bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exhaust Volume Dependency of Turbocharger Turbine Design for a Heavy Duty Otto Cycle Engine
Authors: Anton Nicholas , Genrup Magnus , Fredriksson Carl , Larsson Per-Inge , Erlandsson-Christiansen Anders 
Published: August 2017

This study is considering turbocharger turbine performance at “on-engine” conditions with respect to turbine design variables and exhaust manifold volume. The highly unsteady nature of the internal combustion engine will result in a very wide range of turbine operation, far from steady flow conditions. As most turbomachinery design work is conducted at steady state, the influence of the chosen turbine design variables on the crank-angle-resolved turbine performance will be of prime interest. In order to achieve high turbocharger efficiency with the greatest benefits for the engine, the turbine will need high efficiency at the energetic exhaust pressure pulse peak.
The starting point for this paper is a target full load power curve for a heavy duty Otto-cycle engine, which will dictate an initial compressor and turbine match. Three radial turbine designs are investigated, differing with respect to efficiency characteristics, using a common compressor stage. The influence of the chosen turbine design variables considering a main contributor to unsteadiness, exhaust manifold volume, is evaluated using 1D engine simulation software. A discussion is held in conjunction with this regarding the efficiency potential of each turbine design and limitations of turbine types.
The Fabrication, High Heat Flux Testing, and Failure Analysis of Thermal Barrier Coatings for Power Generation Gas Turbines
Authors: McCay Mary Helen , Hsu Pei-feng , Croy D. Edward , Moreno David , Zhang Mengqi 
Published: August 2017

Thermal barrier coatings (TBC) are used to protect the hot components of gas turbines engines to enhance thermal efficiency and component service life. The coating, based on yttria stabilized zirconia, is used in this study. In this paper high heat flux testing with a temperature gradient across the coating thickness of TBC coated coupons is presented. These buttons are subject to precisely-controlled laser heating on the top side and compressed air cooling on the bottom side. Analysis of the thermal conductivity change with respect to heating time and peak temperature, failure assessment, and metallurgical examination are also presented. Some important results of using this method of testing are: definition of the service time vs temperature relationship for TBC lifetime; improved durability of TBCs under severe environmental conditions; determination of effective steady-state sintering conductivity; identification of onset of coating cracking and delamination; adjustable peak temperature, automated and accelerated thermal cycling, etc. This leads to faster testing turn-around for TBC development.
Two different types of heating modes can be employed: soak test and cycle test. In soak tests, coated coupons are subjected to steady laser heat flux for up to 12 hr. In cycle tests, the laser heat flux is on for one hour and then off to cool the coated coupons for three minutes. Coupon top surface temperatures from 1200 to 1528°C are maintained in various test cases. At the highest temperature test cases, delamination of TBC (cycle test) and surface crack (soak test) are observed. All key measurements (temperatures, laser power to coupon, compressed air flow rate, etc.) are recorded per second. The normalized thermal conductivity can be computed in real time or processed after the test. It is found that the normalized thermal conductivity increases in the first few hours or cycles of heating and it either reaches a near steady state value or decreases due to surface cracking or delamination in the later state of testing.
Identification of Vibrational Resonances of Centrifugal Compressor and Radial Turbine Impellers Interacting With General Pressure Pulsations
Authors: Luo Zhusan , Stanko Mike , Schwarz Carl , Wang Zhihong Annie 
Published: August 2017

