Development of Combustion-Driven Thermoacoustic Engine

2008 ◽  
Author(s):  
Najmeddin Shafrei Tehrany ◽  
Chien Shung Lin ◽  
Cory Bloomquist ◽  
Jeongmin Ahn ◽  
Konstantin Matveev
Keyword(s):  
Heat Transfer ◽  
Acoustic Power ◽  
High Energy ◽  
High Energy Density ◽  
Small Scale ◽  
Developmental Study ◽  
Prime Mover ◽  
Power Devices ◽  
Thermoacoustic Engine ◽  
Thermoacoustic Engines

Miniature thermoacoustic engines driven by combustion and producing electricity are promising candidates for small-scale power devices. The elemental development of the system including a small thermoacoustic engine and a Swiss roll combustor is discussed in this work. A standing-wave thermoacoustic prime mover consists of a resonator with a stack of porous material inside where a temperature gradient is maintained. This engine generates acoustic power from heat. The sound energy can be converted in electricity by an electroacoustic transformer. The Swiss roll combustor utilizes the high energy density of hydrocarbon fuels in order to provide the necessary heat transfer required to generate acoustic power from the engine. Some results of this developmental study are presented.

Modeling of Thermoacoustic Resonators With Nonuniform Medium and Boundary Conditions

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Konstantin I. Matveev ◽  
Sungmin Jung
Keyword(s):  
Boundary Conditions ◽  
Acoustic Power ◽  
Solid Surfaces ◽  
Small Scale ◽  
Nonuniform Medium ◽  
Thermoacoustic Engine ◽  
Efficient Calculation ◽  
Thermoacoustic Engines ◽  
The Subject ◽  
Low Amplitude

The subject of this paper is modeling of low-amplitude acoustic fields in enclosures with nonuniform medium and boundary conditions. An efficient calculation method is developed for this class of problems. Boundary conditions, accounting for the boundary-layer losses and movable walls, are applied near solid surfaces. The lossless acoustic wave equation for a nonuniform medium is solved in the bulk of the resonator by a finite-difference method. One application of this model is for designing small thermoacoustic engines. Thermoacoustic processes in the regular-geometry porous medium inserted in resonators can be modeled analytically. A calculation example is presented for a small-scale thermoacoustic engine coupled with an oscillator on a flexing wall of the resonator. The oscillator can be used for extracting mechanical power from the engine. A nonuniform wall deflection may result in a complicated acoustic field in the resonator. This leads to across-the-stack variations of the generated acoustic power and local efficiency of thermoacoustic energy conversion.

scholarly journals Comparison of Heat Transfer Enhancement Techniques in Latent Heat Storage

2020 ◽  
Vol 10 (16) ◽  
pp. 5519 ◽  
Author(s):  
William Delgado-Diaz ◽  
Anastasia Stamatiou ◽  
Simon Maranda ◽  
Remo Waser ◽  
Jörg Worlitschek
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Latent Heat ◽  
Heat Transfer Performance ◽  
Thermal Power ◽  
High Energy ◽  
High Energy Density ◽  
Evaluation Procedure ◽  
Transfer Performance ◽  
Experimental Conditions

Latent Heat Energy Storage (LHES) using Phase Change Materials (PCM) is considered a promising Thermal Energy Storage (TES) approach as it can allow for high levels of compactness, and execution of the charging and discharging processes at defined, constant temperature levels. These inherent characteristics make LHES particularly attractive for applications that profit from high energy density or precise temperature control. Many novel, promising heat exchanger designs and concepts have emerged as a way to circumvent heat transfer limitations of LHES. However, the extensive range of experimental conditions used to characterize these technologies in literature make it difficult to directly compare them as solutions for high thermal power applications. A methodology is presented that aims to enable the comparison of LHES designs with respect to their compactness and heat transfer performance even when largely disparate experimental data are available in literature. Thus, a pair of key performance indicators (KPI), ΦPCM representing the compactness degree and NHTPC, the normalized heat transfer performance coefficient, are defined, which are minimally influenced by the utilized experimental conditions. The evaluation procedure is presented and applied on various LHES designs. The most promising designs are identified and discussed. The proposed evaluation method is expected to open new paths in the community of LHES research by allowing the leveled-ground contrast of technologies among different studies, and facilitating the evaluation and selection of the most suitable design for a specific application.

