bluuebunny/crossref_metadata_2025_split huggingface dataset:
PLIF and Temperature Measurements in an Actively Forced Swirl-Stabilized Spray Combustor
Authors: Santhanam V. , Knopf F. C. , Acharya S. , Gutmark E. 
Published: December 2014

The effect of synchronized liquid fuel injection into combustion zones within excited air vortices was studied using Planar Laser Induced Fluorescence (PLIF) imaging of OH. A small-scale model of a swirl-stabilized combustor was investigated. Both the liquid fuel and air streams were forced at a normalized frequency (St) of approximately 6. Air vortices were produced by acoustically forcing the air stream. The liquid fuel was modulated at the same frequency and injected at different phase angles relative to the air vortex formation. Air was forced at two levels, and both non-swirling and swirling flow situations (Swirl number of 0.3) were considered. Instantaneous, and phase-averaged PLIF images of OH, and time-averaged temperature measurements were obtained for different phase differences between the two forcing signals.
The PLIF images indicated that with forcing there was an increase in the radial distribution of the reaction zones and a decrease in the height of the flame above the nozzle exit for both non-swirling and swirling conditions. Swirl also produced better mixing along the radial direction for low forcing amplitudes. The phase difference between the two forcing signals produced a significant change in the reaction zones particularly at a low forcing level and with swirl. The PLIF images indicated that the inner region of the flame was the primary reaction zone. When intense combustion occurred at the flame center, high vaporization rate prevented fuel droplets from reaching the external shear layer. The effect of the outer shear layer on combustion was enhanced by swirl, as the swirl increased the droplet dispersion away from the axis.
Up-Rated Reheat Gas Turbine for the Repowering of Steam Power Plants
Authors: Negri di Montenegro G. , Peretto A. , Mantino E. 
Published: December 2014

In the present paper, a thermoeconomic analysis of combined cycles derived from existing steam power plants is performed. The gas turbine employed is a reheat gas turbine. The increase of the two combustor outlet temperatures was also investigated.
The study reveals that the transformation of old conventional fossil fuel power plants in combined cycle power plants with reheat gas turbine supplies a cost per kWh lower than that of a new combined cycle power plant, also equipped with reheat gas turbine. This occurs for all the repowered plants analyzed.
Moreover, the solution of increasing the two combustor outlet temperatures resulted a strategy to pursue, leading, in particular, to a lower cost per kWh, Pay Back Period and to a greater Internal Rate of Return.
Detailed Analysis of the Thermal Wall Heat Load in Annular Combustors
Authors: Krebs Werner , Walz Günther , Hoffmann Stefan , Judith Hans 
Published: December 2014

A detailed thermal analysis involving both measurements and calculations has been carried out in order to determine the wall heal load and to optimize the amount of cooling air for an annular combustor. In calculations, the convective wall heat flux has been detemined by application of a 3D Navier-Stokes Code. Furthermore, the radiation exchange between the hot combustion gases and the liner has been calculated using a multidimensional spectral approach.
Although a quite high thermal power density is found within the combustion chamber the wall heat load is at a low level. Values are well below 80 kW/m2, due to the application of ceramic tiles which have a low thermal conductivity. The wall heat load is dominated by radiation emitted in the lower gas radiation bands (λ < 2.9 μm). The convective wall heat flux is nearly balanced out by the sealing air which is discharged through gaps between the ceramic tiles. The cooling effect of the sealing air, however, is strongly influenced by the 3D near wall flow field in the combustion chamber.
Influence of Turbulence Intensity on Annular Turbine Stator Aerodynamics at Low Reynolds Numbers
Authors: Matsunuma Takayuki , Abe Hiroyuki , Tsutsui Yasukata 
Published: December 2014

