Stirling Engine Research Articles

High power Stirling Engine with low temperature difference for education using 3D printers

High power Stirling Engine with low temperature difference for education using 3D printers

The Application of Thermomechanical Dynamics (TMD) to Thermoelectric Energy Generation by Employing a Low Temperature Stirling Engine

The Application of Thermomechanical Dynamics (TMD) to Thermoelectric Energy Generation by Employing a Low Temperature Stirling Engine

Performance evaluation of gamma-type Stirling engine using combined Schmidt and mechanical loss model

This paper focuses on the study of gamma-type Stirling engine prototype using a combined Schmidt closed-form and mechanical loss analysis. Not restricted to optimizing the indicated power as classic Schmidt theory is set to, this analysis allows to maximize the shaft power due to the mechanical loss in power transmission. For this purpose, MATLAB code was developed to calculate the indicated and the shaft powers of the engine at different operating parameters. The results showed that shaft power peaks at swept volume ratios smaller than those of indicated power at different values of mechanism effectiveness. Within the range of engine mechanism effectiveness typically between 0.7 and 0.9, it was found that maximum shaft power for this particular engine can be achieved at different optimum values of swept volume ratio between 0.75 and 0.95 and phase angle between 80° and 90°. However, an optimum swept volume ratio was found to be <i>k</i>=0.55 of the same engine size for different scenarios of operation. Also, the developed model can be used as a design tool in the preliminary stage to find the optimum geometry of the engine. The new engine design parameters including the stroke, the crank radius and power piston bore, and engine alteration were presented.

Design and Optimization of a Single-Phase Tubular Linear Oscillating Permanent Magnet Machine for Stirling Generator

Design and Optimization of a Single-Phase Tubular Linear Oscillating Permanent Magnet Machine for Stirling Generator

The thermal and stored heat energy driving a Stirling engine for power generation

South Africa’s national power grid is currently in dire straits. The lack of a dependable power supplier and rising electricity costs force the public and businesses to look for alternatives to meet their energy needs. These alternatives are costly to implement and beyond the financial reach of most South Africans. The most common alternative energy source is solar photovoltaic systems with large battery banks to survive Eskom's long, regular load-shedding schedules. This research aims to design and simulate a combined solar-thermal and stored heat energy-powered Stirling engine for power generation. The output of the research simulation was compared to a standard photovoltaic installation of similar power output. The results for this paper were generated from the simulation software package MATLAB. Such a system must have a lower capital cost to compete with solar photovoltaic systems with battery backup. The Stirling system was found to be cheaper than the deep-cycle gel system and about 11% cheaper than the PV system using lithium iron phosphate.

Investigating the onset and steady-state conditions of a diaphragm thermoacoustic stirling engine

This work investigates the onset and steady-state conditions of diaphragm thermoacoustic Stirling engines using the averaging-based Lyapunov technique for the first time. First, the diaphragm thermoacoustic Stirling engine is introduced. Next, the startup conditions, including the onset condition and existence of a stable limit cycle (steady-state) of the engine are studied based on the alteration of the mass connected to the diaphragm of SUTech-SR-3 in the range of 88.2 g to 121.2 g. The simulation results obtained from the averaging-based Lyapunov technique show the engine can run only in the mass range of 90.4 g to 119 g. On the other hand, to validate the simulation outcomes, this assessment is carried out experimentally. The practical results confirm the extracted outcomes from this method. Based on the allowable range acquired from this technique, the effect of the change in the value of the mass connected to the engine diaphragm on the operating frequency is investigated experimentally. This work shows that the employed method can be a helpful means to investigate the startup conditions of the diaphragm thermoacoustic Stirling engines.

Development of a Simple Stirling Engine Demonstration Tool on the Subject of Thermodynamics

Purpose of the study: The aim of this research is to develop a simple Stirling engine teaching aid for the class XI thermodynamics subject at high school and determine students' responses to the teaching aid developed.
 Methodology: The research method used is research and development (R&D) ADDIE model, namely with the stages of analysis, design, development, implementation, evaluation. The instruments used in this research were media expert validation questionnaires, material expert validation, small group trials and field trials with a Likert scale. The data obtained was then analyzed quantitatively and qualitatively. The test subjects in this research were carried out using small group trials of 10 students and field trials of 30 students from three schools.
 Main Findings: Based on the results of the material expert validation analysis and media expert validation, an average of 86.5% was obtained which could be categorized as very good, then for small group trials it was obtained 91.9% and 93.1% of field trials could be categorized as very good, so that the media for simple Stirling engine teaching aids were has been developed as a whole very well to be used as a teaching aid in learning in class XI High School.
 Novelty/Originality of this study: The novelty of developing a simple Stirling engine demonstration tool for the study of thermodynamics lies in its innovative approach to making a complex subject accessible, engaging, and applicable to a wide range of learners, thereby fostering a deeper understanding and appreciation of the field.

