bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Erosion Characteristics of Solid Particles in the First Reheat Stage Blades of a Supercritical Steam Turbine
Authors: Cai Liu-xi , Wang Shun-sen , Di Juan , Mao Jing-ru , Feng Zhen-ping , Zhang Jun-jie , Xu Ya-tao
Published: September 2014

Reducing solid particle erosion (SPE) of blades is one of the most urgent problems for supercritical steam turbine power generation technology. Based on the erosion rate models and the particle rebound models of blade materials obtained through the accelerated erosion test under high temperature, erosion characteristics of the first reheat stage blades in a supercritical steam turbine was simulated and analyzed by three-dimension numerical simulation method in this paper. The influence of operating conditions, particle size distribution in the inlet of nozzle and axial clearance between vanes and rotating blades on the erosion distribution of cascade were explored quantitatively. Results show that: the erosion damage of the first-reheat stage stator is mainly caused by suction surface impingement from oxide particles. In designed loading condition, small and median size of particles mainly eroded the trailing edge (TE) of nozzle pressure surface, while large particles mainly impinge the leading edge (LE) of rotating blades and the TE of vane suction surface, and erosion increase along the blade height. When the turbine is running under part-load condition, particle impingement angle on stator pressure surface is basically unchanged, while impingement velocity slightly reduced. However, the amount of particles that impinge the stator TE suction side after their first-time impingement on rotor LE increase rapidly, leading to the more severe erosion damage of stator suction surface. The particle size distribution in the inlet of nozzle has a significant effect on the erosion simulation of first reheat stage blades, and the size distribution sampled in one unit may not be used to other units. When axial clearance changes, the erosion weight loss of vane pressure surface near TE is basically held constant, while the erosion weight loss in vane suction surface near TE decreases with the increase of axial clearance. For the supercritical 600MW unit simulated in this article, the anti-SPE performance and the unit efficiency can be balanced well when the axial clearance increases to 13mm. The results in this paper will provide a technology basis for reducing oxide particle erosion in the first reheat stage blades of supercritical steam turbine.
Numerical Analysis of Flow in a Transonic Compressor With a Single Circumferential Casing Groove: Application to Two Different Compressor Rotors
Authors: Sakuma Yasunori , Watanabe Toshinori , Himeno Takehiro , Kato Dai , Murooka Takeshi , Shuto Yukari
Published: September 2014

The effect of a single circumferential casing groove on the stability enhancement of two different transonic compressors has been examined with CFD analysis. The differences in flow field and stall inception mechanism between two rotors are presented with principal focus on passage blockage and tip leakage flow behavior. Detailed observation showed that the blockage flow which leads the compressor to stall was different between each other. A parametric study conducted with respect to the axial location of the groove has clarified that the effect which groove has on the tip leakage flow behavior changes according to the blade tip loading and the design tip clearance gap at the location where the groove is applied. When the casing treatment was applied to the compressors with different instability mechanism, whether the casing treatment could enhance the stability of compressor or not was not only dependant on the extent of the influence which it had on the flow field but also on whether it could affect the original stall-initiating phenomena at the adequate location.
Multimode Flutter Analysis of Transonic Fan Using FSI Simulation
Authors: Tateishi Atsushi , Watanabe Toshinori , Himeno Takehiro , Inoue Chihiro
Published: September 2014

Fully coupled steady fluid-solid interaction (FSI) and flutter simulations were conducted on a NASA Rotor 67 transonic experimental fan to demonstrate the capability of application for capturing various aeroelastic phenomena in turbomachinery. The effect of blade deformation on the aerodynamic performance was investigated by steady FSI. Aeroelastic modes were determined using the modal identification technique for the vibration of the cascade. The proposed identification method successfully estimated aeroelastic modes without significant uncertainty. Aeroelastic eigenvalues were localized around the structural modes in vacuum forming the “mode family”, and there was negligible change in their frequency. The calculated aerodynamic coupling between the structural modes was small. Based on the reconstructed local unsteady aerodynamic force, the major damping sources in the 1F mode family were determined to be the shock motion and supersonic region near the leading edge. From these results, it was confirmed that the developed FSI method was applicable to the analysis of unsteady characteristics of blades in multimode oscillation.
Missile Probability Analysis of Welding Nuclear Turbine Rotor
Authors: Chen Rong , Hua Wen Xiang , Yang Yan Lei , He Xiao Zhong
Published: September 2014