Numerical and Experimental Analysis of Laser Surface Remelting of Al 9wt% Si Alloy Samples

2008 ◽  
Vol 587-588 ◽  
pp. 721-725
Author(s):  
Noé Cheung ◽  
Kleber A.S. Cruz ◽  
Noman H. Khan ◽  
Amauri Garcia
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Rapid Heating ◽  
Thermal Action ◽  
High Energy ◽  
Laser Surface ◽  
High Energy Density ◽  
Temperature Fields ◽  
Laser Materials ◽  
Laser Surface Remelting

Laser materials processing has been widely applied in industrial processes due to unique precision and very localized thermal action furnished by the laser’s high energy density and power controllability. With the inherent rapid heating and cooling rates to which this surface layer is subjected, this process provides an opportunity to produce different microstructures from that of the bulk metal leading to useful properties. The aim of this work is to develop a heat transfer mathematical model based on the finite difference method in order to simulate temperature fields in the laser surface remelting process. Convective heat transfer in the remelted pool is taken into account by using the effective thermal conductivity approach. Theoretical predictions furnished by previous models from the literature were used for validation of numerical simulations performed with the proposed model. Experiments of laser surface remelting of Al-9 wt pct Si samples was carried out in the present investigation, and numerical simulations was applied for the laser machine operating parameters. The work also encompasses the analysis of microstructural and microhardness variations throughout the resulting treated and unmolten zones.

Design of a Compliant Industrial Gripper Driven by a Bistable Shape Memory Alloy Actuator

2020 ◽  
Author(s):  
Dominik Scholtes ◽  
Stefan Seelecke ◽  
Gianluca Rizzello ◽  
Paul Motzki
Keyword(s):  
Shape Memory ◽  
High Energy ◽  
Industrial Applications ◽  
High Energy Density ◽  
Small Scale ◽  
Monitoring And Control ◽  
Actuation System ◽  
First Results ◽  
Functional Prototype ◽  
And Control

Abstract Within industrial manufacturing most processing steps are accompanied by transporting and positioning of workpieces. The active interfaces between handling system and workpiece are industrial grippers, which often are driven by pneumatics, especially in small scale areas. On the way to higher energy efficiency and digital factories, companies are looking for new actuation technologies with more sensor integration and better efficiencies. Commonly used actuators like solenoids and electric engines are in many cases too heavy and large for direct integration into the gripping system. Due to their high energy density shape memory alloys (SMA) are suited to overcome those drawbacks of conventional actuators. Additionally, they feature self-sensing abilities that lead to sensor-less monitoring and control of the actuation system. Another drawback of conventional grippers is their design, which is based on moving parts with linear guides and bearings. These parts are prone to wear, especially in abrasive environments. This can be overcome by a compliant gripper design that is based on flexure hinges and thus dispenses with joints, bearings and guides. In the presented work, the development process of a functional prototype for a compliant gripper driven by a bistable SMA actuation unit for industrial applications is outlined. The focus lies on the development of the SMA actuator, while the first design approach for the compliant gripper mechanism with solid state joints is proposed. The result is a working gripper-prototype which is mainly made of 3D-printed parts. First results of validation experiments are discussed.

scholarly journals Diffusion and radiation in magnetized collisionless plasmas with small-scale Whistler turbulence

2016 ◽  
Vol 82 (2) ◽  
Author(s):  
Brett D. Keenan ◽  
Mikhail V. Medvedev
Keyword(s):  
Numerical Study ◽  
High Energy ◽  
High Energy Density ◽  
Larmor Radius ◽  
Small Scale ◽  
Collisionless Plasmas ◽  
Correlation Scale ◽  
Scale Turbulence ◽  
Solar Plasmas ◽  
High Energy Density Plasmas

Magnetized high-energy-density plasmas can often have strong electromagnetic fluctuations whose correlation scale is smaller than the electron Larmor radius. Radiation from the electrons in such plasmas – which markedly differs from both synchrotron and cyclotron radiation – is tightly related to their energy and pitch-angle diffusion. In this paper, we present a comprehensive theoretical and numerical study of particle transport in cold, ‘small-scale’ Whistler-mode turbulence and its relation to the spectra of radiation simultaneously produced by these particles. We emphasize that this relation is a superb diagnostic tool of laboratory, astrophysical, interplanetary and solar plasmas with a mean magnetic field and strong small-scale turbulence.

Laser-plasma extreme ultraviolet and soft X-ray sources based on a double stream gas puff target: interaction of the radiation pulses with matter

2015 ◽  
Vol 23 (2) ◽  
Author(s):  
A. Bartnik
Keyword(s):  
Large Scale ◽  
Extreme Ultraviolet ◽  
High Energy ◽  
High Energy Density ◽  
Small Scale ◽  
X Ray ◽  
Target Interaction ◽  
University Of Technology ◽  
Photoionized Plasmas ◽  
Intense Radiation

AbstractIn this work a review of investigations concerning interaction of intense extreme ultraviolet (EUV) and soft X-ray (SXR) pulses with matter is presented. The investigations were performed using laser-produced plasma (LPP) EUV/SXR sources based on a double stream gas puff target. The sources are equipped with dedicated collectors allowing for efficient focusing of the EUV/SXR radiation pulses. Intense radiation in a wide spectral range, as well as a quasi-monochromatic radiation can be produced. In the paper different kinds of LPP EUV/SXR sources developed in the Institute of Optoelectronics, Military University of Technology are described.Radiation intensities delivered by the sources are sufficient for different kinds of interaction experiments including EUV/SXR induced ablation, surface treatment, EUV fluorescence or photoionized plasma creation. A brief review of the main results concerning this kind of experiments performed by author of the paper are presented. However, since the LPP sources cannot compete with large scale X-ray sources like synchrotrons, free electron lasers or high energy density plasma sources, it was indicated that some investigations not requiring extreme irradiation parameters can be performed using the small scale installations. Some results, especially concerning low temperature photoionized plasmas are very unique and could be hardly obtained using the large facilities.

