bluuebunny/crossref_metadata_2025 huggingface dataset:
Premixed Turbulent Combustion Models for Large Eddy and RANS Simulations
Authors: Tangermann Eike , Keppeler Roman , Pfitzner Michael
Published: January 2011

Large-Eddy simulation (LES) has become an important tool in computational fluid mechanics but still is far from replacing Reynolds-averaged Navier-Stokes (RANS) approaches. The present work compares combustion models for LES and RANS derived from the same physical assumptions. Thus a direct comparison of results from both approaches for a combusting flow becomes possible. The models are based on the assumption of a fractal shape of the flame surface, leading to the Lindstedt-Vaos model in RANS. Its generalization to LES is presented here. Both RANS and LES models are validated with data from a turbulent Bunsen flame to evaluate their sensitivity to turbulence level and length scale. The predicted turbulent burning velocity shows a very similar behavior in both models. The models are also tested with a second validation configuration, the combusting flow over a backward-facing step. This flow clearly shows the different behavior of RANS and LES methods in unsteady flows containing large coherent turbulent structures.
Propulsion Simulator/Stimulator Development for US Navy’s Newest Gas Turbine-Powered Ship: LHD 8 USS Makin Island
Authors: Turso James , Boughner Abe , Buonamici Gianfranco
Published: January 2011

The LHD 8 amphibious assault ship utilizes a hybrid propulsion plant, where the ship has the capability to be propelled by electric propulsion motors or gas turbine engines, all of which is controlled and monitored by a state-of-the-art Machinery Control System (MCS). Unlike the previous ships of the class which were steam powered, the hybrid drive is designed to allow economical low speed fuel efficiency on electric motors as well as a traditional gas turbine power plant for all other mission areas. This is expected to yield significant fuel savings over the life of the ship. The integrated machinery control system is likewise expected to reduce life cycle costs through reduced manning. The build specification for this ship class required that all MCS signals including the gas turbine alarms and shutdown functions be fully tested prior to initial light-off. Many of these functions are not activated, and therefore cannot be tested, until the Electronic Control Unit (ECU) senses that the gas turbine is running. Historically, previous ship classes used a manually-operated set of potentiometers to provide signals to a gas turbine ECU to simulate external inputs to allow testing of shutdown and alarm functions. For this newest class of engine however, the ECU is significantly more complex and requires the ECU to successfully progress through the start sequence, including sensed variables changing at expected rates, in order to activate the alarm and shutdown logic. In order to test this functionality, an engine simulator, physically interfaced to the ECU aboard the ship, was necessary. No system of this type is available or had ever been developed. Neither the engine or ECU manufacturer had a device for this purpose. The paper will discuss the development and implementation of a gas turbine simulator that incorporates an engine mathematical model fully compatible with the ECU controller, simulation hardware capable of supporting real-time system performance, signal conditioning necessary to provide/accept raw signals to/from the ECU, as well as a host laptop with software necessary to control simulator/stimulator and perform test functions. The paper will discuss the system requirements development, component selection, software and hardware development, and system integration and testing. Also discussed will be the results of bench testing as well as the final shipboard test results. Examples in the form of diagrams, photos, charts and schematics will be used. The paper will conclude with a discussion of the benefits of a dynamic gas turbine simulator and potential future applications.
Aerothermal Impact of the Interaction Between Hub Leakage and Mainstream Flows in Highly-Loaded HP Turbine Blades
Authors: Popovic´ I. , Hodson H. P.
Published: January 2011

This paper describes experimental and numerical investigations of a highly-loaded rotor blade with leakage (purge) flow injection through an upstream overlapping seal. The effects of both leakage mass flow rates and swirl have been studied to examine their effects on the aerothermal performance. As the leakage mass flow rate was increased, the loss generally increased. The increase in the losses was found to be non-linear with the three distinct regimes of leakage-mainstream interaction being identified. The varying sensitivity of the losses to the leakage fraction was linked to the effects of the upstream potential field of the blade on a vortical structure originating from the outer part of the seal. This vortical structure affected the interaction between the leakage and mainstream flows as it grew to become the hub passage vortex. Very limited cooling was provided by the leakage flows. The coolant was mainly concentrated close to the suction surface in the front part of the rotor platform and on the blade suction surface in the path of the passage vortex. However, the regions benefiting from cooling were also characterized by higher values of the heat transfer coefficient. As a consequence, the net heat flux reduction was small and the leakage injection was thus deemed thermally neutral.
Three-Dimensional Design Method for Long Blades of Steam Turbines Using Fourth-Degree NURBS Surface
Authors: Senoo Shigeki , Ogata Koji , Nakamura Tateki , Shibashita Naoaki
Published: January 2011

