bluuebunny/crossref_metadata_2025 huggingface dataset:
Extremely Low Mass Flow at High Blade to Jet Speed Ratio in Variable Geometry Radial Turbines and its Influence on the Flow Pattern: A CFD Analysis
Authors: Serrano José Ramón , Gil Antonio , Navarro Roberto , Inhestern Lukas Benjamin
Published: August 2017

State of the art car engines are fed by compressed air, coming from a turbocharger compressor, to increase the power to weight ratio and to allow downsizing the combustion engine. The used compressor is driven by a radial turbine taking advantage of the hot and pressurized exhaust gases of the engine. Thus, the turbine acts under highly unsteady conditions, working at very different turbine map regions. In urban driving the turbine faces even higher changes due to frequent acceleration and deceleration so that extremely low mass flow can occur. However, the flow behavior in turbocharger turbines at these extreme off-design conditions is rather unknown. So the development of physically-based models for extrapolating the usually narrow experimental turbine maps and advanced measurements to increase the range of turbine maps has been in the focus of many researchers. To provide valuable information about those flow characteristics, this paper supplies a detailed analysis at low mass flow in a radial turbocharger turbine. The turbine has been experimentally characterized under steady flow from normal operating working conditions up to extreme off-design points, where the turbine could even work with negative efficiency. Since heat transfer significantly affects the turbine efficiency calculation when turbine power is low, the experiments have been executed under quasi-adiabatic conditions and residual heat fluxes have further been corrected. This paper takes advantage of these data to validate adiabatic CFD simulations in a wide operating range, from optimum efficiency point up to negative turbine power. Stationary and transient three-dimensional CFD simulations of the turbocharger turbine have been performed. The numerical campaign covers a wide range of operating conditions, providing different flow patterns. The obtained results show that the secondary flow field changes appreciably with mass flow rate. At low mass flows, a further backflow region develops over the entire circumference close to the hub, significantly constricting the effective turbine area and provoking mass flow instability. The highlighted flow phenomena will allow to improve state of the art extrapolation models and might help designers to understand turbine flow operating under extreme off-design conditions.
Aerodynamic Optimization of High Pressure Turbine and Interstage Duct in a Two-Stage Air System for a Heavy-Duty Diesel Engine
Authors: Khairuddin Uswah , Costall Aaron W.
Published: August 2017

Turbochargers are a key technology for reducing the fuel consumption and CO2 emissions of heavy-duty internal combustion engines by enabling greater power density, which is essential for engine downsizing and downspeeding. This in turn raises turbine expansion ratio levels and drives the shift to air systems with multiple stages, which also implies the need for interconnecting ducting, all of which is subject to tight packaging constraints.

This paper considers the challenges in the aerodynamic optimization of the exhaust side of a two-stage air system for a Caterpillar 4.4-litre heavy-duty diesel engine, focusing on the high pressure turbine wheel and interstage duct. Using the current production designs as a baseline, a genetic algorithm-based aerodynamic optimization process was carried out separately for the wheel and duct components in order to minimize the computational effort required to evaluate seven key operating points.

While efficiency was a clear choice for the cost function for turbine wheel optimization, the most appropriate objective for interstage duct optimization was less certain, and so this paper also explores the resulting effect of optimizing the duct design for different objectives. Results of the optimization generated differing turbine wheel and interstage duct designs depending on the corresponding operating point, thus it was important to check the performance of these components at every other operating point, in order to determine the most appropriate designs to carry forward. Once the best compromise high pressure turbine wheel and interstage duct designs were chosen, prototypes of both were manufactured and then tested together against the baseline designs to validate the CFD predictions. The best performing high pressure turbine design, wheel A, was predicted to show an efficiency improvement of 2.15 percentage points, for on-design operation. Meanwhile, the optimized interstage duct contributed a 0.2 and 0.5 percentage-point efficiency increase for the high and low pressure turbines, respectively.
Experimental Investigation of a Bluff Body Burner for Distributed Hydrogen Injection
Authors: Gounder James D. , Kutne Peter , Gruber Andrea
Published: August 2017