Characterization of Piezoelectric Materials for Thermoacoustic Power Transduction

2008 ◽  
Author(s):  
A. Wekin ◽  
C. Richards ◽  
K. Matveev ◽  
M. Anderson
Keyword(s):  
Experimental Study ◽  
Piezoelectric Materials ◽  
Electrical Power ◽  
Power Production ◽  
Piezoelectric Transducers ◽  
Maximum Power ◽  
Small Scale ◽  
Thermoacoustic Engine ◽  
Thermoacoustic Engines

In this work an experimental study of the performance of piezoelectric transducers for power production from a small-scale thermoacoustic engine is presented. Four piezoelectric samples are identified and characterized. These samples are tested on a variable acoustic driver and electrical power produced is measured. Finally, the samples are tested on four experimental thermoacoustic engines to verify the results from the acoustic setup. The maximum power produced is 177 μW from a closed thermoacoustic engine coupled to a 15mm PZT disk.

Experimental Investigation of Convergent and Convergent-Divergent Micro Swirling Flame Behavior and Stabilization

2016 ◽  
Author(s):  
Xintong Zhang ◽  
Yuzhen Lin ◽  
Xin Xue ◽  
Liang Zhang ◽  
Chi Zhang
Keyword(s):  
Axial Velocity ◽  
Average Velocity ◽  
Equivalence Ratio ◽  
High Energy ◽  
High Energy Density ◽  
Small Scale ◽  
Flame Propagation Velocity ◽  
Power Resources ◽  
Swirl Injector ◽  
Swirl Flame

With the miniaturization of mechanical and electrical systems, the demands for small-scale power resources with high energy density have promoted studies on small-scale combustors as well as methods to achieve stable small-scale combustion. In the present paper, a micro swirl injector for a small-scale combustor was designed to study the shape and stability of swirl flame in a 4 mm diameter quartz tube experimentally. The influences of fuel equivalence ratio, axial average velocity in the tube, and structure of the swirler exit were investigated under atmospheric pressure and ambient temperature. The fuel equivalence ratio was in the range of 0.5 to 3.0 and axial average velocity varied from 0.2 to 6 m/s. Methane was used as fuel. Results show that when the axial average velocity increases to a certain value and is kept constant, the methane flame abruptly changes from a swirl flame outside the tube into a stable spindle flame located at the exit of the swirl injector inside the tube within certain limits of equivalence ratio. The equivalence ratio ranges that the shape transition can happen extends with the increase of axial average velocity to certain limits, which is approximately 0.7–1.1 for methane. While under low axial velocity conditions, the spindle flame cannot be formed by the changing of equivalence ratio under a certain velocity, it can be formed and stabilized in a wide equivalence ratio range by slowly decreasing the axial velocity of a high-velocity spindle flame under a constant equivalence ratio of the premixed mixture. A flare at the exit of the swirl injector has little influence on stability limits while it makes the spindle flame to shift down and anchor nearer to the swirler exit. Flame shapes under the structure are characterized, and a brief explanation is given based on the vortex bursting mechanism and the match between local gas velocity and flame propagation velocity.

Heat Transfer Modeling for Vaporizing in Vacuum Electron Beam Welding on Magnesium Alloy

2013 ◽  
Vol 681 ◽  
pp. 314-318
Author(s):  
Yi Luo
Keyword(s):  
Heat Transfer ◽  
Electron Beam ◽  
Magnesium Alloy ◽  
Electron Beam Welding ◽  
High Energy ◽  
High Energy Density ◽  
Deep Penetration ◽  
Transfer Model ◽  
Metal Elements ◽  
Short Period

A heat transfer model for vaporizing in vacuum electron beam welding on magnesium alloy is developed based on the laws of heat conduction and energy conservation. The vaporizing time of the main metal elements in AZ series magnesium alloy is calculated using the model. The results show that the vaporization of Mg element will precede the Zn element under the affecting of high energy density electron beam. The vaporizing times of alloying elements are not entirely dependent on the level of the boiling point, to a certain extent, also dependent on the thermal diffusivity and are closely related to the latent heat of vaporizing and melting of the materials. The change of beam spot diameter of electron beam also greatly alters the heat transfer characteristics of electron beam heat source beam. As the strong vaporizing effect of Mg element will occur within several milliseconds, the keyhole induced by the metal elements vaporizing is formed only within several milliseconds, but also the deep penetration welding effect of vacuum electron beam welding of magnesium alloys will be obtained in a very short period of time.

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