A new blade design method for steam turbines using the fourth-degree NURBS surface was developed. The method enables engineers to easily generate three-dimensional complex blade shapes that have inherently good aerodynamic performance and constraint satisfaction. The developed design method has three steps. First, 2D aerofoils are independently generated at each design height. The convergent or convergent-divergent aerofoils are selected on the basis of the outlet Mach number. The convergent flow path is defined by a fourth-degree NURBS curve to preserve the continuity of the slope of the curvature. The divergent flow path for supersonic flow is generated by the method of characteristic curves to avoid strong shock waves. The inlet and outlet angles are constrained to coincide with the flow angle of the velocity triangle. The design parameters, such as chord length, stagger angle and control points of NURBS are automatically decided using an evolutionary optimization technique NSGA-II to minimize the loss by computational fluid dynamics. Therefore, fewer man-hours are needed for design work and better proficiency is not a significant requirement. Second, the number of control points and knot vectors are equalized for all aerofoils by inserting or removing knots and fitting the divergent part by the fourth-degree NURBS curve. Finally, all aerofoils are stacked radially, for example, along the centroid axis, and the fourth-degree NURBS surface is generated by interpolating the control points of the NURBS curves of all the aerofoils. This design method can easily generate long blades of the last stage for steam turbines. The blade has a surface with continuity of the slope of curvature in all directions and good aerodynamic performance under constraints.
A Nonlinear Model of Rotor-Bearing-Seal System Associated With Leakage Through the Labyrinth Seal
Authors: Wang Wei Zhe , Liu Ying Zheng , Meng Guang
Published: January 2011

A nonlinear mathematical model for the rotordynamics of the rotor under the influence of the leakage air flow through a labyrinth seal was established in the present study. An interlocking seal was chosen for study. The rotor-bearing-seal system with four degrees of freedom was modeled as Jeffcot rotor subject to the aerodynamic force induced by the leakage flow through the interlocking seal and the oil-film force induced by the oil flow in the journal bearing. Particular attention was placed on the spatio-temporal variation of the aerodynamic force on the rotor surface in the coverage of the seal clearance and the cavity volume, which was specifically delineated by using Muzynska model and the perturbation analysis, respectively. The governing equation of the rotordynamics, into which the aerodynamic force integrated over all seal clearances and cavity volumes was incorporated together with the oil-film force, was solved by using the fourth-order Runge-Kutta method to obtain the orbit of the whirling rotor. Stability of the rotating rotor was inspected by using the orbital motions and the phase trajectories. The influence of the leakage air flow through the interlocking seal on the whirling rotor was described in terms of the rotating speed and the seal clearance. The results convincingly demonstrate that the destabilization of the rotor-bearing-seal system was reduced due to the aerodynamic force induced by the leakage air flow through the interlocking seal.
Steam Turbine Design Considerations for Ultrasupercritical Cycles
Authors: Zachary Justin
Published: January 2011

The current coal-fired power generation market requires higher cycle efficiencies not only for economic reasons, but also as a means of reducing plant carbon footprint. To achieve these goals, the plant must operate at higher pressures and temperatures in the supercritical (SC) and ultrasupercritical (USC) domains. This paper describes Bechtel’s experience and challenges in regard to the conceptual design and integration of large steam turbines operating under these severe conditions. Several examples of projects are described wherein Bechtel applied this neutral but proactive technical approach in the development or design phase to achieve the best and most cost-effective solution for its customers. The topics presented also relate to steam cycle optimization in terms of plant output, steam conditions, number of reheat circuits, and type and number of heaters. The impact on balance of plant systems, including water treatment, availability, and redundancy criteria, is also addressed.
Qualification of an Afterburner Thrust Augmentation System for an Aero Gas Turbine Engine
Authors: Mishra R. K.
Published: January 2011

Qualification of afterburner thrust augmentation system in stand-alone mode prior to its flight trials plays a vital role in aero engine application. A full-scale afterburner system was studied to demonstrate its performance parameters such as pressure loss, combustion efficiency, liner temperature at full and part load conditions. Light-off characteristics at different altitude-flight Mach combination were also established. The afterburner system also was activated for considerable time to validate its integrity and performance. The paper presents the various tests carried out on the afterburner and their results. The paper also highlights the jet nozzle matching at various throttle position and studies on combustion instability from qualification point of view. Satisfactory demonstration of performance of the afterburner without encountering screech or buzz over the operating range qualifies the system for its application in the aero engine for limited operation.
Study of Fault Self-Recovery and Seal Improvement for Centrifugal Compressor
Authors: Wang Weimin , Gao Jinji , Li Yan , Li Shuangxi
Published: January 2011

