bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas Turbine Operation Offshore: Increased Operating Interval and Higher Engine Performance Through Optimized Intake Air Filter System
Authors: Madsen Stian , Bakken Lars E. 
Published: September 2016

Optimized operation of gas turbines is discussed for six LM2500PE engines at a Statoil North Sea offshore field. Three engines are generator drivers whilst three engines are compressor drivers. Two of the compressor drive engines are running at peak load (T5.4 control), hence the production rate is limited by the available power from these engines. All of the six engines discussed run continuously without redundancy, gas turbine uptime is therefore critical for the field’s production and economy. The performance and operational experience with upgraded inlet air filter systems and online water wash at high water-to-air ratio, as well as successful operation at longer intervals and higher average engine performance are described.
For North Sea operation, a key property of the filter system is the ability to handle high humidity and high salt-content through the harsh environment in these waters. The upgraded filter systems analyzed in this paper is a 2-stage system (vane separator stage upstream of the high-efficiency-filter stage), which is a simplified design versus the old traditional 3-stage systems (louvre upstream and vane separator downstream of the filter stage). These 2-stage systems rely on an efficient upstream vane separator to remove the vast majority of water from the airflow before it reaches the high-efficiency filters. The high-efficiency filters are especially designed to withstand moisture. Deposit analysis from the downstream side of the filters has been performed. Extensive testing of both new and used filter elements, of different filter grade and operated at different intervals, has been performed on a filter test rig facility onshore.
All six engines have historically been operated with 4-month intervals between maintenance stops. Online wash is performed daily between the maintenance stops at full load (i.e. normal operating load for the subject engine). As a result of successful development and pilot testing of new filters and optimized filter change intervals, as well as successful online water wash, the engine operating intervals are now extended to 6 months with very low deterioration rate.
Understanding the gas turbine performance deterioration is of vital importance. Trending of its deviation from the engine baseline facilitates load-independent monitoring of the gas turbine’s condition. Instrument resolution and repeatability are key factors in order to get reasonable results from the performance analysis. Improvement of the package instrumentation has been implemented on three of the analyzed engines, for better performance monitoring. As a result of these analyses, a set of monitoring parameters is suggested for effective diagnostics of compressor degradation. Avenues for further research and development are proposed in order to further increase the understanding of the deterioration mechanisms and the gas turbine performance and response.
Perspectives and Experience With Wet Gas Compression
Authors: Musgrove Grant O. , Poerner Melissa A. , Beck Griffin , Kurz Rainer , Bourn Gary 
Published: September 2016

In oil and gas applications, gas-liquid mixtures of a process fluid are commonplace and the phases of the mixtures are separated upstream of pump or compressor machinery. Considering compressors, the separation of phases is important because the liquid causes the compressor to operate significantly different than with dry to affect the range, performance, and durability of the machine. Even with separation equipment, liquid can be ingested in a compressor by liquid carryover from the separator or condensation of the process gas. Additionally, there is no single definition of what is considered a wet gas.
In this paper, the definition of wet gas from multiple applications is reviewed and a general definition for wet gas is formulated. The effects of wet gas on reciprocating, screw-type, and centrifugal compressors are reviewed to provide insight into how their operation is affected. The limited information for screw compressors is supplemented with multiphase effects in screw pumps.
An Investigation of Turbine Film Cooling Effectiveness With Shaped Holes and Internal Cross-Flow With Varying Operational Parameters
Authors: Wilkes Ellen , Anderson Joshua , McClintic John , Bogard David 
Published: September 2016