In this paper, a 1000MW nuclear turbine LP welded rotor was analyzed to assure the missile safety of the turbine, which is required by the Nuclear Regulatory Commission (NRC). Finite element analysis method was used to estimate the stress level of the rotor. Stress corrosion cracking (SCC) was considered as the main reason of the rotor failure. The probabilistic method was used to assess the missile safety of the turbine rotor. The high speed turbine rotor is one of the key components of the turbine-generator system which was related closely to the safety and economy of the Power Plant’s operation. In this paper the rotor design & analysis process for the Shanghai Turbine Plant’s nuclear 1000MW power station is described. The operation of the turbine rotors of the nuclear power plant suffered from the severe stresses because of high temperature and high speed during start-up, shutdown and load changes. The moisture steam environment due to the low nuclear steam temperature also increase the probability of the fatigue failure of the turbine rotor. The integrity of the turbine rotor was threatened by the material deterioration caused by fatigue and moisture corrosion of the rotor at some critical locations. The fatigue mechanisms of the turbine rotor are described. Key factors that influence missile probability are discussed. Rotor damage due to SCC is discussed and analyzed to evaluate the probability of the nuclear turbine rotor.
High Pressure Combustion Test Rig for 10 MW Full Scale Gas Turbine Combustors
Authors: Kroniger Daniel , Vinnemeier Philipp , Rudolf Christian , Wirsum Manfred
Published: September 2014

This paper reports about a high pressure combustion test rig which was designed and erected inside the laboratory of the Institute of Steam and Gas Turbine (IDG, RWTH Aachen University, Univ.-Prof. Dr.-Ing. Dieter Bohn) in the time period from 1992. The first cold start-up was done to test and adjust the complex infrastructure including monitoring and control. The first hot start-up followed in May 2009 with a can-type combustor for a 7 MWel gas turbine. Thereafter, different gas turbine combustors have been tested and optimized with regard to NOx emission and combustor stability (see Tanaka et al. [1]).

This test rig is designed to conduct combustion tests with unscaled gas turbine combustors with a thermal power of up to 10 MW and exhaust gas temperatures of up to 1350°C. The test rig is capable of achieving air inlet conditions of up to 24 bar, 550°C and 12 kg/s.

After a successful phase of operation, the test rig has been continuously modified and upgraded at the Institute for Power Plant Technology, Steam and Gas Turbines (IKDG, RWTH Aachen University, Univ.-Prof. Dr.-Ing. habil. Manfred Wirsum).

This paper introduces the current test rig. First, the test rig is classified in relation to similar test rigs by relevant literature. Thereafter, the test rig design and operation mode is presented in detail including a quality evaluation of the combustor inlet conditions. Furthermore, a steady-state simulation is set up. Based on its results, the theoretical operating ranges and limitations are identified and discussed.
Mechanical Behavior of Dissimilar Welds for Steam Turbine Rotors With High Application Temperature
Authors: Krojer Stefan , Sheng Shilun , Roos Eberhard , Klenk Andreas , Kern Torsten-Ulf
Published: September 2014

Fossil fired steam power plants of the latest generation require the elevation of steam parameters pressure and temperature to increase efficiency as well as to reduce greenhouse gas emissions. In order to achieve these goals for high temperatures, nickel base alloys could play an important role for steam turbine applications in the future. Due to technological and economical restrictions, their application in turbine rotors shall be restricted to the most heavily stressed regions. Dissimilar welds offer a known solution to combine nickel base alloys with ferritic/martensitic steels in this case.

Thermal mismatch and differences in high temperature performance of the applied base materials make it very difficult to evaluate the lifetime of such dissimilar welds. Depending on temperature and type of loading, different failure mechanisms can be observed. Further, the type of weld material plays a major role for the service behavior of the weld. Therefore, this paper describes standard creep and fatigue tests which were conducted to identify failure mechanisms and failure locations at the weld zone. To simulate the outcome of the creep tests, a modified Graham-Walles approach is used that also accounts for the different creep behavior of the heat affected zones compared to the base material. For the simulation of the fatigue tests, the model type CNOW (Chaboche-Nouailhas-Ohno-Wang) is used. The results contribute to better knowledge in designing dissimilar welds between nickel base alloys and martensitic steels under high temperature loading.
Assessment of a High-Order Discontinuous Galerkin Method for the Direct Numerical Simulation of Transition at Low-Reynolds Number in the T106C High-Lift Low Pressure Turbine Cascade
Authors: Hillewaert Koen , Carton de Wiart Corentin , Verheylewegen Guillaume , Arts Tony
Published: September 2014

An implicit time integration, high-order discontinuous Galerkin method is assessed on the DNS of the flow in the T106C cascade at low Reynolds number. This code, aimed at providing high orders of accuracy on unstructured meshes for DNS and LES simulations on industrial geometries, was previously successfully assessed on fundamental, academic test cases. The computational results are compared to the experimental values and literature, and the obtained flow field characteristics are discussed. Although adequate resolution is supposed to be attained, discrepancies with respect to the experiment are found. These differences were furthermore consistently found by all authors in the workshop on high-order methods for CFD. The origins are therefore conjectured to result from insufficient adequation between computational setup and experiments, as no modeling is assumed. A plan for further investigation is proposed.
An Approach for Predicting the Flow Regime in an Aero Engine Bearing Chamber
Authors: Kurz Wolfram , Bauer Hans-Jörg
Published: September 2014