A novel concept for injection of gaseous hydrogen (fuel) into a stream of air (oxidant) with in low-NOx gas turbine combustion systems is proposed and tested experimentally in a laboratory bluff body (BB) burner. Instead of conventional injection nozzles, that represent undesired point sources of the highly reactive fuel, the injection concept presented in this paper employs porous steel components, with anticipation to achieve hydrogen injection into air in a compositionally diluted and spatially distributed fashion. The BB burner is tested with four different bluff bodies: three bluff bodies manufactured of solid steel and characterized by different diameters are used to chart the burner behavior in conventional, fully-premixed operation with respect to flame stoichiometry and bulk velocity; one bluff body of porous steel is used to implement and demonstrate the distributed fuel injection (BB-DFI) concept. The experimental setup consists of OH* chemiluminescence (CL) and luminescence of flame measured at kHz repetition rate (4 kHz OH* CL and 14 kHz luminescence of flame) using high-speed cameras. Stable operation of the BB-DFI burner configuration with distributed hydrogen injection is demonstrated in the equivalence ratio range of 0.3–0.5 for three bulk velocities of 15, 25 and 35 m/s with the flame anchoring downstream of the distributed injection section, on the tip of the bluff body, according to design. The flame shape observed during the initial tests suggests inadequate mixing between the fuel and carrier air in the mixing section. For comparison, three different arrangements of vortex generators are designed and manufactured to improve fuel-oxidant mixing. The effectiveness of the vortex generators in terms of mixing is investigated using laser induced fluorescence (LIF) technique and one of the vortex generator arrangement show promising improvement in fuel-oxidant mixing.
Innovative Material Testing Based on Small-Scale Specimens and Application for Turbomachinery Components
Authors: Raddatz Mario , Holländer Dirk , Gampe Uwe
Published: August 2017

Material characterization is usually based on standard specimen testing. In contrast, small-scale specimens require less testing material and offer additional advantages like investigation of size effects with impact on material properties (specimen diameter equivalent to wall thickness of buckets and liners) and testing of samples of virgin or service-exposed turbomachinery components. The paper highlights the small-scale specimen test setup and its application for LCF- and HCF-testing. Innovative small-scale specimen testing with close-to-component structural features enables direction dependent and spatially resolved determination of material characteristics. Cast and forged gas turbine nickel-based alloys and a typical steam turbine steel are the materials of interest in this study. Substrate temperature levels ranges from room temperature up to 1000 °C. Test system, radiation heating, instrumentation and two types of small-scale specimen geometries according to German standard DIN 50100 will be presented. Benefits and limitations of application of small-scale specimens will be discussed. Finally the authors report about application of small-scale specimen testing for remaining life time determination of service exposed gas turbine buckets. Small-scale specimens have been directly extracted from a gas turbine. Bucket root material (conventionally cast nickel-base alloy IN738) and literature data serve as reference base for initial state of the material. Tensile and LCF tests have been carried out at a representative material temperature for service conditions of 850 °C. Published material data of IN738 are available at this temperature. On that basis, fatigue life consumption has been estimated. The presented procedure for remaining life time prediction can also be applied to other turbomachinery components.
Integrated Electrical Machine-Turbo Machinery
Authors: Al-ani M. M. J. , Lee S. P. , Allport J. M.
Published: August 2017

Global warming and climate change due to rising levels of greenhouse gases have placed significant pressure on the automobile industry to adopt more clean fuel, transportation electrification, and waste energy recovery technologies. As a result, several electrically assisted or driven turbo-machines have been proposed such as turbochargers, turbo-compressors, and electrical boosters. Therefore, the electrification of turbo-machinery has been trending for the past decade.

All the systems mentioned above consist of a conventional electrical machine connected to the turbo-machinery by a shaft, making the system relatively large, heavy, costly and mechanically complex.

In this paper, an integrated electrical machine-turbo machinery concept is proposed. It consists of an electrical machine mounted around a salient rotor that is shaped like an axial flow turbo-machinery wheel. The electrical machine can be used as a motor to drive or assist the operation of the turbo-machine or it can operate as a generator powered by the gas or fluid flow. Compared to the conventional electrically derived or assisted turbo-machine systems, the proposed system is expected to decrease the overall size, weight and complexity.

In order to illustrate this concept, an initial multi-physics feasibility study is presented. Electromagnetic and mechanical, performance are calculated and investigated using FEA. Additionally, aerodynamic consideration has been illustrated.
Investigation of Fan Blade off Events Using a Bayesian Framework
Authors: Profir B. , Eres M. H. , Scanlan J. P. , Bates R.
Published: August 2017

This paper illustrates a probabilistic method of studying Fan Blade Off (FBO) events which is based upon Bayesian inference. Investigating this case study is of great interest from the point of view of the engineering team responsible with the dynamic modelling of the fan. The reason is because subsequent to an FBO event, the fan loses its axisymmetry and as a result of that, severe impacting can occur between the blades and the inner casing of the engine. The mechanical modelling (which is not the scope of this paper) involves studying the oscillation modes of the fan at various release speeds (defined as the speed at which an FBO event occurs) and at various amounts of damage (defined as the percentage of blade which gets released during an FBO event). However, it is virtually infeasible to perform the vibrational analysis for all combinations of release speed and damage. Consequently, the Bayesian updating which forms the foundation of the framework presented in the paper is used to identify the most likely combinations prone to occur after an FBO event which are then going to be used further for the mechanical analysis. The Bayesian inference engine presented here makes use of expert judgements which are updated using in-service data (which for the purposes of this paper are fictitious). The resulting inputs are then passed through 1,000,000 Monte Carlo iterations (which from a physical standpoint represent the number of FBO events simulated) in order to check which are the most common combinations of release speed and blade damage so as to report back to the mechanical engineering team. Therefore, the scope of the project outlined in this paper is to create a flexible model which changes every time data becomes available in order to reflect both the original expert judgements it was based on as well as the real data itself. The features of interest of the posterior distributions which can be seen in the Results section are the peaks of the probability distributions. The reason for this has already been outlined: only the most likely FBO events (i.e.: the peaks of the distributions) are of interest for the purposes of the dynamics analysis. Even though it may be noticed that the differences between prior and posterior distributions are not pronounced, it should be recalled that this is due to the particular data set used for the update; using another data set or adding to the existing one will produce different distributions.
Effect of Turbulence Damping in VOF Simulation of an Aero-Engine Bearing Chamber
Authors: Bristot Andrea , Morvan Hervé P. , Simmons Kathy , Klingsporn Michael
Published: August 2017

