bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measured Rotordynamic and Leakage Characteristics of a Tooth-on-Rotor Labyrinth Seal With Comparisons to a Tooth-on-Stator Labyrinth Seal and Predictions
Authors: Arthur Stephen P. , Childs Dara W. 
Published: August 2015

Rotordynamic and leakage data are presented for a see-through tooth-on-rotor (TOR) labyrinth seal with comparisons to a see-through tooth-on-stator (TOS) labyrinth seal. Measurements for both seals are also compared to predictions from XLLaby. Both seals have identical diameter and can be considered as relatively long labyrinth seals. The TOR seal has a length-to-diameter ratio of 0.62, whereas the TOS seal is longer and has a length-to-diameter ratio of 0.75. Both seals also differ by number of teeth, tooth height, and tooth cavity length. TOR labyrinth tests were carried out at an inlet pressure of 70 bar-a (1,015 psia), pressure ratios of 0.4, 0.5, and 0.6, rotor speeds up to 20,200 rpm, a radial clearance of 0.1 mm (4 mils), and three preswirl ratios. For comparison, TOS labyrinth tests were run at identical conditions as the TOR tests but for only one positive preswirl ratio.
TOR labyrinth measurements show a pronounced dependence of rotordynamic coefficients on rotor speed, especially when compared to prior documented TOS labyrinth seal tests run at a radial clearance of 0.2 mm (8mils). The TOR labyrinth cross-coupled stiffness is higher in magnitude and increases at a higher rate than that of the TOS labyrinth across all test speeds. However, the TOR labyrinth effective damping was determined to be greater due to higher measurements of direct damping. Measured leakage rates for the TOR labyrinth were approximately 5–10% less than the TOS labyrinth. XLLaby underpredicted the rotordynamic coefficients for both seals. However, as with measurements, it predicted the TOR labyrinth to have higher effective damping than the TOS labyrinth.
Transient Simulations of a T100 Micro Gas Turbine Converted Into a Micro Humid Air Turbine
Authors: Montero Carrero Marina , Ferrari Mario Luigi , De Paepe Ward , Parente Alessandro , Bram Svend , Contino Francesco 
Published: August 2015

Micro Gas Turbines (mGTs) have arisen as a promising technology for Combined Heat and Power (CHP) thanks to their overall energy efficiencies of 80% (30% electrical + 50% thermal) and the advantages they offer with respect to internal combustion engines. The main limitation of mGTs lies in their rather low electrical efficiency: whenever there is no heat demand, the exhaust gases are directly blown off and the efficiency of the unit is reduced to 30%. Operation in such conditions is generally not economical and can eventually lead to shutdown of the machine. To address this issue, the mGT cycle can be modified so that in moments of low heat demand the heat in the exhaust gases is used to warm up water which is then re-injected in the cycle, thereby increasing the electrical efficiency. The introduction of a saturation tower allows for water injection in mGTs: the resulting cycle is known as a micro Humid Air Turbine (mHAT).
The static performance of the mGT Turbec T100 working as an mHAT has been characterised through previous numerical and experimental work at Vrije Universiteit Brussel (VUB). However, the dynamic behaviour of such a complex system is key to protect the components during transient operation. Thus, we have modelled the Turbec T100 mHAT with the TRANSEO tool in order to simulate how the cycle performs when the demanded power output fluctuates. Steady-state results showed that when operating with water injection, the electrical efficiency of the unit is incremented by 3.4% absolute. The transient analysis revealed that power increase ramps higher than 4.2 kW/s or power decrease ramps lower than 3.5 kW/s (absolute value) lead to oscillations which enter the unstable operation region of the compressor. Since power ramps in the controller of the Turbec T100 mGT are limited to 2kW/s, it should be safe to vary the power output of the T100 mHAT when operating with water injection.
Development of High Order LES Solver for Heat Transfer Applications Based on the Open Source OpenFOAM Framework
Authors: Mangani Luca , Launchbury David Roos , Casartelli Ernesto , Romanelli Giulio 
Published: August 2015

