bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Geometry and Spacing in Additively Manufactured Microchannel Pin Fin Arrays
Authors: Ferster Katharine K. , Kirsch Kathryn L. , Thole Karen A. 
Published: August 2017

The demand for higher efficiency is ever-present in the gas turbine field and can be achieved through many different approaches. While additively manufactured parts have only recently been introduced into the hot section of a gas turbine engine, the manufacturing technology shows promise for more widespread implementation since the process allows a designer to push the limits on capabilities of traditional machining and potentially impact turbine efficiencies.
Pin fins are conventionally used in turbine airfoils to remove heat from locations in which high thermal and mechanical stresses are present. This study employs the benefits of additive manufacturing to make uniquely shaped pin fins, with the goal of increased performance over conventional cylindrical pin fin arrays. Triangular, star, and spherical shaped pin fins placed in microchannel test coupons were manufactured using Direct Metal Laser Sintering. These coupons were experimentally investigated for pressure loss and heat transfer at a range of Reynolds numbers. Spacing, number of pin fins in the array, and pin fin geometry were variables that changed pressure loss and heat transfer in this study. Results indicate that the additively manufactured triangles and cylinders outperform conventional pin fin arrays, while stars and dimpled spheres did not.
Comparison of a Heat Soakage Model With Turbofan Transient Engine Data
Authors: Vieweg Maximilian , Wolters Florian , Becker Richard-Gregor 
Published: August 2017

In the present paper, a transient performance code is employed to predict on-wing test data of the IAE-V2500 engine mounted on an Airbus A320-232. The test data was recorded by the engine control system and may serve as an open basis for validation of future transient studies. For the current investigation, the employed code considers the fundamental equations of the constant mass flow method as well as heat transfer effects by a lumped parameter approach.
The study focuses on seven accelerations and one deceleration. Engine test data was gathered with 10Hz sampling rate, imprinting the applied time step of the model. First, the steady-state matching of the test data was conducted. Subsequently, the measurement quantities fuel flow, inlet temperature and inlet pressure were prescribed as time-varying boundary conditions to the transient model. The results of the standard transient model and the model including thermal effects were compared with temperatures, pressures and shaft speeds. The LPT outlet temperature and the working line excursion in the booster map were examined in detail. The outcome concurs with the original statement that thermal effects are mandatory to enhance model accuracy. Lastly, a sensitivity analysis of the thermal input parameters was accomplished and its influence on model prediction investigated.
Design of a Bimetallic Blisk Turbine for a Gas Turbine Engine and its Production Using Powder Metallurgy Methods
Authors: Magerramova Liubov , Vasilyev Boris , Nigmatullin Ravil , Kinzburskiy Vladimir 
Published: August 2017

One key engine component that defines the main engine characteristics is the wheel of a high-pressure turbine. One reasonable approach for increasing the efficiency of this type of turbine is to use blade shrouding. However, this shrouding also increases the centrifugal loading on the profile part of the blades, the lock connection, and the disk. One solution to this issue is to eliminate the lock connections, i.e. to create wheels of a blisk-type design.
The bimetallic blisk was developed based on a wheel that has a lock connection for the disk and blades without shrouds. This study presents a redesign of the profile parts of the blades using computational fluid dynamics calculations, and a reintroduction of shrouds to the blade design. Connection of the blades to the disc involved a newly developed process based on powder metallurgy. The result is a bimetallic blisk consisting of single-crystal blades with shrouds and a disk consisting of a granulated heat-resistant nickel base alloy, connected by hot isostatic pressing. This bimetallic blisk satisfies the strength requirements and is detuned from the resonant frequencies. The weight is 7% lower for the developed design than for the prototype, and the turbine efficiency is increased by 2%.
Further Development of Modified Theta Project Creep Models With Life Fraction Hardening
Authors: Day W. David , Gordon Ali P. 
Published: August 2017

In order to optimally design a hot section component for creep, the designer and turbine durability specialist must have confidence in their predictive tools and be able to gain design insight from these analytical tools. The modified theta projection (MTP) creep model was previously presented as an accurate means of describing creep behavior as a function of stress, temperature and time. The MTP was then implemented in an analytical model using a life fraction hardening (LFH) rule to calculate creep in the presence of time-varying stresses, and the results presented in a second paper. This paper presents improvements to the technique through the use of state variables in addition to the previously shown strain life fraction (ELF) and temperature margin (TMar). The need for performing multiple creep analyses is avoided by adding state variables to that track estimates of the effect of temperature changes on stress relaxation and life fraction, as well as an allowance for material variability and an inexact fit of material behavior.
The results of creep tests, on a nickel blade alloy, with incrementally increasing or decreasing loads are presented to provide validation of the accuracy of the life fraction hardening rule. The use of MTP and LFH has now been expanded to steels. Incremental testing results are examined for a NiCrMoV rotor steel to further validate the technique. The effect of true stress on model accuracy is also presented. Now that an accurate creep model and hardening rule have been implemented, expansion of the techniques to provides more useable design information and allows us to improve the structural integrity of turbine blades, vanes and rotors.
Oil Film Thickness Measurements on Surfaces Close to an Aero-Engine Ball Bearing Using Optical Techniques
Authors: Hee Jee Loong , Santhosh R. , Simmons Kathy , Johnson Graham , Hann David , Walsh Michael 
Published: August 2017