For centrifugal compressor, discharge or suction pressure variations due to process fluctuations or balance drum seal degradation can result in rotor thrust increasing which may jeopardize thrust bearing and compressor’s reliability. Also, the leakage flow through balance drum seal can seriously affect the efficiency of compressor. Summarizing the characteristic of axial displacement fault about centrifugal compressor and analyzing the mechanical performance of tilt pads thrust bearing, theory of axial displacement fault self-recovery is presented and realized through experimental study. The method presented in this paper monitors the stiffness of oil film and identifies the reason of axial displacement increasing. Also the low leakage feature of Dry-Gas-Seal (DGS), high reliability of labyrinth, and the feasibility of upgrading existing structure are taken into account at the same time to design a combined labyrinth-dry gas seal system on the balancing drum. Based on the combined seal system, a Fault Self-Recovering (FSR) mechanism for the fault of rotor axial displacement is introduced to assure the minimum oil film thickness was ensured in real time. The modern Computational Fluid Dynamics (CFD) and experimental study were used to validate this concept. The result and relevant information indicate that the method can realize axial displacement fault self-recovering effectively and the combined sealing system could improve the efficiency of the centrifugal compressor about four percent.
On the Performance of Porous Sound Absorbent Material in High Temperature Applications
Authors: Giese Frank , Ries Hans-Christoph , Eigenbrod Christian
Published: January 2011

This paper discusses the use of novel porous sound absorbent ceramic tiles as heat shields in combustion chambers with respect to their sound absorption. For this purpose a theory describing the bulk properties of a homogeneous porous absorber layer was combined with a transfer matrix approach to account for the temperature gradient within the absorber. By means of a high temperature scenario, the maximum absorption performance and the required microscale properties of the absorber are presented.
Impact of Operating and Health Conditions on Aero Gas Turbine: Hot Section Creep Life Using a Creep Factor Approach
Authors: Abdul Ghafir M. F. , Li Y. G. , Singh R. , Huang K. , Feng X.
Published: January 2011

A thorough assessment of component life is very important to ensure both the safety and economics of gas turbine operation. As a component’s life given by OEM is based on certain ambient and operating conditions, its actual life may vary substantially when the ambient, operating and engine health conditions change. Therefore possessing knowledge on how those conditions affect actual component life will be valuable in making informed maintenance decisions, maximising operation effectiveness and cutting down operating costs. In this paper, an impact analysis on component creep life due to different operating and engine health conditions using an introduced Creep Factor is performed, which aims to provide useful insights on the relationship between gas turbine performance change and hot section component’s creep life. As the Creep Factor is defined as the ratio between the actual creep life and a reference creep life at a user-defined condition, the magnitude of the impact can be quantified with the change of the Creep Factor. The developed creep life analysis approach was applied to a model single spool turboshaft gas turbine engine operated at various operating and health conditions. A physics-based model combined with the Creep Factor approach was then used to estimate the creep life variation of the high pressure turbine of the model engine. The results showed that for a clean engine, the change in the rotational speed has given the highest impact on the creep life consumption. Also the presence of blade cooling and component degradation is seen to significantly reduce the blade’s creep life and as the degradation effects are combined, the degree of reduction increases even more. It also shows that the Creep Factor is good indicator of creep life consumption and provides a good technique to rank the influencing factor according to the threat they imposed.
Impact of Operating Conditions and Design Parameters on Gas Turbine Hot Section Creep Life
Authors: Eshati S. , Abdul Ghafir M. F. , Laskaridis P. , Li Y. G.
Published: January 2011

This paper investigates the relationship between design parameters and creep life consumption of stationary gas turbines using a physics based life model. A representative thermodynamic performance model is used to simulate engine performance. The output from the performance model is used as an input to the physics based model. The model consists of blade sizing model which sizes the HPT blade using the constant nozzle method, mechanical stress model which performs the stress analysis, thermal model which performs thermal analysis by considering the radial distribution of gas temperature, and creep model which using the Larson-miller parameter to calculate the lowest blade creep life. The effect of different parameters including radial temperature distortion factor (RTDF), material properties, cooling effectiveness and turbine entry temperatures (TET) is investigated. The results show that different design parameter combined with a change in operating conditions can significantly affect the creep life of the HPT blade and the location along the span of the blade where the failure could occur. Using lower RTDF the lowest creep life is located at the lower section of the span, whereas at higher RTDF the lowest creep life is located at the upper side of the span. It also shows that at different cooling effectiveness and TET for both materials the lowest blade creep life is located between the mid and the tip of the span. The physics based model was found to be simple and useful tool to investigate the impact of the above parameters on creep life.
On the Efficiency of Secondary Flow Suction in a Compressor Cascade
Authors: Liesner Karsten , Meyer Robert , Lemke Matthias , Gmelin Christoph , Thiele Frank
Published: January 2011

