bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ignition and Flame Stabilization of a Premixed Jet in Hot Cross Flow
Authors: Schmitt Denise , Kolb Michael , Weinzierl Johannes , Hirsch Christoph , Sattelmayer Thomas 
Published: November 2013

At the Institute of Thermodynamics, Technical University of Munich a large scale atmospheric combustion test rig has been designed and set up. The experimental setup is comprised of two burning zones: A first zone consists of 16 burners providing vitiated air at 1776K, into which a secondary fuel-air mixture jet is injected and ignited by the hot cross flow. The phenomenon is known in the literature as a reacting jet in hot cross flow. The hot data is compared to the cold case in order to show differences in the flow field due to flame propagation.
For evaluating the flow field several experimental analyses have been applied so far (OH*, High-Speed PIV, Mixture Analysis). The focus of this paper is on the momentum ratios J = 4–10 with Jet Reynolds Numbers between 20,000 and 80,000. For the cold case the flow field is measured and compared with the reacting jet. In the injector the air and the natural gas are perfectly premixed. The equivalence ratio of the jet is varied over a wide range of mixtures (ϕ = 0.05–0.77) resulting in an adiabatic flame temperature of the jet between 800 and 2200K. As the pictures of the chemiluminescence analysis show the jet gas ignites immediately upon entering the hot cross flow. The distinct influence of the equivalence ratio on the flame length and shape can be seen in the data. The trajectory of the flame penetrates further into the channel compared to the trajectory of the cold case caused by the reaction in the flame and its resulting gas expansion. Due to the large diameter of the jet in the experiment the origins of the dominant flow patterns are obtained with high spatial resolution. Following this, flame anchoring mechanisms at different operation points are derived.
A Four Component Skeletal Model for the Analysis of Jet Fuel Surrogate Combustion
Authors: Akih-Kumgeh Ben , Bergthorson Jeffrey M. 
Published: November 2013

A skeletal chemical kinetic model for jet fuel combustion, comprising four representative fuel components, is presented. The sub model for the three components, toluene, methyl cyclohexane (MCH) and n-dodecane, is deduced from a detailed model for jet fuel surrogate proposed by Wang et al. [Wang et al., 2010]. The reduction is based on a species sensitivity approach, herein referred to as Alternate Species Elimination (ASE). The sub model for the fourth component, iso-octane, is established through semi-detailed kinetic modeling, considering existing reactions and species of the smaller hydrocarbon systems as well as species and reactions pertinent to the n-dodecane system.
The performance of the resulting model is assessed by comparing predictions of ignition delay times and laminar burning velocities with those of the detailed model. It is shown that the skeletal model retains the predictive ability of the detailed model with respect to the three components, n-dodecane, MCH and toluene. The complementary iso-octane sub model is also found to reasonably predict high-temperature ignition delay times and laminar burning velocities.
The four component skeletal model is tested against shock tube ignition data and laminar burning velocities of jet fuel surrogates. It is observed that high-temperature ignition is fairly well predicted while low-temperature ignition delay times are longer than experimentally observed. While the predictions of laminar burning velocities of atmospheric flames of jet fuels at 400 K are reasonable, slower flames are predicted at higher temperatures. The proposed skeletal model has 192 species and 1291 reactions, compared to the detailed multi-component model, with 348 species and 2163 elementary reactions, albeit without iso-octane. This results in improvement in the associated computational costs for combustion analysis. Further development of the skeletal model is needed to improve its prediction ability over a wider range of combustion properties and thermodynamic conditions.
Influence of Fuel Composition, Engine Power and Operation Mode on Exhaust Gas Particulate Size Distribution and Gaseous Emissions From a Gas Turbine Engine
Authors: Li Hu , Altaher Mohamed A. , Wilson Chris , Blakey Simon , Chung Winson 
Published: November 2013

The impact of fuel composition, engine power (idle and full power) and operation mode (cold and hot idle) on the gaseous emissions, particle number and mass concentrations and size distributions from an aircraft auxiliary power unit (APU) was investigated. A re-commissioned Artouste MK113 APU engine was used. The engine was run at three operational modes: i.e. approximately 6 minutes at idle (cold idle) after stabilized from start, 6 minutes at full power and then returning to idle again (hot idle) for 6 minutes. All operating parameters of the engine were monitored and recorded. The engine exhaust particle measurements and gaseous emissions were taken at three operating modes.
Five alternative fuels/blending components were tested and compared to neat conventional JetA1 fuel either in pure or blended forms. These fuels varied in their compositions in terms of H/C ratio, density and other properties. A Scanning Mobility Particle Sizer (SMPS) with a Nano-Differential Mobility Analyzer (NDMA) was used to determine the number and mass concentration and size distribution of engine exhaust in the size range from 5 nm to 160 nm. The influence of fuel elemental ratio (H/C), engine power and cold/hot operation on particle number and mass size distribution was investigated. The results show that there was a good correlation between fuels H/C ratio and particle concentrations, particle size and distributions characteristics. The engine at hot idle produced ∼20% less particles compare to the results at cold idle. The alternative fuel blends produced less particles than JetA1 fuel. The testing fuels produced similar levels of NOx, slight reductions in CO and remarkable reductions in UHC compared to JetA1.
Designing Turbochargers With an Integrated Design System
Authors: Qiu Xuwen , Fredriksson Carl F. , Baines Nicholas C. , Backlund Markus 
Published: November 2013

