bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance Prediction and Analysis of a Three-Shaft Gas Turbine Supported by Turbine Cooling Model
Authors: Ji Xingxing , Gu Chunwei , Song Yin , Xie Weihong 
Published: September 2014

Performance prediction method of the modern gas turbine is an important tool for the engine design and performance analysis. This paper integrates a hybrid cooling model to the previous research of gas turbine performance prediction method which is applied to predict the multi-shaft gas turbine performance. The cooling model, combined with the semi-empirical model and analytical model, had been originally proposed for the investigation of turbine convective cooling or film cooling performance. The aim of the work is to apply the hybrid model to effectively estimate the coolant requirement in the gas turbine performance prediction, therefore to improve the reliability of the analysis in the innovative gas turbine cycle.
The analysis involved a three-shaft gas turbine. Experiments were carried out on the engine, and the effectiveness of the prediction method is validated by the experiment. Consequently detailed performance characteristic of the engine is investigated under different stagger angles of the variable-angle nozzle, revealing how the stagger angle of the variable-angle nozzle and the turbine inlet temperature affect the gas turbine performance. The analysis is considered valuable for the engine operation and components optimization.
Selecting Cavity Geometries for Improving the Aerodynamic Performance of an Axial Compressor
Authors: Flores Diego , Seume Joerg R. 
Published: September 2014

Designers and researchers have traditionally sought to minimize aerodynamic losses in turbomachinery without considering the influence of fillets, seals and cavities. The validity of this assumption is investigated in the present paper. Three different cavity geometries have been implemented in the third stage of a four-stage high-speed axial compressor. To better understand the interaction between the main flow path and the secondary flow caused by leakage through labyrinth seals, three different cavity outlet angles have been investigated: 90°, 45°, and 135° with respect to the main flow path direction. Moreover, three different clearances between the seal tips and the stator have been used in order to investigate the leakage mass flow inside the cavity. Three-dimensional steady RANS simulations with two different turbulence models using the TRACE solver by DLR have been performed in all cases. The SST turbulence model showed higher fidelity when compared to experimental data and proved more sensitive to variations of parameters studied. A comparison of aero-thermodynamic results in the main flow path for the different configurations at the inlet and outlet of the cavities shows that the radial profiles are strongly influenced by clearance height H and cavity outlet angle a in the third stator as well as rotor. A cavity outlet directed against the main flow direction gives the best results in terms of compressor overall efficiency.
The results also reveal some modeling limitations in that neither of the two turbulence models can precisely predict the progressive temperature rise noticed in the experimental data above of 55% blade height in the third stator and rotor, pointing at deficiencies in modeling the tip clearance vortex.
Comparison of Ni-Based 625 Alloy and ATI 20-25+Nb™ Stainless Steel Foils After Long-Term Exposure to Gas Turbine Engine Exhaust
Authors: Bender M. D. , Klug R. C. 
Published: September 2014

A field test program to validate the high temperature oxidation resistance of the ATI 20-25+Nb™ alloy in a Solar Turbines Incorporated Mercury™ 50 gas turbine engine has exceeded 66,000 operating hours. The primary goal of this program is to assess the effect of the actual recuperator operating environment on the high temperature degradation of primary surface recuperator (PSR) materials. As PSRs are generally fabricated from thin foil materials, excessive degradation can cause perforation or collapse, leading to decreased performance or failure. To avoid such issues, PSRs are generally fabricated from highly-alloyed austenitic stainless steels or nickel-base superalloys.
This field test program evaluates and compares the long-term performance of the iron-based austenitic ATI 20-25+Nb™ stainless steel (UNS S35140) with the more highly alloyed nickel-based 625 alloy (UNS N06625) in an in-situ turbine exhaust environment.
Sub-size air cell samples of alloy 625 and ATI 20-25+Nb™ alloy, exposed for 66,000 hours (running time) in turbine exhaust, were removed and tested for materials characterization. Analysis showed that both alloys exhibit excellent long-term resistance to environmental degradation, even after service exposures equivalent to over 7.5 years.
Steady-State Power Operation of a Supercritical Carbon Dioxide Brayton Cycle
Authors: Clementoni Eric M. , Cox Timothy L. 
Published: September 2014

