bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Use of PSP to Determine the Rim Sealing Effectiveness
Authors: Orsini Lorenzo , Picchi Alessio , Facchini Bruno , Bonini Alessio , Innocenti Luca
Published: September 2023

The control of cavities sealing has been a challenging problem since early gas turbine development stages and several aspects regarding the flow physics and the modelling of rim seal flows, especially in terms of unsteady phenomena, still represent an open question. Fundamental test cases have been extensively used in the open literature to characterize the level of ingestion by varying the main flow parameters and the geometrical features. In most of them, the seal effectiveness is measured by using taps connected to a gas analyzer used to sample the concentration of a reference foreign gas (generally CO2) on the stator surface used to seed the purge flow. Consequently, the results are usually single point measurements and unsteady effects are inevitably neglected. Moreover, the intrusiveness of the approach must be carefully checked and the application on the rotor side demands for complex slip-rings or telemetry. To overcome these limitations, the current work presents the application of the Pressure Sensitive Paint (PSP) technique to the study of hot gas ingestion phenomena on a single stage rotating cold rig. By using an oxygen-free gas such as N2 as purge flow, the PSP were used to measure the partial pressure of oxygen at the wall through the wide optical accesses present in the rig. Then, the collected 2D distributions of pressure were related to the seal effectiveness inside the wheel-space. The proposed methodology was firstly validated through a comparison with the data obtained from standard gas sampling and then applied as main experimental technique to characterize the seal ingestion. The analysis of the results highlighted the capabilities of the PSP technique to fast collect data on both stator and rotor side, including the tip of the seal tooth where non uniform efficiency distributions in the circumferential direction have been detected.
New Compression Solution to Decarbonize Petrochemical Plants
Authors: Berterame Domenico , Gabriele Serena
Published: September 2023

Decarbonization is unavoidable and urgent, however it still sounds like an undefined foggy vision, with detrimental impact on any project budget and risk profile, due to novelty introduction. The purpose of this paper is turning upside down this concept and show with a real example that proven technology can reduce CO2 footprint and, at the same time, squeeze costs even in well-established petrochemical process, like PDH one. The journey has started more than 10 years ago, based on the idea of increasing machine rpm to get more work from it! Thanks to investment in new materials, improved bearings, enhanced predictability together with an extensive test campaign on a full-scale prototype Baker Hughes introduced in 2015 the High-Pressure Ratio Compressor (HPRC). This consists in a new generation technology able to cover with a single compressor body the duty usually requiring multiple casings in series. Bottom line: no process change, same (or better) efficiency, less hardware/material and therefore reduced CO2 impact and cost. This solution was successfully deployed for natural gas compression and today it plays a key role in the H2 world. The today idea is to introduce it in the fast-growing petrochemical market and specifically as Reactor effluent compressor, one of the key equipment in PDH plants. That proprietary process requires 2 compressor bodies however can be properly handled by a single casing without any performance change when applying HPRC design. This results in a proven technology delivering on decarbonization while reducing CAPEX and OPEX.
Stability Analysis of an Ammonia-Based Emulsion With Additives for Lean Combustion
Authors: Di Gloria Pasquale , Strafella Luciano , De Giorgi Maria Grazia , Ciccarella Giuseppe , Castelluzzo Gregorio , Baldassarre Francesca , Ficarella Antonio
Published: September 2023

In recent years, considerable progress has been made in exploring new fuel additives to reduce emissions and improve combustion performance compared to conventional fuels. Reducing total nitrogen oxide (NOx) emissions can be achieved by reducing the flame temperature using a fuel emulsified with water and/or using ammonia-based nano-additives such as urea. For the preparation of emulsified fuel, it is desirable to achieve greater stability of the emulsified fuel with a minimum cost of chemicals and energy, so that it can be used for a longer period. The stability of an emulsion is influenced by the water-fuel ratio and the amount of surfactant. In the present work, the influence of dispersed urea nanoparticles, water, and surfactant (Span 85/Tween 80) on the combustion performance and emission characteristics of aviation fuel has been investigated. The experimental campaign was carried out in a 300-kW swirled turbine combustor. It consists of a cylindrical combustion chamber with three optical windows, equipped with pressure sensors, thermocouples, and an exhaust gas analyzer. The experimental campaign was conducted with the same air/fuel ratio (Φ) to facilitate the comparison of different emulsions. The focus is on the stability of the emulsion with the use of surfactants. Chemiluminescence imaging was performed to characterize the effects of the additive on flame emissions. A spectrometer was also used to verify the presence of particulate matter under different fuel conditions. Finally, NOx, CO, CO2, and O2 emissions were measured.
Part I: Validation and Verification of CFD Analysis for NASA SDT Transonic Fan Stage Test Rig
Authors: Robles Vega Gregorio , Lee Daryl Y. , Ni Michael , Ni Ron-Ho
Published: September 2023

In this paper, the NASA SDT (Source Diagnostic Test) was used for CFD code validation as it provides experimental data that includes an operating map of the turbomachinery rig and 2D radial profiles at multiple operating points. The configuration with the baseline OGV geometry is analyzed using steady RANS simulations with the mixing plane approximation at the rotor/stator interface and Wilcox K-w 98 two equation turbulence model.

