bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Investigations on Full Blended Blade and Endwall Technique
Authors: Meng Tongtong , Ji Lucheng , Li Xin , Li Jiabin , Ling Zhou
Published: January 2021

In present state of art, compressor blades can work efficiently between the span of 20%–80%, while nearly 30% of the total loss comes from endwall region. Previous studies have shown that Blended Blade and End Wall (BBEW) which is a control technique can reduce the corner separation effectively. To further reduce the loss, enhance diffusion capability and restrain the secondary flow in the endwall region, in addition of a kind of non-axisymmetric endwall, Full-BBEW technique is put forward. Firstly, the geometric method of the Full-BBEW technique is presented on a NACA65 cascade with the unchanged axial passage area. Moreover, under the category of Full-BBEW technique, according to the different geometry characteristic, BBEW (blended blade and endwall) model, IOEW (inclining-only hub) model and Full-BBEW model are presented. Then in order to find the most effective design, numerical investigation and optimization based on the Kriging surrogate model are employed on the models. Compared with the prototype, the total pressure loss coefficient decreases by 7%–9% in optimized Full-BBEW cases and the aerodynamic blockage coefficient decreases about 23%–36%. Through analysis, the blended blade geometry creates a radial pressure gradient at the end section and push the low-energy fluid up to the mainstream. As the result, the loss decreases significantly between 5%–25% span range. Meanwhile, the intersection of boundary layer weakens because of the expanded dihedral angle. On the other hand, the inclining-only hub geometry reduces the circumferential pressure gradient and restrains the crossflow in corner. Overall, though the loss in mainstream increases slightly, Full-BBEW technique can reduce the boundary layer intersection and the crossing flow in corner so that the diffusion capability further increases and the aerodynamic performance in the endwall region improves effectively.
Effects of Upstream Step Geometry on Axisymmetric Converging Vane Endwall Heat Transfer and Film Cooling at Transonic Conditions
Authors: Bai Bo , Li Zhigang , Li Jun , Mao Shuo , Ng Wing , Xu Hongzhou , Fox Michael
Published: January 2021

In real gas turbine engines, a gap/step interface commonly exits between upstream of the inlet guide vane endwall and combustor, called upstream endwall misalignment, due to the errors of assembly and the thermal expansion. This endwall misalignment, commonly being presented as the gap/step geometry with different heights, has a significant effect on the endwall heat transfer and film cooling coverage distributions.

This paper presents a detailed experimental and numerical study on the effects of upstream endwall misalignment (step geometry) on the vane endwall heat transfer and film cooling in a transonic linear turbine vane passage. The experiment measurements were performed in a blowdown wind tunnel at simulated realistic gas turbine operating conditions (high inlet freestream turbulence level of 16%, exit Mach number of 0.85 and exit Reynolds number of 1.7 × 106. Three types of upstream step geometry were tested at design blowing ratio (BR = 2.5) for the same vane profile: I) baseline geometry with zero-step height of ΔH = 0 mm; II) forward-facing step geometry with negative step height of ΔH = −5 mm; III) backward-facing step geometry with positive step height of ΔH = 5 mm. The endwall thermal load and film cooling coverage distributions were measured using transient infrared thermography, being presented as endwall Nusselt number Nu and adiabatic film cooling effectiveness η, respectively.

Detailed comparisons of experiment measurements with numerical predictions were also presented and discussed for three types of upstream step configurations with ΔH = −5, 0, 5 mm, respectively. The numerical simulations were performed by solving the steady-state Reynolds Averaged Navier Stokes (RANS) with Realizable k-ε turbulence model, based on the commercial CFD solver ANSYS Fluent v.15. The effects of upstream step geometry were numerically studied, at the same design blowing ratio BR = 2.5, by solving the endwall Nusselt number, film cooling effectiveness and secondary flow field for various upstream step heights: three forward-facing step heights (from −8 mm to −3 mm), a baseline step height (0 mm), and four backward-facing step heights (from 3 mm to 10 mm).

The results show the upstream forward-facing step geometry is beneficial for the endwall thermal load and film cooling, though the improvement is weak for all step heights (less than 10% decrease in endwall heat transfer and less than 10% increase in endwall film cooling). However, the upstream backward-facing step geometry is pernicious for the endwall heat transfer and film cooling, and the influence increases with the increasing upstream backward-facing step height. The backward-facing step geometry obviously alters near endwall flow field, leading to an enhancement (up to 20%) in endwall heat transfer and significant reduction (up to 60%) in endwall film cooling effectiveness.
User Assistance for the Application of Multidisciplinary Design Tools
Authors: Schaber Reinhold , Kaiser Sascha , Luisoni Gionata
Published: January 2021

Multidisciplinary design tools are the backbone of conceptual design studies to evaluate and assess future propulsion systems. In the last decade, the IT capabilities dramatically increased. At the same time, “zooming” capabilities and more complex evaluation methods found their way into predesign tools. As a consequence, the bottleneck when performing a design study is neither the computational power nor sufficient computer memory anymore, but rather the abilities of the users to apply the dedicated tools adequately.

