bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aerodynamics Comparisons Between Two Typical Gas Turbine Combustion Swirlers
Authors: Kao Yi-Huan , Haseman Jacob B. , Tambe Samir B. , Jeng San-Mou 
Published: September 2014

In this work, a series of tests have been conducted to study the aerodynamics of two typical gas turbine combustion swirlers, using Laser Doppler Velocimetry (LDV). The first swirler used is a coaxial counter-rotating, radial-radial swirler, designated as the R-R swirler. The primary swirler accounts for 40% of the total effective area of the R-R swirler. The second swirler employed consists of an inner dual-axial swirler assembly with only around 20% of total swirler effective area and an outer coaxial radial swirler, and is designated as the A-R swirler. The aim of this work is to compare the aerodynamics performance of these two different types of swirlers under similar boundary conditions, such as confinement effect, downstream exhaust nozzle, and chamber length.
The R-R swirler has a very high radial dispersing rate, and for the unconfined case, the swirling jet remained attached to the dome plate resulting in a very weak, unbound CTRZ. The swirling jet for the A-R swirler exited at a relatively low expansion angle. For confined cases, the swirling jet attached to the walls of the confinement at a certain distance downstream of the exit plane for both swirlers.
When the exhaust nozzle was applied as a downstream boundary condition, a spinning vortex core with high turbulent intensity was detected along the swirler axis for the A-R swirler, whereas the only difference for the R-R swirler was a slight reduction in the expansion angle of the swirling jet. The proximity of the exhaust nozzle to the swirlers was changed by changing the chamber length. For the R-R swirler, the effect of chamber length was only detected in the near-field region. For the A-R swirler, a reduction in chamber length caused the spinning vortex core to become more intense. Additionally, an annular CTRZ was observed for the shorter chamber lengths.
CFD Investigation Into Oil/Air Behaviour Near a Shrouded Spiral Bevel Gear
Authors: Simmons Kathy , Guymer Dan , Turner Adam 
Published: September 2014

The capability to model an aeroengine internal gearbox in its entirety using CFD is currently hampered by the complexity of the two-phase, highly rotating system and the computational resource required. The University of Nottingham Technology Centre in Gas Turbine Transmission Systems has established modeling capability for an unmeshed, shrouded spiral bevel gear and has conducted a number of experimental investigations for such a gear operating within a cylindrical chamber [1, 2].
In this paper a CFD model is created of an external chamber geometry comparable to that on the experimental test rig using the commercial CFD code Fluent. Droplets are introduced into this chamber at a range of diameters and their trajectories tracked. Small droplets (0.1 μm to 1μm) are representative of mist within the chamber and essentially follow the highly rotating air flow. Droplets in the range 1 μm to 100 μm travel to the chamber walls but interact with the flow such that they may be in the core flow some time before impact. Larger droplets in the range 100 μm to 5000 μm are largely undeflected, travelling directly to the walls.
The Fluent thin film model is used to generate wall films from droplet impacts and the simulation shows how film is likely to be driven away from the gear by the air flows within the chamber forming a thicker film away from the gear axial location.
Vibration Reduction of a Centrifugal Compressor for Gas Transmission
Authors: Liu Zheji , Smith Raymond 
Published: September 2014

Centrifugal compressors used in gas transmission produce strong pressure pulsations, piping vibration, and noise. These are undesirable by-products of the compressor operation that is inherently an unsteady process. This is particularly true for compressors that use a vane diffuser, rather than a vaneless scroll type of diffuser. High vibration levels can potentially cause structural damage in the piping, particularly instrumentation connections, which can cause unnecessary machine down-time and production loss, and is a potential safety hazard.
This paper discusses a unique technique to reduce centrifugal compressor piping vibration. This technique reduces aeroacoustics excitation by mounting a duct resonator array inside a compressor diffuser. The effectiveness of this technique is demonstrated by a recent field application to address a noise and vibration concern of a compressor installed in a pipeline station. This compressor had run successfully for several years with a high (but not excessive) level of high frequency vibration in the unit piping. Recent changes in pipeline operating conditions resulted in a significant increase in vibration and associated problems including failure of thermowells and resistance temperature detectors (RTDs).
A preliminary measurement of gas pressure pulsations and piping vibration revealed a severe level of high frequency vibration that could lead to a fatigue failure of the unit piping, if operation continued under these conditions. Additional vibration data were measured from the compressor to characterize the noise and vibration and to establish the baseline for future comparison. The baseline vibration data are characterized with a dominant component at the blade passing frequency that makes the duct resonator array an ideal solution. Consequently, a resonator array was designed, manufactured, and installed to reduce the compressor piping vibration and noise.
A final test was conducted to verify the effectiveness of the resonator array. Comparing the data acquired before and after the resonator array shows that the dominant vibration level at the blade passing frequency was reduced by 93% on average. The compressor is now able to operate safely at the new pipeline conditions, and it runs much quieter over the full operating range.
An Investigation of Real Gas Effects in Supercritical CO2 Centrifugal Compressors
Authors: Baltadjiev N. , Lettieri C. , Spakovszky Z. 
Published: September 2014