An operating map consisting of seven speedlines and an operating line, 126 points in total, was generated and compared against experimental data. Since only the 100% speed fan geometry was available, it was used for all speeds. The CFD model showed good agreement with 1D mean performance data at design speed. The pressure rise and efficiencies across the bypass stage were predicted within 0.5%. Off-design predicted performance captured the bulk pressure rise and efficiency. Comparisons of radial profiles showed good agreement to data at the fan exit. The CFD model adequately predicted the shape and magnitude as compared to data.

The validation and verification of the NASA SDT fan and baseline OGV configuration provides a foundation for a multipart effort aimed at understanding the impact of airframe installation effects on turbomachinery performance.
A Probabilistic Approach to Turbine Uncertainty
Authors: Bhatnagar Lakshya , Paniagua Guillermo , Clemens Eugene , Bloxham Matthew
Published: September 2023

Efficiency is an essential metric for assessing turbine performance. Modern turbines rely heavily on numerical computational fluid dynamic (CFD) tools for design improvement. With more compact turbines leading to lower aspect ratio airfoils, the influence of secondary flows is significant on performance. Secondary flows and detached flows, in general, remain a challenge for commercial CFD solvers; hence, there is a need for high-fidelity experimental data to tune these solvers used by turbine designers. Efficiency measurements in engine-representative test rigs are challenging for multiple reasons; an inherent problem to any experiment is to remove the effects specific to the turbine rig. This problem is compounded by the narrow uncertainty band required to detect the incremental improvements achieved by turbine designers. Efficiency measurements carried out in engine-representative turbine rigs have traditionally relied upon assumptions such as constant gas properties and neglecting heat loss.

This research presents an uncertainty framework that combines inputs from experiments and computational tools. This methodology allows quantifying uncertainty for high-fidelity efficiency data in engine-representative turbine facilities. This manuscript presents probabilistic sampling techniques to allow for uncertainty propagation. The effect of rig-specific effects, such as heat transfer and gas properties, on efficiency is demonstrated. Sources of uncertainty are identified, and a framework is presented which divides the sources into bias and stochastic. The framework allows the combination of experimental and numerical uncertainty. Gaussian Regression models are developed to obtain speed-lines for the turbine map using the uncertainty of the measured efficiency.
Purge-Mainstream Interactions in a Turbine Stage With Rotor Endwall Contouring
Authors: Mesny Alex W. , Pountney Oliver J. , Scobie James A. , Li Yan Sheng , Sangan Carl M.
Published: September 2023

Purge flows are prevalent in modern gas turbine design allowing for increased turbine entry temperatures. The purge flow passes through a rim seal and interacts with the mainstream flow, modifying the blade secondary flow structures and reducing stage efficiency. These structures may be controlled using End Wall Contouring (EWC), though experimental demonstration of their benefit is seldom reported in the literature. The optically accessible turbine at the University of Bath was designed to directly measure and visualize the flow field within the blade passage for a rotor with EWC.

The single-stage turbine enables phase-locked flow field measurements with volumetric Particle Image Velocimetry (PIV). Purge flow was supplied to investigate a range of operating conditions in which the secondary flow structures were modified. The modular turbine rotor allowed for expedient change of a bladed ring, or bling, featuring non-axisymmetric EWC.

The identified secondary flow structures were the Pressure-Side leg of the Horse Shoe Vortex (PS-HSV) and an Egress Vortex (EV) of concurrent rotational direction. An increase in purge flow rate monotonically shifted the EV toward the suction-side (SS) of the adjacent blade. The migration of the PS-HSV towards the SS caused the two aforementioned vortices to merge.

The EWC rotor design included a Leading-Edge (LE) feature to alter the PS-HSV, and a trough to guide the EV low spanwise in the passage and maintain displacement from the adjacent suction side. The EWC rotor was found to be effective at altering the formation and positioning of the secondary flow structures at a range of purge flow conditions.
Experimental and Numerical Study of Purge Flow Effects in an HP Turbine Stage
Authors: Payne Daniel , Kanjirakkad Vasudevan
Published: September 2023