Bechtel Marine Propulsion Corporation (BMPC) is testing a supercritical carbon dioxide (S-CO2) Brayton system at the Bettis Atomic Power Laboratory. The Integrated System Test (IST) is a two shaft recuperated closed Brayton cycle with a variable speed turbine driven compressor and a constant speed turbine driven generator using S-CO2 as the working fluid designed to output 100 kWe. The main focus of the IST is to demonstrate operational, control and performance characteristics of an S-CO2 Brayton power cycle over a wide range of conditions.
IST operation has reached the point where the system can be operated with the turbine-compressor thermal-hydraulically balanced so that the net output of the system is equal to the turbine-generator output. In this operating mode, power level is changed by using the compressor recirculation valve which changes the fraction of compressor flow that goes to the turbines. Steady-state operation with the turbine-compressor thermal hydraulically balanced at near zero net system power is presented.
Comparison of Carbon Dioxide Property Measurements for an Operating Supercritical Brayton Cycle to the REFPROP Physical Property Database
Authors: Clementoni Eric M. , Cox Timothy L. 
Published: September 2014

Supercritical carbon dioxide (S-CO2) power cycles have been gaining interest in recent years due to their high efficiency and compact components. As interest in CO2 cycles grows, work is being done to test the operation and control of these cycles and model individual component and system performance. A key aspect in this work is the accuracy of the physical properties of the fluid used in the design, system operation, and model validation efforts. A commonly used physical property database is the NIST REFPROP database which implements correlations developed for CO2 by Span and Wagner.
Bechtel Marine Propulsion Corporation (BMPC) is testing an S-CO2 Brayton system at the Bettis Atomic Power Laboratory. The Integrated System Test (IST) is a two shaft recuperated closed Brayton cycle with a variable speed turbine-driven compressor and constant speed turbine-driven generator using S-CO2 as the working fluid designed to output 100 kWe. The IST utilizes coriolis mass flow meters to measure system flow rates as well as CO2 density at various points in the loop. Operational test data for CO2 temperature, pressure, and density are presented and comparisons made on the ability to accurately calculate the density of CO2 using REFPROP with temperature and pressure measurements for an operating Brayton loop. An uncertainty analysis using vendor specified instrument accuracy was performed to show that the calculated and measured properties of CO2 for the operating conditions examined are in good agreement.
Experimental Study on Local Heat Transfer in a Rotating, Two-Pass Cooling Channel With Dense Array of Turbulence Promoters With Naphthalene Sublimation Method
Authors: Hagari Tomoko , Ishida Katsuhiko , Takeishi Kenichiro , Komiyama Masaharu , Oda Yutaka 
Published: September 2014

Detailed heat transfer coefficient distributions in a rotating, two-pass, square channel with densely arranged rib turbulators on the leading and trailing walls are investigated. Rib turbulators have been used in a cooling channel of turbine airfoils. The dense arrangement of the ribs is one of the potential candidates to improve heat transfer performance because of its surface area enlargement effect.
The ribs are arranged with a rib height to channel hydraulic diameter ratio (e/Dh) of 0.13, angles of attack to the mainstream of 60 and 90deg, and rib pitch-to-height ratios (P/e) of 3, 6 and 10. Both rib and floor surfaces are coated with naphthalene to measure their local mass transfer rate, which is correlated with heat transfer coefficient through heat/mass transfer analogy. Combination of a laser displacement sensor and a precision auto-traverse system enables detailed measurement of local heat transfer distribution on the floor surface between the ribs. Overall heat transfer coefficient including the effect of the rib is obtained by measuring the decrease in weight of the naphthalene test piece. Reynolds number is set at 50,000 and rotation numbers are up to 0.05.
The results show that the effect of rotation on local heat transfer behavior depends on the rib spacing and orientation. Compared the overall heat transfer coefficients with the local ones on the floor surface, they showed different trend in some cases. This suggests that variation of rib heat transfer characteristics due to rotation might determine the overall heat transfer coefficient. Such tendency would be stronger for smaller rib spacing because surface area of the rib has large portion of the total heat transfer area. Further investigation on this effect is expected by measuring heat transfer of rib itself under rotating condition.
Off-Design Performance of a Highly Loaded LP Turbine Cascade Under Steady and Unsteady Incoming Flow Conditions
Authors: Berrino Marco , Simoni Daniele , Ubaldi Marina , Zunino Pietro , Bertini Francesco 
Published: September 2014

