bluuebunny/crossref_metadata_2025_split huggingface dataset:
Feasibility of Innovative Solar-Thermo-Acoustic Power Conversion Cycles
Authors: Behar Omar , Saxena Saumitra , Roberts William L. 
Published: January 2021

Abstract
The techno-economic assessment of the concentrating solar power thermo-acoustic power conversion systems is carried out to identify the optimum conditions, under-which the solar thermo-acoustic might be competitive to the current commercial solar thermal power technologies.
The thermal and economic performance of a thermo-acoustic engine integrated to five different solar collectors including Compound Parabolic Collector, Linear Fresnel, Parabolic Trough, Central receiver, and Solar Dish is compared to the current commercial solar thermal power technologies as well as to their corresponding Carnot-cycle. To do so, a modular modeling approach is used to consider all the available commercial technologies, through combining a modular energy model with a simplified economic model.
Jeddah city (Saudi Arabia) has been chosen as a reference site for the present study. The results indicate that the integration of compound and dish solar collectors to a thermo-acoustic engine might offer competitive solutions. Compound collectors might be more suitable for integration with the thermo-acoustic engine than linear Fresnel collectors, if the exergy efficiency of the engine reaches 40%. Besides, dish-thermo-acoustic system becomes more competitive than current dish-mechanical Stirling engine, if the investment costs of the thermo-acoustic engine are reduced to 3500 $/kWe, but the operating temperature should be above 700°C. Improving the exergy efficiency of the thermos-acoustic engines, from 35% to 40%, could make the dish-thermo-acoustic system more competitive than current dish-mechanical Stirling engines at a working temperature of 500°C.
The study concludes that more efforts must be focused on reducing the costs of the TA devices rather than on improving efficiency.
A Toolbox of Hardware and Digital Solutions for Increased Flexibility
Authors: Demougeot Nicolas , Steinbrenner Alexander , Cires Alfredo , Paskin Marc 
Published: January 2021

Abstract
The power generation market has been changing rapidly with the injection of an ever increasing usage of renewable power sources. The cyclic and highly unpredictable nature of power generation output from renewable sources is forcing Gas Turbine (GT) operators to significantly increase the operational flexibility of their engines.
While the industry has been, for many years, developing and fielding solutions providing increased output at the high end of the operating range, the focus has shifted recently to solutions allowing for a safe decrease of the engines’ minimum operating load.
The AutoTune (AT) system was introduced at last year’s Turbo Expo conference [5], and the challenges of developing a safe Extended Turndown add-on are detailed herein. Other digital and hardware solutions presented include Part Load Performance, decreased start-up time for both simple and combined cycle units, disc cavity cooling modulation and Exhaust Bleed. Increased ramp rate is addressed with the associated significant difficulty of maintaining the mechanical integrity of the rotors and casings.
PSM has been working on a toolbox of both hardware and digital solutions to increase on GT operability both on the high and low ends of the load range and the technical issues faced are described in this paper.
Intelligent Fault Diagnosis of Planetary Wheel Bearing Using Constrained Independent Component Analysis and Stacked Sparse Autoencoder
Authors: Li Hongkun , Huang Gangjin , Ou Jiayu , Zhang Yuanliang 
Published: January 2021

