bluuebunny/crossref_metadata_2025_split huggingface dataset:
Telemetric Measurement of Heat Transfer Coefficients in Gaseous Flow: First Test of a Recent Sensor Concept in a Rotating Application
Authors: Heinschke Benjamin , Uffrecht Wieland , Günther André , Odenbach Stefan , Caspary Volker 
Published: September 2014

Heat transfer coefficients are very important for the design of the various flow paths found in turbomachinery. An accurate measurement of heat transfer is difficult for circumstances of gaseous flow in combination with good thermal conductivity of the boundaries along the flow path. The majority of the measurement methods applied frequently have at least one of the following problems: (1) the measurement system as for instance a heat flux sensor is a thermal barrier in the object of interest, and (2) the sensor introduces for measurement reasons a lot of heat into the object of interest. In both cases the main error results from the modification of the system, which is critical for the investigation of any kind of flow influenced by buoyancy. Furthermore, insufficient fluid reference temperature and/or heat flux with changing sign corrupts any attempt to calculate reliable heat transfer coefficients.
The measurement of heat transfer coefficients becomes even more complicated if the flow path of interest rotates at some thousand rpm as for instance in gas turbines or any other fast rotating machine with fluid flow. This contribution presents a new test rig and an experimental investigation of a setup for the direct telemetric measurement of local heat transfer coefficients in gaseous flow with metallic boundaries. The test rig has a complex instrumentation and the measurements are transferred from the rotating to the stationary frame via newly in house developed telemetry system. The measurements presented are based on a recent measurement/sensor concept tested for the first time in the rotating frame. The measurement setup features miniaturized sensor dimensions and low energy consumption. Therefore, the sensor concept is very well suited for use with telemetry system as necessary for many turbomachinery research applications.
Furthermore, measurements of the radial distribution of the heat transfer coefficient of a rotating free disc are presented. Additionally a comparison with correlations found in literature as well as a discussion of the results is included.
Development of a Novel Axial Compressor Generation for Industrial Applications: Part 2 — Blade Mechanics
Authors: Anding Dirk , Ressing Henning , Hörmeyer Klaus , Pisch Roland , Ziegler Kai 
Published: September 2014

Blade vibrations resulting in alternating stresses are often the critical factor in determining blade life. Indeed, many of the failures experienced by turbomachinery blades occur due to high-cycle fatigue caused by blade vibrations. These vibrations can arise either through self-excited oscillations known as flutter or through aerodynamic forcing of the blades from factors such as periodic wakes from up and/or downstream vanes or unsteady flow phenomena such as compressor surge.
The current paper deals with the design and the analytical and experimental verification of the axial blading for a new generation of industrial compressors, a hybrid axial compressor that combines the advantages of conventional industrial compressors — broad operating range and high efficiency — with the advantages of gas turbine compressors — high power-density and high stage pressure ratios. Additionally, the surge robustness of this novel compressor blading has been greatly improved. During the development phase extensive efforts were made to ensure safe operation for future service life. This was achieved by designing blades that will not flutter, do not have high resonance amplitudes throughout their entire operating range and are extremely robust against surge.
This strongly increased robustness of the new compressor blading was achieved by the implementation of a “wide-chord” blade design in all rotor blade rows in combination with a proper tuning of resonance frequencies throughout the entire operating range. For the verification of the new blading well-established methods accepted by industry were used such as CFD and FEA. Furthermore, coupling of the two into a method referred to as Fluid Structure Interaction (FSI) was used to more closely investigate the interaction of flow and structural dynamics phenomena. These analytical techniques have been used in conjunction with extensive testing of a scaled test compressor, which was operated at conditions of dynamic similitude (matching of scaled blade vibration frequencies, flow conditions, and Mach number) with full-scale operational conditions. Strain gauges placed on the blades and a state of the art technique known as “tip timing” were used to verify blade vibrations over a wide range of combinations of guide vane positions and rotational speeds.
No propensity was found of any of the blades to develop high vibration amplitudes at any of the operating conditions investigated in the rig tests. The comparison of non-linear forced response analyses and the rig test results from strain gauges and tip timing showed close agreement, verifying the analysis techniques used.
In conclusion it can be stated that the blade design exhibits a very high level of safety against vibrations within the entire operating range and during surge.
Unsteady RANS Analysis of Particles Deposition in the Coolant Channel of a Gas Turbine Blade Using a Non-Linear Model
Authors: Borello Domenico , Capobianchi Paolo , De Petris Marco , Rispoli Franco , Venturini Paolo 
Published: September 2014