To improve the efficiency of gas turbines, it is essential that designers understand the interaction between primary and secondary air systems in critical regions of the engine. One of the most important regions is the rotor-stator cavity of the first stage high pressure turbine, where the high temperatures could cause a catastrophic failure if the supply of secondary air is too low or the cavity is not effectively sealed. This paper presents experimental results and analysis of data from the Rim Seal (RiSe) rig at the University of Sussex. This is a single stage engine representative axial turbine facility and allows for measurements to be made of the interaction between the main annulus flow and the coolant flow within the rotor stator cavities. Experiments are completed at a set operating point of the turbine, at an Axial Reynolds number of 7 × 105 and a fixed Pressure Ratio of 2.5, whilst the purge flow is varied from 0.05% to 1% of the main annulus flow. Numerical simulations are completed using a Reynolds Averaged Navier-Stokes (RANS) solver for a periodic sector of the test section. The simulations conducted include those with the cavity domain alone and those where both the cavity and the main annulus domains are combined. This allows for comparisons to be made of the different physical mechanisms associated with the interaction between the main annulus and cavity flows. In this paper we will present comparisons between the experimental measurements and numerical simulations for a range of purge flow rates and simulation setups. Analysis of the simulations along with that of the experimental data will explain the various aero-thermal mechanisms involved in the cavity regions.
Resolving Issues and Failures of Diaphragms in Turbines
Authors: Gowreesan Vamadevan , Greaves Wayne , Grebinnyk Kyrylo
Published: September 2023

Diaphragms are used in steam turbines to regulate the flow of the steam to the rotating blades. The regulation or the change of flow direction is to increase the efficiency of the turbine. Though diaphragms are non-rotating parts, they may experience elevated temperature and they may also be subjected to high stress and or cyclic stresses during service. As a result, they may develop failures and other issues due to long term service. The vanes of the diaphragms may develop cracks and the diaphragms may develop dishing which is generally a result of creep deformation resulting from long term service at elevated temperature.

This paper discusses different types of diaphragms and their fabrication methods first. The fabrication of the diaphragm involves casting or machining of vanes. Then these vanes or vane segments are welded to the inner and outer rings to make the rigid diaphragms.

Then some of the common failures and issues these diaphragms see in their service will be discussed. These will be illustrated with some recent field examples. This will be followed by some approaches to mitigate the risk of these failures and issues.
On the Aeroacoustic Properties of a Prandtl-Fan
Authors: Czwielong Felix , Benz Julian , Ocker Christof , Renz Andreas , Sedlmajer Michael , Merkel Markus , Becker Stefan
Published: September 2023

Axial fans are used in many machines and equipment in close proximity to people. Therefore, acoustic optimization of the fans is essential to protect the well-being of people and to ensure a quiet environment. The sound emission of fans is determined, among other factors, by the selected load distribution of the blades and the resulting angles of attack and chord lengths. A bell-shaped load distribution developed by Prandtl in 1933 was applied to a benchmark fan and investigated aeroacoustically. A total of three axial fans were numerically simulated for flow and acoustics at the design point. One of these fans is an international benchmark fan, the second is a fan with the same isoenergetic load distribution but a different chord length, and the third fan has the Prandtl load distribution and the same modified chord length. Based on the simulations performed, it was shown that a larger chord length leads to an improvement in the aerodynamic and acoustic properties of the axial fan with isoenergetic load distribution. This is due to the reduced blade tip overflow and the associated reduced pressure fluctuations at the blade surface. The bell-shaped load distribution increases the efficiency of the fan, but also increases the total sound emission by 1.5 dB compared to the axial fan with constant chord length and isoenergetic load distribution. This is due to the increased interaction between the blades, as the blade tip vortex hits the following blade leading edge more frontally. This increase occurs despite a reduction in the strength of the blade tip vortex. Compared to the benchmark fan, the changes in chord length and Prandtl’s load distribution resulted in a sound reduction of 3.9 dB and an increase in efficiency of 4%. It was shown that the modifications can be used for future aeroacoustic optimization of axial fans.
Fast Prediction of Combustor Stability Limits in Humidified Micro Gas Turbines Using Hybrid 0D/1D Model
Authors: Pappa Alessio , Bricteux Laurent , De Paepe Ward
Published: September 2023

Cycle humidification is considered as an interesting route to enhance the micro Gas Turbine (mGT) operational flexibility, ensuring a place for mGTs in future small-scale decentralized power production. Indeed, humidifying the mGT cycle when there is no heat demand increases the electrical efficiency of the cycle, and thus the operational flexibility of the unit. However, the rather small operating range of the mGT combustor under these diluted conditions remains the main limitation, restricting the humidification rate, and thus the potential cycle improvement. Therefore, a complete characterization of the combustor performances for a range of operating conditions in combination with an increasing water-to-air ratio allows quantifying the operability limit of the engine under these unconventional diluted conditions. To improve the mGT cycle further, the limits to reach stable, complete, and low emissions combustion are assessed using a hybrid 0D/1D model of the combustor of typical mGT, namely the Turbec T100 mGT, for different humidification pathways (steam or water injection, saturation tower, ...). This model combines 0D Chemical Reactor Networks with 1D unstretched laminar flame calculations. The results of this computationally fast and flexible model are experimentally validated for both dry and wet cycle operation. For moderate water fractions, the simulation results show that complete combustion with low CO emissions, but at reduced temperature, could be achieved at a constant equivalence ratio compared to the dry reference case. At increased water fraction, stable and complete combustion at similar CO emission levels could still be achieved by increasing the equivalence ratio, compensating for the reduced temperature in the combustion chamber. Finally, at high water fractions, the results show unacceptably high CO levels, as a result of incomplete combustion due to the too-low temperature or too-low flame speed. With these simulations, we were able to assess the influence of humidified conditions on the combustion stability as well as to determine the operating limit helping so future cycle improvements.
Integrated Design of a Variable Cycle Engine and Aircraft Thermal Management System
Authors: Clark Robert A. , Tai Jimmy , Mavris Dimitri
Published: September 2023