This study focuses on specifics of gas turbine film cooling. Laboratory film cooling tests are important for industry because actual engine conditions are too hot, too small, and too fast to take accurate and high resolution measurements. Experiments are typically conducted using a plenum to feed coolant through round or shaped film cooling holes. Less common are experiments using cross-flow fed coolant, a method that flows coolant perpendicular to the mainstream flow and better represents engine designs. There are a few studies that have explored shaped holes in cross-flow, but none have looked at the effect cross-flow channel parameters other than Mach number.
Here, the effectiveness of film cooling is quantified by measuring adiabatic effectiveness on a flat plate with a single row of shaped film cooling holes in cross-flow. A preliminary examination of the effect of cross-flow versus plenum fed coolant on the adiabatic effectiveness of the axial 7-7-7 shaped hole, a laidback fan-shaped hole with a 30 degree injection angle, is first conducted. Subsequently, the effects of two internal coolant parameters on film cooling effectiveness are presented: Reynold’s number inside the cross-flow channel, and velocity ratio (defined as the ratio of cross-flow channel average velocity to mainstream velocity). By measuring the effect of these parameters, a chain of relative importance can be generated and applied to future experimentation. Parameters that heavily influence film cooling effectiveness can be studied further and optimized for turbine film cooling design.
A Water Lubricated Hybrid Thrust Bearing: Measurements and Predictions of Static Load Performance
Authors: San Andrés Luis , Phillips Stephen , Childs Dara 
Published: September 2016

Process fluid lubricated thrust bearings (TBs) in a turbomachine control rotor placement due to axial loads arising from pressure fields on the front shroud and back surface of impellers. To date, prediction of aerodynamic induced thrust loads is still largely empirical. Thus needs persist to design and operate proven thrust bearings and to validate predictions of performance derived from often too restrictive computational tools. This paper describes a test rig for measurement of the load performance of water lubricated hydrostatic/hydrodynamic thrust bearings operating under conditions typical of cryogenic turbo pumps.
The test rig comprises of a rigid rotor composed of a thick shaft and two end collars. A pair of flexure-pivot hydrostatic journal bearings (38 mm in diameter) support the rotor and quill shaft connected to a drive motor. The test rig hosts two thrust bearings (8 pockets with inner diameter equal to 41 mm and outer diameter equal to 76 mm); one is a test bearing and the other is a slave bearing, both facing the outer side of the thrust collars on the rotor. The slave TB is affixed rigidly to a bearing support. A load system delivers an axial load to the test TB through a non-rotating shaft floating on two aerostatic radial bearings. The test TB displaces to impose a load on the rotor thrust collar and the slave TB reacts to the applied axial load.
The paper presents measurements of the TB operating axial clearance, flow rate and pocket pressure for conditions of increasing static load (max. 3,600 N) and shaft speed to 17.5 krpm (tip speed 69.8 m/s) and for an increasing water supply pressure into the thrust bearings, max. 17.2 bar (250 psig). Predictions from a bulk flow model that accounts for both fluid inertia and turbulence flow effects agree well with recorded bearing flow rates (supply and exiting thru the inner diameter), pocket pressure and ensuing film clearance due to the imposed external load. The measurements and predictions show a film clearance decreasing exponentially as the applied load increases. The bearing flow rate also decreases, and at the highest rotor speed and lowest supply pressure, the bearing is starved of lubricant on its inner diameter side, as predicted. The measured bearing flow rate and pocket pressure aid to the empirical estimation of the orifice discharge coefficient for use in the predictive tool. The test data and validation of a predictive tool give confidence to the integration of fluid film thrust bearings in cryogenic turbo pumps as well as in other more conventional (commercial) machinery. The USAF Upper Stage Engine Technology (USET) program funded the work during the first decade of the 21st century.
Numerical Study on Aeroelastic Instability for a Low Speed Fan
Authors: Lee Kuen-Bae , Wilson Mark , Vahdati Mehdi 
Published: September 2016