The paper discusses an approach to predict the two-phase flow regime in an aero engine bearing chamber. In general, one of two distinct flow regimes can occur in a bearing chamber. At lower shaft speeds, the oil flow is only partially affected by the air flow, which is driven by the rotating shaft. At higher shaft speeds, however, the rotating air flow forces the oil film at the chamber walls to rotate, too. Thus, the two flow regimes correspond to two very different oil film distributions inside a bearing chamber presumably with significant consequences for the internal wall heat transfer. In order to determine the driving parameters for the flow regimes and the change between them, experiments were carried out with a bearing chamber test rig. With this test rig all relevant operating parameters as well as the geometry of the bearing chamber could be varied independently. The analysis of the experimental data allowed defining a general parameter which takes into account the chamber pressure, shaft speed, oil viscosity and chamber length. The influence of the oil flow rate and the overall dimensions are assessed qualitatively.
Determining the Effect of Bearing Clearance and Preload Uncertainties on Tilting Pad Bearings Rotordynamic Coefficients
Authors: Romero Quintini Juan C. , Pineda Saira , Matute José A. , Medina Luis U. , Gómez José L. , Diaz Sergio E.
Published: September 2014

Tilting Pad Journal Bearings (TPJB) are commonly used in high-speed and high-power turbomachines, due to their contributions in avoiding rotor instabilities. Studies related to the estimation of dynamic coefficients have been carried out considering nominal values of the geometric parameters (clearance and preload) for all bearing pads. However, the unavoidable uncertainties on these geometric parameters and, therefore their possible influence on the TPJB rotordynamic coefficients do not seem to have been discussed enough. In a previous work, a numerical study was conducted to examine the influence of preload and bearing clearance variations on a five-pad TPJB rotordynamic coefficient. The current work is an extension of that paper, considering at this time the Design of Experiments framework. By means of a 2k factorial design and ANOVA random effect model, uncertainties on bearing clearance and pad preload values are introduced in a standard numerical model (i.e. finite element model) used to estimate the direct and cross-coupled dynamic stiffnesses of the five pad TPJB. The influence on these dynamic coefficients, due to the variance of the aforementioned geometric parameters, is discussed and presented in graphical form in order to illustrate the sensitivity of the TPJB dynamic coefficients. Results derived from this study show that variations on loaded pads affect the direct dynamic coefficients, and unloaded pads variations influence the cross-coupled dynamic coefficients. This work contributes to the understanding of the sensitivity of TPJB dynamic coefficients to manufacturing tolerances.
Mean Velocity Scaling and Friction Coefficient Estimation for Rough Surface Turbulent Boundary Layers in Turbomachines
Authors: Shin Ju Hyun , Song Seung Jin
Published: September 2014

Based on flat plate results, mean velocity and friction coefficient estimation methods are proposed for rough surface turbulent boundary layers on axial compressor and turbine blades. The ratio of the displacement thickness to boundary layer thickness (δ*/δ) was first suggested by Zagarola and Smits (1998) for smooth pipe flows. The same parameter is proposed in this paper to scale the normalized mean velocity defect of smooth and rough surface flat plate turbulent boundary layers with zero, favorable, and adverse pressure gradients. The available mean velocity defect profiles of smooth and rough surface boundary layers from axial compressor and turbine blades are also scaled and compared to the flat plate results. Irrespective of the Reynolds number (Reθ), pressure gradient (K), and roughness (k), δ*/δ provides appropriate scaling for collapsing the flat plate and turbomachinery data. From the results, a new one-variable power law based on δ*/δ is proposed to estimate the mean velocity profile. The proposed power law can accurately estimate boundary layers on flat plates, compressor blades, and turbine blades. Finally, a new empirical Cf correlation is proposed for rough surface turbulent boundary layers under pressure gradients. The proposed Cf correlation is based on that of Bergstrom et al. (2005) and newly incorporates the acceleration parameter K. It can accurately estimate Cf in turbulent boundary layers of rough surface flat plates as well as those of smooth turbine blades.
Investigation of Non-Axisymmetric Endwall Contouring and 3D Airfoil Design in a 1.5 Stage Axial Turbine: Part I — Design and Novel Numerical Analysis Method
Authors: Poehler Thorsten , Niewoehner Jens , Jeschke Peter , Guendogdu Yavuz
Published: September 2014

This paper presents the results of the analysis of different 3D designs for the first stator and the rotor of a 1.5-stage turbine test rig. A tangential endwall contouring for the hub and the shroud, a bowed profile stacking, and a combination of those have been designed for the first stator. In addition a tangential endwall contouring has been designed for the hub of the unshrouded rotor. Part I of this two-part paper deals with the design process and the numerical analysis of the results. All designs have been optimized with the stage efficiency as the target function. For the design of the 3D stator vanes, the optimization led to an unexpected result: The secondary flow vortex strength increased. However, the secondary flow pattern has been rearranged and the exit flow angle has been homogenized. Although the stator losses increased, the stage efficiency also increased. Thus, a reduction of the rotor losses overcompensated the higher stator losses.

