bluuebunny/crossref_metadata_2025 huggingface dataset:
Turning Vane FE Model Validation Using Ping Test
Authors: Satheesh Aparna , Santhana Gopalakrishnan Babu , Chippa Anil Kumar
Published: February 2024

Energy demand in world is ever increasing trend and new gas turbine portfolios is continuing to increase with improved performance, reliability, and efficiency. In new gas turbine development, designs are being developed by numerical, analytical methods with complex assessment and bench marked with previous experiences. As new development in progress, complex designs are being tried out to improve Gas turbine efficiency and performance and in that different variability arises with respect to boundary conditions and loading scenario for various operating conditions. It is important to validate the component behavior both in static behavior and dynamic behavior to predict the durability of that component. Typically, these assessments are being performed using FE analysis to validate the design analytically, but it is also important to match the FE results with past field experience or test data.

This paper discusses design validation of one such component which was introduced in flow path to turn the angle of the air flow in compressor exit. Component which considered for this study is named as Turning Vane which is part of compressor casing in gas turbine. As there is no experience in past available or field data exists to bench mark the design, FE analysis assumptions in boundary conditions are validated using ping test from component assembly. As the name suggests, turning vane is the statoric component which turns the flow to create smoother change in direction of air flow resulting in pressure loss reduction thereby increasing the efficiency of the burning of the fuel during combustion phase. This paper focuses on the pre-test preparation and post processing of test data to validate the model considered. Further, it also describes how the accuracy of FE model with respect to ping test results are arrived at using at using modal assurance criteria number.

FE model constraint and mode shapes are also discussed in this paper. Criteria for finalizing instrumentation location is also discussed in this paper. This paper also focuses on other parameters of test like Auto MAC index, reciprocity test and linearity test.
Gas Turbine Instrumented Exhaust System Structural Assessment
Authors: Sambandam Manoharan , Simoncini Marco , Michal Zielaskowski , Michonski Michal
Published: February 2024

There is a constant demand from the market for the new gas turbines or enhancement of an existing gas turbines. There are several aspects which triggers this market demand, like changing environmental regulations, market competition, energy efficiency, technological advancements, need for fuel flexibility, to name only few. Prototype tests are conducted to validate the design input parameters considered at the time of development and the expected output parameters to gain more confidence of this new gas turbine or enhancement of an existing gas turbine. Typical design input parameters are pressure, temperature, speed, load, etc. and product output parameters are heat rate, efficiency, power output, speed, exhaust temperature values, estimated vibration levels, strain levels, clearance values between rotor to stator parts, etc. Several instrumentations are required at the identified locations of the critical parts and subsystems from the inlet to the exhaust of the gas turbine during the prototype testing. The gas turbine is tested with all these instrumentation with several identified operating conditions, viz. speed, load, etc., to gather actual values of the operating parameters and responses of the subsystem and the parts at these operating conditions. All these instrumentations require modification of the parts for the placement of the instruments and its routing of the cable to the data acquisition system. Pressure probes, thermocouples, strain gages, accelerometer, etc. are placed at the identified locations after necessary modifications are made to the part for installing the instruments. Use of pressure probes and thermocouples for the flow-path measurement needs additional fixtures which are verified for flutter and flow disturbance. All these modified parts and the additional fixtures are validated through appropriate analytical simulations to ensure design robustness for successful test campaign and data acquisition. Exhaust system is one of the vital parts of any gas turbine which facilitate handling the exhaust gas efficiently. Measurement of temperature, pressure and vibration levels are some of the critical parameters needed to ensure design robustness of the exhaust system. This paper is intended to describe the steps followed in performing analytical assessment to achieve design robustness of the instrumented exhaust system.
Performance Prediction of a Swash Plate Piston Pump Using 3D CFD Simulation
Authors: Godavarthi Raghu Vamsee , Maiti Dipak , Ding Hui
Published: February 2024

Axial piston pumps are widely used for inlet fogging, wet compression and NOx reduction in gas turbines and also as a part of hydraulic systems in landing gears and brakes of aircraft. These pumps operate at high pressures and flow rates with greater efficiency due to their high power to weight ratio. The design of such high-pressure pumps is challenging as its performance is affected by cavitation/aeration and various leakages among the piston, cylinder block, valve plate, slippers and swash plate at high operating speed.

