Performance Improvement of a Thermoacoustic Stirling Engine with In-Line Phase-Adjuster

2021 ◽  
pp. 1-14
Author(s):  
Isares Dhuchakallaya ◽  
Patcharin Saechan
Keyword(s):  
Acoustic Field ◽  
Acoustic Impedance ◽  
Heat Engine ◽  
Acoustic Power ◽  
Energy Conversion Efficiency ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Experimental Investigations ◽  
Set Up ◽  
High Level

Abstract This study examined the influence of an in-line phase-adjuster on the energy conversion efficiency of thermoacoustic Stirling heat engine (TASHE). The numerical and experimental investigations were performed. An acoustic field in the system can be adjusted by the phase-adjuster. Therefore, the TASHE could maintain high-level performance at all operating conditions. The phase-adjuster or the telescopic in-line piston was set up at the tail of the resonance tube. The TASHE was modeled by DeltaEC to search the optimal configurations. Due to the variations of acoustic loads or operating conditions from the design criteria, the engine absolutely cannot maintain maximum efficiency. The proposed phase-adjuster could bring back its maximum efficiency by re-matching the acoustic impedance in the regenerator. In the experiments, the self-excited and steady-state temperatures were 480°C and 397°C. The TASHE can provide an acoustic power of up to 40 W. The thermo-to-acoustic efficiency of 12.03%, related to 22.56% of the Carnot efficiency, was achieved. There was a reasonably good agreement between the measured and simulation results. The function of the phase-adjuster in tuning the acoustic impedance was demonstrated experimentally. In the case of the TASHE operated under the off-design conditions, these scenarios would drop the system efficiency. This research can confirm that the phase-adjuster is the component applied to tune the acoustic field in the regenerator accurately with the minimum changes. It could help to improve the efficiency of such consequences.

The Role of Internal Irreversibilities in the Performance and Stability of Power Plant Models Working at Maximum ϵ-Ecological Function

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Gabriel Valencia-Ortega ◽  
Sergio Levario-Medina ◽  
Marco Antonio Barranco-Jiménez
Keyword(s):  
Power Plants ◽  
Heat Engine ◽  
Combined Cycle ◽  
Ecological Function ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Working Fluid ◽  
Engine Model ◽  
Improved Stability ◽  
The Stability

Abstract The proposal of models that account for the irreversibilities within the core engine has been the topic of interest to quantify the useful energy available during its conversion. In this work, we analyze the energetic optimization and stability (local and global) of three power plants, nuclear, combined-cycle, and simple-cycle ones, by means of the Curzon–Ahlborn heat engine model which considers a linear heat transfer law. The internal irreversibilities of the working fluid measured through the r-parameter are associated with the so-called “uncompensated Clausius heat.” In addition, the generalization of the ecological function is used to find operating conditions in three different zones, which allows to carry out a numerical analysis focused on the stability of power plants in each operation zone. We noted that not all power plants reveal stability in all the operation zones when irreversibilities are considered through the r-parameter on real-world power plants. However, an improved stability is shown in the zone limited by the maximum power output and maximum efficiency regimes.

scholarly journals Chart for Thermoelectric Systems Operation Based on a Ternary Diagram for Bithermal Systems

Entropy ◽  
2018 ◽  
Vol 20 (9) ◽  
pp. 666
Author(s):  
Julien Ramousse ◽  
Christophe Goupil
Keyword(s):  
Heat Pump ◽  
Heat Engine ◽  
Ternary Diagram ◽  
Operating Conditions ◽  
Thermal Dissipation ◽  
Maximum Efficiency ◽  
Joule Effect ◽  
Parametric Curve ◽  
Thermoelectric Systems ◽  
The Impact

Thermoelectric system’s operation needs careful attention to ensure optimal power conversion depending on the application aims. As a ternary diagram of bithermal systems allows a synthetic graphical analysis of the performance attainable by any work-heat conversion system, thermoelectric systems operation is plotted as a parametric curve function of the operating conditions (electric current and reservoirs’ temperature), based on the standard model of Ioffe. The threshold of each operating mode (heat engine, heat pump, thermal dissipation, and forced thermal transfer), along with the optimal efficiencies and powers of the heat pump and heat engine modes, are characterized graphically and analytically as a function of the material properties and the operating conditions. The sensibility of the performance aims (maximum efficiency vs. maximum power) with the operating conditions is, thus, highlighted. In addition, the specific contributions of each phenomenon involved in the semiconductor (reversible Seebeck effect, irreversible heat leakage by conduction and irreversible thermal dissipation by Joule effect) are discussed in terms of entropy generation. Finally, the impact of the exo-irreversibilities on the performance is analyzed by taking the external thermal resistances into account.

