bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three-Dimensional Mass Fraction Distribution of a Spray Measured by X-Ray Computed Tomography
Authors: Coletti Filippo , Benson Michael J. , Sagues Alexander L. , Miller Benjamin H. , Fahrig Rebecca , Eaton John K. 
Published: November 2013

In order to design a spraying system with the desired characteristics, the atomization process has to be understood in detail, including the primary break-up of the liquid core. Accurate prediction of primary break-up is a major barrier to computer-based analysis of spray combustion. The development of models is hindered by the lack of validation data in a region where the fluid is dense, and optical access is therefore limited.
The present experimental study is aimed at probing the spray structure by means of X-ray computed tomography (CT). A full-cone atomizer (0.79 mm orifice diameter) spraying in air at ambient pressure is investigated as a proof of concept. A mixture of water and iodine is used as the working fluid, providing elevated X-ray absorption and therefore improved signal-to-noise ratio. Several hundreds of X-ray projections are acquired as the spraying atomizer is rotated in front of the detector. Standard software for medical imaging is used to reconstruct the three-dimensional time-averaged distribution of liquid mass fraction in the full field of view, from the intact liquid core to the dilute spray region. A spatial resolution of 0.6 mm is obtained along the spraying direction, while the resolution is 0.3 mm in the other two directions. Significant asymmetries in the structure of the spray are revealed.
Siemens SGT-800 Industrial Gas Turbine Enhanced to 50MW: Combustor Design Modifications, Validation and Operation Experience
Authors: Lörstad Daniel , Lindholm Annika , Pettersson Jan , Björkman Mats , Hultmark Ingvar 
Published: November 2013

Siemens Oil & Gas introduced an enhanced SGT-800 gas turbine during 2010. The new power rating is 50.5MW at a 38.3% electrical efficiency in simple cycle (ISO) and best in class combined-cycle performance of more than 55%, for improved fuel flexibility at low emissions. The updated components in the gas turbine are interchangeable from the existing 47MW rating. The increased power and improved efficiency are mainly obtained by improved compressor airfoil profiles and improved turbine aerodynamics and cooling air layout. The current paper is focused on the design modifications of the combustor parts and the combustion validation and operation experience.
The serial cooling system of the annular combustion chamber is improved using aerodynamically shaped liner cooling air inlet and reduced liner rib height to minimize the pressure drop and optimize the cooling layout to improve the life due to engine operation hours. The cold parts of the combustion chamber were redesigned using cast cooling struts where the variable thickness was optimized to maximize the cycle life. Due to fewer thicker vanes of the turbine stage #1, the combustor-turbine interface is accordingly updated to maintain the life requirements due to the upstream effect of the stronger pressure gradient.
Minor burner tuning is used which in combination with the previously introduced combustor passive damping results in low emissions for >50% load, which is insensitive to ambient conditions. The combustion system has shown excellent combustion stability properties, such as to rapid load changes and large flame temperature range at high loads, which leads to the possibility of single digit Dry Low Emission (DLE) NOx. The combustion system has also shown insensitivity to fuels of large content of hydrogen, different hydrocarbons, inerts and CO. Also DLE liquid operation shows low emissions for 50–100% load.
The first SGT-800 with 50.5MW rating was successfully tested during the Spring 2010 and the expected performance figures were confirmed. The fleet leader has, up to January 2013, accumulated >16000 Equivalent Operation Hours (EOH) and a planned follow up inspection made after 10000 EOH by boroscope of the hot section showed that the combustor was in good condition. This paper presents some details of the design work carried out during the development of the combustor design enhancement and the combustion operation experience from the first units.
Techno-Economic Evaluation of an IGCC Power Plant With Carbon Capture
Authors: Majoumerd Mohammad Mansouri , Assadi Mohsen , Breuhaus Peter 
Published: November 2013