Stirling engines: Advancements, applications, and environmental benefits

The increasing adoption of Stirling engines in contemporary industries is driven by their potential to address critical issues of energy efficiency and emissions reduction. Stirling engines offer higher energy efficiency, lower noise and emissions, and versatility in utilizing various heat sources, making them a promising solution for enhancing environmental preservation and energy diversity. This paper examines the growing adoption of Stirling engines in diverse industries, driven by the urgent need to address energy efficiency and emissions challenges. The paper outlines the core principles and advantages of Stirling engines, highlighting their potential to enhance energy efficiency, preserve the environment, and diversify energy sources. Furthermore, the paper underscores significant industrial and aviation applications of Stirling engines, particularly in vehicle propulsion, heat pumps, and electricity generation. Notably, the automotive Stirling engine excels in fuel efficiency and emissions reduction, offering a viable alternative to traditional internal combustion engines. Stirling engines also prove effective in heat pump systems, contributing to efficient building heating and cooling. In conclusion, despite challenges such as material requirements and heat loss, Stirling engines hold great promise as sustainable and eco-friendly thermal engines. As global concerns regarding energy and the environment intensify, Stirling engines offer a compelling pathway to improved energy efficiency, reduced emissions, and a more diversified energy landscape, driving innovation across sectors.

Synchronization approach to achieving maximum power and thermal efficiency for weakly coupled low-temperature-differential Stirling engines

Synchronization approach to achieving maximum power and thermal efficiency for weakly coupled low-temperature-differential Stirling engines

A novel approach towards the selection of regenerators for optimal Stirling engine performance based on energy and exergy analyses

A novel approach towards the selection of regenerators for optimal Stirling engine performance based on energy and exergy analyses

Temperature-Enhanced Exciton Emission from GaAs Cone-Shell Quantum Dots.

The temperature-dependent intensities of the exciton (X) and biexciton (XX) peaks from single GaAs cone-shell quantum dots (QDs) are studied with micro photoluminescence (PL) at varied excitation power and QD size. The QDs are fabricated by filling self-assembled nanoholes, which are drilled in an AlGaAs barrier by local droplet etching (LDE) during molecular beam epitaxy (MBE). This method allows the fabrication of strain-free QDs with sizes precisely controlled by the amount of material deposited for hole filling. Starting from the base temperature T = 3.2 K of the cryostat, single-dot PL measurements demonstrate a strong enhancement of the exciton emission up to a factor of five with increasing T. Both the maximum exciton intensity and the temperature Tx,max of the maximum intensity depend on excitation power and dot size. At an elevated excitation power, Tx,max becomes larger than 30 K. This allows an operation using an inexpensive and compact Stirling cryocooler. Above Tx,max, the exciton intensity decreases strongly until it disappears. The experimental data are quantitatively reproduced by a model which considers the competing processes of exciton generation, annihilation, and recombination. Exciton generation in the QDs is achieved by the sum of direct excitation in the dot, plus additional bulk excitons diffusing from the barrier layers into the dot. The thermally driven bulk-exciton diffusion from the barriers causes the temperature enhancement of the exciton emission. Above Tx,max, the intensity decreases due to exciton annihilation processes. In comparison to the exciton, the biexciton intensity shows only very weak enhancement, which is attributed to more efficient annihilation processes.

Evaluating the onset conditions of a thermoacoustic Stirling engine loaded with an audio loudspeaker

This paper aims to evaluate the onset conditions of a thermoacoustic Stirling engine loaded with a commercially available audio loudspeaker. The thermoacoustic engine converts supplied heat power into mechanical power in the form of sound, without any mechanical moving parts. The simplicity of the acoustical heat engine holds great promise for high reliability and low cost. By utilizing a readily available electromagnetic device, the engine can serve as a durable solution for practical applications. In this study, we assembled a commercially available moving-coil loudspeaker as a low-cost linear alternator for the thermoacoustic Stirling engine, enabling electric generation from supplied heat. We modeled the loudspeaker using linear control equations and experimentally calibrated its acoustic impedances to estimate the acoustic load. For the part of the thermoacoustic engine, we estimated its acoustic characteristics within the framework of the linear thermoacoustic theory. By solving the characteristic equation resulting from the engine loaded with the audio speaker, we estimated the operational point of self-sustained oscillations excited by the coupling of the loudspeaker and the thermoacoustic engine system. To validate the estimations, we tested a prototype of the combined system, comprising the loudspeaker and the thermoacoustic engine. The results highlight the necessity of precise calibration and accounting for complex geometries within the acoustic load for accurate theoretical estimations, especially when incorporating a commercially available loudspeaker into a thermoacoustic engine.

