Performance Of Stirling Engine Research Articles

Experimental optimization of displacer working gap in a gamma-type Stirling engine

In this experimental study, the effects of the working gap between the displacer and its cylinder on the performance of a gamma configuration Stirling engine were investigated. The torque and power variations with engine speed were investigated for four different working gap values as 0.5, 0.7, 0.9, and 1.1 mm. Experiments were carried out with an LPG-fueled heater at a hot surface temperature of 375 °C and a cold surface temperature of 30 °C. Helium was used as the working mass and the tests were performed between 0.5 and 3.5 bar initial pressure with 0.5 bar ranges. According to the experimental results, the gap width has a significant effect on the gap losses and heat transfer and directly affects the performance of the gamma Stirling engine. Therefore, optimizing the gap width is necessary if the Stirling engine's efficiency is to be increased. In this study, the optimum displacer gap value was obtained as 0.9 mm for 90 mm cylinder diameter and 190 mm displacer length of a gamma Stirling engine. Maximum output power and torque were obtained at 3 bar initial pressure and 0.9 mm displacer gap as 45.06 W at 260 rpm and 2.18 Nm at 170 rpm, respectively. This study made an essential contribution to the literature by performing an experimental gap width optimization.

Performance Analysis of Stirling Engine Type Alpha Using Thermodynamic Approach Based on Schmidt Theory

Environmental concern and the impact on climate change have spawned various technological innovations for high efficiency engines that save fuel and produce less carbon emissions. Technological innovations that operate on a closed cycle can use variety of heat sources, produce no emissions and very high efficiency was Stirling engine. This research aims to design a Stirling engine type Alpha with a capacity of 228 cc with a phase angle of 90 degrees, then analyze its performance in the form of power indicators and thermal efficiency indicators and determine the effect of the increase in temperature difference between the compression chamber temperature and the expansion chamber temperature towards engine rotation speed. The method used to analyze engine performance is the Schmidt method, which is a Stirling engine performance analysis method based on isothermal expansion and ideal gas compression. The result of this research is that the Stirling engine which is designed starts working when the compression chamber temperature is 31.9 degrees Celsius and the expansion chamber temperature is 482.2 degrees Celsius. The highest engine speed is 598 rpm which is obtained at a compression chamber temperature of 45.5 degrees Celsius and an expansion chamber temperature of 662.4 degrees Celsius. The engine power indicator is 194.6 watt at 598 rpm, while the thermal efficiency indicator is 65.94 percent. Based on the experimental data, it is also known that the increase in temperature difference between the compression chamber temperature and the expansion chamber temperature causes an increase in engine rotation speed.

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

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.

Integration of a Gamma-Type Stirling Engine with LPG Cooking Stove for Micro-Scale Combined Heat and Power Generation

The Stirling engine is one of the most versatile micro-scale prime movers for combined heat and power applications, adaptable to different levels of heat sources. This study started a unique journey that included developing, experimenting, and analyzing the Gamma-type Stirling engine. Notably, the engine design ingeniously harnesses heat from a customized cooking stove burner powered by liquefied petroleum gas. The engine fabrication resulted in a compression ratio 2.014, accommodating a volumetric capacity of 181 cc. The Stirling engine test used air as the working gas, and the initial conditions were at atmospheric pressure. Stirling engine performance was analyzed using an ideal thermodynamic cycle model and burner efficiency using the water boiling method. The modified burner attains an average temperature of 699.5°C, producing a burner power output of 5.702 kW and a thermal efficiency of 32.7% or around 1.867 kW of heat for operating the engine and cooking activities. Simultaneously, tests of the Stirling engine revealed an average air temperature difference of 146.2°C between the expansion and compression phases. The flywheel rotation speed ranges from 158 to 369 rpm. During testing, the Stirling engine obtained an average thermal efficiency of 31.08%, accompanied by an ideal power spectrum ranging from 0.3 W to 42.6 W. The highlight of this study was the maximum pressure achieved at the end of the heat absorption stage, recorded at 296.1 kPa. Importantly, these findings underscore the promising potential of micro-Combined Heat and Power systems. Integrating the gamma-type Stirling engine with the LPG stove represents novelty and paves the way for further development and advancement in sustainable energy solutions.