Vibrational resonances of centrifugal compressor and radial inflow turbine impellers are usually identified using either Kushner’s or Singh’s parametric equations in product design and failure analysis. These equations were developed based on positive work accumulated within a certain time period. However, some resonances observed in simulation and testing cannot be understood with those resonance equations.
This paper presents an alternative method to derive vibrational resonance conditions. A new model of general pressure pulsations is developed by taking into account the disturbances resulting from stationary obstacles and rotating blades. Analytical solutions of the forced vibration responses of a rotating disk subjected to different pressure pulsations are then formulated. From the forced responses, both Kushner’s and Singh’s equations can be derived. They can further prove to be equivalent though they focus on different physics.
A general resonance condition is derived from the analytical solutions. This condition is a necessary condition, i.e. all resonances must meet this condition while a system following the condition may or may not be in resonance, depending upon excitation sources. It is noticed that the excitation sources could be related to harmonics due to stationary obstacles, harmonics with combined harmonic orders, or even harmonics to be understood. This general resonance condition can hence provide more “possible resonance points” and assist identifying resonances from more representative modes and more excitation sources. It has been validated by predicting vibrational resonances observed in three centrifugal compressors. This condition has also been successfully employed in the failure analysis and design modification of a radial inflow turbine impeller.
Erosion Properties of Ceramic Composite Material Based on Nano-Mullite Whisker and Zirconia-Toughened Alumina
Authors: Erazo Fabian , Robertson Taylor , Huang Xiao , Kearsey Rick , Yang Qi 
Published: August 2017

The improvement of bulk ceramic properties through the addition of a secondary or even tertiary phase is a field of research that has been actively pursued since the mid twentieth century. This pursuit has become more relavent with the adoption of ceramic phases to protect structural components within the hotpath of gas turbines. Improving the properties of these ceramic coatings and tiles has the potential of reducing catastrophic damage events leading to an overall reduction in unplanned maintence and downtime.
To date, Several approaches have been undertaken to improve the physical properties of these ceramics including preferential microstructural grain growth and doping to develop metastable crystal phases. This paper examines the effect of whisker additions to a mechanical mixture of oxide ceramics on the erosion properties. The baseline structure is a mechanical mixture of zirconia and alumina particles in the ratio of 89.8vol% alumina to 10.2vol% partially stabalized zirconia. A ratio of 20.0vol% mullite whiskers is incorporated into the structure as a toughening agent. The mullite whiskers are grown using a molten salt method. The overall structural composition is 20.0vol% mullite whiskers, 8.2vol% partially stabilized zirconia, and 71.8vol% alumina. This whisker toughened material is compared to a baseline 89.8vol% alumina 10.2vol% zirconia ceramic.
Erosion tests were conducted using a 50 μm diameter alumina erodant with a velocity of 104 m/s. Impingement angles of 30°, 60° and 90° were examined to determine the effect of whisker additions at steeper attack angles. Despite the increased hardness, tensile strength and fracture toughness, whisker-enhanced zirconia-toughened alumina has shown similar erosion rate as non-reinforced ZTA at 30° ad 90° and much higher erostion at 60°. It can be surmised that whisker-enhanced toughening of ceramics has little positive effect on the erosion resistance of ceramics at room temperature and is potentially harmful. Microstructure analysis results are also presented within to illustrate the erosion material removal mode under different conditions.
Computational and Experimental Study of a Platinum Thin-Film Based Oil Condition and Contamination Sensor
Authors: Sridhar V. , Chana K. S. , Singh D. 
Published: August 2017