The two-phase flow in a geometry representing the final portion of the internal cooling channels of a gas turbine blade is here presented and discussed. In the configuration under scrutiny, the coolant flows inside the duct in radial direction and it leaves the blade through the trailing edge after a 90 deg turning.
An unsteady Reynolds Averaged Navier-Stokes (URANS) simulation of the flow inside such channel was carried out. An original non-linear version of the well-established ζ-f elliptic relaxation model was developed and applied here.
The new model was implemented in the well-validated T-FlowS code currently developed by the authors’ group at Sapienza Università di Roma.
The predictions demonstrated a good accuracy of the non-linear URANS model, clearly improving the results of the baseline linear ζ-f model and of the Launder Sharma k-ε model used as reference.
The obtained unsteady flow field was adopted to track a large number of solid particles released from several selected sections at the inlet and representing the powders usually dispersed (sand, volcanic ashes) in the air spilled from the compressor and used as cooling fluid.
The well-validated particle-tracking algorithm here adopted for determining the trajectories demonstrated to be very sensitive to the flow unsteadiness.
Finally, the fouling of the solid surfaces was estimated by adopting a model based on the coefficient of restitution approach.
Transient Surge Dynamics: A Shock Tube Theory and Experimental Comparison
Authors: Huang Paul Xiubao , Yin JianAn 
Published: September 2014

High-speed high-pressure ratio compressor surge is a transient breakdown in compression accompanied by an abrupt momentary reversal of gas flow. It commonly exists in dynamic type turbo compressors, particularly in the axial compressor of modern aero-engines. By Newton’s Laws of Motion, a force is needed to change the state of any motion. So what is the force that can cause such a dramatic motion as surge? What exactly triggers it, and how do we quantify the transient surge phenomenon? This paper attempts to answer these questions and discuss the transient dynamics of surge at its initial stage.
It has generally been accepted that surge is precipitated by the onset of a rotating spike or stall, not only for low speed but for high-speed compressors too. The state of dynamic surge modeling today is best exemplified by the “Greitzer-Moore” model. However, it fails to incorporate the key elements of the transient nature of a surge inception: the extremely short time duration on millisecond scale and the shock wave presence observed experimentally.
An indirect approach is taken in this paper to address the transient dynamics of stall and surge by using an analogy to the shock tube. The link is established based on observations that instant zero net through flow inside stalled cascade cell triggers stall/surge. The results from the analogy reveal that surge initiation simultaneously generates a pair of non-linear compression and expansion waves (CW & EW) and induced reverse fluid flow (IRFF). The dynamic forces for instant flow reversal are the pushing force of upstream propagating CW and the pulling force from downstream travelling EW. Surge Rules are deduced and then compared with experimental findings by previous researchers with good agreements. Moreover, the strength of the transient post-surge components, CW, EW and IRFF, can be estimated analytically or numerically by the shock tube theory from known pre-surge conditions and routes to surge.
Study of Unsteady Heat Transfer as a Key Parameter to Characterize Limit Cycle of High Amplitude Pressure Oscillations
Authors: Shahi Mina , Kok Jim B. W. , Roman Casado J. C. , Pozarlik Artur K. 
Published: September 2014

The objective of the studies presented in this paper is the numerical prediction of unsteady heat flux and pressure fluctuations during the unstable regime of a combustor. The studied laboratory-scale lean partially premixed combustor was built in the LIMOUSINE project, to explore the mechanisms driving thermo-acoustic instabilities in conditions representative of gas turbine combustors.
Due to the thermal interaction between hot gases and the colder liner wall, and also the correlation between gas temperature, density and speed of sound, prediction of the transient heat transfer rate is of high importance. In this paper analysis of transient heat transfer is conducted by coupling of fluid flow and solid body (liner) in one computational domain and thereby taking into account the thermal convection with the environment around the combustor and also the heat conduction transients within the liner. Conjugate heat transfer modeling can give access to the transient temperature distribution in the structure of the combustor which is important for the dynamic heat storage. Also this can be used to estimate the thermal stresses and creep strain as required to evaluate the lifetime assessment of the combustor. In this work the commercial CFD code ANSYS CFX is used to solve the problem, in which fluid and solid regions are solved simultaneously with a finite volume approach. In the fluid region, three dimensional compressible Reynolds Averaged Navier-Stokes equations are solved, while for the solid region only the enthalpy conservation equation is solved. To remove any interpolation errors, in all cases the skin (interface) mesh cells for both the fluid and solid are similar in resolution on either side of the interface. By comparing heat release and pressure data available from the measurements it follows that this simulation can give more accurate prediction of the amplitudes of thermoacoustic instabilities as compared to the solution with imposed thermal boundary conditions (such as isothermal). In the latter case the time history of heat accumulation in the solid is predicted incorrectly. Because the spatial scales of the solid temperature profiles are different in case of steady state or transient oscillatory heat transfer, care has to be taken in the meshing in these two situations. When meshing for a transient oscillatory heat transfer case, the solid mesh resolution needs to be adapted to the thermal penetration depth of the surface temperature oscillations. Hence for the transient heat transfer in limit cycle combustion oscillations, the meshing strategy and size of the grid in the solid part of the domain will play a very important role in determining the magnitude for the pressure fluctuations.
Experiments on an Axial Fan Stage: Time Resolved Analysis of Rotating Instability Modes
Authors: Pardowitz Benjamin , Tapken Ulf , Neuhaus Lars , Enghardt Lars 
Published: September 2014

