bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-Parameters Sensitivity Analysis of Overall Cooling Effectiveness on Turbine Blade and Numerical Investigation of Internal Cooling Structures on Heat Transfer
Authors: Liu Runzhou , Li Haiwang , You Ruquan , Tao Zhi
Published: October 2022

Turbine blade overall cooling effectiveness is a conjugate result under the influence of various parameters. In order to analyze the overall cooling effectiveness more accurately, we have to categorize all the influencing parameters. This paper builds a one-dimensional conjugate heat transfer model with four parameters which are adiabatic film cooling effectiveness, heat transfer coefficient ratio between blade external surface (hg) and internal surface (hi), internal coolant warming factor (Tg−Tw,iTg−Tc), Biot number. The effects of different internal cooling structures, film hole inclined angle and blowing ratio on flow and heat transfer characteristic were numerically investigated based on flat-plate film hole model and impingement-effusion model, where 3-D steady RANS method with SST k-ω model was used. V-rib, 45° inclined rib, 90° rib and dimple were adopted to compare with smooth internal channel. The results show that four dimensionless parameters (adiabatic film cooling effectiveness, heat transfer coefficient ratio, warming factor, Biot number) are positively correlated with overall cooling effectiveness. The overall cooling effectiveness is the most sensitive to adiabatic film cooling effectiveness, followed by warming factor. This indicates that the adiabatic film cooling effectiveness is the worthiest to improve. The numerical results show that the ribs and dimple structures have little influence on the distribution of adiabatic film cooling effectiveness and Biot number on the mainstream side. The 45° rib presents higher overall cooling effectiveness.
Experimental Analysis of an Axial Compressor Operating Under Flow Distortion
Authors: Baretter Alberto , Joseph Pierric , Roussette Olivier , Romanó Francesco , Dazin Antoine
Published: October 2022

In aircraft engines, compressor stages can encounter situations in which the flow is distorted at rotor inlet, for example during particular flight maneuvers, or due to the shape of the inlet of the airframe. The main objective of this paper is to investigate experimentally the effect of an inlet flow distortion on the internal flow dynamic and its consequences on the performance and operability of these machines. The distortion was generated by a porous plate grid installed upstream of the compressor. Eight total pressure rakes placed downstream of the grid were used to evaluate the distortion. Unsteady pressure measurements were performed on the casing at different axial and azimuthal positions to investigate the dynamic flow behavior at nominal conditions, at an operating point close to stall and during the transition to stall. 2D-2C PIV maps, synchronized with the runner position, were obtained on rotor blade-to-blade planes at three different spanwise positions (79%, 51%, 18% of the blade span). Three relative angular positions of the grid to the laser sheet were investigated at two different flow rates, namely the nominal flow rate and a flow rate close to stall. These three positions are corresponding to the laser sheet cutting through i/ the center of the grid’s wake and ii/ the two edges of the grid. The impact of the distortion on the performance of the compressor is analyzed and compared to existing models. The impact of the flow dynamic will also be considered, especially in operations close to the stall limit.
LES of Turbulent Premixed CH4/H2/Air Flames With Stretch and Heat Loss for Flame Characteristics and Dynamics
Authors: Kutkan Halit , Amato Alberto , Campa Giovanni , Tay-Wo-Chong Luis , Æsøy Eirik
Published: October 2022

This paper presents large eddy simulation (LES) turbulent combustion models for premixed methane/hydrogen/air mixtures which account for stretch, heat loss and Lewis number effects by means of a previously proposed turbulent flame speed expression [1]. In this expression stretch and heat loss effects are introduced by means of strained non-adiabatic laminar consumption speed calculations in fresh-to-burnt counter flow configurations with detailed chemistry, and preferential diffusion of hydrogen is accounted for by calculating an effective Lewis number of the reactants.

To validate and analyze the performance of the models, large eddy simulations of fully premixed atmospheric bluff body stabilized methane/hydrogen/air flames are compared against experimental measurements [2, 3]. Heat release distributions and mean flame shapes are compared against OH* chemiluminescence data. Flame dynamics are investigated by extracting flame transfer functions (FTFs) with system identification (SI) methods and comparing them with measured FTFs from experiments.
The Influence of Combustor Hot Streaks on the Aerodynamic Performance of a Turbine Center Frame
Authors: Badžek Ena , Patinios Marios , Farisco Federica , Heitmeir Franz , Göttlich Emil
Published: October 2022

