bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reliability Measurements for Gas Turbine Warranty Situations
Authors: Ekstrom Thomas E. 
Published: March 2015

Reliability performance is currently receiving significant attention in the bid requests for new gas turbine generating units. Reliability guarantees backed by liquidated damages clauses are becoming the rule rather than the exception. But the power generation industry does not have a universally accepted set of reliability measurements and the more commonly used measurements are not sufficiently refined for the warranty situation.
This paper is intended to provide the guidance, structure and refinement needed for meaningful reliability warranties.
Four key areas of reliability measurement: starting reliability, running reliability, availability and equivalent availability are separately addressed. And within each of these areas there is the flexibility, the methodology and the need to adapt the measurement system to the varied operating regimes and philosophies encountered such as: peaking vs. continuous service, attended vs. unattended sites, different levels of maintenance intensity, chargeable vs. non-chargeable outage events and emotional/political/optical acceptability (i.e., 3% Forced Outage Factor vs. 40% Forced Outage Rate). Warranty structuring rationale and suggested contract language are provided to address such needs as a rigorous and explicit operating log, certification of data, measurement accuracy, statistical confidence, assurance of readiness and risk assessment.
The suggestions presented herein have been constructed with logic and fairness. This paper will be beneficial to all Architect Engineers, Utilities, Independent Power Producers and OEM’s that become involved with the structuring of reliability warranties.
Relative Flow and Turbulence Measurements Downstream of a Backward Centrifugal Impeller
Authors: Ubaldi Marina , Zunino Pietro , Cattanei Andrea 
Published: March 2015

The paper presents the results of an experimental investigation on the three-dimensional relative flow at the exit of the backward bladed centrifugal impeller of the high pressure stage of a two stage biregulating pump-turbine model, operating at the pump nominal point.
Mean velocity, Reynolds stress tensor and total pressure of the relative flow have been measured with stationary hot wire probes and fast response miniature pressure transducers, by means of a phase locked ensemble average technique.
The results, shown in terms of secondary vector plots and contours of mean flow characteristics and Reynolds stress components, give a detailed picture of the flow kinematic structure and of the complex relative total pressure loss and turbulence distributions.
In spite of strongly backswept blades, the flow leaving the impeller presents a jet and wake structure and an intense secondary flow activity. Large relative total pressure losses affect the wake and the region where secondary vortices interact.
The turbulence data analysis provides information about the effects of the impeller rotation on the turbulence structure and about the mechanisms of the flow mixing process and of the secondary flow decay downstream of the impeller.
Performance and Emission Levels in Gas Turbine Plants
Authors: Bozza Fabio , Tuccillo Raffaele , Fontana Gustavo 
Published: March 2015

The rise in gas turbine combustion chamber temperatures requires optimal choices to be made with regard not only to performance parameters but also with a view to resolving pollutant emission problems. For this reason, the authors have set up a gas turbine cycle model which performs an accurate analysis of several processes, in terms of operating fluid chemical and thermodynamic properties. The model also enables prediction of NOx formation based upon chemical kinetics and is able to relate the amount of pollutants to a number of operating parameters (e.g. cycle pressure ratio, fuel to air equivalence ratio, residence time in combustion chamber, etc.). It can also predict the effect of the most usual NOx reduction systems, such as water or steam injection.
A comparison of several possible choices for the gas and combined cycles is then presented, in terms of thermodynamic performance (e.g. first and second law analysis) and nitric and carbon dioxide emissions. In order to find the best compromise between performance improvement and limitation of pollutant emission, enhanced gas cycles are also considered, such as STIG or intecooled-reheat cycles.
Examples also refer to medium or low BTU gases, obtained from coal gasification, in order to show not only the possible advantages in terms of thermal NOx reduction, but also the significant amounts of “fuel NOx“ which can arise from ammonia contained in the fuel.
Design Features Influencing the Distribution of Fuel Within the Spray From an Air Blast Fuel Injector
Authors: Stringer F. W. , Irwin A. N. 
Published: March 2015

This paper describes work carried out to determine the influence of several design features upon the performance of an air blast fuel injector. The design features studied were the number of tangential fuel holes feeding the swirl chamber, the depth of the swirl chamber, and the shape of the downstream section of the swirl chamber.
The performance parameters considered were, fuel distribution, flow number, air side effective area, spray cone angle and spray SMD. The fuel used was aviation kerosine.
Apparatus for the relatively simple and rapid determination of the fuel distribution within the spray is also described.
MTR390—Engine for the Future
Authors: Spirkl A. , Ducos J. S. , Thorn R. 
Published: March 2015