The off-design performance of a highly loaded LP turbine cascade has been experimentally investigated, at the Aerodynamics and Turbomachinery Laboratory of Genova University, under steady and unsteady incoming flow conditions. Tests have been performed for different Reynolds numbers (Re = 70000 and Re = 300000), in order to cover the typical LP turbine working range. The incidence angle has been varied between i = −9° and +9°, in order to test off-design conditions characterizing the engine. For the unsteady case upstream wake periodic perturbations have been generated by means of a tangential wheel of radial rods. The cascade and the moving bars system have been located over a common bearing in order to make them rigidly rotating. This solution allows a proper comparison of the cascade robustness at the incidence angle variation under steady and unsteady incoming flows, since all the other operating parameters have been kept the same. In order to survey the variation of the unsteady boundary conditions characterizing the off-design operation of the downstream cascade, time-mean and time-resolved wake structures have been analyzed in detail.
For what concerns the cascade performance, profile aerodynamic loadings and total pressure loss coefficients at the cascade exit have been surveyed for the different incidence angles under both steady and unsteady inflows. Different total pressure loss sensitivity at the incidence angle variation has been observed for the steady and the unsteady inflow conditions.
Hot-wire anemometer has been employed to obtain the time-mean pressure and suction side boundary layer velocity profiles at the blade trailing edge for the different conditions. The integral parameters at the cascade exit plane help to justify the different loss trend vs incidence angle found for the steady and the unsteady cases, explaining the different sensibility of the blade profile when this operates under realistic unsteady inflow condition.
Emergency Shutdown Management in Fuel Cell Gas Turbine Hybrid Systems
Authors: Lambruschini Fabio , Ferrari Mario L. , Traverso Alberto , Larosa Luca 
Published: September 2014

A real-time dynamic model representing the pressurized fuel cell gas turbine hybrid system emulator test rig at Thermochemical Power Group (TPG) laboratories of the University of Genoa has been developed to study the fuel cell behavior during different critical operative situations like, for example, load changes (ramp and step), start-up and shut-down and, moreover, to implement an emergency shutdown strategy in order to avoid any damage to the fuel cell and to the whole system: focus has been on cathode/anode differential pressure, which model was validated against experimental data. The real emulator plant (located in Savona University campus) is composed of a 100 kW recuperated micro gas turbine, a modular cathodic vessel (4 modules of 0.8 m3 each) located between recuperator outlet and combustor inlet, and an anodic circuit (1 module of 0.8m3) based on the coupling of a single stage ejector with an anodic vessel.
Different simulation tests were carried out to assess the behavior of cathode-anode pressure difference, identifying the best control strategies to minimize the pressure stress on fuel cell stack.
Minimum Environmental Load Reduction in Heavy Duty Gas Turbine by Bleeding Lines
Authors: Cioffi Marco , Piola Stefano , Puppo Enrico , Silingardi Andrea , Bonzani Federico 
Published: September 2014

