. This paper describes CFD numerical investigations carried out to study the combustion process occurring inside the annular rich-quick-lean combustion chamber of the given microturbine. A RANS analysis has been performed in order to simulate both natural gas and syngas combustion. A mechanisms based on two reduced and detailed chemical kinetic were taken into account and applied to carry out the CFD simulations. The numerical results obtained for NG are presented and compared with the experimental data on emission to validate the numerical assumptions. The combustion mechanism are used also in pyrolysis gas combustion case to investigate the operation of the microturbine fuelled with this biomass derived fuel.
Wake Control by Boundary Layer Suction Applied to a High-Lift Low-Pressure Turbine Blade
Authors: Satta Francesca , Ubaldi Marina , Zunino Pietro , Schipani Claudia
Published: January 2011

Wake control by boundary layer suction has been applied to a high-lift low-pressure turbine blade with the intention of reducing the wake velocity defect, hence attenuating wake-blade interaction, and consequently the generation of tonal noise. The experimental investigation has been performed in a large scale linear turbine cascade at midspan. Two Reynolds number conditions (Re = 300000 and Re = 100000), representative of the typical operating conditions of the low pressure aeroengine turbines, have been analyzed. Boundary layer suction has been implemented through a slot placed in the rear part of the profile suction side. The suction rate has been varied in order to investigate its influence on the wake reduction. Mean velocity and Reynolds stress components in the blade to blade plane have been measured by means of a two-component crossed miniature hot-wire. The wake shed from the central blade has been investigated in several traverses in the direction normal to the camber line at the cascade exit. The traverses are located at distances ranging between 5 and 80% of the blade chord from the blade trailing edge. To get an overall estimate of the wake velocity defect reductions obtained by the application of boundary layer suction, the integral parameters of the wake have been also estimated. Moreover, spectra of the velocity fluctuations have been evaluated to get information on the unsteady behaviour of the wake flow when boundary layer suction is applied. The results obtained in the wake controlled by boundary layer suction have been compared with the results in the baseline profile wake at both Reynolds number conditions for the purpose of evaluating the control technique effectiveness. The removal of boundary layer through the slot in the rear part of the profile suction side has been proved to be very effective in reducing the wake shed from the profile. The results show that a reduction greater than 65% of the wake displacement and momentum thicknesses at Re = 300000, and a reduction greater than 75% at Re = 100000 can be achieved by removal of 1.5% and 1.8% of the single passage through flow, respectively.
Experiments on the Transient Performance of an Adaptive Multi-Objective Controller for Rotating Machinery
Authors: Sahinkaya M. Necip , Abulrub Abdul-Hadi G. , Keogh Patrick S. , Burrows Clifford R.
Published: January 2011

The paper describes an experimental assessment of the transient performance of a multi-objective adaptive approach to the control of flexible rotors previously presented by the authors. The approach is applicable to any form of controllable bearings or actuators. In the case reported here, the rotor is supported by active magnetic bearings (AMBs). The theory underlying the controller is outlined: the objectives include minimization of the forces transmitted to the base while restricting rotor vibrations to a user-defined limit. A third objective is to prevent rotor contact with the auxiliary bearings used to protect the active elements. These three objectives are met by a two-stage weighting strategy followed by the adaptive control of two parameters that automatically and continuously adjust the weightings of individual objective functions to satisfy user defined performance criteria.
Effect of Combustor Inlet Geometry on Acoustic Signature and Flow Field Behavior of the Low Swirl Injector
Authors: Therkelsen Peter L. , Littlejohn David , Cheng Robert K. , Portillo J. Enrique , Martin Scott M.
Published: January 2011

Low Swirl Injector (LSI) technology is a lean premixed combustion method that is being developed for fuel-flexible gas turbines. The objective of this study is to characterize the fuel effects and influences of combustor geometry on the LSI’s overall acoustic signatures and flowfields. The experiments consist of 24 flames at atmospheric condition with bulk flows ranging between 10 and 18 m/s. The flames burn CH4 (at φ = 0.6 & 0.7) and a blend of 90% H2 - 10% CH4 by volume (at φ = 0.35 & 0.4). Two combustor configurations are used, consisting of a cylindrical chamber with and without a divergent quarl at the dump plane. The data consist of pressure spectral distributions at five positions within the system and 2D flowfield information measured by Particle Imaging Velocimetry (PIV). The results show that acoustic oscillations increase with U0 and φ. However, the levels in the 90% H2 flames are significantly higher than in the CH4 flames. For both fuels, the use of the quarl reduces the fluctuating pressures in the combustion chamber by up to a factor of 7. The PIV results suggest this to be a consequence of the quarl restricting the formation of large vortices in the outer shear layer. A Generalized Instability Model (GIM) was applied to analyze the acoustic response of baseline flames for each of the two fuels. The measured frequencies and the stability trends for these two cases are predicted and the triggered acoustic mode shapes identified.
Concept for a Phosphorescent Thermal History Sensor
Authors: Rabhiou A. , Feist J. , Kempf A. , Skinner S. , Heyes A.
Published: January 2011