Computational Fluid Dynamics (CFD) simulations provide detailed insights of the flow field and pressure for understanding the performance of a pump and assist in developing an efficient and reliable product in a shorter time. In the present work, the performance of a swash plate piston pump with 9 pistons is simulated at 100bar using 3-D CFD software Simerics-MP+. The rotation and deformation of the pumping chambers along with all the leakage gaps is modeled for accurate prediction of the pump performance. The change in piston displacement as it rotates based on swash plate angle is captured in the simulation. Conformal Adaptive Binary-tree (CAB) algorithm [1] is used to generate a high quality grid dominated by Cartesian cells and the mesh motion is captured through volume remeshing. The governing flow equations are solved using Finite Volume Method (FVM) in Simerics-MP+. The fluid compressibility and cavitation/aeration due to entrained and dissolved air is considered by solving the cavitation model developed by Singhal et al [2] to predict the fill speed accurately. The swash plate angle is varied to predict the change in flow rate at a fixed pump speed. The effect of leakage gaps on the volumetric efficiency of the pump is predicted at different pump speeds. The pump performance at different speeds along with leakage effects, cavitation effects, vapor/gas bubble locations are presented in detail in this study.
Study of Tandem Rotor Dual Wake Interaction With Downstream Stator Under Unsteady Numerical Approach
Authors: Singh Ajey , Mistry Chetan
Published: February 2024

This paper highlights the intricate rotor-stator interaction between a tandem bladed rotor and a single-bladed stator in the light of unsteady numerical simulations. With the promising pressure rise capability of the tandem bladed compressor stage, it becomes obligatory to investigate the rotor-stator interaction owing to its dominant effect on overall stage performance. The multi-passage rotor-stator unsteady simulations have been performed using transformation methods in ANSYS CFX. Due to the presence of two highly loaded rotor blades, the tandem rotor exhibits peculiar rotor-stator interaction in terms of multiple wake impingement on the stator. Incorporating tandem blading on the rotor instead of the stator (which is more common) has some aerodynamic leverage but it also constricts the design envelope in terms of choice of blade axial overlap and percentage pitch. This results in managing the desired loading by varying blade overlap from hub to shroud with careful loading distribution. The variation of aerodynamic loading from hub to tip for both the rotor blades results in spanwise varying wake strength. The initially distinct wake structures merge with a certain frequency resulting into a thicker wake. This changes the incidence on the downstream stator. Additionally, the rotor blades are highly loaded in the tip region which results in the complex interaction between end-wall boundary layer and tip leakage flow. Cumulatively, these conditions constitute a challenging aerodynamic field for the downstream stator. The incidence change caused by the velocity defect at the rotor exit plane affects the aerodynamic loading of the stator. The tip leakage flow behavior is entirely different in a tandem bladed rotor due to the presence of blade overlap. The study focuses on the qualitative interaction between the rotor wakes and blockage with the downstream stator and put forwards some aspects of the tandem rotor-single stator stage design especially for core compressors of aero engine application.
Implementation of Flow Control Methods for Design of Connecting Duct of Annular Sector Cascade Tunnel
Authors: Bhavsar Hardikkumar , Mistry Chetan S.
Published: February 2024

In order to investigate the part clearance leakage flow field through a variable area nozzle turbine (VANT), an experimental setup of the annular sector cascade (ASC) with eight numbers of passages is being developed. The second stage low-pressure turbine stator from Energy Efficient Engine proposed by Pratt and Whitney was selected and modified for the VANT concept. The intermediate turbine duct (ITD) – connecting the high-pressure turbine with the low-pressure turbine was inevitable to be incorporated between the wind tunnel and ASC test section for the following reasons: a) ITD will ensure the geometric continuity on the hub and casing end-walls, and b) it will provide realistic entry flow field with radial pressure gradient. The diverging shape of the ITD with continuously increasing mean radius imposes a major challenge to achieving the required inlet flow angle with periodicity at the entry of the ASC. Hence, the present study focuses on the challenging work of modifying the existing annular ITD to achieve the required inlet flow for ASC. The various geometries of the ITD, including different flow control methods, were numerically analyzed using commercial software ANSYS CFX®. The flow field of the numerical simulations at multiple locations was analyzed using flow angle and its distribution, velocity streamlines, static pressure recovery coefficient, and total pressure loss coefficient. It was found that the IGVs direct the flow through the ITD, and approximately the required flow condition with periodicity was achieved at the entry of the test vane cascade. As an active flow control method, an opening slot was modelled on the casing end-wall at the upstream region of the test vane cascade. However, the numerical analysis shows an adverse effect on the flow angle distribution at the entry of the cascade. The change in axial spacing between IGVs and the test vane cascade shows a negligible effect on the cascade entry flow field.
Influence of Mechanical Properties on Compressor Rotor Blade Fatigue Life : A Reliability Approach
Authors: Muthu S. Esakki , K Ramesh , Degaonkar Girish K , C. A. Neeralagi , Roy Hardik
Published: February 2024