The integrated design of a variable cycle engine (VCE) and an aircraft thermal management system (TMS) is investigated. The integrated system is designed using the multiple design point (MDP) approach in order to achieve required performance metrics at points other than the cycle design condition. The VCE architecture under investigation is a three-stream design where the third-stream is split off after the fan, exhausting through a separate third-stream nozzle. The primary air stream passes through a low-pressure compressor before splitting into an inner bypass stream and a core stream. The inner bypass and core streams mix aft of the low-pressure turbine and exhaust through a core nozzle. The variable cycle engine utilizes multiple variable geometry components: variable compressor inlet guide vanes (IGVs), a variable area bypass injector (VABI) at the inner bypass / core stream mixing plane, and variable throats in the two exhaust nozzles. The TMS architecture modeled is an open-loop air cycle system (ACS) that uses air bled from the high-pressure compressor as the working medium. The bleed air passes through heat exchangers (located in the engine third stream) before and after passing through a supercharging compressor, and is then expanded through two turbines to reach the low temperatures required to absorb heat from the aircraft cooling system. The effect of integrating the TMS into the engine design loop is investigated. In addition, a comparison is made to prior studies, where the same TMS architecture was connected to a low-bypass ratio turbofan engine, with the heat exchangers placed in either a ram-air stream or the engine bypass stream. The comparison shows that the variable cycle engine is able to improve heat dissipation capability versus a ram-air cooled system, while eliminating the airframe integration impact that comes with a separate ram-air stream. Lastly, the impact of modulating the variable geometry features on overall cooling capability is investigated. Results are presented for individual operating points as well as at the aircraft mission level.
A Machine Learning Approach for the Prediction of Time-Averaged Unsteady Flows in Turbomachinery
Authors: Blechschmidt Dominik , Mimic Dajan
Published: September 2023

Recent advances in deep learning have led to its increased application in the field of fluid dynamics. By using a data-driven approach instead of a more conventional numerical approach, it is possible to reduce the computational cost of fluid simulations significantly. Especially unsteady computational fluid dynamics (CFD) are known to require a considerable amount of time and resources. Hence, it is common practice in turbomachinery to model the flow as steady by averaging the flow between the rotor and stator in a so-called mixing plane. While this approach is numerically efficient, the full interactions between the rotor and the stator can no longer be predicted accurately due to the averaged upstream flow field. Contrary to this, the time-average of an actual unsteady flow does not contain such a modeling error while still resulting in a flow field that is decoupled from its temporal fluctuations. In this work, we introduce a graph neural network (GNN), which predicts the time-averaged flow field of a rotor stage in an axial compressor based on its steady solution. Because GNNs are able to operate directly on the high-fidelity CFD mesh, we are able to retain the spatial resolution necessary to depict more complex flow behaviour. Consequently, the fidelity of our predictions can compete with conventional high-accuracy flow simulations. Our model is capable of predicting the velocity, pressure, density, and temperature field of a single rotor stage from a 4½-stage axial compressor test case and shows significant improvements compared to the steady state solution, while also being substantially faster than conventional unsteady CFD simulations.
Multi-Objective Numerical Optimization of Radial Turbines
Authors: Fuhrer Christopher , Kovachev Nikola , Vogt Damian M. , Mahalingam Ganesh Raja , Mann Stuart
Published: September 2023

The growing demand of high flexibility and wide operating ranges of radial turbines in turbocharger applications necessitates new methods in the turbomachinery design process. Often, design criteria such as high performance at certain operating conditions or low inertia contradict the requirement for high durability. This paper demonstrates a newly developed optimization approach for radial turbines that allows to optimize for several design objectives. The presented approach is based on a parametric model of the turbine wheel geometry.

On the one hand, the model is designed to capture the most important geometry and design features, and on the other hand, it is flexible for use on various machines. A surrogate model-based genetic algorithm is used to optimize the geometries with respect to several objectives, including efficiency, durability (HCF), Low-Cycle Fatigue (LCF), inertia and mass. Certain operating points or criteria can be particularly emphasized and specified constraints throughout the process allow for customized optimization. The simulations underlying the optimization are state-of-the-art CFD and FE analyses, involving the respective components.