scholarly journals Experimental Investigations on Tilting Pad Journal Bearings

1999 ◽  
Vol 5 (3) ◽  
pp. 181-191 ◽  
Author(s):  
Renato Brancati ◽  
Stefano Pagano ◽  
Ernesto Rocca ◽  
Michele Russo ◽  
Riccardo Russo
Keyword(s):  
Dynamic Behaviour ◽  
Experimental System ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Rigid Rotor ◽  
Tilting Pad ◽  
Set Up ◽  
The University ◽  
Tilting Pad Journal Bearings

The results of a survey conducted on an experimental system consisting of a rigid rotor supported on two radial bearings each with five tilting pads is presented. In particular, the system was set up in order to assess the dynamic behaviour of the bearing in unusual operating conditions. The response of the bearing to different unbalance values was determined after acquiring and analysing the orbits described by the journal axis for assigned unbalance values in different operating conditions. Analysis of the results shows some particular operating features that were not entirely predicted by the theoretical model and which may give rise to malfunctions in the rotor-tilting pad bearings system. The tests were carried out in the rotor dynamics laboratory of the Dipartimento di Ingegneria Meccanica per l'Energetica at the University of Naples.

Effect of phase adjustment on the acoustic field of a cascade thermoacoustic engine

2017 ◽  
Vol 231 (4) ◽  
pp. 317-327
Author(s):  
Patcharin Saechan ◽  
Isares Dhuchakallaya
Keyword(s):  
Acoustic Field ◽  
Traveling Wave ◽  
Acoustic Impedance ◽  
Acoustic Power ◽  
Phase Region ◽  
Thermoacoustic Engine ◽  
Flow Area ◽  
Resonator Length ◽  
Phase Adjustment ◽  
Tuning Methods

This study set out to explore the influence of phase adjustment on the acoustic field of a cascade thermoacoustic engine. The system consists of one standing wave unit and one traveling wave unit arranged in series. The straight-line configuration allows suppressing a time-averaged mass flow or Gedeon streaming, which causes some unwanted convective heat transport and reduces the efficiency of the system. Theoretically, the regenerator of the traveling wave unit must be operated within the traveling wave phasing and high impedance region in order to achieve an efficient performance. The various techniques of phase adjustment by modifying the configurations and geometrical dimensions of the system are investigated both numerically and experimentally to adjust the position of the sweet spot as well as to achieve the high acoustic impedance in the regenerator. The effective tuning methods with less modification here are accomplished by changing the volume of the down-cavity and reducing the flow area of the down-resonator by inserting the pencil. However, the pencil insertion scheme causes an extra loss due to viscous dissipation that should be taken into account. The change of the down-resonator length has a strong effect on the acoustic field in the system. After the phase-adjustment schemes are completely implemented, the performance of the proposed system is significantly improved, in which the regenerator of the traveling wave unit operates within the traveling wave phase region with high acoustic impedance. This prototype operated with air at atmospheric pressure can supply acoustic power up to 33 W to the down-resonator, which is about 9.5% of Carnot efficiency.

scholarly journals MACROECONOMIC RISKS: CLASSIFIED FEATURES, METHODS OF MEASUREMENT, MITIGATION PATTERNS

2018 ◽  
Vol 4 (4) ◽  
pp. 258-264
Author(s):  
Yurii Paida ◽  
Yaryna Andrushko ◽  
Olena Iliushyk
Keyword(s):  
Future Generation ◽  
High Yield ◽  
Maximum Efficiency ◽  
Practical Implementation ◽  
Human Needs ◽  
Systemic Risks ◽  
Set Up ◽  
High Level ◽  
Entrepreneurial Activities ◽  
Macroeconomic Risks

The article deals with the essence, factors, and patterns of macroeconomic risks mitigation. The purpose of the paper is to summarize and present a classification of systemic risks, to analyse principles and methods of macroeconomic risks evaluation. The methodological basis of the study is general scientific and special methods of cognition. The most extended analysis of systemic risks not only from the perspective of geographical and historical aspects but also in the context of modern economic processes is carried out. Results of the research prove that in the context of formation of a new economy of Ukraine and approval of the practice of timely prevention and mitigation of macroeconomic risks in accordance with imperative of modern time, it is necessary to: 1) give real state priority to the most advanced educational technologies. While providing maximum broad and equal access of youth to education, we should have the program for search and practical support of national intelligence phenomena in place; 2) create conditions for rehabilitation and advanced development of innovative directions of applied and, first and utmost, polytechnic sciences. It is the task of the state to ensure their financial support and direct employment at enterprises. All-round support of introduction of high-yield venture developments into the production; 3) secure efficient state protection of intellectual property, create legislatively the conditions for commercial usage of innovative achievements within the country; 4) encourage with maximum efficiency return of high-level engineers and blue-collar workers to the technological area; breathe new life into the system of professional and technical schools where information and programming professions prevail and which graduators would be engaged with priority into operations in unique productions; 5) create modern information market, allround support of introduction of a unified information field. Learning and striving to satisfy human needs without placing systemic risks on future generation being on the Earth should become the core principle of a civilizational development. Value/originality. We may lay down an essential principle of civilizational regulation of systemic risks when each state, specifically the international community, should set up (subject to all complexities of practical implementation) regulating constants, rules, and bans of such contents and in such direction to have business or entrepreneurial activities carried out ultimately in the risk-related mode, which would cause no detrimental effect on the economy as whole.