Therefore, it is crucial to limit the administrative tasks dealing with input and output as much as possible. Those administrative tasks can comprise the preparation of input data and — even more importantly — the check of the model setup and the inspection of the results regarding physical soundness.

The paper describes by means of examples how to cope with the challenges described above. The following topics will be addressed: standardization in the field of model configuration (engine model library), automated multidimensional check of multidisciplinary propulsion system models, use of high fidelity methods for pre-design, state-of-the-art error detection, semi-automated parametric studies including the automated set-up of a parametric study, automated convergence improvement, automated result handling, and error detection provided by the codes themselves or by other means of external user guidance.
Large-Eddy Simulation of Flame Dynamics During the Ignition of a Swirling Injector Unit and Comparison With Experiments
Authors: Töpperwien Karl , Collin-Bastiani Félix , Riber Eleonore , Cuenot Bénédicte , Vignat Guillaume , Prieur Kevin , Durox Daniel , Candel Sébastien , Vicquelin Ronan
Published: January 2021

During the ignition of a swirled single-injector combustor, two phases have been identified experimentally. In the first, the flame penetrates the injection unit, while in the second the flame lifts off after a substantial delay before stabilizing at a distance from the injector. This transient phenomenon is investigated using Large Eddy Simulations based on an Euler-Lagrange description of the liquid spray, an energy deposition model to mimic ignition and the thickened flame combustion model. It is shown that the initial penetration of the flame in the injector unit is linked with the positive pressure excursion induced by the rapid volumetric expansion of burnt gases. This sudden expansion is itself due to the fast increase in heat release rate that occurs during the initiation of the process. The corresponding positive and negative pressure disturbances induce a rapid reduction of the mass flow rate through the injector, followed by an acceleration of the flow and a return to the nominal value. It is also shown that the flame root disappears after another delay, which results in the flame edge lifting and stabilization at a distance from the injector exhaust corresponding to steady operation of the device. The relatively long delay time before this lift-off takes place is found to correspond to the residence time of the cooled burnt gases in the vicinity of the chamber walls, which are ultimately entrained by the internal recirculation zone and quench the lower flame foot.
Efficient Steady and Unsteady Flow Modeling for Arbitrarily Mis-Staggered Bladerow Under Influence of Inlet Distortion
Authors: Phan Hien M. , He Li
Published: January 2021

Accurate and efficient predictions of the steady and unsteady flow responses due to the blade-to-blade variation as well as due to the non-axisymmetric inlet distortion have been continually pursued. Computation of two problems concurrently has been rarely done in the past partly because of the need to perform whole annulus bladerow simulations, despite the advances in the current state-of-the-art methods with the phaseshift single passage simulations. The current work attempts to deal with this challenge by developing a new computational approach based on the principle of the multiscale method in the framework of a commercial solver (CFX). The methodology formulation relies on summation of the constituent source terms, each of which corresponds to a particular flow perturbation. The source term element corresponding to the blade-to-blade variation effect is linearly superimposed as in the classical Influence Coefficient Method. Only the relative positions between the reference blade and its neighbor matter in this method, thus enables an arbitrarily mis-staggered bladerow to be computed efficiently. In addition, the source term arisen due to the inlet distortion is calculated based on spatial Fourier transform. A key enabler is that the source term can be pre-computed using a small set of identical blade passages. The source term is then propagated to different spatial and temporal locations depending on the combination of the mis-staggering pattern and the inlet distortion. The multiscale treatment makes it possible to predict a high-resolution flow field effects on the base coarse mesh as if the fine mesh is solved, while achieving a computational gain. The source term summation method proposed in the current work has been validated using a uniformly staggered bladerow, and an arbitrarily mis-staggered bladerow in a clean inflow condition as well as that subject to an inlet distortion.
Investigation of the Fuel Distribution in a Shockless Explosion Combustor
Authors: Yücel Fatma Cansu , Habicht Fabian , Jaeschke Alexander , Lückoff Finn , Oberleithner Kilian , Paschereit Christian Oliver
Published: January 2021

Shockless explosion combustion is a promising concept for implementing pressure gain combustion into a conventional gas turbine cycle. This concept aims for a quasi-homogeneous autoignition that induces a moderate rise in pressure. By this, considerable losses due to entropy generation by inherent shock waves of detonation-based concepts can be avoided. Since the ignition is not triggered by an external source but driven by chemical kinetics only, the homogeneity of the autoignition is very sensitive to local perturbations in equivalence ratio, temperature, and pressure that produce undesired local premature ignition. Therefore, the precise injection of a well-defined fuel profile into an convecting air flow is crucial to ensure a quasi-homogeneous ignition of the entire flammable mixture. The objective of this work is to demonstrate that the injected fuel profile is preserved throughout the entire measurement section. For this, two different control trajectories are investigated. Optical measurement techniques are used to illustrate the effect of turbulent transport and dispersion caused by boundary layer effects on the fuel concentration profile inside the combustor. Results from line-of-sight measurements by tunable diode laser absorption spectroscopy indicate that the transport of the fuel-air mixture is dominated by turbulent diffusion. However, comparisons to numerical calculations reveal the effect of dispersion towards the bounds of the fuel concentration profile. The spatially resolved distributions of the fuel concentration inside the combustor gained from acetone planar laser induced fluorescence replicates a typical velocity distribution of turbulent pipe flow in radial direction visualizing boundary layer effects. Comparing both methods provide deep insights into the transport processes that have an impact on the operation of the shockless explosion combustor.
On the Effect of Supplied Flow Rate to the Performance of a Tilting-Pad Journal Bearing: Static Load and Dynamic Force Measurements
Authors: San Andrés Luis , Jani Hardik , Kaizar Hussain , Thorat Manish
Published: January 2021

