bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of an Oil Film Journal Bearing for Temperature Reduction
Authors: Chatterton Steven , Pennacchi Paolo , Vania Andrea , Dang Phuoc Vinh 
Published: September 2021

Abstract
Rotating machines are generally equipped with tilting-pad journal bearings. In general, during the design phase, the aspects that are most taken into account are the dynamic performances in terms of stiffness and damping and the minimum thickness of the oil film to avoid mixed lubrication conditions that can lead to white metal wear phenomena. The thermal aspect, on the other hand, is often underestimated and can be critical for machines operating at high speed and high load. Thermal heating is caused by shear stresses in the lubricating film. In general, an increase in lubricant temperature corresponds to a reduction in oil viscosity followed by a reduction in lubricant film thickness. This has a beneficial effect on bearing stiffness. On the contrary, a high temperature in the oil film is detrimental to the mechanical characteristics of the white metal which is characterized by a low melting temperature and subject to thermal creep phenomena.
The article analyzes, by means of numerical simulations, the influence of the bearing geometry on the thermal behavior of the bearing. The bearing geometry will then be optimized to reduce the maximum temperature in the bearing.
Off-Design of a Pumped Thermal Energy Storage Based on Closed Brayton Cycles
Authors: Frate Guido Francesco , Paternostro Luigia , Ferrari Lorenzo , Desideri Umberto 
Published: September 2021

Abstract
The growth of renewable energy source requires reliable, durable and cheap storage technologies. In this field, the Pumped Thermal Energy Storage (PTES), is drawing some interest as it appears not to be affected by geographical limitations and use very cheap materials. PTES is less efficient than pumped hydro and batteries, but it could achieve satisfactory efficiencies, show better economic performance and be characterized by negligible environmental impacts. A PTES stores the electric energy as thermal exergy in solid packed beds, by operating two closed Brayton cycles, one for charging and the other one for discharging. Although PTES thermodynamical behavior is well understood, the interaction between the components is rarely investigated. This study investigates the impact of packed-bed behavior on turbomachines operating conditions. In this way, PTES off-design and part-load performance are estimated. A control strategy especially suited for closed Brayton cycles, i.e. the inventory control, is used to control the system. As it resulted, PTES is characterized by an excellent part-load performance, which might be a significant advantage over the competing technologies. However, the off-design operation induced by the packed-bed thermal behavior might significantly reduce the system performance and, in particular, that of the discharge phase.
Proper Orthogonal Decomposition Analysis and Braking Control on Hydrodynamic Retarders by Bionic Iris Effective Diameter Regulation
Authors: Chen Xiuqi , Wei Wei , Liu Tangzhu , Xie Wenhao , Li Yifei , Zhuo Wang , Ruolin Wang , Yan Qindong 
Published: September 2021

Abstract
AIris, a flat circular membrane in the middle layer of human eyeball, is controlled by sympathetic nerve and can automatically adjust pupil size according to light intensity to limit the amount of light entering the eyeball. This paper attempts to introduce the artificial iris diameter changing mechanism into hydrodynamic machinery, that is, to control the hydrodynamic retarder without filling fluid by changing the inner diameter of iris and changing the flow path of retarder. Through the decomposition and reconstruction of the intrinsic flow field, the flow field characteristics of the iris retarder are deeply understood, and the fast prediction of the braking torque is realized. At the same time, the close-loop controller is designed to control the iris opening that realizing the adaptive adjustment of the output torque of the retarder, thus overcoming the difficulty on-line observation of actual filling rate of oil problem and the inaccurate tracking of braking torque on traditional hydrodynamic retarder with filling rate control. Our work prove that the nonlinear controller can achieve fast and accurate torque closed-loop torque control in various braking conditions compared with the hydrodynamic rate control retarder, and the potential of iris mechanism for adaptive control of hydrodynamic retarder is verified.
Control Strategy Development for Optimized Operational Flexibility From Humidified Micro Gas Turbine: Saturation Tower Performance Assessment
Authors: De Paepe Ward , Pappa Alessio , Coppitters Diederik , Montero Carrero Marina , Tsirikoglou Panagiotis , Contino Francesco 
Published: September 2021