In aero-engine bearing chambers, the modelling of shear-driven oil films with the Volume of Fluid method poses significant challenges linked with the need to accurately capture the gas-liquid interaction at the free surface. Typically, the modelling of the latter relies on a dedicated scalable source term, which is activated locally at the interface between the phases. Our latest published work focused on the application of a popular term of this kind known as turbulence damping, and raised some questions on the suitability of the choice of a high value for its scaling factor. In this paper, a lower turbulence damping factor value is proposed. The new results are evaluated against both the reference bearing chamber experimental data and the previously published numerical data. The results highlight that a transition from shear-driven to gravity-driven flow conditions takes place once the damping factor value is decreased. Considering the impact this may have on the accuracy of the numerical predictions, a strategy is proposed towards a better-informed choice of the turbulence damping factor, in particular when the expected flow conditions are unknown.
Experimental Sensitivity Analysis and the Equivalence of Pulsed Forcing and Feedback Control in Thermoacoustic Systems
Authors: Jamieson Nicholas P. , Juniper Matthew P.
Published: August 2017

We examine the shifts in linear decay rates and growth rates, with and without control devices on a simple thermoacoustic system. When the system is stable, we measure the decay rate by pulsing with a loudspeaker. This improves on the experimental techniques developed by Rigas et al. (J. Fluid Mech., 2016, vol. 787, R1 [1]) and Jamieson et al. (Int. J. Spray and Comb. Dyn., accepted, 2016 [2]), to develop a more efficient method of experimental sensitivity analysis to apply in thermoacoustic systems. When the system is unstable, we use feedback control to bring it to a non-oscillating state. We then switch off the feedback control and measure the growth rate. The results suggest that both methods are suitable for use in the experimental sensitivity analysis of thermoacoustic systems. Our experimental set up is automated and we find that we can obtain thousands of decay rates in 1/12 the time compared with the previous work.
Towards Investigation of External Oil Flow From a Journal Bearing in an Epicyclic Gearbox
Authors: Berthold Martin , Morvan Hervé , Young Colin , Jefferson-Loveday Richard
Published: August 2017

High loads and bearing life requirements make journal bearings the preferred choice for use in high power, epicyclic gearboxes in jet engines. In contrast to conventional, non-orbiting journal bearings in epicyclic star gearboxes, the kinematic conditions in epicyclic planetary arrangements are much more complex. With the planet gears rotating about their own axis and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and affect the external flow behavior of the oil exiting the journal bearing.

This paper presents a literature and state-of-the-art knowledge review to identify existing work performed on cases similar to external journal bearing oil flow. In order to numerically investigate external journal bearing oil flow, an approach to decompose an actual journal bearing into simplified models is proposed. Later, these can be extended in a step-wise manner to allow key underlying physical phenomena to be identified. Preliminary modeling considerations will also be presented. This includes assessing different geometrical inlet conditions with the aim of minimizing computational requirements and different numerical models for near-wall treatment. The correct choice of near-wall treatment models is particularly crucial as it determines the bearing’s internal and external thermal behavior and properties. The findings and conclusions are used to create a three dimensional (3D), two-component computational fluid dynamic (CFD) sector model with rotationally periodic boundaries of the most simplistic approximation of an actual journal bearing: a non-orbiting representation, rotating about its own axis, with a circumferentially constant, i.e. concentric, lubricating gap. The inlet boundary conditions for simulating the external oil flow are generated by partly simulating the internal oil flow within the lubricating gap. In order to track the phase interface between the oil and the air surrounding the bearing, the Volume of Fluid (VoF) method is used. The quality of the CFD simulations of the domain of interest is not only dependent on the accuracy of the inlet conditions, but is also dependent on the computational mesh type, cell count, cell shape and numerical methods used. External journal bearing oil flow was simulated with a number of different mesh densities and the effect on the flow field behavior will be discussed. Two different operating temperatures, representing low and high viscosity oil, were used and their effect on the flow field behavior will also be assessed.