One of the more visible tasks when designing a turbocharger is the optimized design for a compressor and a turbine. The ultimate measure of a successful turbocharger design, however, is how well it works with a specific engine at various operating conditions. Final design decisions must be based on the engine-turbocharger system as a whole, rather than only on the individual component performance.
This paper describes the effort to develop an integrated design system which allows the user to design and optimize a turbocharger on a system level. With the basic engine parameters specified, along with simple models for other commonly used components, such as the Exhaust Gas Recirculation (EGR), wastegate, and intercooler, the program may be linked to two powerful meanline programs that can handle the fast iterations of the design and analysis of a compressor and a turbine. The output is either a new compressor or turbine that best matches the operation of the engine or the performance of an existing turbocharger at a specific engine operating condition.
A case study is presented where the program is applied in a real-life design situation to fit a new turbocharger for a large locomotive 18-cylinder diesel engine. The tool is extensively used in guiding the selection of the turbocharger and in the simulation of the overall system performance. The test data from the new design show close agreement with the simulation results, as well as an improvement over the original design.
An Energy-Based Method for Predicting the Additive Effect of Multiple Film Cooling Rows
Authors: Kirollos Benjamin , Povey Thomas 
Published: November 2013

There have been numerous studies reporting film effectiveness for film rows in isolation, which have led to correlations which are used for preliminary design. Many applications require multiple film cooling rows. Although there is some published data which deals with the combined effect of multiple rows, in most design situations the additive effect is computed using correlations for single rows. The most widely used method is the Sellers superposition method. In many applications the method gives accurate results. Although the method is to some extent physically based, energy is not conserved within the model, and in certain situations this limitation can be shown to lead to an under-prediction of the film effectiveness.
In this paper, a new energy-based method for predicting the additive effect of multiple film cooling rows is outlined. The physical basis and limitations of the model are discussed. Predictions conducted using the new method are compared with CFD data and contrasted with the Sellers method. In situations where energy conservation is required to avoid under-prediction of effectiveness the method is shown to be advantageous.
Numerical Analysis of the Conceptual Design of Arrayed-Vanes Premixer for Gas Turbine Combustors Burning High-Hydrogen Fuels
Authors: Yu Zongming , Wu Xinnan , Wu Feifan , Wang Yue , Kong Wenjun , Feng Yongzhi , Wang Hui 
Published: November 2013

Using high-hydrogen fuels in industrial gas turbines is an effective way to achieve near-zero carbon emission power generation. Lean premixed combustion can effectively reduce NOx emission. However, due to the strong flashback and auto-ignition tendencies during fuel-air mixing, it is a challenge to use lean premix combustion mode of high hydrogen fuels under gas turbine operation conditions.
An innovative conceptual design of arrayed-vanes premixer was proposed to achieve safe and uniform mixing of fuel and air. Inside the arrayed-vanes premixer, a cascade of mixing vanes is arranged in the axial annular air flow passage. Fuel-air mixing and flow field stretch are improved and well controlled by the arrayed vanes. The conditions of auto-ignition and flame stabilization inside the vanes are unsatisfied. Meanwhile the upstream flow disturbance will be inhibited by the arrayed vanes, which benefits combustion stability.
The arrayed-vanes premixer was designed and its flow field was numerically simulated under the operation condition of F class gas turbine combustors. The flow and fuel-air mixing behavior was analyzed and compared with a typical swirl-based premixer now widely used in DLN combustors of F class gas turbines. The results show that the non-uniformity index of fuel concentration distribution at the exit plane of the arrayed-vanes premixer is 50% lower than that of the swirl-based premixer.
The responses of flow field at the exit plane to the inlet flow disturbance was calculated and compared for the two types of permixer. The inlet flow disturbance includes the velocity distortion and the oscillation of the pressure. The results show that the arrayed-vanes premixer absorbs and damps the inlet flow disturbance better than the swirl-based premixer. And it exhibits highly monochromatic characteristic through the acoustic signature analysis.
Furthermore, the tendencies of auto-ignition and flashback were investigated by examining the flow field and the flammability of hydrogen. The results show that there is a low risk of auto-ignition or flashback due to the short residence time and the high discharge velocity.
The present study indicates that the arrayed-vanes premixer achieves ultra uniform fuel-air mixing, good adaptability to inlet flow disturbance and anti auto-ignition and flash back, which is benefit to DLN combustor designed for high-hydrogen fuels. This design will be possibly used in DLN combustors after future developments.
Preliminary Calculations on Post Combustion Carbon Capture From Gas Turbines With Flue Gas Recycle
Authors: Akram Muhammad , Khandelwal Bhupendra , Blakey Simon , Wilson Christopher W. 
Published: November 2013