Performance optimization of a free piston Stirling engine using the self-directed online machine learning optimization approach

To achieve a good match between the thermodynamic, dynamic, and structural parameters of a free-piston Stirling engine (FPSE), a numerical model that couples thermodynamics with dynamics was developed and experimentally verified in this study. A multi-objective optimization of Stirling engine performance was proposed based on a self-online machine learning optimization approach, which integrated a deep neural network with the numerical model. The spring stiffness of the displacer and power piston, average pressure, and rod diameter of the displacer were selected as factors, and the dimensionless work and efficiency of the FPSE were the objectives to be optimized. Based on the prediction of the deep neural network, the possible optimal design point was determined, and new query points were dynamically generated and evaluated using the numerical model of the FPSE. The optimal design values of the spring stiffness of the displacer and power piston, average pressure, and rod diameter of the displacer were 20800 N/m, 22500 N/m, 3.1 MPa, and 5.5 mm, respectively. The corresponding dimensionless work and efficiency were 0.59 and 34%, respectively, which increased by approximately 9.3% and 4.3%, respectively, compared with that of initial samples. In addition, the shuttle loss of the displacer and damping dissipation of pistons were efficiently reduced, decreasing the thermal and power losses by approximately 3.1% and 14%, respectively.

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.

Comparison of the dynamic characteristics and performance of beta-type Stirling engines operating with different driving mechanisms

Comparison of the dynamic characteristics and performance of beta-type Stirling engines operating with different driving mechanisms

Enhancing solar stirling engine performance through the use of innovative heat transfer fin shapes

One of the challenges in designing and optimizing solar energy systems is achieving maximum power and efficiency at the lowest cost. This study focuses on using heat transfer fins to enhance energy absorption in the heater section of a solar Stirling engine. To begin, we model a parabolic solar collector system, considering factors that influence the amount of heat transfer to the heater section of the Stirling engine. Next, we model the Stirling engine using the PSVL model, which accounts for factors such as gas leakage, the temperature distribution in heat exchangers, longitudinal heat loss, polytropic heat transfer in cylinders, and other effects. In this paper, we also propose modifications to the basic model and introduce heat transfer fins made of FGM, with unique geometry and variable thickness, on the heater section of the solar Stirling engine to increase the heat received by the working fluid. We perform a thermal analysis of the fins to evaluate their impact on the heat the Stirling engine receives, including the effects of convection and radiation on the environment. We find that using these new fins in the heater section of the Stirling engine significantly increases the power and efficiency of the system.

Optimal performance identification of a combined free piston Stirling engine with a permanent magnet linear synchronous machine using dedicated controls

• A Linear Synchronous Machine combined with a Free Piston Stirling Engine. • For the combined system, two different control methods were developed. • Based on the control methods, the performance of the combined system was optimized. • The performance and application of the two control methods were compared. In the present study, to find the optimal performance of a combined RE-1000 Free Piston Stirling Engine (FPSE) with a three-phase Permanent Magnet Linear Synchronous Machine (PMLSM), two different control methods were developed. To convert the produced mechanical power of the FPSE to the electrical one, generally, it should be coupled with a linear generator. Here, a three-phase PMLSM was chosen to convert the linear movement of the FPSE to electricity. The control of the FPSE system was also done through this generator using velocity control. It is possible to obtain the optimal system behavior based on the identification of the adapted velocity reference value. Based on two different methods, the FPSE-PMLSM optimum working point was determined. In the first method, an open-loop sinusoidal wave was assumed as the reference velocity, and its amplitude and frequency were optimized. In the second method, the reference velocity was identified using closed-loop feedback of the electromagnetic force, and the optimal feedback coefficient was found. The results show that apart from the advantages and disadvantages related to each method, the optimized point was almost identical.

The Influence of the working fluid and Regenerator material on the Performance of the types Gamma Stirling Engine

In concentrated solar energy applications, the Stirling engine is the optimum option for extracting mechanical work. The engine's most notable features are minimal noise, vibration, and pollution, as well as its capacity to function with any external heat source, including biomass, solar energy, and industrial waste. The gamma-type STE-1008 Stirling engine is the subject of our research. This engine can handle a maximum charging pressure of 10 bar. The engine is divided into two sections (expansion and compression) and three heat exchangers (regenerator, cooler, and heater). The cooler is a finned aluminium heat exchanger with 144 internal fins, each with a cross-sectional area of 1 mm by 10 mm. The regenerator is fitted with a diameter of 31 m and a volumetric porosity of 90%. This investigation employed a random fiber with three different metals: stainless steel, copper, and aluminium. Nitrogen and air served as the working fluids. From the results, stainless steel, copper, and aluminium regenerators produced 583 W, 562 W, and 553 W, respectively. When nitrogen is utilized at 500 °C, the engine generates 11 N.m of torque compared to 8.5 N.m when air is used, and the engine has a thermal efficiency of 19% compared to 15% when air is used. The results of other researchers were used to compare and validate our model. With errors of no more than 12%, the results were close enough to the experimental data to be useful.

