scholarly journals Beta Type Stirling Engine. Schmidt and Finite Physical Dimensions Thermodynamics Methods Faced to Experiments

Entropy ◽  
2020 ◽  
Vol 22 (11) ◽  
pp. 1278
Author(s):  
Cătălina Dobre ◽  
Lavinia Grosu ◽  
Monica Costea ◽  
Mihaela Constantin
Keyword(s):  
Experimental Tests ◽  
Stirling Engine ◽  
Analytical Models ◽  
Maximum Pressure ◽  
Heat Sources ◽  
Type Machine ◽  
Thermodynamic Coupling ◽  
Energy Processes ◽  
Theoretical Results ◽  
Engine Cycle

The paper presents experimental tests and theoretical studies of a Stirling engine cycle applied to a β-type machine. The finite physical dimension thermodynamics (FPDT) method and 0D modeling by the imperfectly regenerated Schmidt model are used to develop analytical models for the Stirling engine cycle. The purpose of this study is to show that two simple models that take into account only the irreversibility due to temperature difference in the heat exchangers and imperfect regeneration are able to indicate engine behavior. The share of energy loss for each is determined using these two models as well as the experimental results of a particular engine. The energies exchanged by the working gas are expressed according to the practical parameters, which are necessary for the engineer during the entire project, namely the maximum pressure, the maximum volume, the compression ratio, the temperature of the heat sources, etc. The numerical model allows for evaluation of the energy processes according to the angle of the crankshaft (kinematic–thermodynamic coupling). The theoretical results are compared with the experimental research. The effect of the engine rotation speed on the power and efficiency of the actual operating machine is highlighted. The two methods show a similar variation in performance, although heat loss due to imperfect regeneration is evaluated differently.

scholarly journals Light-assisted electrospinning monitoring for soft polymeric nanofibers

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Dario Lunni ◽  
Goffredo Giordano ◽  
Francesca Pignatelli ◽  
Carlo Filippeschi ◽  
Stefano Linari ◽  
...  
Keyword(s):  
Real Time ◽  
Electrospun Fiber ◽  
Correlation Coefficients ◽  
Experimental Tests ◽  
Electrospinning Process ◽  
Analytical Models ◽  
Diameter Distribution ◽  
Soft Systems ◽  
Light Coupling ◽  
Waveguide Length

Abstract A real-time tool to monitor the electrospinning process is fundamental to improve the reproducibility and quality of the resulting nanofibers. Hereby, a novel optical system integrated through coaxial needle is proposed as monitoring tool for electrospinning process. An optical fiber (OF) is inserted in the inner needle, while the external needle is used to feed the polymeric solution (PEO/water) drawn by the process. The light exiting the OF passes through the solution drop at the needle tip and gets coupled to the electrospun fiber (EF) while travelling towards the nanofibers collector. Numerical and analytical models were developed to assess the feasibility and robustness of the light coupling. Experimental tests demonstrated the influence of the process parameters on the EF waveguide properties, in terms of waveguide length (L), and on the nanofibers diameter distribution, in terms of mean $$\widehat{D}$$ D ^ and normalized standard deviation $$\chi$$ χ . Data analysis reveals good correlation between L and $$\widehat{D}, \chi$$ D ^ , χ (respectively maximum correlation coefficients of $${\rho }_{L,\widehat{D}}$$ ρ L , D ^ = 0.88 and $${\rho }_{L,\chi }$$ ρ L , χ = 0.84), demonstrating the potential for effectively using the proposed light-assisted technology as real-time visual feedback on the process. The developed system can provide an interesting option for monitoring industrial electrospinning systems using multi- or moving needles with impact in the scaling-up of innovative nanofibers for soft systems.

A New Concept of Externally Heated Engine—Comparisons with the Stirling Engine

1996 ◽  
Vol 210 (5) ◽  
pp. 363-371 ◽  
Author(s):  
L Brzeski ◽  
Z Kazimierski
Keyword(s):  
Low Power ◽  
Power Density ◽  
Internal Combustion Engines ◽  
Thermodynamic Cycle ◽  
Rotational Frequency ◽  
Stirling Engine ◽  
Maximum Pressure ◽  
Combustion Engines ◽  
Working Medium ◽  
Engine Cylinder

This paper presents a new concept of the externally heated valve (EHV) engine. Air can be used as a working medium in the closed cycle of this engine. Heat delivered to the working air can come from a combustion chamber or another heat generator of an arbitrary type. The engine construction and the thermodynamic cycle performed by it are original and entirely different from the well-known Stirling engine. The main disadvantage of the Stirling engine is its low power density, that is the low power obtained per litre of the engine cylinder volume. In the case of the engine presented here it is possible to achieve power density and efficiency similar to those typical of advanced internal combustion engines. Comparisons between the power of the Stirling engine and the power of the new engine have been performed for the same engine capacity, rotational frequency and maximum and minimum temperatures of the cycle. At the same minimum pressure of the working gas in both engines, the power of the EHV engine is several times higher than that of the Stirling engine, while, on the other hand, at the same maximum pressure of the working gas in both engines, the power of the EHV engine is 20 per cent higher than that of the Stirling engine power. The efficiencies of both engines do not differ significantly from each other.