Rotating Instability (RI) occurs at off-design conditions in axial compressors, predominantly in rotor configurations with large tip clearances. Characteristic spectral signatures with side-by-side peaks below the blade passing frequency are typically referred to RI located in the clearance region next to the leading edge (LE). Each peak can be assigned to a dominant circumferential mode. RI is the source of the clearance noise and an indicator for critical operating conditions. Earlier studies at an annular cascade pointed out that RI modes of different circumferential orders occur stochastically distributed in time and independently from each other, which is contradictory to existing explanations of the RI. Purpose of the present study is to verify the generality with regard to axial rotor configurations.
Experiments were conducted on a laboratory axial fan stage mainly using unsteady pressure measurements in a sensor ring near the rotor LE. A mode decomposition based on cross spectral matrices was used to analyze the spectral and modal RI patterns upstream of the rotor. Additionally, a time-resolved analysis based on a spatial Discrete-Fourier-Transform was applied to clarify the temporal characteristics of the RI modes and their potential interrelations. The results and a comparison with the previous findings on the annular cascade corroborate a new hypothesis about the basic RI mechanism. This hypothesis implies that instability waves of different wavelengths are generated stochastically in a shear layer resulting from a backflow in the tip clearance region.
Deformation Modeling and Lifetime Prediction of Ni-Base Gas Turbine Blade Alloys Under TMF-Conditions
Authors: Grützner Stefan , Fedelich Bernard , Rehmer Birgit , Mosquera Maria 
Published: September 2014

Under cyclic thermomechanical loading conditions, various effects such as strain accumulation, creep damage, ageing, fatigue etc. may occur in the material of a gas turbine blade. Depending on the loading conditions, all these effects contribute to reduce the lifetime of the component.
Subject of the present work is the development of a lifetime model able to discriminate between the different damage mechanisms, as well as the development of a material model to describe the mentioned effects and thus providing the input data for lifetime prediction.
CFD Simulation of Incompressible Turbomachinery — A Comparison of Results From ANSYS Fluent and OpenFOAM
Authors: Bothe Franziska , Friebe Christian , Heinrich Martin , Schwarze Rüdiger 
Published: September 2014

A numerical investigation of incompressible turbomachinery and the comparison of two CFD packages are presented within this paper. A ducted single rotor fan is simulated with OpenFOAM and ANSYS FLUENT by applying methods as comparable as possible. The characteristic maps and flow fields are analyzed and the results from the CFD codes are compared to examine differences regarding accuracy and efficiency. Additionally the influence of the turbulence model is determined. It is found that the CFD programs show a good agreement especially at the machines design point.
The information about the flow field of this fan is used for the modelling of a high-performance and energy-efficient ducted contra-rotating fan (CRF). Comparing the CRF simulation results to those of the single rotor fan, a doubling of the total pressure rise and a significant reduction of the swirl in the wake flow can be noticed.
Development and Experimental Investigation of a Tubular Combustor for Pyrolysis Oil Burning
Authors: Beran Martin , Axelsson Lars-Uno 
Published: September 2014

The growing demand for more economical and environmentally friendly power generation forces the industry to search for fuels that can replace the conventional fossil fuels. This has led to significant developments in the production of alternative fuels during the last years, which have made them a reliable and relatively efficient source of energy. One example of these alternative fuels is the pyrolysis oil. However, higher viscosity, lower heat content, limited chemical stability and its ability to create sediment make pyrolysis oil challenging for gas turbines. The OPRA OP16 gas turbine is an all radial single-shaft gas turbine rated at 1.9 MW. The all radial design, together with the lack of intricate cooling geometries in the hot section, makes this gas turbine suitable for operation on these fuels.
This paper presents an experimental investigation of pyrolysis oil combustion in a tubular combustor developed especially for low-calorific fuels. The experiments have been performed in an atmospheric combustion test rig and the results have been compared to the results obtained from ethanol and diesel combustion. It was found that it was possible to burn pure pyrolysis oil in the load range between 70 to 100% with a combustion efficiency exceeding 99% and without creation of sediments on the combustor inner wall.
It was found that the NOx emissions were similar for pyrolysis oil and diesel, whereas the CO emissions were twice as high for pyrolysis oil. A comparison between the air blast nozzle and the pressure nozzle was performed. The air blast nozzle was found to be more suitable due to its better performance over a wider operating range and that it is more resistant to erosion and abrasion. It was found that the maximum allowed droplet size of the pyrolysis oil spray should be about 50–70% of the droplet size for diesel fuel.
Research and Educational Opportunities in Hardware-in-the-Loop Simulation of Advanced Power Systems: An International Perspective
Authors: Pezzini Paolo , Ferrari Mario L. , Tucker David , Traverso Alberto 
Published: September 2014