This paper presents a comprehensive assessment of real gas effects on the performance and matching of centrifugal compressors operating in supercritical CO2. The analytical framework combines first principles based modeling with targeted numerical simulations to characterize the internal flow behavior of supercritical fluids with implications for radial turbomachinery design and analysis. Trends in gas dynamic behavior, not observed for ideal fluids, are investigated using influence coefficients for compressible channel flow derived for real gas. The variation in the properties of CO2 and the expansion through the vapor-pressure curve due to local flow acceleration are identified as possible mechanisms for performance and operability issues observed near the critical point.
The performance of a centrifugal compressor stage is assessed at different thermodynamic conditions relative to the critical point using CFD calculations. The results indicate a reduction of 9% in the choke margin of the stage compared to its performance at ideal gas conditions due to variations in real gas properties. Compressor stage matching is also impacted by real gas effects as the excursion in corrected mass flow per unit area from inlet to outlet increases by 5%. Investigation of the flow field near the impeller leading edge at high flow coefficients shows that local flow acceleration causes the thermodynamic conditions to reach the vapor-pressure curve. The significance of two-phase flow effects is determined through a non-dimensional parameter that relates the time required for liquid droplet formation to the residence time of the flow under saturation conditions. Applying this criterion to the candidate compressor stage shows that condensation is not a concern at the investigated operating conditions. In the immediate vicinity of the critical point however, this effect is expected to become more prominent. While the focus of this analysis is on supercritical CO2 compressors for carbon capture and sequestration, the methodology is directly applicable to other non-conventional fluids and applications.
Large Eddy Simulation of a Thermoacoustic Instability Within a Swirl-Stabilized Burner Using Impedance Boundary Conditions
Authors: Lourier Jean-Michel , Noll Berthold , Aigner Manfred 
Published: September 2014

A thermoacoustic instability observed within a lean swirl-stabilized burner is analyzed by means of numerical calculations. As extension to previously reported numerical data for the considered test case, the numerical domain is extended to include the fuel plenum and the acoustic outlet impedance is modeled by time domain impedance boundary conditions.
The predicted thermoacoustic frequency is in excellent agreement with experimental findings. Furthermore, the thermoacoustic feedback loop is discussed by means of phase resolved data which show that a variation of the equivalence ratio within the swirler is the driving mechanism of the instability. Finally, the Rayleigh criterion is shown to be satisfied within the combustion chamber. Hence, a closed thermoacoustic feedback loop is observed.
Leakage Performance and Rotordynamic Characteristics of Bump Floating Ring Seals for Turbopump
Authors: Lee Yong-Bok , Kim Kyoung-Wook , Ryu Sol-Ji , Chung Jin Taek 
Published: September 2014

Floating ring seal with bump foil (BFRS) was newly proposed and tested. BFRS which has a thickness of bump (0.076, 0.1 and 0.12 mm) are separately tested for pressure-drops of 3.0, 5.0 and 7.0 MPa and rotor-speed up to 24,800 rpm. The measured data included leakage performance, attitude angle, lock-up eccentric ratio, and rotordynamic coefficients such as stiffness, damping and equivalent whirl frequency ratio to decide the whirling stability of seal were compared with floating ring seal.
When the thickness of bump floating ring seals is increasing, leakage flow rate somewhat increases. Also, the lock-up eccentric ratio of the bump floating ring seal with large thickness is lower than that of the floating ring seal or small thickness of bump foil. The attitude angle increases linearly with the operating speeds in both cases. The direct damping coefficients increase significantly with the increments in bump-foil thickness and hydrostatic pressure-drop, but diminish with the rising rotor-speed. Especially, Coulomb friction damping force between the bump foil and housing surface contributes to the enhancement of direct damping coefficient value. Whirl frequency ratio of the floating ring seal without bump shows somewhat small in low speed ranges. When bump foil thickness is 0.074mm or 0.1mm, WFR is insensitive in rotating speed and pressure. But BFRS (0.12mm) shows up more stable tendency according to decreasing whirl frequency ratio in high speed ranges. The design parameters determined from these test results will be used to enhance the stability in high pressure and high speed turbomachinery seals.
Development of the Electric Fuel System for the More Electric Engine
Authors: Morioka Noriko , Oyori Hitoshi , Gonda Yukinori , Takamiya Kenji , Yamamoto Yasuhiko 
Published: September 2014

