bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Artificial Neural Network Based Gas Path Diagnostics on Gas Pipeline Compressors
Authors: Suleiman Suleiman M. , Li Yi-Guang 
Published: January 2021

Abstract
This paper presents the development of an artificial neural network (ANN) Gas Path Diagnostics (GPD) technique applied to pipeline compression system for fault detection and quantification. The work detailed the various degradation mechanisms and the effect of such degradations on the performance of natural gas compressors. The data used in demonstrating the ANN diagnostics is so derived using an advanced thermodynamic performance simulation model of integrated pipeline and compressor systems, which has embedded empirical compressor map data and pipeline resistance model. Implantation of faults within the model is in such a way to account for faults degradations caused by fouling, erosion and corrosion, of various degrees of severities, to obtain wide range of corresponding simulated “true” measurements. In order to account for uncertainties normally encountered in field measurements, Gaussian noise distribution was combined with simulated true measurements, which depends on the instrument’s tolerances. Furthermore, since judicious measurements selection are crucial in ensuring flawless GPD predictions, a sensitivity and correlation analysis of the available measurements revealed that discharge temperature, rotational speed and torque are the most effective measurements for the diagnostics with acceptable degrees of accuracies. The measurements observability technique is a novel approach in pipeline compressor diagnostics. Analytical case studies of the developed method show that, a selected ANN architecture can detect and quantify faults related to degradation in efficiency and flow capacities in the presence of instrument error, varied operational and environmental conditions.
Measured Influence of Clearance and Eccentricity on Brush Seal Leakage Characteristics
Authors: Thorat Manish R. , Bauer Brian 
Published: January 2021

Abstract
Brush seals are used in turbomachinery for reduced leakage as compared to conventional seals such as labyrinth seals. Early applications tended to favor having a line-to-line to a slight interference fit of the bristles to the shaft, but more recent applications have favored the use of a slight initial clearance fit for the purpose of reducing bristle wear. In these brush seals with clearance, the phenomenon of bristle blow-down largely negates the leakage degradation due to clearance, with bristles bending to reduce the clearance gap. This paper presents experimental results for a 10.5 inch bore brush seal with 0.0028 inch bristle diameter. Bristle blow-down is characterized with measurements at three different clearances then compared to a calibrated brush seal leakage model.
Tolerances in brush installation may lead to a brush seal bore that is eccentric to the rotor. The influence of this seal eccentricity on measured leakage performance is also characterized in the paper. Seal eccentricities up to 55% of brush fence height are tested. Effective clearances for eccentric operation are estimated from the measurements.
Brush seals are described as unidirectional seals because the bristles have a lay angle in the direction of rotation. This paper also investigates the influence of rotation direction on measured leakage performance of brush seal. This influence is characterized by non-pressurized reverse rotation operation and measurement of leakage performance prior to and after reverse rotation operation.
Numerical Investigation Into Fully and Partially Wetted Disk Geometries With Relevance to Intershaft Hydraulic Seals
Authors: Warusevitane Achinie , Johnson Kathy , Ambrose Stephen , Walsh Mike , Young Colin 
Published: January 2021

Abstract
Civil aero-engines contain two or three shafts that are supported by bearings. Seals are required both between pairs of rotating shafts and between static elements and shafts. Seals located between two co/contra rotating shafts within the bearing chamber are known as intershaft seals and are typically classified as either hydraulic or oil backed. This paper focuses on research relevant to intershaft hydraulic seals.
A hydraulic seal is formed by a seal fin on the inner shaft immersed in an annulus of oil in the outer shaft where the oil in the annulus is centrifuged outwards by the radial pressure gradient. Once formed a hydraulic seal does not allow air to flow across the seal and any pressure difference across the seal creates different oil levels either side of the fin. Despite their reliable operation with zero leakage, the application of hydraulic seals is restricted due to temperature limitations, oil degradation and coking. Research and development of the next generation of hydraulic seals needs to focus on addressing these issues so that the seals can be utilized in hotter zones in future engines. Understanding of the detailed fluid dynamic behaviour during hydraulic seal operation is relatively limited with very little published data. There is an acknowledged need for improved knowledge and this is the context for the current study.
The ability to accurately computationally model hydraulic seals is highly desirable. Prior experimental and analytical investigations into fully and partially wetted rotating disks have been used to aid understanding of the performance and flow characteristics of hydraulic seals as there are many geometric and operational similarities. These fundamental experimental investigations in the literature provide validation data that allows the authors to establish a CFD modelling methodology.
This paper initially compares the flow characteristics of a fully wetted rotating disk against experimental results available in literature including the radial and tangential velocity components. This paper subsequently investigates the flow characteristics of a partially wetted disk by examining the effect on the angular velocity of the fluid core with varying engagement and spacing ratios for two flow regimes.
Characterising Mixing and Soot Production Using a Lagrangian Statistical Method
Authors: Kampanas Vasileios , Williams Maxwell , Garmory Andrew 
Published: January 2021