An experimemtal investigation in a high speed compressor cascade has been carried out to show the effect of different types of secondary flow suction. In order to get deeper insight into the separated three dimensional flow topology and to determine appropriate suction positions, numerical simulations are performed additionally for the baseline cascade. To obtain the flow solution, an implicit, pressure based solver, elaN3D (by ISTA TU Berlin), is employed in steady RANS mode, whereby the Menter SST-k model is used for turbulence treatment. Both investigations are conducted at Mach number Ma = 0.67 and Reynolds number Re = 560.000. The aerodynamic design condition is used. The examined cascade consists of NACA65-K48 type vanes. The experiments include measurements with four different types of suction geometries plus reference measurements. Total pressure and flow angle measurements in the wake show the flow deflection, total pressure loss and the rise of the static pressure of the cascade. The best suction geometry follows the design of R.E. Peacock, designed for low Mach number cascades, with small changes. Using a maximum suction rate of 2% of the main flow the total loss coefficient was reduced by 23%. In this case the stage efficiency — calculated with a reference rotor — is increased by almost 1%. The vacuum pump energy consumption has been taken into account for this calculation. In another case the suction geometry has been chosen in a way that the suction slot is placed along the sidewall from suction side to pressure side following the wall streamlines. With an increased suction rate of 5% of the main flow, the vortex system in the passage is eliminated and the total loss coefficient is decreased to 0.055, which equals to a decrease of 37%. Taking into account that compressors in aero-engines provide bleed air for the plane’s air system, enormous efficiency increase is possible. For this the air bleed valves need to be redesigned.
Fracture Mechanics Analysis of a Single Crystal Turbine Blade
Authors: Wu X. , Beres W. , Zhang Z. , Reed P. A. S.
Published: January 2011

Single crystal superalloy turbine blades exhibit anisotropic behaviors, and the stress at the fir-tree root often reaches the yield stress of the material when the turbine operates at the peak rotational speed and at the maximum temperature. The nonlinear behavior of the material character at these operating conditions poses a significant challenge to prediction of the blade behavior using the conventional linear elastic fracture mechanics approach. In this paper a fracture mechanics analysis was performed for a single crystal turbine blade using the J-integral concept. First of all, the elastic-perfectly plastic J-integral and CTOD was used to correlate with the fatigue crack growth rates obtained in a single crystal blade in [100] and [110] directions, with the [001] direction as the loading direction under typical service conditions. The weight function method was used to evaluate the stress intensity factor for a crack growing along the serration bottom of the blade fir-tree root under small-scale yielding conditions and the crack growth analysis was performed using the correlated fatigue crack growth data. In addition, crack growth simulations were also performed using the Zencrack software. The simulated crack growth profile was compared with the actual crack profile on the component.
Velocity Measurements Around Film Cooling Holes With Deposition
Authors: Haase Kristian , Bons Jeffrey P.
Published: January 2011

The choice of synthetic fuels (synfuels) in order to achieve greater fuel flexibility may lead to unwanted solid depositions on the blades of turbomachines. The objective of this paper is to gain information of the flow field over a turbine blade with depositions around the film cooling holes. For the investigation the particle image velocimetry technique (PIV) is utilized. The experiments are conducted in a low speed wind tunnel at a Reynolds number of 300,000 based on the distance from the leading edge to the middle of the cooling holes and a Reynolds number of 9,200 based on the hole diameter. Three different simulation plates are tested in the tunnel—a flat plate for comparison, a plate with large depositions only upstream of the holes, and one with smaller depositions all around the holes. The two deposition configurations are scaled models of actual depositions formed at simulated engine flow conditions on a turbine test coupon. The experiments are conducted at four different coolant to free stream blowing ratios—0, 0.5, 1, and 2—and at a density ratio of 1.1. PIV images are taken in four planes from the side of the tunnel to record the main flow structures and in five planes from the end of the tunnel to record the secondary flow structures. The results show that the type of deposition has a large influence on the flow field. With the smaller depositions the penetration of the coolant jet into the free stream is significantly reduced but the dimension and strength of the kidney vortices is increased compared to the flat plate. With the large depositions, on the other hand, the penetration of the coolant jet is much higher due to the ramp effect and the dimension of the secondary vortices is also increased. It can also be seen that the coolant gathers and stays behind the large depositions and then flows off very slowly. Film effectiveness and surface heat flux data acquired with the same plates (and reported previously) allow the identification of flow features and their direct influence on the film cooling performance.
Numerical Study of Internally Finned Bayonet Tubes in a High Temperature Bayonet Tube Heat Exchanger With Inner and Outer Fins
Authors: Ma T. , Lin M. , Zeng M. , Ji Y. P. , Wang Q. W.
Published: January 2011