This paper investigates the influence of combustor temperature non-uniformities on modern engine turbine center frames (TCFs). Due to their position in an engine, coupled with the trends of more aggressive designs, increased turbine inlet temperatures (TIT), and utilization of lean-burn combustors, turbine center frames are exposed to even higher temperatures and non-uniform temperature flow fields. These temperature non-uniformities, or hot streaks, were previously studied at the combustor - high-pressure turbine (HPT) interface, but there is no available research in the open literature that clarifies their influence on the TCF performance. A new test bench, designed specifically for fundamental research on hot streaks, was set up at the Institute for Thermal Turbomachinery and Machine Dynamics at the Graz University of Technology. The test bench features a 90° sector-cascade of an engine representative TCF geometry, equipped with a hot streak generator and a flow conditioning grid. Experimental data was gathered by means of five-hole-probe area traverses at the TCF inlet and outlet planes. Two individual clocking positions of hot streaks in respect to the leading edges of the struts were investigated, as well as three different radial positions for each of the clocking scenarios. Hot streaks were injected upstream of the flow conditioning grid, generating a representative temperature ratio at the TCF inlet plane. Results show that the hot streaks have migrated radially outwards and are characterized by different temperature distributions, depending on the injection position. An increase in pressure loss and thermal loading of the strut and of the shroud is observed.
Numerical Investigation of Potential Flow Induced Vibrations of Steam Turbine Last Stage Rotor at Low Load Operation – Part 1: Sensitivity to Flutter Occurrence
Authors: Pinelli Lorenzo , Mariotti Filippo , Arnone Andrea , Marconcini Michele , Arcangeli Lorenzo , Ciuchicchi Lorenzo , Maceli Nicola
Published: October 2022

The present paper is part of a two-part publication that aims to numerically investigate the occurrence of flow induced vibrations in a steam turbine last stage rotor at low load operations. Experimental and numerical investigations at low load operations are gaining interest in the design of steam turbine blades due to the effort required to achieve carbon free objectives, which lead to higher flexibility of steam power plants. Reliable machines able to work safely at low load conditions are required for coupling with renewable energy sources and high output power plants. In this part 1 paper, the last rotor of a low-pressure steam turbine module installed in concentrated solar plants has been numerically evaluated to assess the flutter stability at different low load conditions, while the companion part 2 deals with the investigation of unsteady aerodynamic instabilities which might arise in the last stage rotor.

In the present work, aerodynamic and flutter simulations were performed at different load conditions, from the design point to very low mass flows to achieve a real sensitivity of flutter behavior to the mass flow rate. By means of steady state multistage results, aerodynamic performance and flow structures were evaluated. The decreasing mass flow and blade load reveal the formation of wide separation areas both on the last rotor pressure side and in the exhaust duct, bringing the stage up to ventilating conditions. The flutter analyses were performed with an uncoupled non-linear method in order to estimate the aerodynamic damping for a selection of mode-shape families. From aerodamping results it was possible to observe the trend in the flutter response at different load conditions and it is evident how the shock wave system near the tip plays a major role in energy exchange between flow field and the vibrating profile. The results show an overall flutter stability of the blade up to very low load conditions. This means that for these type of rotor profiles and corresponding applications, flutter occurrence is not the main issue, and further vibration causes like rotating instabilities have to be investigated as demonstrated in the companion part 2 paper.
A Numerical Study on the Effects of Circumferential Positions of Combustor Hot Streaks on a TCF Configuration
Authors: Benauer Richard , Schreck Stefan , Leitl Peter , Badzek Ena , Patinios Marios , Farisco Federica
Published: October 2022

This work presents the results of numerical investigations conducted within the framework of a project focused on studying the influence of combustor hot streaks onto the aerodynamic performance of a TCF representative geometry. Different circumferential positions of the hot streaks, in respect to the leading edges of the high pressure turbine (HPT) stator vanes, were examined in order to determine changes in the flow field and its influence on the downstream components. Numerical investigations were carried out at Bionic Surface Technologies GmbH using the commercial tool ANSYS CFX. Transient simulations were performed to obtain the flow-field and capture the propagation of the hot streaks through the HPT stage into the TCF. Time averaged five-hole-probe measurements, taken from the TU Graz transonic test turbine facility (TTTF), were used as the initial boundary conditions for the simulations. Results are showing that the circumferential position of the hot streaks influences the temperature distribution at the TCF outlet since the hot streaks follow the fluid migration in the TCF, and are therefore affected by secondary flow structures originating from the fluid interaction with the HPT and TCF struts. Results also present an increase of pressure loss below 1%, for the hot streaks simulations.
Design of an Air-Cooled Condenser for CO2-Based Mixtures: Model Development, Validation and Heat Exchange Gain with Internal Microfins
Authors: Illyés Viktoria , Morosini Ettore , Doninelli Michele , David Pierre-Luc , Guerif Xavier , Werner Andreas , Di Marcoberardino Gioele , Manzolini Giampaolo
Published: October 2022