Rotating machinery relies on engineered tilting-pad journal bearings (TPJB) to provide static load support with minimal drag power losses, safe pad temperatures, and ensuring a rotordynamic stable rotor operation. End users focus on reducing the supplied oil flow rate into a bearing to both lower operational costs and to increase drive power efficiency. This paper presents measurements of the steady-state and dynamic forced performance of a TPJB whilst focusing on the influence of supplied oil flow rate, below and above a nominal condition (50% and 150%). The test bearing has five pads, slenderness ratio L/D = 0.4, spherical pivots with pad offset = 50% and a preload ∼ 0.40, with a clearance to radius ratio (Cr/R) ≈ 0.001 at room temperature. The bearing is installed under a load-between-pads (LBP) orientation and has a flooded housing with end seals. The test conditions include operation at various shaft surface speeds (32 m/s-85 m/s) and specific static loads from 0.17 MPa to 2.1 MPa. A turbine oil lubricates the bearing with a speed-dependent flow rate delivered at a constant supply temperature. Measurements obtained at a steady thermal equilibrium include the journal static eccentricity and attitude angle, the oil exit temperature rise, and the pads’ subsurface temperatures at various locations, circumferential and axial. The rig includes measurement of the drive torque and shaft speed to produce the bearing drag power loss. Dynamic force coefficients include stiffness, damping, and virtual-mass coefficients. As expected, the drag power and the lubricant temperature rise depend mainly on shaft speed rather than on applied load. A reduction in oil flow rate to 50% of its nominal magnitude causes a modest increase in journal eccentricity, a 15% reduction in drag power loss, a moderate raise (6°C) in pads’ subsurface temperatures, a slight increase (up to 6%) in the direct stiffnesses, and a decrease (up to 7%) in direct damping coefficients. Conversely, a 1.5 times increase in oil flow rate causes a slight increase (up to 9 %) in drag power loss, a moderate reduction of pads’ temperatures (up to 3°C), a maximum 5% reduction in direct stiffnesses, and a maximum 10% increase in direct damping. The paper also presents comparisons of the test results against predictions from a thermo-elasto-hydrodynamic lubrication model. In conclusion, a 50% reduced oil flow rate only causes a slight degradation in the test bearing static and dynamic force performance and does not make the bearing operation unsafe for tests with surface speed up to 74 m/s. As an important corollary, the measured bearing drag power differs from the conventional estimate derived from the product of the supplied flow rate, the lubricant specific heat and the oil exit temperature rise.
New Insights From Conceptual Design of an Additive Manufactured 300 W Micro Gas Turbine Towards UAV Applications
Authors: Badum L. , Leizeronok B. , Cukurel B.
Published: January 2021

Owing to the high energy density of hydrocarbon fuels, ultra-micro gas turbines with power outputs below 1 kW have clear potential as battery replacement in drones. However, previous works on gas turbines of this scale revealed severe challenges due to air bearing failures, heat transfer from turbine to compressor, rotordynamic instability and manufacturing limitations. To overcome these obstacles, a novel gas turbine architecture is proposed based on conventional roller bearing technology that operates at up to 500,000 RPM and an additively manufactured monolithic rotor in cantilevered configuration, equipped with internal cooling blades. The optimum turbomachinery design is elaborated using diabatic cycle calculation, coupled with turbomachinery meanline design code. This approach provides new insights on the interdependencies of heat transfer, component efficiency and system electric efficiency. Thereby, a reduced design pressure ratio of 2.5 with 1200 K turbine inlet temperature is identified as most suitable for 300 W electric power output. In following, a review of available additive manufacturing technologies yields material properties, surface roughness and design constraints for the monolithic rotor. Rotordynamic simulations are then conducted for four available materials using a simplified rotor model to identify valid permanent magnet dimensions that would avoid operation close to bending modes. To complete the baseline engine architecture, a novel radial inflow combustor concept is proposed based on porous inert media combustion. CFD simulations are conducted to quantify compressor efficiency and conjugate heat transfer analysis of the monolithic rotor is performed to assess the benefit of the internal cooling cavity and vanes for different rotor materials. It is demonstrated that the cavity flow absorbs large amount of heat flux from turbine to compressor, thus cooling the rotor structure and improving the diabatic cycle efficiency. Finally, the results of this conceptual study show that ultra-micro gas turbine with electric efficiency of up to 5% is feasible, while energy density is increased by factor of 3.6, compared to lithium-ion batteries.
Boundary Layer Flashback Limits of Hydrogen-Methane-Air Flames in a Generic Swirl Burner at Gas Turbine Relevant Conditions
Authors: Ebi Dominik , Jansohn Peter
Published: January 2021