In order to achieve the future objective of creating a design tool for routine use, key areas will be identified in which further progress is required. This includes the need to progressively increase the model fidelity to eventually simulate an orbiting journal bearing in planetary configuration with an eccentric, i.e. convergent-divergent, lubricating gap.
Experimental Investigation of Dust-Pan Shaped Hole Film Cooling Characteristics on Pressure Side of a Turbine Blade in a Linear Transonic Cascade
Authors: Fu Zhong-yi , Zhu Hui-ren , Liu Cong , Li Zheng
Published: August 2017

An experimental research of film cooling performance of three single dust-pan shaped hole rows in different positions of a turbine blade was carried out in the short-duration transonic linear cascade at stationary condition, which can model realistic engine aerodynamic conditions. The effects of inlet Reynolds number (Rein = 2.5 × 105∼7.5 × 105), isentropic exit Mach number (Mais = 0.71∼0.91) and coolant blowing ratio (M = 0.8∼2.6) on film cooling effectiveness are investigated. Three single hole rows are located at 11.7%, 36.3% and 55.6% relative arc on the pressure sides of three enlarged blade models respectively. The adiabatic film cooling effectiveness are derived from the surface temperatures based on transient heat transfer measurement method. The results show that in the range of blowing ratios studied in the present paper, for location 3 the cooling effectiveness decreases a lot with blowing ratio increasing due to the lift-off of coolant at high blowing ratios, while for location 1 and 2, the film cooling effectiveness increases with blowing ratio increasing, because the strong favorable pressure gradient and high concave curvature near the leading edge lead to a good attachment of coolant on the surface. At M≤1.0 conditions, the film cooling effectiveness of location 1 and 2 is lower than that of location 3, which reflects that strong favorable pressure gradient and high concave curvature weaken film cooling performance at low blowing ratio conditions, while the effect is opposite when M is greater than 1.0. For location 1, the highest general cooling performance is obtained at Rein = 2.5 × 105 condition, and for location 2, the change of Rein has different effects on cooling effectiveness in different regions. In the range of Mais studied in this paper, the change of Mais has little effect on film cooling effectiveness.
Hybrid RANS/LES Simulation of Corner Stall in a Linear Compressor Cascade
Authors: Xia Guoping , Medic Gorazd
Published: August 2017

Current design-cycle Reynolds-Averaged Navier-Stokes-based CFD methods have the tendency to over-predict corner-stall events for axial-flow compressors operating at off-design conditions. This shortcoming has been demonstrated even in simple single-row cascade configurations [1]. Here we report on the application of hybrid RANS/LES predictions for simulating the corner-stall data from the linear compressor cascade work conducted at Ecole Centrale de Lyon [2][3][4]. This benchmark data set provides detailed loss information while also revealing a bimodal behavior of the separation which, not surprisingly, is also not well modeled by RANS. The hybrid RANS/LES (or DES) results presented here predict bimodal behavior similar to the data only when special treatment is adopted to resolve the leading-edge endwall region where the horseshoe vortex forms. The horseshoe vortex is shown to be unstable, which produces the bimodal instability. The DES simulation without special treatment or refinement in the horseshoe vortex region fails to predict the bimodal instability, and thus the bimodal behavior of the separation. This in turn causes a gross over-prediction in the scale of the corner-stall. The horseshoe vortex region is found to be unstable with rolling of the tertiary vortex over the secondary vortex and merging with the primary horseshoe vortex. With these flow dynamics realized in the DES simulations, the corner stall characteristics are found to be in better agreement with the experimental data, as compared to RANS and standard DES approaches.
Lateral Equilibrium Position Analysis Program With Applications to Electric Submersible Pumps
Authors: Norrbin Clay S. , Childs Dara W.
Published: August 2017

The long length of sub-sea Electric Submersible Pumps (ESPs) requires a large amount of annular seals. Loading caused by gravity and housing curvature changes the Static Equilibrium Position (SEP) of the rotor in these seals. This analysis predicts the SEP due to gravity and/or well curvature loading. The analysis also interfaces displays the rotordynamics around the SEP.

A static and rotordynamic analysis is presented for a previously studied ESP model. This study differs by first finding the SEP and then performing a rotordynamic analysis about the SEP. Predictions are shown in a horizontal and a vertical orientation. In these two configurations, viscosities and clearances are varied through 4 cases: 1X 1cP, 3X 1cP, 1X 30cP, and 3X 30cP.

In a horizontal, straight-housing position, the model includes gravity and buoyancy on the shaft. At 1cP-1X and 1cP-3X, the horizontal statics show a moderate eccentricity ratio for the shaft with respect to the housing. With 30cP-1X, the predicted static eccentricity ratio is low at 0.08. With 30cP-3X, the predicted eccentricity ratio increases to 0.33.