In order to understand how the 3D vanes affect the stator secondary flow pattern, a detailed analysis of vortex stretching and vortex dissipation is presented here. With this approach, the various impacts of the 3D designs on the secondary flow vortices’ strength can be quantified. In addition, the potential theory effect of the self-induced velocity is introduced here in order to explain the effects of a tangential endwall contouring on the trajectory of the pressure side leg of the horseshoe vortex. At the authors’ knowledge, both approaches are new for the analysis of turbine secondary flows.

The impact of the stronger but rearranged stator secondary flow on the rotor secondary loss development is analyzed by means of unsteady simulations. The results show that the rotor secondary flow can be effectively reduced through a proper stator secondary flow pattern. In part II of this paper, the analysis of extensive experimental results validates and supplements the numerical analysis.
Development of Thrust Bearings With High Specific Load
Authors: Sumi Yuki , Sano Takeshi , Shinohara Tanehiro , Tochitani Naoto , Otani Yukihiro , Yamashita Kazuhiko , Nakano Takashi
Published: September 2014

Steam turbine is now facing strict market demands for further improvements in efficiency. To meet such demands, thrust bearing with high specific load makes a huge contribution to improvements in efficiency. Because the smaller thrust dummy diameter of rotor can be adopted and leakage flow through the thrust dummy can be reduced, in case thrust bearing allows higher specific load and allowable thrust force becomes bigger. MHI developed the thrust bearing with high specific load, which PEEK (polyether-ether-ketone) resin pad is applied. Both the laboratory bearing tests and long-time operation (from 2007) in MHI’s internal combined cycle power plant have been successfully accomplished. This PEEK resin thrust bearing is going to be applied to the actual plant. This article describes the performance and characteristics of PEEK resin thrust bearing and summary of laboratory test and long-time operation.
MT30: The Heart of Future Integrated Power and Propulsion Systems
Authors: Rath Oliver
Published: September 2014

The MT30 has been developed specifically for 21st century marine propulsion and has now been applied in a wide range of different propulsion system configurations in the US Navy, the UK Royal Navy and the Republic of Korea Navy. Both naval and commercial marine propulsion systems are increasingly seeking more power from fewer prime movers to facilitate lower cost of ownership. In naval systems, the move to partial or full-electric propulsion for larger escorts and the introduction of single boost gas turbines for smaller escorts has allowed a reduction in the number of installed prime movers, while retaining and often enhancing survivability and redundancy. The Rolls-Royce MT30 marine gas turbine can be regarded as an enabling technology in this area to allow a wide variety of propulsion system options to be realised.

This paper describes the current trends in Naval propulsion systems with particular focus on the platform design, operational and through-life benefits of the MT30 in the context of different system arrangements. A variety of different systems are covered with a particular focus on hybrid electromechanical and all-electric systems.
Fuel System With Variable Speed Pump to Improve Thermal Management Ability for Aircraft Engines
Authors: Oba Daisuke , Gonda Yukinori
Published: September 2014

Now, fuel systems on aircrafts/engines are required to rapidly improve thermal management technology. The proposed variable speed pump systems are a unique solution to improve the thermal management of aircrafts/engines without requiring a major change in the conventional interface between a jet engine and a fuel system. Concurrently, the proposed systems have the possibility to improve SFC by about 0.25% during cruise on a small turbofan engine due to reducing inefficient energy consumption. These systems lead to minimize the conventional cooling mechanisms and contribute to the additional improvement of SFC. The purpose of this paper is to show the characteristics of the proposed systems.
Process Monitoring for Manufacturing of Critical Aero Engine Components: An Overview
Authors: Veselovac Dražen , Gierlings Sascha , Brockmann Matthias
Published: September 2014

Modern production systems stand out due to an increasing degree of capacity utilization of the efficiency available through the production process. As working on a technological threshold as well as on a complex task comes along with an increase of susceptibility to failure, process monitoring is an important means to avoid damage to machines, tools, and component parts and a consequent machine downtime. In order to bring about detection of tool breakage, overload and tool wear, we use different sensor and monitoring systems which are adjusted to the process in the best possible way. This paper gives an overview of existing process monitoring solutions, especially in the field of aero engine manufacturing.
Experimental Investigation of Nonperiodic Endwall Film Cooling in Neighboring Passages With Upstream Rotating Flow
Authors: Zhang Yang , Yuan Xin
Published: September 2014

The distribution of film-cooling holes is considered to be the same between neighbouring high pressure turbine passages in most cascade experiments. Because of the difference in accounts of combustors and vanes, however, the flow fields of neighbouring passages are completely different. The secondary flow, especially the passage vortex, is dominated by the upstream inlet rotating flow whose relative flow direction is the reverse between the neighbouring vane passages. Specific rotating directions introduce new challenges in film-cooling design. The present experiment compares three groups of endwall film-cooling with anticlockwise rotating flow inlets at different clocking positions, and the film-cooling effect is analysed to investigate the effects of inlet rotating flow. The inlet flow condition of neighbouring passages is simulated by switching the position of the swirler by means of which rotating inlet flow conditions in different positions are achieved.