Abstract
Waste heat recovery through cycle humidification is considered as an effective tool to increase the operational flexibility of micro Gas Turbines (mGTs) in cogeneration in a Decentralized Energy System (DES) context. Indeed, during periods with low heat demand, the excess thermal power can be reintroduced in the cycle under the form of heated water/steam, leading to improved electrical performance. The micro Humid Air Turbine (mHAT) has been proven to be the most effective route for cycle humidification; however, so far, all research efforts focused on optimizing the mHAT performance at nominal electrical load, and no thermal load. Nevertheless, in a DES context, the thermal and electrical load of the mGT needs to be changed depending on the demand, requiring both optimal nominal and part load performances. To address this need, in this paper, we present the first step towards the development of a control strategy for a Turbec T100 mGT-mHAT test rig. First, using experimental data, the global performance, depending on the operating point as well as the humidity level, has been assessed. Second, the performance of the saturation tower, i.e. the degree of saturation (relative humidity) of the working fluid leaving this saturator, is analyzed to assess the optimal water injection system control parameter settings. Results show that optimal mHAT performance can only be obtained when the working fluid leaving the saturation tower is fully saturated, but does not contain a remaining liquid fraction. Under these conditions, a maximal amount of waste heat is transferred from the water to the mGT working fluid in the saturation tower. From these data, some general observations can be made to optimize the performance; being maximizing injection pressure and aiming for a water flow rate of ≈5 m3/h. However, having a specific control matrix, that allows setting the saturation tower control parameters for any set of operational setpoint and the inlet conditions would be of more interest. Therefore, future work involves the development of a control matrix, using advanced data post-processing for noise reduction and accuracy improvement, as well as an experimental validation of this methodology on the actual test rig.
Gaussian Stochastic Process Modeling of Blend Repaired Airfoil Modal Response Using Reduced Basis Mode Shape Approach
Authors: Brown Jeffrey M. , Kaszynski Alex A. , Gillaugh Daniel L. , Carper Emily B. , Beck Joseph A. 
Published: September 2021

Abstract
A machine learning (ML) approach is developed to predict the effect of blend repairs on airfoil frequency, modal assurance criterion (MAC), and modal displacement vectors. The method is demonstrated on a transonic research rig compressor rotor airfoil. A parametric definition of blend geometry is developed and shown to be capable of encompassing a large range of blend geometry. This blend repair geometry is used to modify the airfoil surface definition and a mesh morphing process transforms the nominal finite element model (FEM) to the repaired configuration. A multi-level full factorial sampling of the blend repair design space provides training data to a Guassian stochastic process (GSP) regressor. The frequency and MAC results create a vector of training data for GSP calibration, but the airfoil mode shapes require further mathematical manipulation to avoid creating GSP models for each nodal displacement. This paper develops a method to significantly reduce blended airfoil mode shape emulation cost by transforming the mode shape training data into a reduced basis space using principal component analysis (PCA). The coefficients of this reduced basis are used to train a GSP that can then predict the values for new blended airfoils. The emulated coefficients are used with the reduced basis vectors in a reconstruction of blended airfoil mode shape. Validation data is computed at a full-factorial design that maximizes the distance from training points. It is found that large variations in modal properties from large blend repairs can be accurately emulated with a reasonable number of training points. The reduced basis approach of mode shape variation is shown to more accurately predict MAC variation when compared to direct MAC emulation. The added benefit of having the full modal displacement field also allows determination of other influences such as tip-timing limits and modal force values.
Investigation on the Effects of Field Emission Plasma on the Performance of a Micro-Combustor
Authors: De Giorgi Maria Grazia , Cinieri Giacomo , Fontanarosa Donato , Ficarella Antonio 
Published: September 2021

Abstract
This work provides a numerical investigation of the effects of micro field emission dielectric barrier discharge (FE-DBD) plasma actuation on the performance of a micro-combustion system composed of two straights perpendicular microchannels for propellant injection followed by a rectangular micro-combustion chamber in a T-shaped planar configuration.
Concerning the modeling, a novel two-step approach has been developed. The first step consisted in solving the chemistry of a sinusoidal plasma discharge in a zero-dimensional modeling. To this purpose, the collisional processes involved in the plasma discharge have been solved using a Boltzmann-equation approach, which permits to predict the electron impact reactions based on a two-temperature model. Furthermore, the zero-dimensional hypothesis used for computations assumed uniform plasma during the overall discharge duration. Concerning the plasma chemistry, excitation and de-excitation processes, electron-ion recombination reactions, attachment and detachment for electrons and neutral species have been considered in order to improve the prediction accuracy.
This step allowed to quantify the body force, the heat source and the propellant composition modification induced by sinusoidal plasma actuation operating at 10 MHz of repetition rate, atmospheric pressure and 300 K temperature. Therefore, the predicted cycle averaged plasma effects have been used in 2D steady-state simulations of the laminar, compressible, reactive micro flow, based on a continuum Navier-Stokes approach. SIMPLE pressure-velocity coupling scheme was chosen with a second order pressure spatial discretization. A second-order upwind scheme was applied. The hydrogen-oxygen combustion has been modeled using the Connaire mechanism. The comparison between the results of the reference case without plasma actuation, and those retrieved in presence of plasma actuation at different supplied voltages, highlighted the performance enhancement due to plasma discharge.
Compressor Map Corrections for Highly Non-Linear Fluid Properties
Authors: Anderson Mark 
Published: September 2021