The newly developed and fully automated approach includes tasks of different disciplines. In the end, a selection of several promising geometries is examined more intimately to finally find a most suitable geometry for the given application. For the current study, this geometry has been manufactured and tested on a hot-gas-test facility to successfully validate the design process.
Effect of Centrifugal Force of Gas Film on the Load Capacity of Thrust Gas Bearing
Authors: Kim Daejong
Published: September 2023

A modified Reynolds Equation including centrifugal force of gas film was derived, and it was used to study the effect of gas film centrifugal force and associated streamline on the load capacity of both rigid and foil thrust bearings operating in hydrodynamic and hybrid modes. The thrust bearings have 6 pads with an outer diameter of 82 mm and an inner diameter of 47 mm with typical aper-flat geometry. The setup for the simulations is a single-acting air thrust bearing operating at various ambient pressures and isothermal temperature. Air was chosen for the gas film for the investigations, but the modified Reynolds Equation can handle any general gas films through non-dimensional parameter governing the centrifugal force. The simulations were performed with varying ambient pressure from 1 to 9 bar. The simulation results at different ambient pressures and temperatures are presented in forms of pressure profiles, streamlines, and bearing’s load capacity. The bearings’ load capacity becomes worse when the centrifugal force is considered at very low temperature, and the reduction of the load capacity grows more noticeable with the increase of the ambient pressure and the decrease of the ambient temperature. However, at higher temperature where centrifugal force is not large enough to create large leakage, the centrifugal force helps to redistribute the streamline to favorable way to increase the load capacity.
Aerodynamic Parametrization of Last Stage Steam Turbine Blades
Authors: Schippling Stefan , Fuhrer Christopher , Vogt Damian M.
Published: September 2023

The present paper introduces a novel method to parametrize blade profiles of last stage steam turbines with aerodynamic data. This offers the possibility to specifically influence the flow in order to reduce thermodynamic relaxation losses without changing the desired expansion and redirection of the flow from the ini-tal blade profile. The idea is that the flow channel between two adjacent blades can be regarded as a bent nozzle and the nozzle contour is calculated using aerodynamic data. This nozzle is bent over an ideal streamline, which represents the desired flow redirection, and completed with leading and trailing edges to form a blade profile. In the presented parametrization, the expansion rate is used as variable to adapt the blade profile, as it has a direct influence on condensation and thus thermodynamic relaxation losses. In addition to the distribution of the expansion rate and static pressure along the streamline, the coordinates of the streamline, the total pressure and total enthalpy at the inlet of the profile as well as the distance of the throat are necessary to describe the blade geometry. The new aerodynamic parametrization is capable of accurately representing a Laval-nozzle and a stator cascade. With adapting expansion rates, wetness losses are reduced by 3.5 % for the nozzle and by 2 % for the blade profile.
Impact of Preheating on Flame Stabilization and NOx Emissions From a Dual Swirl Hydrogen Injector
Authors: Magnes Hervé , Marragou Sylvain , Aniello Andrea , Selle Laurent , Poinsot Thierry , Schuller Thierry
Published: September 2023

Flame stabilization, structure and pollutant emissions are investigated experimentally on a swirled injection system operating with globally lean air/hydrogen mixtures at atmospheric conditions and moderate Reynolds numbers. This injector consists of two coaxial ducts with separate injection of hydrogen into a central channel and of air into an annular channel. Both streams are swirled. The resulting flames exhibit two stabilization modes. In one case, the flame takes an M-shape and is anchored to the hydrogen injector lips. In the second case, the flame is aerodynamically stabilized above the injector and takes a V-shape. Regions of existence of each stabilization mode are determined according to the operating conditions. For low air flow rates, the flame can be either anchored or lifted above the hydrogen injector lips depending on the path followed to reach the operating condition. At high air flow rates, the flame is always lifted regardless of the trajectory followed. The impact of air inlet temperature on these stabilization regimes is then evaluated from T = 300 K up to 770 K. Flame re-attachment is shown to be controlled by edge flame propagation and the impact of preheating is well reproduced by the model. Unburnt hydrogen and NOx emissions are finally evaluated. Unburnt hydrogen is only observed for global equivalence ratios below 0.4 and at ambient inlet temperature. NOx emissions decrease when the global equivalence ratio is reduced. Furthermore, at fixed global equivalence ratio, NOx emissions decrease as the thermal power increases, regardless of air preheating and the flame stabilization regime. At high power, NOx emissions reach an asymptotic value that is independent of the thermal power. The impact of flame shape, air preheating and combustion chamber wall heat losses on NOx production is also evaluated. Finally, NOx emissions are shown to scale with the adiabatic flame temperature Tad at the global equivalence ratio and the global residence time inside the combustor.
Computational Modeling of Hydrogen and Hydrogen-Methane Fuel Combustors for Gas Turbine Engine Applications
Authors: Prasad Mathiyalagan Senthil , Khot Mahaveer , Subramanian Sundaresa “Mani”
Published: September 2023