Abstract
Industrial machinery is developing in the direction of large-scale, automation, and high precision, which brings novel troubles to mechanical equipment management and maintenance. Intelligent diagnosis of mechanical running state based on vibration signals is becoming increasingly important, and it is still a great challenge at pattern recognition. As one of the indispensable components in mechanical equipment, planetary gearboxes are widely used in wind power, aerospace, and heavy industry. However, the problem of automatically maximizing the accuracy of planetary gearbox under different working conditions has not been solved. Therefore, an intelligent diagnosis method for planetary wheel bearing based on constrained independent component analysis (CICA) and stacked sparse autoencoder (SSAE) is presented in this research. Firstly, the fault signal with obvious time-domain characteristics is extracted by constrained independent component analysis (CICA), and the fault signals and noise is separated. Then, calculating the correlation kurtosis value of the time domain signals at different iteration periods as the eigenvalue to obtain the training samples and the test samples. The parameters of the network layer, the number of hidden nodes and learning rate are determined to build the model of SSAE. In the end, the training samples are input into the model for training and the whole network is fine-tuned. The advantages and disadvantages of the model are verified by the test samples. The intelligent classification and diagnosis of the mechanical running state are completed. Experiments analysis with real datasets of planetary wheel bearing show that the proposed method can achieve higher accuracy and robustness for fault classification compared with other data-driven methods. The application of this method in other major machinery industry also has bright prospects.
Machine Learnt Synthetic Turbulence for LES Inflow Conditions
Authors: Corsini Alessandro , Delibra Giovanni , Giovannelli Marco , Traldi Stefania 
Published: January 2021

Abstract
LES computations have limited applications in turbomachinery predictions because of the formidable amount of resources they require. Due to the exponential increase of requirements with Reynolds number, LES is usually limited to elements with moderate flow velocities and to investigate flows characterized by multiple length and time scales that overlaps. It is the case of combustion, aeroacoustics, unstable range of operations such as stalled conditions.
In all these cases LES can provide unique insights on thermo-fluid-dynamics. The main drawback is that LES is not only very expensive, but also extremely sensitive to inflow conditions. A number of studies pointed out that slight differences in LES inflow conditions can result in a very different flow development and therefore different prediction of performance, noise and so on. It is so sensitive that comparison of computations with different inflow conditions and same arrangement for other parameters result in completely diverging results.
There are two major solutions to this problem. First, is to use a cyclic inflow channel to generate a fully turbulent profile to feed to the main simulation. Second, the use of a synthetic turbulence model to generate analytically an unsteady turbulent profile. The drawback of the first approach is the fact that a fully developed inflow can be un-realistic for most turbomachinery applications. On the other hand, the second approach was proved not to be able to correctly reproduce the statistics of turbulence and therefore the synthetic inflows do not provide a real solution to the problem. In this paper we discuss a novel method to generate LES inflow conditions, based on adversarial machine learning. In particular we trained a generative adversarial network (GAN) to reproduce the inflow conditions of a channel flow. In this way, the generator of the GAN is trained to correctly reproduce an unsteady turbulent profile, while the discriminator is used during the training phase as an adversarial agent for the generator. During the validation of the method both the discriminator and the generator will be used to validate the proposed methodology.
Using Feature-Based Mesh Adaptation to Improve the Adjoint Optimisation of Transonic Compressor Blades
Authors: John Alistair , Vivarelli Guglielmo , Qin Ning , Shahpar Shahrokh 
Published: January 2021

Abstract
The benefit of mesh adaptation to improve the optimisation process of turbomachinery components is here demonstrated for the first time. Mesh movement is used to automatically cluster and align the cells with significant flow features such as shocks, shock-induced separation and wakes for every geometry tested during a transonic compressor blade optimisation. Using mesh movement means that the same size grid is used while significantly improving the accuracy of the simulation and resulting adjoint gradients. A method is demonstrated to automatically carry out feature based mesh movement during every step of an adjoint optimisation process. Optimisations are carried out using the adaptation method and also using the starting mesh as a comparison. It is shown that (when tested on a very fine grid) the adaptation-optimisation process results in a better design, due to more accurate flow and gradient prediction throughout the optimisation process. A cost breakdown of the process is given to show that using adaptation during the optimisation process only increases the overall optimisation cost by a small amount, but results in greater efficiency of the final blade design.
A Machine-Learnt Wall Function for Rotating Diffusers
Authors: Tieghi Lorenzo , Corsini Alessandro , Delibra Giovanni , Tucci Francesco Aldo 
Published: January 2021

