bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pump Grooved Seals: A CFD Approach to Improve Bulk-Flow Model Predictions
Authors: Wu Tingcheng , San Andrés Luis 
Published: November 2019

Abstract
In multiple stage centrifugal pumps, balance pistons, often comprising a grooved annular seal, equilibrate the full pressure rise across the pump. Grooves in the stator break the evolution of fluid swirl and increase mechanical energy dissipation; hence, a grooved seal offers a lesser leakage and lower cross-coupled stiffness than a similar size uniform clearance seal. To date bulk-flow models (BFMs) expediently predict leakage and rotor dynamic force coefficients of grooved seals; however, they lack accuracy for any other geometry besides rectangular. Note scalloped and triangular (serrated) groove seals are not uncommon. In these cases, computational fluid dynamics (CFD) models seals of complex shape to produce leakage and force coefficients. Alas CFD is not yet ready for routine engineer practice. Hence, an intermediate procedure presently takes an accurate two-dimensional (2D) CFD model of a smaller flow region, namely a single groove and adjacent land, to produce stator and rotor surface wall friction factors, expressed as functions of the Reynolds numbers, for integration into an existing BFM and ready prediction of seal leakage and force coefficients. The selected groove-land section is well within the seal length and far away from the effects of the inlet condition. The analysis takes three water lubricated seals with distinct groove shapes: rectangular, scalloped and triangular. Each seal, with length/diameter L/D = 0.4, has 44 grooves of shallow depth dg ∼ clearance Cr, and operates at a rotor speed equal to 5,588 rpm (78 m/s surface speed) and with a pressure drop of 14.9 MPa. The method validity is asserted when 2D (single groove-land) and 3D (whole seal) predictions for pressure and velocity fields are compared against each other. The CFD predictions, 2D and 3D, show the triangular groove seal has the largest leakage, 41% greater than the rectangular groove seal does, albeit producing the smallest cross-coupled stiffnesses and whirl frequency ratio. On the other hand, the triangular groove seal has the largest direct stiffness and damping coefficients. The scalloped groove seal shows similar rotordynamic force coefficients as the rectangular groove seal but leaks 13% more. For the three seal groove types, the modified BFM predicts leakage that is less than 6% away from that delivered by CFD, whereas the seal stiffnesses (both direct and cross-coupled) differ by 13%, the direct damping coefficients by 18%, and the added mass coefficients are within 30%. The procedure introduced extends the applicability of a BFM to predict the dynamic performance of grooved seals with distinctive shapes.
High Temperature Oxidation Lifetime Modeling of Thin-Walled Components
Authors: Pillai R. , Dryepondt S. , Pint B. A. 
Published: November 2019

Abstract
High temperature material solutions for future power generation applications require longer component lifetimes at higher temperatures to improve durability and efficiency. From a research and development point of view, the lifetimes are too long for experimental verification. Thus, accurate lifetime models are needed. Examples are provided where modeling is being applied to lifetime prediction of thin-walled NiCr wrought alloy components. Specific laboratory experiments have been conducted for alloy X at 900°–950°C in dry air and air with water vapor with cycle times from 1 to 500 h. Along with microstructure characterization, comparisons are made between experiment and model predictions. The eventual goal is to predict both oxidation and mechanical behavior.
Boundary Layer Flashback Prediction for Turbulent Premixed Jet Flames: Comparison of Two Models
Authors: Kalantari Alireza , Auwaijan Nicolas , McDonell Vincent 
Published: November 2019