The compressor blade which operates at higher pressure and higher temperature conditions are made out of titanium alloys. The fatigue life of the compressor blade depends on load, geometry and material. In material, parameters like Young’s modulus, ultimate tensile strength and fatigue strength plays a vital role in fatigue life. The scatter / variation in each parameter’s influence the fatigue life. The compressor rotor blade under study is analyzed for material properties scatter. The stress scatter and corresponding material parameters were used to estimate the fatigue life scatter. The reliability analysis was carried out on fatigue scatter. The influence of each material parameter was studied on fatigue life of the blade. The parametric analysis was done to find out the influence of each mechanical properties effect on compressor blade fatigue life.
Effect of Variable Tip Clearance at the Inlet and Exit of a Radial In-Flow Turbine
Authors: Harish D. , Bharathan R. D. , Kumar C. Kishore , Kapil Sharad , Jehoash Jatin Kumar , Prasad D. Kishore , Ramana Murty S. V.
Published: February 2024

Radial inflow turbines are widely used in turbochargers, in which they drive the centrifugal compressor, and in auxiliary power units (APUs). Losses in a radial inflow turbine are comprised of profile losses, secondary losses and clearance losses. Therefore, in order to increase the efficiency of the radial inflow turbine, it is necessary to keep the losses due to clearance too as low as possible. There are two clearances in a typical radial turbine — Tip clearance and Hub clearance. The effects of variable tip clearance at the inlet and exit of a radial turbine are investigated, and the relative losses associated with each clearance variation are quantified. Hub clearance is formed due to scalloping. This is carried out to decrease the hub stress and polar moment of inertia, which leads to additional losses. In this paper, the effect of variable tip clearance and scalloping on the performance of a radial turbine is studied through use of numerical simulation.
Non-Axisymmetric Stator Hub Endwall Contouring for Tandem Bladed Axial Compressor Stage
Authors: S. Priyanka , Mistry Chetan S. , Roy Arnab
Published: February 2024

Secondary flow within the compressor stator passage induces 3D flow separation and reduces the flow passage which in turn decreases the efficiency, operating range and pressure rise capacity of the compressor stage. The aim of this study is to reduce the effects of secondary flow losses near the lower span region by implementing a Non-Axisymmetric Hub Endwall contour. The linear stator hub cascade is used by utilizing point displacement method in conjunction with optimization. The numerical simulation was performed using ANSYS CFX® to solve steady state 3D-RANS equation with SST K-ω turbulence model for a single blade passage with translational periodicity, Parameterization of Hub endwall was done using commercial software CAESES® using control points based NURBS curves. The optimization for the NAEW was performed using ANSYS Direct optimization by availing the ASO (Adaptive Single Objective) optimization method, which is the combination of optimal space filling, kriging response surfaces and MISQP (Mixed-integer sequential quadratic programming). The optimization has been done for the design incidence case, which resulted in the reduction of total pressure loss coefficient of maximum 1.2%. The same optimized endwall contour has been numerically studied for the different incidence angles of −4 degree and +4 degree. It was found at the −4 degree incidence angle, the blade stall has been removed completely. The change in the endwall pressure gradient and thereby spanwise pressure gradient bring the change in the flow structure. Reduction of total pressure loss coefficient increases with the increase in the positive incidence angle which is due to the reduction of loss coefficient along the spanwise direction increases. The endwall contour of Design A found to be more favorable compared to other profiles.
Numerical Investigation on the Optimization of Angled Effusion Holes of Liner Assembly of Micro Gas Turbine Engine Combustor
Authors: Shahi Nivedita , Divyansh Ayush , Tyagi Vatsal , K. P. Shanmugadas
Published: February 2024

The present work investigates the flow topology generated by the angled effusion holes of a compact combustor liner assembly. The combustor geometry is designed in a way that the flow conditions are selected corresponding to a 1 KN thrust for a micro gas turbine engine. The combustor operates based on a lean burn combustion technology in which 70% of the air is admitted through the injector and the remaining is sent to the annulus passage of the liner assembly which aids in cooling the liner walls. The angled effusion holes were designed initially on the basis of existing empirical formulas and further iterated according to the numerical analysis to provide an optimum cooling pattern across the combustor length. Optimization of the cooling hole geometry is critical to achieve the desired film cooling effectiveness. The various parameters with important effect on film cooling effectiveness include positioning of holes, dimension, shape (elliptical, circular, or other), number of holes. A detailed parametric study is conducted on a number of geometrical features related to the liner holes such as hole diameter, shape, angle with respect to liner axis, the position of holes, number of rows of holes, the transverse and axial pitch. The combustor is operating at a maximum pressure of 14 bar with a mass flow rate 0.2206 Kg/s coming from the compressor at a temperature of 595K based on the Brayton cycle analysis done for 1kN thrust. The combustor liner is operated at zero pressure drop focusing the geometry in absence of injector where 4 % pressure drop is considered through annulus passage. The combustor is having 70-30 % mass flow split and a uniform temperature of 900K is taken inside the combustion chamber. The combustor cooling is optimized for the minimum pressure drop across the liner. The study is carried out using numerical analysis on the lean burn liner system designed to optimize wall temperature conditions to have control over temperature of emissions reaching the turbine blades and have better service life as a result.