Predictions for a vertical case of the same model are also presented. The curvature of the housing is varied in the Y-Z plane until rub or close-to-wall rub is expected. The curvature needed for a rub with a 1X 1cP fluid is 7.5 degrees of curvature. Curvature has little impact on stability. With both 1X 30cP and 3X 30cP, the maximum curvature for a static rub are over 25 degrees of curvature. Both 1X 30cP and 3X 30cP remain unstable with increasing curvature.
Experimental and Numerical Investigation of the Mutual Interaction Between Liner Film Cooling and Combustor Swirl Flow
Authors: Andreini Antonio , Becchi Riccardo , Facchini Bruno , Mazzei Lorenzo , Picchi Alessio , Vitale Ignazio , Tolpadi Anil
Published: August 2017

In the continuous demand of increasing cooling efficiency for novel combustor liners, it is necessary to have a comprehensive understanding of the interaction of hot gases with coolant flows. The aim of the present study is the experimental characterization of the flow field and the measurement of liner heat transfer coefficient in a combustion chamber model equipped with an axial swirler and a liner slot cooling scheme.

The test rig geometry consists in a linear three sector chamber fed by an open loop blower. The system is operated at isothermal conditions. A highly swirled main stream flow is achieved by considering an injector geometries that produce flow structures which interact with film cooling flow delivered by a simplified slot at the inner wall of the liner. To study the effects of this mutual interaction, the flow field and the liner heat transfer are investigated at different slot cooling and injector flow rates.

A 2D PIV (Particle Image Velocimetry) technique is employed to investigate the test section flow field on two different planes. An experimental campaign focused on liner heat transfer measurement is carried out using a TLC (Thermochromic Liquid Crystals) steady state technique with a thin Inconel heating foil fed by two copper bus bars.

Results obtained indicate an appreciable role of film cooling flow on both swirler aerodynamics and the liner heat transfer coefficient. When the slot cooling flow rate is increased, the observed peak of heat transfer coefficient, due to liner-swirl flow interaction, gradually reduces. This is a consequence of a reduction in swirling jet expansion when slot cooling is increased, which also affects the amount of flow recirculation due to vortex breakdown.
Numerical Research on Effects of Shroud Contraction on Tip Leakage Flow and Overall Performance of Axial Compressors
Authors: Zhang Yufan , Li Jiabin , Ji Lucheng
Published: August 2017

In the design of an axial compressor, many designers take advantage of this technology and employ contracted shroud. What is its impact on tip leakage flow and overall performance of the axial compressor? What is its mechanism? In this paper, the NASA Rotor67 is taken as a research case, and parameterized study is conducted to investigate the effects of shrouds with different inclined angles. The inclined angles range from 0° to 13°. Based on the above described plan, numerical simulations are conducted to the original rotor67 and its modified versions with inclined shroud. To remove factors that might interfere the results, original Rotor 67 and all the blades with modified shroud should be compared to their optimal design status. Adjoint optimization is used to give the optimum blade corresponding to each shroud with different blade inclined angles.

Then adjoint optimization was used again to give the optimum meridional flowpath for all the cases with different shroud inclined angles. This provides a powerful tool to evaluate the accuracy of the aforementioned prediction. A detailed comparison is made between the original flowpath and the optimized ones.

Numerical results are analyzed in detail between original Rotor67 and its modified versions. The results show that the shroud inclined angle has an effect on the overall performance of the blade. It will also redistribute the velocity triangles and the chordwise distribution of aero load in the tip region. Hence it exerts great influence on the tip leakage flow field in the meantime. Shroud with suitable inclined angles can suppress the developing of leakage vortex , and the best-inclined angle for rotor 67 is found to be roughly 11°.
A Thermodynamic Model to Quantify the Impact of Cooling Improvements on Gas Turbine Efficiency
Authors: Uysal Selcuk Can , Liese Eric , Nix Andrew C. , Black James
Published: August 2017

Cooling of turbine hot-gas-path components can increase engine efficiency, reduce emissions, and extend engine life. As cooling technologies evolved, numerous blade cooling geometries have been, and continue to be proposed by researchers and engine builders for internal and external blade and vane cooling. However, the impact of these improved cooling configurations on overall engine performance is the ultimate metric. There is no assurance that obtaining higher cooling performance for an individual cooling technique will result in better turbine performance because of the introduction of additional second law losses, e.g. exergy loss from blade heat transfer, cooling air friction losses, fluid mixing, etc. and thus the higher cooling performance might not always be the best solution to improve efficiency.

To quantify the effect of different internal and external blade cooling techniques and their combinations on engine performance, a cooled engine model has been developed for industrial gas turbines and aero-engines using MATLAB Simulink®. The model has the flexibility to be used for both engine types, and consists of uncooled on-design, turbomachinery design and a cooled off-design analysis in order to evaluate the engine performance parameters by using operating conditions, polytropic efficiencies, material information and cooling system information. The cooling analysis algorithm involves a Second Law analysis to calculate losses from the cooling technique applied.