Carbon capture is getting increased attention recently due to the fact that it seems to be the only answer to decrease emissions. Gas turbines exhaust have 3–5 % concentration of CO2 which is very low to be captured by an amine carbon capture plant effectively. The amine based plants are most effective at around 10 – 15% CO2 in the flue gas. In order to increase the concentration of CO2 in the exhaust of the gas turbine, part of the exhaust gas needs to be recycled back to the air inlet. On reaching the concentration of CO2 around 10% it can be fed to the amine capture plant for effective carbon capture.
A 100 kWe (plus 150 kW hot water) CHP gas turbine Turbec T100 is installed at the Low Carbon Combustion Centre of the University of Sheffield. The turbine set up will be modified to make it CO2 capture ready. The exhaust gases obtained will be piped to amine capture plant for testing capture efficiency. Preliminary calculations have been done and presented in this paper. The thermodynamic properties of CO2 are different from nitrogen and will have an effect on compressor, combustor and turbine performance. Preliminary calculations of recycle ratios and other performance based parameters have been presented in this paper. This paper also covers the aspects of turbine set up machinery which needs to be modified and what kind of modifications may be needed.
Using a Lubrication Test Bench for Testing New Oil Quality Sensors
Authors: Berten Olivier , Hendrick Patrick , Villar Alberto , Seveno David 
Published: November 2013

The Université Libre de Bruxelles/ Aero-Thermo-Mechanics Department (ULB/ATM) has developed a flow bench used to mimic the complete behaviour of an aircraft gas turbine engine lubrication system.
This test bench has been improved to be fully instrumented and is really multi-purposes in order to test different lubrication devices in the supply circuit (pure oil) or in the scavenge part (two-phase flow) simulating real flight conditions (oil flow rate, oil temperature and pressure…).
The paper will first present the characteristics of the lubrication test bench and its capabilities.
In a second part, it will be presented the integration and the test results of two different types of sensors into the lubrication test bench. One sensor is based on measuring the change in frequency of a quartz crystal resonator. The other one is composed of two optical sensors, which are able to monitor different properties of the oil and also to detect particles in the oil.
A Chemical-Kinetic Investigation of Combustion Properties of Alternative Fuels: A Step Towards More Efficient Power Generation
Authors: Methling Torsten , Braun-Unkhoff Marina , Riedel Uwe 
Published: November 2013

Biomass is a clean, renewable energy source with a large potential to contribute significantly to power generation, promising a more environmentally friendly production of electricity in future, with lower greenhouse gas emissions.
A large variety of biomass feedstock exists, including agricultural and biomass residues and by-products, with wood, sludge, and waste among them. Biomass can be used directly to generate electricity if converted to more user-friendly sources of energy, e.g. by fermentation producing mainly methane (biogas) and by gasification leading mostly to hydrogen and carbon monoxide (syngas), allowing a more efficient use of the product gases compared to direct combustion, besides further advantages, with less amounts of ash and corrosive species.
The resulting product gases can be burned in small to large scale gas turbines, stand alone, process integrated or in combined cycles. In a hybrid power plant, an increase of the electrical efficiency of small gas turbines to more than 50 % can be reached, by coupling a gasifier or biogas reactor with a fuel cell (FC) and a micro gas turbine.
To widen the acceptable range in the variation of fuel composition and conditions and to ensure a reliable and more efficient operation, it is of outmost importance to expand our knowledge on biogenic gas mixtures with respect to modeling capabilities e.g. of major combustion properties, thus enabling predictive calculations.
The present work is dealing with the use of representative biogenic gas mixtures for decentralized power production. The concept of coupling a gasifier or biogas reactor with a fuel cell and a micro gas turbine (hybrid power plant) is followed.
The product gases are stemming from the fermentation of sludge and algae as well as from the gasification of their residues and wood, in addition. Their combustion behavior — lower heating value (LHV), Wobbe index, adiabatic flame temperature, laminar flame speed, and ignition delay time — is calculated for the relevant parameters — fuel-air ratio, pressure — and discussed with respect to the intended use.
Coupled Fluid-Thermal-Solid Simulation of Axial Through-Flow Rotating Cavities
Authors: Yi Wei-lin , Zhang Xiao-hang , Ji Lu-cheng , Chen Jiang 
Published: November 2013