Operating stationary gas turbines on hydrogen-rich fuels offers a pathway to significantly reduce greenhouse gas emissions in the power generation sector. A key challenge in the design of lean-premixed burners, which are flexible in terms of the amount of hydrogen in the fuel across a wide range and still adhere to the required emissions levels, is to prevent flame flashback. However, systematic investigations on flashback at gas turbine relevant conditions to support combustor development are sparse. The current work addresses the need for an improved understanding with an experimental study on boundary layer flashback in a generic swirl burner up to 7.5 bar and 300° C preheat temperature. Methane-hydrogen-air flames with 50 to 85% hydrogen by volume were investigated. High-speed imaging was applied to reveal the flame propagation pathway during flashback events. Flashback limits are reported in terms of the equivalence ratio for a given pressure, preheat temperature, bulk flow velocity and hydrogen content. The wall temperature of the center body along which the flame propagated during flashback events has been controlled by an oil heating/cooling system. This way, the effect any of the control parameters, e.g. pressure, had on the flashback limit was de-coupled from the otherwise inherently associated change in heat load on the wall and thus change in wall temperature. The results show that the preheat temperature has a weaker effect on the flashback propensity than expected. Increasing the pressure from atmospheric conditions to 2.5 bar strongly increases the flashback risk, but hardly affects the flashback limit beyond 2.5 bar.
Possibilities and Limitations of Early Fault Detection in Gas Turbines
Authors: Persigehl Bernhard , Gellermann Thomas , Thumm Stefan , Stoiber Johannes
Published: January 2021

Since the 1960’s the maintenance concepts of gas turbines have remarkably changed. Nowadays, condition monitoring systems supervise modern gas turbines. These systems are capable of avoiding failures that are developing slowly. The actual enhancement of early fault detection is predictive maintenance where big data from different sources is used to predict the behavior of gas turbines.

In this paper eight different actual gas turbine failures are presented, beginning with the damage event and the root cause and followed by a discussion, whether the failure could have been avoided by predictive maintenance. In some cases, e.g. during commissioning, a successful early fault detection with predictive maintenance cannot be achieved, since the failure often occurs suddenly and is unforeseen. In others cases, especially during operation, the failure could have been prevented by predictive maintenance. However, it has to be stated, in all these cases significantly more measuring devices would have been necessary.

The potential exists that more failures can be avoided by predictive maintenance in the future. However, there are also damage scenarios that cannot be prevented by any early fault detection system. Thus, the Possible Maximum Loss, an important figure for technical insurances, remains unchanged independent of the application of predictive maintenance.
Modeling of Cyclic Life for Compressor Rotor of Gas Turbine Engine Taking Into Account Production Deviations
Authors: Arkhipov Alexandr N. , Ravikovich Yury A. , Matushkin Anton A. , Kholobtsev Dmitry P.
Published: January 2021

The regional aircraft with a turbofan gas turbine engine, created in Russia, is successfully operated in the world market. Further increase of the life and reduction of the cost of the life cycle are necessary to ensure the competitive advantages of the engine.

One of the units limiting the engine life is the compressor rotor. The cyclic life of the rotor depends on many factors: the stress-strain state in critical zones, the life of the material under low-cycle loading, the regime of engine operation, production deviations (within tolerances), etc.

In order to verify the influence of geometry deviations, the calculations of the model with nominal dimensions and the model with the most unfavorable geometric dimensions (worst cases) have been carried out.

The obtained influence coefficients for geometric and weight tolerances are then used for probabilistic modeling of stresses in the critical zone. Rotor speed and gas loads on the blades for different flight missions and engine wear are determined from the corresponding aerodynamic calculations taking into account the actual flight cycles (takeoff, reduction, reverse) and are also used for stress recalculations.

The subsequent calculation of the rotor cyclic life and the resource assessment is carried out taking into account the spread of the material low-cycle fatigue by probabilistic modeling of the rotor geometry and weight loads.

A preliminary assessment of the coefficients of tolerances influence on stress in the critical zone can be used to select the optimal (in terms of life) tolerances at the design stage.