A bayonet tube heat exchanger with fins being employed outside and inside outer tubes of bayonet-elements is recommended to be used in the ultra high temperature environment by our previous research, such as Externally Fired Combined Cycle and syngas production processes. The present study is concerned with the heat transfer and pressure drop characteristics in internally finned bayonet tubes. Two kinds of thermal boundary conditions applied to the model, i.e., constant wall temperature boundary and convective heat transfer boundary, are calculated and compared. Effects of different fluid flow patterns, inlet Reynolds number and tube length on the heat transfer and pressure drop characteristics are performed. Thermal stress is produced due to the large temperature difference between the inner and outer tube under ultra high temperature environment. Considering the safety of the heat exchanger, the alternative designs are suggested that there should be a small spacing between the inner fin and inner tube surface. The effects of various spacing on the heat transfer and pressure drop characteristics are discussed as well. Based on the results, the suitable spacing is proposed.
Gas Turbine Dynamic Model and Control in Integrated Gasification Combined Cycle Application
Authors: Parulekar Prashant S. , Gurgenci Hal
Published: January 2011

This study used a dynamic model to analyze the influence of syngas firing on the dynamic performance of the gas turbine and assessed the influence of bleeding air from the gas turbine axial flow compressor on the overall performance of the gas turbine. The dynamic model simulated the inlet air flow control using inlet guide vanes, stage by stage model of a 17-stage axial compressor, a thermodynamic model of the combustors, a lumped turbine blade cooling model, a 4-stage turbine model and a torsional shaft model. This open loop dynamic model was then controlled using control blocks that modulated the inlet guide vanes and fuel supply to facilitate stable operation using natural gas and syngas. The model investigated the impact of switching from natural gas firing to syngas firing. Influence of variation in the diluent nitrogen quantity supplied to the combustor was also analyzed.
Attenuation of Vane Distortion in a Transonic Turbine Using Optimization Strategies: Part I—Methodology
Authors: Joly M. , Verstraete T. , Paniagua G.
Published: January 2011

Single-stage high-pressure turbines often operate in the transonic regime, resulting in strong shock interactions between the vanes and the rotor blades. With the present study, a Multi-Objective Optimization is applied to the redesign of a transonic vane. The objective of the steady-flow optimization is to attenuate the propagation of shock waves downstream of the vane, while reducing the vane losses. Computation of the resulting unsteady forcing on the rotor is performed to validate the reduction in high-cycle fatigue risk. This first part presents the optimization code developed at the von Karman Institute. An evolutionary optimization strategy is applied with a differential evolution algorithm to address multi-objective problems. Turbine vane design is performed using a parametrization of 2D sections and of the 3D stacking line. Aerodynamic performances are evaluated with the TRAF solver considering robust mesh generations. Metamodels are investigated to provide a fast approximation of the Navier-Stokes computation. A methodology is proposed to assess the accuracy and robustness of the metamodel prediction, i.e. to evaluate the metamodel training effectiveness. The second part of this paper targets at the application of the optimization technique to the transonic turbine vane design. The objective is to reduce the downstream pitchwise static pressure distortion, with no increase of vane losses. The operating conditions are an isentropic exit Mach number of 1.2 and an outlet angle of −74 degree. The methodology includes a 2D section steady-flow optimization design at mid-span. Optimal airfoil passages present a convergent-divergent contraction channel that reduces the trailing edge shock system propagation. Validation of the geometry with the computation of the unsteady force response on the rotor confirms a reduction in high cycle fatigue risk. A multi-point optimization highlights the conflict between reducing the stator/rotor interaction and limiting the losses at off-design. A 3D optimization is finally performed considering simultaneously the lean and 2D section adaptation and enables further improvements of stator/rotor interaction and losses.
Attenuation of Vane Distortion in a Transonic Turbine Using Optimization Strategies: Part II—Optimization
Authors: Joly M. , Paniagua G. , Verstraete T.
Published: January 2011

Single-stage high-pressure turbines often operate in the transonic regime, resulting in strong shock interactions between the vanes and the rotor blades. With the present study, a Multi-Objective Optimization is applied to the redesign of a transonic vane. The objective of the steady-flow optimization is to attenuate the propagation of shock waves downstream of the vane, while reducing the vane losses. Computation of the resulting unsteady forcing on the rotor is performed to validate the reduction in high-cycle fatigue risk. The first part of this paper presents the optimization code developed at the von Karman Institute. An evolutionary optimization strategy is applied with a differential evolution algorithm to address multi-objective problems. Turbine vane design is performed using a parametrization of 2D sections and of the 3D stacking line. Aerodynamic performances are evaluated with the TRAF solver considering robust mesh generations. Metamodels are investigated to provide a fast approximation of the Navier-Stokes computation. A methodology is proposed to assess the accuracy and robustness of the metamodel prediction, i.e. to evaluate the metamodel training effectiveness. This second part of this paper targets at the application of the optimization technique to the transonic turbine vane design. The objective is to reduce the downstream pitchwise static pressure distortion, with no increase of vane losses. The operating condition are an isentropic exit Mach number of 1.2 and an outlet angle of −74 degree. The methodology includes 2D section steady-flow optimization design at mid-span. Optimal airfoil passages present a convergent-divergent contraction channel that reduces the trailing edge shock system propagation. Validation of the geometry with the computation of the unsteady force response on the rotor confirms a reduction in high cycle fatigue risk. A multipoint optimization highlights the conflict between reducing the stator/rotor interaction and limiting the losses at off-design. A 3D optimization is finally performed considering simultaneously the lean and 2D section adaptation and enables further improvements of stator/rotor interaction and losses.
Response Prediction of Frictionally Constraint Blade Systems Based on a Variable Normal Load Microslip Model
Authors: Liu Yalin , Xu Zili , Bo Shangguan , Li Linzhong
Published: January 2011