The circular holes of 1.82 mm diameter inclined at an angle of 18-degree result in the best film cooling effectiveness among all geometries. This is decided basis of the temperature plots, pressure drop through holes, and pressure drop across the entry and exit of holes favorable for optimal film cooling effectiveness.
Heat Transfer Radiation Coefficient Measurements on Different Shaped Sections of a Piping System
Authors: Elsharafi Mahmoud , Criss Ty , Vora Nevil , Alkathiri Abdullah
Published: February 2024

The understanding of heat transfer is very important to the success of any project or product dealing with thermal processes whether as a product or an unintended byproduct. There are three subcategories within heat transfer. These are convection, conduction, and radiation. Radiation, which is the purpose of our research, deals with electromagnetic waves being emitted as the charges within the particles themselves move. These waves radiate to other surfaces or the atmosphere which transfer thermal energy from which it was generated. Radiation is dependent on several factors, such as shape, and material properties. The goal of this project was to create a model of the temperature and heat losses associated with a typical piping system consisting of different shaped pipes. This would allow improvement in existing systems through the recommendations gathered from our research to increase efficiency and maximize or minimize thermal energy loss depending on the goal of the specific piping system. To do this, an apparatus consisting of three different shaped pipes will have a heated gaseous medium flowing through it, in which the temperature will be recorded, and analyzed. The focal point of the data would be the measured temperature from thermocouples on each shaped pipe. By designing a piping system consistent with those in industry, we can discover more efficient ways to contain and/or utilize thermal energy in productive ways through the use of unconventional geometrical shaped pipes.
A Computational Fluid Dynamics Approach for Hospitalization at Home During the Pandemic
Authors: Al-Rawi Mohammad , Wang Lulu , Zhou Hong
Published: February 2024

Recently due to the COVID-19 pandemic, caused by the SARS-COV-2 virus which spreads via airborne transmission, there has been greater attention on the concept of acute hospitalization at home (HaH). Whilst HaH has been investigated for over three decades, the need for development of this method was highlighted by the pandemic which overloaded tertiary (hospital) health care services. HaH requires advanced medical equipment that is not always readily available for non-wealthy households; however middle-class households have the means to purchase less advanced ventilation equipment to treat the air, for example, using HEPA filters in a particulate air cleaner (CC 410). To assess the ventilation efficiency, Computational Fluid Dynamics (CFD) modelling using ANSYS CFX 2022 R2 is applied and then validated experimentally to ensure the reduction of CO2 concentration in the HaH space in terms of age of air (AoA). Additionally, thermal comfort parameters were assessed using CFD modelling and validated experimentally. The predicted mean vote (PMV) and percentage dissatisfaction (PPD) while running the device were aligned with the ASHRAE 55 standard to ensure users would not switch off the device based on dissatisfaction or discomfort. The results show that the device improved the AoA in 105 seconds of the time of CO2 produced by one of the occupants in the room. This type of analysis is helpful to reduce the time during a crucial period of treatment, when infected occupants are hospitalized at home up to a maximum space of 140 m2.
Mesh Independency Analysis for Aorta Geometry Using a Computational Modelling Approach
Authors: AL-Rawi Mohammad , Belkacemi Djelloul , Al-Jumaily Ahmed M.
Published: February 2024

Cardiovascular diseases have been investigated computationally by biomedical engineers to find new diagnoses for these diseases. Computationally simulating diseases occurring at the aorta artery and more specifically aortic arch, requires a comprehensive workstation computer with an advanced processor and graphics card to create a suitable mesh for the elements. The mesh process is essential: sufficient granularity of the mesh increases simulation accuracy, providing the ability to solve the governing partial differential equations in an increasingly realistic three-dimensional form in the allocated cell. For the complicated geometry of an artery, it is essential to reach a suitable mesh, validated with clinical data, to ensure the computational fluid dynamics model (CFD) has minimal error. Therefore, in this study we investigated different types of mesh, applying different element sizes, and comparing the results with clinical data for a healthy aorta using ANSYS 2021 R1-Fluent. Tetrahedral and Polyhedral meshes were applied for the same element size (1.0, 0.8 and 0.6 mm) with a growth rate of 1.2 and 10 boundary layers for the artery wall using the same boundary conditions to investigate the pressure, velocity waveforms and wall shear stress (WSS) at the aortic arch. The boundary conditions used in this study are the blood flow waveform applied at the ascending aorta and iliac pressure waveform applied at the iliac bifurcation based on clinical data. The results show that the Tetrahedral mesh obtained higher average pressure values with 2.8% at the systolic; however, the diastolic pressure values are the same for the 1 mm element size. Comparing that to the element size of 0.8 and 0.6 mm, the pressure difference was 2.9% and 3.1% respectively for the systolic pressure with a phase time of 0.01 s.
Targeted Particle Fractionation Technologies: Proof of Concept
Authors: Minette Michael J. , Burns Carolyn A. , Phillips Nathan R. J. , Davidson Casie L. , Bamberger Judith A. , Serkowski Jason E. , Pease Leonard F.
Published: February 2024

Most methods of particle-size separation involve particle fractionation which is often done by filtration or the use of screens. This paper provides proof-of-concept testing for new in-pipe particle fractionation technologies that can be used at laboratory to industrial scales. These technologies are extensions of recent advancements in bump arrays as well as testing of new inline angled-to-the-flow-slats separation technologies.