Most of the scenarios presented by different actors and organizations in the energy sector predict an increasing power demand in the coming years mainly due to the world’s population growth. Meanwhile, global warming is still one of the planet’s main concerns and carbon capture and sequestration is considered one of the key alternatives to mitigate greenhouse gas emissions. The integrated gasification combined cycle (IGCC) power plant is a coal-derived power production technology which facilitates the pre-combustion capture of CO2 emissions.
After the establishment of the baseline configuration of the IGCC plant with CO2 capture (reported in GT2011-45701), a techno-economic evaluation of the whole IGCC system is presented in this paper. Based on publicly available literature, a database was established to evaluate the cost of electricity (COE) for the plant using relevant cost scaling factors for the existing sub-systems, cost index, and financial parameters (such as discount rate and inflation rate). Moreover, an economic comparison has been carried out between the baseline IGCC plant, a natural gas combined cycle (NGCC), and a supercritical pulverized coal (SCPC) plant.
The calculation results confirm that an IGCC plant is 180% more expensive than the NGCC. The overall efficiency of the IGCC plant with CO2 capture is 35.7% (LHV basis), the total plant cost (TPC) is 3,786 US$/kW, and the COE is 160 US$/MWh.
Turbulent Flame Speed as an Indicator for Flashback Propensity of Hydrogen-Rich Fuel Gases
Authors: Lin Y.-C. , Daniele S. , Jansohn P. , Boulouchos K. 
Published: November 2013

The turbulent flame speed (ST) is proposed to be an indicator of flashback propensity for hydrogen-rich fuel gases at gas turbine relevant conditions. Flashback is an inevitable issue to be concerned about when introducing fuel gases containing high hydrogen content to gas turbine engines, which are conventionally fueled with natural gas. These hydrogen-containing fuel gases are present in the process of the integrated gasification combined cycle (IGCC) with and without pre-combustion carbon capture, and both syngas (H2 + CO) and hydrogen with various degree of inert dilution fall in this category. More understanding on the flashback phenomenon for these mixtures is thus necessary in order to evolve the IGCC concept (either with or without carbon capture) into a promising candidate for clean power generation.
Compared to syngas, the hydrogen-rich fuel mixtures exhibit an even narrower operational envelope between the occurrence of lean blow out and flashback. When flashback occurs, the flame propagation is found to happen exclusively in the boundary layer of the pipe supplying the premixed fuel/air mixture to the combustor. This finding is based on the experimental investigation of turbulent, lean-premixed, non-swirled, confined jet flames for three fuel mixtures with H2 > 70 Vol. %. Measurements were performed up to 10 bar at fixed bulk velocity at the combustor inlet (u0 = 40 m/s) and preheat temperature (T0 = 623 K). Flame front characteristics were retrieved via OH-PLIF diagnostics, and turbulent flame speed (ST) was derived accordingly from the perspective of a global consumption rate.
Concerning the flashback limit, the operational range of the hydrogen-rich mixtures is found to be well represented by the velocity gradients prescribed respectively by the flame (gc) and the flow (gf). The former (gc) is determined as ST/(Le × δL0), where Le is the Lewis number and δL0 is the calculated thermal thickness of the one-dimensional laminar flame. The latter (gf) is predicted by the Blasius correlation for fully developed turbulent pipe flow, and it indicates the capability with which the flow can counteract the opposed flame propagation. Our results show that the equivalence ratios at which the two velocity gradients reach similar levels correspond well to the flashback limits observed at various pressures. The methodology is also found to be capable of predicting the aforementioned difference in the operational range between syngas and hydrogen-rich mixtures.
Evaluation of Reduced Kinetics in Simulation of Gasified Biomass Gas Combustion
Authors: Zhang Xiaoxiang , Munjat Nur Farizan , Jayasuriya Jeevan , Fakhrai Reza , Fransson Torsten 
Published: November 2013