Abstract
Data-driven tools and techniques have proved their effectiveness in many engineering applications. Machine-learning has gradually become a paradigm to explore innovative designs in turbomachinery. However, industrial Computational Fluid Dynamics (CFD) experts are still reluctant to embed similar approaches in standard practice and very few solutions have been proposed so far. The aim of the work is to prove that standard wall treatments can obtain serious benefits from machine-learning modelling.
Turbomachinery flow modeling lives in a constant compromise between accuracy and the computational costs of numerical simulations. One of the key factors of process is defining a proper wall treatment. Many works point out how insufficient resolutions of boundary layers may lead to incorrect predictions of turbomachinery performances. Wall functions are universally exploited to replicate the physics of boundary layers where grid resolution does not suffice. Widespread wall functions were derived by the observation of a few canonical flows, further expressed as a simple polynomial of Reynolds number and turbulent kinetic energy. Despite their popularity, these functions are frequently applied in flows where the ground assumptions cease to be true, such as rotating passages or swirled flows. In these flows, the mathematical formulations of wall functions do not account for the distortion on the boundary layer due to the combined action of centrifugal and Coriolis forces.
Here we will derive a wall function for rotating passages, through means of machine-learning. The algorithm is directly implemented in the N-S equations solver. Cross-validation results show that the machine-learnt wall treatment is able to effectively correct the turbulent kinetic energy field near the solid walls, without impairing the accuracy of the RANS turbulence model in any way.
Effect of Jets in Crossflow in Deposition Mitigation on Full 3D NGV With Endwall Features
Authors: Oliani Stefano , Casari Nicola , Pinelli Michele , Suman Alessio , Carnevale Mauro 
Published: January 2021

Abstract
Particle ingestion is a major concern for the operation of gas turbines. In the case of an aircraft, particle dispersed in the air ingested by the engine can threaten flight safety. Swallowed particles can erode or stick to aerodynamic surfaces. Both the occurrences translate in a reduction of performance due to variation in shape and in roughness of the aerodynamic surfaces. This work is devoted to the analysis of fouling, i.e. the deposition of particles over time. By observing that the deposition pattern is strongly influenced by the flow field in the nearby of the walls, the central idea of this work is to employ Active Flow Control (AFC) to mitigate fouling when emergency conditions are met by the aircraft. The proposed system will inject air bled from compressor discharge in front of the critical locations where fouling is supposed to occur. The present work aspires to lay the foundations for the development of such an AFC device, by focusing on the modified aerodynamics consequent to the introduction of the transverse jet. The potential of this device is evaluated quantitatively using CFD simulations. An energy-based sticking model, coupled with a mesh-morphing solver, is used to track the airfoil deposition thickness evolution in time. The work is two-fold: first, the dynamics of the interaction between flow structures and particle transport is addressed. Second, the attention is posed on correlating fouling pattern variation to the modified aerodynamics of the vane consequent to the introduction of the device. Three design concepts are investigated on the 3D test case geometry of an HPT NGV cascade. The counter-rotating vortex pair (CVP) is detected as the main responsible for jet-particle interaction. Finally, the jet impact on aerodynamic performance is also assessed.
A Simplified Model for Predicting Natural Draft Wet Cooling Tower Performance of Large Steam Power Plants
Authors: aus der Wiesche Stefan 
Published: January 2021

Abstract
Flexible plant operation and rapid load changes become major issues for steam turbine operation. In thermal power plants, the steam turbine performance is closely related to the condenser, and an accurate prediction of coolant temperature as function of changing weather conditions is necessary in order to optimize power plant fleet operation. In this contribution, a one-dimensional model for simulating the performance of large natural draft wet cooling towers is presented. The evaporation zone model rests on the evaporative cooling theory developed by Merkel and Poppe. The off-design behavior of the cooling tower, that is relevant to part load performance, is modeled by an empirical power-law approach. A user-friendly method is presented in order to identify required model parameters by means of already available power plant data. The simulation tool can be employed easily for existing power plants for which the original cooling tower design and construction data lost their validity. The outcome of the present calculation method is successfully compared with field data from representative cooling towers at Middle-European sites.
Design Optimization of a Multi-kW Thermoacoustic Electric Generator Using DeltaEC Model
Authors: Somu Srinath , Lacoste Deanna , Saxena Saumitra , Roberts William L. , Keolian Robert M. 
Published: January 2021