The thermal history of hot surfaces is of great practical importance, but very hard to measure. Thermal indicating paints offer one possible and practical way, but they have many disadvantages. A novel concept for the utilisation of phosphorescent coatings as thermal history sensors has been proposed by Feist et al. [1] in 2007. These phosphor coatings undergo irreversible changes when exposed to high temperatures that affect their light emission properties. A subsequent off-line analysis of the emission at room temperature can reveal the temperature history of the coating. In this paper, an investigation of the amorphous-to-crystalline change of Y2SiO5: Tb is reported and used to provide a proof of concept for a phosphorescent thermal history sensor. The phosphor powder was calcined at different temperatures, and characterised using photoluminescence spectroscopy. A calibration curve was generated from the measurements and is presented and discussed.
Experimental and Numerical Cross-Over Jet Impingement in an Airfoil Trailing-Edge Cooling Channel
Authors: Taslim M. E. , Nongsaeng A.
Published: January 2011

Trailing edge cooling cavities in modern gas turbine airfoils play an important role in maintaining the trailing edge temperature at levels consistent with airfoil design life. In this study, local and average heat transfer coefficients were measured in a test section simulating the trailing edge cooling cavity of a turbine airfoil using the steady-state liquid crystal technique. The test rig was made up of two adjacent channels, each with a trapezoidal cross sectional area. The first channel, simulating the cooling cavity adjacent to the trailing-edge cavity, supplied the cooling air to the trailing-edge channel through a row of racetrack-shaped slots on the partition wall between the two channels. Eleven crossover jets, issued from these slots entered the trailing-edge channel and exited from a second row of race-track shaped slots on the opposite wall in staggered or inline arrangement. Two jet angles were examined. The baseline tests were for zero angle between the jet axis and the trailing-edge channel centerline. The jets were then tilted towards one wall (pressure or suction side) of the trailing-edge channel by five degrees. Results of the two set of tests for a range of local jet Reynolds number from 10,000 to 35,000 were compared. The numerical models contained the entire trailing-edge and supply channels with all slots to simulate exactly the tested geometries. They were meshed with all-hexa structured mesh of high near-wall concentration. A pressure-correction based, multi-block, multi-grid, unstructured/adaptive commercial software was used in this investigation. Standard high Reynolds number k–ε turbulence model in conjunction with the generalized wall function for most parts was used for turbulence closure. Boundary conditions identical to those of the experiments were applied and several turbulence model results were compared. The numerical analyses also provided the share of each cross-over and each exit hole from the total flow for different geometries. The major conclusions of this study were: a) except for the first and last cross-flow jets which had different flow structures, other jets produced the same heat transfer results on their target surfaces, b) jets tilted at an angle of 5 degrees produced higher heat transfer coefficients on the target surface. The tilted jets also produced the same level of heat transfer coefficients on the wall opposite the target wall and c) the numerical predictions of impingement heat transfer coefficients were in good agreement with the measured values for most cases thus CFD could be considered a viable tool in airfoil cooling circuit designs.
CFD Methods for Shear Driven Liquid Wall Films
Authors: Hashmi Amir A. , Dullenkopf Klaus , Koch Rainer , Bauer Hans-Jo¨rg
Published: January 2011