Factors Affecting the Thermodynamic Performance of the Stirling Engines: a Review Study

Stirling engines are efficient heat engines distinguished by their capacity to employ alternate fuel sources as a source of heat, such as solar energy, making them an important study issue. The goal of this research is to discover new ways and strategies for improving Stirling engine performance for future development. This article presents reviews a series of research studies on Stirling engine technology, focusing on the main factors and characteristics influencing engine performance, such as Stirling engine types and mechanical configuration, operating parameters, geometric parameters, and working fluid properties. It demonstrated its capacity to work in a varied range of temperatures, and many different types of fuels which can be used as a heat source for operation. Regarding Stirling engine types, the Gamma engine is the most efficient due to its capacity to produce high efficiency and power when compared to Alpha and Beta engines. Stirling engines require working fluids that have high thermal conductivity, high heat capacity, and low viscosity, helium and air are common working fluids used practically. Moreover, phase angle is an important geometric parameter affecting Stirling engine performance. The optimal value is theoretically around 90°. The findings obtained in this article describe the Stirling engine's potential. In conclusion, the mechanical and physical characteristics of the engine and the properties of the working fluids are the most important factors in the performance of Stirling engines.

Energy conversion of biogas from livestock manure to electricity energy using a Stirling engine

• Stirling engine performance prediction is evaluated, and specific biogas consumption, biomethane production and number of animals required for a continuous operation are calculated. • When biogas is composed of 60% of methane and engine is heated to 1000 K, 88 pigs or 26 dairy cows are needed to produce 2.1 kW of shaft power or 50 kWh per day. • When biogas is composed of 60% of methane and engine is heated to 1000K, 710 and 1090 liters of daily water feeding rate and 190 and 340 kg of daily biomass feeding rate are required in a biodigester with a capacity of 26 and 40 m 3 when operating with pig and cow waste, respectively. • When the engine hot chamber is at 1000 K the output power is 2089 W. In this condition, the required mass flow is 20.0 m 3 /h for biogas with 80% of CH4 and 47.0 m 3 /h, in case of having low quality biogas (e.g. 40% concentration). • The mathematical modelling proposed in this work allows the extrapolation for other Stirling engines and other operating conditions. The use of biogas can present an interesting alternative for energy production, especially in regions far from conventional centers of power production and distribution, such as estates with agricultural and livestock activity, in addition to representing an environmentally adequate manner of dealing with its bio-waste. In order to prove this potential, the present work evaluates, through simplified mathematical models, a decentralized biogas production system from the livestock tailings biodigestion and its use for power generation using a Stirling engine. For this, the Stirling engine, the burner combustion and the bio-digestion, which work in a dependent way, were modeled. Thus, the biogas consumption, the cattle or swine population size necessary to supply the biomass demand, the amount of water needed in the process and the biodigester volume were estimated. The influence of the methane concentration and air humidity in combustion are evaluated, as well as the convective coefficient of heat transfer between the combustion gases and the engine during energy generation. Through this analysis, it is concluded that when biogas is composed of 60% of methane and engine is heated to 1000 K, 88 pigs or 26 dairy cows are needed to produce 2.089 kW of shaft power or 50 kWh per day, with 535 and 325 liters of daily water feeding rate and 180 and 325 kg of daily biomass feeding rate in a biodigeste with a capacity of 18.7 and 11.3 m 3 when operating with pig and cow waste, respectively.

Development of a new technique of waste heat recovery in cement plants based on Stirling engine technology