In a civil aero-engine transmission system a number of bearings are used for shaft location and load support. A bespoke experimental test facility in the University of Nottingham’s Gas Turbine and Transmissions Research Centre (G2TRC) was created to investigate oil shedding from a location bearing. An engine representative ball bearing was installed in the rig and under-race lubrication was supplied via under-race feed to three locations under the inner race and cage. The oil was supplied in an engine representative manner but the delivery system was modified to provide circumferentially even flow. An electromagnetic load system was designed and implemented to allow engine representative axial loads between 5 and 35 kN to be applied to the bearing. In this phase of testing the rig was operated at shaft speeds between 1,000 rpm and 7,000 rpm for a range of oil flow rates and low and high load conditions. The rig was designed with good visual access and high speed imaging was used to investigate film formation and movement on surfaces close to the bearing.
This paper presents images and qualitative observations of thin film formed on the static surfaces forming the outer-periphery of the bearing compartment as well as the gap between orbiting cage and static outer race. Quantitative film thickness was obtained at two circumferential locations (90° and 270° from top dead centre) and three axial locations, through sophisticated analysis of the high speed images. The effect on film thickness of the varied parameters rotational speed, axial load and oil feed input flow rate are presented in this paper.
It was observed that for all axial planes of measurement in both co-current and counter-current regions film thickness decreases with increase in shaft rotational speed. At 5,000 and 7,000 rpm film thicknesses are around 0.75 mm – 1 mm and are similar at 90° and 270°; at 3,000 rpm films tend to be somewhat thicker at around 1.5 mm – 2 mm and are thicker in the counter current region, particularly closer to the bearing. It is suggested that at higher shaft speeds interfacial shear dominates whereas at lower speed the effect of gravity in slowing the film in the counter-current region causes a measureable difference.
It was further observed that increasing the input oil flow rate from 5.2 litres per minute to 7.3 litres per minute did not produce significant effect on film thickness. However, the increase of axial bearing load from 10 kN to 30 kN yielded thicker films at the location above the cage.
In all cases there was waviness on the film surface at the bearing outer periphery; imaging was not sufficient to see if the film surface close to the bearing is wavy.
Effect of Cooling on the Aerodynamic Performance in the Intercooled Compressor Vanes
Authors: Liu Long-gang , Li Xue-song , Ren Xiao-dong , Gu Chun-wei 
Published: August 2017

An intercooling technique using convective cooling channels in the compressor stator vanes has been proposed in recent years. In this paper, two cooling methods are presented and conjugate heat transfer method is used in the numerical simulation to study the effect of cooling on the laminar boundary layer and turbulent boundary layer in compressors. The overall performance of the compressor is also analyzed.
A flat plate in T3C series experiments under adverse pressure gradient has been simulated to verify the aerodynamic simulation and preliminarily investigate the cooling effect. Subsequently, a two-dimensional compressor vane NACA65-(12A2I8b)10 has been numerically simulated to study the cooling effect on two-dimensional boundary layer of the curve surface. The numerical simulation results of the vane without cooling channel are in good agreement with the experiment data by NASA. By comparing it with the case which has convective cooling channels, it can be found that the cooling decreases the size of laminar separation bubble and delays the turbulent separation, which reduces the loss at both the design and off-design angle of attack.
A three-dimensional highly-loaded five-stage axial compressor whose stator vanes have cooling channels and cooling endwalls has also been numerically simulated. The cooling channels and endwalls decrease the temperature rising of the main stream with a slight increase of the pressure rising, which indicates that this intercooling method can be used in the intercooled and recuperated (ICR) cycle. Cooling channels decrease the temperature of the stator vanes and protect them from the high temperature. Besides, the effect of cooling on the turbulent separation in the corner region has also been investigated. The cooling channels decrease the total pressure loss, which indicates that cooling has a beneficial effect on the aerodynamic performance of the compressor.
Numerical Simulations of Flow Fields and Heat Transfer Characteristics in Tenon Joint Gap Between Turbine Blade and Disk Under Rotating Conditions
Authors: Chen Da-wei , Zhu Hui-ren , Xu Yang , Jia Xiao-meng , Liu Cong , Lu Hai-ying 
Published: August 2017