The GE-E3 airfoil is used in the cascades, with a scaled-up factor of 2.2. The inlet Reynolds number is 3.5×105 and the Mach number is 0.1. The effects of the blowing ratio and relative positions of the swirler are investigated in the experiment. Adiabatic film-cooling effectiveness is probed by using pressure-sensitive painting (PSP). The coolant is simulated by nitrogen by which a density ratio of around 1.0 can be achieved. Fan-shaped film-cooling holes are introduced into the endwall surface as well as trailing edge discharge holes. The cooling performance of the combustor-turbine gap leakage flow is also considered simultaneously.

Conclusions are as follows: (1) the anticlockwise direction of rotating flow influences the endwall film-cooling effectiveness, especially for the upstream part of the endwall which is mainly covered by the leakage flow; (2) the film-cooling effectiveness in the neighbouring passages differs depending on the position of the inlet rotating flow core; (3) the film-cooling performance at the downstream part of the endwall is partly influenced by the upstream rotating flow inlet as well.
3D Unsteady RANS Simulation of the Interaction Between Fan Stage, Struts and Bifurcations
Authors: Holewa Axel , Guérin Sébastien , Weckmüller Christian , Enghardt Lars
Published: September 2014

Struts and bifurcations installed in the bypass duct of aeroengines can deteriorate the aerodynamic and acoustic performances of the fan and therefore should be accounted for in the design process. This paper compares two 3-D unsteady RANS simulations of a fan model obtained respectively for an isolated and an installed configuration. In the installed case the strut–bifurcation system creates a strong disturbance of the steady flowfield. This involves a deformation of the rotor wakes during their convection, so that their impingement on the stator generates pressure fluctuations acting as sound sources with strong scattered azimuthal mode orders. The scattering is found by analyzing the acoustic field upstream and downstream of the fan stage. The present results are obtained while the rotor is supersonic (Mtip,rel ≈ 1.24). Since all the blades are identical, no frequency scattering (buzz-saw) does happen in the simulations.
Particularities of Blading Free Resonance Design for Heavy Duty Gas Turbines With Circumferential Rotor Grooves
Authors: Putchkov Igor , Arkhipov Alexander , Moskovskikh Valery , Kissel Harald , Laqua Alexander
Published: September 2014

Blades for heavy duty engines with circumferential rotor grooves are designed such that radial contact is made between the blade teeth and rotor groove at steady state operation conditions. However, sometimes circumferential contact arises between neighboring blade shanks, which is often caused by blade root /rotor thermal expansion. In this case, the radial fixation will give the lower limit of blade frequency band, and the circumferential will give the upper one. The Blade frequency difference between these two fixations might reach about 200–500 Hz depending on blade airfoil and root sizes.

When some excitation source (e.g., vane passing frequencies caused by up-stream and down-stream vane counts) has a frequency level situated between blade frequencies caused by radial and circumferential contact, such a case is the subject of the proposed approach.

In order to assess how strongly the blade might be fixed under different conditions and how long it might be in resonance during engine start-up and subsequent loading, a 3D elastic-plastic transient analysis and corresponding frequency calculation of blade/rotor assembly is used.

At engine start-up the circumferential (lateral) contact between neighboring blade roots is insignificant, and the radial contact between the rotor and the blade is dominant. The lateral contact spot between neighboring blade attachments during start-up appears due to different rates of blade/rotor heating.

Further heating leads to an increase of the lateral contact spot areas. The closing of these contact surfaces starts from the outer root edge and spreads toward the inner one, leading to an increase of assembly natural frequencies.

Engine loading and further heating lead to the appearance of a circumferential gap between the surfaces, causing the lateral contact to disappear during steady state. The blade root coupling switches again to the usual radial contact state, with the corresponding reduction of natural frequencies.

Because the described phenomenon might occur for some time during every start-up and shut-down (from several minutes to couple of hours), it becomes even more severe from a dynamics standpoint if some natural frequency of coupled system crosses the exciting frequency.