CO2 blends provide tremendous advantages when used as a working fluid in transcritical power cycles with respect to pure CO2. The benefits become especially apparent if coupled with concentrated solar power since increasing the critical temperature of the blend with respect to pure CO2 allows dry condensing at high ambient temperatures in locations of high solar radiation. One key cycle component is the cooler, which in this work is designed as an air-cooled condenser with a MATLAB in-house code. The internal, condensation heat transfer model used in this paper relies on a correlation developed by Cavallini (2006). The model itself is validated against experimental data from a test rig for heat transfer measurements on a CO2 + R1234ze(E) mixture. The resulting design of the condenser is compared with the commercial software HTRI for a specific case study which is representative of the condenser of a recuperated cycle working with a CO2 + C6F6 blend. The authors also present an upgraded heat exchanger design with microfinned tubes, the DIESTA tubes, and groovy fins on the air side. The design of the heat exchanger adopting the mixture is compared to a case with pure CO2 as the working fluid.
Experimental Study on the Optimization of the Sensor Arrangement for Blade Tip Timing Measurement
Authors: Tian Jie , Zhang Zhiwei , Chai Pengfei , Wang Shang , Chen Yong , Ouyang Hua
Published: October 2022

As a means of non-contact measurement of blade vibrations, blade tip timing (BTT) has good application prospects for blade design verification and health monitoring. In BTT, the sensor arrangement directly determines the effectiveness of the extracted signal and ultimately affects the quality of the identified vibration parameters. In previous research on optimizing sensor arrangements, the position of each sensor is often selected from among multiple uniformly distributed virtual positions, which limits the optimization space. Moreover, to verify the performance of a sensor arrangement, a high-precision experimental calibration platform is required. However, it is often difficult for the precision to meet the requirements for a benchmark due to an inability to measure the actual blade vibrations. This paper optimized the sensor arrangement by simultaneously considering the mutual coherence and the approximate distance between sensing matrices for an equiangular tight frame in arbitrary-angle compressive sensing method. To avoid the uncertainty in blade displacement conversion in traditional calibration, such as with strain gauges, a laser displacement sensor connected to a slip ring was used to measure directly the displacement of the blade due to vibration. Besides, a macro-fiber composite was used to apply an excitation with a precise frequency to the blade at different speeds to make the blade vibrate synchronously or asynchronously. Then the performance of sensor arrangements optimized by the proposed method as well as other methods, such as mutual coherence, were verified on the self-developed BTT experimental calibration platform. The experimental results show that the signals identified with the optimized sensor arrangements are in good agreement with measurements made by the laser displacement sensor. The amplitude accuracy was more than 76.5% and 91.3% for synchronous and asynchronous vibrations, respectively. Moreover, the identification results were stable after data from 1 or 2 random sensors were removed. This shows the method has good reconstruction accuracy and sensor redundancy.
Predictive Modelling of Local Film-Cooling Flow on a Turbine Rotor Blade
Authors: DeShong Eric T. , Berdanier Reid A. , Thole Karen A.
Published: October 2022

In the turbine section of a modern gas turbine engine, components exposed to the main gas path flow rely on cooling air to maintain hardware durability targets. Therefore, monitoring turbine cooling flow is essential to the diagnostic and prognostic efficacy of a condition-based operation and maintenance (CBOM) approach. This study supports CBOM goals by leveraging supervised machine learning to estimate relative changes to local film-cooling flow rate using surface temperature measured on the pressure side of a rotating turbine blade operating at engine-relevant aerothermal conditions. Throughout the lifetime of a film-cooled turbine component, characteristics of the film-cooling flow — such as film trajectory and cooling effectiveness — vary as degradation-driven geometry distortions occur, which ultimately affects the relationship between the model input and the model output – film-cooling flow rate predictions. The present study addresses this complication by testing a data-driven model on multiple turbine blades of the same nominal design, but with each blade exhibiting different localized film-cooling flow characteristics. By testing the model in this manner, strategies for mitigating the detrimental effects of film-cooling flow characteristic variations on model performance were investigated, and the corresponding flow rate prediction accuracy was quantified.
Effects of Internal Coolant Crossflow on Film-Cooling Performance of Double-Jet and Cylindrical Holes
Authors: Zhu Huaitao , Xie Gongnan , Zhu Rui , Sunden Bengt
Published: October 2022

In this paper, the effects of internal coolant crossflow on double-jet holes were simulated and compared with two rows of cylindrical holes under three blowing ratios (M = 0.5, 1.0, and 1.5), with an established and validated turbulence model. The results show that double-jet holes can provide better film cooling performance for the three different blowing ratios compared with cylindrical holes. As the blowing ratio increases, the superiority of double-jet holes becomes more obvious. The introduction of crossflow can significantly enlarge the coolant coverage area of cylindrical holes, and increase the laterally-averaged film cooling effectiveness. For double-jet holes, the internal coolant crossflow also increases the laterally averaged film cooling effectiveness, but the improvement is limited. For the −45° compound angle film hole of double-jet holes, the internal coolant crossflow decreases the normal velocity (momentum), and makes the coolant to attach on the plate. However, for the other hole, the influence is opposite, the normal velocity (momentum) is increased and the coolant is detached from the plate.
Application of 3D Inverse Design Method on a Transonic Compressor Stage
Authors: Zhang Luying , Ray Saurya Ranjan , Zangeneh Mehrdad
Published: October 2022