Taking into account the actual geometric and weight parameters can allow estimating the stress and expected life of each manufactured rotor.
A Damage-Based Fatigue Model of Braided Ceramic Matrix Composites at Elevated Temperature
Authors: Liu Changqi , Shi Duoqi , Yang Xiaoguang , Teng Xuefeng
Published: January 2021

Ceramic matrix composites (CMCs) play an increasingly significant role in the modern aerospace industry due to their excellent high-temperature mechanical properties. Fatigue property at elevated temperatures is an essential issue for their application, especially for the turbine blades of aircraft engines subjected to cyclic loading under extreme conditions. A progressive fatigue damage approach was established to predict the damage initiation and evolution of braided SiC/SiC CMCs under tension-tension cyclic loading. The main framework was achieved via a user-material subroutine UMAT in ABAQUS with FORTRAN code. Different damage initiation criteria are introduced for fiber bundles, matrix and interface. Related experimental results reveal that the main reasons for the failure of composites under cyclic loading are the loss of bearing capacity of the matrix, the decrease of fiber strength in high-temperature oxidation environment and the interface wear. Hence, the stiffness and strength degradation of matrix and fiber bundles as well as the interfacial shear stress reduction are used to describe the fatigue damage in this method. And a specific proportion of failure elements on the loading surface is regarded as the symbol of the eventual failure of the composites. Damage evolution of different constituents during the fatigue process can be simulated with this method. Subsequently, the simulation results of static and fatigue analysis were compared with relevant experimental results at 1300°C. It indicates that the predicted static tensile strain-stress curve, and curves of maximum strains vs cycles in the fatigue analysis are in good agreement with that measured during the experiments. Besides, the predicted fatigue life also exhibits an acceptable consistency.
An Experimental and Computational Investigation of a Pulsed Air-Jet Excitation System on a Rotating Bladed Disk
Authors: Kurstak Eric , D’Souza Kiran
Published: January 2021

Non-synchronous vibrations are a difficult problem to address for turbomachines due to the complex nature of the forcing. Such vibrations can be caused by vortex shedding, flow instabilities, stall cells, or flutter. Testing a design with such excitations can be difficult in practice due to the required forcing. This work demonstrates an experimental excitation method using pulsed air jet excitation to create non-synchronous vibrations in engine hardware rotating at nominal design speeds. Experimental runs were conducted to excite a number of engine orders. Blade tip timing was used to measure the blade response without interfering with the blade dynamics. The bladed disk was held at a constant rotational speed while the air jets were pulsed at a sweeping frequency to simulate rotating forcing. Computational models of the physical system were constructed using parametric reduced order models that incorporate the effects of rotational speed and small mistuning. The computational model was used in simulations that mimic the experiment; the forcing was swept across the blades while being pulsed. This results in a system response that cannot be captured using traditional harmonic analyses. The computational and experimental datasets were compared through mistuning values, amplitudes, and the nodal diameter content in the system response.
Numerical Modeling of the Effects of Leading-Edge Erosion and Trailing-Edge Damage on Wind Turbine Loads and Performance
Authors: Papi Francesco , Cappugi Lorenzo , Bianchini Alessandro , Perez-Becker Sebastian
Published: January 2021

Wind turbines often operate in challenging environmental conditions. In hot and dusty climates, wind turbine blades are constantly exposed to abrasive particles that, according to many field reports, cause significant damages to the blade’s leading edge. On the other hand, in cold climates similar effects can be caused by prolonged exposure to hail and rain. Quantifying the effects of airfoil deterioration on modern multi-MW wind turbines is crucial to correctly schedule maintenance and to forecast the potential impact on productivity. Analyzing the impact of airfoil damage on fatigue and extreme loading is also important to improve the reliability and longevity of wind turbines. However, this is a topic that has not yet been extensively investigated. In this work, a blade erosion model is developed and calibrated using Computational Fluid Dynamics (CFD). The DTU 10MW Reference Wind Turbine (RWT) is selected as the case study for the analysis, as it is representative of the typical size of the future generation wind turbines. Lift and Drag polars are generated using the developed model and a CFD numerical set-up. Power and torque coefficients are compared in idealized conditions at two wind speeds, i.e. the rated speed and one below it. Full aero-servo-elastic simulations of the turbine are conducted with the eroded polars using NREL’s BEM-based code OpenFAST. Sixty-six ten-minute simulations are performed for each stage of airfoil damage, reproducing operating conditions specified by the IEC 61400-1 power production DLC-group, including wind shear, yaw misalignment and turbulence. Performance data, fatigue and extreme loads are compared for the aeroelastic simulations, showing maximum decreases in CP of about 12% as well as reductions in fatigue and extreme loading.
The Endwall Effects of Stators With and Without Simplified Penny Gaps in a High-Loaded Multistage Compressor
Authors: Wang Xiaochen , Ren Xiaodong , Li Xuesong , Wu Hong , Gu Chunwei
Published: January 2021

A simplified configuration of variable stator vanes, which has a uniform hub clearance and a stationary hub surface, is applied to a high-loaded multistage compressor. Comparisons of endwall flow structures are made between the ideal and the simplified configurations. After validating numerical results of the ideal stator configuration with experiment data, the third stator and all stators are modified with the simplified configuration in two separate cases. Flow structures and loss characteristics in the endwall region are investigated numerically in detail at design point. Limited corner separation near the suction side and comparatively strong secondary flow near the pressure side make similar contributions to endwall loss at design point for the baseline configuration, while the shear flow of the blade tip and the endwall boundary layer are regarded as important sources of loss for the modified configuration.
Experimental Investigation and Numerical Modelling of a Large Heavily-Loaded Tilting Pad Journal Bearing With Polymer Lined Pads
Authors: Cangioli Filippo , Livermore-Hardy Richard , Pethybridge Guy , Mermertas Uemit , Stottrop Michael , Bender Beate
Published: January 2021