The design of the MTF390, a turboshaft engine in the 1000 kw range, is based on proven technology and components developed well in advance of the actual programme start. The engine features a two stage centrifugal compressor, an annular reverse flow ring combustor, a single stage air cooled gas generator turbine, a two stage free power turbine, an integrated reduction and accessory gearbox with integral oil system. A full authority digital engine control provides the engine and system monitoring functions.
The development programme, which also includes a comprehensive integrated logistics support programme, is running according to schedule, more than 1400 engine hours have been logged including 200 flight hours with both a Flying Test Bed and the TIGER prototype helicopter.
Viscous Throughflow Modelling for Multi-Stage Compressor Design
Authors: Howard M. A. , Gallimore S. J. 
Published: March 2015

An existing throughflow method for axial compressors, which accounts for the effects of spanwise mixing using a turbulent diffusion model, has been extended to include the viscous shear force on the endwall. The use of a shear force, consistent with a no-slip condition, on the annulus walls in the throughflow calculations allows realistic predictions of the velocity and flow angle profiles near the endwalls. The annulus wall boundary layers are therefore incorporated directly in the throughflow prediction. This eliminates the need for empirical blockage factors or independent annulus boundary layer calculations.
The axisymmetric prediction can be further refined by specifying realistic spanwise variations of loss coefficient and deviation to model the three-dimensional endwall effects. The resulting throughflow calculation gives realistic predictions of flow properties across the whole span of a compressor. This is confirmed by comparison with measured data from both low and high speed multi-stage machines.
The viscous throughflow method has been incorporated into an axial compressor design system. The method predicts the meridional velocity defects in the endwall region and consequently blading can be designed which allows for the increased incidence, and low dynamic head, near to the annulus walls.
Ingestion Into the Upstream Wheelspace of an Axial Turbine Stage
Authors: Green T. , Turner A. B. 
Published: March 2015

The upstream wheelspace of an axial air turbine stage complete with nozzle guide vanes (NGV’s) and rotor blades (430 mm mean diameter) has been tested with the objective of examining the combined effect of NGV’s and rotor blades on the level of mainstream ingestion for different seal flow rates.
A simple axial clearance seal was used with the rotor spun up to 6650 rpm by drawing air through it from atmospheric pressure with a large centrifugal compressor. The effect of rotational speed was examined for several constant mainsteam flow rates by controlling the rotor speed with an air brake.
The circumferential variation in hub static pressure was measured at the trailing edge of the NGV’s upstream of the seal gap and was found to significantly affect ingestion. The hub static pressure distribution on the rotor blade leading edges was rotor speed dependent and could not be measured in the experiments. The Denton 3D C.F.D. computer code was used to predict the smoothed time dependent pressure field for the rotor together with the pressure distribution downstream of the NGV’s.
The level and distribution of mainstream ingestion, and thus the seal effectiveness, was determined from nitrous oxide gas concentration measurements and related to static pressure measurements made throughout the wheelspace.
With the axial clearance rim seal close to the rotor the presence of the blades had a complex effect. Rotor blades in connection with NGV’s were found to significantly reduce mainstream ingestion seal flow rates, but a small level of ingestion existed even for very high levels of seal flow rate.
Utility Perspective of Selecting Air Filter for Simple-Cycle, Heavy-Duty Combustion Turbines
Authors: Lyons James W. , Morrison Alex 
Published: March 2015

The combustion turbines evaluated for this study range in size (nominal) from 80 MW to 100 MW and operate at a compression ratio between 10 and 14. Under these conditions the compressor ingests about 500,000 to 725,000 cubic feet of air per minute for its rated output. With this volume of air, even low concentrations of contaminants can result in a significant total amount of contaminants entering the unit, which may cause compressor erosion, fouling, and foreign object damage in the compressor section and cooling air passage blockage, locking of turbine blade roots, and hot corrosion or sulfidation in the turbine section. Adequate protection against the above mentioned degradation or damage due to poor air quality may be obtained by using properly designed air filters. An inadequate filter system or having no filter system results in a reduction in power and efficiency over the life of the unit and may significantly decrease the intervals between maintenance and thereby increase the cost of maintenance. Consideration should be given to adding an air inlet filter when or after the combustion turbine without air filter is overhauled to reduce future maintenance costs.
This study investigates the need for an inlet air filtration system for the simple-cycle, heavy-duty combustion turbines from a cost/benefit and operation standpoint. Options for inlet air filters include a self-cleaning pulse type filter, a surface loading cartridge filter without pulse feature, and a three-stage depth loading type media type filter. Benefits are determined by estimates of improvements in performance and effects on the combustion turbine’s longevity and maintenance.
Some Basic Reflections About the Influence of Non-Metallic Inclusions on Rolling Contact Fatigue of Bearing Steels
Authors: Böhmer Hans-Jürgen 
Published: March 2015