In this paper, a three-dimensional viscous inverse design method is presented. The blade geometry is parameterized by aerodynamic variables such as blade loading, which allows direct control of the aerodynamic flow field. With a specified stacking axis and thickness distribution, the algorithm solves the flow field and blade geometry iteratively until the prescribed blade loading is matched. Meanwhile, the fast turn-around time of the inverse design method enables a substantial reduction of time and computational resources, which is particularly advantageous when the product development period is limited. The method is demonstrated through the redesign of an axial transonic compressor (Darmstadt Transonic Compressor), which has been extensively studied by experimental research and numerical simulations. The interaction between the shock wave, the tip clearance flow, and the boundary layer flow in the tip region is crucial for the compressor performance and operational stability. The redesigned compressor reduces the shock strength and the induced flow loss in the tip region through blade loading control. The performance improvement is verified by computational fluid dynamics (CFD) simulations for a stage configuration. A detailed flow field is obtained and compared to the baseline design. The loss reduction mechanism is analyzed by using entropy production rate to better understand the design impact.
Numerical Simulation of Multi-Scale Oil Films on a Rotating Cup Using VOF and Coupled Eulerian Thin-Film-DPM Approaches
Authors: Nicoli A. , Singh K. , Jefferson-Loveday R. , Ambrose S. , Mouvanal S.
Published: October 2022

In this study, the newly developed Nottingham Gas Turbine and Transmission Research Centre (G2TRC) Bearing Chamber Test Module is presented and investigated computationally. The module houses a rotating cup and shaft configuration in order to simulate the droplet generation processes from an aeroengine bearing. The objective of this paper is to model the thin film that develops over the rotating cup surface, comparing a high-fidelity Volume of Fluid (VOF) approach against the Eulerian Thin-Film Model (ETFM). Whilst a VOF approach has previously demonstrated good accuracy for modelling of films over a rotating surface, the ETFM can provide a comparable solution at a much-reduced computational cost. Simulations are performed over a range of shaft speeds and oil flow rates to represent engine operating conditions. This study presents the very first simulation of an oil film over a rotating cup geometry, with a shaft running through the centre of the cup. Computationally, a VOF periodic sector is compared to ETFM simulations run on an equivalent 30° periodic domain. At planes before the rotating cup edge, both film thicknesses and axial velocities are compared. The high-fidelity VOF simulations demonstrate that with an increase in rotational speed, the film thickness over the rotating cup reduces; whilst an increase in oil flow rate produces a thicker film. Compared to the high-fidelity VOF simulations, the ETFM provides good agreement in terms of both film thickness and axial velocities. Overall, the ETFM is shown to be able to produce a similar film to the VOF approach at a much-reduced computational cost, offering a numerical speed-up of approximately 200 to 300 times.
Axial Ventilation and Blade Row Effects on Transient Natural Convective Shutdown Cooling in a Gas Turbine
Authors: Fahy Daniel D. , Ireland Peter
Published: October 2022

As a large civil gas turbine is cooling following operation, natural convective flows cause components to cool asymmetrically — the bottom sector cools faster than the top sector. This can lead to a number of issues that have the potential to damage engine components and affect operability. The ability to predict and understand this transient cooling cycle of a gas turbine has proven to be extremely difficult, owing to the complex nature of natural convective flow physics and its dependency on a considerable number of design parameters.

An experimental and numerical investigation into the impact of axial ventilation (interaction between the annulus and the external air) and blade rows on the natural convective flow field in a large civil gas turbine high-pressure compressor has led to some key discoveries. Axial ventilation caused a 70% increase in the peak top-to-bottom temperature difference in the cooling cycle, when compared to the baseline sealed case. The combinations of four blade rows and axial ventilation caused a 130% increase in peak temperature difference over the baseline case. Numerical simulations illuminated that the root cause of this was the cold air drawn into the lower section of the annulus led to a relatively high heat flux, coupled with a blockage effect on the natural draft in the upper section of the annulus inhibiting the convective heat transfer from this section. There appears to be a relationship between the porosity of the annulus and the peak top-to-bottom temperature difference that was observed.

This study on the impact of two parameters on the shutdown cooling of a simplified gas turbine annulus has highlighted their importance and inter-dependency in defining the level of rotor bow that is observed. Therefore, it is imperative that these effects are included and sufficiently captured in order for a shutdown cooling prediction method to be accurate.
Development of a Transient Test Facility for Evaluating the Aerothermodynamic Performance of Gas Turbine Cascades
Authors: Bai Bo , Li Yuanyuan , Li Zhigang , Li Jun
Published: October 2022