The aerodynamic characteristics of turbine cascades are thought to be relatively satisfactory due to the favorable pressure of the accelerating flow. But within the low Reynolds number region of 6×104 where the 300kW ceramic gas turbines which are being developed under the New Sunshine project of Japan operate, the characteristics such as boundary layer separation, reattachment and secondary flow which lead to prominent power losses can not be easily predicted.
In this research, experiments have been conducted to evaluate the performance of an annular turbine stator cascade, especially focused on the influence of inlet turbulence intensity at low Reynolds numbers. The Reynolds number, based on inlet condition, was varied from 2×104 to 12×104. The turbulence intensity was changed between 0.5% and 8.9% by setting turbulence generation sheets. The wake of the cascade was measured using a 5-hole pressure probe and a single element hot-wire anemometry.
The Reynolds number was a determinative important parameter, while the turbulence intensity was found to have an insignificant effect on the overall total pressure loss of annular turbine stator at low Reynolds numbers. However, the increase in separation zone on suction surface and the decrease of passage vortices near the endwalls were observed locally with the increase in the inlet turbulence intensity. Instantaneous velocity signals proved the transformation of the flow structure in separation zone. The increase in profile loss (separation) and the decrease in net secondary loss (passage vonices) offset each other. Therefore, the net overall loss remains almost constant.
On the Development and Application of the FRAP® (Fast-Response Aerodynamic Probe) System in Turbomachines: Part 2 — Flow, Surge and Stall in a Centrifugal Compressor
Authors: Roduner Christian , Kupferschmied Peter , Köppel Pascal , Gyarmathy George 
Published: December 2014

The present paper, Part 2 of a trilogy, is primarily focussed on demonstrating the capabilities of a FRAP® system configuration based on the simplest type of fast-response probe. A single cylindrical probe equipped with a single pressure sensor is used to measure absolute pressure and both velocity components in an essentially two-dimensional flow field. The probe is used in the pseudo-3-sensor mode (see Part 1). It is demonstrated that such a 1-sensor probe is able to measure high-frequency rotor-governed systematic fluctuations (like blade-to-blade phenomena) alone or in combination with flow-governed low-frequency fluctuations as rotating stall (RS) and mild surge (MS). However 3-sensor probes would be needed to measure stochastic (turbulence-related) or other aperiodic velocity transients.
The data shown refer to the impeller exit and the vaned diffuser of a single-stage high-subsonic centrifugal compressor. Wall-to-wall probe traverses were performed at the impeller exit and different positions along the vaned diffuser for different running conditions. The centrifugal compressor was operated under stable as well as under unstable (pulsating or stalled) running conditions. The turbomachinery oriented interpretation of these unsteady flow data is a second focus of the paper. A refined analysis of the time-resolved data will be done in Part 3 where different spatial/temporal averaging methods are compared.
Two different averaging methods were used for the data evaluation. Impeller based ensemble averaging for blade-to-blade systematic fluctuations (with constant period length at a constant shaft speed) and flow-based class averaging for the relatively slow MS and RS with slightly variable period length.
Due to the ability of fast-response probes to simultaneously measure velocity components as well as total and static pressure, interesting insights can be obtained into impeller and diffuser channel flow structures as well as into the time behavior of large-domain phenomena as RS and MS.
Effects of Hole Shape on Film Cooling With Large Angle Injection
Authors: Kohil Atui , Bogard David G. 
Published: December 2014

In this study the film cooling performance of a single row of discrete holes inclined at an injection angle of 55° is investigated at a density ratio of DR = 1.6. Three different hole geometries were used in this study, a round hole and two shaped holes. One shaped hole had forward and lateral expansions of 15°, and the other a 15° lateral with a 25° forward expansion. For reference, a round hole with an injection angle of 35° was also tested. The film cooling performance of each hole shape was evaluated using adiabatic effectiveness, thermal field, and velocity field measurements.
The shaped holes showed higher spatially averaged adiabatic effectiveness than the round hole over the whole range of momentum flux ratios (I) investigated. The effectiveness values for the shaped holes were only marginally better than the round hole at the low I, but at the high I, the shaped holes performed much better than the round hole. The temperature and velocity field measurements near the hole exit suggest that there is a slight detachment of the jet from the wall for the round hole, while the jets remain attached for the two shaped holes. The shaped hole with the larger forward expansion had a warmer jet with a higher trajectory at the hole exit suggesting ingestion of mainstream fluid and flow separation within the hole.
Overshoot of the Rankine Vortex Formed in the Flow Field Behind the Inlet Guide Vane of Centrifugal Compressors
Authors: Chen Y. N. , Hagelstein D. , Kassens I. , Hasemann H. , Haupt U. , Rautenberg M. 
Published: December 2014