The effects of variations in engine parameters such as turbine inlet temperature, by-pass ratio, and operating temperature are studied. The impact of variations in metal Biot number, thermal barrier coating Biot number, film cooling effectiveness, internal cooling effectiveness and maximum allowable blade temperature on engine performance parameters are analyzed. Possible design recommendations based on these variations, and direction of use of this tool for new cooling design validation, are presented.
Electrochemical Carbon Separation in a SOFC-MCFC Poly-Generation Plant With Near-Zero Emissions
Authors: Mastropasqua Luca , Campanari Stefano , Brouwer Jack
Published: August 2017

High temperature fuel cells have been studied as a suitable solution for Carbon Capture and Storage (CCS) purposes at a large scale (>100 MW). However, their modularity and high efficiency at small-scale make them an interesting solution for Carbon Capture and Utilisation at the distributed generation scale when coupled to appropriate use of CO2 (i.e., for industrial uses, local production of chemicals etc.). These systems could be used within low carbon micro-grids to power small communities in which multiple power generating units of diverse nature supply multiple products such as electricity, cooling, heating and chemicals (i.e., hydrogen and CO2).

The present work explores fully electrochemical power systems capable of producing a highly pure CO2 stream and hydrogen. In particular, the proposed system is based upon integrating a Solid Oxide Fuel Cell (SOFC) with a Molten Carbonate Fuel Cell (MCFC). The use of these high temperature fuel cells has already been separately applied in the past for CCS applications. However, their combined use is yet unexplored. Moreover, both industry and US national laboratories have expressed their interest in this solution.

The reference configuration proposed envisions the direct supply of the SOFC anode outlet to a burner which, using the cathode depleted air outlet, completes the oxidation of the unconverted species. The outlet of the burner is then fed to the MCFC cathode inlet which separates the CO2 from the stream. Both the SOFC and MCFC anode inlets are supplied with pre-reformed and desulfurized natural gas. The MCFC anode outlet, which is characterised by a high concentration of CO2, is fed to a CO2 separation line in which a two-stage Water Gas Shift (WGS) reactor and a PSA/membrane system respectively convert the remaining CO into H2 and remove the H2 from the exhaust stream. This has the significant advantage of achieving the required CO2 purity for liquefaction and long-range transportation without requiring the need of cryogenic or distillation plants. Moreover, the highly pure H2 stream can either be sold as transportation fuel or a valuable chemical.

Furthermore, different configurations are considered with the final aim of increasing the Carbon Capture Ratio (CCR) and maximising the electrical efficiency. Moreover, the optimal power ratio between SOFC and MCFC stacks is also explored.

Complete simulation results are presented, discussing the proposed plant mass and energy balances and showing the most attractive configurations from the point of view of total efficiency and CCR.
Towards Full 3D Numerical Simulation of Whirl Motions Stemming From Unilateral Contact Constraints in Aircraft Engines
Authors: Paltrinieri Jérémy , Nyssen Florence , Parent Marie-Océane , Batailly Alain
Published: August 2017

The reduction of nominal clearances between a rotating bladed-disk and its surrounding casing yields a very significant increase of the overall engine efficiency. However, the smaller the clearances, the higher the risk of structural contacts between static and rotating components that may lead to hazardous interaction phenomena. In particular, at the fan stage of an aircraft engine, impacts between the rotating bladed-disk and the casing may generate forward or backward whirl motions induced by the precession of the shaft axis of rotation. In such specific configuration, an accurate modeling of interaction phenomena requires to account for both centrifugal and gyroscopic effects on the rotor. This contribution addresses the development of efficient reduced-order models of industrial finite element models embedding both centrifugal and gyroscopic effects. Proposed developments are validated on an academic model and are then applied on the finite element model of an aircraft engine fan stage. Results obtained with the academic model underline that the impact of gyroscopic effects on the rotor’s dynamics is essentially related to the frequency split of 1-nodal diameter free-vibration modes of the first modal family. Results presented on the industrial finite element models are limited to a few case studies as a proof-of-concept.
Rotordynamic Performance of Hybrid Air Foil Bearings With Regulated Hydrostatic Injection
Authors: Zamanian Yazdi Behzad , Kim Daejong
Published: August 2017