Harnessing Viscoelasticity to Suppress Irreversibility Buildup in a Colloidal Stirling Engine.

Typically, the rate at which a heat engine can produce useful work is constrained by the buildup of irreversibility with increasing operating speed. Here, using a recently developed reservoir engineering technique, we designed and quantified the performance of a colloidal Stirling engine operating in a viscoelastic bath. While the bath acts like a viscous fluid in the quasistatic limit, and the engine's performance agrees with equilibrium predictions, on reducing the cycle time to the bath's structural relaxation time, the increasingly elastic response of the bath aids suppress the buildup of irreversibility. We show that the elastic energy stored during the isothermal compression step of the Stirling cycle facilitates quick equilibration in the isothermal expansion step. This results in equilibriumlike efficiencies even for cycle times shorter than the equilibration time of the colloidal particle.

Theoretical and experimental study of free piston Stirling generator for high cold end temperatures

The cold end temperature of the free piston Stirling generator (FPSG) should be increased to reduce the heat sink radiator area for space application. A comprehensive model coupled with thermodynamics, dynamics, and electromagnetism was built and solved numerically to investigate the intrinsic relationship between cold end temperature and FPSG performance. It shows that, with fixed heating power, as the cold end temperature increases, the magnetic field strength of alternator air gap decreases. The output power and efficiency show a steadily declining trend. A 100W prototype was tested for model verification. The relative error between experiment and model prediction of the amplitude of piston and displacer is 2.48 % and 11.97 % respectively. For phase difference between piston and displacer, thermal efficiency, and working frequency, the relative error is 54.32 %, 27.23 %, and 2.39 % respectively. When the cold end temperature rises from 320.5K to 394K, the output power and efficiency relative error is 26.06 %∼37.85 % and 27.67 %∼34.24 % respectively. The predicted parameter effect trend is well consistent with experiment, showing the important guiding role for generator optimization operating at high temperatures. The exergy analysis shows that increasing cold end temperature causes input exergy decline and aggravates exergy loss, which is main cause of generator performance degradation.

Environmental Impact Analysis of Residential Energy Solutions in Latvian Single-Family Houses: A Lifecycle Perspective

This study aims to compare the technological solutions that can contribute to more sustainable energy use in the residential sector. Specifically, the goal of the study is to evaluate the environmental impact of different energy (heat and electricity) supply technologies applicable for an average size single-family building in Latvia, a country known for climatic condition characterized by cold winters with frequent snowfall. The study applies the lifecycle assessment methodology of ISO 14040 and the impact assessment method known as ReCiPe 2016 v1.1, which has not been used before for the scope addressed in the study in the context of single-family building energy supply technologies for climatic conditions in Latvia. Thus, the results of the study will provide new information for more sustainable energy solutions in this area of study. The technologies included in the defined scenarios are conventional boiler, electricity from the grid, Stirling engine, and solar photovoltaics (PV). The results of the lifecycle impact assessment for damage categories revealed that all scenarios have a high impact on human health due to fine particulate matter formation followed by global warming. Regarding the damage to the ecosystem, the terrestrial ecotoxicity category has highest impact, followed by global warming. Sensitivity analyses affirmed the model’s validity and also showed that the impacts of conventional systems were most sensitive to changes in electricity consumption, and therefore, the scenarios with electricity supply from a Stirling engine or PV can be considered a more robust solution under changing electricity demands from an environmental perspective.

Enhancing alpha solar stirling engine performance with regenerator

Nowadays, as traditional fossil energy sources are in decline, renewable energy sources are being actively sought, and the use of renewable energy is receiving widespread attention. The Dish engine solar power plant is vital in using solar energy. The Stirling engine is the fundamental element of the power plant, responsible for energy conversion. And the internal regenerator has an essential influence on the engine's performance. Hence, this paper focuses on the analysis and improvement of the regenerator. Heat transportation determines its efficiency, while the regenerator is the core component. An efficient Stirling engine cannot occur without a high-quality regenerator. This paper uses simulation experiments to explore the impact of various materials on the regenerator's performance. By comparing the regenerator performance of filled copper foam and stainless-steel mesh, it was found that the copper foam regenerator had a faster start time, while the stainless-steel mesh regenerator had a higher thermal capacity. After this conclusion, an optimized regenerator is designed, filled with different materials at each end according to the material properties. After simulations, it can be concluded that this enhancement improves the regenerator's performance, increasing the Stirling engine's overall efficiency.

