bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Development of a Specially Modified Positive Displacement Rotary Screw Pump and Relevant Hydraulic Circuit to Enhance “Entrained Air Handling” Capability in a Closed Loop Lube Oil System
Authors: Berti Simone , Fracassi Pietro , Mattioli Alessandra , Potula Varuna Reddy , Lotti Cristiano
Published: November 2013

Rotary screw type positive displacement (RSPD) pumps are commonly used in Oil and Gas Industry for pumping of mineral lube oil in services where they can be mechanically driven by gears coupled to a train driver. Installation of these pumps is critical and should be designed jointly by vendors and users according to project specific restrictions (i.e. the arrangement of the entire oil circulation system). This paper describes a real case in which restrictions due to lube oil system arrangement have produced low pump suction head and have amplified the influence of air bubbles that remained entrained in oil despite lube oil tank degassing.

The investigations have been directed toward the mathematical modeling of the aeration phenomenon coupled with experimental measurements of critical parameters taken on the shop plant. Among corrective actions identified and considered there are reduction of quantity of air entering the lube oil system and revamping of the entire lube oil system with changes in piping, tank and also in pump model together with special modifications of internal path to enhance air handling capabilities. In order to validate pump behavior with reference to resistance to aeration (monitoring noise and vibration) a special simulation set-up was jointly developed by end user and manufacturer on a pilot test bench to carry out the various performance tests.

The numerical data collected during shop aeration test have confirmed that the pump was able to handle the expected amount of entrained air with noise and vibrations within industrial limits. The pumps tested in the pilot bench were installed at user’s site and the effectiveness of the synergic corrective actions listed above was successfully verified.

The study concludes that an early estimation of entrained air in the lube oil system is critical for design and development of either the RSPD pump or the entire lube oil circuit of a motor compressor train. When a critical quantity of entrained air is likely to be reached at pump suction (near 10% in volume), pump manufacturers and end users should apply some basic rules related to “design for aeration” of the pump and agree on a non-routine test to be performed at manufacturer’s shop before pump installation at site. This will serve as a reliable prediction of pump air handling capabilities, without which effective operation, reliability and durability of the pump could be jeopardized.
Prediction of Pressure Amplitudes of Self-Excited Thermoacoustic Instabilities for a Partially Premixed Swirl-Flame
Authors: Ćosić Bernhard , Moeck Jonas P. , Paschereit Christian Oliver
Published: November 2013

The prediction of the limit-cycle amplitude of thermoacoustically unstable practical gas turbine combustion systems remains a challenge for the gas turbine industry. The present study uses an experimentally obtained Flame Describing Function (FDF) for the determination of the thermoacoustic oscillation frequency and amplitude. In contrast to other studies, which investigated perfectly premixed laminar or marginally turbulent flames, this study deals with a highly turbulent swirl flame with spatial and temporal fuel–air unmixedness in an order of practical interest. A partially premixed swirl-stabilized flame is investigated at a Reynolds number of approximately 35 000. The Multi-Microphone-Method is used to determine the amplitude dependent transfer function of the flame as well as the transfer function of the burner and the acoustic response of the boundary conditions. The results are compared to OH* chemiluminescence measurements, which show a significant deviation in terms of the flame transfer function gain due to equivalence ratio fluctuations. The measured transfer functions are incorporated into a thermoacoustic modeling framework to determine frequency and amplitude of the self-excited limit cycle oscillation. Measurements were made for various lengths of the exhaust gas tube to verify the results for different frequencies and amplitudes. Good agreement is found for the entire range of combustor lengths investigated. The error between model and experimental results is thoroughly assessed.
Numerical and Experimental Investigation of Tangential Endwall Contoured Blades in a 2-Stage Turbine
Authors: Schwab Stephan , Wendland Dominik , Wirsum Manfred
Published: November 2013

This paper deals with the results of numerical and experimental investigations of tangential endwall contoured (TEWC) blades. The contouring is restricted to the blade passage and is implemented on the root and the shrouds for all blade rows. The investigated results of the new blade design have been compared to a reference blade design, which differs only in terms of the contouring. For this reason, the differences of the flow conditions can solely be attributed to the endwall contouring. All investigations have been carried out at different blade loadings in order to determine the potential improvement of the blading with respect to the efficiency.