Abstract
Lean-premixed combustion is commonly used in gas turbines to achieve low pollutant emissions, in particular nitrogen oxides. But use of hydrogen-rich fuels in premixed systems can potentially lead to flashback. Adding significant amounts of hydrogen to fuel mixtures substantially impacts the operating range of the combustor. Hence, to incorporate high hydrogen content fuels into gas turbine power generation systems, flashback limits need to be determined at relevant conditions. The present work compares two boundary layer flashback prediction methods developed for turbulent premixed jet flames. The Damköhler model was developed at University of California Irvine (UCI) and evaluated against flashback data from literature including actual engines. The second model was developed at Paul Scherrer Institut (PSI) using data obtained at gas turbine premixer conditions and is based on turbulent flame speed. Despite different overall approaches used, both models characterize flashback in terms of similar parameters. The Damköhler model takes into account the effect of thermal coupling and predicts flashback limits within a reasonable range. But the turbulent flame speed model provides a good agreement for a cooled burner, but shows less agreement for uncooled burner conditions. The impact of hydrogen addition (0 to 100% by volume) to methane or carbon monoxide is also investigated at different operating conditions and flashback prediction trends are consistent with the existing data at atmospheric pressure.
The Influence of Turbulence and Reynolds Number on Slot Film Cooling Over the Downstream Pressure Surface
Authors: Soma L. W. , Ames F. E. , Acharya S. 
Published: November 2019

Abstract
Pressure surface film cooling from discrete holes can often be challenging due to higher than optimum coolant to surface pressure ratios, effects of high levels of flow field turbulence, and the potential for clogging. Double wall cooling methods can be designed to collect spent cooling air and distribute the film cooling downstream through a slot. Incremental impingement is a new internal cooling method designed for cooling the leading edge region and pressure surface. Internally, incremental impingement includes high solidity pedestals to conduct heat and transmit thermal stresses due to temperature variations between cold and hot side surfaces. Subsequently, the flow is collected downstream from the last row of pedestals and discharged through a slot. Experimental and computational research from mesh slots, which have dense arrays of pedestals upstream from the discharge, and slots downstream from high solidity pedestal arrays have shown that turbulence and vorticity generated inside a film cooling plenum can have a significant impact on downstream film cooling. This impact of plenum flow disturbances is in addition to the film cooling dissipation caused by external flow field turbulence. Incremental impingement, in addition to high solidity pedestals, has impingement jets integrated behind the last row of pedestals which may cause further disruption to the film discharge and flow field interaction. The present measurements document the film cooling effectiveness distributions downstream from a slot located at 62% arc along the pressure surface of a vane. The plenum has been designed to include high solidity pedestals and impingement jets consistent with an incremental impingement geometry. Blowing ratios of 0.4, 0.7 and 1.0 have been investigated at vane exit chord Reynolds numbers of 500,000, 1,000,000 and 2,000,000 at density ratios a little over 1. These conditions have been run at 5 independent turbulence levels ranging from 0.7% to over 17%. The results provide a consistent picture of pressure surface slot film cooling downstream from incremental impingement.
Film Cooling of Compound Angle Upstream Sister Holes
Authors: Abd Alsalam Sana , Jubran Bassam 
Published: November 2019

Abstract
This study introduces a novel and simple strategy; compound angle upstream sister holes (CAUSH) to increase film cooling performance of the cylindrical hole by combining two techniques: Sister holes; (two small round holes placed upstream the primary hole) and compound angle hole. Whereas the upstream sister holes were injected at several compound angles β = 0°, 45°, 75°, and 90°, while the main hole was injected to the streamwise direction at 35° on a flat plate. FLUENT-ANSYS code was used to perform the simulation by solving the 3D Reynolds Averaged Navier-Stokes Equations. The capability of three types of k-ε turbulence modeling combined with the enhanced wall treatment is investigated to predict the film cooling performance of sister holes. A detailed computational analysis of the cooling performance of the (CAUSH) and the flow field was done at a density ratio equal to two (D.R = 2) and four blowing ratios M = 0.25, 0.5, 1.0 and 1.5 to predict the centerline and laterally averaged film cooling performance. The centerline effectiveness results showed that the highest cooling performance from the examined (CAUSH) was obtained at β = 0°, 45°, and 90° for low and high blowing ratio, the highest laterally averaged film cooling performance was captured at β = 0° and 90° for all tested blowing ratios. Also, the results indicated that the upstream sister hole with 90° compound angle holes has the best overall film cooling effectiveness while the worst performance is attained at β = 75°.
NOx Emissions Predictions for a Hydrogen Micromix Combustion System
Authors: Babazzi Giulia , Gauthier Pierre Q. , Agarwal Parash , McClure Jonathan , Sethi Vishal 
Published: November 2019