It is essentially important to use appropriate chemical kinetic models in the simulation process of gas turbine combustion. To integrate the detailed kinetics into complex combustion simulations has proven to be a computationally expensive task with tens to thousands of elementary reaction steps. It has been suggested that an appropriate simplified kinetics which are computationally efficient could be used instead. Therefore reduced kinetics are often used in CFD simulation of gas turbine combustion. At the same time, simplified kinetics for specific fuels and operation conditions need to be carefully selected to fulfill the accuracy requirements. The applicability of several simplified kinetics for premixed Gasified Biomass Gas (GBG) and air combustion are evaluated in this paper.
The current work is motivated by the growing demand of gasified biomass gas (GBG) fueled combustion. Even though simplified kinetic schemes developed for hydrocarbon combustions are published by various researchers, there is little research has been found in literature to evaluate the ability of the simplified chemical kinetics for the GBG combustion. The numerical Simulation tool “CANTERA” is used in the current study for the comparison of both detailed and simplified chemical kinetics. A simulated gas mixture of CO/H2/CH4/CO2/N2 is used for the current evaluation, since the fluctuation of GBG components may have an unpredictable influence on the simulation results. The laminar flame speed has an important influence with flame stability, extinction limits and turbulent flame speed, here it is chosen as an indicator for validation. The simulation results are compared with the experimental data from the previous study [1] which is done by our colleagues. Water vapour which has shown a dilution effect in the experimental study are also put into concern for further validation. As the results indicate, the reduced kinetics which are developed for hydrocarbon or hydrogen combustion need to be highly optimized before using them for GBG combustion. Further optimization of the reduced kinetics is done for GBG and moderate results are achieved using the optimized kinetics compared with the detailed combustion kinetics.
Numerical Investigation of Improving Turbine Sealing Effectiveness Through Slot Width Modification of the Rim Seal
Authors: Zhang Jinghui , Ma Hongwei 
Published: November 2013

The hot gas in the main annulus of a gas turbine can ingest into the rotor-stator cavities through the rim seal clearance as a result of the interaction of the rotor and the stator disks and the external flow in the hot gas annulus. To prevent the turbine root region from being heated up, this ingestion has to be avoided almost completely. This paper introduces a new idea to improve turbine sealing effectiveness through slot width modification of the rim seal. Unsteady numerical simulations are performed with two different rim seal geometries at the design condition with different cooling flow rates. Both of the rim seal geometries are simple axial seal configurations. One is uniform slot rim seal geometry and is taken as the reference case. The other is a new kind of rim seal geometry with slot width modification. The clearance is bigger in the main flow path and smaller in the stator wake region keeping the area of the two kinds of rim seal surfaces equivalent.
The sealing air egress happens in the main path flow region and the ingestion happens in the stator wake region. Through comparing the results of the two kinds of rim seal geometries, it is found out that the contoured slot rim seal geometry can reduce the pressure in the cavity which leads to the decrease of the gas turbine loss. The inward radial velocity of the ingestion increases in the stator wake region and hence the axial seal gap has been reduced in this region. The time-averaged outward radial velocity decreases in the main flow region and becomes more uniform. Unsteady flow patterns in the rim seal region are compared for the two seal configurations. The sealing effectiveness is rapidly improved by using the contoured seal configuration. This work provides an idea to increase the sealing effectiveness and decrease the pressure in the cavity.
A Novel Gas Generator Concept for Jet Engines Using a Rotating Combustion Chamber
Authors: Jeschke Peter , Penkner Andreas 
Published: November 2013

A gas generator — consisting of a single-stage shrouded mixed-flow compressor without a diffusor, a rotating combustion chamber, and a vaneless single-stage shrouded centripetal turbine — is presented and analyzed here. All components comprise a coherent rotating device, which avoids most of the problems usually associated with small gas generators. In other words, the concept avoids all radial clearances, it is vaneless, shortens the combustion chamber, minimizes the wetted area and enables ceramic materials to be used, due to compressive blade stresses. However, the concept faces severe structural, thermal and chemical reaction challenges. All these features and their implications are discussed and their benefits for several jet engines are quantified, mainly by means of thermodynamic cycle calculations. An upfront CFD analysis identifies a polytropic compressor efficiency of around 95%. It is then demonstrated that the concept offers a thrust-to-weight ratio which is several times higher than the standard when incorporated into small UAV-type jet engines. It also enables an attractive multistage and dual-flow, but fully vaneless design option. Lastly, a thermal efficiency increase of several percentage points would be achieved, if the concept were to be realized in the (small) core of turbofans with highest overall pressure ratios and high bypass ratios.
In summary, the paper presents a gas generator approach which may be considered by designers of small jet engines like those used in UAV applications and it might even be a (challenging) long-term option for the small core engines encountered in future turbofans and turboprops.
Numerical Analysis of Three-Dimensional Corner Separation in a Linear Compressor Cascade
Authors: Gao Feng , Ma Wei , Boudet Jérôme , Ottavy Xavier , Lu Lipeng , Lebœuf Francis 
Published: November 2013