The analysis has emphasized an efficiency improvement for the design point and an efficiency decrease for high blade loading. The under- and overturning are considered by means of the angle distributions behind the stages and serve as an indicator for the losses caused by the passage vortex. An attenuation of the passage vortex in the casing area resulting from the load relief in the casing-sided area can be observed. The contouring in the hub-area however leads to a higher development of the horseshoe vortex at high blade loading.
The Optimal Distribution of Pin Fins for Blade Tip Cap Underside Cooling
Authors: Ledezma Gustavo A. , Bunker Ronald S.
Published: November 2013

This article presents a geometric optimization study to maximize the total heat transfer rate between an array of discrete pin fins and the surrounding serpentine cooling flow. The fins are installed on the tip cap underside of a High Pressure Turbine blade model. The study has three parts. In the first, the numerical model is validated against experimental data obtained with liquid crystal thermography. In the second part, the heat and fluid flow performance of the pin fin assembly is simulated numerically, using RANS turbulence models in the range 25,000 < Re < 100,000 and Pr ∼ 0.7. The effect of varying the spacing and the tip cap boundary condition is investigated. In the last part of the study it is shown that the optimal spacing between the pin fins can be correlated following the same theoretical arguments derived in previous investigations that used simpler geometries.
A Novel Coal Based Cogeneration System for Substitute Natural Gas and Power With CO2 Capture and Moderate Recycle of the Chemical Unconverted Gas
Authors: Li Sheng , Jin Hongguang , Gao Lin
Published: November 2013

Cogeneration of substitute natural gas (SNG) and power from coal efficiently and CO2 capture with low energy penalty during coal utilization are very important technical paths to clean coal technologies for China which is rich in coal but lack of natural gas resources. This paper integrates a novel coal based cogeneration system with CO2 capture for SNG and power, and presents the energetic and exergy analysis based on the thermodynamic formulas and the use of ASPEN PLUS 11.0. In the novel system, instead of separation from the gas before synthesis traditionally, CO2 will be removed from the unconverted gas after synthesis, whose concentration can reach as high as 55% before separation and is much higher than 30% in traditional SNG production system. And by moderate recycle instead of full recycle of chemical unconverted gas back into SNG synthesis, the sharp increase in energy consumption for SNG synthesis with conversion ratios will be avoided, and by using part of the chemical unconverted gas, power is cogenerated efficiently. Thermodynamic analysis shows that the benefit from both systematic integration and high CO2 concentration makes the system have good efficiency and low energy penalty for CO2 capture. The overall efficiency of the system ranges from 53%–62% at different recycle ratios. Compared to traditional single production systems (IGCC with CO2 capture for power, traditional SNG system for SNG production), the energy saving ratio (ESR) of the novel system is 16%–21%. And compared to IGCC and traditional SNG system, the energy saving benefit from cogeneration can even offset the energy consumption for CO2 separation and realize zero energy penalties for CO2 capture systematically. Sensitivity analysis hints that an optimized recycle ratio of unconverted gas and chemicals to power output ratio (CPOR) can maximize system performance and minimize the energy penalty for CO2 capture.
Effect of Change in Fuel Compositions and Heating Value on Ignition and Performance for Siemens SGT-400 Dry Low Emission Combustion System
Authors: Liu Kexin , Martin Pete , Sanderson Victoria , Hubbard Phill
Published: November 2013

The influence of changes in fuel composition and heating value on the performance of an industrial gas turbine combustor was investigated. The combustor tested was a single cannular combustor for Siemens SGT-400 13.4 MW dry low emission (DLE) engine. Ignition, engine starting, emissions, combustion dynamics and flash back through burner metal temperature monitoring were among the parameters investigated to evaluate the impact of fuel flexibility on combustor performance.

Lean ignition and extinction limits were measured for three fuels with different heat values in term of Wobbe Index (WI): 25, 28.9 and 45 MJ/Sm3 (natural gas). The test results show that the air fuel ratio (AFR) at lean ignition/extinction limits decreases and the margin between the two limits tends to be smaller as fuel heat value decreases. Engine start tests were also performed with a lower heating value fuel and results were found to be comparable to those for engine starting with natural gas.

The combustor was further tested in a high pressure air facility at real engine operating conditions with different fuels covering WIs from 17.5 to 70 MJ/Sm3. The variation in fuel composition and heating value was achieved in a gas mixing plant by blending natural gas with CO2, CO, N2 and H2 (for the fuel with WI lower than natural gas) and C3H8 (for the fuel with WI higher than natural gas).

Test results show that a benefit in NOx reduction can be seen for the lower WI fuels without H2 presence in the fuel and there are no adverse impacts on combustor performance except for the requirement of higher fuel supply pressure, however, this can be easily resolved by minor modification through the fuel injection design.

Test results for the H2 enriched and higher WI fuels show that NOx, combustion dynamics and flash back have been adversely affected and major change in burner design is required. For the H2 enriched fuel, the effect of CO and H2 on combustor performance was also investigated for the fuels having a fixed WI of 29 MJ/Sm3. It is found that H2 dominates the adverse impact on combustor performance. The chemical kinetic study shows that H2 has significant effect on flame speed change and CO has significant effect on flame temperature change.

Although the tests were performed on the Siemens SGT-400 combustion system, the results provide general guidance for the challenge of industrial gas turbine burner design for fuel flexibility.
The Effect of Surface Roughness on Efficiency of Low Pressure Turbines
Authors: Vázquez Raúl , Torre Diego
Published: November 2013

The effect of surface roughness on efficiency of low pressure turbines (LPT) was investigated experimentally in a multistage turbine high-speed rig. The rig consisted of three stages of a state-of-the-art LPT. The stages were characterized by a very high wall-slope angle, reverse cut-off design, very high lift and very high aspect ratio airfoils.