Abstract
An understanding of fuel-air mixing, along with the link between turbulent fluid flows and soot production is vital for the design of an efficient, low emissions gas turbine combustor. This paper uses a Lagrangian statistical method to investigate the time histories of mixing hence and soot development for massless parcels tracked within an LES calculation. This provides the advantage of investigating soot development using an inexpensive post-processing technique. The method comprises tracking massless parcels through the flow and recording the local temperature and composition at the parcel location, as well as the age of the parcel. This can be used to give statistical information about various aspects of mixing and soot production, such as distributions of mixture fraction or residence times. The history for each parcel can then be used in a postprocessing step to predict the soot development in time for that parcel path. This has been used to compare Large Eddy Simulations (LES) of reacting flows in both a laboratory aero-engine model combustor and a geometry representative of an annular sector from an aircraft engine combustor. It was found, that when normalized by a reference time scale based on combustor length and bulk velocity, the residence times for the annular sector were considerably shorter and mixture fraction distributions wider. This was due to a much higher chance of parcels being recirculated within the primary zone of the laboratory combustor. Further analysis of the annular combustor sector showed that very different mixing is found between the oxidation ports on the centre of the sector compared to those at the edge. The instantaneous mixing is seen to be less effective for those ports at the edge of the sector and this leads to higher soot levels in these regions.
Experimental Study on Heat Transfer Characteristics of Array Impingement With Initial Cross-Flow
Authors: Zhu Tian-liang , Xu Wei-jiang , Shi Xiao-yu , Su Bo , Lu Fei 
Published: January 2021

Abstract
In order to increase the thermal efficiency, combustion are designed to operate at higher temperature, which requires highly efficient cooling structures for combustion walls. Impingement is an effective structure to enhance the convective heat transfer in the combustion cooling. In the present study, two array impingement cooling structures with cross-flow are presented, and the heat transfer characteristics are obtained experimentally. The heat transfer performance of the impingement cooling structures are studied by using the transient liquid crystal thermography technique for turbulent flow in rectangular channels within the Reynolds number range from 75,000 to 125,000. The impingement hole diameters of the two test pieces were 12mm and 11mm, respectively. The impingement distances-to-hole diameter ratios (z/d) were 1.25 and 2, and the dimensionless hole spacing (x/d) was 2.5 and 2.727. It is found that crossflow shifts the jet downstream, resulting in asymmetric flow, the heat transfer coefficient upstream of the jet weakens, and the shape of stagnation area transitions from circular to hoof-shaped. The cross-flow disturbance accelerates the diffusion of the jet, which makes the distribution of the Nusselt number on the target more uniform, and the overall heat transfer on the target is enhanced. With the change of cross-flow intensity, there are differences in the influence of heat transfer on target under different impact geometries.
Effect of the Foam Metal Casing Treatment on a Low-Speed Axial Compressor
Authors: Li Jia , Sun Dakun , Xu Reize , Dong Xu , Sun Xiaofeng 
Published: January 2021

Abstract
Foam metal is a foam-like substance made out of metal and can be used in flow control, vibration damping and acoustic absorption mainly based on their special physical properties. A kind of foam metal casing treatment is proposed and tested in this study. The impact of the foam metal casing treatment on compressor stability and noise reduction are experimentally investigated. The foam metal selected in the experiments is constructed from ferronickel and its PPI (pores per inch) is 35. The foam metal casing treatment comprises annular support casing and foam metal ring. The effect of foam metal location on stability of the test compressor are investigated by placing shims in support casing. Both time-mean and high-response instrumentation are applied to capture the steady and unsteady compressor performances with the presence of the foam metal casing treatment. 20 microphones of G.R.A.S type are used to measure in-duct acoustic level of the compressor. It is found that the SMI (stall margin improvement) is 36.1% and the efficiency loss is 1.5% at location 7. When foam metal moves to rotor leading edge, the SMI as well as the efficiency loss are getting smaller. The optimal location in the experiments is location 4 where the SMI of compressor is 14.9% and the efficiency loss is 0.1%. The interaction of foam metal with flow in the blade tip region at these locations are investigated and presented in detail. The PSD (power spectrum density) analysis is carried out to show the unsteady signal development in stall inception. The noise attenuation varies in 0.18∼1.6 dB when foam metal is at different locations. Finally, the mechanism and application of the foam metal casing treatment are also discussed.
Numerical Investigation for Characteristics and Oil-Air Distributions of a Tilting-Pad Journal Bearing Under Different Loads
Authors: Ding Aoshuang , Li Xuesong 
Published: January 2021