Abstract
Waste heat recovery from power plants and industries requires a new type of electricity generators and related technological developments. The current research work is aimed at the design of a multi-kilowatt thermoacoustic electric generator, which can be employed as the bottoming cycle of a gas-turbine power plant or for industrial waste heat recovery. The proposed device converts thermal energy into acoustic power and subsequently uses a piezoelectric alternator to convert acoustic power into electricity. The challenge in designing such a device is that it has to be acoustically balanced and the performance of the device is greatly affected by numerous parameters such as frequency of the traveling acoustic wave, heat exchanger parameters, regenerator dimensions, acoustic feedback loop, etc. The proposed device is a lab-scale demonstration targeted to produce a few kilowatts of electric power from a 20 kWth heat source. To achieve the acoustically balanced configuration of the device, DeltaEC software is used. The DeltaEC model outcomes are used to arrive at the optimized design of the device and its components. The analytical method, the optimized geometrical dimensions of thermoacoustic components and the minimum required conditions of heat source input are presented in this paper.
Digital Hybrid Evaporative Cooler: An Adaptive, Modulated Evaporative Cooler for Combined Cycle Power Plants With Improved Heat Rate and Water Expense
Authors: Sammak Majed , Jupudi Maruthi , Kippel Brad , Zia Jalal 
Published: January 2021

Abstract
This paper introduces a novel evaporative cooling system. The digital hybrid evaporative cooler works under a wide range of evaporative cooling effectiveness from 0% to 100%. It consists of several evaporative cooling media installed in a row with a fixed space in between. By operating the evaporative cooling system with varied numbers of evaporative cooling media in service, the evaporative cooling percentage can be changed from 0% to 100%. This digital hybrid evaporative cooler can thus be used to achieve a desired combined cycle power and heat rate as well as reduced water consumption.
The study was performed on GE heavy duty gas turbine. The selected combined cycle was 1-on-1 (one gas turbine, one heat recovery steam generator and one steam turbine train). The heat recovery steam generator was a 3-pressure level with reheat.
The study showed the evaporative cooling effectiveness impact on gas turbine parameters. The studied parameters were firing temperature, gas turbine exhaust temperature, exhaust energy, gas turbine power and heat rate.
Furthermore, the combined cycle heat rate improvement at different combined cycle loads and cooling effectiveness was analysed. The analysis was performed on combined cycle loads from 100% to 80% load with 5% interval. The selected evaporative cooling effectiveness at these loads were 90, 70, 50 and 30 percent respectively.
The combined cycle heat rate at 80%-part load and 30% evaporative cooling effectiveness was calculated at two ambient conditions in a selected site in the Middle East. At the ambient conditions of 43°C/30%RH, the combined cycle heat rate improvement was 0.56%. At the ambient conditions of 35°C/40%RH, the combined cycle heat rate improvement was 0.38%.
The digital evaporative cooler is also a mean of achieving water expense target. Reducing the evaporative cooling effectiveness from 90% to 30% would allow for an approximate of 60% saving in water consumption.
This digital hybrid evaporative cooler is connected to a control system which collects data from the gas turbine key parameters and depending on the requirements the system determines the number of evaporative cooling media in service.
Experimental Investigation of Surge Phenomena in a Transonic Centrifugal Compressor With Inlet Distortion
Authors: Ito Sasuga , Furukawa Masato , Gunjishima Satoshi , Ota Takafumi , Konishi Kazuhito , Yamada Kazutoyo 
Published: January 2021