Two sets of airfoils (both stators and rotors) were tested. The first set was made of airfoils with a roughness size of 0.7 μm Ra (25–35×10−5 ks/Cm), which was representative of LPT polished airfoils. The surface finish for the second set of airfoils was 1.8 μm Ra for blades and 2.5 μm Ra for stators (approximately 90×10−5 in terms of ks/Cm for both stators and blades). The resulting roughness of this set was representative of “as-cast” airfoils of low pressure turbines.

The airfoil geometries, velocity triangles, leading and trailing edge locations and flowpath were maintained between both sets. They were tested with the same instrumentation and at the same operating conditions with the intention of determining the isolated impact of the surface roughness on the overall efficiency. The turbine characteristics: sensitivity to speed, specific work, Reynolds number and purge flows were obtained for both sets.

The comparison of the results suggests that the efficiency and capacity of both types of airfoils exhibit the same behaviour. No significant differences in the results can be distinguished for the range of operating conditions of this study.

The results agree with previous studies of distributed roughness in turbines: the use of as-cast rough airfoils in some low pressure turbines at high altitude does not introduce additional pressure losses.
Early Detection of Boiler Leakage in a Combined Cycle Power Plant Using an Auto Associative Kernel Regression Model
Authors: Jeffries Brien , Hines J. Wesley , Klein Albert , Palmé Thomas , Bayère Romain
Published: November 2013

This paper presents the results of applying a data-driven condition-based monitoring system for the fault detection of a boiler leakage in a Combined Cycle Power Plant (CCPP). An auto associative kernel regression model is developed using normal process data and tested with faulted data to determine the earliest warning of the boiler leakage. Automatic variable grouping, which uses the linear correlations among the available thirty sensors, is employed to obtain optimal groupings to be used in model development. Several models were developed, optimized and compared. A logic test was used for fault detection and this test produced alarms in the region were the leak was later confirmed to have occurred. Comparison of these results with those of a physics-based analysis also confirmed the accuracy of the models in the early detection of the leakage.
Analysis and Modelling of Entropy Modes in a Realistic Aeronautical Gas Turbine
Authors: Motheau Emmanuel , Nicoud Franck , Mery Yoann , Poinsot Thierry
Published: November 2013

A combustion instability in a combustor typical of aero-engines is analyzed and modeled thanks to a low order Helmholtz solver. A Dynamic Mode Decomposition (DMD) is first applied to the Large Eddy Simulation (LES) database. The mode with the highest amplitude shares the same frequency of oscillation as the experiment (approx. 350 Hz) and it shows the presence of large entropy spots generated within the combustion chamber and convected down to the exit nozzle. The lowest purely acoustic mode being in the range 650–700 Hz, it is postulated that the instability observed around 350 Hz stems from a mixed entropy/acoustic mode where the acoustic generation associated with the entropy spots being convected throughout the choked nozzle plays a key role. A Delayed Entropy Coupled Boundary Condition is then derived in order to account for this interaction in the framework of a Helmholtz solver where the baseline flow is assumed at rest. When fed with appropriate transfer functions to model the entropy generation and convection from the flame to the exit, the Helmholtz solver proves able to predict the presence of an unstable mode around 350 Hz, in agreement with both the LES and the experiments. This finding supports the idea that the instability observed in the combustor is indeed driven by the entropy/acoustic coupling.
Misconceptions in Test Accuracy: Confidence Intervals vs. Statistical Power — An Engine Inlet Example
Authors: Kidman David , Stevens Craig , Remund Todd , Poulson Robert , Kitto William , Vining Charles
Published: November 2013

The United States Air Force (USAF) is continually looking for ways to improve test and evaluation techniques to ensure systems meet military requirements. Since 1997, Air Combat Command (ACC) has been successfully using Design of Experiments (DOE) to construct and analyze operational test efforts. This paper highlights recent Air Force Materiel Command (AFMC) efforts to pursue statistically defensible test techniques to aid developmental test efforts.

Defensible testing is a statistical approach which encompasses DOE but also emphasizes the need for better test planning by insisting on understanding the system under test, by requiring clear and achievable test objectives, by ensuring system performance is measurable, and by requiring that instrumentation accuracy and uncertainty are well understood and by estimating risk in test planning and evaluations which sometimes require confidence and power calculations.

This paper highlights the Air Force Flight Test Center’s (AFFTC) first steps to improve aircraft propulsion system developmental test and evaluation (T&E) through the implementation of statistically defensible test techniques. Specifically, this paper provides insight into test accuracy. Engineers typically misuse terminology to specify test accuracy (error, precision, uncertainty, confidence intervals, etc…). This paper will present a case study in which the engineer specifies test accuracy requirements in terms of margin of error using 95-percent confidence intervals (CI’s). However, statisticians recommend using “Statistical Power” to ensure desired accuracy is achieved. Which is best to achieve test goals (CI’s or Power)? This paper will provide case study based on results from a recent aircraft engine inlet upgrade and provide a comparison between margin of error (confidence intervals) and statistical power results.