The paper presents the detailed design and benchmarking measurements for a transient linear cascade test facility with a bypass line. The test facility includes an experiment measurements line, a linear test section cascade, a bypass line and an exhaust line, and the quasi-steady-state aerodynamic and transient thermodynamic measurements can be conducted in this test facility. The linear cascade holds up 6 equally spaced cascade profiles, forming 5 completed cascade passages, and the center passage is used for aerodynamic and thermodynamic experiment measurements. Up to 2.4 kg/s of air is continuously supplied by four compressors, thus the quasi-steady-state aerodynamic test can be conducted. For a transient thermodynamic test, the mainstream is heated by a 150 kW heater and discharged to the atmosphere through a bypass line. After reaching the steady state, the bypass flow can be turned to enter the test line within 1.5 s by a control system. A significant step change of mainstream temperature is achieved in this way. A wide range of geometries and flow conditions investigations can be performed in this test facility, due to the special design of the pitch adjustment section and rotatable platform. An optical access window installed on the turntable can provide instrumentation access for Infrared (IR) measurements, laser-based measurements and visualization measurements. The benchmarking measurements at various exit Mach number (Ma) and incidence angles (β), are used to verify the aerodynamic and thermodynamic measurements performance of this transient test facility. Results show that the desired aerodynamic behaviors and a significantly transient step change (less than 1 s) of mainstream temperature are observed during the benchmark test duration. The long-time quasi-steady-state aerodynamic and transient thermodynamic measurements can be reliably conducted in this transient test facility.
Aeroelastic Analysis of Large-Scale Wind Turbines With Biplane Rotors
Authors: Pichitkul Auraluck , Sankar Lakshmi
Published: October 2022

As modern wind turbines continuously grow in scale and capacity, rotor blade mass and cost have become major design drivers. For offshore windfarms where construction, maintenance, and service are particularly challenging, blade mass and cost concerns are even more critical. A biplane rotor design concept, proposed by Wirz et al. at the University of California Los Angeles, is explored in this study as a means of reducing blade mass and cost. The biplane design replaces the thick airfoil shapes commonly found in the root region of conventional rotors with two thinner airfoils arranged in a biplane configuration. In the present study, this biplane design concept is applied to a redesign of the NREL 5 MW rotor, representative of modern large-scale offshore wind turbines. It is observed that the performance of the proposed biplane configuration is comparable to the baseline NREL 5 MW design at rated wind speeds, with potential mass-savings. However, the structural analyses also indicate significant stress concentration at the junctions where the biplane configuration is connected to the monoplane regions. A more detailed structural design would be necessary to alleviate stress concentrations in these areas and improve the overall structural characteristics of the rotor.
Predicting NOx Emissions In Gas Turbines Using Finite Rate Approach
Authors: Patwardhan Saurabh , Nakod Pravin , Orsino Stefano , Yadav Rakesh , Xu Fang , Brandt Dustin
Published: October 2022

Emission standard agencies are coming up with more stringent regulations on Nitrogen Oxides (NOx), given their adverse effect on the environment. The aircraft engines operate at varying operating conditions and temperature-dependent emissions like NOx are significantly affected by varying conditions. Computational Fluid Dynamics (CFD) simulations are playing a key role in the design of gas turbine combustors and an accurate NOx model will be an important tool for the designers. The new stringent regulations will require new computational approaches over the traditional methods so that the NOx can be predicted accurately under a wide range of operating conditions.

Traditionally, the high temperature NOx is predicted using a three-step Zeldovich mechanism. However, it has been observed that the NO (Nitrogen oxide) mass fraction predicted by the Zeldovich mechanism is not accurate for low power conditions due to its predominantly high-temperature kinetics. A significant amount of NO2 (Nitrogen dioxide) is observed in the experimental data at lower temperatures. This requires the inclusion of NO2 chemistry in the NOx mechanism. With the increase in the available computational power, a detailed chemistry simulation is gaining attention, especially for pollutant prediction. In this work, we explore the finite rate (FR) chemistry approach for the prediction of total NOx (NO + NO2) in a gas turbine combustor designed for Aerospace applications. Two reduced mechanisms are investigated namely, the PERK mechanism with 31 species and the Hychem mechanism with 71 species. Simulations with both mechanisms show good comparison with the experimental data and predict the individual contribution of NO and NO2 reasonably well. Further, it is observed that the spray breakup model has a significant impact on the NOx prediction, and it is important to capture the fuel spray correctly to predict the right amount of NOx.
Impacts of Pin Fin Shape and Spacing on Heat Transfer and Pressure Losses
Authors: Corbett Thomas M. , Thole Karen A. , Bollapragada Sudhakar
Published: October 2022

Additive manufacturing (AM) provides designers with the freedom to implement many designs that previously would have been costly or difficult to traditionally manufacture. This experimental study leverages this freedom and evaluates several different pin shapes integrated into pin fin arrays of a variety of spacings. Test coupons were manufactured out of Hastelloy-X using direct metal laser sintering (DMLS) and manufacturer recommended process parameters. After manufacturing, internal surface roughness and as-built accuracy were quantified using Computed Tomography (CT) scans. Results indicated that pin fins were all moderately undersized, and that there was significant surface roughness on all interior surfaces. Experimental data indicated that diamond shaped pins were found to have the highest heat transfer of the tested shapes, but triangle shaped pins pointed into the flow incurred the smallest pressure drop. Modifications to the streamwise spacing of the pins had little impact on the friction factor, but did increase heat transfer with increasing pin density. Prior Nusselt number correlations found in literature underestimated heat transfer and pressure loss relative to what was measured resulting from the AM roughness. A new correlation was developed accounting for AM roughness on pin fin arrays.
Numerical Performance Study of Adsorption Based Hydrogen Storage System in Silica Aerogel
Authors: Riahi Adil , Algurab Sara , Otto Marcel , Fernandez Erik , Kapat Jayanta , Schmitt Joshua , Saxena Swati
Published: October 2022

