Stirling Engine Prototype Research Articles

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.

Hydraulic resistance analyses of selected elements of the prototype Stirling engine

The paper presents the results of simulation tests of hydraulic resistance and temperature distribution of the prototype Stirling alpha engine supplied with waste heat. The following elements were analyzed: heater, regenerator and cooler. The engine uses compressed air as a working gas. Analyses were carried out for three working pressure values and different engine speeds. The work was carried out in order to optimize the configuration of the engine due to the minimization of hydraulic resistance, while maintaining the required thermal capacity of the device. Preliminary tests carried out on the real object allowed to determine boundary and initial conditions for simulation purposes. The simulation assumes that there is no heat exchange between the regenerator and the environment. The solid model used in simulation tests includes the following elements: supply channel, heater, regenerator, cooler, discharge channel. Due to the symmetrical structure of the analyzed elements, simulation tests were carried out using 1/6 of the volume of the system.

A Case Study of the Development Experience of Using a Prototype Stirling Engine in A Novel Bioenergy Driven Co-Generation Plant in Bolivia

The necessity for green technology to generate power in rural regions is becoming more widely recognized. Stirling engines have attracted a lot of interest in recent years due to their relative ease of maintenance and simple design. Practical experience from the operation and maintenance of the Stirling engine Genoa-01 in Bolivia is the subject of this case study. The project uses a trial-and-error approach to maintain the engine in order to find relevant lessons that may be used in training of power plant personnel based in locations with limited technical resources. Analysis of the information gathered during the study identified the main challenges to overcome for small, decentralized power technologies as supply chain of spare parts, technical capacities, and promotion of the technology.

Pengaruh Variasi Dimensi Sirip Pada Displacer Sistem Pendingin Mesin Stirling Menggunakan Energi Surya Terkonsentrasi

Energy needs in Indonesia are increasing day by day due to population growth and economic growth. To meet the increasing energy needs, it is necessary to develop a variety of alternative energies such as: biomass, solar energy, wind energy, water energy, which are still few that utilize One of the machines that use renewable energy is the Stirling motor. A stirling motor is a type of motor that has an external combustion engine that does not require much maintenance and does not emit a lot of pollutants because it only requires a source of thermal energy to run it. In other words, solar energy can also be utilized. The method developed is the use of solar energy which is concentrated by a parabolic reflector to the hot cylinder of the Stirling engine to convert heat energy into motion energy. The purpose of this study was to determine the effect of variations of several fin dimensions and variations in the number of fins on a displacer with aluminum material. This study uses an experimental method to describe the performance of the stirling engine prototype using various dimensions of cooling fins and variations in the number of fins. The results showed that the gamma stirling engine using 6 fins, and a diameter of 38 mm, showed the best results with a time of 43 minutes with an intensity of solar radiation of 188.2 W/m² to drive the stirling engine with a speed of 189 rpm and a torque of 0.87 N. mm. The difference in temperature produced in the hot cylinder and cold cylinder is 115˚C with a thermal efficiency of 44.13%.

Prototype Stirling Engine using Low Temperature Heat Source

Stirling engines do not necessarily require the combustion of fossil fuels and are therefore attracting attention as heat engines that can use a wide variety of fuels and as low-pollution equipment. Therefore, the Stirling engine is expected to be put to practical use in areas where it is difficult to utilize internal combustion engines, such as solar heat and factory waste heat. The aim of this study is to design and build a prototype Stirling engine that can be operated using low-temperature heat sources such as snow and ice. In the prototype engine, the bore of the power piston was changed to a smaller bore and experiments were carried out and discussed. As a result, it was confirmed that the continuous operation time could be improved and that the engine could be operated at a temperature difference of about 30°C. Based on these results, a larger Stirling engine using a low-temperature heat source and a non-contact power generation method will be investigated to increase the power output.