Abstract
Being free from carbon content, hydrogen has been considered as a promising candidate to reduce pollutant emissions in Gas Turbine Combustion Systems. Due to hydrogen’s significantly different burning characteristics, its implementation requires adjustments to the design philosophies of traditional combustion chambers. The micromix concept offers an alternative diffusive combustion injection system, improving the mixing characteristics without the risk associated with pre-mixing, thereby reducing the likelihood of hotspots forming.
The importance of turbulence-chemistry interaction modelling, particularly for highly diffusive flames such as hydrogen, has been widely addressed. A turbulence-chemistry interaction study on such a micromix injector was performed investigating the coupling between the Flamelet Generated Manifold (FGM) combustion model and different hydrogen reaction mechanisms. This methodology correctly reproduces the typical micromix micro-flame behaviour and the analysed mechanisms are shown to be in good agreement in terms of flow characteristics prediction.
A comparative study between two reduced order emissions prediction models was then carried out: a CFD post-processing technique for NOx emissions calculations and a hybrid CFD-CRN approach were explored. Due to the coupling between accurate turbulence-chemistry interaction modelling and the ability to handle detailed chemistry, the hybrid CFD-CRN approach gives valuable results with a modest computational cost and it could be used as an optimising tool during the injector geometry design process.
Involving Students in the Learning Process: Using Team Competition to Teach Gas Turbine Cycle Design
Authors: Van Treuren Kenneth 
Published: November 2019

Abstract
Active learning is an important part of modern engineering education. It directly engages students in the learning process, helping them think and creatively solve problems. Often this is done in the context of a team project involving group activities both inside and outside the classroom. Analysis and Design of Propulsion Systems is an elective course that has been a traditional lecture course at Baylor University, teaching gas turbine engines using cycle design. In an effort to involve the students more in the learning process, active learning modules were introduced to make the course more interactive.
The active learning modules involved assigning students into teams of four that were formed using the Comprehensive Assessment of Team Member Effectiveness (CATME) software. Each team was to operate as a commercial company which included picking a name, developing a logo, and writing a mission statement similar to actual commercial companies. The point of having each team become a commercial company was to foster competition. The companies were tasked to eventually design the lowest cost, most efficient high bypass turbofan engine to replace the existing engines on the B-52H bomber. Each company wrote a persuasive position paper on whether or not the B-52H should be re-engined and a Request for Proposal (RFP) for the re-engined B-52H.
Gas turbine cycle design occurred using a three part design project. The engine cycle of choice for this re-design was the high bypass turbofan. Phase one was a detailed mission analysis incorporating the requirements from the RFP and leading to the selection of a design point, the calculation of the required installed thrust for each leg (and consequently the uninstalled thrust for each leg), as well as an average uninstalled specific fuel consumption for the mission. On-design, the next phase in the design process, used an on-design analysis at the design point which resulted in a selection of a fan pressure ratio, an overall pressure ratio, and a bypass ratio. The last phase examined the chosen engine at off-design mission points and the final fuel was calculated using actual uninstalled specific fuel consumption values to assure the fuel reserve was met. All phases were incorporated into a final report.
To conclude the process, each team presented their engine as if they were a company seeking to sell their product to a customer. The customer, the professor, then picked an overall winner based on the information presented. Assessment of the course showed that the students appreciated the competitive environment giving them insight into how a gas turbine company might operate. In conclusion, the active learning modules and team competition with the design project were effective in challenging and exciting the students about the design of gas turbine engines. The company context for teams prepares students for what to expect should they work in the gas turbine industry.
Multi-Objective Design of a Transonic Turbocharger Compressor With Reduced Noise and Increased Efficiency
Authors: Wang Peng , Zangeneh Mehrdad , Heyes Francis , Roach Paul 
Published: November 2019