A case will be made that statistical power is more mathematically rigorous than typical margin of error approaches and should be used to ensure test accuracy requirements are met.
Multi-Field Coupling Analysis on the Film-Cooling of a Turbine Guide Vane
Authors: Wang Zhan , Liu Jian-Jun , Zhang Chao
Published: November 2013

Multi-field coupling method is used to assess the film-cooling properties of a turbine guide vane. The creep strain is used to evaluate the film-cooling validness, in order to take into account the effects of both temperature and thermal stress. Because of the high temperature gradients, thermal stress is much higher than the aerodynamic stress in a guide vane. It is found that large creep strain may be generated where the cooling holes locate, especially near the shower-head and upper endwall. For the shower-head film cooling, three types of holes (cylindrical, fan-shaped, double-jet) were studied. The results showed that fan-shaped and double-jet holes were suitable for the cooling of the shower-head of the guide vane. For the endwall, adding more cooling holes could reduce the area of high temperature and also reduce the creep strain.
Micro Gas-Turbine Design for Small-Scale Hybrid Solar Power Plants
Authors: Aichmayer Lukas , Spelling James , Laumert Björn , Fransson Torsten
Published: November 2013

Hybrid solar micro gas-turbines are a promising technology for supplying controllable low-carbon electricity in off-grid regions. A thermoeconomic model of three different hybrid micro gas-turbine power plant layouts has been developed, allowing their environmental and economic performance to be analyzed. In terms of receiver design, it was shown that the pressure drop is a key criterion. However, for recuperated layouts the combined pressure drop of the recuperator and receiver is more important. The internally-fired recuperated micro gas-turbine was shown to be the most promising solution of the three configurations evaluated, in terms of both electricity costs and carbon emissions. Compared to competing diesel generators, the electricity costs from hybrid solar units are between 10% and 43% lower, while specific CO2 emissions are reduced by 20–35%.
Wall Temperature Effects on Heat Transfer Coefficient
Authors: Maffulli Roberto , He Li
Published: November 2013

Developments of High Pressure Turbine (HPT) blades and vanes are particularly affected by the accuracy and consistency in heat transfer prediction techniques. The conventional wisdom in heat transfer analysis considers that aerodynamics fully determines Heat Transfer Coefficient (HTC) distribution along the blade surface, so that wall temperature should have no influence on HTC. The effect of the wall temperature on the heat transfer coefficient has been rarely studied, although there have been some rather scattered correlations regarding the influence of the wall-inflow temperature ratio on HTC, largely based on simple geometry configurations. There seems to be a need to answer two related questions:

a) to what extent the conventional wisdom is valid, in particular for a transonic HPT blading?

b) what is a consistent way by which the HTC should be worked out in CFD (as well as in experiment)?

In this paper, computational analyses are carried out on the effects of wall thermal boundary condition on external HTC for a 2D Nozzle Guide Vane (NGV) profile. The study is performed by using Fluent® commercial Reynolds-Averaged Navier Stokes Equations solver. Further computations are also made using a coupled solid-fluid Conjugate Heat Transfer (CHT) method with an internally cooled blade. The present results show a strong dependence of HTC on wall temperature, far above that predicted by using the existing correlations, highlighting the importance of upstream boundary layer history on the HTC distribution. Influence of the wall temperature on the trailing edge shock position has been also observed. Based on the results found, a new method is proposed, allowing to model the HTC dependence on wall temperature with much improved accuracy as demonstrated.
Modelling of a Turbulent Jet in a Gas Crossflow
Authors: Moffat Dominic L. , Burluka Alexey A.
Published: November 2013

The first part of this work presents a comparison of predictions obtained with several two-equation type RANS turbulence models commonly used in industry against experimental data obtained by Whitelaw et al [1]. All examined models yield a relatively poor match in the flow region very close to the wall; agreement with the measurements improves significantly when moving further away from the wall. This concerns both the internal normal stress profiles and the average velocity profiles, the latter show improved prediction of the recirculation zone area when moving further into the main stream. Downstream behaviour for both models shows an excellent match more than 6 diameters away from the jet inlet, defined as the region after which the flow essentially resumes its normal duct behaviour[1].

Expanding upon these RANS results, another series of simulations using LES modelling with the standard Smagorinsky SGS model was conducted using the same grid and compared to the RANS-based results. Although performance in the most complex flow areas was slightly improved over RANS, this was at the cost of an increase of computation time by almost a factor of 6.