A discrete microslip friction contact model, which can consider time-dependent/space-related normal load, has been established to investigate the contact kinematics in the contact interfaces between adjacent blade shrouds. The model extends the capability of Csaba’s model in dealing with the situation of variant normal load. A Fast Anti-alias Fourier transform (FAFT) is introduced to the alternating frequency/time domain method (AFT) to improve the accuracy of spectrum analysis and extend analysis spectrum range. The developed friction model and the modified AFT are applied to calculate nonlinear vibration for a simplified shrouded blade, and the effect of parameters on resonant frequency and amplitude of shrouded blade are investigated and discussed. Comparing with existing variable normal load macroslip model, the model proposed here has the mathematically tractable characteristic and can be easily used. Combining with the AFT method, it is suitable for the analysis of complex system with multiple variables and degrees of freedom, and it can meet the engineering need.
Experimental Investigation on Damping Characteristics of Blade With Loosely Assembled Dovetail Attachment
Authors: Bo Shangguan , Xu Zili , Liu Yalin , Xu An
Published: January 2011

The damping characteristics of blade with loosely assembled dovetail attachment are investigated experimentally. An experimental method and a test rig were presented to study the blade damping characteristics. In the measurement system, an external force is imposed on blade, to simulate the centrifugal force of blade. The dynamic responses of a group of simulation blades with different dovetail attachment angles were measured in consideration of variable simulation centrifugal force. The damping characteristics of a compressor blade with dovetail attachment were measured too. Some conclusions can be drawn from the experimental results. The resonant frequency increases with the centrifugal force, gradually reaches a certain value. The amplitude of resonant response decreases at the beginning and then increases with the centrifugal force increasing, there exists a special centrifugal force on which the effect of dry friction damping is the best. The change rate of the blade response in the range of neighboring optimal centrifugal force is obviously influenced by the dovetail angle. From the results of the last stage blade of compressor, we can find that the resonant amplitude retains a low level when the centrifugal force is from 1.5kN to 4kN.
Measurement Selections for Multi-Component Gas Path Diagnostics Using Analytical Approach and Measurement Subset Concept
Authors: Jasmani Mohd Shahrizal , Li Yi-Guang , Ariffin Zaharudin
Published: January 2011

Gas path analysis (GPA) is a powerful tool to predict gas turbine degradations based on measurement parameters of gas turbine engines. Accordingly, prudent measurement selections are crucial to ensure accurate GPA predictions. This paper is intended to investigate the influence of measurement parameter selection towards the effectiveness of GPA algorithm. An analytical methodology for measurement selection, combined with measurement subset concept, is developed to properly select measurements for multiple component fault diagnosis. The effectiveness of GPA using the measurement sets selected with the introduced measurement selection method are then compared to the results of using standard measurements installed on existing gas turbine engines. A case study applying the new measurement selection method to GPA diagnostic analysis is demonstrated on a 3-shaft aero-derivative industrial gas turbine model based on similar unit installed onboard an offshore platform operated by PETRONAS. The engine is modeled and simulated using PYTHIA, a gas turbine performance and diagnostics analysis tool developed by Cranfield University. To validate the findings, non-linear GPA prediction errors are evaluated in various cases of single and multi components faults. As a result, the selected measurements have successfully produced much superior diagnostics accuracies in the fault cases when compared to the standard measurements. These findings proved that proper measurement selection for better GPA diagnostic analysis can be achieved by using the proposed analytical methods. Several engine sensor enhancements are also discussed to accommodate the unique sensor requirements for health diagnostics using GPA.
Study of Sand Particle Trajectories and Erosion Into the First Fan Stage of a Turbofan
Authors: Ghenaiet Adel
Published: January 2011