The computation of heat transfer phenomena in gas turbines plays a key role in the continuous quest to increase performance and life of both component and machine.
In order to assess different cooling approaches computational fluid dynamics (CFD) is a fundamental tool. Until now the task has often been carried out with RANS simulations, mainly due to the relatively short computational time. The clear drawback of this approach is in terms of accuracy, especially in those situations where averaged turbulence-structures are not able to capture the flow physics, thus under or overestimating the local heat transfer.
The present work shows the development of a new explicit high-order incompressible solver for time-dependent flows based on the open source C++ Toolbox OpenFOAM framework. As such, the solver is enabled to compute the spatially filtered Navier-Stokes equations applied in large eddy simulations for incompressible flows.
An overview of the development methods is provided, presenting numerical and algorithmic details.
The solver is verified using the method of manufactured solutions, and a series of numerical experiments is performed to show third-order accuracy in time and low temporal error levels. Typical cooling devices in turbomachinery applications are then investigated, such as the flow over a turbulator geometry involving heated walls and a film cooling application. The performance of various sub-grid-scale models are tested, such as static Smagorinsky, dynamic Lagrangian, dynamic one-equation turbulence models, dynamic Smagorinsky, WALE and sigma-model. Good results were obtained in all cases with variations among the individual models.
A Simplified Analytical Approach for Calculating the Start-Up Time of Industrial Steam Turbines for Optimal and Fast Start-Up Procedures
Authors: Beer Wolfgang , Propp Lukas , Voelker Lutz 
Published: August 2015

New flexible operational regimes with fast start-ups and fast-changing load cycles for steam turbines require calculation procedures for determining optimal start-up times in order not to exceed the limits of thermal stress for the steam turbine parts.
This work presents a start-up time calculation for various kinds of industrial steam turbines. An analytical approach for estimating the optimal thermal load of a turbine from quasi-steady or steady condition is developed. The geometry of the respective turbine components, the changing of the steam parameters and heat transfer effects during the start-up procedure are taken into account while observing the respective material properties and stress limits. The temperature distributions of the respective turbine parts are calculated with a one-dimensional numerical algorithm of Fourier’s heat conduction equation. Three-dimensional influences of the geometry and of the the heat flux are considered analytically by adjusting the numerical solutions of elementary bodies (e.g. one-dimensional plate). The start-up time calculation is performed in small time steps to guarantee the stability of the numerical solution. The unsteady stress analysis for the start-up procedure does not uniquely identify one critical component. The calculation must be repeated for each time step to identify the component which limits the start-up gradient. Other boundary conditions, such as restricted speed ranges of the rotor with minimum transients and time for synchronization with the electrical grid, are considered by the model too and can further limit the start-up gradient and lead to slower start-up procedures. The one-dimensional calculation models were verified with a three-dimensional FEA of the casing and a two axis symmetrical FEA of the rotor. The results for the temperature distribution are presented and compared to the one-dimensional results.
The final result of the analytical approach for an optimized start-up time calculation is verified with two typical start-up calculations, one for a generator drive steam turbine and one for a mechanical-drive steam turbine.
Comparison of the Three-Dimensional Boundary Layer on Flat Versus Contoured Turbine Endwalls
Authors: Lynch Stephen P. , Thole Karen A. 
Published: August 2015

The boundary layer on the endwall of an axial turbomachine passage is influenced by streamwise and cross-stream pressure gradients, as well as a large streamwise vortex, that develop in the passage. These influences distort the structure of the boundary layer and result in heat transfer and friction coefficients that differ significantly from simple two-dimensional boundary layers. Three-dimensional contouring of the endwall has been shown to reduce the strength of the large passage vortex and reduce endwall heat transfer, but the mechanisms of the reductions on the structure of the endwall boundary layer are not well understood.
This study describes three-component measurements of mean and fluctuating velocities in the passage of a turbine blade obtained with a laser Doppler velocimeter. Friction coefficients obtained with the oil film interferometry method were compared to measured heat transfer coefficients. In the passage, the strength of the large passage vortex was reduced with contouring. Regions where heat transfer was increased by endwall contouring corresponded to elevated turbulence levels compared to the flat endwall, but the variation in boundary layer skew across the passage was reduced with contouring.
Axial Compressor Blade Failure, Design Modification, and its Validation
Authors: Hulme C. J. , Fiebiger S. W. , Szwedowicz J. 
Published: August 2015

Utilising a comprehensive design tool suite and in-house knowledge, the root cause analysis of High Cycle Fatigue (HCF) failures on the first stage compressor blade in a gas turbine (GT) engine is presented in this paper.
Based on the experience gained from the root cause analysis more reliable lifetime prediction for compressor blade design is possible. Tip timing measurements of blades in service have been evaluated to obtain valuable information about the real vibratory stress levels of the first stage compressor blades, to validate design methods, and to identify the failure mechanism. Metallurgical evaluation and testing of the failed parts were also used as part of the investigation. During the failure investigations the impacts of important damage mechanisms, not identified in the original design process, were determined. These damage mechanisms included, water droplet erosion of blades due to impingement on highly stressed regions of airfoil, mistuning within manufactured blade sets, and a very strong transient aerodynamic loading.
Considering the damage mechanisms, improved design methodologies have been used to design robust compressor blade sets. These have been validated in successful engine tests. Subsequent continued successful operation of new blade designs has been recorded in engines during an extended validation period.
Experimental and Numerical Investigation of Partial Admission of a Radial Turbocharger Turbine for Improved Off-Design Operation
Authors: Ilievski Mirko , Heidinger Frederic , Fuhrer Christopher , Schatz Markus , Vogt Damian M. , Challand Sebastian 
Published: August 2015