The purpose of this paper is to investigate the thermodynamics of the adsorption/desorption processes of hydrogen on silica aerogel. Hydrogen is a promising alternative fuel for gas turbines as it is carbon free and an excellent energy storage medium. However, the storage of hydrogen itself presents some challenges when stored in liquid or gaseous states. Thus, storing hydrogen in its adsorbed state provides a potential pathway to large scale economic hydrogen storage. The adsorption process is based on weak Van Der Waals forces that make the adsorbate (hydrogen) stick to the adsorbent surface (Silica Aerogel). A 2D CFD model was elaborated to examine the temperature and pressure changes along the adsorption/desorption processes. A grid independence analysis was conducted on meshes ranging from 5000 to 100000 nodes resulted in a similarity of thermodynamic properties after 80000 nodes. The Dubinin-Astakhov (D-A) model was adopted to determine the change in the quantity adsorbed with changing Temperature and pressures. The D-A model declared promising results when implemented in various adsorption studies. The simulation revealed an exothermic and endothermic processes during the adsorption and desorption respectively. A change in temperature during the storage/ discharge of (ΔT = 95K) provides an estimate of the amount of heat to be removed or added during the adsorption and desorption processes. The choice of silica aerogel resides on its feature of being among the lightest materials existing on earth which makes our system suitable for hydrogen storage in transportation. Furthermore, it is largely available and affordable. The outcome of this research can be extrapolated to several gas/silica aerogel combinations’ comparisons. This will be the focus of the upcoming research studies. Additionally, small storage units could provide healthcare applications with breathing air or oxygen packs, diving, space, and aircraft life support would also benefit from this storage technology which endows the system with a portability trait.
Effect of Inlet Preswirl on the Film Cooling Characteristics of Turbine Vane Surface
Authors: Chen Xinnan , Li Zhigang , Li Jun , Xu Qingzong , Du Qiang
Published: October 2022

Conjugate heat transfer (CHT) analyses were conducted to validate the accuracy of numerical method in the prediction of aerodynamic and thermal performance of the film cooled C3X vane. The effect of inlet preswirl on the film cooling performance of the vane surface was investigated, while the Nu and the net heat flux reduction (NHFR) were also calculated to analyze the heat transfer characteristics. In particular, the effects of clocking positions and swirl orientations of the inlet preswirl with varied mass flow ratios of film coolant were studied individually. The results indicate that the inlet preswirl aligned to the vane leading edge (LE) would significantly enhance the heat transfer on the vane surface while the inlet preswirl aligned to the passage would weaken the heat transfer but lead to a nonuniform distribution of Nu. The inlet preswirl aligned to the LE would also seriously affect the flow structure of the showerhead film coolant and do deteriorate to the film cooling performance on the vane surface especially for the suction surface, in contrast, the inlet preswirl aligned to the passage would even improve the film cooling performance under some mass flow rates of film coolant. Moreover, the disadvantage of inlet preswirl to the downstream film cooling performance is almost negligible, while the inlet preswirl is even beneficial to the film coolant coverage under some mass flow rates of coolant in this paper, especially for the suction surface (SS) with a large mass flow rate and the pressure surface (PS) with a small mass flow rate.
Next Generation APS Porous TBC for Gas Turbine Combustors
Authors: Rudrapatna Nagaraja , Lutz Bradley , Kington Harry
Published: October 2022

Modern gas turbine combustors rely on thermal barrier coatings (TBC) in addition to sophisticated cooling strategies to survive high temperature environments. The need for lower emissions either driven by International Civil Aviation Organization (ICAO) regulations or by customers desire for green engines often necessitates increased air budget for improved mixing, thus resulting in less available cooling flow. Even with state-of-the-art cooling schemes to offset reduced cooling air allocation, combustors can benefit from better TBC performance to mitigate durability challenges. This paper showcases the next generation Air Plasma Spray (APS) porous TBC developed by Honeywell as well as discusses tests performed and results gathered to assess its suitability for combustor application. A configured test specimen was utilized to evaluate suitability of new coating system for combustor application. The configured specimen captures the material system, geometric features, manufacturing, and assembly process associated with combustor fabrication and thus provides a realistic environment for performance assessment. The configured specimen test results indicate the new APS porous TBC showed better performance than the standard 6–8% Yttria Stabilized Zirconia (YSZ) porous TBC. The new TBC with its lower conductivity at higher temperature, increased thickness capability, and superior stability at substantially higher temperature than 6–8% YSZ TBC enables hot section components to survive hotter engine cycles.
Numerical Modeling of Liquid Jet in Non-Uniform Crossflow Using Enhanced Madabhushi Model
Authors: Feiz Homayoon , Zhao Wei , Kubicki Dominik , Frackowiak Marcin , Kumar Vivek , Jadeja Harshrajsinh , Nakod Pravin , Shrivastava Sourabh , Nallamothu Sravan K. , Lambert Markus , Lee Jong Guen , Song Jinkwan
Published: October 2022