The next stage involved developing a code based on the model for two-phase flow described in [2] to predict the atomisation pattern for a non-vaporising (or “cold”) flow based on the parameters of the previous simulations. This model implements transport equations for the liquid mass fraction and the average surface area per unit mass along with an equation for average density; resulting in an entirely Eulerian model which can be used to predict atomisation from first principles. Current work consists in development of additional source terms describing vaporisation in a strongly turbulent environment and further coupling with a combustion model applicable to the combustion chamber of an industrial gas turbine.
An Advanced Usage of Meanline Loss Systems for Axial Turbine Design Optimisation
Authors: Zhdanov Ivan , Staudacher Stephan , Falaleev Sergey
Published: November 2013

A comprehensive axial turbine framework model has been developed at the Institute of Aircraft Propulsion Systems, University of Stuttgart. It discovers the principles of a meanline optimisation and shows its advantages for quick prediction of optimal meanline parameters considering manufacturing, mechanical and aerodynamic requirements. The framework model can incorporate different loss correlations and compare their results for one and the same multi-dimensional design parameter space. A special attention is paid to the influence of loss correlations on optimal values of meanline parameters. It is shown that, although all loss correlation has their own global optimum of turbine performance in the multi-dimensional design parameter space, they are going to coincide if the requirements addressed to a turbine are considered and the turbine design constraints, e.g. a specified rotational speed, inlet diameter and etc., are applied. Thus, the more constraints in the design parameter space exist, the lower the impact of a loss correlation on optimal values of meanline parameters.
Sensitivity of the Numerical Prediction of Flow in the LIMOUSINE Combustor on the Chosen Mesh and Turbulent Combustion Model
Authors: Shahi Mina , Kok Jim B. W. , Pozarlik Artur K. , Roman Casado J. C. , Sponfeldner Thomas
Published: November 2013

The objective of this study is to investigate the sensitivity and accuracy of the combustible flow field prediction for the LIMOUSINE combustor with regards to choices in computational mesh and turbulent combustion model. The LIMOUSINE combustor is a partially premixed bluff body stabilized natural gas combustor designed to operate at 40–80 kW and atmospheric pressure and used to study combustion instabilities. The transient simulation of a turbulent combusting flow with the purpose to study thermo-acoustic instabilities is a very time consuming process. For that reason the meshing approach leading to accurate numerical prediction, known sensitivity, and reduced amount of mesh elements is important. Since the numerical dissipation (and dispersion) is highly dependent on, and affected by, the geometrical mesh quality, it is of high importance to control the mesh distribution and element size across the numerical model. Typically, the structural mesh topology allows using much less grid elements compared to the unstructured grid, however an unstructured mesh is favorable for flows in complex geometries. To explore computational stability and accuracy, the numerical dissipation of the cold flow with mixing of fuel and air is studied first in the absence of the combustion process. Thereafter the studies are extended to combustible flows using standard available ANSYS-CFX combustion models. To validate the predicted variable fields of the combustor’s transient reactive flows, the numerical results for dynamic pressure and temperature variations, resolved under structured and unstructured mesh conditions, are compared with experimental data. The obtained results show minor dependence on the used mesh in the velocity and pressure profiles of the investigated grids under non-reacting conditions. More significant differences are observed in the mixing behavior of air and fuel flows. Here the numerical dissipation of the (unstructured) tetrahedral mesh topology is higher than in the case of the (structured) hexahedral mesh. For that reason, the combusting flow resolved with the use of the hexahedral mesh presents better agreement with experimental data and demands less computational effort. Finally in the paper the performance of the combustion model for reacting flow as a function of mesh configuration is presented, and the main issues of the applied combustion modeling are reviewed.
An Immersed Mesh Block (IMB) Approach for Conjugate Heat Transfer Predictions
Authors: Lad B. , He L.
Published: November 2013

Aerothermnal design capability for cooled high pressure turbines depends on resolving complex physical processes such as coolant mixing, coupled fluid-solid convection-conduction heat transfer, and their interactions. This paper presents the development of the generalised Immersed Mesh Block 2 (IMB2) method, which allows high resolution predictions of all these processes to be conducted for a fully cooled turbine stage within a couple of days. The method consists of creating high density meshes of cooling holes to capture the high flow gradients in the fluid domain and separately, generating corresponding meshes for the local metal layer with high temperature gradient. These can then be inserted rapidly into a host turbine domain for conjugate heat transfer as immersed mesh blocks for fluids (IMBf) and metals (IMBm). In this way, conjugate heat transfer meshes of entire rows of cooling holes can be generated and inserted into a host mesh within minutes. The composite domain is then solved with simultaneous coupling between all the fluid and metal IMBs, as well as the host mesh. The paper presents the methodology of this approach and demonstrates its application to a transonic, fully cooled nozzle guide vane.
Gasdynamic Design Numerical Optimization of High-Loaded Subsonic Stages for Low Pressure Steam Turbine
Authors: Dolganov Aleksei , Nekrasov Alexander
Published: November 2013