This paper describes the experimental rig test result of the electric motor-driven fuel pump system for the MEE (More Electric Engine). The MEE is an aircraft engine system concept, which replaces conventional mechanical/hydraulic driven components with electric motor-driven components. Various MEE approaches have been studied since the early 2000s and one of its key concepts is an electric motor-driven fuel pump [1–4]. The authors commenced a feasibility study of the electric motor-driven gear pump system for what was assumed to be a small-sized turbofan engine. The concept study and system design were conducted, whereupon technical issues for the electric fuel pump system, which both supplies and meters fuel via the motor speed control, were clarified [5, 6]. Since one of the key issues is fuel-metering accuracy, the electric fuel system, including a flow feedback closed-loop control, was designed to ensure accurate fuel-flow metering for aircraft engine applications.
To verify the rig system, an experimental model of the electric fuel pump system is assumed for a small-sized turbofan engine. The hardware of the motor-driven fuel pump and flow measurement mechanism, including an FPV (Fuel-Pressurizing Valve) and orifice, were designed, manufactured and fabricated and a differential pressure sensor for flow feedback was selected. Other equipment was also prepared, including a motor controller, power source and measurement devices, and the entire rig set-up was constructed.
A bench test using the rig test set-up was conducted to verify the fuel-metering accuracy, response and system stability. Data, including the static performance and frequency response, were obtained for the electric motor, motor-driven fuel pump and entire fuel system respectively. The rig test results indicate the feasibility of the system, which will provide an accurate engine fuel flow (Wf) measurement and frequency response required for actual engine operation, via an electric motor speed control and fuel-flow feedback system, as proposed in the MEE electric fuel system.
Numerical Conjugate Heat Transfer Study of a Cooled Compressor Rear Cone
Authors: Bleier Fabian , Hufnagel Max , Pychynski Tim , Bauer Hans-Jörg , Eichler Christian 
Published: September 2014

The paper presents the setup of a conjugate heat transfer study of an annular conical gap, its validation and a parameter study. The main goal of the work is to identify effects of gap width and swirl ratio on the local and global heat transfer in the annular conical gap. The validation of the numerical model is done by a comparison against experimental data from literature. It is shown that the non-axisymmetric flow in the gap can be well reproduced by a three-dimensional axisymmetric model. To identify influences of geometric and operational parameters on the cooling efficiency, a RANS parameter study of the cooling concept is performed. The parameter study includes variations of the gap width and the pre-swirl of the inlet air.
The results are used to evaluate the quality of the cooling concept and to identify the effect of geometry on frictional effects and on heat transfer coefficients. In this respect it is important to separate frictional heating and convective heat transfer effects.
Numerical Investigations on the Conceptual Design of a Ducted Contra-Rotating Fan
Authors: Huo Chao , Gonzalez Diez Nestor , Rao Arvind Gangoli 
Published: September 2014

The Advisory Council for Aeronautics Research in Europe (ACARE) has set an ambitious array of objectives to be accomplished by 2050. It is often claimed that complying with those targets will not require evolution but, rather, revolution. If the growth in aviation has to be sustained in the future then we must come up with radical aircraft and engine configurations which can meet the demands of future aviation.
The contra-rotating fan is one such system which can play an important role in the future engine configurations, such as the hybrid engine configuration that is being investigated in the EU cofounded AHEAD project.
In order to design a CRF system, a 1-D code has been developed based on the inverse Blade Element Method (BEM) to design a contra rotating fan. The CRF design obtained from this methodology is then analyzed with a full 3D RANS simulation.
The numerical analysis revealed that the performance of the first rotor satisfies with the given design requirements in terms of both pressure ratio and isentropic efficiency, thus proving the efficacy of using the 1-D code for designing the CRF. However, the performance of the rear rotor does not reach the design demands. It was observed that there is a strong flow separation around the root and a strong normal shock in the blade passage near the tip. It was found that there is a great difference between the blade metal inlet angles and the relative flow inlet angles near the root of the rear rotor. One of the main reasons for this is the calculation of the axial velocity depending on the vortex design and the resolution of the radial equilibrium. Based on the CFD simulations, the design code could be further modified to improve the design of CRF.
Development of a Novel Axial Compressor Generation for Industrial Applications: Part 1 — Compressor Design and Performance
Authors: Ziegler Kai , Eisenberg Bernhard , Hörmeyer Klaus , Emmrich Roland , Ressing Henning 
Published: September 2014