An Adaptive PI/Sliding Mode Controller for a Speed Drive

1989 ◽  
Vol 111 (3) ◽  
pp. 409-415 ◽  
Author(s):  
R. M. DeSantis
Keyword(s):  
Performance Improvement ◽  
Sliding Mode ◽  
Experimental Tests ◽  
Industrial Applications ◽  
Open Loop ◽  
Sliding Mode Controller ◽  
Switching Element ◽  
Parallel Addition ◽  
Self Tuning ◽  
Theoretical Results

A classical PI speed drive controller modified with the parallel addition of an on-off switching element appears to offer a potential for reasonable improvement over the performance of the original version. This improvement is obtained by combining classical transfer function techniques, sliding mode systems ideas, and self-tuning. While theoretical results, extended simulations, and preliminary experimental tests are encouraging, they do suggest that in actual industrial applications performance improvement may be conditioned by the usage of better performing open loop components.

Using noise control principles when evaluating the acoustic impacts of face coverings during the coronavirus pandemic

2021 ◽  
Vol 263 (3) ◽  
pp. 3554-3561
Author(s):  
Richard Ruhala ◽  
Laura Ruhala
Keyword(s):  
Classroom Environment ◽  
Noise Control ◽  
Experimental Tests ◽  
Analytical Models ◽  
Octave Band ◽  
Interference Level ◽  
Cavity Resonances ◽  
The Face ◽  
Clear Plastic ◽  
Stiffness And Damping

Several different combinations of face masks and shields are evaluated for their acoustic performance using a head and torso simulator (HATS). The HATS is used as a controlled and repeatable artificial sound source using white noise in a classroom environment. Sound pressure levels at octave band frequencies due to the face coverings are evaluated at a location of 2.0 meters from the HATS which is within the direct field to reduce the room acoustical effects. The problem is modeled as a barrier separating a source and receiver using fundamental noise control principles. Fabric material properties are used such as thickness, density, stiffness, and damping. The results are compared with experimental tests. The face shield with clear plastic barrier produces a resonance in the 1000 Hz octave band. Analytical models of cavity resonances, standing wave resonances, or plate resonances are calculated and compared with the experimental resonance. The speech interference level is used to determine the frequency content that is most likely to cause hearing difficulties and compared with A-weighted differences between the unmasked condition and masked.

Analysis of the thermal variations in a moving pantograph strip using an electro-thermal simulation tool and validating by experimental tests

2019 ◽  
Vol 234 (8) ◽  
pp. 859-868
Author(s):  
Nicolas Delcey ◽  
Philippe Baucour ◽  
Didier Chamagne ◽  
Geneviève Wimmer ◽  
Giuseppe Bucca ◽  
...  
Keyword(s):  
Test Bench ◽  
Electrical Power ◽  
Computation Time ◽  
Experimental Tests ◽  
Simulation Tool ◽  
Heat Sources ◽  
Train Operation ◽  
Catenary System ◽  
Experimental Values ◽  
Physical Phenomena

The performance of the pantograph–catenary system is very significant in supplying reliable electrical power for the operation of trains. Many problems arise due to the increase in temperature inside the pantograph strip. More research works have been done to study the temperature extrema of the system but it is quite difficult to obtain the experimental values during a real-time train operation. Moreover, performing experimental tests needs a representative test bench of the system or a real train. This is challenging owing to the time and availability of materials and taking into account the number of physical phenomena to control and measure. To address this problem, the authors of this study present an electro-thermal modeling tool. The heat sources which characterize the system are analyzed to generate a heat equation formulation. This equation is solved with the finite differences numerical method in order to obtain the temperature distribution in the pantograph strip. In addition, some specifications such as computation time or required memory are taken into account. More precisely, mathematical and numerical optimizations are proposed to improve these specifications. The tool is validated by comparing the simulated results with the experimental tests obtained from a test bench located at POLIMI (Polytechnico Di Milano, Milan). Finally, thermal interpretations as well as relative gap analyses are done in different situations.