The power generation and energy market scenarios are requiring the power generation plants to fulfill more flexible operations respect to the recent past. One of the main concerns of plant operators is the lowering of minimum load at which the machines can be exercised while respecting the pollution limits. A strategy to improve minimum turndown capability by reducing the minimum environmental load of heavy duty axial gas turbines is here presented: it is based on the use of the compressor air bleeding lines (blow-off lines).
The described technical development activities are based on the numerical modeling of blow-off lines and bleeding compressor sections; these preliminary tasks have been followed by on-field plant testing.
The blow-off lines modeling reserves a particular regard, due to the somehow non-usual fluid dynamics involved. A Fanno flow 1D approach has been adopted to properly model the bleeding lines fluid flow whereas full 3D numerical solutions have been developed to get a better insight of the bleeding plenums and of the line sector including the valve. In addition, the gas turbine components off-design behavior and the overall performances are computed by the Ansaldo modular simulation code. Numerical analysis and performed field tests are here presented and results are compared, showing a good agreement, in accord to the simplified model adopted. Additional comparisons with different alternative strategies are finally presented in terms of gas turbine power and excess air variation.
The described technique by blow-off lines opening shows to be able to fulfill the required task by incrementing the plant operative flexibility and guaranteeing safe plant operation. The technique drawbacks are a gas turbine slightly lower efficiency and the lower output flue gas temperature, whose relative importance have to evaluate by the plant operators. At present the long term sustainability of the new operative condition is the object of a deeper and longer field testing phase.
Secondary Flows and Fillet Radii in a Linear Turbine Cascade
Authors: Mank Sebastian , Duerrwaechter Lukas , Hilfer Michael , Williams Richard , Hogg Simon , Ingram Grant 
Published: September 2014

Most large scale cascade experiments and the corresponding computational fluid dynamics are conducted on geometries without fillet radii, that is with sharp edges. Despite that the fact that all real machines have a fillet radii there has not so far been a detailed examination of the influence of fillet radii on the secondary flow structures in turbines.
This paper presents detailed measurements on a large scale, low speed cascade with significant secondary flows. A series of detailed traverses inside the blade row were obtained allowing the influence of fillet radii on the formation of secondary flows to be examined. The experimental campaign is backed up by RANS computations.
The fillets were found to increase loss by around 10% compared to the base case. This loss could not be accounted for by a simple model of boundary layer behaviour and an accounting of the complex secondary flow interactions is required to explain the observed changes in performance. The secondary flow interactions include a larger radial migration of secondary flows from the endwall and the elimination of the corner vortex. The potential to improve performance by varying the fillet radii around the blade was identified.
Experimental Characterization of the Flow-Field Downstream of an Innovative Ultra Low NOx Injection System
Authors: Berrino Marco , Satta Francesca , Ubaldi Marina , Zunino Pietro , Colantuoni Salvatore , Di Martino Pasquale 
Published: September 2014

The present paper is focused on the characterization of the aerodynamics of the nonreacting flow downstream of an innovative Ultra Low NOx (ULN) injection system. The system is aimed at reducing NOx emissions and combustor axial length, to obtain a more compact and lighter low-emission combustor. The flow path downstream of the injection system has been investigated by means of Particle Image Velocimetry (PIV) and Hot Wire Anemometry (HWA). Particle Image Velocimetry measurements have been carried out in the meridional plane and in three frontal planes, in order to measure mean velocity components and their fluctuations, as well as to identify the coherent structures that characterize the time-varying flow. Hot Wire Anemometry has been used to investigate the unsteady behavior of the flow and to detect the presence of velocity fluctuation frequencies at different radial and axial positions downstream of the injection system. The HWA technique allowed the identification of the frequencies associated with the precession motion due to the vortex breakdown and with the coherent structures at the interface between the inverse flow region and the jets. The experimental results show a large reverse flow region at the exit, without any back-flow within the injection system, hence offering the evidence that the injection system may be able to stabilize the flame, without inducing risks of flash-back or auto-ignition phenomena. Moreover, the mean velocity distributions show the injection system ability of keeping separated the two jets coming out from the internal and external swirlers, with the consequent possibility of applying fuel-staging.
Furthermore, the experimental results have been compared to CFD RANS calculations and used for the validation of the numerical procedure.
A Method for Forecasting the Condition of HPT NGVs by Using Bayesian Belief Networks and a Statistical Approach
Authors: Giesecke Daniel , Friedrichs Jens , Kenull Thomas , Binner Matthias , Siegert Martin 
Published: September 2014