One of the most used spray configurations for gas turbines and power combustors is liquid jet in crossflow. The process of breakup of liquid jet is very complex and understanding this mechanism is of paramount importance in engine design. This has led to the commencement of several studies from leading research groups [1–6]. Several new modeling methods such as the Madabhushi breakup model or more detailed VOF and Level set methods have been used successfully to understand and describe these complex breakup processes. However, most of these studies have been restricted to liquid jet in uniform single stream crossflow. In reality, these jets could be subjected to several gaseous streams and the breakup mechanism may vary significantly. Recently there have been some studies to understand the effect of non-uniformities on the crossflow velocity distribution and the droplet diameter. In the current work, we attempt to extend the scope of the Madabhushi breakup model to jets subjected to non-uniform crossflow. Non-uniform crossflow is created by co-directional and parallel gas flow using several hollow tubes. Locally, the momentum flux ratio changes by a factor of 4 and uniformity ratio (the ratio of the velocities of the two gas streams) of 2. A modified version of the Madabhushi model as proposed by Lambert et. al is used here to simulate the jet breakup. Model tuning has been conducted using University of Cincinnati Research data specifically designed for this configuration in partnership with General Electric Company. For turbulence, realizable k-ε with scalable wall function is used. The droplets are tracked using Ansys Fluent Discrete Particle Model (DPM). A second modeling approach VOF-to-DPM is also used which uses VOF equation along with LES with Dynamic Kinetic Energy Subgrid-Scale Model. This model requires no fine tuning of parameters and is more accurate but comes with more computational expense.

Various simulations are performed with pure water, pure diesel and emulsified diesel and water with uniform and non-uniform cross flows inside a chamber at a pressure of 50psi. Overall, the trends due to difference in material properties of the two liquids especially on penetration and Sauter mean diameter are well captured. The droplet characteristics such as axial velocity, Sauter mean diameter and volumetric flux are compared with experimental measurements and shows reasonable agreement. Overall, the liquid penetration is within reasonable accuracy. Discrepancies were seen in the spatial variation of the spray quantities such as Sauter mean diameter, droplet axial velocity etc. The simulation revealed a more averaged field whereas in experiments some layering was observed with bigger droplets at the edge of the spray, away from the wall.
Powering Telecommunication Towers Using Vertical Axis Wind Turbines: A Feasibility Study in Saudi Arabia
Authors: Toor Zakria , Bahaidarah Haitham M. , Rehman Shafiqur
Published: October 2022

This paper presents a road map to select and integrate an existing off-the-shelf Vertical Axis Wind Turbine (VAWT) for telecommunication towers. A comprehensive feasibility analysis is performed based on technical, economic, and greenhouse gas (GHG) emission reduction factors. More than 80% of these towers have a maximum power requirement of less than 3.5 kW. Hence, the study is conducted for wind turbines with 10 kW rated power. Four commercially available VAWTs are selected and analyzed at two locations within Dhahran using hourly wind data recorded between 2019 and 2020. The study found that the best wind turbine has a capacity factor of 18.7% and 19.1% for these sites at 10 m hub height, and the capacity factor increases to 21.6% and 22.3% at 50 m hub height. Similarly, the specific yield of the turbine also increases from 137 to 263 kWh/m2 as the hub height is increased from 10 m to 50 m. Economic analysis revealed that the best wind turbine results in 15,043 kWh of energy exported to the tower leading to 7.2 years’ payback period. Emissions analysis for the best case reduces the GHG emissions by 83%, which amounts to 23.3 tons of CO2.
Heat Transfer Enhancement of Swirl Cooling by Different Crossflow Diverters
Authors: Xiao Kun , He Juan , Feng Zhenping
Published: October 2022