Experiments were conducted for three targeted particle fractionation technologies to evaluate the in-pipe removal of oversized sands in Newtonian slurries prior to the introduction to bump arrays. This mesofluidic system uses an array of staggered posts at controlled offset angle to establish flow streams within the device. The methods and results of these experiments are described in this paper. This information could be applied in most industrial and laboratory systems to rapidly remove oversized particles from a flowing slurry.
Determination of Material Parameters of In740H Under Different Experimental Situations Using Chaboche Model
Authors: Haddadi Elnaz , Zimnoch Michael , Tabarraei Alireza
Published: February 2024

This paper presents the development and validation of a Chaboche unified viscoplastic constitutive model, incorporating both nonlinear isotropic and kinematic hardening rules, to accurately predict the stress-strain behavior of Inconel Alloy 740H. Inconel 740H is a high-temperature, nickel-based superalloy known for its exceptional mechanical strength, creep resistance, and corrosion resistance, making it highly suitable for extreme environmental applications. The research focuses on determining the material parameters of the unified Chaboche constitutive model and validating its accuracy using experimental data obtained from uniaxial strain-controlled loading tests. The experimental data covers a wide temperature range from room temperature up to 1112 °F, with strain ranges spanning from 0.75% to 1%. The results demonstrate the model’s effectiveness in capturing the complex mechanical behavior of Inconel Alloy 740H under varying conditions, providing a valuable tool for design and engineering applications in high-temperature environments.
Assessing Acoustic Piping Vibration on a Naphtha Splitter Column Overhead Line
Authors: Herrera Sierralta Carlos , Alsokairan Ibraheem Saud
Published: February 2024

In gas piping systems exposed to pressure drops, the high frequency generated by the flow could provoke acoustic induced vibration.

Acoustic induced fatigue is a particular concern as it could lead to catastrophic failure of piping components in a significant short period of time in some cases in a matter of days, hours or minutes. The reason being that this type of excitation can generate high frequency vibration of the pipe wall which takes the form of pipe wall flexural modes, resulting in high dynamic stresses with the potential of generate fatigue at circumferential discontinuities on pipe wall.

The typical approach of the designers is to conduct the acoustic induced vibration (AIV) screening by calculating the acoustic power level at the source (PWL) as per the Energy Institute’s screening method.

Alternatively, there is a different methodology proposed by Eisinger, which is based on an acoustic induced vibration fatigue chart corresponding to the relationship between the acoustic energy parameter in terms of the downstream Mach number, pressure drop, diameter and wall thickness.

While the aforementioned screening methods can be deemed sufficient during the detailed engineering phase of the facility, practitioners are advised to bear in mind, that any anomaly detected during commissioning and start-up after construction of the piping system should be thoroughly assessed by a dedicated study, including the verification that the “as-built” matches the issued for construction documentation and the thorough analysis of vibration data, etc. collected at field.

This paper describes a case study of a piping system that during the start-up of the facility was observed with abnormal levels of noise and it was perceived with a relatively high frequency piping vibration.

The system in question was a particular concern as the AIV screening methods were circa the border line of the acceptability criteria for both the Energy Institute and Eisinger Method, this finding plus the abnormal vibration and noise at field raised the doubt of the owner of whether or not the system was at risk of having an acoustic induced fatigue failure.

Consequently, the system was thoroughly studied by collecting and analyzing vibration and strain gauges data from the field to primordially corroborate the original detailed design, and to conduct fatigue life predictions that allowed to determine that the system was not at risk of fatigue.
Challenges of Purging Air With Natural Gas and Hydrogen Blends in Pipe Segments
Authors: Botros Kamal K. , Hill Colin , Ziade Paul , Johansen Craig , Van Boven Greg
Published: February 2024