A new partial admission concept for turbocharger turbine operation at off-design is designed and investigated numerically and experimentally in a turbocharger test rig. This new concept is called MEDUSA (Multiple Exhaust Duct with Source Adjustment) and is based on a partial admission turbine system consisting of several separate flow channels that connect the cylinder of the engine and individual nozzle segments of the turbine. The turbine flow is adjusted by the chosen admission rate according to the available exhaust enthalpy. In the present study, a reference turbocharger has been equipped with a four segment partial admission system instead of its conventional Waste-Gate scroll.
The numerical results indicate similar loss mechanisms compared to an axial turbine stage, when partial admission is applied. Based on a stator design optimization, a design was chosen for manufacturing and testing on the turbocharger test rig. Despite the fact that the turbocharger efficiency at partial admission for the MEDUSA-system drops, a higher turbine expansion ratio can be achieved to obtain the same compressor operating point. These results indicate an enhanced use of the available exhaust enthalpy at part-load conditions, thus improving the turbocharger performance at low end torque engine speeds.
Admissible Roughness in Gas Turbines
Authors: Goodhand Martin N. 
Published: August 2015

Roughness below a certain, admissible level will not increase an aerofoil’s skin friction and thus will not impact on engine performance. In this paper a simple model is developed that demonstrates how this admissible roughness height changes through the engine. The model is determined by combining existing analytical models and is backed up by computational validation where necessary.
It is shown that, given a fixed inlet/exit stagnation temperature and pressure to a blade row, the admissible roughness height is only a weak function of chord Reynolds number and Mach number for typical gas turbine blades. The aerofoil geometry/duty is also shown to have little impact. This allows the model to give a general picture of where roughness matters, irrespective of the exact details of the flow conditions/blade geometries.
The model shows that the admissible roughness height decreases as the stagnation pressure increases. The lowest admissible roughness level occurs at the high pressure end of the compressor at sea-level; the admissible roughness increases as the stagnation pressure drops towards the front of the compressor. Turbines are also most sensitive to roughness close to the combustor, but even there the admissible roughness will be around three times greater than at the rear of the compressor.
The Limitations of “Ra” to Describe Surface Roughness
Authors: Goodhand Martin N. , Walton Karl , Blunt Liam , Lung Hang W. , Miller Robert J. , Marsden Reg 
Published: August 2015

Current criteria used to determine whether rough surfaces affect skin friction typically rely on a single amplitude parameter to characterize the roughness. The most commonly used criteria relate the centreline averaged roughness, Ra, to an equivalent sandgrain roughness size, ks. This paper shows that such criteria are oversimplified and that Ra/ks is dependent on the roughness topography, namely the roughness slope defined as the roughness amplitude normalized by the distance between roughness peaks, Ra/λ.
To demonstrate the relationship, wake traverses were undertaken downstream of an aerofoil with various polished surfaces. The admissible roughness Reynolds number (ρ1u1Ra/μ1) at which the drag rose above the smooth blade case, was determined. The results were used to demonstrate a 400% variation in Ra/ks over the roughness topographies tested.
The relationship found held for all cases tested, except those where the roughness first initiated premature transition at the leading edge. In these cases, where the roughness was more typical of eroded aerofoils, the drag was found to rise earlier.
Film Cooling Modelling for Gas Turbine Nozzles and Blades: Validation and Application
Authors: Andrei Luca , Innocenti Luca , Andreini Antonio , Facchini Bruno , Winchler Lorenzo 
Published: August 2015