Abstract
In marine diesel engines, transonic centrifugal compressors are widely used due to their capabilities to: 1) downsize engines by increasing output power; 2) cause less fuel consumption; 3) enhance the combustion efficiency. Apart from the traditional requirements such as good choke and stall margin, high boosting pressure ratio, and high stage efficiency, it is also necessary to reduce the turbocharger noise as much as possible for a more comfortable working environment. The most effective way is to reduce the compressor noise at the source, i.e. the compressor impeller itself must produce less aerodynamic noise rather than using any silencers. In this paper, we present a redesign work for an existing impeller wheel using the 3D inverse method with an in-house aeroacoustic code. The CFD simulations for the compressor characteristics and internal flow field details, the numerical predictions of aeroacoustic sound emissions, and FEA analysis for the structure integrity have all been attempted to thoroughly assess the performances of baseline and optimised impellers. The computational results found that the new impeller can lead to better performances in all three aspects, which are supported by the experimental measurements conducted for both impellers using the same test configurations. The experimental data confirmed that the inversely redesigned impeller wheel provides a wider compressor operating range, higher efficiency at large rotating speed, and a few dB(A)s lower noise emissions in the upstream radiation direction.
Experimental Study of Flow Inside a Centrifugal Fan Using Magnetic Resonance Velocimetry
Authors: Hoffman Davis W. , Villafañe Laura , Elkins Christopher J. , Eaton John K. 
Published: November 2019

Abstract
Three-dimensional, three-component time-averaged velocity fields have been measured within a low-speed centrifugal fan with forward curved blades. The model investigated is representative of fans commonly used in automotive HVAC applications. The flow was analyzed at two Reynolds numbers for the same ratio of blade rotational speed to outlet flow velocity. The flow patterns inside the volute were found to have weak sensitivity to Reynolds number. A pair of counter-rotating vortices evolve circumferentially within the volute with positive and negative helicity in the upper and lower regions, respectively. Measurements have been further extended to capture phase-resolved flow features by synchronizing the data acquisition with the blade passing frequency. The mean flow field through each blade passage is presented including the jet-wake structure extending from the blade and the separation zone on the suction side of the blade leading edge.
Novel Approaches for sCO2 Axial Turbine Design
Authors: Sathish Sharath , Kumar Pramod , Namburi Adi Narayana , Swami Lokesh , Fuetterer Carsten , Gopi Pramod Chandra 
Published: November 2019

Abstract
The axial sCO2 turbine design for shaft power above 10 MW can be approached in a manner similar to the High Pressure (HP), backpressure steam turbine. Starting from the overall performance specification, the detailed turbine design is carried out in steps; 1-Dimensional (1D) meanline design, Quasi 3D (Q3D) throughflow design, cascade blade-to-blade design, 3-Dimensional (3D) blade design, stress and vibration analysis. These design steps are well established and validated, using dedicated test rigs and field performance measurements, for the steam turbines. Even though detailed validation tests are not available for axial sCO2 turbines, there exists a scope to utilize the established steam turbine design principles. This paper highlights sCO2 turbine design procedure through a 10 MW turbine design case study for Waste Heat Recovery (WHR) power plant. The focus areas are blade-to-blade design and stress analysis for which the challenges and novel approaches to design are elucidated.
Classical blade design typically relies on expert knowledge where the 2D blade profile geometry is successively iterated to minimize the profile loss. Automated optimization routines are also employed by geometry parametrization techniques such as Bezier or B-Spline control points. This paper introduces a novel approach to 2D blade design as applied to a sCO2 turbine through a combination of Kulfan Class Shape Transformation (CST) for blade parametrization and unique optimization constraints to mimic the expert knowledge.
The high power density of sCO2 turbomachinery while advantageous for weight and footprint reduction poses significant challenge in mechanical design. The overall power is distributed among few stages resulting in higher blade stress compared to an equivalent steam turbine. Increasing the blade chord, alternative root design are some of the mitigation methods to deal with the increased stress. They however lead to compromise in aerodynamic performance due to reduced blade aspect ratio. This necessitates novel approaches to balance mechanical and aerodynamic design, which are considered in this paper.
Through a 10 MW sCO2 axial turbine design case study, this paper brings to the fore certain design challenges as compared to a conventional steam turbine and puts forth novel approaches to overcome the identified challenges.
Optimized SGT-A35 (GT61) for Improved Emissions and Enhanced Efficiency Across the Load Range
Authors: Thirumurthy Deepak , Ruggiero Barry , Chhibber Gautam , Singh Jaskirat 
Published: November 2019