scholarly journals Accuracy Analysis of the Measurement of Centre of Gravity and Moment of Inertia with a Swing

2021 ◽  
Vol 11 (12) ◽  
pp. 5345
Author(s):  
Roman Gabl ◽  
Thomas Davey ◽  
Edd Nixon ◽  
David M. Ingram
Keyword(s):  
Early Stage ◽  
High Accuracy ◽  
Moment Of Inertia ◽  
Experimental Investigations ◽  
Scaled Model ◽  
Centre Of Gravity ◽  
Building Process ◽  
Set Up ◽  
High Level ◽  
Motion Capturing

Floating devices under wave and current loads are typically designed based on numerical methods followed by a validation with experimental investigations. This allows an independent check due to the comparison of two different modelling approaches based on different assumptions. At an early stage of the project, numerical simulations are based on theoretical (ideal) values of the centre of gravity (CG) and moment of inertia (MI). The building process of a scaled model results very often in a requested simplification of certain parts, which can influence the CG and also the MI of the scaled model. Knowing those discrepancies allows us to improve the comparability of both approaches but the measurement of those values is connected with either a higher uncertainty or a high level of effort. A significant improvement of such measurements can be reached by the deployment of a specific experimental set-up. This paper presents the classification of the newly designed swing with a high accuracy inertial inclinometer, which was verified by the marker-based motion capturing system. The achieved experiences are useful for the future use of the set-up as well as similar investigations. The comparison with the theoretical values for the swing as well as an example model showed very good agreements and a high accuracy of few millimetres for the CG and an error smaller 1% for MI.

Onchocerciasis in Osse, Ondo State, Nigeria: Effectiveness of Motivational Strategies in Sustaining Compliance with Community Ivermectin Therapy

2002 ◽  
Vol 21 (2) ◽  
pp. 177-189
Author(s):  
O. U. Manafa ◽  
T. S. Awolola ◽  
A. N. Isamah
Keyword(s):  
Community Intervention ◽  
Intervention Group ◽  
Control Group ◽  
Group Discussions ◽  
Participant Satisfaction ◽  
Attitudes And Practices ◽  
Ondo State ◽  
Set Up ◽  
High Level ◽  
Knowledge Attitudes And Practices

A study in human Onchocerciasis was undertaken in four endemic communities in Ondo State, Nigeria. In-depth interviews were conducted on peoples' knowledge, attitudes, and practices regarding Onchocerciasis aetiology, treatment, prevention, and symptoms. These were complemented by key informant interviews and focus group discussions. Based on this information, an educational program was set up which included the training of selected villagers (motivators) and community intervention organized by these motivators. Evaluation used a control group where intervention was focused on other health problems in the area. Onchocerciasis education took place only with the intervention group. At the start of the project, peoples' knowledge about Onchocerciasis, its cause, treatment, prevention, and symptoms were varied and only a small proportion could link the bite of the blackfly to Onchocerciasis. The educational intervention achieved a high level of participant satisfaction which was expressed in continuous attendance at workshops and keeping appointments with motivators. The intervention helped to bring a significant improvement in the knowledge, attitudes, and practices (KAP) of the respondents. The knowledge of Onchocerciasis aetiology increased to 79.8 percent, 71.5 percent, and 74 percent from 48.5 percent, 48.7 percent, 34 percent, and 45 percent pre-intervention in the four study areas used. The project demonstrated that a community-based health education can be effective in Onchocerciasis control.

scholarly journals Developing a BIM-Based MUVR Treadmill System for Architectural Design Review and Collaboration

2021 ◽  
Vol 11 (15) ◽  
pp. 6881
Author(s):  
Calvin Chung Wai Keung ◽  
Jung In Kim ◽  
Qiao Min Ong
Keyword(s):  
Architectural Design ◽  
Human Locomotion ◽  
Virtual Space ◽  
Design Stage ◽  
Design Review ◽  
Team Members ◽  
Physical Constraints ◽  
Simulated Environment ◽  
Set Up ◽  
High Level