Examples of assembly frequency tuning are presented.
Intersplat Oxidation of Atmospheric Plasma Sprayed MCrAlY Coatings
Authors: Eriksson Robert , Yuan Kang , Johansson Sten , Peng Ru Lin
Published: September 2014

MCrAlY coatings and thermal barrier coatings (TBC) are commonly used in gas turbines to prolong the life of structural parts. The atmospheric plasma spray (APS) process yields coatings with a typical splat-on-splat structure which oxidizes at intersplat boundaries during high-temperature exposure. A study was performed to establish the influence of intersplat oxidation on Al depletion. It was found that the β-depletion based life may be overestimated by a factor of 1.8–18 if intersplat oxidation is not considered. Two different mechanisms of intersplat oxidation were observed: At high temperature (1050 °C), a fraction of the intersplat boundaries remained in contact with the coating surface and oxidized with the same kinetics as the surface oxides. At lower temperature (900 °C), intersplat oxidation occurred by considerable slower growth rates than surface oxidation. The mechanisms behind intersplat oxide growth was further studied by O diffusion calculations.
Experimental Investigations of Effects of Centrifugal Compressor Impeller Design on Noise Characteristics
Authors: Ha Kyoung-Ku , Lee Chang-ha , Park Yong-sun , Kang Shin-hyoung , Park Chi-young , Yang Hyun-sub
Published: September 2014

The subject of this study is a centrifugal compressor for fuel-cell vehicles which produces compressed air and sends it to the cathode channels of a fuel-cell stack. It uses up a lot of electricity and it is the only component in the processing system that has a rotating part moving a high angular velocity. So, it is important to improve the centrifugal compressor in efficiency and noise respects. As demand for quiet and comfort of vehicles increases recently, it becomes more and more important for the compressor to achieve low noise level. But it is difficult to design a suitable compressor with a conventional design method, which was formulated to provide highly efficient operation at the design point without considering the noise. Actually, the noise of a compressor is hard to be considered in the early steps of the design procedure because of a lack of information. So, this study aims to describe noise characteristics of centrifugal compressors experimentally and to pull noise considerations into a design procedure of the centrifugal compressor.

According to previous studies, a tonal component leads to overall noise of a compressor in normal operation and there is a close connection between the instability intensity and the circumferential flow fluctuations of an impeller. Therefore an experimental study was designed to check the aero-acoustic characteristics of the impeller. An existing compressor was modified to install pressure transducers at the inlet and outlet of the impeller. And two microphones were installed to measure noise signals of the compressor in a sealed room. Tests were carried out to investigate the phenomena governing the overall noise and the dominant noise source of the centrifugal compressor. Then pressure fluctuations, noise signals and spectra of them were examined closely. After that, several impellers varying exit blade angles and design flow coefficients were tested also. They were all designed to satisfy the same pressure performance at a design mass-flow rate. Then investigations into the noise characteristics were carried out to find out effects of the impeller design variables on them. The results show that a large value of a blade angle is good for efficiency and noise level of the compressor. It is expected to be an optimal value to improve noise characteristics in terms of the design flow coefficient. The experimental facility, conditions and the results were described in this paper minutely.
The Study of Tip Clearance of a Wide-Chord Fan Blade of a High Bypass Ratio Turbo-Fan Engine
Authors: Chai Xianghai , Han Pinlian , Shi Tongcheng , Wang Zhiqiang
Published: September 2014

The wide-chord swept fan blade (WCSFB) has been extensively used in a advanced high bypass ratio turbofan engines. This paper explores the nature of WCSFB tip clearance. From the static analysis, it is found that the tip radial clearance at leading and trailing edge of WCSFB will be reduced with either bending or torsional deformation of the blade. And the change of the tip radial clearances varies with the twist angle.

In this study, dynamic response of the WCSFB with different angular accelerations of the engine has been analyzed. It shows that when the angular acceleration of the fan rotor reaches a certain level, considerable bending and torsional deformation of the blade will occur, accompanied by the reduction of the tip radial clearance, which may lead to abnormal rubbing/impact between the blade tip and the casing. This may cause severe consequence for the blade and casing of the engine. The numerical simulation results show that the rubbing/impact between the WCSFB tip and the casing under angular acceleration loads can lead to local buckling of the tip leading edge of the blade, which will cause severe damage at the blade tip. Moreover, the influence of vibration and mass imbalance of the rotor on the fan blade tip clearance is also analyzed.

In this paper, the results of a rig test under irregular acceleration for the WCSFB rotor is also presented, which validates the analytical results. The numerical simulation and test results will assist the blade tip clearance design to reflect the nature of the WCSFB under irregular acceleration to ensure safety.
Investigation of Filtered Rayleigh Scattering Techniques for Rig Testing Diagnostics
Authors: Estevadeordal Jordi , Opaits Dmitry , Kalra Chiranjeev
Published: September 2014

A laboratory investigation of Filtered Rayleigh Scattering (FRS) techniques for high-resolution and high-accuracy temperature measurements in rig tests with high pressures and temperatures and combustion is presented.

