bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation of Steam Turbine Exhaust Diffuser Flows and Their Three Dimensional Interaction Effects on Last Stage Efficiencies
Authors: Tanuma Tadashi , Sasao Yasuhiro , Yamamoto Satoru , Niizeki Yoshiki , Shibukawa Naoki , Saeki Hiroshi 
Published: September 2014

The purpose of this paper is to present the methodology for high accurate aerodynamic numerical analysis and its design application of steam turbine down-flow type exhaust diffusers including their three dimensional flow interaction effects on last stage efficiencies.
Down-flow type exhaust diffusers are used in large scale steam turbines from 200MW to 1400MW class units for power generation plants mainly. The axial length of typical 1000MW class large scale steam turbines is about 30–40m and its four low pressure (LP) down-flow type exhaust diffusers occupy a large amount of space. The axial lengths and diameters of these exhaust diffusers contribute significantly to the size, weight, cost, and efficiency of the turbine system. The aerodynamic loss of exhaust hoods is nearly the same as that of stator and rotor blading in LP steam turbines, and there remains scope for further enhancement of steam turbine efficiency by improving the design of LP exhaust hoods.
In the design process of last stages, the average static pressure in the last stage exit is introduced accurately using numerical analysis and experimental data of model steam turbines and model diffusers. However the radial and circumferential unsteady aerodynamic interaction effects between last stages and their exhaust diffusers are still need to be investigated to increase the accuracy of the interaction effect on the last stage efficiencies.
This paper presents numerical investigation of three dimensional wet steam flows including three dimensional flow interaction effects on last stage efficiencies in a down-flow type exhaust diffuser with non-uniform inlet flow from a typical last stage with long transonic blades designed with recent aerodynamic and mechanical design technology.
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.
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.
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.
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.
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.
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.
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.