Abstract
The RT61 is a three-stage industrial power turbine which couples with the SGT-A35 aeroderivative gas generator (formerly named Industrial RB211). It was designed for improved efficiency and modular construction for ease in maintainability. The aeroderivative SGT-A35 (GT61) product serves both oil & gas and power generation market with a fleet size of greater than 90 units.
In recent years, there has been increased emphasis on clean energy, only complemented by the regulatory changes and market conditions. The power generation and oil & gas customers (upstream, midstream, and downstream) are continuously looking for opportunities to decrease their greenhouse gas emissions and reduce fuel consumption by improving the gas turbine cycle efficiency.
The SGT-A35 (GT61) power turbine has > 93% isentropic efficiency and industry standard overhaul schedule of 100,000 hours. However the potential for further cycle efficiency improvements and reduction in emissions exist by optimizing the power turbine capacity to a specific load range. This served as the main motivation for this technical work.
This paper discusses the engineering efforts taken in implementing the above stated improvement and further optimizing the product for reduced emissions. The improvements are discussed on the product level and on the TransCanada Pipelines fleet level.
A new power turbine variant was developed on a demanding timeline driven by the customer project. A detailed development project was undertaken to establish the new operating point, aerodynamic design, and the new geometry. It was optimized to the customer project-specific load range. During the manufacturing phase, novel rapid prototyping methods were used to achieve desired lead times. Flow path change was limited to the first stage vane to minimize the introduction of new risks and uncertainties.
Assessment of Calibration Approaches for the Stress Relaxation Test
Authors: Pellicotte Jacob , Cotto Mario , Stewart Calvin 
Published: November 2019

Abstract
Advanced manufacturing technologies are enabling the next generation of superalloys for extreme temperatures, pressures, and longevity. There is a need for Accelerated Creep Test (ACT) methods to reduce the time needed to implement new creep resistant superalloys. Without the development of ACTs, the qualification of new superalloys using conventional creep tests can take 11+ years corresponding to the 100,000-hour service life of long-lived turbomachinery components. A refined stress relaxation test (SRT) is introduced to succeed real-time conventional creep tests (CCTs). The stress relaxation test generates extensive stress versus creep-strain-rate data within a single specimen. Since the specimen is held below the elastic limit and relatively little creep deformation has occurred, several SRTs at different temperatures can be performed using a single specimen. To obtain data, specimens are rapidly loaded in force-control to just below the elastic limit. The specimen is switched to displacement-control and held at a fixed displacement while stress relaxation occurs. This generates a stress versus time curve that must be converted into stress versus creep-strain-rate. The stress versus creep-strain-rate curves are utilized to calculate creep activation energy and produce a creep-strain-rate master curve. The objective of this study is to determine the best calibration approach for SRT: regression of stress, regression of creep strain, and the finite difference of creep strain. It is recommended that the differentiation be applied; however, finite difference applied to the raw data produces inconsistent calculations of the creep-strain-rate. In this study, a MATLAB algorithm is written to evaluate all three calibration options where, stress and creep deformation are regressed into natural logarithm functions. The resulting creep-strain-rate curves are compared to determine the most reliable and consistent method. Analyzing and evaluating the results the regression of stress and regression or creep strain calibration methods prove to provide accurate results. These methods will help replace CCTs by conducting less expensive ACTs, while increasing the overall efficiency of the development of new materials.