Abstract
Turbomachinery systems are often subject to variations in ambient conditions and applied loads in operation. Standard maps (perhaps the most common being pressure ratio verses mass flow for compressors) are usually presented in terms of fixed inflow conditions. To account for changes in performance due to varying inlet conditions, compressors maps are often presented in standardized form where the mass flow and rotational speeds are normalized as a function of the reference condition total pressure and temperature. These methods are very widely used, particularly in the turbo charger industry. With these normalized maps, the actual performance of a compressor in a given environment can be deduced simply and easily with very reasonable accuracy in most cases.
The underlaying assumption of this conventional normalization process is that the fluid behaves as a perfect gas. While this is usually sufficient for air compressors, the method is not viable where the fluid properties are not near perfect gas conditions, which is certainly the case for supercritical applications. The highly variable fluid properties near the critical point, and the challenges they present in design, have been well documented in the literature. The two most critical properties to consider in the design process are the density and the speed of sound. The density determines the volumetric flow for a given mass flow and this in turn determines the incidence angle, a primary driver of performance. The speed of sound directly affects the range of the compressor via choking. Choking range can be further complicated by the fact that under certain conditions, the choked state can be reached at Mach numbers less than one. While rare, this situation can occur when the inflow conditions are found close to the liquid side of the saturation dome.
To account for these effects, a new method is proposed to generate normalized maps of performance that can be used to determine actual performance of a wide range of inlet conditions for highly non-linear thermodynamic properties. Although not as simple as the conventional perfect gas method that can be applied in a “back-of-the-envelope” style, the new method can be applied very rapidly using a spreadsheet-based method directly calling high fidelity NIST thermodynamic models. The end result of this tool is that a compressor map that has been painstakingly generated with testing or CFD can be applied to any inlet condition and the range and performance predicted very rapidly with high accuracy.
Design of 1 MW Direct-Fired Combustor for an sCO2 Power Cycle
Authors: Delimont Jacob , White Steve , Andrews Nathan 
Published: September 2021

Abstract
Direct-fired super-critical carbon dioxide (sCO2) power cycles, are a potential method for efficiently capturing nearly all of the CO2 emissions from burning fossil fuels. Direct-fired sCO2 cycles require a very high degree of recuperation, which in turn means that the inlet temperature to the combustor is significantly higher than would typically be seen in a similar gas turbine combustors. Previous efforts have shown that combustor inlet temperatures of around 700 °C are to be expected for a cycle with around 1200 °C combustor exit temperatures [1]. This high inlet temperature means that bypass gasses are extremely hot, which poses some difficulties for the design of the combustion system, especially thermal management of the combustor liner and injectors in the 200 bar sCO2 environment.
The project team led by Southwest Research Institute (SwRI) is in the process of building a 1 MW scale direct-fired combustor. This paper will detail some of the design challenges and obstacles associated with designing a direct-fired sCO2 combustor. These obstacles include thermal management of fuel and oxygen streams, oxygen safety, and combustor cooling. This paper will focus on many of the design questions necessary for the design of a direct-fired sCO2 combustor. This work presents computational modeling details of the actual 1 MW geometry currently being built.
Use of an Integrated Approach for Analysis and Design of Turbocharged Internal Combustion Engine
Authors: Ebel Thiago , Anderson Mark , Pandya Parth , Perchanok Mat , Tiney Nick , Gravante Steve P. 
Published: September 2021

Abstract
When developing a turbocharged internal combustion engine, the choice of turbocharger is usually based on designer experience and existing hardware. However, proper turbocharger design relies on matching the compressor and turbine performance to the engine requirements so that parameters such as boost and back pressure, compressor pressure ratio, and turbine inlet temperatures meet the needs of the engine without exceeding its allowable operating envelope. Therefore, the ultimate measure of a successful turbocharger design is how well it is matched to an engine across various operating conditions. This, in turn, determines whether a new turbocharger is required, or an existing solution can be used.
When existing turbocharger solutions are not viable, the engine designer is at a loss on how to define a new turbocharger that meets the desired performance requirements. A common approach in industry has been to scale the performance of an existing turbocharger (compressor and turbine maps) and take these requirements for Original Equipment Manufacturers to possibly match it with a real machine. However, the assumptions made in a basic scaling process are quite simplistic and generally not satisfactory in this situation. A better approach would be to use a validated meanline model for a compressor and turbine instead, allowing to perform an actual preliminary design of such components. Such approach allows to link the engine performance requirements in a very early stage of te component design project and it guides the designer for the design decisions, such as rotor size, variable geometry nozzles, diameter, or shroud trims and others. Therefore, a feasible solution is more likely with design less iterations.
This paper describes a methodology for an integrated approach to design and analyze a turbocharged internal combustion engine using commercially available state-of-the-art 1D gas dynamics simulation tool linked to two powerful turbomachinery meanline programs. The outputs of this analysis are detailed performance data of the engine and turbocharger at different engine operating conditions.
Two case studies are then presented for a 10-liter diesel truck engine. The first study demonstrates how the programs are used to evaluate an existing engine and reverse engineer an existing turbocharger based only on the available performance maps. Then a second study is done using a similar approach but redesigning a new turbocharger (based on the reverse engineered one) for an increased torque output of the same engine.
Oxy-Fuel Combustor Injector
Authors: Etemad Shahrokh , Baird Benjamin D. , Alavandi Sandeep 
Published: September 2021