Nowadays, the internal flow in aircraft engine compressors can be quite accurately reproduced at design condition by the CFD tools. However, CFD generally fails to simulate some singular 3D phenomena, near off-design conditions, such as the corner separation. Studies have pointed out that the separation regions are often over-estimated when the flow state is far from design condition, owing to the turbulence model. Much work is devoted to improving the capability of the turbulence model in capturing the onset and the extent of the corner separation, which is desired in the designing procedures.
In this paper, steady RANS simulations are carried out in the same configuration as an experiment of Ma et al. These simulations are obtained with a high-precision in-house Navier-Stokes solver (Turb’Flow). With the same mesh, an unsteady simulation (URANS) is subsequently presented, in order to investigate the influence of a fluctuating inflow.
Attention is focused on a specific angle of attack of 4 degrees, for which the three-dimensional corner separation is clearly observed. For the unsteady simulation, unsteadiness is imposed through perturbations of the angle of attack at the inlet. The results of the steady and unsteady computations are analyzed and compared with those of the experiment. The time-averaged URANS results agree well with the RANS results. The fluctuating inflow does not show much influence on the mean performance of the compressor cascade. The onset of the corner separation occurs earlier in the simulations than in the experiment, considering the blade surface pressure and the passage velocity profiles. However, the cross-stream extent of the corner separation appears slightly under-estimated by CFD, according to the outlet total pressure losses and the passage velocity profiles. Finally, the URANS simulation allows to recover bi-modal PDFs, as observed in the experiment.
Effects of Simplified Platform Overlap and Cavity Geometry on the Endwall Flow: Measurements and Computations in a Low-Speed Linear Turbine Cascade
Authors: MacIsaac G. D. , Sjolander S. A. , Praisner T. J. , Grover E. A. , Jurek R. 
Published: November 2013

Incorporating the platform overlap and endwall cavity into the early stages of turbine CFD analyses is desirable from the perspective of accurately capturing the near endwall flow features. However, the overlap and cavity geometry increase the complexity of the computational domain making CFD meshes more difficult to generate and the CFD solutions more resource intensive. Thus, geometric approximations are often made to simplify the CFD analysis. This paper examines, experimentally, the secondary flows of a linear turbine cascade with three different platform overlap geometries, two of which incorporate geometric simplifications. These are then compared with the corresponding computations.
Experimental measurements were collected using a seven-hole pressure probe at a plane located 40% of the axial chord downstream of the trailing edge. Steady-state computational predictions were performed using ANSYS CFX 12.0 and employed the SST transition turbulence model.
The experimental results show that the presence of an upstream rim-seal creates a stronger passage vortex, relative to a flat endwall, resulting in larger integrated losses as well as higher levels of secondary kinetic energy and streamwise vorticity. Subtle differences in the strength of the passage vortex and the associated losses are observed for the simplified geometries in both the measured and predicted results. By examining the details of the cavity flow, a recirculation zone is identified which energizes the formation of the passage vortex. The effect of the recirculation zone may be attenuated or intensified by the rim-seal geometry. The paper concludes by addressing the validity and usefulness of the proposed platform overlap simplifications in design-oriented computations.
Evaluation of the Shortcomings of Current Engine Technology Stack-Up Methods and Suggestions for Improvement
Authors: Perullo Christopher A. , Kestner Brian K. , Tai Jimmy C. M. , Schutte Jeff S. , Mavris Dimitri N. 
Published: November 2013