Abstract
This paper analyses the flow characteristics and oil-air distributions of oil flows in a tilting-pad journal bearing under different bearing loads. This titling-pad journal bearing is working at 3000 rpm rotation speed and its minimum film thicknesses have been measured under different loads from 180 kN to 299 kN. Based on the previous researches of this bearing under 180 kN, the gaseous cavitation and low-turbulence flow exists in this bearing flow. A suitable gaseous cavitation model and the SST model with low-Re correction are used in the film flow simulations. With the rotor and pads assumed to be rigid, the dynamic mesh and motion equations are applied to simulate the motions of the rotor and the rotations of the pads. Based on the simulation results under different bearing loads, the simulated minimum film thicknesses agrees well with the measured data. It indicates that the simulation results can catch the film geometries and flows correctly. With the load increasing, the rotor moves closer to the loaded pads and the minimum film thickness decreases. Taking the effect of boundary layers into consideration, the turbulence has a negative relationship with the film thickness and decreases in the loaded area under higher bearing load. It can be verified by the simulated lower turbulent viscosity ratio distributions in the loaded pads. In the unloaded area, both the film thickness and turbulence viscosity ratio are positively related to the bearing loads. Thus, the higher bearing load may lead the flow to be more different in the loaded and unloaded area, and the turbulence in the loaded pads may transfer to laminar in the end. As for the oil-air distributions, in the unloaded pads, with the bearing load increasing, the simulated air volume fraction increases in the unloaded pads with lower pressure. It should be caused by the higher film thickness of the unloaded pads under higher loads. In sum, the flow turbulence and cavitation process changes with the bearing load. With a higher load, the cavitation becomes more in the unloaded pads and the flow changes sharper from the high-turbulence unloaded area to the low-turbulence loaded area. As the simulation results is in good accordance with the experimental data, the SST model with low-Re correction and the gaseous cavitation model are verified to be suitable for bearing film simulations under different loads.
Implementation of Wide Diffusion Angle V-Shaped Holes for Gas Turbine Cooling: Design Phase and Numerical Simulation
Authors: Odemondo V. , Abba L. , Abram R. 
Published: January 2021

Abstract
This paper describes the design process carried out to develop a new hole geometry. This geometry is able to increase the cooling coverage effect on a turbine blade, in order to have a higher efficiency compared to the standard holes. The first step of the activity described is a CFD analysis of the performances of different hole geometries on a flat plate. Starting from the cylindrical holes the performances of several geometries have been compared. This study allowed the determination of the geometrical parameters mostly responsible of the film effectiveness increase. In this way a criterion able to optimize the hole geometry has been found. Keeping as constraint the same inlet section for all the geometries, the shape of the outlet section was modified in order to maximize the film coverage performances. An optimized hole geometry had been determined. This solution, called V-Shaped hole is characterized by a wide lateral expansion angle and a negligible laidback angle and it is able to increase the cooling effectiveness compared to cylindrical and shaped holes with typical expansion angles (lateral and laidback about 10°). Finally, a comparison with an experimental campaign has been performed to confirm the main results of the CFD analysis.
Combined Numerical and Experimental Study on the Use of Gurney Flaps for the Performance Enhancement of NACA0021 Airfoil in Static and Dynamic Conditions
Authors: Balduzzi Francesco , Holst David , Melani Pier Francesco , Wegner Felix , Nayeri Christian Navid , Ferrara Giovanni , Paschereit Christian Oliver , Bianchini Alessandro 
Published: January 2021