Lubrication systems form an integral part of aircraft and automobiles. Failure of lubrication systems can occur due to contamination or degradation of oil which can lead to excessive wear and failure of rotating components. This leads to unnecessary downtime and increase in maintenance costs. Oil contamination occurs when metallic or non-metallic particles are produced due to wear of the machine components such as bearings, gears etc. and these particles may not be always captured by the filtering system that are already in the lubrication system. Hence, the particles can clog oil paths and accelerate the wear of moving parts. In addition to this, variations in thermal stresses causes oxidation and thereby degradation of the oil. Contamination can also be in the form of liquids such as water droplets or fuel from heat exchangers. Currently, on-line oil condition monitoring systems use sensors that are based on eddy current, optical, capacitive to detect contamination in oil for preventive maintenance especially for aircraft engine bearings, aviation gearboxes etc. These sensors have some major drawbacks: prone to surface contamination, non-linearity, insensitive to detect extremely small particulates or false detection such as trapped bubbles.
A new sensor based on platinum thin film heat transfer gauges has been developed at the University of Oxford that works on the principle of measuring the change in thermal product of the material that is in contact. The sensor is able to detect any form of contamination in oil and can be used for both off-line and on-line condition monitoring. The sensor is found to be quite sensitive and can detect extremely small concentrations of contaminants of the order 0.01 % by volume. This paper presents a detailed computational and experimental study carried out to test contamination in oil at room temperatures. The three-dimensional, time-dependent, implicit numerical simulations were carried out using the commercial computational fluid dynamics package FLUENT®. The simulation incorporates conjugate heat transfer to obtain the heating curves of the sensor with and without contamination. This was necessary to understand the range of the sensor and also to study the variations in heat transfer from the sensor to the material that is in contact with the sensor, which otherwise would not have been possible through experiments. The numerical heating curves are then compared with experimentally obtained heating curves. The comparison showed that the numerical and experimental data to agree well and are within 1 %.
Micro-Gas Turbine Feed With Natural Gas and Synthesis Gas: Variation of the Turbomachines’ Operative Conditions With and Without Steam Injection
Authors: Renzi Massimiliano , Caligiuri Carlo , Rossi Mosè 
Published: August 2017

In this work, the performances of a 100 kW Micro Gas Turbine (MGT) fed by Natural Gas (NG) and three different biomass-derived Synthesis Gases (SGs) have been assessed using a MATLAB® simulation algorithm. The set of equations in the algorithm includes the thermodynamic transformations of the working fluid in each component, the performance maps that describe the turbomachines’ isentropic efficiencies and pressure ratios as a function of the reduced mass flow rate and the reduced rotational speed, the performance and the pressure losses in each component, as well as the consumption of the other auxiliary devices.
The electric power output, achieved using SGs, turns out to be lower or higher with respect to the one produced with the NG, depending on the fuel Lower Heating Value (LHV) but also largely on the variation of the working fluid composition.
In this work, the effect of the steam injection on the MGT performance characteristics has been also investigated. Steam injection allows to obtain higher power and efficiencies using both NG and SGs at the rated rotational speed, mainly thanks to the increase of the turbine enthalpy drop and the reduction of the compressor consumption. Attention must be paid to the risk of the compressor stall, especially when using SGs, as the mass flow rate processed by the compressor decreases significantly.
Moreover, another advantage of adopting the steam injection technique lies in the increased flexibility of the system: according to the users’ needs, the discharged heat can be exploited to generate steam, thus to enhance the electric performances, or to supply thermal power.
Uncertainty Quantification of Conjugate Heat Transfer of a Cooled Turbine Vane: Roughness Effect
Authors: Shi Wei , Li Weihong , Shi Bo , Li Xueying , Ren Jing , Jiang Hongde 
Published: August 2017

HP turbine usually works in complex operation conditions and subjects to strong temperature variability and thermal gradients. For these reasons, some small variations caused by manufacturing process and operation conditions will yield great effect on the heat transfer performance and the life of hot components.
UQ is a state of the art that seeks to provide a framework for calculating the effects of input parameter uncertainty on model output variables. This study presents an investigation of the uncertainty quantification (UQ) of conjugate heat transfer of a typical high load HP cooled turbine vane, considering the influence of total inlet temperature, turbulence intensity and different surface roughness level. The non-intrusive Probabilistic Collocation Method, integrated with sparse grid quadrature has been used in the UQ analysis. The scaled sensitivity analysis is also carried out to assess the influence of each input uncertainty on the output response.
The UQ analysis implies that the increasing of surface roughness will enlarge uncertainty of metal wall temperature. As a result, it needs to amplify the safety margin coefficient in order to assess the turbine guide vane surface temperature distribution and service life.
Global Three-Dimensional Surrogate Modeling of Gas Turbine Aerodynamic Performance
Authors: Leylek Zafer , Neely A. J. 
Published: August 2017