The aspiration for blending hydrogen (H2) into natural gas (NG) in gas transmission systems is high and is happening globally. However, several design and operational aspects need to be developed to ensure the safe and reliable delivery of these blends to the end users. One of these aspects is the development of an effective purging procedure of air with NG+H2 blends during the commissioning of a pipe section. The present research examines various aspects of the purging procedures and attempts to address salient parameters and conditions when the NG+H2 blend is the purging gas. Three principal aspects were investigated, namely: 1) The stratification velocities of the air and gas wave fronts for different NG+H2 blend ratios, 2) The interfacial turbulent diffusivity coefficients between air and NG+H2 blends that determine the extent of the mixing spread as purging progresses, and 3) The applicability of the minimum stratification velocity to smaller pipe sizes ≤ NPS 4. The present investigation found that the stratification velocity of the air wave is higher than that of the NG+H2 wave, and both deviate from the classical value corresponding to Fr # = 0.707 assumed in AGA Purging Principles and Practices. Initial results of the diffusivity coefficients show an upward deviation from that currently in use in the gas transmission industry.
A Composite Structure for Low-Frequency Sound Absorption With Continuous Broadband Under High Sound Pressure Excitations
Authors: Zhu Junzhe , Gao Hao , Qu Yegao , Meng Guang
Published: February 2024

High-amplitude sound absorption in the low-frequency range is of great interest because of its vast engineering applications. This work is associated with a novel composite multilayer structure for high-amplitude sound energy attenuation. An analytical model based on the equivalent fluid method by using JCAL (Johnson-Champoux-Allard-Lafarge) model is used to predict the sound absorption performance of the multilayer structure both under 90 dB excitation and 140 dB excitation. Numerical simulation is applied to verify the accuracy of the analytical model. This work demonstrates four samples with different parameters to compare the analytical and numerical results. The results of the two methods agree well with each other. The resonance frequencies of all samples locate in the low-frequency range. It is also found that the resistance of the multilayer structure is enlarged as the sound excitation increases, which can be utilized to design high-intensity sound energy absorbers. The sound absorption coefficient is improved under high sound pressure excitations. To further broaden the sound absorption bandwidth in the low-frequency range, a composite multilayer structure with three absorption units is designed to achieve high-efficiency sound absorption continuously. The composite structures combine the sound absorption performance of each unit and three absorption peaks occur in the low-frequency range. The experiments are performed to verify the sound absorption performance of the proposed structure. The results show that the designed composite multilayer structure has a superior noise reduction capability with continuous bandwidth under high sound pressure excitations in the low-frequency range.
Motion Control of a Robot by Means of Q-Learning Using the Example of Locomotion
Authors: Bußmann Tobias , Schilberg Daniel
Published: February 2024

The aim is to program a robot who learns a movement using Q-Learning. A neural network is used to process the data. To check whether the robot has learned successfully, four requirements were made of the robot. Various experiments were carried out with the robot, in which the parameters of the learning algorithm or the neural network were varied. The results of the experiments show that the robot fulfills every requirement, except in the experiments where the neural network diverges and the robot does not learn any strategy to reach the goal.
Virus Transmission Aboard a Transit Bus
Authors: Bonifacio Jeremy , Rahai Hamid , Horstman Raymond
Published: February 2024

Unsteady numerical simulations of virus transport released from an infectious passenger aboard a transit bus have been investigated. The goal of the investigation was to explore methods for controlling the spread of a virus or any contaminants aboard a public transportation system for improving public health. The virus was modeled as a 2.5 μm round solid particle released from the mouth of the infectious passenger at a rate of 21 particles per second at a mouth velocity of 0.278 m/sec. The air delivery to the cabin was two linear ceiling slots spanning the length of the bus delivering 59.38 m3/min (2,097 CFM) of air at a mean velocity of 1 m/sec. Axial linear exhaust slots placed on the side walls have been investigated to contain and prevent the spread of the virus to the other parts of the cabin. Simulations were performed for both cases of the bus in transit and at the bus stop when the drop-off door was opened. Results indicate during the transit, virus spread was contained to passengers sitting in immediate front and behind the infectious passenger and the level of virus concentration could merit an increased risk of infection with increased virus residence time. However, augmented air mixing was observed between inside and outside air during the passenger drop-off with viruses spread to the front and back of the bus with reduced concentration and risk of infection. Analytical analyses of the risk of infection using the Wells-Riley equation have shown that with axial slots, the viruses are contained around the infectious but with the increased concentration, the risk of infection for these passengers is increased.
ADAMS Multibody Simulation of Jamming in the Recirculation Channel of a Single-Nut Ball Screw
Authors: Bertolino Antonio Carlo , De Martin Andrea , Guida Roberto , Sorli Massimo
Published: February 2024