Shear driven liquid wall films or physically similar two phase flow phenomena can be found in a number of different industrial and engineering applications. Gear boxes, bearing chambers or combustors in aero engines, heat exchanger ducts, oil and gas production and transport in petrochemical industry are just a few examples where this phenomenon is present and has been studied for decades. The most common approach of modeling shear driven film flows consist of empirical correlations derived from simple experiments. This approach is reasonable but highly case dependent. The problem lies in the difficulty of achieving experimental data for cases of practical importance. For a more global approach in this respect, CFD can be a useful tool. Therefore the study presented in this paper is dedicated to explore the potential of modern CFD methods. All available multiphase flow models are analyzed for their applicability for subcritical shear driven wall films (no mass transfer, no droplet shedding/deposition from/to film). VOF is suggested to be the only available multiphase flow model applicable to shear driven flows. However, further investigations have revealed that VOF method in its original form is not suitable for the flow conditions leading to high interaction between the phases i.e. where the motion of slow moving heavier phase is dictated by the fast moving lighter phase. This shortcoming in the VOF method is explained by means of a false momentum transfer between the phases. The focus then turns to find the improvement possibilities in the VOF method. Two approaches can be found in literature addressing the improvement possibilities in VOF method. The approach of physically justified modification of the turbulence quantities at the gas-liquid interface is adopted in this paper and is referred to as interface treatment. The approach is applied to a simple test case where the liquid phase acts as a wall. The results achieved for this test case are compared to the validation data where remarkable improvements are observed when compared to the VOF method without interface treatment. The interface treatment is then applied to a case of more practical importance where improvements are clearly evident again. Due to the lack of quantitative information on the interfacial waves, outlet boundary conditions cannot be well defined at this point. Therefore the later case is only seen as a motivation for further investigation of this approach.
Novel Joint Time Frequency Vibration Diagnostics of Turbine Engine Accessories
Authors: Watson Matthew J. , Sheldon Jeremy S. , Lee Hyungdae , Byington Carl S. , Behbahani Alireza
Published: January 2011

Traditional engine health management development has focused on major gas turbine engine components (i.e., disks, blades, bearings, etc.) due to the fact that these components are expensive to maintain and their failures frequently have safety implications. However, the majority of events that lead to standing down of aircraft arise from gas turbine accessory components such as pumps, generators, auxiliary power units, and motors. Common vibration diagnostics, which are based on frequency domain analysis that assumes the monitored signal is “stationary” during the analysis period, are not effective for these components. This is true because operating conditions are often non-stationary and evolving, which leads to spectral smearing and erroneous analysis that can cause missed detections and false alarms. Traditionally, this is avoided by defining steady state operating conditions in which to perform the analysis. Although this may be acceptable for major engine components, which are typically highly loaded during normal steady operation, many engine accessories are only high loaded during transients, especially startup. For example, an engine starter or fuel pump may be more highly loaded and therefore susceptible to damage during engine start up, typically avoided by traditional vibration analysis methods. More importantly, certain component faults and their progression can also lead to non-stationary vibration signals that, because of the smearing they induced, would be missed by traditional techniques. As a result, the authors have developed a novel engine accessory health monitoring methodology that is applicable during non-stationary operation through application of joint time-frequency analysis (JTFA). These JTFA approaches have been proven in other disciplines, such as speech analysis, radar processing, telecommunications, and structural analysis, but not yet readily applied to engine accessory component diagnostics. This paper will highlight the results obtained from applying JTFA techniques, including Short-Time Fourier Transform, Choi-Williams Distribution, Continuous Wavelet Transform, and Time-Frequency Domain Averaging, to very high frequency (VHF) vibration data collected from healthy and damaged turbine engine accessory components. The resulting accuracy of the various approaches were then evaluated and compared with conventional signal processing techniques. As expected, the JTFA approaches significantly outperformed the conventional methods. On-board application of these techniques will increase prognostics and health management (PHM) coverage and effectiveness by allowing accessory health monitoring during the most life influencing regimes regardless of operating speed and reducing inspection and replacement costs resulting in minimizing the vehicle down time.
Aeromechanical Optimisation of a Winglet-Squealer Tip for an Axial Turbine
Authors: Schabowski Zbigniew , Hodson Howard , Giacche Davide , Power Bronwyn , Stokes Mark R.
Published: January 2011