Turbine blades and the disks are connected by tenons. There is a pair of jagged assembly clearance between each tenon and corresponding mortise. In practical engineering applications, flow and heat transfer characteristics in assembly clearance used to be simplified. In order to obtain more accurate temperature fields of the turbine blades and disks, detailed study of the flow and heat transfer mechanism in tenon joint gap is necessary.
In this paper, two typical assembly clearances under the stationary and rotating conditions were investigated numerically, including double S-shaped and double Crescent-shaped. The inlet Reynolds numbers range from 5,500 to 50,000 and the Rotation numbers range from 0 to 0.005. The results show that the fluids in the two branches of the double S-shaped channel have different flow characteristics under rotating conditions. A vortex is formed at the corner of the left branch and the vortex scale can be influenced by Re and Ro. The large vortex decreases the local heat transfer coefficient. In the right branch, the three-dimensional flow from the flat wall to the concave wall increases the local heat transfer coefficient of different regions. For the double Crescent-shaped channel, the region with higher velocity is offset to the right of the channel which leads to higher local heat transfer coefficient under rotating conditions. The simulation results have great significance to the heat transfer analysis of turbine blades and disks.
Development of Porous Injection Technology to Reduce Emissions for Dry Low NOx Combustors: Micromixer and Swirl Injectors
Authors: Bhayaraju Umesh , Hamza Mahmoud , Jeng San-Mou 
Published: August 2017

The Combustion and Fire Research Laboratory (CFRL) at the University of Cincinnati (UC) is working on the development of advanced next generation injectors for DLN combustors. Several inputs were received from the project partners during the development phase. In the present paper, developmental work on two novel injectors with Porous Injection Technology (PIT) is presented. The technology has the potential to reduce NOx emissions to single digit PPM level with a stable combustion across wide range of load conditions.
One of the key factors that are essential for lowering NOx levels is the efficient mixing of fuel-air in both spatial and temporal domains. The porous injection technology has the potential to reduce the spatial and temporal gradients to a minimum. In the present paper, two measurement techniques were used to evaluate the fuel-air mixing under atmospheric conditions. The CO2 mixing technique was used to quantify the spatial variations in the fuel mass fraction. Planar Laser Induced Fluorescence (PLIF) was used to obtain both spatial and temporal fuel mass fractions. The CO2 mixing measurements were used to validate the PLIF data for quantification. The RMS fluctuations in spatial and temporal domains were quantified from PLIF data. The combustion experiments were carried out at atmospheric pressure with a preheated temperature of air of 500–650 K and equivalence ratio of 0.5–0.8. The pressure drop across the injector was 4%. Natural gas with 90% methane and 9% ethane was used as fuel. The results show a stable flame for both injectors without combustion instabilities. Both injectors show low NOx levels. For conventional swirl stabilized design with PIT, the NOx levels were of the order of 1.5 ppm at the firing temperature of 1866 K whereas for the novel micromixer design, the NOx levels were of the order of 4 ppm @ ∼1866 K.
Staged Combustion System for Improved Emissions Operability and Flexibility for 7HA Class Heavy Duty Gas Turbine Engine
Authors: Karim Hasan , Natarajan Jayaprakash , Narra Venkat , Cai Jun , Rao Shreekrishna , Kegley Jonathan , Citeno Joseph 
Published: August 2017

Driven by global warming, a relentless march towards increased fuel efficiency has resulted in increased firing temperature for HA-class engines without an increase in baseload emissions. Moreover, emissions compliance for CO, NOx, and unburned hydrocarbons are desired over increased range in gas turbine load. In addition, exceptional gas turbine operational flexibility is desired to address potential intermittency due to the penetration of renewables in the electrical grid.
Staged/sequential combustion is a state of the technology to provide operational flexibility and reduced emissions in power generation gas turbines. GE Power’s 7HA-class gas turbine combustion system combines GE’s proven DLN-2.6+ combustion technology, that has run reliably for over 1.3 million fired hours across more than eighty 9FA.03, 9F.05 & 7FA gas turbine engines, with an axially fuel staged system (AFS). Axially staging combustion to two zones allows for increased firing temperature at baseload (while maintaining the same NOx level) by operating the later/second stage hotter than the first/primary stage. During low load operation as the gas turbine firing temperature is reduced, percentage fuel split in the staged fuel system can either be reduced significantly or turned off and thereby keeping the overall combustion system into emissions compliance over a wider range of firing temperatures.
This paper presents both the development testing of the staged combustion in the FA and HA class gas turbine combustion system rigs at GE Power’s Gas Turbine Technology Laboratory and the validation testing of staged combustion system for the 7HA.01 engine completed during Spring 2016 at GE Power’s engine test facility in Greenville, SC. The paper also discusses the significant simplification of operational principle and flexibility of startup, loading and baseload operation of the 7HA combustion system. Discussion of engine test results will show how axial fuel staging was utilized to demonstrate emissions compliance ( NOx (15% O2) < 25 ppm; CO < 9 ppm), operation from 14% load to 100% load with low combustion dynamics and also to enable wide wobbe capability, which is a normalized measure of fuel flexibility.
A Centrifugal Compressor Impeller: A Multidisciplinary Optimization to Improve its Mass, Strength, and Gas-Dynamic Characteristics
Authors: Salnikov Anton , Danilov Maxim 
Published: August 2017

