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"Stirling engines Models."
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Numerical investigation of alpha Stirling engine performance based on ideal and actual adiabatic analysis
This article discusses in detail the adiabatic models investigations of alpha Stirling engine with study the influence of performance factors; adiabatic analysis is a crucially effective method because it is close to the real and practical engines when compared to isothermal analysis. The numerical model was created using MATLAB software, an extremely useful tool for solving equations. The study includes two adiabatic analysis models: the ideal model, which considers heat transfer is the duty of the heater and cooler when the regenerator is ideal, and the simple model, which considers the loss and the transfer of heat between the regenerator matrix and the working fluid.
Journal Article
Assessment of a diaphragm thermoacoustic Stirling engine using the energy standpoint and genetic algorithm
This paper presents a novel method to estimate the design parameters of a diaphragm thermoacoustic Stirling engine and investigate the stable limit cycle (sufficient condition) of the engine dynamic using the genetic algorithm and system energy changes. In this regard, first, the parametric equations are extracted by employing both the governing equations of the engine and energy standpoint. Next,
V
c
0
(initial volume of compression space),
R
q
(pneumatic resistance),
V
h
0
(initial volume of expansion space), and hot gas temperature (
T
h
) are taken as the design parameters in this study. Genetic algorithm and parametric equations were then utilized to estimate the chosen design parameters. Next, the sufficient condition of the engine is evaluated based on the estimated design parameters. The simulated outcomes are shown that the sufficient condition is satisfied by the estimated design parameters. Afterward, the simulated results are validated using experimental data gathered from the constructed SUTech-SR-3 engine. Comparing the extracted data eventuates a proper method of estimating design parameters and satisfying the sufficient condition related to the SUTech-SR-3 engine. It is worth noting that in this research, the dynamic of the thermoacoustic Stirling engine has investigated using a mechanical point of view. Also, in this paper, only the dynamic behavior of the engine has been investigated, and the production power and work have not been studied.
Journal Article
Study of Performance of Quantum Stirling Engine Using 2D and 3D Heisenberg Model
In the article, a quantum Stirling machine is proposed and its behavior as a quantum heat engine (QHE) or a refrigerator is investigated. The working substance of the machine is considered as a 2D and 3D spin chain model under a magnetic field and the Dzyaloshinskii-Moriya interaction (DMI). The effects of a magnetic field, the temperature of a cold bath, DMI, and the system dimension have been studied on the efficiency and performance coefficient of the Stirling heat engine and the Stirling refrigerator. It is deduced that with proper selection of the system parameters, and system dimension the Stirling cycle can be operated as a QHE or quantum refrigerator with sufficient efficiency, and performance coefficient. By decreasing the temperature of the cold bath and considering a 3D model without DMI, the system works as a QHE with a maximum efficiency of 33%. Also, by considering a 2D model with DMI and rising the magnetic field, the system works as a quantum refrigerator with a maximum performance coefficient approximately of 7.1. Therefore, we can say that the maximum efficiency or performance coefficient can be obtained by the appropriate selection of system parameters and dimensions.
Journal Article
Effect of Radial Clearance on the Secondary Motion and Tribological Performance of Stirling Engine Piston-Crosshead
The cylinder radial clearance is a significant influencing factor for secondary motion and frictional power consumption of Stirling engine piston-crosshead structure. In this paper, a piston-crosshead dynamical model of the Stirling engine considering the surface tribological characteristics is established, and the correctness of the model is verified on the piston rod sealing test bench. The influence of the clearance on the dynamics and the tribology of the Stirling engine piston-crosshead is analysed based on this model, and it is shown that the crosshead knocking force and the frictional force reach equilibrium when the clearance is 0.06 mm.
Journal Article
A novel approach towards the selection of regenerators for optimal Stirling engine performance based on energy and exergy analyses
Regenerators play a vital role in enhancing the overall performance of Stirling engines. Hence, this paper performed an energy and exergy analysis to elucidate the significance of regenerator characteristics concerning system performance, contributing to the optimal regenerator’s design and selection. The relationship between regenerator structure, regenerator exergy destruction, and output power, thermal efficiency, and exergy efficiency for Stirling engines was established by integrating the thermal model of Stirling engines with a mathematical model of regenerators. In contrast to cross-flow and parallel-flow regenerators, a novel concept of inclined-flow regenerators, featuring a matrix surface inclined in the direction of gas flow, was developed to achieve higher and more balanced engine output power and energy utilization efficiency. A comprehensive investigation was conducted into the effects of matrix structure types and regenerator geometries on the performance of both regenerators and engines. The results reveal that, following structural optimization, Stirling engines equipped with the inclined-flow regenerator demonstrate a substantial 16.6%, 38.3%, and 37.2% increase in power output, thermal efficiency, and exergy efficiency, respectively, compared to those equipped with cross-flow regenerators. In contrast, when compared to engines fitted with parallel-flow regenerators, they experience a 13.5% reduction in power output but achieve remarkable enhancements of 45.4% and 36.7% in thermal and exergy efficiency, respectively. This study introduces new insights into selecting regenerator structures for enhancing the output performance of Stirling engines.