The possibility of reducing the over tip leakage loss of unshrouded axial turbine rotors has been investigated in an experiment using a linear cascade of turbine blades and by using CFD. A numerical optimisation of a winglet-squealer geometry was performed. The optimisation involved the structural analysis alongside the CFD. Significant effects of the tip design on the tip gap flow pattern, loss generation and mechanical deformation under centrifugal loads were found. The results of the optimisation process were verified by low speed cascade testing. The measurements showed that the optimised winglet-squealer design had a lower loss than the flat tip at all of the tested tip gaps. At the same time, it offered a 37% reduction in the rate of change of the aerodynamic loss with the tip gap size. The optimised tip geometry was used to experimentally assess the effects of the opening of the tip cavity in the leading edge part of the blade and the inclination of the pressure side squealer from the radial direction. The opening of the cavity had a negligible effect on the aerodynamic performance of the cascade. The squealer lean resulted in a small reduction of the aerodynamic loss at all the tested tip gaps. It was shown that a careful consideration of the mechanical aspects of the winglet is required during the design process. Mechanically unconstrained designs could result in unacceptable deformation of the winglet due to centrifugal loads. An example winglet geometry is presented that produced a similar aerodynamic loss to that of the optimised tip but had a much worse mechanical performance. The mechanisms leading to the reduction of the tip leakage loss were identified. Using this knowledge, a simple method for designing the tip geometry of a shroudless turbine rotor is proposed. Numerical calculations indicated that the optimised low-speed winglet-squealer geometry maintained its aerodynamic superiority over the flat tip blade with the exit Mach number increased from 0.1 to 0.8.
Sensitivity Analysis With Respect to Flutter-Free Design of Compressor Blades
Authors: May Markus
Published: January 2011

In this paper, the rotor geometries of two consecutive design loops are compared numerically with respect to aeroelastic stability. Therefore, the TRACE code of the German Aerospace Center DLR is used to compute the flutter predictions: based on a three-dimensional steady solution, the time-linearized Navier-Stokes equations are solved in order to assess the aerodynamic damping so that the critical inter-blade phase angles can be determined. Apart from the global stability behaviour the computation of local excitation per surface area is presented, facilitating the identification of stabilizing and destabilizing effects due to blade motion and flow field disturbances. Aiming for flutter-free design of compressor blades, an exemplary sensitivity analysis on the first mode is performed. Within the scope of this study, reduced frequency and mass ratio are varied and the influence of these parameters on the stability behaviour is deduced. For a tuned system, the nondimensional flutter equations are derived introducing the flutter index as aeroelastic similarity parameter. Differing tendencies of the aerodynamic work entry and the corresponding logarithmic decrement concerning flutter susceptibility are discussed in detail.
Experimental and Numerical Investigations of Aerodynamic Behavior of a Three-Stage HP-Turbine at Different Operating Conditions
Authors: Abdelfattah S. A. , Schobeiri M. T.
Published: January 2011

This paper describes experimental and numerical investigations of a three-stage high pressure research turbine which incorporates fully 3-D bowed blades at various operating conditions. Experimental data were obtained using interstage aerodynamic measurements at three measurement stations, namely, downstream of the first rotor row, the second stator row and the second rotor row. Measurements were conducted through the use of five-hole probes traversed in both circumferential and radial directions to create a measurement window. Aerodynamics measurements were carried out within a rotational speed range of 1800 to 2800 RPM. Numerical simulation of the aforementioned turbine was performed through the use of a commercial computational fluid dynamics code. A detailed mesh of the three-stages was created and used to simulate the corresponding operating conditions and a comparison was made between experimentally and numerically determined aerodynamics and turbine performance.
Testing Rotating Horizontal Axis Wind Turbine Blade Designs in a Laboratory Wind Tunnel
Authors: Van Treuren Kenneth W. , Gregg Jason R.
Published: January 2011

The importance of renewable and alternative energy is rapidly gaining attention. A national goal of replacing 20% of the United States electricity generation with wind power by 2030 has been proposed but such an ambitious goal is dependent on many parameters. Improved aerodynamic performance of wind turbine blades is one parameter necessary to achieve this goal. Blade testing is traditionally done using 2D airfoils in a laboratory wind tunnel, developing the lift and drag coefficients, and then using this data to predict wind turbine blade performance. Dimensional analysis has been used successfully in design of rotating machinery such as pumps, developing a series of dimensionless pump parameters with which to scale a particular pump design to a larger or small size. These parameters lead to similarity or affinity laws which relate any two homologous states for two pumps that are geometrically and dynamically similar. Affinity laws could be applied to wind turbines however the conditions tested in the wind tunnel do not match what would be expected in a full scale wind machine. As with pumps, the laws would apply only if the model and full scale wind turbine would operate at identical Reynolds numbers and are exactly similar (i.e. relative surface roughness and tip conditions). Reynolds numbers in the model tests are smaller than those achieved by the actual wind turbines while the surface roughness of the model is generally larger. This leads to the need for empirical equations to predict performance. This paper examines current wind tunnel testing and the problems with scaling wind turbine blades. It also outlines a methodology to test 3-D model wind turbine blades in a wind tunnel. Blades are designed and manufactured according to existing criteria, mounted to a generator, and their performance is then tested in the wind tunnel. Challenges with wind tunnel testing as well as extrapolation of the wind tunnel data to actual applications will be addressed.
Assessment of the Energy Conversion of Whole Oil Fruits With a Pyrolysis and Gas Turbine Process
Authors: Fantozzi Francesco , D’Alessandro Bruno , Bartocci Pietro , Desideri Umberto , Bidini Gianni
Published: January 2011