Cement plants are one of the most energy consuming industries in which a large amount of heat energy is lost into the atmosphere causing the increase of environmental issues and leading to the rise of cement production energy cost. Recently, waste heat recovery systems such as steam and Rankine cycles have received much attention by researchers and industrial sectors for power production application to enhance the system efficiency. However, the existing waste heat recovery systems present different drawbacks. This paper proposes, for the first time, a new technique of recovering cement plants waste heat based on Stirling engine technology. The modelling of a Gamma type Stirling engine was conducted for recovering the waste heat released from the clinker cooling process. Furthermore, the non-ideal adiabatic model was used for engine designing in MATLAB software. For model validation step, the results obtained from the present study have been compared with experimental data of Lewis Research Center in the National Aeronautics and Space Administration and previous numerical models. The comparison findings have shown a high accuracy of the current model. The effect of several geometrical and physical specifications on Stirling engine performances was studied to obtain the best engine design. The results showed that maximum efficiency can be achieved by increasing the regenerator porosity up to 79 % and by decreasing the regenerator length to 0.015 m. A matrix wire diameter of 50 μm has been found as an optimum value regarding the high output power generated and acceptable heat input required. The parametric analysis of heat exchangers geometries has revealed that the increase of the heater and cooler tube lengths reduces the engine performances. However, the rise of heater and cooler tube inner diameters could enhance the power and efficiency. Furthermore, it was found that the variation of phase angle has an important influence on Stirling engine outputs, thus the consideration of 90 degree as phase angle is more suitable for engine design which will be able to produce 1641.36 W with a thermal efficiency of 21.29 %. Additionally, it was concluded that the augmentation of pressure and rotational speed increases the engine power. Finally, it was shown that the rise of working gas mass enhances the engine output power but increases the heat input requirement. This work demonstrates the potential of using Stirling engine technology for cement plants waste heat recovery applications and highlights its ability to produce high output performances.

Theoretical investigations of Stirling engine performances for different filling gas properties

Stirling engine research has increased and opened new industrial opportunities. Stirling engines have the advantage of running on any sort of thermal energy. However, their biggest downside is their low experimental efficiency compared to Carnot's optimal efficiency. Thus, much research studies the optimal working parameters of this engine. Most existing models evaluate the Stirling engine's performance using the perfect gas assumption. However, this assumption is only valid for low pressures. At high pressure, real gas behaves differently from perfect gas. Hence the necessity and the interest of the conducted research work. The major goal of this numerical study was to analyze the influence of gas qualities on Stirling engine power and efficiency using a semi-real gas assumption. The impact of operating and geometric parameters on the performance of a four-cylinder Stirling engine (FCSE) were explored for three monatomic gases (Helium, Neon, and Argon) and one diatomic gas (Nitrogen). The dependence of volume ratio, regenerator form factor, load pressure, hot end temperature and rotation speed on gas properties were investigated. Major significant losses were accounted for at different conditions. To figure out parameters that maintain the highest performance, four different regenerator porosity (60%, 70%, 80%, 90%), three different cylinder diameters (3.5, 4, 4.5 cm) and three different phase shifts between the two pistons ( 2 π 5 $$ \frac{2\pi }{5} $$ , π 2 $$ \frac{\pi }{2} $$ , 3 π 5 $$ \frac{3\pi }{5} $$ ) were evaluated. As regards, the obtained results, not only the optimum parameters that provide higher output power were identified but also predicted correlations for each studied filling fluid as a function of the geometric and operating parameters. The outcomes of the study would be very helpful for a new more powerful engine design. The obtained results clearly demonstrated that: (a) The choice of the filling gas is determined by the regenerator form factor. (b) The optimum volume ratio for nitrogen is roughly 1.1, whereas for Helium it is around 0.7. (c) For Helium and Neon, the output power diminishes as the volume ratio rises. (d) The output power increases significantly when the regenerator form factor (length by diameter) <0.2 and then reaches an optimum of around 2.1 kW for the Helium case. (e) Among the four studied gases, the use of Helium allows obtaining the highest output power. On the other hand, it is observed that the lowest output power is obtained when using Argon. Inside Stirling engines, the use of lightweight monoatomic gases (with high thermal conductivity and heat capacity values) boosts the output power. There is a variation in power up to 50% depending on the properties of the filling gas.

Experimental investigation of the effects of hot-end and cold-end connection on the performance of a gamma type Stirling engine

External combustion Stirling engines are considered as an alternative to the solution of increasing energy and environmental problems due to their ability to work with any heat source and to be an efficient energy conversion system. In this study, the effects of hot-end and cold-end connections of power and displacer cylinders on the performance of a gamma-type Stirling engine (GTSE) were investigated experimentally. The effects of the connection type between the power and displacer cylinders on the engine performance were compared at the same operating conditions without making any structural modifications to the engine. The performance tests were conducted using helium as the working gas at different charging pressures. The experimental results show that the maximum values of the engine torque and output power were obtained at a certain charging pressure for both hot-end and cold-end connected engines. Compared to the cold-end connection (CEC) engine, the maximum torque and output power increased in the hot-end connection (HEC) engine at the same temperature range. In the HEC engine, the maximum engine torque and power were achieved as 0.5665 Nm and 23.35 W, resulting in an increase of 68.4% and 84.7% compared to those of the CEC engine, respectively.