Jet engine maintenance is a very competitive field in terms of time and costs. To increase planning security and reduce turnaround time (TAT) of the maintenance process it is important to get as much engine data as possible before disassembly. Aero engines are especially subjected to environmental and operational influences. For the high pressure turbine (HPT), the following parameters have been identified to describe the deterioration of its nozzle guide vane (NGV): On-wing cycles, NGV material, airport region, engine wing position, thrust rating, vane repair history and customer business segment.
The combined influences of the parameters are non-trivial and it is not possible to acquire them analytically. There are no known mathematical laws connecting the above-mentioned parameters. The linear regression method set limits for processing data in an adequate manner. This is confirmed by the analysis of the arithmetic means and standard deviations. Especially the standard deviation values fit in a broad spectrum due to various reasons. Thus, it is not feasible to make an appropriate forecast with a simple statistical method due to the multidimensional character of the parameters influencing the accuracy. For this reason, advanced methods need to be developed to derive a feasible forecast method.
By applying a statistical hypothesis test, a bayesian belief network (BBN) has been designed. It allows the use of imprecise data without suffering a significant loss in forecast accuracy and additionally, the implementation of expert knowledge. The objective of this study is to develop an effective BBN in order to adequately predict the next repair of the first stage HPT NGV of the General Electric CF6-80C2 engine. The reason for selecting the NGV is due to its high susceptibility to different influences, combined with the significant costs and TAT during the maintenance process.
Having poor forecasting quality by using a simple statistical method, the evaluation of the BBN provides very satisfactory accuracy of above 80 percent which is equivalent to 19 out of 23 vane segments. Furthermore, the developed BBN emphasises robustness when detecting the expected tendencies while having only a limited amount of input parameters. Further work includes application of this method on other engine components as well as establishing the business value of the developed method. In conclusion, BBN have tremendous potential for forecasting the repair of the entire jet engine.
Quantitative CFD Analyses of Particle Deposition on a Transonic Axial Compressor Blade: Part II — Impact Kinematics and Particle Sticking Analysis
Authors: Suman Alessio , Morini Mirko , Kurz Rainer , Aldi Nicola , Brun Klaus , Pinelli Michele , Spina Pier Ruggero 
Published: September 2014

In heavy-duty gas turbines, the micro-particles not captured by the air filtration system can cause fouling and, consequently, a performance drop of the compressor. This paper presents three-dimensional numerical simulations of the micro-particle ingestion (0–2 μm) on an axial compressor rotor carried out by means of a commercial computational fluid dynamic code. Particle trajectory simulations use a stochastic Lagrangian tracking method that solves the equations of motion separately from the continuous phase. The NASA Rotor 37 is considered as a case study for the numerical investigation. The compressor rotor numerical model and the discrete phase model were previously validated by the authors in the first part of this work.
The kinematic characteristics (velocity and angle) of the impact of micrometric and sub-micrometric particles with the blade surface of an axial transonic compressor are shown. The blade zones affected by particle impact were extensively analyzed and reported in the first part of this work, forming the starting point for the analyses shown in this paper.
The kinematic analysis showed a high tendency of particle adhesion on the suction side, especially for the particles with a diameter equal to 0.25 μm. Fluid dynamic phenomena and airfoil shape play a key role regarding particle impact velocity and angle.
This work has the goal of combining, for the first time, the kinematic characteristics of particle impact on the blade with fouling phenomenon by the use of a quantity called sticking probability adopted from literature.
From these analyses, some guidelines for a proper management of the power plant (in terms of filtration and washing strategies) are highlighted.