Imaging techniques based on filtered Rayleigh scattering have the potential for two-dimensional (2D) and near wall measurement of gas velocity and temperature fields among other properties. For gas temperature measurements, laser Rayleigh scattering from gas molecules are typically captured with an ICCD camera and temperature can be inferred from the number density measured from the image intensities. The accuracy challenges associated with property spatial variations, gas composition, and pressure and temperature conditions are investigated for the rig test environments.

Representative examples including mixing layer, jet and vortex flows and flame and combustion tests are presented.
Prediction of Transitional and Separated Boundary Layers in a Compressor Cascade
Authors: Kamin Manu , Mathew Joseph
Published: September 2014

Numerical simulations were performed of experiments from a cascade of stator blades at three low Reynolds numbers representative of flight conditions. Solutions were assessed by comparing blade surface pressures, velocity and turbulence intensity along blade normals at several stations along the suction surface and in the wake. At Re = 210,000 and 380,000 the laminar boundary layer over the suction surface separates and reattaches with significant turbulence fluctuations. A new 3-equation transition model, the k-kL-ω model, was used to simulate this flow. Predicted locations of the separation bubble, and profiles of velocity and turbulence fluctuations on blade-normal lines at various stations along the blade were found to be quite close to measurements. Suction surface pressure distributions were not as close at the lower Re. The solution with the standard k-ω SST model showed significant differences in all quantities. At Re = 640,000 transition occurs earlier and it is a turbulent boundary layer that separates near the trailing edge. The solution with the Reynolds stress model was found to be quite close to the experiment in the separated region also, unlike the k-ω SST solution. Three-dimensional computations were performed at Re = 380,000 and 640,000. In both cases there were no significant differences between the midspan solution from 3D computations and the 2D solutions. However, the 3D solutions exhibited flow features observed in the experiments — the nearly 2D structure of the flow over most of the span at 380,000 and the spanwise growth of corner vortices from the endwall at 640,000.
Performance Improvement of a Heavy Duty GT: Adiabatic Effectiveness Measurements on First Stage Vanes in Representative Engine Conditions
Authors: Andrei Luca , Facchini Bruno , Caciolli Gianluca , Picchi Alessio , Tarchi Lorenzo , D’Ercole Michele , Innocenti Luca , Russo Alessandro
Published: September 2014

Nowadays total inlet temperature of gas turbine is far above the permissible metal temperature; as a consequence, advanced cooling techniques must be applied to protect from thermal stress and to reduce the risk of creep failure, oxidation and corrosion of components located in the high pressure stages, such as first vane. Film cooling has been widely used to control temperature of high temperature and high pressure vanes. In a film cooled vane the air taken from last compressor stages is ejected through discrete holes to provide a cold layer between hot mainstream and turbine components. A comprehensive understanding of phenomena concerning the complex interaction of hot gases with coolant flows in a vane passage plays a major role in the definition of a well performing film cooling scheme.

The aim of this study is the measurement of adiabatic effectiveness on the first stage vane of a heavy duty GT by means of coolant concentration technique based on Pressure Sensitive Paint (PSP). The investigation of coolant distribution on airfoils and platforms was done in order to make feasible possible optimizations and to validate numerical design tools. The experimental analysis was performed on a static test article replicating an annular sector made up of two cooled airfoils and three passages. An actual first stage vane (scale 1:1) with complete internal cooling scheme has been tested at different coolant conditions and imposing two values of density ratio (DR = 1.0;1.5). Film protection was generated by a showerhead on the leading edge and by cylindrical holes on pressure and suction side and on the platforms; finally a cutback with elongated pedestals was employed for the protection of the pressure side trailing edge. Results, reported in terms of detailed 2D maps of film cooling effectiveness and averaged trends, point out the effect of coolant-to-mainstream mass ratio and density ratio. Beyond the results obtained in this specific vane geometry, the use of PSP was proven to be a promising technique for direct measurements on real geometries: as a matter of fact, the opportunity to get detailed results of pressure and adiabatic effectiveness distributions is of outstanding importance for the design and optimization of vanes and blades cooling systems.
An Experimental Investigation of the Influence of Flash-Back Flow on Last Three Stages of Low Pressure Steam Turbines
Authors: Shibukawa Naoki , Iwasaki Yoshifumi , Takada Yoshiaki , Murakami Itaru , Suzuki Takashi , Fukushima Takao
Published: September 2014