An Adsorption-Desorption Heat Engine for Power Generation from Waste Heat

According to the United States Department of Energy, waste heat recovery would allow up to a 20% reduction in greenhouse gases (GHG) emission. Most of the waste energy is discharged as a low-grade heat at temperatures less than 250°C. Therefore, the development of new technologies and the enhancement of existing ones to convert low-grade heat into electrical or mechanical energy are of great importance. The working principle of adsorption-desorption heat pumps with cyclic switching between adsorption and desorption is adapted in the proposed heat engine to generate electrical power from low-temperature heat. Thermodynamic analysis of the heat engine cycle is carried out for the pair adsorbant-adsorbent: CO<sub>2</sub>-activated carbon. Its efficiencies are calculated accepting the ideal gas law and an adsorption-desorption equilibrium at the key points of the cycle. The cycle consists of two isochores and two isotherms like the Stirling engine, but at the same temperature range and without heat regeneration, its thermal efficiency (work per heat supplied) can reach 11.3% vs. 5.0% and specific work 50.7 vs. 3.55 in the latter. The proposed unit has thermal efficiency in the range of Organic Rankine Cycle units and can be utilized in small-scale applications up to 40kWe, where manufacturing cost of turbines or expanders for ORCs increases dramatically. Accounting for quality (temperature) of utilized heat, the proposed cycle’s exergy efficiency, <em>ζ<sub>ex</sub></em> = 34.5% approaches that of water-steam Rankine cycles utilizing natural gas or coal combustion.

The advantages and applications of the stirling engine

Stirling engines are a kind of heat engine that achieve their function via compressing and expanding the working fluid at temperatures that are entirely different from one another. The Stirling cycle consists of four processes, two of which are isothermal and the other two are isochoric. Stirling engines may be assembled in one of three distinct configurations: alpha, beta, or gamma. They are superior to traditional heat engines, with high efficiency, low noise, and low pollution. Stirling engines may be found in various systems that produce power and those used for mechanical propulsion, heating and cooling, and other similar applications. In today's world, programs such as this are really helpful. On the other hand, they have some drawbacks, such as a low power density, a high price tag, a sluggish beginning-of-operation and reaction time, and restricted availability. This page covers a variety of topics pertaining to Stirling engines, including their history, composition, characteristics, applications, and use, as well as some of the likely next advancements in the field.

Research on the application of heat engine efficiency in reducing energy consumption

In recent years, the problem of global warming and environmental pollution has become increasingly serious, so improving the efficiency of heat engines is of great significance to reduce energy consumption. This paper uses the method of literature review to study the current situation and prospects of heat engine efficiency in reducing energy consumption in three aspects. Firstly, the heat engine and its efficiency are summarized from the theoretical derivation. Secondly, the working principles of the Carnot heat engine and the Stirling heat engine are explained in detail through formula derivation and comparative analysis. Finally, taking the air-source heat pump as an example, we explain the basic principle, operation mechanism, and technical ways to improve efficiency in detail.

Numerical and experimental investigations on coiled resonance tube of a duplex Stirling cryocooler

Duplex Stirling cryocooler is promising in mitigating methane emission due to its environmentally-friendly working gas, high thermal efficiency and high adaptivity to varying methane concentration. In this work, a coiled resonance tube is introduced to supplant the conventional straight tube in a resonance tube coupled duplex free-piston Stirling cryocooler (RT-DFPSC) to reduce footprint and elevate power density. At first, an experimental setup was built employing resistance-compliance acoustic load to produce the analogical acoustic field. It was observed from experiments that on a coiled resonance tube, an acoustic power transfer efficiency of 35% was obtained. Based on the experiments, a three-dimensional computational fluid dynamics (CFD) model was subsequently developed to pinpoint the loss mechanism. Due to the interaction of centrifugal, viscous and inertial force, there are two secondary flow vortices in the cross-section of the coiled resonance tube during the reversing flow, accounting for the primary loss. Furthermore, the acoustic loss of the coiled resonance tube increases with the decrease of the coiled diameter, while the spiral pitch has minimal effect on the acoustic and flow field. Typically, the acoustic loss of a coiled resonance tube with a diameter of 0.8 m increases by approximately 9% compared to that of a straight tube. Finally, a one-dimensional equivalent model of the coiled resonance tube was established and integrated into a one-dimensional system-level model. Compared to the straight RT-DFPSC, a system with a coiled tube resonance tube demonstrates a cooling capacity and overall exergy efficiency reduction by 465.2 W and 2.4%, respectively.