Crude vegetable oil energy conversion is addressed as an important issue for the electric energy production without changing the CO2 concentration in atmosphere. The oil is obtained by grinding oily fruits while a high amount of energy rich residues is produced. The present paper evaluates the thermodynamic and environmental performances of a plant that converts the whole fruit into energy through pyrolysis. Vegetable Oil is used to fuel an internal combustion engine while solid residuals of the oil production are used to fuel an Integrated Pyrolysis Regenerated Plant (IPRP) technology based plant. Tars from pyrolysis process are water scrubbed from syngas and then emulsioned with vegetable oil to increase the electric energy production. IPRP concept is based on a gas turbine (GT) fuelled with the syngas produced in a rotary kiln pyrolyzer fed with Biomass or Wastes (B&W); GT exhaust gases together with combustion of pyrolysis by-products (char), is used to sustain the pyrolysis process. The IPRP concept was modelled through thermodynamic relations, energy balances and data available in the Literature for oil yields and husks pyrolysis products. The analysis was carried out investigating the influence on plant performances of main thermodynamic parameters of the GT and on pyrolysis temperature. Results are collected for typical parameters of different GT sizes, namely the manometric compression ratio and the turbine inlet temperature. The paper discusses best efficiency points of different plant sizes when fuelled with syngas and tar and oil for three important oil fruits namely sunflower, palm and soybean.
Lateral Rotordynamic Analysis of a Large Alternator/Flywheel/Motor Train
Authors: Chaudhry Jawad , Dimond Tim , Younan Amir , Allaire Paul
Published: January 2011

A large alternator/flywheel/motor train is employed as part of the power system for the ALCATOR C-MOD experiment at the MIT Plasma Fusion Center. The alternator is used to provide peak pulse power of 100 MW to the magnets employed in the fusion experiment. The flywheel diameter is 3.3m and the alternator is 1.8 m in diameter. After being driven up to full speed over a long period of time by a 1491 kW motor, the alternator is rapidly decelerated from approximately 1800 rpm to 1500 rpm during a 2 second interval. This sequence is repeated about six times per working day on average. A full lateral rotordynamic analysis of the including the rotors, fluid film bearings and unbalanced motor magnetic force was carried to assess the effects of rotor modifications in the alternator shaft bore. This paper provides a more detailed analysis of a complicated rotor train than is often performed for most rotors. Critical speeds, stability and unbalance response were evaluated to determine if lateral critical speeds might exist in the operating speed range in the existing or modified rotor train and if unbalance levels were within acceptable ranges. Critical speeds and rotor damping values determined for the rotor system with the existing and modified rotor. The first critical speed at 1069 rpm is an alternator mode below the operating speed range. The second critical speed is also an alternator mode but, at 1528 rpm, is in the rundown operating speed range. The third critical speed is a flywheel mode at 1538 rpm, also in the rundown operating speed range but well damped. The predicted highest rotor amplitude unbalance response level is at 1633 rpm, again in the operating speed range. Direct comparisons were made with measured bearing temperature values, with good agreement between calculations and measurements. Stress levels in the rotor were evaluated and found to be well below yield stress levels for the material for both original and modified rotors. Comparisons we carried out between standard vibration specifications and measured vibration levels which indicated that the third critical speed amplification factors were much higher than API standards indicate they should have been. Corrective actions to reduce unbalance were taken for the modified rotor.
Combustion Dynamics in a Gas Turbine Single Annular Combustor Sector
Authors: Ichihashi Fumitaka , Cai Jun , Kao Y. H. , Syed A. A. , Jeng S. M.
Published: January 2011