A New Coupled Approach for Enthalpy Pumping Consideration in a Free Piston Stirling Engine (FPSE)

One group of losses that can considerably affect the performance of Free Piston Stirling Engines’ (FPSE) is the enthalpy pumping and the shuttle effect, which are due to the gap standing between the cylinder and the displacer. The shuttle effect is induced by the periodic displacer motion between the hot and the cold sources. The enthalpy pumping, which is the subject of the present study, is due to the short-circuit-like flow between the hot and cold spaces. To study these losses, first, a fine nonlinear dynamic model of the FPSE is developed and validated. Then, to study the enthalpy pumping based on that, a coupled model (for the first time) and a decoupled model are presented. The difference between the two models is that the first one provides a dynamic and a thermic linkage between the Stirling and loss model, while the second one studies them separately. The effect of the gap size on both loss models was investigated. The coupled and decoupled modeling results were quite different due to the considerable effect of the enthalpy pumping on the FPSE response. The results showed that the enthalpy pumping in the decoupled model exceeds the total output power when the gap exceeds 30 μm, and when the gap exceeds 70 μm, the enthalpy pumping is around ten times larger than the output power. In contrast, the enthalpy pumping in the coupled model is always less than the output power, which is logical. Thus, the coupled one was presented as the adapted model that should be considered for further FPSE studies.

Examine Fuzzy System to Present an Equilibrium Model for the Internal Pressure Losses of Alpha Type Stirling Engine: Comparison with ANN Model

Global warming associated with the greenhouse effect urge finding alternative energy strategies concerned with sustainable energy resources that are environmentally friendly and provide energy saving. Waste heat recovery engines are attracting devices that convert usually wasted energy to valuable mechanical or electrical energy. The current research aims to develop a mathematical model to investigate the effects of regenerator physical dimensions on the alpha Stirling engine performance indicators. A mathematical model integrating an internal pressure drop has been proposed to act as a thermodynamic optimization tool for the Stirling engine. The main conclusion was that both geometrical factors and working fluid initial charge (gas mass) craft the performance parameters of alpha type Stirling engine that operates with air as working material. After that, Artificial neural networks of Levenberg Marquardt and Orthogonal Distance Regression models, and Fuzzy systems trained for Mass Charge from M = 0.002 to 0.004 Kg are compared to find the least uncertainty. Results revealed that the Fuzzy system and Orthogonal Distance Regression model could predict more effectively than the Levenberg Marquardt model.

Tuning the performance of a micrometer-sized Stirling engine through reservoir engineering

Colloidal heat engines are paradigmatic models to understand the conversion of heat into work in a noisy environment - a domain where biological and synthetic nano/micro machines function. While the operation of these engines across thermal baths is well-understood, how they function across baths with noise statistics that is non-Gaussian and also lacks memory, the simplest departure from the thermal case, remains unclear. Here we quantified the performance of a colloidal Stirling engine operating between an engineered memoryless non-Gaussian bath and a Gaussian one. In the quasistatic limit, the non-Gaussian engine functioned like a thermal one as predicted by theory. On increasing the operating speed, due to the nature of noise statistics, the onset of irreversibility for the non-Gaussian engine preceded its thermal counterpart and thus shifted the operating speed at which power is maximum. The performance of nano/micro machines can be tuned by altering only the nature of reservoir noise statistics.

Theoretical model of a α-type four-cylinder double-acting stirling engine based on energy method

The double-acting Stirling engine is a type of Stirling engine which comprises four engine units with only four pistons. In this paper, an energy method is proposed for solving the relationship between the crank angle of the main shaft and the work generated by the working fluid. The proposed method is capable of finding the relationship more efficiently without solving the equations of motion of all the links of the linking mechanism. The wobble yoke mechanism is chosen as the transmission mechanism of the proposed engine. A modified non-ideal adiabatic model was employed for predicting the transient variation in the thermal properties of working fluid. The transient behavior of the kinetic energy and potential energy of the linking mechanism, the work loss due to friction, shaft work, and indicated work were discussed. The simulation results show that the maximum shaft power of the proposed engine is 1103 W at 878 rpm under the loading torque of 12 N m at the heating temperature of 1200 K. In addition, the regenerator's porosity of 0.666 gives the maximum shaft power 683 W for the proposed engine. The proposed model has successfully predicted the performance of the four-cylinder double-acting Stirling engine.