Air foil bearing (AFB) technology has made substantial advancement during the past decades and found its applications in various small turbomachinery. However, rotordynamic instability, friction and drag during the start/stop, and thermal management are still challenges for further application of the technology. Hybrid air foil bearing (HAFB), utilizing hydrostatic injection of externally pressurized air into the bearing clearance, is one of the technology advancements to the conventional AFB. Previous studies on HAFBs demonstrate the enhancement in the load capacity at low speeds, reduction or elimination of the friction and wear during starts/stops, and enhanced heat dissipation capability. In this paper, the benefit of the HAFB is further explored to enhance the rotordynamic stability by employing a controlled hydrostatic injection. This paper presents the analytical and experimental evaluation of the rotordynamic performance of a rotor supported by two three-pads HAFBs with the controlled hydrostatic injection, which utilizes the injections at particular locations to control eccentricity and attitude angle. The simulations in both time domain orbit simulations and frequency-domain modal analyses indicate a substantial improvement of the rotor-bearing performance. The simulation results were verified in a highspeed test rig (maximum speed of 70,000 rpm). Experimental results agree with simulations in suppressing the subsynchronous vibrations but with a large discrepancy in the magnitude of the subsynchronous vibrations, which is a result of the limitation of the current modelling approach. However, both simulations and experiments clearly demonstrate the effectiveness of the controlled hydrostatic injection on improving the rotordynamic performance of AFB.
Machine Learning for Turbulence Model Development Using a High-Fidelity HPT Cascade Simulation
Authors: Weatheritt Jack , Pichler Richard , Sandberg Richard D. , Laskowski Gregory , Michelassi Vittorio
Published: August 2017

The validity of the Boussinesq approximation in the wake behind a high-pressure turbine blade is explored. We probe the mathematical assumptions of such a relationship by employing a least-squares technique. Next, we use an evolutionary algorithm to modify the anisotropy tensor a priori using highly resolved LES data. In the latter case we build a non-linear stress-strain relationship. Results show that the standard eddy-viscosity assumption underpredicts turbulent diffusion and is theoretically invalid. By increasing the coefficient of the linear term, the farwake prediction shows minor improvement. By using additional non-linear terms in the stress-strain coupling relationship, created by the evolutionary algorithm, the near-wake can also be improved upon. Terms created by the algorithm are scrutinized and the discussion is closed by suggesting a tentative non-linear expression for the Reynolds stress, suitable for the wake behind a high-pressure turbine blade.
Industrial and Marine Development Policy Study and Practices for GT28 Gas Turbine
Authors: Wen Xueyou , Xiao Dongming , Zhao Ningbo
Published: August 2017

As a high performance gas turbine, GT28 combines with a two-spool gas generator and a free power turbine. Under the condition of ISO, its power and efficiency are 28MW and 37% for marine mechanical propulsion, respectively. Considering the design characteristics and operating performance of GT28 gas turbine can meet the requirements of many marine propulsion, mechanical driven and electrical power generation, and this paper introduces the potential application of GT28 gas turbine in different industrial and marine fields. On this basis, the related key technologies are discussed briefly. Finally, a derivative network is presented to describe the relationships of different application and development of GT28 gas turbine.
Effect of Outer Fin Axial Gap on the Sealing Effectiveness and Fluid Dynamics of Radial Rim Seal
Authors: Li Zhigang , Li Jun , Song Liming , Gao Qing , Yan Xin , Gao Tieyu
Published: August 2017

The modern gas turbine is widely applied in the aviation propulsion and power generation. The rim seal is usually designed at the periphery of the wheel-space and prevented the hot gas ingestion in modern gas turbines. The high sealing effectiveness of rim seal can improve the aerodynamic performance of gas turbines and avoid of the disc overheating. Effect of outer fin axial gap of radial rim seal on the sealing effectiveness and fluid dynamics was numerically investigated in this work. The sealing effectiveness and fluid dynamics of radial rim seal with three different outer fin axial gaps was conducted at different coolant flow rates using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and SST turbulent model solutions. The accuracy of the presented numerical approach for the prediction of the sealing performance of the turbine rim seal was demonstrated. The obtained results show that the sealing effectiveness of radial rim seal increases with increase of coolant flow rate at the fixed axial outer fin gap. The sealing effectiveness increases with decrease of the axial outer fin gap at the fixed coolant flow rate. Furthermore, at the fixed coolant flow rate, the hot gas ingestion increases with the increase of the axial outer fin gap. This flow behavior intensifies the interaction between the hot gas and coolant flow at the clearance of radial rim seal. The preswirl coefficient in the wheel-space cavity is also illustrated to analyze the flow dynamics of radial rim seal at different axial outer fin gaps.
Analysis of the Influence of Geometric Structure on the Rotationally Induced Ingress
Authors: Zhenxia Liu , Jun Ma , Jianping Hu , Lifen Zhang
Published: August 2017

Rotating air inside the wheel-space creates a radial gradient of pressure which drives the gas ingress through the rim seal. This kind of reason for the gas ingestion is called rotationally induced ingress (RI). The minimum sealing flow rate was proportional to the seal-clearance. The geometric structure, including the position of the seal-clearance, is also important to predict the minimum sealing flow rate for RI ingestion. This paper gets the sealing efficiency and the flow results of different geometric structure through the method of 3D steady compressible CFD (Computational Fluid Dynamics). Because the analysis of the influence of geometry is given under the condition of RI ingestion, a 3D model without turbine blades has been chosen.