Abstract
Oxygen-fuel-diluent mixing is important for oxy-combustion as it impacts emissions, efficiency (oxygen slippage) and pattern factor. In this work, rapid mixing validation testing was conducted. Combustion testing was performed with natural gas and syngas from atmospheric pressure (1 atm.) to high pressure (10 atm.) to demonstrate stable operation. Oxy-natural gas testing demonstrated stable operation and low CO emissions over a wide range of test conditions. Syngas testing showed low CO emissions and a wider operability range with high dilution/low oxygen levels. Complete oxygen burnout was accomplished, indicating no oxygen slippage occurred at stoichiometric conditions and hence improved cycle efficiency.
Improving Fuel Efficiency Using Various Configurations of a Hydrogen Ejector in a Fuel Cell
Authors: Yun Seok-Beom , Kim Youn-Jea 
Published: September 2021

Abstract
Renewable energy such as hydrogen or solar energy is promising due to issues surrounding environmental pollution. In particular, hydrogen only produces water and generates electric energy in a fuel cell when reacting electrochemically with air. A fuel cell consists of many parts such as a cell stack, an ejector, a hydrogen tank, and a regulator, and so on. In this study, the ejector, a device that supplies hydrogen to proton exchange membrane fuel cell (PEMFC), is studied. The ejector recirculates unreacted hydrogen in proton exchange membrane fuel cells by the Venturi effect. Since the ejector is related to energy efficiency, many researchers have conducted research to improve the performance of the ejector. Therefore, it is most desirable that hydrogen recirculation in the ejector is increased. The present research investigates how the configuration of the ejector affects the hydrogen recirculation. A concave configuration of the ejector is considered. This concave having a helical pattern is dependent on a pitch ratio and the number of grooves. The results are compared with numerical analysis data from existing publications using computational fluid dynamics (CFD). The influence of the configuration was analyzed by performing numerical simulations with three-dimensional grid systems. A poly-hex-core mesh type was applied to reduce errors caused by convection and diffusion in the computational domain. Considering the configurations of the ejector, turbulence dissipation rate, static pressure, and tangential velocity inflow were analyzed graphically. Consequently, it was determined that the model displays a 7% increase in recirculation ratio over the reference model.
Multi-Physics Topology Optimization for Thermal-Flow Problems Applied to Additively Manufactured Heat Exchangers
Authors: Tang Tsz Ling Elaine , Xia Songtao , Rop Peter , de Wispelaere Steven , Subramanian Ramesh , Koos Bernd 
Published: September 2021

Abstract
Heat exchangers are often subjected to increasing demands on their efficiency with a reduced volumetric footprint. With the advancement in additive manufacturing technologies, topology optimization can be a viable strategy to derive novel designs to improve product performance. Topology optimization has been vastly investigated in the past few decades for structural designs. In this presentation, a thermo-flow topology optimization workflow was developed for heat exchanger applications which performs a multi-physics analysis (e.g. with coupled flow dynamics and heat transfer). In the thermo-flow topology optimization workflow, thermo-flow solver in STAR-CCM+ was utilized to evaluate thermal and flow performance metrics. Adjoint sensitivity was computed with the adjoint solver based on a defined objective function. The adjoint sensitivity was then used as an input to a method of moving asymptotes (MMA) optimizer to identify new designs. This integrated workflow is demonstrated through the design optimization for application to heat exchangers with single phase fluids in a dual flow arrangement. The multi-physics topology optimization enables objectives of different physics to be evaluated in a single optimization run. The major complicating factor compared to earlier optimization work on the gas turbine components, is the dual flow character of the problem that requires optimization on both sides of the heat exchanger. Future efforts on several individual flows involved in the heat exchange problem, as well as single phase versus two-phase flow phenomena will be discussed.