Modern large capacity steam turbine for fossil power plants should have a high efficiency to be competitive in today’s tough market. It should be compact, with a smaller mass for reducing cost. In these circumstances, an effective solution is to create a large capacity steam turbine that consists of integrated high-intermediate-pressure turbine (HIPT) and one low-pressure turbine (LPT). Greater heat drop as compared to a conventional turbine shall be provided in LPT of such steam turbine. With this rather high efficiency of the low-pressure turbine should be provided. The performance of LPT depends not only on the efficiency of trans- and supersonic stages, but also on the efficiency of subsonic upstream stages. At a time when the overall heat drop in the low-pressure turbine is increased, role of the upstream subsonic stages also increases, provided that the design of stages L-0 and L-1 is maintained. This paper presents results of numerical simulation of an optimized subsonic stages section for a new low-pressure steam turbine. Simulation results of a conventional subsonic stages section are presented for comparison. Stages of the optimized subsonic section have a number of features: increased disposable heat drop, enlarged relative pitch, spline representation of sections of blade profiles, 3D airfoil design. The comparison of normalized integral basic characteristics, plots of the main parameters on the blade height, diagrams of the normalized pressure in individual cylindrical sections is given for optimized and conventional cases.
ETF40B 3rd Vane Field Investigation: Root Cause and Corrective Action
Authors: Slogar Gerrick , Prus Gary , Canilang Benjamin
Published: November 2013

Results from an engineering investigation, including findings, root cause and corrective action of an ETF40B compressor incident, are presented in this paper. Vericor’s ETF40B is used to power US NAVY Landing Craft Air Cushion (LCAC) vehicles that have undergone the Service Life Extension Program (SLEP). This paper discusses the initial review of an engine incident, the results of the engineering investigation that led to identifying root cause and the successful validation testing providing fleet corrective action. This paper will present the history of the investigation, the metallurgical analysis findings, the results of finite element stress analysis and investigative testing performed on the vane. The paper will conclude with the testing conducted to verify the design solution and how the final field and production compressor changes were incorporated.
Development of an Experimental Test Facility for Investigating Mist/Air Film Cooling Application in Gas Turbine Airfoils
Authors: Wang Ting , Zhao Lei
Published: November 2013

Film cooling is a cooling technique widely used in high-performance gas turbines to protect the turbine airfoils from being damaged by hot flue gases. Motivated by the need to further improve the turbine hot section cooling performance, a new cooling scheme, mist/air film cooling is investigated. A small amount of tiny water droplets with an average diameter about 7 μm (mist) is injected into the cooling air to enhance the cooling performance. One key feature in understanding mist cooling is the ability to capture droplet information. This paper presents the experimental facility and instrumentation of a mist/air film cooling study with both heat transfer and droplet measurements.

A wind tunnel system and test facilities are built. A Phase Doppler Particle Analyzer (PDPA) system is employed to measure the two-phase flow characteristics, including droplet size, droplet dynamics, velocity, and turbulence. Infrared camera and thermocouples are both used for temperature measurements. An extensive uncertainty analysis is performed to assist in identifying large uncertainty sources and planning for experimental procedure.

It was found during the experiment design process that resolving the mist agglomeration problem is the key in successfully generating a well-controlled mist/air mixture and reducing experimental uncertainties. The test apparatus has proven to serve the purpose well to investigate mist/air film cooling with both heat transfer and droplet measurements. Selected experimental data is presented.
Reducing the Number of Turbine Starts in Concentrating Solar Power Plants Through the Integration of Thermal Energy Storage
Authors: Guédez Rafael , Spelling James , Laumert Björn , Fransson Torsten
Published: November 2013

The operation of steam turbine units in solar thermal power plants is very different than in conventional base-load plants. Due to the variability of the solar resource, much higher frequencies of plant start-ups are encountered. This study provides an insight to the influence of thermal energy storage integration on the typical cycling operation of solar thermal power plants. It is demonstrated that the integration of storage leads to significant reductions in the annual number of turbine starts and is thus beneficial to the turbine lifetime. At the same time, the effects of storage integration on the electricity costs are analyzed to ensure that the designs remain economically competitive. Large storage capacities, can allow the plant to be shifted from a daily starting regime to one where less than 20 plant starts occur annually. Additionally, the concept of equivalent operating hours is used to further analyze the direct impact of storage integration on the maintenance planning of the turbine units.
Conditions in Advanced Turbines for IGCC Power Plants With Carbon Capture
Authors: White Briggs M. , Ames Robin W. , Burke Patcharin
Published: November 2013

The anticipated conditions in advanced turbines for Integrated Gasification Combined Cycle (IGCC) power plants with Carbon Capture (CC) are discussed to provide researchers with accurate boundary conditions to conduct targeted research and development activities. Information was collected through reviews of existing IGCC plant conditions, system studies, permitting requirements, and industry feedback. Anticipated bulk gas phase characteristics are provided, including temperatures, pressures, mass flow rates, and compositions. Particulate loadings and sizing information are also presented; however, compositional information is limited.
Influence of Large Wake Disturbances Shed From the Combustor Wall on the Leading Edge Film Cooling
Authors: Mazzoni Cosimo Maria , Klostermeier Christian , Rosic Budimir
Published: November 2013

The first vane leading edge film cooling is challenging because of the highest thermal load and the complex flow interaction between the hot mainstream gas and the coolant flow. This interaction varies significantly from the stagnation region to the regions of high curvature and acceleration further downstream. Additionally, in industrial gas turbines with multiple combustor chambers around the annulus the first vane leading edges may also be exposed to large wake disturbances shed from the upstream combustor walls.