Related to the Sustainable Aviation Programs, focused on technologies to achieve some ambitious decarbonization goals for aircraft engines, research and development efforts into using alternative fuels, such as Sustainable Aviation Fuel (SAF) and Hydrogen. In relation to these efforts, this proposed study will focus on using Hydrogen and Hydrogen fuel blends in aircraft engine combustor to study the impact of reducing CO2 and NOx levels at typical operating conditions. Along with other SAF, Hydrogen is one of the most promising fuels for the Aviation industry to reduce CO2 levels significantly. However, NOx emissions are a bigger challenge in a Hydrogen-Air combustion system. Understanding the NOx emissions and its levels along with the temperature distribution in the combustor becomes even more challenging with Hydrogen as the primary fuel. Numerical simulations of combustion, with appropriate representation of chemical kinetics is expected to provide more insights about the temperature distribution and NOx emissions, thus aiding better combustor designs. At the present time, limited computational studies are underway in the gas turbine community. In this paper, multiple computational fluid dynamics (CFD) analyses have been completed by varying the combinations of mass fraction of Hydrogen and Methane in the fuel mixture for a NASA published public domain gas turbine combustor geometry under two different fuel flow conditions. All the previous calculations were for non-reacting cases, primarily to study the fuel-air mixing characteristics. The Hydrogen percentage in the mixture was varied from 0 to 100% (all Methane to fully Hydrogen) in steps of 25%. In this particular study, reacting flow simulations were performed for a pure Hydrogen and 50% H2-50% CH4 mixture and are presented and discussed. Converge CFD software was utilized for all the reacting flow calculations using the referenced NASA combustor geometry under combustor inlet conditions at the design point. The numerical results are presented and discussed with the available experimental data for the combustion performance and emissions.
Physics Discovery of Engineering Applications With Constrained Optimization and Genetic Programming
Authors: Luan Lele , Jacobs Ryan , Ghosh Sayan , Wang Liping
Published: September 2023

Discovering physics from data have the potential to advance our understanding and prediction of a system where the governing physics are unknown but experimental data are available. Physics-based models are conventionally obtained from rigorous first principles derivations such as conservation laws or knowledge-based phenomenological derivations. However, inferring physics-based models remains challenging for many real-world complex systems with intertwined and coupled multi-physics that are challenging to derive from first principles. In recent years, data-driven physics discovery has become an attractive research topic across many scientific disciplines due to the increasing richness of observational data and advances in machine learning. Various data-driven physics discovery algorithms have been proposed to extract simple but appropriate models governing the systems from the observed data. Among the proposed algorithms, genetic programming (GP) based symbolic regression (SR) plays a dominant role. Here, we build a general GP based SR platform to discover physical models from observations for real-world systems. The platform is used to solve an optimization problem where the outcome is a set of human-readable equations that the user can select from based on accuracy vs parsimony trades. The discovery process also considers the prior knowledge of experts, which manifests as constraints to enhance the embedding of physics and avoid overfitting. The discovered models not only have high interpretability but also demonstrate good extrapolation performance.
Thermoacoustic Characterization of a Premixed Multi Jet Burner for Hydrogen and Natural Gas Combustion
Authors: Beuth Jan Paul , Reumschüssel Johann Moritz , von Saldern Jakob G. R. , Wassmer Dominik , Ćosić Bernhard , Paschereit Christian Oliver , Oberleithner Kilian
Published: September 2023

In this study, the acoustics and flame dynamics of a prototype multijet burner with 19 individual mixing tubes for operation with pure hydrogen and pure natural gas are experimentally investigated. The burner transfer matrix of the jet burner is determined from experimental data and acoustic network modeling, showing very good agreement. The burner plate and attached mixing tubes are shown to be well approximated with an acoustic model of a perforated plate with bias flow. Accordingly, the burner is found to feature a high level of acoustic damping. A comparison of the flame dynamics of the two fuels considering mass flow and equivalence ratio variation reveals that the flame transfer functions (FTFs) are dominated by a convective mechanism originating from the upstream end of the mixing tubes where the fuel is injected. Consequently, these are most likely fluctuations in the equivalence ratio that feature two characteristic time scales: the convection time in the mixing tubes and along the flame. The overall qualitative shape of the FTFs for hydrogen and natural gas at equal thermal power is found to be similar, with the dynamics of the natural gas flames being more responsive to acoustic excitation, as evident in generally higher gain values. Distinctly less pronounced phase decays are observed for hydrogen compared to natural gas operation. Moreover, the FTFs for H2 are found to change only slightly across the considered range of equivalence ratios. At the same time we observe only small changes in the corresponding static flame shapes. These observation are consistent with the hypothesis of a dominant convective mechanism. In conclusion, the study provides valuable information on the acoustics and flame dynamics of multijet burners for flexible fuel operation.
Characterization of a Novel AM Micromix Nozzle Burning Methane to Hydrogen
Authors: Durocher Antoine , Fan Luming , Francolini Benjamin , Füri Marc , Bourque Gilles , Bergthorson Jeffrey M. , Yun Sean , Vena Patrizio
Published: September 2023