Turbine blade aerodynamic performance can be accurately predicted using one-dimensional mean-line and two-dimensional through-flow solvers. These predictions have been achieved by coupling one and two-dimensional ideal flow equations with blade aerodynamic loss and flow deviation angle models. These loss and deviation models are largely generated using classical cascade testing which have limitations and constraints. These limitations are associated with testing in general and include scope, time, resources, geometric and operating parameter space, data scatter and uncertainty. The models largely ignore interaction effects and can be subjective. The loss and deviation models also do not incorporate blade features associated with modern turbine blades. The objective of this paper is to study the feasibility of conducting these experiments numerically using three-dimensional turbine blade and constructing global blade performance and loss models.
The study looks at a number of competing surrogate modeling techniques and evaluates their performance for optimum blade loss and deviation prediction. The effect of Reynolds number, performance parameter definition, operating condition specification along with the use of extended parameters are investigated to further enhance the surrogate models. The performance map generated using the optimized surrogate models is then validated using a 1.5 stage axial turbine. The results show that numerically generated surrogate models can be used to accurately predict the CFD based axial turbine performance.
Analysis on Solid Particle Erosion in the Governing Stage of a High-Parameter Steam Turbine
Authors: Hu Peng-fei , Li Yong , Cao Li-hua , Zhang Tao 
Published: August 2017

The solid particle erosion (SPE) of flow passage is a universal problem in modern high-parameter steam turbines. With the continuous improvement of the working parameters of the steam turbine, the problem of SPE is becoming more serious. This problem is caused by the ferric oxide exfoliations carried by steam from the inner wall of the boiler tube into the steam turbine flow passage, causing the stator blades, the rotor blades, and the shroud to be eroded under impingement and scuffing failure. The SPE cannot only destroy the blade profile, increase the roughness of the blade surface, and affect the aerodynamic performance of the blade, but it can also shorten the maintenance cycle, prolong the maintenance downtime, and even increase the cost for steam turbine maintenance thereby reducing the unit efficiency and safety.
In order to simulate SPE in the governing stage of a high-parameter steam turbine, this study adopts the Lagrange method and the Finnie erosion model. The motion characteristics of five different kinds of solid particle, including the solid particle trajectory, are thoroughly analyzed. The regulation of the erosion distribution in the radial and axial directions to the stator and rotor blades is studied to present the mechanism of SPE.
Simulated results show that before their collision with the blades, the particles of the small diameters flow with the main stream, and their trajectories are close to the steam streamlines. By contrast, the particles of the large diameters are hardly influenced by the external factors, and their trajectories are close to the straight line. The SPE distribution of the stator and rotor blades varies with the particle diameter. The eroded area in the stator blade is mainly located at the leading edge and the pressure surface, particularly the mid-rear part of the pressure surface, whereas no eroded area can be observed in the suction surface. The small particles greatly affect the erosion distribution of the stator blade. The eroded area in the rotor blade is primarily at the mid-rear part of the pressure surface and the suction surface, which is close to the leading edge. The eroded area takes on a typical slop shape, and the erosion position has an obvious upward trend.
The proposed research reveals both the motion characteristics of the solid particles and the distribution regulation of the SPE in the steam turbine flow passage. The analysis results provide references for the governing stage of a high-parameter steam turbine to prevent SPE.
Impact of Vortex Produced by a Novel Curve-Micro Vortex Generator on Secondary Flow in Compressor Cascade
Authors: Ma Shan , Chu Wuli , Zhang Haoguang , Li Lanpan , Lang Jinhua 
Published: August 2017