The detrimental influence of inclusions on rolling contact fatigue behaviour of bearing steel is well known and empirically described. Yet only a few publications exist where the effect of inclusions is investigated analytically. This paper presents a new method to describe the influence of inclusions based on a mechanical analysis.
From this analysis some general effects of inclusions on material stress and behaviour in rolling contact fatigue were concluded. The actual “notch effect” of inclusions is qualitatively independent on their specific properties, even if they are more pliable or stiffer than the matrix. Only the amount of the notch effect is — to a certain extent — dependent on their respective properties. Many discrepancies between classical theory of Hertzian contact and damage analysis of rolling element bearings can be explained by this analysis.
The correct appraise of compressive residual stresses in rolling contact fatigue is strongly bound to the consideration of inclusions. It is shown that compressive residual stresses have the greatest benefit if they are about 15% of the applied Hertzian pressure. Exceeding this value may be detrimental.
Effects of Free-Stream Turbulence and Adverse Pressure Gradients on Boundary Layer Transition
Authors: Gostelow J. P. , Blunden A. R. , Walker G. J. 
Published: March 2015

Boundary layer measurements are presented through transition for six different free-stream turbulence levels and a complete range of adverse pressure gradients for attached laminar flow.
Measured intermittency distributions provide an excellent similarity basis for characterizing the transition process under all conditions tested when the Narasimha procedure for determining transition inception is used. This inception location procedure brings consistency to the data.
Velocity profiles and integral parameters are influenced by turbulence level and pressure gradient and do not provide a consistent basis. Under strong adverse pressure gradients transition occurs rapidly and the velocity profile has not fully responded before the completion of transition. The starting turbulent layer does not attain an equilibrium velocity profile.
A change in pressure gradient from zero to even a modest adverse level is accompanied by a severe reduction in transition length. Under diffusing conditions the physics of the transition process changes and the spot formation rate increases rapidly; instead of the “breakdown in sets” regime experienced in the absence of a pressure gradient, transition under strong adverse pressure gradients is more related to the amplification and subsequent instability of the Tollmien-Schlichting waves. Measurements reveal an exponential decrease in transition length with increasing adverse pressure gradient; a less severe exponential decrease is experienced with increasing turbulence level. Correlations of transition length are provided which facilitate its prediction in the form of suitable length parameters including spot formation rate.
ATTAP Ceramic Gas Turbine Technology Development
Authors: Smyth J. R. , Morey R. E. 
Published: March 2015

In the Advanced Turbine Technology Applications Project (ATTAP), Garrett Auxiliary Power Division (GAPD) continues to address critical technologies for the application of ceramics in gas turbine engines. Design methods and component and fabrication development are culminating in rig and engine testing to confirm ceramic technology development. Analytical methods for designing impact-resistant ceramic engine components have been verified in experiments, and improved regenerator seals and combustor designs have been tested. Engineered process development by selected subcontractors has resulted in delivery of high-quality ceramic components. All of these efforts are aimed at a planned all-ceramic turbine engine demonstration for 300 hours operation up to 2500F (1371C).
ATTAP is a continuing program funded by the U.S. Department of Energy (DOE) Office of Transportation Technologies and administered by the NASA-Lewis Engineering Research Center under Contract No. DEN3-335.
An Externally Pressurized Air Bearing System, Journals and Thrust, for Application to Small Turbomachinery
Authors: Turner A. B. , Davies S. J. , Nimir Y. L. , Richardson J. D. 
Published: March 2015

An aerostatic (externally pressurized) air bearing system for application to small high speed, low temperature turbomachinery has been designed and successfully tested at over 100,000 rpm using an air supply at a gauge pressure of 3.4 bar (50 psig).
The test rig used a Holset turbocharger centrifugal compressor impeller and radial turbine wheel mounted at either end of a 150 mm long 40 mm diameter shaft with two 23 mm long inboard journal bearings mounted on either side of an integral 100 mm diameter tapered thrust collar. The turbine was driven by an independent air supply with a maximum temperature of 200°C, and the unit was operated with the shaft vertical. A static axial thrust capability of over 1000 N (225 lbf) has been demonstrated using a novel plenum chamber arrangement to overcome pneumatic instability (air hammer) problems. The paper presents details of the design, some static rig tests and the dynamic test conditions and results.
Aircraft Engine Integration for the M88-RAFALE Couple
Authors: Ramette Philippe , Corde Jean Christophe 
Published: March 2015