Magnetorheological damper behaviour in accordance with flow mode

2018 ◽  
Vol 84 (2) ◽  
pp. 21101
Author(s):  
Joanes Berasategui ◽  
Ainara Gomez ◽  
Manex Martinez-Agirre ◽  
Maria Jesus Elejabarrieta ◽  
M. Mounir Bou-Ali
Keyword(s):  
Rheological Behaviour ◽  
Mr Damper ◽  
Experimental Tests ◽  
Magnetorheological Damper ◽  
Flow Mode ◽  
Main Design ◽  
Mr Dampers ◽  
Significant Parameter ◽  
Optimal Flow ◽  
Theoretical Results

The objective of this article is to determine the optimal flow mode in an MR damper to maximize its performance. Flow mode is one of the main design issues in an MR damper, as it determines the velocity profile and the pressure drop across the gap. In this research, two MR dampers were designed and manufactured with two flow modes: valve and mixed. The response of these two dampers was compared experimentally. Additionally, the experimental tests were correlated by theoretical results that were obtained considering the rheological behaviour of the MR fluid, the shear stress distribution in the gap, and the damper movement. Interestingly, the obtained results suggest that flow mode is not a significant parameter for determining the behaviour of a MR damper.

Motorcycle Analytical Modeling Including Tire–Wheel Nonuniformities for Ride Comfort Analysis

2017 ◽  
Vol 45 (2) ◽  
pp. 101-120 ◽  
Author(s):  
Matheus de B. Vallim ◽  
José M. C. Dos Santos ◽  
Argemiro L. A. Costa
Keyword(s):  
Degrees Of Freedom ◽  
Analytical Modeling ◽  
Ride Comfort ◽  
Experimental Tests ◽  
Rotational Frequency ◽  
Analytical Models ◽  
Vertical Force ◽  
Lumped Mass ◽  
Multi Body ◽  
4 Degrees Of Freedom

ABSTRACT The transmission of vibrations in motorcycles and their perception by the passengers are fundamental in comfort analysis. Tire nonuniformities can generate self-excitations at the rotational frequency of the wheel and contribute to the ride vibration environment. In this work a multi-body motorcycle model is built to evaluate the ride comfort with respect to tire nonuniformities. The aim is to obtain a multi–degrees-of-freedom dynamic model that includes both the contributions of the motorcycle and tire–wheel assembly structures. This representation allows the tire nonuniformities to predict the vertical force variations on the motorcycle and can be used through a root mean square acceleration evaluation for ride comfort analysis. The motorcycle model proposed is a 10-degrees-of-freedom system, where each tire–wheel is a 4-degrees-of-freedom model. The tire–wheel assemblies include two types of nonuniformities: lumped mass imbalance and radial run-out. Simulations of analytical models are compared with experimental tests.

Design of CNG Tank Supports on Vehicle for Crash Test Simulation

2008 ◽  
Author(s):  
M. Asadi Garmaroudi ◽  
J. Mosayebi ◽  
F. Hojabri
Keyword(s):  
Vertical Direction ◽  
Experimental Tests ◽  
Longitudinal Direction ◽  
Crash Test ◽  
Design Domain ◽  
Structural Members ◽  
Standard Size ◽  
Automotive Body ◽  
Geometrical Shapes ◽  
Theoretical Results

Typical structural members in the automotive body have complex geometrical shapes and no standard size. Thus, generating crash behavior database for all possible dimensions of even single shape is an extremely expensive task. A remedy is to generate databases containing relatively few sizes of the structural members, then employ different methods to approximate the behavior of the structural members over the complete design domain of the dimensions. This paper simulates the behavior of the CNG tank and structural members to crash conditions by using Finite Element Method. According to standard ISO15500, these conditions are acceleration with: i)± 20g longitudinal direction, ii) ± 8g side direction and iii) 4.5g vertical direction [1]. Then, experimental tests were done to validate theoretical results.

Thermosyphon Models for Downhole Heat Exchanger Applications in Shallow Geothermal Systems

1978 ◽  
Vol 100 (4) ◽  
pp. 713-719 ◽  
Author(s):  
D. B. Kreitlow ◽  
G. M. Reistad ◽  
C. R. Miles ◽  
G. G. Culver
Keyword(s):  
Heat Exchanger ◽  
Analytical Models ◽  
Geothermal Systems ◽  
Flow Rates ◽  
Estimated Parameters ◽  
Design Variables ◽  
Circulation Mechanism ◽  
Geothermal Wells ◽  
Experimental Values ◽  
Theoretical Results

The analysis of downhole heat exchangers used to extract energy from relatively shallow geothermal wells leads to the consideration of several interesting problems of buoyancy-driven heat transfer in enclosures. This paper considers thermosyphoning through and around the wellbore casing which is perforated at two or more depths. Analytical models are developed for thermosyphoning in the cased well both with and without a heat exchanger installed. Theoretical results are compared with experimental values. These comparisons show that the observed energy extraction rates and flow rates through the well casing are possible with thermosyphoning as the only circulation mechanism within the well bore. The model with a heat exchanger installed is parametrically evaluated to illustrate the sensitivity of the model to estimated parameters and the effect of changes in design variables or constraints.

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