Ball screw jamming is a significant concern as it can have a detrimental impact on the performance and reliability of ball screw systems, potentially leading to a complete loss of mechanical power transmission. However, no studies in the literature have conducted dynamic analyses to investigate the effect of such fault on the performance of this mechanism. This article reports on the findings of a simulation analysis using a detailed multi-body dynamic model developed in the MSC ADAMS environment to exploit its capabilities of describing contacts between arbitrary shaped bodies and accounting for the complete dynamics of each subcomponent. The analysis focused on a single-nut not preloaded ball screw with three axisymmetric sphere internal recirculating circuits and compliant constraints. The results of an extensive validation process of the mathematical model against literature data in nominal conditions are firstly presented to enhance the reliability of the results. Then, the outcomes of the simulation campaign are presented, investigating the impact of different numbers of recirculation channel jammings on the overall mechanical efficiency and the internal behavior of the spheres, for different lubrication conditions. The findings of this study provide valuable insights into the behavior of ball screw systems under jamming conditions and can lay the foundations for in-depth analyses and the development of a prognostic framework for such devices.
Design Improvement and Field Testing for Biogas Power Generation System
Authors: Song Yuxin , Duan Shawn
Published: February 2024

This paper details the process of obtaining high-purity methane from biogas by using specific filtering and drying devices and utilizing it as fuel to drive generators for electricity generation. The system is designed to filter out most impurities from the biogas produced from the fermentation of biological waste (cow manure), using a purification device to extract methane. The conversion kit uses methane to run the generator to produce electrical energy. Field tests were carried out to ensure the proper functioning of the experimental setup, considering interference factors such as temperature changes, weather factors, and natural fermentation effects. The design flaws were identified during the testing, such as airtightness problems that led to system failure and inaccurate data. Control variable method was used to resolve these issues, and some parts were replaced through redesign and testing to ensure the proper functioning of all components. Finally, it was found that adding a certain amount of Sodium hydroxide (NaOH) to the water tank significantly improved the impurity removal effect, achieving the expected result. The testing results showed that percentage of methane reached 89.57%, while carbon dioxide dropped from 48.17% to 5.02%, and Hydrogen sulfide was removed completely. The generator with a conversion kit was able to produce 0.0705 kw · h of electricity by running on 8-Psi purified biogas for three minutes. Redesign and testing have validated design idea and achieved goal of the project.
Impact of Online Versus In-Person Group Work on Behavioral Peer Evaluations in Engineering Capstone Team Projects
Authors: Mishur Juliana , Niemi Sean R. , Underhill Janna L. , Traum Matthew J.
Published: February 2024

A critical open question in the mechanical engineering pedagogical literature is whether Capstone senior design can be taught as effectively online as in-person with emphasis on whether group work conducted under these contrasting conditions is equally effective. The onset of COVID-19 induced a natural experiment enabling comparison of engineering student group work conducted in-person versus all-online.

Group work is an essential element of mechanical engineering education codified by Student Outcome 5 of ABET Criterion 3 (Groupwork). Peer evaluation is a common engineering group work assessment, especially in Capstone design courses. In this paper, recurring peer evaluations are evaluated to quantify how well students performed in groups within a longitudinal study conducted across five semesters of a mechanical engineering Capstone senior design course.

In UF’s Mechanical Engineering Capstone courses, recuring peer evaluation surveys tied to group assignment deadlines were already established prior to COVID-19. By continuing to deploy this same survey when courses transitioned online during the pandemic, three full semesters of group performance data were collected when students were forced to meet remotely. As students returned to campus, the same survey provided comparative data for two semesters when students were meeting in person. These collected data represent a quantitative tool to evaluate how online vs. in-person group meeting setting impacts the quality of teamwork.

This work shows that online vs. in-person meeting environments DID NOT have statistically significant impacts on teamwork performance for mechanical engineering Capstone students in the semesters being evaluated. This result suggests that ABET Criterion 3 Student Outcome 5 can be met just as effectively in online or in-person Capstone courses.

This important result debunks the misconception that the quality and fidelity of Capstone groupwork is somehow diminished when senior design is taught online to learners remote from each other over the Internet. This finding adds to the growing body of evidence supporting the viability of an all-online Bachelor of Science in mechanical engineering program capable of receiving and maintaining ABET accreditation. Moreover, a forward-looking online ME program can include an effective Capstone senior design course with rich student groupwork interactions of quality equal to those experienced by students when meeting in-person.
Experimental Investigation and Optimization of the Effect of Burnishing Process Parameters on Surface Roughness and Hardness of Al 2036
Authors: Asadbeygi Alireza , Rezaei Hamed , Jalali Aghchai Abdolhossein
Published: February 2024