Ingestion of dust particles by aero-engines or stationary gas turbines is inevitable when operating in extremely polluted environments. The impingements of particles on the surfaces of blades cause erosion damage and permanent losses in engine performance. This paper presents a study of the particle dynamics and erosion in the first stage of a turbofan. The steady flow field through the turbomachinery components was solved separately from the solid phase. The particle trajectories computations used a stochastic Lagrangian tracking code that implements probabilistic modeling for particle size rebound and fragmentation, and considers the eddy-lifetime concept for turbulence and the complex flow features near walls. The equations of a particle motion were solved in a stepwise manner using the seventh order RK-Fehlberg technique, whereas particle tracking in different cells of the computational domain used the finite element method. Computations of particle trajectories were carried out for sand particles MIL-E5007E (0–1000 microns) at low, mid and high concentrations. As the locations of impacts were predicted, erosion contours were estimated and the subsequent blade deteriorations were assessed. The rotor blade shows a noticeable erosion of the blade leading and trailing edges almost from root to tip and a rounding of blade tip. Erosion patterns in the diffuser depict high erosion at blade leading and trailing edges and the erosion of pressure side is spreading almost from root to tip, in addition to erosion over the suction side. The actual findings may serve in improving erosion resistance of the blades in this fan stage.
Optimization of Turbofan Propulsion Cycle Using a Genetic Algorithm
Authors: Ghenaiet Adel
Published: January 2011

This paper presents an evolutionary approach as the optimization framework to design for the optimal performance of a high-bypass unmixed turbofan to match with the power requirements of a commercial aircraft. The parametric analysis had the objective to highlight the effects of the principal design parameters on the propulsive performance in terms of specific fuel consumption and specific thrust. The design optimization procedure based on the genetic algorithm PIKAIA coupled to the developed engine performance analyzer (on-design and off-design) aimed at finding the propulsion cycle parameters minimizing the specific fuel consumption, while meeting the required thrusts in cruise and takeoff and the restrictions of temperatures limits, engine size and weight as well as pollutants emissions. This methodology does not use engine components’ maps and operates on simplifying assumptions which are satisfying the conceptual or early design stages. The predefined requirements and design constraints have resulted in an engine with high mass flow rate, bypass ratio and overall pressure ratio and a moderate turbine inlet temperature. In general, the optimized engine is fairly comparable with available engines of equivalent power range.
Experimental Investigation of Conjugate Heat Transfer in a Rib-Roughened Trailing Edge Channel With Crossing-Jets
Authors: Coletti Filippo , Scialanga Manfredi , Arts Tony
Published: January 2011

The present contribution is devoted to the experimental study of the conjugate heat transfer in a turbine blade cooling cavity located near the trailing edge. The cooling scheme is characterized by a trapezoidal cross-section, one rib-roughened wall and slots along two opposite walls. The Reynolds number, defined at the inlet of the test section, is set at 67500 for all the experiments. The values of all the important non-dimensional parameters characterizing the experiment, including the solid-to-fluid conductivity ratio, are engine-representative. Uniform heat flux is imposed along the outer side of the rib-roughened wall. The measurements are performed using three different ribbed walls, with thermal conductivities ranging from 1 to 18 Wm−1K−1. Highly resolved distributions of non-dimensional temperature and Nusselt number over the rib-roughened wall are obtained by means of infrared thermography and finite element analysis. The impact of the conduction through the wall on the thermal performance is demonstrated by comparison with purely convective results, previously published by the authors on the same configuration.
Non-Linear Maneuver-Acceleration Analysis for Airborne Gas Turbine Engines
Authors: Brockett Theodore S.
Published: January 2011

A maneuver and acceleration analysis is a standard way to predict the structural displacements, clearance closures, and shaft and bearing loading due to aircraft turn rates and accelerations in airborne gas turbine engines. The industry standard practice is to perform these analyses assuming the acceleration and turn rates are steady-state. This gives rise to a static analysis in which the applied loads are a function of the aircraft turn rate, the aircraft translational accelerations, and the aircraft rotational accelerations. A method is presented for predicting static maneuver and acceleration lateral deflections and accompanying loads for airborne gas turbine engines with non-linear supports. The non-linear supports might include connections to ground and/or connections between various components of the rotor-structure system. These potential connections include squeeze-film-dampers (SFDs), clearance in rolling-element bearings, clearance stops in spring cages, rubs between rotors and shrouds, rubs between shafts, or supports modeled as non-linear (cubic) springs. The advantage of the method over traditional transient analysis is that the displaced shape (and accompanying shafting, bearing, and structure loads) can be found using an iterated static solution algorithm such that the transient solution is avoided. The algorithm allows for fast design trade studies when clearance closure and associated shafting/structure/bearing loads are part of the maneuver/acceleration analysis.
Comparisons of Flow Friction and Heat Transfer Performance in Rectangular Channels With Pin Fin-Dimple, Pin Fin and Dimple Arrays
Authors: Rao Yu , Wan Chaoyi , Zang Shusheng
Published: January 2011