This paper is aimed to analyze the experimental results obtained by Kassens and Rautenberg (1998) and Kassens (1997) concerning the overshoot of the rotating velocity field behind the IGV. Since the IGV used in the present investigation has the form of a disc in the closed condition of the blades, the vorticity field of the rotating flow behind the outlet edge of the IGV can be determined by means of the streamline deflection in this IGV, whose function as an actuator disc does not need to be used. The potential-vortex field generated by these streamlines out of the IGV is calculated with good accuracy compared with the experimental results.
The further development of the vorticity field mentioned into the distribution of the tangential velocities can be derived from the diffusion of the vorticity, but with an inaccuracy caused by the overshoot of the Rankine vortex. This overshoot originates from the potential vortex field and travels towards the vortex core, which acts as a rigid body rotation.
The overshoot degenerates downstream from the outlet of the IGV due to strong damping incorporated in its unusual velocity field. Its disappearance introduces the formation of the orderly Lamb-Oseen vortices, whose theoretical property coincides well with the experimental result. Thus, the overshoot plays an active role for the loss in the total pressure in the central region of the rotating flow generated by the IGV.
Part Load Operation of a Combined Plant Using a Closed Circuit Blade Cooled Gas Turbine
Authors: Marushima Shin’ya , Higuchi Shin’ichi , Ikeguchi Takashi 
Published: December 2014

Closed circuit blade cooled gas turbines are drawing attention because of their efficiency compared with that of a conventional air cooled gas turbine. In a closed circuit blade cooled gas turbine, coolant is not discharged into the gas path, so dilution of the hot gas stream, rotor blade pumping loss and pressure loss due to mixing of coolant with the stream are drastically reduced.
In this paper, two types of combined cycles, a closed circuit steam cooled gas turbine combined cycle CCSC, and a closed circuit air cooled gas turbine combined cycle CCAC are analyzed to verify the part load performance.
The blade temperatures of both combined cycles are lower than at full load, that is, the blades are sufficiently cooled. Under 30% load in the CCSC, the coolant steam pressure is lower than the main gas stream because of a shortage of coolant steam.
Performance of Pre-Swirl Rotating-Disc Systems
Authors: Karabay Hasan , Pilbrow Robert , Wilson Michael , Owen J. Michael 
Published: December 2014

This paper summarises and extends recent theoretical, computational and experimental research into the fluid mechanics, thermodynamics and heat transfer characteristics of the so-called cover-plate pre-swirl system. Experiments were carried out in a purpose-built rotating-disc rig, and the Reynolds-averaged Navier-Stokes equations were solved using 2D (axisymmetric) and 3D computational codes, both of which incorporated low-Reynolds-number k-ε turbulence models. The free-vortex flow, which occurs inside the rotating cavity between the disc and cover-plate, is controlled principally by the pre-swirl ratio, βp: this is the ratio of the tangential velocity of the air leaving the nozzles to that of the rotating disc. Computed values of the tangential velocity are in good agreement with measurements, and computed distributions of pressure are in close agreement with those predicted by a one-dimensional theoretical model.
It is shown theoretically and computationally that there is a critical pre-swirl ratio, βp,crit, for which the frictional moment on the rotating discs is zero, and there is an optimal pre-swirl ratio, βp,opt, where the average Nusselt number is a minimum. Computations show that, for βp < βp,opt, the temperature of the blade-cooling air decreases as βp increases; for βp > βp,opt, whether the temperature of the cooling air increases or decreases as βp increases depends on the flow conditions and on the temperature difference between the disc and the air. Owing to the three-dimensional flow and heat transfer near the blade-cooling holes, and to unquantifiable uncertainties in the experimental measurements, there were significant differences between the computed and measured temperatures of the blade-cooling air. In the main, the 3D computations produced smaller differences than the 2D computations.
Aerothermal Investigations of Mixing Flow Phenomena in Case of Radially Inclined Ejection Holes at the Leading Edge
Authors: Bohn Dieter E. , Kusterer Karsten A. 
Published: December 2014