As all other comparable programs, the couple RAFALE-M88 has to be a fully optimized multirole weapon system with the highest level of integration; a key factor for that purpose is the very good prebuilt integration of the engine within the aircraft.
After a short description of the main historical milestones of the aircraft and engine programs development and integration, the paper will first summarize the rigourous procedures which are used by aircraft and engine manufacturers, official services and future Air Force and Navy users.
Then, the paper will detail the main points where aircraft engine integration as to be lead precisely and carefully; these points are:
-at first, the electronical links which are establised between the aircraft and the engine, due to the high complexity of flight softwares who have to work and talk with each others;
-secondly, the aerodynamical subjects, including air intake and exhaust nozzle installation;
-thirdly, the mechanical integration (geometry, mechanical behaviour, …);
-then all kinds of fluid circuits or equiments.
Textron Lycoming AGT1500 Engine Operational and Support Cost Reduction
Authors: Pellegrino Edward 
Published: March 2015

An aggressive program to significantly reduce the sustainment cost of the M1 Abrams Main Battle Tank Powertrain was initiated by the Army Material Command (AMC) in 1985. The powerpack (engine and transmission) sustainment cost had been calculated by the Army to be twenty-one percent (21%) of the total M1 sustainment cost with the engine accounting for fourteen percent (14%) of the total. Although this figure was considerably less than the original assumption of thirty percent (30%) for the engine alone, the cost was considered significant.
In order to achieve the Army mandated fifty percent (50%) savings on sustainment cost, Textron Lycoming pursued an aggressive reliability improvement program recognizing the potential to increase operational readiness while decreasing future operational and support cost. A major milestone was achieved by 1988 when the powerpack sustainment cost was calculated to be ten percent (10%) of the total M1 sustainment cost.
In 1989, a study conducted by Textron Lycoming concluded that additional and substantial operational and support cost reductions could be realized by addressing and improving the engine’s field maintenance concept and its application.
Gas Turbine Driving Reciprocating Compressors Experience in Natural Gas Applications
Authors: Giacomelli E. , Petrini P. , Montelatici A. , Desolati M. 
Published: March 2015

The flexibility of reciprocating compressors combined with the utilization of variable speed drives like gas turbines optimizes operating and capital investment costs in natural gas services. Reliability and respect for limits specified in pollution control regulations are the most significant requirements related to modern compression stations. Equipped with monitoring systems, the trains must benefit by special design procedures and modern full-load test facilities to ensure the complete confidence of users.
The above features, together with energy saving advantages, make it possible to forecast the increasing application of compressor - turbine arrangements.
Inverse Design of Compressor and Turbine Blades at Transonic Flow Conditions
Authors: Léonard O. , Van den Braembussche R. A. 
Published: March 2015

This paper describes the design of realistic blade shapes using an inverse method. Special attention is given to the geometrical and mechanical constraints imposed upon the blade.
Examples presented in this paper illustrate how a better understanding of the theoretical relations between imposed velocity and resulting geometry can help satisfy the geometrical restrictions. Another method using a numerical procedure for finding a compromise between the target velocity distribution and geometrical restrictions is also proposed and illustrated by an example.
A blade design procedure using an inviscid inverse method and a boundary layer calculation method is described and applied to the design of a shock free transonic compressor cascade. The iterative character of the procedure provides a blade shape control good enough to design sufficiently thick blades resulting in realistic geometries. The blade shape coordinates are given as a possible bench mark for inviscid or viscous two-dimensional methods.
Ceramics for Aero-Engine Applications
Authors: Wortmann J. , Prewo K. M. 
Published: March 2015

In the general aero-engine development effort to significantly improve specific fuel consumption as well as thrust-to-weight ratios, ceramics have been under investigation since the mid-Seventies. Their great potential for increasing gas-turbine performance has resulted in a number of research programs worldwide to assess their desirability for static or rotating components.
There has been remarkable progress in the drive to improve material strength by especially process control and the clean room approach. This development has been assisted by revised design and lifing methods. Thus static components like hybrid vanes and combustor rings have withstood temperatures of up to 1650 °C for several hundred hours and some ten cycles. But for ceramics, one essential property required of all aero-engine materials — defect tolerance, or the ability to reduce stresses in a controlled manner — still falls short of the standard commonly associated with other materials.
Attention is therefore focused on methods of controlling the inherently poor defect tolerance of ceramic materials by appropriate design concepts (small volumes, simple shapes, constant wall thickness, compression stress state) and by strengthening the material proper through fiber reinforcement.
Apart from the ambitious application of monolithic or fibrereinforced ceramics as structural components in the hot gas path in extremely high temperature environments, some applications, such as thermal barrier coatings, bearings and flaps, have already reached the production stage.