Over recent years engine designs have moved increasingly toward low specific thrust cycles to deliver significant specific fuel consumption (SFC) improvements. Such fan blades are more loaded than conventional fan blades and therefore can be more prone to aerodynamic and aeroelastic instabilities. The aim of this paper is to analyse the flutter stability of a low speed/low pressure ratio fan blade. By using a validated CFD model (AU3D), three dimensional unsteady simulations are performed for a modern low speed fan rig for which extensive measured data are available. The computational domain contains a complete fan assembly with an intake duct and the downstream OGVs (whole LP domain). Flutter simulations are conducted over a range of speeds to understand flutter characteristics of this blade. Only the 1F (first flap) mode is considered in this work. Measured rig data obtained by using the same fan set but with two different intakes showed a significant difference in the flutter boundary for the two intakes. AU3D computations were performed for both intakes and were used to explain this difference between the two intakes, and showed that intake reflections play an important role in flutter of this blade. In the next phase of this work, two possible modifications for increasing the flutter margin of the fan blade were explored:
1. Changing the mode shape of the blade
2. Using acoustic liners in the casing
The results show that it is possible to increase the flutter margin of the blade by either decreasing the ratio of the twisting to plunging motion in 1F mode or by introducing deep acoustic liners in the intake. The liners have to be deep enough to attenuate the flutter pressure waves and hence influence the stability.
The results indicate the importance of reflection in flutter stability of the fan blade, and clearly show that intake duct needs to be included in flutter study of any fan blade.
Towards High Productive Roughing of Profiled Grooves in Nickel Based Alloys
Authors: Klocke F. , Doebbeler B. , Seimann M. , Binder M. 
Published: September 2016

Facing a high demand for aircraft engines over the next decades in combination with new challenging materials, aircraft engine manufacturers are striving for new manufacturing processes. The manufacturing of profiled grooves for the mounting of the turbine blades on the disc is a bottle neck process today due to the exclusive use of High Speed Steel (HSS) tools in broaching. Because of the limited hot hardness of HSS, the applied cutting speeds are low compared to other conventional machining processes, i.e. 2–5 m/min. Furthermore, the broaching process has some more drawbacks regarding flexibility, capital commitment for machinery and tools as well as costs. Nevertheless, broaching offers outstanding properties regarding surface finish, manufacturing accuracy and is still a productive process due to the many cutting edges applied. There are some alternative process chains which are not yet in industrial use, which are able to substitute and/or complement the HSS-broaching process.
In this paper, results are presented on two different roughing strategies for the manufacturing of profiled grooves in Nickel Based Alloys Allvac718plus and Inconel718. On the one hand, rough broaching with cemented carbide tools using indexable inserts was investigated at different cutting speeds, which are up to five times higher than the applied cutting speeds in industrial applications with HSS-tools. Two different carbide grades were investigated varying the cobalt content and the grain size. Cemented carbide is not state of the art in broaching Nickel Based Alloys due to its low fracture toughness. Different cutting edge inclination angles were applied and their effect on cutting forces, wear and tool chipping tendency were analyzed. On the other hand, rough side milling with ceramic cutting tools was investigated. Ceramic cutting tools excel in high hot hardness and thus can be used at very high cutting speeds i.e. up to 1000 m/min in Nickel Based Alloys. However, being very brittle and sensitive to alternating loads and thermal shock, machining processes with ceramic tools require extensive process design. In side milling experiments, Whisker reinforced as well as SiAlON and Oxide ceramic were investigated. In a first step, a window for machining parameters was identified. Then, tool life tests were conducted varying the feed at a fixed cutting speed of 1000 m/min. Subsequent to the experiments, the rim zone of the roughed grooves was investigated depending on the wear state of the used tools. The condition of the rim zone is a major criterion for the assessment of the adequacy of the roughing processes, because it can affect the subsequent finishing process. In further work, the interdependencies between the investigated roughing processes and finishing will be addressed.
Support Vibration Diagnostics and Limits in Gas Turbines
Authors: Bielecki Marcin , Costagliola Salvatore , Gebalski Piotr 
Published: September 2016