A leading edge cooling configuration is investigated numerically by application of a 3-D conjugate fluid flow and heat transfer solver, CHT-Flow. The code has been developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It works on the basis of an implicit finite volume method combined with a multi-block technique.
The cooling configuration is an axial turbine blade cascade with leading edge ejection through two rows of cooling holes. The rows are located in the vicinity of the stagnation line, one row is on the suction side, the other row is on the pressure side. The cooling holes have a radial ejection angle of 45°. This configuration has been investigated experimentally by other authors and the results have been documented as a test case for numerical calculations of ejection flow phenomena.
The numerical domain includes the internal cooling fluid supply, the radially inclined holes and the complete external flow field of the turbine vane in a high resolution grid. Periodic boundary conditions have been used in the radial direction. Thus, end wall effects have been excluded. The numerical investigations focus on the aerothermal mixing process in the cooling jets and the impact on the temperature distribution on the blade surface. The radial ejection angles lead to a fully three dimensional and asymmetric jet flow field. Within a secondary flow analysis it can be shown that complex vortex systems are formed in the ejection holes and in the cooling fluid jets. The secondary flow fields include asymmetric kidney vortex systems with one dominating vortex on the back side of the jets. The numerical and experimental data show a good agreement concerning the vortex development. The phenomena on the suction side and the pressure side are principally the same. It can be found that the jets are barely touching the blade surface as the dominating vortex transports hot gas under the jets. Thus, the cooling efficiency is reduced.
Experimental and Numerical Conjugate Flow and Heat Transfer Investigation of the Influence of Density Ratio and Blowing Ratio on the Film-Cooling Efficiency of a First Stage Turbine Guide Vane
Authors: Bohn Dieter E. , Becker Volker J. , Rungen Agnes U. 
Published: December 2014

A modem nozzle guide vane with showerhead cooling is investigated. The showerhead design consists of four rows of ejection holes at the leading edge in the stagnation region and has been worked out on the basis of a former design with only two rows.
The experimental analysis is performed in a cold-air test turbine by means of LDV. In order to overcome the thermal limitations of the test rig, the heat transfer analysis is performed with CHT-Flow, a numerical method that has been developed at the Institute of Steam and Gas Turbines and that works in a conjugate manner. This means that no thermal boundary conditions such as heat transfer coefficients have to be described on the vane surface for thermal analysis.
The first part of the investigation deals with the aerodynamics. At first, air is used as a cooling fluid leading to a density ratio of Πρ = 1.2. Then, in order to take density effects into account in the experiments. CO2 is used as a cooling gas providing a density ratio Πρ = 1.8 representative for modern engine operating conditions. The results are compared to the simulations.
It is shown that the cooling gas does not penetrate the main flow as far under realistic density ratios. Thus, the aerodynamic losses are reduced and there is better attachment of the cooling film to the airfoil.
The second part analyses the heat transfer. It is shown that lowering the blowing ratio has different influences on the material temperature locally. On the suction side, the cooling gas film attachment is enhanced and the surface temperature is lowered. In contrast, the surface temperature rises slightly on the pressure side.
The Requirements for a Modern Marine Gas Turbine and the Development of the WR21
Authors: Butler Brian , Wright Nigel 
Published: December 2014