There are currently numerous government and industry entities engaging in aviation technology development programs [1,2,3]. Due to the number of technologies being investigated there exists an understandable desire to rank technologies in order to identify the most beneficial ones. Historically, this has been done through the use of “waterfall” or technology stack-up charts [4].One purpose of such waterfall charts is to show the amount of benefit each technology provides to the integrated system. This approach is valid, and extremely useful, for verifying the modeling of such technologies; however, there are shortcomings in using a waterfall chart to assess the relative contribution of individual technologies to the overall system level benefit. This is due to several considerations that are not taken into account when developing conventional technology ranking charts. For example, the relative impact of each technology can be highly dependent on the order in which technologies are applied, the system the technology is applied to, the relative design changes that occur either before or after the technology is applied, and other technologies that are present on the system. In order to explore these characteristics this paper uses propulsion technologies since there are strong interactions between the various components of an engine. Engine technologies also commonly rely upon enabling technologies which provide less benefit, but without them the larger “bigger hitting” technologies are not feasible.
This research explores and quantifies the issues associated with several conventional methods of creating technology ranking charts. Propulsion technologies targeting both thermal and propulsive efficiency are applied to a baseline aircraft and engine configuration. Several conventional technology ranking and stack-up techniques are applied in order to evaluate how the relative impacts of individual technologies vary greatly depending on the assessment method. In all cases the same technology packages are applied such that the final benefit is the same, regardless of ranking method. It is suggested that a range of currently used ranking techniques all used to determine a more robust estimate of the impact.
Prediction of the NOx-Emissions of a Swirl Burner in Partially and Fully Premixed Mode on the Basis of Water Channel LIF and PIV Measurements
Authors: Sangl J. , Mayer C. , Sattelmayer T. 
Published: November 2013

The paper describes the development and validation of an efficient and cost effective method for the prediction of the NOx emissions of turbulent gas turbine burners in the early burner design phases which are usually focused on the optimization of the swirler aerodynamics and the fuel air mixing. As the method solely relies on non-reacting tests of burner models in the water channel it can be applied before any test equipment for combustion experiments exists.
In order to achieve optimum similarity of fuel air mixing in the water channel tests with engine operation the model is operated at the engine momentum ratio. During the LIF measurements the water flow representing the fuel is doped with fluorescent dye, a plane perpendicular to the length axis near the burner exit plane is illuminated with a 5W Ar-Ion Laser and the fluorescence is recorded with a video camera from downstream. From the video sequences the local probability density functions (PDF) of the dye concentration fluctuations are calculated from the data. Furthermore, the time mean velocity fields are measured with PIV. From the LIF data the PDFs of the local equivalence ratio are derived. Assuming flamelets, the NOx generation in the entire equivalence ratio range observed in the water channel tests is computed using the unstrained freely propagating one-dimensional flame model in Cantera and the GRI3.0 reaction scheme. Although neither flame stretch nor post flame NOx generation were considered the NOx values computed were in excellent agreement with the experimental data from perfectly premixed combustion experiments. The local time averaged NOx mole fraction is obtained by integrating the flamelet NOx over the mixture PDF. Finally the global NOx emission of the burner at the considered operating point is obtained by spatial integration considering the measured velocity field.
The method was validated using a conical swirl burner with two fuel injection stages, allowing the degree of premixedness to be adjusted over a wide range depending on the specific fuel injection scenario. For the case with fuel injection along the air inlet slots NOx values slightly above the minimum NOx limit for perfectly premixed combustion were computed. This is consistent with the emission measurements and indicates finite mixing quality of this injection method. In the partially premixed regime the configurations with potential for low NOx emissions were reliably identified with the LIF and PIV based water channel method. The method also shows the steep increase of the NOx emissions with decreasing degree of premixing observed in the experiments but quantitative predictions would have required a postprocessing of the data from the LIF mixing study with a higher spacial resolution than available.