An industrial axial compressor has to meet a wide range of operation requirements and therefore must run within the whole compressor map without restrictions at an overall high level of efficiency. Additionally a robust design is required allowing a continuous operation of up to five years under industrial boundary conditions without inspection. These requirements led the industrial turbomachinery market to be generally conservative and sensitive to every single change through modern compressor development. The consequence for industrial compressor designs are, that these have made only moderate development steps during the last 50 years.
This paper deals with a novel hybrid axial flow compressor, which combines the advantages of an conventional industrial compressor, such as good operating range and efficiency, with the advantages of gas turbine compressors, mainly the higher power density resulting in a higher stage pressure ratio. Furthermore, the surge robustness of the novel compressor blading has been strongly improved. Starting from scratch, the development began with comprehensive matrix studies in all areas of the design, taking into account aerodynamics, mechanics, rotor dynamics and power density in order to ascertain the overall optimum for this new hybrid generation. State of the art CFD analysis has been intensively used to optimize the compressor blading as well as the flow behavior of inlet and exit for the specified requirements and different compressor control mechanisms.
The novel hybrid compressor is designed for a volume flow of 930 000 m3/h and allows a scaling from 100 000 up to 1 500 000 m3/h of air. To verify the design, a rig — downscaled by the factor of 3 — was tested. The rig was intensively instrumented with thermocouples and pressure probes, a torquemeter, strain gauges, tip-timing probes, and transient pressure transducers. Besides the measurement of blading performance, inlet and exit flange-to-flange instrumentation has been used to collect performance data under a variety of industrial operating conditions. The compressor behavior will be presented with a focus on aerodynamic aspects. The analytical and experimental data will be discussed in detail.
Towards a Highly Efficient Small Scale Turboshaft Engine: Part II — Aero-Mechanical Turbine Design and Optimization
Authors: Siller U. , Kröger G. , Moser T. , Hediger S. 
Published: September 2014

Aero-mechanical design of the turbine section of a small scale turboshaft engine is presented in this paper. A single stage high-pressure turbine (HPT) and the power turbine stage (PT), have been designed by means of automated optimization. This study demonstrates how multi-disciplinary optimization can be used effectively in today’s industrial development cycles with respect to timeframe and computational resources. Both, the aerodynamic performance and the mechanical blade behavior were subject to the optimization in a very high dimensional design space expressed by well above 100 free design parameters for the annular duct and the bladings of two axial stages. In the first part, this paper describes the design task and constraints in order to meet the requested thermodynamic cycle performance and fabricational requirements. In the second part, the optimization strategy is explained with focus on geometry parameterization, simulation setups for flow and structural analysis and acceleration techniques for the optimization itself.
Finally, a very promising resulting design is reviewed in terms of a detailed aerodynamic and mechanical assessment and regarding to the overall engine concept. This work contributes to the development of a highly efficient, light-weight propulsion system powering, beside a wide range of other possible applications, for example small aerial systems such as helicopter drones.
The engine prototype is expected to be tested the first time in 2014.
Operation of a Burner Rig for Thermal Gradient Cycling of Thermal Barrier Coatings
Authors: Feist J. P. , Sollazzo P. Y. , Pilgrim C. , Nicholls J. R. 
Published: September 2014

Thermal barrier coatings (TBC), in combination with sophisticated cooling systems are crucial for the operation of highly efficient gas turbines. New generations of coatings will need to show increased cycling capability as a future energy mix will contain a high proportion of renewable energy which will be subject to rapid changes in supply. This will require gas turbines to be on stand-by to fill shortages in power supply with short notice. Furthermore, higher operating temperatures are sought to improve the efficiency of the engine. It is, therefore, an aim of the industry to find a coating composition or structure which will enable the operation at temperatures greater than 1250°C and with high cycling capability.
Test methods are required to meet these new operating conditions to validate new coatings. The maximum temperature limit of commonly used isothermal or cyclic oxidation tests is usually the temperature at which the substrate will start to significantly oxidise. However, there is the technical need to test the ceramic top layer at elevated surface temperatures up to 1500°C while keeping the substrate ‘cool’. Such capability would allow the effects of ceramic sintering, and deposit induced damage to be assessed at the TBC surface. This only can be performed on a complete coating system, when a thermal gradient is established throughout the coating.
This paper reviews a burner test facility, designed and built by Sensor Coating Systems Ltd. (SCS), which combines severe and frequent cycling with the exposure of the coating to high surface temperatures and active cooling of the substrate. Further, this test can include thermal shock by active cooling of the surface at the end of each cycle. The paper will consider different operating conditions and will review experiences in building and operating the rig, including results from thermal barrier coating tests on electron beam physical vapour deposition (EBPVD) and atmospheric plasma spray (APS) samples. Further, the rig is capable of testing optical techniques such as pyrometry and thermographic phosphor thermometry for measuring surface temperature in controlled laboratory conditions and example of this will be presented. The paper also will reflect on the ISO 13123:201 standard for this type of test.