Some experiments initially revealed that the different seal-clearance positions have different sealing efficiency. However, what position would have best sealing efficiency was not given. If the position of seal-clearance is selected in the rotor disc or the static disc, the effect of the “pump” of the rotor disc is more obvious, which makes the gas ingestion serious. When the position of seal-clearance is near the rotor disc, the gas is fully mixed with the cooling air after the ingestion and then flows to the side of the static disc. Therefore, the sealing efficiency of the structure, whose seal-clearance position is near the rotor disc, will be higher than that, whose seal-clearance position is close to the static disc. When the fluid flows to the static disc, the velocity triangle shows that a barrier will be created between the cavity and mainstream in a particular seal-clearance position, which makes the efficiency higher than other positions.
Large Eddy Simulation of Flow and Heat Transfer Mechanism in Matrix Cooling Channel
Authors: Luan Yigang , Yang Lianfeng , Wan Bo , Sun Tao
Published: August 2017

Gas turbine engines have been widely used in modern industry especially in the aviation, marine and energy fields. The efficiency of gas turbines directly affects the economy and emissions. It’s acknowledged that the higher turbine inlet temperatures contribute to the overall gas turbine engine efficiency. Since the components are subject to the heat load, the internal cooling technology of turbine blades is of vital importance to ensure the safe and normal operation. This paper is focused on exploring the flow and heat transfer mechanism in matrix cooling channels. In order to analyze the internal flow field characteristics of this cooling configuration at a Reynolds number of 30000 accurately, large eddy simulation method is carried out. Methods of vortex identification and field synergy are employed to study its flow field. Cross-sectional views of velocity in three subchannels at different positions have been presented. The results show that the airflow is strongly disturbed by the bending part. It’s concluded that due to the bending structure, the airflow becomes complex and disordered. When the airflow goes from the inlet to the turning, some small-sized and discontinuous vortices are formed. Behind the bending structure, the size of the vortices becomes big and the vortices fill the subchannels. Because of the structure of latticework, the airflow is affected by each other. Airflow in one subchannel can exert a shear force on another airflow in the opposite subchannel. It’s the force whose direction is the same as the vortex that enhances the longitudinal vortices. And the longitudinal vortices contribute to the energy exchange of the internal airflow and the heat transfer between airflow and walls. Besides, a comparison of the CFD results and the experimental data is made to prove that the numerical simulation methods are reasonable and acceptable.
Heat and Mass Transfer Characteristics of Water Droplets in Wet Compression Process
Authors: Liu Chunlei , Li Xiang , Zhang Hai , Zheng Qun
Published: August 2017

Wet compression technology is an economic and effective approach to improve the performance of gas turbine. In the process of wet compression, the gas turbine engine will ingest a certain amount of water, which can influence the overall performance of the engine. Thermodynamic process and performance of compressor are influenced significantly by heat and mass transfer of the injected water droplets.

This study is a new research of investigating theoretically the water droplets effects on the heat and mass transfer characteristics. It focuses on the aerodynamic and thermodynamic effects of the two-phase flow in the compressor stage. The application of Computational Fluid Dynamics (CFD) is the basic method to examine the details of the flow in an axial compressor stage and how it is affected by the presence of water, especially by the water droplets. The computation of water droplets characteristics, are provided by a simulation model of the code named CFX. Considering the change in aerodynamics and thermodynamics feature due to the water droplets, the compressor stage’s performance variations are analyzed. The movement and the evaporation of the water droplets in a compressor stage are simulated and analyzed by using unsteady numerical methods under different water injecting conditions in this paper. The movement characteristics of water droplets in compressor passage are investigated to understand the flow mechanisms responsible for wet compression formation process.

The investigation of water droplets in compression can help to understand some phenomenons by using wet compression technology. The flow of water droplets between rotor blades are analyzed by using computational fluid dynamics method. Full coupling between gas and water droplets are adopted, allowing gas and water droplets to affect each other. Many motion parameters of water droplets are researched, such as slip velocity, Weber number and Reynolds number. The forces acting on water droplet are also discussed. Aerodynamic breakup of water droplets and interactions between water droplets and wall are taken into consideration at the same time.

The results indicate that: (1) The motion of water droplets in compression areor mainly controlled by drag force. The motion parameters of water droplets changes mostly at the entrance of flow passage between rotor blades, and the turbulence intensity and breakup strength of water droplets reaches their maximum at the entrance. (2) The flow angle of water droplets is bigger than gas in rotor region due to their inertia, which can explain why water droplets have bigger separation degree and are easier to flow toward blade pressure surface. (3) The motion of water droplets in stator region is also important to be investigated for wet compression, and the motion analysis of single water droplets between blades is still needed to be developed, so more investigation will be carried out.