Surface roughness and hardness of work pieces have been always of great importance in the manufacturing industry. Burnishing as a surface treatment process is taken into consideration as a result of its great effect on surface quality. The objective of this work is to investigate the effect of roller burnishing process parameters on roughness and hardness of work pieces for aluminum 2036 alloy. Burnishing speed (Vc), feed rate (Vf), applied force (F) and depth of penetration (Dp) are assumed as the input parameters. In the experimental procedure, tests were designed based on Central Composite Design (CCD) design of experiments. A quadratic regression model for the surface roughness reduction is proposed and a parametric study is performed based on the developed model. Finally, the process parameters were optimized in order to achieve the lowest value of surface roughness. The results indicate that following the burnishing process, the average surface roughness of 31 samples decreased by 49.7% and the average surface hardness increased by 25.1%. By applying the optimal process parameters, A roughness reduction of 1.19 Ra (84%) was achieved, which was predicted by the model with an error of 8.4%.
Development and Aerodynamic Performance of an Axisymmetric-Sector Inertial Particle Separator Wind Tunnel
Authors: Rodriguez-Saenz Cesar R. , Loth Eric , Smith C. Frederic
Published: February 2024

An Inertial Particle Separator (IPS) can help reduce performance degradation of gas turbine engines used in aircraft when operating in dusty environments. In particular, an IPS geometry uses flow curvature to separate particles from the core flow path, so they are ideally fully directed into the scavenge flow path. To better understand the multiphase flow physics and performance of an IPS system, an axisymmetric-sector vertical bifurcated wind tunnel was developed and tested. This wind tunnel was designed to emulate the fluid and particle physics associated with the axisymmetric flow bifurcation for typical operational conditions. The wind tunnel employs a 50-degree sector angle to allow optical accessibility combined with a ratio of throat height to throat radius of 0.17. The tunnel uses a geometry representative of typical systems in terms of air flow velocities but with a size of about 40% (based on throat height) relative to full-scale systems. The wind tunnel air flow is achieved with two exhaust blowers and a calibrated control system, which allows for high mass-flow stability and a wide range of flow split ratios between the core and scavenge flows. To characterize the tunnel’s aerodynamic performance, measurements were taken for mass-flow stability and surface flow visualization to investigate corner flows and separation regions. The results indicate that the flow is highly stable and has separation regions qualitatively similar to those seen in 2-D facilities.
Fast Fourier Transform Method in Peridynamic Micromechanics of Composites
Authors: Buryachenko Valeriy A.
Published: February 2024

We consider a static linear bond-based peridynamic (proposed by Silling, see J. Mech. Phys. Solids 2000; 48:175–209) composite materials (CMs) of a periodic structure. In the framework of the second background of micromechanics (called also computational analytical micromechanics), one proved that local micromechanics (LM) and peridynamic micromechanics (PM) are formally similar to each other for CM of both random and periodic structures. It gives an opportunity for straightforward generalization of LM methods (including fast Fourier transform, FFT) to their PM counterparts. So, in the PM counterpart of the implicit periodic Lippmann-Schwinger (L-S) equation in LM, we have three convolution kernels corresponding to the properties of the matrix, inclusions, and interaction interface. Eshelby tensor in LM depending on the inclusion shape is replaced by PM counterparts depending on the shapes of inclusions and interaction interface (although the Eshelby concept of homogeneous eigenfields does no work in PM). The mentioned tensors are estimated one time (as in LM) in a frequency domain (also by the FFT method). The polarization schemes of the solution of L-S equation in the Fourier space have one primary unknown variable (polarization) whereas the PM counterpart contains three primary ones estimated at each step which are formally similar to LM case. Computational complexities O(Nlog2N) of the FFT methods are the same in both LM and PM.
Residual Stress Evaluation of Multilayer Viscoelastic Composites Using Ultrasonic Acoustoelastic Effects
Authors: Jiang Houfu , Shen Yanfeng , Zhang Tao
Published: February 2024

This paper proposes the advancement of residual stress evaluation technology, utilizing the ultrasonic acoustoelastic theory by detecting the variation of wave speed under different stress conditions. The target structure for nondestructive evaluation task is a typical multilayer, viscoelastic composite shell of a solid rocket motor. By carrying out an in-depth theoretical analysis with Finite Element Modeling (FEM), the sensing sensitivity of the probing ultrasonic wave characteristics are studied systematically. The effective generation of interface guided wave modes is investigated, where the pure wave mode excitation is accomplished. To monitor the residual stress state, a theoretical model is established by considering the stress gradient in each layer, indicating the current stress condition inside the testing object. Consequently, via the comprehensive consideration of transducer dimensions, center frequency, and the signal attenuation, the most effective residual stress monitoring setup is established and the sensing signals are recorded by piezoelectric wafer active sensors (PWAS) placing on the object. Finally, different values of prestress are applied to the object, while the nonlinear constitutive law of the layered materials is implemented. The pattern between the sensing signal and the residual stress state is identified. The amplitude and the Time of Flight (TOF) of sensing signals could provide indicative information for evaluating the residual stress state based on the acoustoelastic effects, including the change of wave speed under various prestress loading conditions. The findings of this research possess superb application potential for the evaluation of residual stresses in multilayer composites for enhancing manufacturing quality and avoiding unexpected failures in solid rocket motor industry. This paper finishes with summary, concluding remarks, and suggestions for future work.