As the energy landscape transitions to low/zero-carbon fuels, gas turbine manufacturers are targeting fuel flexible operation with natural gas, syngas, and hydrogen-enriched mixtures. Having a single geometry that can support the different fuel blends requested by clients can accelerate the transition to cleaner energy generation and mitigate the environmental impact of gas turbines. Toward this goal, micromix combustion technology has received significant interest, and when coupled with additive manufacturing, novel injector geometries with unique configurations may be capable of stabilizing premixed, partially-premixed, and diffusion flames using fuel mixtures ranging from pure methane to pure hydrogen. In this work, a preliminary investigation of this micromix concept is performed in the Atmospheric Combustion Rig at the National Research Council Canada. Flame stability maps are obtained for fuel lean mixtures of H2/CH4 ranging from 0/100, 70/30, 90/10, to 100/0%, by volume. Multiple flame shapes are observed depending on the fuel mixture and combustion mode selected. PIV, OH and acetone planar laser-induced fluorescence (PLIF), and acoustic measurements provide additional insights into the combustion process of these novel burners to better understand the stability mechanisms. The quality of the fuel-air mixing from the premixed and micromix injectors is assessed using acetone as a tracer for the fuel, while simultaneous OH-PLIF measurements provide an indication of the post-flame regions in the flow. Acoustic measurements complete the current dataset and provide combustion dynamics maps measuring the normalized pressure amplitudes and identifying the dominant frequencies. The preliminary characterization of this AM micromix nozzle shows promising fuel flexibility with wide stability margins and low combustion dynamics for this single nozzle burner.
Sensor System Maturation for Gas Turbine Engine Particulate Ingestion Monitoring
Authors: Papadopoulos George , Bivolaru Daniel , Siu Spencer
Published: September 2023

Experimental studies of turbine engine sand, dust, and ash ingestion have shown that certain constituents, typically such as Calcium, Magnesium, Aluminum, and Silicon (CMAS) compound minerals and/or Chlorides and Sulfates, are particularly detrimental to engine turbine components. These reactive media undergo a phase change from solid to semi-solid as they pass through the combustion section of the engine under certain conditions characterized by size and mass. The phase change allows them to adhere to various turbine components including but not limited to stator vanes, rotor blades and shrouds. Unfortunately, with no on-board sensing technology the only warning signs that the flight crew has to an impeding airborne particle ingestion problem are lagging indicators, such as the St. Elmo’s Fire effect seen at night when charged ash particles hit the aircraft or a sulphurous smell and dust within the cabin. Hence, a sensor system that can measure the composition, size and concentration of particles being ingested by a gas turbine while in flight can provide pilots the warning they need to limit damage by either exiting the area or taking other actions to avoid prolonged exposure that can lead to serious damage mechanisms, both in the military where operational limits are always pushed to the extreme, and in the commercial area where safety is paramount. The current paper reports on the maturation of an in-situ, advanced monitoring and measurement of sand (AMMoS) sensor system that can be integrated at several places within an engine (e.g. aircraft inlet, engine inlet, engine bypass, engine gas path) with minimum modifications. The AMMoS system can provide measurements of composition, size and concentration for particles ingested by the engine. The current paper describes maturation efforts involving AMMoS system validation for particle size and system operation under various particle loading conditions. A dedicated test apparatus was assembled to facilitate the use of image-based diagnostics for providing independent measurements on the particle laden flow environment.
Biocompatibility and Mechanical Behaviour Studies on Wire-Arc Additive Manufactured Stainless Steel 316L and Shape Memory Alloy (NiTi) Materials for Biomedical Implants
Authors: T. Geethapriyan , Badhai Jhasketan , Karthik Sibi , Sonawane Avinash , Palani I. A.
Published: September 2023