Virtual reality (VR) is quickly becoming the medium of choice for various architecture, engineering, and construction applications, such as design visualization, construction planning, and safety training. In particular, this technology offers an immersive experience to enhance the way architects review their design with team members. Traditionally, VR has used a desktop PC or workstation setup inside a room, yielding the risk of two users bump into each other while using multiuser VR (MUVR) applications. MUVR offers shared experiences that disrupt the conventional single-user VR setup, where multiple users can communicate and interact in the same virtual space, providing more realistic scenarios for architects in the design stage. However, this shared virtual environment introduces challenges regarding limited human locomotion and interactions, due to physical constraints of normal room spaces. This study thus presented a system framework that integrates MUVR applications into omnidirectional treadmills. The treadmills allow users an immersive walking experience in the simulated environment, without space constraints or hurt potentialities. A prototype was set up and tested in several scenarios by practitioners and students. The validated MUVR treadmill system aims to promote high-level immersion in architectural design review and collaboration.

scholarly journals A Novel Hybrid LDC Converter Topology for the Integrated On-Board Charger of Electric Vehicles

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3603
Author(s):  
Vu-Hai Nam ◽  
Duong-Van Tinh ◽  
Woojin Choi
Keyword(s):  
Low Voltage ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Battery Charger ◽  
Forward Converter ◽  
Vehicle To Grid ◽  
Circulating Current ◽  
In Series ◽  
Converter Topology ◽  
Output Capacitor

Recently, the integrated On-Board Charger (OBC) combining an OBC converter with a Low-Voltage DC/DC Converter (LDC) has been considered to reduce the size, weight and cost of DC-DC converters in the EV system. This paper proposes a new integrated OBC converter with V2G (Vehicle-to-Grid) and auxiliary battery charge functions. In the proposed integrated OBC converter, the OBC converter is composed of a bidirectional full-bridge converter with an active clamp circuit and a hybrid LDC converter with a Phase-Shift Full-Bridge (PSFB) converter and a forward converter. ZVS for all primary switches and nearly ZCS for the lagging switches can be achieved for all the operating conditions. In the secondary side of the proposed LDC converter, an additional circuit composed of a capacitor and two diodes is employed to clamp the oscillation voltage across rectifier diodes and to eliminate the circulating current. Since the output capacitor of the forward converter is connected in series with the output capacitor of the auxiliary battery charger, the energy from the propulsion battery can be delivered to the auxiliary battery during the freewheeling interval and it helps reduce the current ripple of the output inductor, leading to a smaller volume of the output inductor. A 1 kW prototype converter is implemented to verify the performance of the proposed topology. The maximum efficiency of the proposed converter achieved by the experiments is 96%.

scholarly journals A 2-D model for Intermediate Temperature Solid Oxide Fuel Cells Preliminarily Validated on Local Values

Catalysts ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 36 ◽  
Author(s):  
Bruno Conti ◽  
Barbara Bosio ◽  
Stephen John McPhail ◽  
Francesca Santoni ◽  
Davide Pumiglia ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Intermediate Temperature ◽  
Physical Parameters ◽  
Local Concentration ◽  
Oxide Fuel ◽  
Molten Carbonate ◽  
Experimental Apparatus ◽  
Set Up

Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) technology offers interesting opportunities in the panorama of a larger penetration of renewable and distributed power generation, namely high electrical efficiency at manageable scales for both remote and industrial applications. In order to optimize the performance and the operating conditions of such a pre-commercial technology, an effective synergy between experimentation and simulation is fundamental. For this purpose, starting from the SIMFC (SIMulation of Fuel Cells) code set-up and successfully validated for Molten Carbonate Fuel Cells, a new version of the code has been developed for IT-SOFCs. The new release of the code allows the calculation of the maps of the main electrical, chemical, and physical parameters on the cell plane of planar IT-SOFCs fed in co-flow. A semi-empirical kinetic formulation has been set-up, identifying the related parameters thanks to a devoted series of experiments, and integrated in SIMFC. Thanks to a multi-sampling innovative experimental apparatus the simultaneous measurement of temperature and gas composition on the cell plane was possible, so that a preliminary validation of the model on local values was carried out. A good agreement between experimental and simulated data was achieved in terms of cell voltages and local temperatures, but also, for the first time, in terms of local concentration on the cell plane, encouraging further developments. This numerical tool is proposed for a better interpretation of the phenomena occurring in IT-SOFCs and a consequential optimization of their performance.

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