The influence of these vortical structures on the first vane leading edge film cooling is numerically analysed in this paper. In order to assess the capabilities of the flow solver TBLOCK to simulate these complex interactions an experimental test case is modelled numerically. The test case is available in the open literature and consists of a cylindrical leading edge and two rows of film cooling holes representative of industrial practice. A LES turbulence modelling strategy with WALE sub-grid scale (SGS) model is applied and compared against experimental results. Based on this validation it is decided to analyse also the wake–leading edge interaction, dominated by large scale unsteady vortical structures, using the same WALE sub-grid scale LES model. The initial flow domain with the cylindrical leading edge and cooling holes is extended to incorporate the effect of the combustor wall, which is modelled as a flat plate with a square trailing edge. The location and the size of the plate are scaled to be representative of industrial practice: the plate is located upstream from the leading edge at a distance twice the leading edge diameter, and the thickness of the plate is one half of the leading edge diameter. Two different clockwise positions of the vertical combustor wall model were investigated and compared with the datum configuration: the former where the axis of the plate and the leading edge are aligned (central wake location), the latter with the combustor wall circumferentially shifted up by a quarter of the leading edge diameter (circumferentially shifted wake location).

Numerical predictions show that the shed vortices from the combustor wall trailing edge have a highly detrimental effect on the leading edge film cooling by periodically removing the coolant flow from the leading edge surface. This results in an increased unsteady thermal load. These negative effects are less significant in the case of circumferentially shifted wake, due to the combined action of both shed vortices.
Enhancement of Impinging Atomization by Microjet Injection
Authors: Inoue Chihiro , Watanabe Toshinori , Himeno Takehiro , Uzawa Seiji
Published: November 2013

With increasing focus on environmental effects and the need for fuel diversity in gas turbines, good liquid atomization is increasingly important. It is known that impinging atomization is able to produce fine drops by impingement of fast liquid jets. However, the atomization characteristics deteriorate at lower injection velocities. In this study, for improving atomization characteristics under a wide range of injection velocity, an effective technique is verified utilizing a small amount of gas (microjet) injection. The microjet is supplied from a pressurized reservoir independent of the liquid supply system, and it is injected from the center of the liquid nozzles toward the impingement point. To clarify the flow field and the mechanism of the effectiveness, experimental visualizations and drop size measurements are carried out. It is found that atomization is remarkably promoted when the dynamic pressure of microjet overcomes that of the liquid at the impingement point. By the microjet injection with only 1% of liquid mass flow rate, Sauter mean diameter (SMD) becomes one-tenth of the original SMD. In addition, optimized atomization efficiency is successfully achieved when the dynamic pressure of the microjet is two times that of the liquid at the impingement point.
Conjugate Heat Transfer Modeling of a Film-Cooled, Flat-Plate Test Specimen in a Gas Turbine Aerothermal Test Facility
Authors: Sidwell T. G. , Lawson S. A. , Straub D. L. , Casleton K. H. , Beer S.
Published: November 2013

The aerothermal test facility at the National Energy Technology Laboratory (NETL) provides experimental data at realistic gas turbine conditions to enable the development of advanced film cooling strategies for future gas turbine components. To complement ongoing experimental studies, Fluent computational fluid dynamics (CFD) models have been developed to provide a framework for comparison of cooling strategies and to provide fundamental understanding of the fluid dynamic and conjugate heat transfer (CHT) processes occurring in the experiments.

The results of a parametric study of the effects of mesh density, near-wall refinement, wall treatment, turbulence model and gradient discretization order on the CHT predictions are presented, and the simulation results are compared to experimental data. A flat plate test specimen with a single row of laidback fan-shaped film cooling holes was modeled at a process pressure of 3 bar, a process gas flow rate (m) of 0.325 kg/s (Re ≈ 100,000) and a blowing ratio (M) of 2.75. Three polyhedral mesh cases and three turbulence models (Realizable k-ε, SST k-ω and RSM Stress-ω) were implemented with enhanced wall treatment (EWT) and 1st-order and 2nd-order gradient discretization.