A large tilting-pad journal bearing (TPJB) with “PEEK” polymer-lined pads was tested over a range of operating conditions representative of those experienced on turbogenerators used in fossil fuel power plants. The 500 mm diameter test-bearing has four offset-pivot pads, ball and socket pivots, load-between-pivot configuration, directed lubrication and hydrostatic jacking features. The operating conditions explored during the test campaign characterize the static and dynamic behaviour of the bearing over a range of shaft surface speeds between 40 m/s and 95 m/s and maximum specific load of 4.75 MPa. Similar test conditions were previously investigated on the same bearing with whitemetal lined pads, allowing for a direct comparison.

A thermo-elasto-hydrodynamic (TEHD) model for TPJBs with polymer-lined pads is introduced in this paper and validated against experimental test data.

Experimental data along with numerical results reveal and confirm the superior performance that can be attained using TPJBs with polymer lined pads at high specific loads.
A Method for the Simulation of Time-Dependent In-Service Performance Change
Authors: Evans Rich , Dawes Bill , Meah Nabil , Kudryavtsev Andrey , Hunt Matthew
Published: January 2021

Most numerical engineering simulation is performed on pristine, as-designed representations of the components and systems in question. Although the rate of through-life performance degradation is hugely important when considering the total cost/benefit of a system, engineers have had profound difficulties in modelling the physical changes that components undergo in service due to the quasi-random and organic nature of the mechanisms such as wear, corrosion, icing and fouling. Typically, the creation of ‘worn’ models is based on a posteriori inspection or scanning of a failing or failed component.

This paper presents a novel method for modifying geometry in response to scalar field variables directly accessed from the embedded physical models within physics-based simulation. It uses a distance field, managed as a Level-set, to drive time-dependent changes to the geometry surface, borrowing heavily from technology which has seen widespread use in the computer graphics industry to create and modify items in a natural organic way. A computational mesh can then be constructed around and within the modified geometry so that the simulation can be performed on the now ‘in-service’ version of the components. This greatly improves the predictive power of such simulations and provide a priori predictions of component performance in response to, for example, corrosive environments.

The method is robust, can manage and create meshes for arbitrarily complex geometry, is insensitive to large scale topology changes such as hole blockage or passage burn-through, is highly suitable for automated simulation workflows and can represent both additive (fouling, icing) and reductive (erosion, corrosion, burn though) shape change.
Transfer Optimization in Accelerating the Design of Turbomachinery Cascades
Authors: Wang Qineng , Song Liming , Guo Zhendong , Li Jun
Published: January 2021

This paper draws motivation from the fact that engineering optimizations were mostly carried out from scratch. In contrast, however, humans routinely take advantage of the knowledge from past experiences whenever a new task is met. Such a transfer learning process by leveraging knowledge from already completed tasks can be promising to significantly improve the performance of current state-of-the-art algorithms, particularly in solving expensive black-box problems. In light of the above, we propose a Cokriging based transfer optimization framework for the design of turbomachinery cascades, which is demonstrated by optimization to re-design the first-stage vane of GEE3. Specifically, when building Cokriging surrogate in such a transfer optimization context, the samples from already completed tasks are treated as low-fidelity (LF) data. The acquisition function of expected improvement is adopted to guide the search for high-fidelity (HF) data. In order to make full use of the “past experiences”, one of our efforts was drawn to designing selection strategies of initial HF samples. In addition, as the “past experiences” may do harm to the optimization of the target task, the correlation coefficients between source and target tasks in each optimization process were calculated to avoid “negative transfer”. The test results show that, by learning from the past, the transfer optimization framework can reduce the computational cost by much as 50%. More importantly, our proposed transfer learning strategy can effectively avoid “negative transfer” and thus always achieve better solutions than the compared state-of-the-art algorithms.
Advances and Challenges in Purging Pipeline Sections: Field Measurements vs. 1D Purging Model
Authors: Botros Kamal K. , Hawryluk Andrew , Ryapolov Dmitry
Published: January 2021