The maritime engine test facility at the Defence Evaluation and Research Agency (DERA) Pyestock in the United Kingdom has been involved with the testing of gas turbine engines for the Royal Navy since 1952. This testing has been aimed at proving that the already developed gas turbine can operate in the maritime environment, perform the expected duty cycles, and reach the required levels of availability, reliability, and maintainability as required. To this end, the vast amount of testing at DERA has been the endurance style where the engine is run over extended periods in arduous conditions to test the life of components and with only a minimum amount of data collection. This dramatically changed in 1994 with the beginning of the WR21 Intercooled Recuperated gas turbine (WR21 ICR) development program.
The paper describes the benefits of the WR21 ICR over a simple cycle gas turbine, the methodology behind the current development testing, and the evolution of the DERA Pyestock facility. In particular facility designs, instrumentation, data handling, and testing operations to meet the growing needs of the customer to develop this complex cycle gas turbine.
A Study of the Flow Field in a Model Rotor-Stator Disk Cavity
Authors: Roy R. P. , Devasenathipathy S. , Xu G. , Zhao Y. 
Published: December 2014

Experimental and computational studies of the turbulent flow field in a model gas turbine disk cavity have been carried out. The experiments were performed in a rig which features a rotor disk-stator disk configuration with stator vanes, rotor blades, and rim discouragers with axial overlap. Particle Image Velocimetry was used to map the flow field in the cavity at three positions along the axial gap between the disks for various mainstream and secondary air flow rates, and rotor speeds. Static pressure distribution in the cavity at the stator disk and the circumferential distribution of the same at the mainstream passage outer shroud were measured.
A recirculation region developed radially inboard in the disk cavity where a strong radial outflow was found close to the rotor disk and a weak radial inflow near the stator disk. This is the source region where the rotation of the core fluid is minimal, its radial extent increasing with the secondary air flow rate. Radially outboard, in the core region, the flow was rotation-dominated except when the secondary air flow rate was high.
The peak-to-peak amplitude of the circumferential pressure asymmetry in the mainstream flow path increased as the square of the main air flow rate, attained its maximum value at the stator vane exit, and decreased rapidly downstream. For the experiments performed, no circumferential pressure asymmetry could be found in the disk cavity, even near its rim. The rotating fluid in the core region of the cavity gave rise to an adverse radial pressure gradient, its magnitude increasing as the secondary air flow rate decreased. This feature can facilitate ingress of mainstream gas into the cavity.
Concurrently with the experiments, the flow field was simulated numerically using the commercial CFD code FLUENT/UNS. The agreement between the measurements and the computed results is generally good.
Influence of Rim Seal Geometry on Hot Gas Ingestion Into the Upstream Cavity of an Axial Turbine Stage
Authors: Bohn Dieter , Rudzinski Bernd , Sürken Norbert , Gärtner Wolfgang 
Published: December 2014

The ingestion of hot gas at the rim seal of a turbine has been investigated for a complete stage with nozzle guide vanes and rotor blades for two types of geometry: 1. the simple axial gap between a flat rotor disk and a flat stator disk, commonly used for industrial gas turbines and 2. an axial lip of the rim seal on the stator combined with a flat rotor disk, often found in aero engine applications. The clearance of the axial gap has been varied for the second type. The efficiency of the rim seal has been examined for different seal flow rates, rotational Reynolds numbers and Mach numbers in the main flow.
For the determination of the sealing effectiveness carbon dioxide gas concentration measurements have been carried out in the wheelspace. The distribution of the static pressure in the vicinity of the seal and inside the wheelspace has been measured by means of pressure taps at the stator disk.
It is shown that the external flow Mach number in the main flow has a significant effect on the sealing efficiency. As Mach number increases sealing efficiency goes down. The rotational Reynolds number has a distinct effect on the rim seal efficiency depending on the examined configuration. Even for high seal flow rates the ingestion of hot gas can not be fully avoided.
The experimental results were the motivation for a three-dimensional CFD approach neglecting the influence of the rotor blades. The results give further insight into aerodynamic features of the ingestion phenomenon.