The results show that the choice of turbulence model will have little effect on the results when utilizing the finest mesh case and 2nd-order discretization. It was also shown that the SST k-ω turbulence model cases showed minimal mesh sensitivity with 2nd-order discretization, while the Re k-ε turbulence model cases were more sensitive to mesh density and near-wall refinement. The results thus indicate that the SST k-ω turbulence model can predict the convective heat transfer adequately with a relatively coarse mesh, which will save computational resources for later inclusion of radiative heat transfer effects to provide comprehensive CHT predictions.
Effects of Both Axial Gap and Blade Count Ratio on the Forced Response of a Steam Turbine Stage
Authors: Chen Tie , Rogerson John , Patel Kush
Published: November 2013

Rotating blades of steam turbines are subjected to unsteady forces due to the presence of both wake and potential field from the adjacent stationary blade rows. The combined effects of both axial gap and blade count ratio on the unsteady forces have been demonstrated on a steam turbine stage. This study shows their effects on the forced response. Further investigations show their effects on stimulus, aero damping and frequency shift. This study uses a one-way coupling dynamic stress prediction tool, which integrates an in-house Computational Fluid Dynamic solver TF3D-VIB with a commercial Finite Element solver ABAQUS.
Optimization of Micro-Textured Surfaces for Turbine Vane Impingement Cooling
Authors: Jacobs Justin , Tripp Joe , Underwood David , Lengsfeld Corinne
Published: November 2013

Gas turbine engines are challenged to operate at higher efficiencies, leading to turbine inlet temperatures that exceed turbine material limits. Increased internal cooling efficiency enables higher temperature operation, reduces cooling air injection into the core flow, and mitigates performance penalties from thermal mixing and total pressure loss. Micro Cooling Concepts has developed a turbine vane cooling concept that provides enhanced internal impingement cooling effectiveness via the use of micro-textured impingement surfaces (i.e., grooves and fins). The current effort employs computational models, in conjunction with optimization techniques, to explore the optimal design of these micro-textured surfaces. A computational fluid dynamics model of the vane leading edge was utilized to compute the flow in the vane interior and the temperature distribution in the vane material. A gradient-based optimization routine, implemented in Matlab, varied geometric parameters in an independent manner to minimize the maximum metal temperature in the vane material volume. Four separate design spaces were explored: grooves and fins (both shrouded and unshrouded). It was determined that the shrouded fins and fin design outperformed all others. The maximum external convective free stream temperature obtained was 2600 K while the maximum internal vane temperature remained below 1219 K.
Experimental and Numerical Investigations of Flowpath Profiling on Secondary Flow Losses in a Turbine Control Stage
Authors: Moser Nils , Steinhoff Peter , Joos Franz
Published: November 2013

The numerically and experimentally investigated industrial steam turbine control stage is derived from a real design. Due to the production process and costs of the guide vanes for control stages of steam turbines the flowpath profiling is rotationally symmetric. However the combination of the two-dimensional shroud contour and the flow deflection in the guide vane results in a fully three-dimensional end wall contour having a strong influence on the secondary flow features in the turbine control stage.

To obtain an improved profile for the nozzle shroud the reduction of the total pressure loss over the guide vanes is taken as an optimization criterion. The three-dimensional contour generates a diffuser flowpath between the suction and the pressure side of two guide vanes perpendicular to the main flow direction. This diffuser geometry affects the pressure distribution over the guide vane and therefore the formation mechanisms of secondary flows. For the experimental and numerical investigations a baseline shroud design and two additional profiled contours are analyzed in detail.

The control stage test rig is operated with air and is capable to represent a wide range of operating conditions. The measurements show a considerable increase of the stage efficiency and power output. The effect of the flowpath profiling on the pressure distribution over the guide vane is clearly proved.
A Particle Image Velocimetry-Based Investigation of the Flow Field in an Oblique Jet Impingement Configuration
Authors: Schulz Sebastian , Schueren Simon , von Wolfersdorf Jens
Published: November 2013

Impinging jets have become an indispensable measure for cooling applications in gas turbine technology. The present study seeks to unfold the flow field dynamics inside an enigine-relevant cooling passage of trapezoidal cross-section. The investigated geometry produces a highly complex flow field which was investigated employing Particle Image Velocimetry (PIV). The experiments were accompanied by numerical simulations solving the RANS equations with FLUENT using the low-Re k-ω-SST turbulence model. Additionally, time-resolved pressure measurements were performed utilizing Kulite pressure transducers. The spectral analysis of the transient pressure signal in conjunction with a Proper Orthogonal Decomposition (POD) analysis of the PIV data allows a detailed insight into the effects of geometric constraints on the fluid dynamic processes inside the geometry.

The results are presented for a jet Reynolds number of 45,000 and display a qualitatively fair agreement between the experiments and numerical simulations. Nevertheless, the simulations predict flow features in particular regions of the geometry that are absent in the experiments. Despite the lack of conspicuous high energy modes, the flow was well suited for a POD analysis. Depending on the considered PIV plane, it could be shown that up to 25% of the flow field’s total turbulent energy are contained in the first ten POD modes. Additionally, using the first 20 to 60 POD modes sufficed to reconstruct the flow fields with its governing features.