Stainless steel 316L (SS316L) and Nickel-titanium alloy (NiTi), which are additively manufactured metallic biomaterials, are explore for their biocompatibility and mechanical properties in bio-implant applications. The nickel-titanium alloy (NiTi) has been suggested for exceptional thermal shape memory, super elasticity, and high damping qualities compared to Stainless steel 316L (SS316L). In this present study, the input process variables such as voltage, wire-feed rate, dwell time and argon gas flow rate have been maintained constantly (fixed) based on the trial experiments. The metallic biomaterials (Stainless steel 316L (SS316L) and Nickel-titanium alloy (NiTi)) are fabricated using a wire-arc additive manufacturing process and it is utilized to study the mechanical properties such as tensile, yield strength and % elongation. The additive manufactured biomaterials such as Stainless steel 316L (SS316L) and Nickel-titanium alloy (NiTi) have been compared and studied the impact of biocompatibility (Cytotoxicity) and anti-bacterial property for surgical implant applications. From the result, it has been found that the shape memory alloy (NiTi) has higher ultimate tensile and yield strength than the Stainless steel 316L (SS316L) due to its high corrosion resistance, super elasticity, and shape memory behaviour. In addition, the cytotoxic effects of both biomaterials (SS 316L and NiTi alloy) on L929 mouse fibroblast cells were examined in the cell culture media. The biocompatibility and anti-bacterial characteristics of SS 316L and NiTi alloy has been investigated, which would support its use as a surgical implant.
Experimental Investigation of the Surface Topography in Terms of Process Parameters During Picosecond Laser Machining of Polycrystalline Diamond
Authors: Zhang Yushun , Han Fuzhu
Published: September 2023

Because of its significant impact on the friction and surface quality of a cutting process, the surface topography of the flank face is one of the most crucial indicators for the quality of Polycrystalline Diamond (PCD) cutting tools machined with ultrafast laser. Therefore, it is necessary to study the effect of process parameters on the topography of the machined surface. In this study, a picosecond laser with 1064nm wavelength was used to generate and polish kerfs on PCD samples. An orthogonal experiment was conducted to evaluate the impact of process parameters on surface roughness. The results indicated that the surface roughness decreased with increased pulse energy, polishing depth, or decreased laser polishing speed. As the number of polishing cycles increased, the surface roughness tended to first decrease and then increase. The results of variance analysis demonstrated that the polishing speed and polishing depth have a significant impact on the surface roughness. Additionally, surface topography and microgrooves formed on the side wall of the kerfs were studied using a digital microscope. Finally, process optimization was carried out based on the previous experiment. A surface roughness of Ra0.16μm was obtained and recasting layer was fully removed. This study shows that the surface topography of the flank face of PCD cutting tools can be improved with an appropriate combination of the cutting depth, cutting speed, number of polishing cycles, and pulse energy during ultrafast laser processing.
Intelligent Uncertainty Handling Using Artificial Neural Networks in a Programmatic Logic Controller-Based Automation System
Authors: Lai Enoch , Ma Jianfeng
Published: September 2023

The manufacturing industry is relying more and more on artificial intelligence (AI). Despite this, Programmable Logic Controllers (PLCs), one of the most common industrial tools, still lack AI integration. This means that PLCs are still very rigid and struggle with handling uncertainties. Uncertainties are input data that the controller has not been programmed to address. Uncertainties can be caused by variation in sensor data or other factors. Because PLCs struggle to handle uncertainties, this makes them very tedious to program. Implementing AI into the PLC may eliminate this problem. This study answers the question of whether AI can be implemented into a PLC (Allen-Bradley). To do this, a Levenberg-Marquardt backpropagation artificial neural network (ANN) was trained in MATLAB to approximate a mathematical function. A representation of the ANN was then constructed using the PLC ladder logic diagram by implementing the weight and bias values obtained from the trained ANN. The PLC-implemented ANN’s results were validated by comparing its output values to those of MATLAB trained ANN. Negligible differences between the outputs indicate that implementing an ANN framework into the PLC ladder logic code is viable. The ability to implement an ANN into the PLC code may help PLCs handle uncertainties better. This implementation may help the PLC become more versatile for more jobs and may also make it easier to program. Future studies should test out this method of implementation and apply it in real world applications.
Experimental Analysis on Tissue Fracture in Needle Insertion Process
Authors: Hu Yingda , Du Shilun , Lei Yong
Published: September 2023

During needle insertion procedures, the insertion of the needle is accompanied by tissue fracture, which is the result of needle tissue interactions. The tissue fracture toughness is an important parameter to describe the resistance of tissue to crack generation, as well as to quantify the energy absorbed by the tissue during crack propagation. Fracture toughness can be affected by many factors, such as needle insertion speed, needle tip bevel angel and tissue Young’s modulus. However, existing studies on fracture toughness estimation did not consider the effect of Young’s modulus. In this paper the influence of three major factors on fracture toughness, specifically, insertion velocity, needle diameter and tissue Young’s modulus, are systematically studied. testbed is constructed, and the experiments are designed using polyvinyl alcohol tissue phantom with different insertion velocity, needle diameter and Young’s modulus. Experiments results show that the fracture toughness is positive proportional to insertion velocity, and Young’s modulus, and negative proportional to needle diameter. In addition, the sensitivity analysis shows that the effect of Young’s modulus to fracture toughness is less than other influencing factors.