The use of Computational Fluid Dynamics (CFD) for modern turbine blade design requires the accurate representation of the effect of film cooling. However, including complete cooling hole discretization in the computational domain requires a substantial meshing effort and leads to a drastic increase in the computing time. For this reason, many efforts have been made to develop lower order approaches aiming at reducing the number of mesh elements and therefore computational resources. The simplest approach models the set of holes as a uniform coolant injection, but it does not allow an accurate assessment of the interaction between hot gas and coolant. Therefore higher order models have been developed, such as those based on localized mass sources in the region of hole discharge.
It is here proposed an innovative injection film cooling model (FCM), embedded in a CFD code, to represent the effect of cooling holes by adding local source terms at the hole exit in a delimited portion of the domain, avoiding the meshing process of perforations. The goal is to provide a reliable and accurate tool to simulate film-cooled turbine blades and nozzles without having to explicitly mesh the holes.
The validation campaign of the proposed model is composed of two phases. During the first one, results obtained with the film cooling model are compared to experimental data and to numerical results obtained with the full meshing of the cooling holes on a series of test cases, ranging from single row to multi row flat plate, at varying coolant conditions (in terms of blowing and density ratio). Though details of the flow structure downstream of the holes cannot be perfectly captured, this method allows an accurate prediction of the overall flow and performance modifications induced by the presence of the cooling holes, with a strong agreement to complete hole discretization results. In the second phase, a complete film-cooled vane test case has been studied, in order to consider a real injection system and flow conditions. In this case, film cooling model predictions are compared to an in-house developed correlative approach and full CHT 3D-CFD results.
Finally, a comparison between film cooling model predictions and experimental data was performed on an actual nozzle of a GE Oil & Gas heavy-duty gas turbine as well, in order to prove the feasibility of the procedure.
The presented film cooling model proved to be a feasible and reliable tool to evaluate adiabatic effectiveness, simplifying the design phase avoiding the meshing process of perforations. Also, refining the mesh near the hole exit, FCM results well approximate the solution coming from a full CHT calculation.
Performance Testing of Centrifugal Compressors: Schultz Compressibility Factors
Authors: Taher Matt 
Published: August 2015

ASME PTC-10 [2009] recognizes inaccuracies involved in using the generalized charts to calculate Schultz compressibility factors for real gas compression. However, it neither addresses a method to develop the compressibility factors, nor does it specify when to use calculated compressibility factors rather than using generalized values. Using inaccurate generalized values for Schultz compressibility factors may lead to erroneous calculation of polytropic exponents and polytropic work.
This paper employs the LKP equation of state to directly calculate Schultz compressibility factors for a mixture of hydrocarbons typically found in natural gas. The results are compared with the values of compressibility factors from the generalized compressibility charts.
Engineering Approach for LCF Assessment of Porous Alloys
Authors: Bednarz Piotr , Szwedowicz Jaroslaw 
Published: August 2015

Most components used in gas and steam turbines are metallic parts produced by either casting or forging processes. Although process control works to eliminate defects, there can be variation in micro-porosity from component to component. Previously this micro-porosity was only able to be detected destructively using metallography. Using Computer Tomography (CT), one can find voids in the range of a few tenths of a millimeter and know the location of the voids with high precision. This allows one to map the defects present in each component onto the stress and temperature fields for that component. However, there is not yet universal agreement upon a consistent method to evaluate the effect of these small porosities on a component’s lifetime. Having a robust analysis tool to understand the impact of micro-porosity would decrease development costs, decrease the time to bring a product to market, and increase the likelihood of failure-free operation.
This paper presents an approach using equivalent LCF material properties which avoids the need to explicitly model the morphology of the microstructure in the region of the micro-porosity. The homogenization methodology calculates new LCF curves depending on porosity ratios in material. This approach uses Morrow’s correlation factor of LCF cycles to crack initiation regarding energy amount dissipated in stable cycling (shake-down) and ultimate strain energy under monotonic loading. The paper generalizes Morrow’s postulate and formulates the hypothesis that energy stored and dissipated in the material under shake-down conditions corresponds directly to the number of LCF cycles to crack initiation. The paper demonstrates that the reduction of LCF life based on the porosity ratio agrees well with the experimental results. These results also show that the methodology is very sensitive to the void orientation and loading direction.
Gasification of Agro-Industrial Wastes for Electricity Cogeneration
Authors: Sarmiento A. L. E. , Maya D. M. Y. , Chejne F. , Lora E. E. S. 
Published: August 2015

The purpose of this paper is to report studies on agricultural residual biomass gasification to power cogeneration. The classification was determined by availability and feedstock for thermochemical conversion of waste materials of flower industry in Colombia. Firstly, it was made an inventory of the main species of flowers produced, they were evaluated from the point of view of energy proximate and ultimate analysis of the available biomass[1]–[4] [5].
As a result of this work, the waste types with higher residual biomass per unit area were classified, they generate on average 665.59 Kg/ha of dry residual biomass. The elemental analysis (CHON) was expressed to be: C:35,47%, H:4,50%, O:52,24 % and N:2,291% and a calorific value of 3248,30 cal/kg. Experimental tests were conducted in a gasification updraft reactor using air as gasifying agent, steam and a mixture of air and steam at 850°C. The yields and gas composition were analyzed, in this case the values of CO, H2, CO2, N2 and CH4 have been on average 21.9%, 44.8%, 24.4%, 5.9% and 3.1% respectively [1], [2], [4], [6]–[10]. With the experimental test data was fed zero dimensional model in Aspen Plus® software, which highlights that 20% of energy from biomass producer gas is carried to later becoming electricity, it concludes that for each kilogram of biomass with 11% humidity fed to the process will provide 0.66 kW of electric power to the motor generator.