Swirl cooling is a promising cooling technology in gas turbine blade leading-edge. However, the swirl strength of coolant decreases rapidly along the swirl chamber, and there exists a low heat transfer zone between two adjacent nozzles. Moreover, the downstream heat transfer is always reduced by the crossflow. To solve this problem, the concept of swirl cooling with crossflow diverter was proposed, and the velocity fields and heat transfer performance were investigated in this paper. Numerical simulations were performed by using 3D steady flow solver of Reynolds-averaged Navier-Stokes equations (RANS). The turbulence model validations were performed against both smooth swirl chamber and circular tube with circumferential ribs, and the validation results pointed out that the SST k-ω turbulence model had the highest accuracy in predicting the heat transfer in swirl chamber with diverters. To reveal the mechanism of crossflow suppression and heat transfer enhancement, the simulation results were compared with smooth swirl chamber under different Reynolds numbers. On this basis, the effects of crossflow diverter heights and locations were studied further. The results showed that for smooth swirl chamber, the swirl strength decayed linearly, and the heat transfer coefficients decreased rapidly, thus the high heat transfer zone cannot cover the whole region between these two adjacent nozzles. The circumferential velocity of the jet gradually decreased while the axial velocity increased, and the crossflow formed. Crossflow and downstream nozzle efflux produced interference effect. Because of friction effect, crossflow reduced the circumferential velocity of the downstream jets and made the jet deflect downstream. Thus, the high heat transfer area of the downstream target plane decreased sharply. For swirl chamber with crossflow diverters, the crossflow and downstream jets separated from each other. The ability of the downstream jet to penetrate the mainstream and scour the target surface was strengthened. Therefore, the heat transfer of the target surface near the downstream nozzle was enhanced. Higher Reynolds number contributed to a more obvious crossflow suppression and heat transfer enhancement effect.
Influence of the Contact Interfaces on the Dynamics and Power Flow Behavior of the Bolted Structure
Authors: Wang Yongfeng , Ma Yanhong , Hong Jie , Battiato Giuseppe , Firrone Christian Maria
Published: October 2022

Bolted joints are widely used for the assembly of mechanical components to provide continuity of the structure and transfer internal actions (i.e. forces and moments) from one member to another. Contact and dry friction at the jointed interface have a great influence on the dynamical performance of the assembly, especially for light-weight and heavy-loaded structures, such as the aero-engine.

In this paper, the nonlinear dynamic response of a turbo-engine casing in the presence of bolted flanges is studied, using one reduced order model of an elementary casing sector with means of node-to-node contact elements. while the vibration power flow method for the structural system with frictional interfaces is proposed, to reveal effects of energy dissipation at contact interfaces. It concluded that, the resonance frequencies and vibration responses of the bolted structures are influenced by the interfacial contact state, and the damping induced at the slipping contact area surrounding the bolt decreased the vibration response. Power flow through the bolted structure are visualized, which clarified the energy dissipation at the bolted interfaces.
Analysis of Melting and Solidification Behavior in DED Laser Welding of Inconel 901
Authors: Ali Ehtesham , Kwon Hwabhin , Lee Je-Hyun , Park Heesung
Published: October 2022

In this study, a transient simulation of laser welding is carried out using Directed energy deposition (DED) method for the 4mm thick Inconel 901 plate. Experimental and numerical simulation method are used to investigate the thermal behavior and solidification characteristics. Five different cases are investigated using COMSOL Multiphysics® software. The parameters used in this study are the laser power ranging from 550 W to 750 W and the laser scanning speed ranging from 6.67 to 10.0 mm/s. The cooling time between the melting and solidification process is evaluated in the region under the top surface of substrate for different laser power and laser scanning speed. Among the cases studied, D5 shows the highest temperature variation under top the surface of the substrate, followed by D2, D3, D4, and D1 has the lowest temperature due to lower laser power. The temperature variation under the top surface of substrate is also calculated for different conditions of laser assisted DED processes. The numerical simulation results are compared with the experimental results which are in good agreement and well validated. The obtained conclusions in this paper demonstrated that this numerical study of thermal behavior could provide a better understanding of the melting and solidification process inside the molten pool using laser assisted DED processes.
A Mechanistic Model for the Predictive Maintenance of Heavy-Duty Centrifugal Fans Operating With Dust-Laden Flows
Authors: Vulpio Alessandro , Oliani Stefano , Suman Alessio , Zanini Nicola , Saccenti Paolo
Published: October 2022

Heavy-duty centrifugal fans are employed for the transport of dust-laden flows in industrial plants, for cement or steel production, or in energy production plants and mine ventilation systems. These applications require the disposal of huge amounts of suspended particles which can lead to a gradual erosion of the machine parts where impacts take place. The wear of the fan components can lead to premature failure of the machine, threatening human safety and reliability of the whole plant. The assessment of the wear severity of the machine, according to the process parameters, can aid the plant owner in scheduling overhaul operations along with the operative life of the machine. Moreover, through a reliable estimation of the wear severity, fan manufacturers can optimize the whole machine design process, from the material selection to the warranty time assessment. The present work aims to develop a semi-empirical method capable of estimating the erosion severity of centrifugal fans employed for heavy-duty operations. A mechanistic model which accounts for the erosion on the blade leading edge is proposed. The model is derived by means of an analytical approach and accounts for a number of operating parameters (i.e., fan geometry, fan operating point, particle concentration in the flow, fluid properties, and material erosion resistance). A comparison of the theoretical model to the CFD results obtained through the use of multi-phase particle tracking is also provided to assess the reliability of the present method.