The rotating cavities of aero-engine compressors are the main part of secondary air flow system. It is known that there are typical multidisciplinary fluid-thermal-solid coupling characteristics in them. The high precision prediction of disc surface temperature is very important for structure designer to select materials, control blade clearances et al. The aim of this paper is to investigate the aerodynamic-thermal simulation model to obtain the method and tool for reliable temperature prediction.
The paper firstly selected publicly available experimental data of two rotating cavity geometries with twin-discs to validate the precision of established fluid-thermal simulation model with the different grids, difference schemes and turbulence models. The results showed that the RNG-KE turbulence model with QUICK scheme has the better simulation precision for flow structure and Nusselt number distribution.
Based on the above research, a fluid-thermal-solid coupling simulation of a twin-cavities model which is approaching to the real conditions of aero-engine has been carried out. The wall temperature distribution on inner surface has been obtained and its maximum error comparing with the experimental value is 8°C. Also the results further validated the reliabilities of the flow model, heat transfer model and fluid-thermal-solid coupling model. The paper also shows the flow field structure of rotating cavity for further understanding the internal flow characteristics.
Optimizing Lifetime Consumption and Increasing Flexibility Using Enhanced Lifetime Assessment Methods With Automated Stress Calculation From Long-Term Operation Data
Authors: Vogt Jan , Schaaf Thomas , Helbig Klaus 
Published: November 2013

In the past most of the steam turbines were designed as base load machines. Due to new market requirements based on the effect of renewable energies, power plant operators are forced to operate with more frequent start-up events and load changes, resulting in a fundamental higher low cycle fatigue (LCF) lifetime consumption.
Traditional methods of lifetime assessment often use representative start-ups, for the calculation of LCF damage, which can provide very conservative results with reasonable safety margins. For a high number of starts these safety margins may result in an overestimation of the LCF damage.
At Alstom, an enhanced method for lifetime assessment has been developed, that evaluates the actual lifetime consumption from real operation data in an automated manner and provides much more realistic results.
The operation data is used to calculate the transient temperature distribution and heat transfer coefficients along the rotor for each start-stop cycle. The corresponding stress distribution in the rotor is evaluated by means of a Finite-Element-method analysis.
Finally the number of remaining cycles is extracted for the most critical locations using material data. In combination with the creep damage the lifetime consumption is evaluated. The entire process is highly automated, but also facilitates easy monitoring through the lifetime engineer by graphic presentation of calculation results.
Using this enhanced method of lifetime assessment, the computed lifetime consumption is closer to the actual value, supporting the planning of overhauls and component replacements and minimizing the risk of failure or forced outages.
The utilization of remaining lifetime can be optimized in favour of a more flexible mode of operation (e.g. low load operation and fast start-up) or extension of operational lifetime for conventional and combined cycle power plants.
Crystallographic Orientation Evolution in NbSS-Nb5Si3 Eutectic Alloys by EBSD Analyses
Authors: Li Y. L. , Ma C. L. , Zhang H. 
Published: November 2013

The progresses in high temperature materials encourage the development of turbine engine in terms of thrust and efficiency. Ni-based superalloys, which are predominant in elevated temperature application, have limited potential to raise serving temperature. In-situ composites, such as Cr-Cr3Si, NiAl-Cr and Nb-Nb5Si3 eutectic alloys, consisting of a ductile metallic phase and a hard intermetallic phase, are attractive candidates to replace Ni-based superalloys. The microstructure and mechanical properties of these in-situ composites are widely investigated. However, little work is focused on crystallography of in-situ composites, except for preferred growth direction and crystallographic orientation relationship.
In this paper, Nb-Si-Mo-based alloys were fabricated by non-consumable arc melting, and then were directionally solidified in an optical floating zone (OFZ) melting furnace. The crystallographic orientation evolutions in Nb-Nb5Si3 eutectic alloy are studied by electron back-scattered diffraction (EBSD) analyses. First, the effect of solidification condition on crystallographic orientation is examined. The as-cast alloy displays cellular microstructure. The Nb phase shows different crystallographic orientations in different cells, while the Nb5Si3 phase shows similar crystallographic orientation in a number of cells. In directionally solidified alloys, when growth rate is 5mm/h without seed rod rotation, the grain sizes of Nb and Nb5Si3 are both several millimeter. As growth rate rises or seed rod rotates, the grain size of Nb decreases much more drastically than that of Nb5Si3. Thus, solidification condition is supposed to influence nucleation of the Nb phase rather than the Nb5Si3 phase. Second, the effect of annealing on crystallographic orientation is studied. The Nb5Si3 has three allotropic phases. The allotropic phase transformations occur through annealing, during which the Nb5Si3 grain size decreases.