An experimental study was conducted to investigate the flow friction and heat transfer performance in rectangular channels with pin fin-dimple and pin fin arrays in the Reynolds number range of 8200–54000. The friction factor, average Nusselt number and the overall thermal performance parameters of the pin fin-dimple and the pin fin channels have been obtained and compared with the experimental data of a smooth rectangular channel and previously published data of a pin fin channel and a dimpled channel. The comparisons show that the pin fin-dimple channel has a better convective heat transfer performance, a lowered friction factor and a higher overall thermal performance than the pin fin channel. The comparisons also show that the pin fin-dimple channel has a significantly higher heat transfer performance and friction factor than the dimpled channel, however the former’s overall thermal performance becomes distinctively lower than the latter at a higher Reynolds number than 37000.
Repair Process Technology Development and Experience for W501F Row 1 Hot Gas Path Blades
Authors: Miglietti Warren , Summerside Ian , Hoevel Simone , Zainuddin Zaki
Published: January 2011

Volatile market dynamics in the electrical power generation field continues to force power companies to identify prudent material cost reductions opportunities in their Operations and Maintenance (O&M) business. Today, there is an industry-recognized need for advanced hot gas path component repair and reconditioning capability for operators of F-Class gas turbines that can be highly cost effective with short cycle times. The SGT6-5000F (W501FD) engine, an “F” class machine has been in operation for more than a decade now. Of importance to operators/users and owners of this gas turbine engine is the ability to recondition the turbine “hot-end section” components, in order to support maintenance requirements. The first 2 rows of blades are unshrouded; whereas the last 2 rows are shrouded. The row 1 blades show severe degradation and thus repair of this component has been a focus point for PSM. The technical objective is to develop repair schemes for the row 1 blades since this component (other than the Transition Piece (TP)) has the highest frequency of replacement, plus is the highest replacement cost per component. Special processes have been developed for these components repairs, including but not limited to: a) Acid stripping of the coating; b) Machining off of the original brazed tip cap plates; c) High frequency gas tungsten arc welding and vacuum diffusion braze repair of platform cracks; d) High frequency gas tungsten arc weld attachment or laser welding of new tip cap plates; e) Laser metal forming/cladding of new squealer tips; f) Rejuvenation heat treatment; g) Application of superior MCrAlY and TBC coating to that originally applied. 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.
Experimental and Analytical Mistuning Analysis of a Blisk at Lab Conditions and Under Rig Conditions Using Tip Timing
Authors: Schoenenborn Harald , Retze Ulrich , Ziller Gerhard , Waniczek Phillip
Published: January 2011

Determination of the amplification factor due to mistuning is an important task for the safe design of turbomachinery, specially for blisk-design with low mechanical damping. The complexity of the environment effects increases from measurements in the laboratory to measurements in test rigs and engines. Also the uncertainties of the boundary conditions increase. In this paper measurements of the amplification factors due to mistuning at various conditions are presented, starting from simple lab measurements up to rig measurements. Calculations with a Reduced-Order Code based on measured frequency distributions and FEM are performed and compared with the measurements. For the determination of the amplification factor a mistuning rig with travelling wave excitation was built. For a small demo-blisk the amplification factor was determined. Then a real blisk was tested. Afterward, the same blisk was built into a two-stage axial compressor rig. Here, tip-timing measurements were performed under rig conditions (centrifugal force, flow conditions). As tip-timing measures the vibration amplitude of each single airfoil, an amplification factor can be determined for each resonance.
Design and Analysis of HP-Turbine for Variable Cycle Engine
Authors: Liu Zhi-gang , Fang Xiang-jun , Liu Si-yong , Wang Ping , Yin Zhao
Published: January 2011

A supersonic highly loaded high-pressure turbine with large enthalpy drop was designed for a variable cycle Engine (VCE) in the conditions of both single and double bypass modes in accordance with the similarity principle in the paper. The blade profiles were designed by means of a three-dimensional (3D) profile design method based on S1 stream surface. Then, 3D numerical simulations were performed on the HP turbine of both working conditions with different thermodynamic cycle parameters to confirm the design methods and results. The one-equation turbulence model of Spalart-Allmaras was applied to solve Reynolds’s averaged Navier-Stokes equations and the transition model of Abu-Ghanam Shaw (AGS) was introduced to capture the development process of boundary layer on blade surfaces in the simulations. The results of simulations indicate that the turbine performances are satisfactory in both working conditions with high efficiency and the design targets being anticipated have been achieved. The method of design profiles based on S1 stream surface is more precise and effective than conventional cylinder method for turbine blade because the 3D characteristics of flow field are considered elaborately. Further research reveals wave structures in the supersonic turbine, behavior of tip clearance flow, the phenomenon of transition flow in boundary layer and the physical mechanism of strong compressive wave-boundary layer interactions.