Abstract
The use of power augmentation devices in wind energy applications has been receiving increasing interest from both the scientific and the industrial community. In particular, Gurney Flaps (GFs) showed a great potential thanks to the passive functioning, the simple construction and the possibility to add them as a retrofit to existing rotors. The possibility of having a high quality set of airfoil data for a wide range of both angle of attack (AoA) and Reynolds number is pivotal in the design phase of newly developed machines. Such data are usually available in the technical literature for smooth airfoils, while there is a lack of generalized results in case of airfoils with GFs. Within this context, the authors have performed an extended investigation on the lift increase capabilities of GFs for the well-known NACA 0021 airfoil, which has been used in several wind energy applications up to now. The present paper shows the results of a combined experimental and numerical analysis considering different geometrical configurations of the flaps under both static and dynamic conditions.
Experimental data were first obtained for the AoA range of 180 degrees at a low value of Reynolds number (i.e. Re = 180 k) to analyze the impact of three different geometrical configurations of the GF on the aerodynamic behavior for the full range of incidence angles. The geometrical configurations were defined by varying the length of the flap (i.e. 1.4% and 2.5% of the chord length) and its inclination angle with respect to the blade chord (i.e. 90 degrees and 45 degrees). The experimental investigation involved also dynamic sinusoidal pitching movements at multiple reduced frequencies to evaluate the stall hysteresis cycle. Subsequently, an unsteady CFD numerical model was first calibrated against wind tunnel data at low values of the Reynolds number. Then, the virtual model was exploited to extend the investigation to a wider range of Reynolds number for dynamic AoA rates of change typical for example of vertical-axis wind turbines, i.e. characterized by higher reduced frequencies with a non-sinusoidal motion law.
Heat Transfer Characteristics of Blade Internal Tip Surface by Arrays of Delta-Winglet Vortex Generator Pairs
Authors: Zhao Zhiqi , Luo Lei , Qiu Dandan , Zhou Xun , Wang Zhongqi 
Published: January 2021

Abstract
This paper numerically investigated the effect of the arrays of the delta-winglet vortex generators (DWVGs) pairs on the flow field and heat transfer characteristics of gas turbine blade tip internal surface. Six different arrangements including three inclinations (30°, 45°, 60°) and two aspect ratios of DWVGs are calculated at Reynolds numbers ranging from 6000 to 14,000. The internal cooling passage of gas turbines are simplified as two-pass U bend channel and the U bend channel without any tabulators are considered as Baseline. The detailed flow structure, the evolution of vortices and heat transfer performance over the tip internal surface are presented. The results show that the arrays of DWVGs placed on the tip internal surface have great influence on the tip flow and heat transfer. Small-scale vortices are induced by the DWVGs, which have negligible impact on the main flow. Due to the nature of 180-deg turn, the impingement-like flow contributes the highest heat transfer performance. But too many DWVGs placed on the attachment region will weaken the energy of main flow and therefore reduce the local heat transfer. Besides, the blocked DWVGs (BVG) will enhance the heat transfer at the center line, and the guided DWVGs (GVG) will extend the low-energy flow cluster and thus weakening the heat transfer intensity. The results of this study are useful for understanding the mechanism of heat transfer characteristics in a realistic gas turbine blade by using the arrays of DWVGs.
Experimental and Numerical Comparison of Non-Reacting Flow Formation From a 7-Point Lean Direct Injector Array
Authors: Capil Tyler , Guzman Francisco , Tacina Kathleen , Hicks Yolanda 
Published: January 2021

Abstract
An experimental and numerical comparison of cold-flow structures from two configurations of a 7-point lean direct injector array was completed for this study. The comparison seeks to have the computational model aid in understanding of the experimental flow fields and expand on the underlying physics involved. Qualitative data of mean axial velocity contours as well as quantitative data of mean axial profiles facilitated the comparison between experiment and numerical solutions. Experimental data was collected using particle image velocimetry (PIV) with water seeding through the center fuel nozzle. The numerical computation was carried out with NASA’s OpenNCC (Open National Combustion Code) using steady state Reynolds Averaged Navier-Stokes (RANS) simulation to calculate gas phase velocities. There were notable quantitative differences in the average axial velocity profiles, especially at locations closest to the dump plane. However, good qualitative agreement was consistent for each 7-point configuration.
Building Digital Twins to Simulate Manufacturing Variation
Authors: Shahpar Shahrokh 
Published: January 2021

Abstract
To improve the quality of a manufactured part in industry, a variety of techniques are used to scan a built geometry to bring it back to the physics based simulation world to assess its true performance. There are various laser and structured light measurement techniques (GOM), Computed Tomography (CT) scan as well as touch-point probes in the form of CMM cloud of data that can provide an estimate for the shape of an object. However, there are many challenges on how to construct the digital geometry from the scan in order not to lose any deviations and defects and yet being able to mesh a solid manifold for simulation purposes. In this paper, a novel method based on multi-layered Artificial Intelligence (AI) is presented to produce a meaningful engineering design space to perturb the design-intent geometry to match the manufactured data cloud. The inverse mapping techniques has been applied to a range of real turbomachinery components to demonstrate its flexibility and robustness, even when the original GOM is not perfect. A case study is presented based on a real modern jet engine bypass outlet guide vane (BOGV) to show how constructing and using its digital twin and high-fidelity simulation can save a significant cost for a fleet of engines/aircraft.