The high-loaded centrifugal compressor blisk-type impeller, one of the main low-sized gas-turbine engine components, strongly affects engine efficiency. However, its design is a time-consuming and complex task for several reasons, including its high loading, the large number of structural and technological constraints, and the variety of requirements needed for application to a gas-turbine engine centrifugal compressor impeller (e.g., increased efficiency and strength, minimized weight requirements, etc.).
The imposition of several constraints for structure modification of the centrifugal wheels can improve one characteristic but can worsen others. The standard solution for this problem is to use an iterative approach, whereby the design process is reduced to a consistent set of impeller element design problem statements and decisions; these are separate for different analysis disciplines.
The main drawbacks to this approach are that it is labor intensive and can cause deterioration of the design quality because this procedure does not consider the design object as a unit. The present work considers a centrifugal compressor wheel design approach based on the use of an integrated multidisciplinary parameterized 3D model. This model includes a number of specialized sub-models that describe the necessary design areas as well as physical process features and phenomena occurring in the designed object. The model also realizes the integration and interaction of sub-models used in an integrated computing space.
The proposed approach allows the optimization of the structure based on several criteria, such as the mass of the wheel, stage efficiency, strength, economic indicators, etc. The result of multi-criteria optimization is not a single product design, but a set of optimal Pareto points, which describes a number of centrifugal wheel models. The optimal configuration is selected from this set, based on what is considered the most important criterion.
Optimization criteria may vary depending on the problem formulation, but the design technology, parameterization scheme, and choice of multidisciplinary integrated mathematical model are retained. Therefore, in the case of a product requirement correction, a new optimal design will require less time. In aggregate, with the nonlinear constrained optimization application, this approach reduces the total time of the design cycle, decreases development costs, and improves quality.
Valve Body Thermal Stress Control While Warming Up
Authors: He Jin 
Published: August 2017

Quasi-stationary theory is applied to a simplified one-dimensional solid to work out warm-up thermal stress [1]. This paper verifies the quasi-stationary state exits in the three-dimensional valve body warm-up process, and the relationship of the thermal stress and the temperature difference is similar.
Dynamic analysis of warming-up at constant temperature increasing speed shows that: the ratio of the thermal stresses and the temperature difference gets the max value at the quasi-stationary state. The ratio is not influenced by the surface heat transfer coefficient, the material thermal diffusion coefficient and the temperature raise speed. It is a safety way to estimate the thermal stresses by temperature difference multiplied by this max ratio value. For quasi-stationary, once the temperature measure points be located, the ratio between stresses of any selected point and temperature difference is fixed. Where to set the measure points is unlimited, and the mean metal temperature, which is not easy to get, may not be applied anymore.
Predicting the Influence of Damping Devices on the Stability Margin of an Annular Combustor
Authors: Zahn Max , Betz Michael , Schulze Moritz , Hirsch Christoph , Sattelmayer Thomas 
Published: August 2017

A numerical modeling approach based on linearized Euler equations is applied to predict the linear stability of an annular combustor with and without dampers. The acoustic properties of all relevant combustor components such as damping devices, swirl burner characteristics, swirl flame dynamics, and combustor exit are individually evaluated via experimental and numerical approaches. All of the components are incorporated subsequently into the combustor model using impedances and acoustic transfer matrices to obtain an efficient procedure.
This study focuses on using this approach to predict an annular combustor’s stability margin and to assess how dampers influence the modal dynamics of the first azimuthal mode. Stability predictions are successfully validated with experimental data. Different combustor components’ contributions to the acoustic damping of the entire system is also determined based on that numerical approach. Damper application in combustors can engender uncertainties in resonance frequency in the case of hot-gas ingestion. The impact of “detuned” resonators on the predicted damping rates with respect to a deviation in the resonance frequency and the eigenfrequency of the attenuated acoustic mode is therefore evaluated. The influence of dampers on the annular combustor’s stability margin is also determined.