Hardware-in-the-loop simulation (HiLS) is a specific technique designed in the experimental environment for studying the coupling between different technologies, where simulated and hardware components interact to each other. Two different HiLS facilities used for educational and research purposes are examined in the paper: the Hybrid Performance (Hyper) project facility at the U.S. Department of Energy, National Energy Technology Laboratory (NETL), and the Hybrid system emulator at the Thermochemical Power Group (TPG) facility, run by the University of Genoa in Italy. Since one facility is at a national laboratory and the other one in a university environment, both facilities dedicate considerable resources to the education of students with a different perspective: industrial and experimental approach.
A description of the two configurations, the unique and overlapping attributes of each facility and the experimental results are reported and discussed to show different possibilities for students and researchers. Undergraduates, Postgraduates and Ph.D. students have the opportunity to learn innovative configuration of energy power systems, innovative control strategies applied to hybrid configurations, how to design real hardware components, and how to implementation real-time simulation models. The strong impact of these two laboratories is to show to students the applicability about their knowledge studied during lectures.
From Design Aspects Through to Testing of the MAN Diesel and Turbo Subsea Motor-Compressor for the Åsgard Subsea Project
Authors: Büche Dirk , Aho Tuomo , Dettwyler Markus 
Published: September 2014

This paper outlines pioneering work in the field of subsea compressor technology. The guiding design principles for the subsea motor-compressor of the authors’ company were operational safety, robustness, reliability, and remote operability. An early demonstrator was realized and tested in collaboration with the end-user upfront and consecutively improved gradually where indicated. This turned out to be beneficial in the phase of project execution since the early knowledge of application specific requirements resulted in an already elaborated overall design basis.
The presented design also draws on extensive top side experience from sealed motor-compressors, where a portion of the process gas is taken directly from an intermediate stage of the compressor and fed back to the suction line after passing through, and thus cooling, the motor and the active magnetic bearings. This minimizes the number of interfaces and required sub-systems.
Various simulations were performed to account for differences between subsea and topside environments. The focus of the work presented in this paper is on the effect of the high heat transfer resulting in an altered overall temperature situation.
At the time of writing, the first units of the discussed subsea motor-compressor have successfully passed Factory Acceptance Testing (FAT) under atmospheric conditions. At the moment, they are being prepared for extended submerged testing with production gas at a test facility of the end-user.
A Theoretical and Experimental Analysis of the Sealing Capability of a Membrane Seal
Authors: Tibos Stacie , Aujla Randhir , Pyzik Przemyslaw , Lewis Martin , Justl Sascha 
Published: September 2014

Improvements in turbine performance are increasingly being driven by the need to control leakage both in the main gas path as well as secondary air flow systems. Membrane seals have long been established as a method of sealing in some of the harshest of environments found in gas turbines. The membrane seal has a wide usage in gas turbines for stationary component interface sealing. The geometry is of plate construction with bulbous ends, the seals are assembled vertically and are retained by the component grooves. The grooves allow relative sliding and rotation against their surfaces a necessary feature, since during operation the seal needs to withstand relative movements due to thermal growth, vibratory forces, excitation and assembly loads. However, more accurate leakage estimates are required. Thus, in order to evaluate the complete performance characteristics of the seal for a wide range of working conditions, a theoretical and experimental campaign was undertaken.
The membrane seal performance curves were created based on a series of tests performed in a specially designed rig. The rig utilised an actuation system that allowed for the precise adjustment of the seal’s relative position in two directions while performing the tests at a given working condition. It was noted that not only the movement and deformation of the membrane but also, assembly clearances and surface condition of the components have an impact on the seal’s performance. To assist in the understanding of the influence of the changing parameters on the performance of the seal an FEA study was undertaken employing known data to aid the understanding and improve the knowledge of how the seal behaves under specific engine conditions. The evaluation gives confidence in the experimental test results.