Effective purging of air out of a pipeline section before commissioning by direct displacement with natural gas has been safely practiced for decades with the recognition that flammable interfacial mixing zone between the driving gas (behind) and the air (ahead) is inevitable. In cases when the purge velocity is below a threshold dictated by the gravity current velocity (defined in AGA Purging Principles and Practices, 2001), natural gas being lighter than air can in fact ride over air being the heavier gas and short circuit the flow path to the vent at the other end of the pipe section, thus trapping behind pockets of air that could potentially introduce risk of internal explosion with subsequent damage to the pipe section and pose a safety issue to field personnel. Therefore, maintaining the purge velocity above this threshold by a good margin has been a common practice in the purging procedure to-date. In fact, maintaining the purge velocity above the threshold can be controlled by the injection press or flow, where tools and dynamic purging models have been successfully developed and proven to be useful. However, AGA recommends that the drive purge gas pressure be limited to 689 kPag (100 psig) in the inlet purge line to the pipe section to avoid the risk of detonation. In some cases when the inlet purge line is relatively small compared to the main pipe section, this limit on the purge pressure would result in gas/air interfacial velocity much lower than the threshold velocity, hence stratification will occur. This paper provides insight into the possibility of increasing the purge pressure above AGA limit to avoid stratification, while conforming to the safety aspects related to detonation. A purge model is developed to overcome the shortcoming in AGA purge software that limits the purge pressure to maximum of 689 kPag (100 psig). Field trial was conducted to validate the model which demonstrated, as a proof of concept, a successful purge procedure with purge pressure = 5517 kPag (800 psig) in NPS 1.5 purge line to purge nitrogen out of NPS 42, 5.8 km section of a pipeline.
Liquid Pipeline Rupture Detection Using Multiple Artificial Intelligence Classifiers During Steady-State and Transient Operations
Authors: MacDonald Christopher , Yang Michael , Learn Shawn , Hugo Ron , Park Simon
Published: January 2021

There are several challenges associated with existing rupture detection systems such as their inability to accurately detect during transient (such as pump dynamics) conditions, delayed responses and their inability to transfer models to different pipeline configurations easily. To address these challenges, we employ multiple Artificial Intelligence (AI) classifiers that rely on pattern recognitions instead of traditional operator-set thresholds. AI techniques, consisting of two-dimensional (2D) Convolutional Neural Networks (CNN) and Adaptive Neuro Fuzzy Interface Systems (ANFIS), are used to mimic processes performed by operators during a rupture event. This includes both visualization (using CNN) and rule-based decision making (using ANFIS). The system provides a level of reasoning to an operator through the use of the rule-based AI system. Pump station sensor data is non-dimensionalized prior to AI processing, enabling application to pipeline configurations outside of the training data set. AI algorithms undergo testing and training using two data sets: laboratory-collected data that mimics transient pump-station operations and real operator data that includes Real Time Transient Model (RTTM) simulated ruptures. The use of non-dimensional sensor data enables the system to detect ruptures from pipeline data not used in the training process.
Undermatching and Low Strain In-Service Failures in X70 Line Pipe: Contributions From Standards, Specifications and Coating
Authors: Barbaro Frank , Fletcher Leigh
Published: January 2021

Some 10 incidents of low strain in-service and pre-service hydrotest failures in girth welds have been reported in North America since the Enterprise Products ethane pipeline failure in 2015. No such failures have been reported in Australia, despite the similarities in Standards, the line pipe data, and the use of manual SMAW using fully cellulosic procedures.

There are however significant differences that warrant further investigation and adoption in terms of best practice to ensure the security and safety of our pipeline networks.

Some unique differences and observations in terms of pipe properties, weld qualification procedures, test methods and even full scale pressure burst tests before and after coating are described to highlight subtle differences in the standards that may provide clarity in explaining pipeline girth weld failures and it is anticipated may also provide guidance for the future.
Peer Review of the Plausible Profiles Corrosion Assessment Model
Authors: Kiefner John
Published: January 2021

An enhanced corrosion assessment model has been developed by TC Energy. The new model is called the “Plausible Profiles Model for Corrosion Assessment” or “Psqr” for short and is described in three IPC 2020 papers1,2,3. The Psqr model uses a probabilistic approach for creating a number of plausible profiles along a corroded area. The predicted failure pressure for each plausible profile is calculated using RSTRENG, resulting in a probabilistic distribution of predicted failure pressures. The predicted failure pressure for the corroded area is taken to be the lower 5th percentile value of the distribution.

TC Energy requested that PRCI sponsor an independent review of the Psqr model by subject matter experts (SMEs). The PRCI Corrosion Technical Committee and TC Energy jointly selected a team of SMEs to conduct the review. The team was comprised of the following individuals:

• Maher Nessim — C-FER Technologies

• Ming Gao — Blade Energy Partners

• Ravi Krishnamurthy — Blade Energy Partners

• Phil Hopkins — Independent Consultant

• Andrew Cosham — Ninth Planet Engineering

• Michael Rosenfeld — RSI Pipeline Solutions

• Bruce Nestleroth — Kiefner and Associates, Inc.