The paper deliberates vibration limits for non-rotating parts in application to industrial gas turbines. As a rule such limits follow ISO 10816-4 or API616, although in field operation it is not well known relationship between these limits and failure modes. In many situations, the reliability function is not well-defined, and more comprehensive methods of determining the harmful effects of support vibrations are desirable.
In the first part, the undertaken approach and the results are illustrated based on the field and theoretical experience of the authors about the failure modes related to alarm level of vibrations. Here several failure modes and diagnostics observations are illustrated with the examples of real-life data. In the second part, a statistical approach based on correlation of support vs. shaft vibrations (velocity / displacement) is demonstrated in order to assess the risk of the bearing rub. The test data for few gas turbine models produced by General Electric Oil & Gas are statistically evaluated and allow to draw an experimentally based transfer function between vibrations recorded by non-contact and seismic probes. Then the vibration limit with objectives like bearing rub is scrutinized with aid of probabilistic tools. In the third part, the attention is given to a few examples of the support vibrations — among other gas turbine with rotors supported on flexible pedestals and baseplate. Here there is determined a transfer coefficient between baseplate and bearing vibrations for specific foundation configurations. Based on the test data screening as well as analysis and case studies thereof, the conclusions about more specific vibration limits in relation to the failure modes are drawn.
The Application of Ceramic Matrix Composite to Low Pressure Turbine Blade
Authors: Watanabe Fumiaki , Nakamura Takeshi , Shinohara Ken-ichi 
Published: September 2016

The structural reliability of composite parts for aircraft is established through the “building block” approach, which is a series of tests that are conducted using specimens of various levels of complexity. In this approach, the failure modes and criteria are validated step by step with tests and analysis at coupon, element, sub-component, and component levels.
IHI is developing ceramic matrix composite (CMC) components for aircraft engines to realize performance improvement and weight reduction. We conducted the concept design of CMC low pressure turbine (LPT) blade with the building block approach. In this paper, we present the processes and results of the design, which was supported by a series of tests.
Typical low pressure turbine blade has dovetail, airfoil and tip shroud. Each element has different function and characteristic shape. In order to select the configuration of CMC LPT blade, we conducted screening tests for each element. The function of dovetail is to sustain the connection with blade and disk against centrifugal force. The failure modes and strength of dovetail elements were examined by static load tests and cyclic load tests. The configuration of airfoil was selected by modal tests. The function of tip shroud is forming gas passage and reducing the leakage flow, therefore this portion needs to sustain the shape against the centrifugal force and the rubbing force. The feasibility of tip shroud was verified by spin tests and rubbing tests. The initial CMC LPT blades were designed as combination of the selected elements by these screening tests. Prototype parts were made and tested to check the manufacturability and the structural feasibility. The static strength to the centrifugal force was examined by spin test. The durability to vibration was examined by HCF test.
Evaluation of Measurement Uncertainties for Pneumatic Multi-Hole Probes Using a Monte Carlo Method
Authors: Hölle Magnus , Bartsch Christian , Jeschke Peter 
Published: September 2016

The subject of this paper is a statistical method for the accurate evaluation of the uncertainties for pneumatic multi-hole probe measurements. The method can be applied to different types of evaluation algorithms and is suitable for steady flowfield measurements in compressible flows. The evaluation of uncertainties is performed by a Monte Carlo method (MCM), which is based on the statistical law of large numbers. Each input quantity, including calibration and measurement quantities, is randomly varied on the basis of its corresponding probability density function (PDF) and propagated through the deterministic parameter evaluation algorithm. Other than linear Taylor series based uncertainty evaluation methods, MCM features several advantages. On the one hand, MCM does not suffer from lower-order expansion errors and can therefore reproduce nonlinearity effects. On the other hand, different types of PDFs can be assumed for the input quantities and the corresponding coverage intervals can be calculated for any coverage probability.
To demonstrate the uncertainty evaluation, a calibration and subsequent measurements in the wake of an airfoil with a 5-hole probe are performed. MCM is applied to different parameter evaluation algorithms. It is found that the MCM approach presented cannot be applied to polynomial curve fits, if the differences between the calibration data and the polynomial curve fits are of the same order of magnitude compared to the calibration uncertainty.
Since this method has not yet been used for the evaluation of measurement uncertainties for pneumatic multi-hole probes, the aim of the paper is to present a highly accurate and easy-to-implement uncertainty evaluation method.
Experimental and Numerical Investigation on Leakage Characteristic of Stepped Labyrinth Seal
Authors: Zhang Li , Zhu Hui-ren , Liu Cun-liang , Tong Fei 
Published: September 2016