The performance of compressor cascade is considerably influenced by secondary flow. An extensive experimental study of vortex generator (VG) applied on axial compressor was conducted by many scholars, in order to control these effects. Particularly, MVG is one of the hot researches in present to restrain secondary flow. On the foundation of research experience finished by the former scholars, a new Curve-micro vortex generator (C-MVG) was proposed in this paper. In order to investigate the effect of C-MVG on secondary flow in low-Mach number cascade, the present was carried out on a high-loaded axial compressor cascade with incoming flow of Ma<0.3. The experiment of baseline was conducted at a low speed (incompressible) cascade wind tunnel. The C-MVGs were placed on the end-wall at a distance of 7% chord length ahead of passage and a pitch distance of 26 mm from the leading edge of suction side. 8 cases with different spacing and θVGs were calculated. The height of all the C-MVGs were 5 mm and each case was comprised of 3 vanes.
At design and stall incidence angle (−1 deg and 8 deg), the total pressure loss coefficient averaged by mass-flow (Loss) in the outlet was analyzed with numerical method of k-omega turbulence model. Different combinations of C-MVGs were compared. Results show that the Loss in 140% axial chord length (Ca) after leading edge was increased on design condition. At 8 deg incidence angle, all cases could delay the inception of separation and decrease loss. The case VGθ3 showed the highest loss reduction benefit of 7.3%, which indicated that C-MVGs could control the large separation area effectively.
Development and Validation of a Novel Synthetic Blade Model for Axial Flow Fans in Unsteady CFD
Authors: Bonanni Tommaso , Corsini Alessandro , Delibra Giovanni , Volponi David 
Published: August 2017

Here we present a Synthetic Blade Model (SBM) for axial flow fans, derived from Actuator Disk and Actuator Line theories. This new approach is able to model the momentum exchange between the fan and the fluid by adding source terms into momentum equation, like an actuator disk. However, the model accounts for the position of the blades, their rotation and the non-uniform distribution of deflection capability in the blade-to-blade passage, like in an actuator line model.
This approach is derived, described and validated against available data on a reversible tunnel and metro fan.
Metamodel-Assisted Optimization of a High-Lift Low Pressure Turbine Blade
Authors: Bigoni Fabio , Maffulli Roberto , Arts Tony , Verstraete Tom 
Published: August 2017

The scope of this work is to perform a single-objective optimization of the high-lift and aft-loaded T2 low pressure turbine blade profile previously designed at the von Karman Institute for Fluid Dynamics (VKI). At correct engine Mach and Reynolds numbers and for a uniform inflow at low turbulence level, a laminar separation bubble occurs in the decelerating part of the suction side.
The main goal of the optimization is to obtain a high-lift and aft-loaded blade characterized by lower aerodynamic losses with respect to the original profile.
The optimization uses a metamodel-assisted Differential Evolution algorithm, with an Ordinary Kriging metamodel performing the low-fidelity evaluations and Numeca FINE/Turbo for the high-fidelity ones.
The numerical results relative to the optimized profile are compared with those obtained for the baseline profile, in order to highlight the improvements on the blade aerodynamic performance coming from the optimization process.
Nodal Diameter-Dependent Modal Damping Method for Nonlinear Blade Dynamics Prediction Considering Variable Rotational Speed
Authors: Heinze Torsten , Panning-von Scheidt Lars , Wallaschek Jörg , Hartung Andreas 
Published: August 2017

Since industrial large-scale models of friction-damped bladed disks for vibration analysis usually comprise numerous degrees of freedom, reduction techniques are required to facilitate the application of frequency and time domain solution methods. Common approaches utilize modal representations of the vibrational behavior considering either fixed, free, or hybrid interface conditions as well as elastic response to either unitary displacements or unitary forces acting on interface degrees of freedom to ensure static completeness. These modes serve as a basis for reduced description of the equation of motion. Often global damping concepts such as Rayleigh damping or hysteretic damping are applied afterwards. If mode-wise damping ratios are known, these can be introduced using modal damping formulation. Provided that variable rotational speed-dependence of the structure is of interest, an expanded speed-independent multi-model reduction basis is needed.
The aim of this paper is to provide a nodal diameter-dependent modal damping approach to account for such damping information in case of variable rotational speed. Therefore, basis transformations between surrogate and multi-model basis are required. Attention will be paid to dealing with linearly dependent bases. Periodic solutions induced by multi-harmonic excitation are sought using a harmonic balance approach. The influence of multi-harmonic excitation onto the vibrational behavior is analyzed, serving as a starting point for nodal diameter-dependent modal damping investigations. Accuracy and scope of the method are finally discussed.