The occurrence of combustion instability dynamics known, as “screech, howl and growl,” in the combustors of gas turbine engines is a very difficult challenge for engineers. The very high amplitude pressure oscillations caused by combustion dynamics, are not only detrimental to the operation of the engine and combustor, but the difficulty in predicting and remedying these problems can lead to significant costs and delays in engine development. The coupling of the unsteady heat release in the flame with the natural acoustic resonance modes of the combustor duct causes the phenomena of combustion dynamics. To improve our understanding of stability characteristics in such complex systems, encountered in many industrial applications, the flame structure of an atmospheric swirl-stabilized burner, containing dilution and cooling air holes and fed with natural gas fuel, was systematically investigated for various inlet temperatures, pressure drops and air-fuel ratios. Experiments were also designed and conducted with the goal to understand better the phenomena of combustion dynamics that were experienced. More specifically, six acoustic pressure transducers were incorporated in the combustor and in the upstream duct to measure the acoustic field and the acoustic impedance characteristics at specified locations of interest. A one-dimensional wave propagation model is presented to predict the acoustic frequencies and damping of resonance modes, based on the geometry of the test rig, the flow conditions, and the acoustic impedance characteristics of the terminations of the combustor. This paper will present the acoustic analysis of the test data in the light of the above-mentioned theoretical modeling. The limitations of the current test rig are pointed out and changes in the rig design are discussed for future research.
A Correlation Approach to Predicting Film Cooled Turbine Vane Heat Transfer
Authors: Boyle Robert J. , Ameri Ali A.
Published: January 2011

A correlation is developed to predict film cooling effectiveness for turbine vanes. Heat transfer data from a number of different sources is examined to determine if the correlation satisfactorily predicts film cooled vane heat transfer data. Predictions are made for a range of variables encountered in these data. The primary purpose of this work is to demonstrate how well film cooling correlations, developed from large scale experiments, can be utilized to predict turbine blade heat transfer. The correlation that is developed accounts for blowing ratio, Reynolds number, turbulence intensity, and surface curvature. A second purpose of this work is to illustrate the importance of comparing predictions with data at a sufficiently high Reynolds number to be applicable to first stage turbine vanes of future engines with their increased overall pressure ratios.
Numerical Study of Discrete Tip Injection in a Transonic Axial Compressor
Authors: Khaleghi Hossein , Teixeira Joao A.
Published: January 2011

This paper reports on a time-accurate simulation of discrete tip injection upstream of a transonic axial compressor, NASA Rotor-67. Twenty two discrete injectors were placed around the casing upstream of the blade to investigate the effect of injector-rotor interaction at near-stall condition. Time-accurate simulations were performed with and without tip injection at stable and unstable operating points. Although the injected mass flow rate is very small, the range extension obtained promises the effective use of such injection in suppressing rotating stall at early stages of formation, with almost no efficiency penalty incurred. The effect of injection on the tip flow structure and unsteady response of the leakage flow are presented and discussed. Results indicate that injection periodically pushes the tip leakage vortex and passage shock rearward. The location of the leakage vortex with injection was found to be backward of that without injection, at the near-stall condition of the non-injection case. At the near-stall point of the injection case, however, the tip leakage vortex was at some situations rearward and at some situations forward, as compared with the non-injection case. In other words, the leakage vortex in the injection case oscillates around the location of the time-averaged leakage vortex without injection. This is the situation, at which, the interface between the leakage and oncoming flows tends to become parallel to the leading-edge plane. The effect of injection on the boundary layer separation from the casing wall is also investigated. The rotor operation at in-stall condition for both the injection and non-injection cases is studied and the path into instability is discussed for each case. The propagation of a low-velocity region near the pressure surface and leading-edge of the blade was found to be responsible for the detachment of the passage shock from the leading-edge and upstream movement of the leakage vortex, leading to the occurrence of the leading-edge vortex spillage, for both the injection and non-injection cases.
A Probabilistic Framework for Gas Turbine Engine Materials With Multiple Types of Anomalies
Authors: Enright Michael P. , McClung R. Craig
Published: January 2011

Some rotor-grade gas turbine engine materials may contain multiple types of anomalies such as voids and inclusions that can be introduced during the manufacturing process. The number and size of anomalies can be very different for the various anomaly types, each of which may lead to premature fracture. The probability of failure of a component with multiple anomaly types can be predicted using established system reliability methods provided that the failure probabilities associated with individual anomaly types are known. Unfortunately, these failure probabilities are often difficult to obtain in practice. In this paper, an approach is presented that provides treatment for engine materials with multiple anomalies of multiple types. It is based on previous work that has extended to address the overlap among anomaly type failure modes using the method of Kaplan-Meier, and is illustrated for risk prediction of a nickel-based superalloy. The results can be used to predict the risk of general materials with multiple types of anomalies.