Labyrinth seals represent an important flow element in the secondary air system of aero engines. The influence of seal clearance and teeth parameters on the leakage characteristic of a real size stepped labyrinth seal was experimentally and numerically analyzed in a stationary state. Two kinds of labyrinth seals were studied in this investigation that are generally used in gas turbines, namely downward stepped labyrinth and upward stepped labyrinth. The differences of seal flow leakage mechanisms between the two types of the labyrinth were investigated. In order to eliminate the scaling effects on leakage losses in labyrinth seals, the experimental labyrinth seal model took the size of the real one in an aero engine. The experiments covered a range of pressure ratio from 1.1 to 3.5.
The experimental and numerical results show that in the range of the studied parameters the main teeth parameters affecting leakage coefficient are seal clearance, tooth tip thickness, tooth number and tooth front inclination. The influence of tooth height, pith and rear inclination angle on leakage coefficient of downward stepped labyrinth seal can almost be neglected in this research. And when the step height is more than twice the width of seal clearance, its effect on seal performance can be ignored. An empirical formula express of leakage coefficient with pressure ratio, seal clearance and teeth parameters of downward stepped labyrinth seal was organized which fits the experimental data with a maximal deviation of 8%. With similar pressure ratios and seal clearances, the downward stepped labyrinth seal displays lower leakage rates and provides the best sealing efficiency.
Numerical Investigation on Flow and Heat Transfer Characteristics of Steam and Mist/Steam in Internal Cooling Channels With Different Rib Angles
Authors: Zeng Junxiong , Gao Tieyu , Li Jun , Zhu Jiangnan , Fei Jiyou 
Published: September 2016

In order to further increase the gas turbine efficiency by increasing the turbine inlet temperature, an advanced cooling technology needs to be developed. Recently, mist /steam (air) cooling is considered as a promising technology to effectively cool the hot components such as gas turbine vanes and blades. A series of experimental investigations and numerical simulations conducted in the past proved the feasibility and superiority of mist cooling technology in elevated gas turbine working condition. The aim of this study is to numerically analyze the secondary flow structure and the influence of secondary flow distribution on heat transfer in steam and mist/steam cooling channels with different rib angles by using vortex core interaction. In addition, the heat transfer characteristics of steam and mist/steam in gas turbine cooling channels with rib angles of 30°, 45°, 60°, 90°, duct aspect ratio 2:1, Reynolds number ranging from 10000 to 60000 and mist ratio increasing from 2% to 8% are also investigated.
The commercial software ANSYS CFX 14.5 is used to solve the 3-D steady Reynolds-averaged Navier–Stokes equations with a SST turbulent model. The numerical results of Nusselt number (Nu) distribution along the centerline of each channel with steam-only are validated with the experimental values. Numerical results indicate that the predicted results are in good agreement with the experimental data. The distribution and strength of longitudinal secondary flows in 30°, 45°, 60° ribbed channels and transverse secondary flows in 90° ribbed channel have a great influence on the distribution of Nusselt number. The averaged Nu in 30°, 45°, 60° ribbed channels is higher than that in 90° ribbed channel due to longitudinal secondary flow having a better heat transfer performance than transverse secondary flow. The decrease of averaged Nu between two neighbored ribs along inclined ribs is mainly induced by the decreased strength of longitudinal secondary flow along the same direction in 30°, 45°, 60°ribbed channels. The averaged Nu of mist/steam with 5% mist injection in the four channels increases by 97.98%–151.9% compared with steam at Re=60000. Furthermore, the averaged Nu increases by about 11.08% to 213.6% compared with steam, when the mist ratio increases from 2% to 8%. The 60°ribbed channel achieves the best heat transfer performance in mist/steam cooling channels.