A shutdown operation of a large size steam turbine could possibly cause flashing phenomena of the pooled drain water in low-pressure heaters. The boiled steam is sometimes in the same amount as the main flow in the case where shutdown is executed during low load conditions, and returns to the steam flow path through the extraction lines. A series of experimental work with a subscale model turbine facility has been carried out to investigate the vibration stress behavior, and the steady and unsteady pressures under the flashing back conditions. It was observed that the blades of the two stages before the last stage (L-2) and a stage before the last stage (L-1) presented their peak vibration stresses immediately after the flash-back flow reached the turbine. In the meantime, the vibration stresses of the last stage (L-0) blades were reduced for a few tens of seconds. It can be thought that the flash-back flow pushed out the reverse flow region around the L-0 blades and allow the blades to be more stable. A detailed examination with measured data of the L-2 blade explained that, as long as the flash-back flow has small wetness, the blade is excited in its specific vibration modes in larger than 8th harmonic of rotational speed, but once the flash back flow carries water droplets, the fluid force in random frequencies remarkably increases and excites the blade in less than 7th harmonic range.
Differential Mobility Spectrometer Particle Emission Analysis for Multiple Aviation Gas Turbine Engine Exhausts at High and Low Power Conditions and a Simulated Gas Turbine Engine Exhaust
Authors: Walters David M. , Sevcenco Yura A. , Crayford Andrew P. , Marsh Richard , Bowen Philip J. , Johnson Mark P. , Williams Paul I.
Published: September 2014

This paper presents particulate matter (PM) size spectral measurements, analysed to determine number and mass concentration, taken using a fast response differential mobility spectrometer (DMS500). Exhaust samples from multiple commercially available large civil aviation gas turbine engines and an auxiliary power unit operating at high and low engine power conditions were studied, in addition to a simulated aviation gas turbine exhaust, which was operated to exhibit specific PM output. Results show all exhaust sources as having similar bi-modal PM size spectra with both number and mass concentrations highly dependent on the emission source and the sampling testing condition. When operating at high power levels all of the tested gas turbine emission sources, with the exception of the 2-stage combustor design, generally produced distributions of PM which exhibited larger average mean diameter particle sizes and higher number and mass concentrations.
Evaluation of the Influence of Volute Roughness on Turbocharger Compressor Performance From a Manufacturing Perspective
Authors: Javed A. , Kamphues E.
Published: September 2014

This paper presents a comprehensive surface roughness evaluation of a mass-produced turbocharger centrifugal compressor for automotive application. The aim is to study the impact of surface roughness on compressor performance and manufacturability of the volute. Surface roughness data for different components has been obtained from drawing specifications and sample measurements. Detailed compressor performance evaluation has been made in three parts using CFD. In the first part, the overall compressor performance variation has been simulated from stall to choke over a speed line; initially with all smooth surfaces and later, with rough surfaces. The second part decomposes the performance variation into its sources by simulating each compressor component individually with its specific roughness. Moreover, a performance sensitivity analysis has been conducted to identify the components most responsive to limited surface roughness deviation. In the third part, the volute is subdivided into five sections and a performance sensitivity analysis has been performed by sequentially varying the surface roughness for each section within a particular deviation range. The analysis revealed the sections which essentially require smoothing via sand core coating. Lastly, the roughness specifications have been reviewed especially for the volute, keeping in view the benefits the new specifications may have on overall compressor performance and manufacturing costs.
Modeling Curvature Effects on Turbulence Transition for Turbomachinery Flows
Authors: Rinaldi Enrico , Raspopov Roberto Suarez , Colonna Piero , Pecnik Rene
Published: September 2014

The rotation-curvature correction proposed by Spalart and Shur is implemented in the γ–Re~θt transition model of Langtry and Menter. The correction term modifies the turbulence production such that it is damped in convex curvatures and enhanced otherwise. The curvature corrected transition model is first validated on a U-shaped channel flow for which experimental data and reference numerical results are available. The improved prediction capability is then assessed on a series of well documented two-dimensional turbomachinery problems. A better agreement with experimental data is observed in the simulation of the transition onset, which leads to an improved estimation of parameters of practical interest such as the heat transfer and pressure coefficient.
Research on the Coupling Mechanism Between Alternating Flow Pattern and Valve Stem System of Steam Turbine Control Valve
Authors: Zeng Li-Fei , Liu Guan-wei , Mao Jing-ru , Wang Shun-sen , Zhang Cong , Yu Xin , Zhang Jun-jie , Xu Ya-tao
Published: September 2014

Control valve is an accident prone equipment in high-parameter steam turbine, and its safety directly influences the economy and safety of the unit. In this study, a control valve of a 600 MW subcritical unit used in the power plant was investigated to reveal the mechanism of flow induced vibration of the control valve. It is found that the intermittent vibration of the control valve is a fluid-solid interaction phenomenon, which occurs in middle-opening and transonic flow condition. The phenomenon is a variable damping and nonlinear vibration for the valve stem system. The experimental results show that as the valve head tilts to different positions, the pressure fluctuation at the valve seat changes significantly at the same time. Unsteady numerical simulation is conducted when valve head is in the center and tilts toward three different directions with the same angle. The results indicate that the separation point between the high jet flow and valve head is changing with time. The thick boundary layer caused by transonic flow and the moving high-pressure region induced by impinging jet flow are the two main reasons for the flow pattern alternation. The average unbalanced force of fluid acting on valve head varies as the flow pattern alternates. And its direction is from center to the narrower side of the annular channel in the oblique section when valve head is tilted.