• John Kiefner — RSI Pipeline Solutions

This paper describes the work carried out by the SMEs and presents their findings and conclusions. Basically, they found that the model is more accurate and exhibits less scatter than existing models such as RSTRENG, B31G, and Modified B31G4. They recommended that the Psqr Model be implemented in conjunction with a high-quality corrosion management plan such as that outlined in TC Energy’s technical report5, and they recommended specific minimum Psqr-predicted failure stress levels for use on pipelines being operated at maximum stress levels ranging from 40% of SMYS to 80% of SMYS.
A Novel Three-Dimensional Non-Contact Magnetic Stress Inspection Technology and its Application on LNG Pipeline
Authors: He Guoxi , He Tengjiao , Liao Kexi , Zhu Hongdong , Zhao Shuai
Published: January 2021

On the basis of the metal-magnetic-memory (MMM) effect, a three-dimensional high-precision non-contact pipeline magnetism-based stress inspection (PMSI) technology is developed for trenchless inspection of buried pipeline defects. This technology is a new non-destructive testing technology, which can find the possible stress concentration area (SCA) along the buried gas transmission pipeline. Hence, we could further judge according to the testing data that the stress concentration is caused by the overpressure which results from whether the pipeline external load at the potential landslide of the soil or serious metal loss such as corrosion defects. The stress inspection method determines the relative risk of defects by directly quantifying the change level of stress, rather than calculating the geometric parameters (length, width, height) of defects. The PMSI was carried out on a 10.3 km LNG pipeline and two level-II SCAs were found. A comprehensive index F was defined to evaluate the severity quantitatively and judge the grade of the defect status as well as the sensitive. Thus, the relative stress and thereby the safety state of the pipeline are judged, and then the precise position of the relatively serious section on the pipeline is determined.
An Integrated Approach to System-Wide Landslide Monitoring in the Appalachian Basin Region of the U.S.
Authors: Theriault Bailey , Hennessy John , Markley Chris
Published: January 2021

Landslides have the potential to adversely affect the integrity of pipelines. Identifying, characterizing, evaluating, and if necessary, mitigating and monitoring landslide hazards have become critical steps to successfully and safely building and operating pipelines in the Appalachian Basin region of the United States. Natural geologic, geographic, and climatic conditions in this region combine to create a high incidence of landslides, with landslide formation and movement often exacerbated by anthropogenic activity. Rapid expansion of pipeline construction and operation in the region, along with the ever-decreasing availability of preferred routing options, have resulted in increased landslide-related pipeline incidences, both during and post-construction. As such, there is an increasing need to identify, characterize, and closely monitor landslide hazards throughout the construction and operational lifespan of each pipeline system. This can prove challenging in an area where a pipeline may be subject to an average of two to five landslides per mile of pipeline, and where new landslide hazards may develop on an annual basis. Typical site-specific monitoring approaches (e.g., strain gauge, inclinometers, monitoring points, etc.) may not be economically feasible to use for all hazards when traversing long distances of such terrain, and such approaches likely do not address the need to identify new hazards that may develop over time (e.g., new or reactivated landslides).

Strong monitoring programs should seek to identify and use complimentary technologies to balance out the relative strengths and weaknesses of each. Overdependence on a single or select number of tools could lead to overconfidence and an unnecessary number of false positives and negatives. This paper will provide an overview of monitoring approaches that have proven useful for the long-term monitoring and assessment of high density landslide areas at a system-wide scale, including the use of repeat LiDAR surveys (i.e., LiDAR Change Detection Analysis), in-line inspection (ILI) inertial measurement unit (IMU) data, aerial patrol/reconnaissance, and ground patrol. Case studies will be presented from the Appalachian Basin region, including how monitoring techniques were selected based on specific pipeline system configurations and individual Operator objectives, and how they are being used to track existing hazards and to identify hazards as they develop.
Safety Risk Acceptance Criteria for Pipelines
Authors: Nessim Maher , Kariyawasam Shahani
Published: January 2021

The lack of established acceptance criteria has been one of the key challenges to the application of quantitative risk assessment (QRA) techniques in the Canadian pipeline industry. While a wide range of such criteria have been developed and published, it remains difficult for most operators to commit to specific criteria because such criteria may not be acceptable to all stakeholders. Recognizing this limitation, the Canadian Standards Association formed a Risk Management Task Force (RMTF) under the Technical Committee for the Z662 Standard on the Oil and Gas Pipeline Systems to propose criteria for potential inclusion in its non-mandatory Annex on Risk Assessment.

This paper describes the criteria that have been developed by the RMTF and provides the background information needed for users to understand and use them correctly. The discussion includes: a summary of the measures used to quantify the safety risk associated with an ignited product release; a summary of established international and Canadian criteria that have been considered; a description and interpretation of the ALARP (As Low As Reasonably Practicable) principle; and the rationale used by the RMTF to select specific individual risk and societal risk criteria for CSA Z662. The proposed criteria are also compared to the criteria underpinning other risk-based parts of the Z662 Standard, including Annexes C and O.

Guidance is provided on the analysis assumptions, methods and parameters required to ensure that the risk calculations produce results that are consistent with the definition and intent of the criteria. Key issues addressed by the guidance include the definition of individual risk (i.e. location risk versus personal risk), the pipeline length over which the frequency versus number of fatalities (F-N) relationship representing societal risk is calculated, and the effect of population density averaging over the pipeline length.