Journal Article
A general stability analysis method for regenerative oscillating heat engines based on heat-dynamics network model and Nyquist criterion
Regenerative oscillating heat engines (ROHEs), such as Stirling and thermoacoustic heat engines, are self-excited oscillating heat engines. In the design and application of these ROHEs, operating stability is of utmost importance. However, general and efficient stability analysis methods for ROHEs are still lacking. The present research focuses on developing a unifying approach for analyzing the stability of ROHEs through heat-dynamics network model and the Nyquist criterion. First, the general heat-dynamics network model as an analytical tool is provided for three typical ROHEs, including the travelling-wave, standing-wave thermoacoustic engine and Stirling engine. Then, based on the features of established network models, these ROHEs are regarded as either feedback or negative-resistance type oscillators, and their startup and stability characteristics are analyzed by combining the Nyquist criterion and PSO method so that the startup information and the limit cycle for these ROHEs are accurately obtained. In the meanwhile, the Nyquist criterion is extended to consider nonlinear effects in this paper. The prototype analyses show that the calculated results for the startup information and the limit cycle are in good agreement with those of the experiment or the related analysis, with a maximum error of 12.64%.
Journal Article
Efficiency at Maximum Power of a Quantum Stirling Heat Engine
In both the classical and quantum fields, the efficiency at maximum power(EMP) of low-dissipation Carnot heat engines has been extensively studied. However, research on low-dissipation Stirling heat engines has never been done before. We use a two-level system as the working substance to construct a non regenerative quantum Stirling heat engine. In the range of low dissipation, we find that controlling the heat exchange of the working substance during the isochoric process can make the EMP upper bound of the Stirling engine exceed that of the Carnot engine. In addition, we also compare the efficiency of the heat engine in the high-temperature region and the low-temperature region in the case of symmetrical dissipation. The results obtained indicate that the heat engine operating in the high temperature region has an advantage over the low temperature region.
Journal Article
Influences of nonlinear parameters on the performance of a free‐piston Stirling engine
This study presents a thermodynamic–dynamic model of a free‐piston Stirling engine (FPSE) with nonlinear coefficients of spring, load damping, and pressure for working spaces. The effects of the nonlinear coefficients of hardening and softening springs on the movement and operating frequency of a displacer and piston are investigated. Subsequently, the influences of the nonlinear pressure terms of the working space and buffer spaces, as well as the nonlinear coefficients of the load on the amplitudes of the two pistons, frequency, and output powers are discussed. The results indicate that the low nonlinear coefficients of the spring have a minor effect on the amplitudes and frequency. As the high nonlinear coefficients of the hardening spring increase, the amplitudes and output power decrease, while the frequency increases. As the nonlinear terms of the softening spring increase, the amplitudes and output power reach maximum values, but the frequency is reduced by 3.55%. The effects of the nonlinear pressure terms on the amplitudes and output power are not evident. However, an increase in the nonlinear load leads to a significant decrease in the FPSE's performance.
Journal Article
A Systematic and Comprehensive Review on 2-D and 3-D Numerical Modelling of Stirling Engine
The present study summarises a comprehensive review of the simulation modelling of the Stirling engine. A Stirling engine, characterized as an external combustion engine, is versatile enough to operate on various fuels, including solar energy and waste heat. Among the different analysis approaches for the Stirling Engine, fourth-order analysis, which is Computational Fluid Dynamics (CFD) analysis, stands out as the sole method that takes into account the actual geometry of the engine. It is capable of identifying intricate gas flow patterns, as well as non-uniform pressure and temperature distributions within the engine. This results in better understanding and optimisation of the design parameters of the engine. The primary goal of this study is to compile and summarize 2D and 3D CFD simulation investigations, categorizing them based on the software employed, including ANSYS Fluent, OpenFOAM, and COMSOL. The focus will be on delineating the study type, computational domain, and the eddy viscosity models utilized for the modeling of Stirling engines. Comparison of various models and their deviation from experimental results is also listed. It was found that considering the radiation model resulted in an improvement of accuracy by 11%. The impinging effect, noted by CFD analysis, is responsible for vortex formation that improved heat transfer, resulting in a discrepancy of over 80% between the prediction of power output by the second-order method and CFD. For accuracy, simulation in full domain 3D is preferred over partial domain 3D and 2D CFD studies. However, it will require more computational resources, accurate 3D model and boundary conditions.
Journal Article