Abstract
Inlet distortion has influence on the aerodynamic performance of turbomachinery such as compressors, turbines and fans. On turbochargers, bent pipes are installed around the compressor due to the spatial limitations in the engine room of the vehicle. As the result, the compressor is operated with the distorted inflow. In the low flow rate operation, the distorted inflow also affects the flow instability like stall and surge. Especially, the operation range on the low flow rate side is defined based on the flow rate where surge occurs, so it is important to investigate the effect of the distorted inflow on surge. In this study, the effect of the inlet distortion to surge phenomena has been investigated by the experiments with a transonic centrifugal compressor. A bent pipe has been installed at the upstream of the compressor to generate a distorted flow. Experiments have been also conducted under the condition that a straight pipe was installed upstream of the compressor, and unsteady measurements with high response pressure sensors and an I-type hot wire probe have been carried out to each experiments. In addition, Fast Fourier transform (FFT) and Wavelet transform have been applied to the unsteady measurement results obtained from each experiment.
Part 2: Design Optimisation Strategies for a Fuel Spray Nozzle
Authors: Andreou Thomas , White Craig , Kontis Konstantinos , Shahpar Shahrokh , Brown Nicholas 
Published: January 2021

Abstract
Reducing emissions and improving fuel economy has become a key target for advanced aircraft engine platforms. The competitive aviation market requires a drastic reduction in current aircraft emission levels, which leads to the requirement of optimising the entire combustion process. Lean burn pre-mixed systems are an efficient way of reducing NOx emissions. Starting from a datum blade generated in a companion paper, shape optimisation strategies applied to a fuel spray nozzle have been explored. Making use of three different design space parametrisation methods and several optimisation algorithms, an optimised passage has been generated. The optimised design achieves a considerable pressure loss reduction in comparison to the baseline design.
Ignition Probability and Lean Ignition Behaviour of a Swirled Premixed Bluff Body Stabilised Annular Combustor
Authors: Ciardiello Roberto , Pathania Rohit S. , Allison Patton M. , de Oliveira Pedro M. , Mastorakos Epaminondas 
Published: January 2021

Abstract
An experimental investigation was performed in a premixed annular combustor equipped with multiple swirl, bluff body burners to assess the ignition probability and to provide insights into the mechanisms of failure and of successful propagation. The experiments are done at conditions that are close to the lean blow-off limit (LBO) and hence the ignition is difficult and close to the limiting condition when ignition is not possible. Two configurations were employed, with 12 and 18 burners, the mixture velocity was varied between 10 and 30 m/s, and the equivalence ratio (ϕ) between 0.58 and 0.68. Ignition was initiated by a sequence of sparks (2 mm gap, 10 sparks of 10 ms each) and “ignition” is defined as successful ignition of the whole annular combustor. The mechanism of success and failure of the ignition process and the flame propagation patterns were investigated via high-speed imaging (10 kHz) of OH* chemiluminescence. The lean ignition limits were evaluated and compared to the lean blow-off limits, finding the 12-burner configuration is more stable than the 18-burner. It was found that failure is linked to the trapping of the initial flame kernel inside the inner recirculation zone (IRZ) of a single burner adjacent to the spark, followed by localised quenching on the bluff body probably due to heat losses. In contrast, for a successful ignition, it was necessary for the flame kernel to propagate to the adjacent burner or for a flame pocket to be convected downstream in the chamber to grow and start propagating upwards. Finally, the ignition probability (Pign) was obtained for different spark locations. It was found that sparking inside the recirculation zone resulted in Pign ∼ 0 for most conditions, while Pign increased moving the spark away from the bluff-body or placing it between two burners and peaked to Pign ∼ 1 when the spark was located downstream in the combustion chamber, where the velocities are lower and the turbulence less intense. The results provide information on the most favourable conditions for achieving ignition in a complex multi-burner geometry and could help the design and optimisation of realistic gas turbine combustors.