Pengaruh konduktivitas thermal pada hot cylinder mesin stirling menggunakan energi surya terkonsentrasi

Renewable energy is one of the businesses sector that will develop rapidly after the changing economic order due to the corona outbreak. The characteristics of Indonesia's tropical climate by getting good sunlight throughout the year can be used as alternative and renewable energy. The Stirling engine is one type of external combustion engine, because combustion is carried out outside the engine using a closed regenerative cycle in which the working fluid is compressed or expanded in a separate reservoir and then distributed to drive the power piston reciprocatingly. The method developed is the use of solar energy which is concentrated by a parabolic reflector to the hot cylinder of the Stirling engine to convert heat energy into motion energy. The purpose of this study was to determine the effect of the thermal conductivity of several material specimens used in the hot cylinder of the Stirling engine including copper, stainless steel, & glass. This study uses an experimental method to describe the performance of a stirling engine prototype using various types of hot cylinder material specimens. The results showed that the gamma stirling engine using hot cylinder glass material had the best performance because with a heat conductivity of 0.78 W/m˚C it was able to drive a stirling engine with a speed of 132 rpm and a torque of 0.57 N.mm at the temperature difference between hot cylinder and cold cylinder of 88˚C and with a thermal efficiency of 20.39%.

A novel unified dynamic-thermodynamic method for estimating damping and predicting performance of kinematic Stirling engines

This paper presents a novel unified dynamic-thermodynamic (UDT) method to achieve the damping coefficient and overall performance of a kinematic Stirling engine. First, dynamic, kinematic, thermodynamic, and heat transfer equations are used to present a comprehensive model of a gamma-type Stirling engine. The equivalent inertia method is proposed to present a compact form of motion equation of the engine. Then, the proposed mathematical scheme is further employed to predict the engine speed corresponding to different values of the damping coefficient. Subsequently, a prototype Stirling engine is developed and tested to achieve the practical engine speed. Therefore, the damping coefficient of the developed gamma-type Stirling engine is identified through the proposed dynamic model taking into account the measured engine speed. Next, the overall performance of the Stirling engine in terms of engine frequency, output power, work, efficiency, gas pressure, and gas temperature is simulated via the proposed model considering finite heat transfer, imperfect regeneration, and frictional damping. Finally, the prototype Stirling engine is tested to validate the proposed mathematical procedure as well as to verify the identified damping coefficient. The good agreement between the simulation and experimental results reveal the effectiveness of the proposed modeling scheme.

Development of a 100-Watt-Scale Beta-Type Low Temperature Difference Stirling Engine Prototype

This paper documents the ongoing design process of a Stirling engine prototype for a source temperature of 95 °C, aiming to achieve shaft power on the order of 100 Watts. The engine will serve to produce experimental data for the validation of a numerical low temperature Stirling model. The higher-level motivation is to assess the technical and economical potential of producing power from abundant sources of low temperature heat by using Stirling engines. Design decisions are governed by the goals of minimizing energy losses and maximizing the variability of operating points through variable heat exchanger geometry, compression ratio and charge pressure. The resulting design is a beta engine with a total gas volume around 100 liters. It features displacer and power pistons in a combined cylindrical working space and a mechanism using pivoting links similar to a bellcrank. The stroke of the power piston is adjustable while maintaining a constant top dead center position. A component critical for friction is the power piston seal, for which a low friction rolling seal and a conventional sliding seal were considered. As of June 2021, the development is at an advanced state and the first set of components are entering production.

Development of a Beta-Type Moderate-Temperature-Differential Stirling Engine Based on Computational and Experimental Methods

Stirling engine is a favorable technique in the application of waste heat recovery or cogeneration system. This paper aims at developing a beta-type Stirling engine which is operated at moderate heating temperature (773–973 K). Rhombic drive mechanism is utilized to make coaxial motion of displacer and piston. Based on the proposed dimensions, a theoretical model combining thermodynamic and dynamic analysis is built to predict the performance of the Stirling engine. Thermodynamic analysis deals with variations of properties in each chamber while dynamic analysis handles the resultant shaft torque produced by the Stirling engine. Furthermore, a prototype engine is manufactured, and experimental test is carried out to validate the simulated results in this research. Under heating temperature of 973 K, charged pressure of 8 bar, rotation speed of 1944 rpm, shaft power of 68 W is obtained from the prototype Stirling engine. Power density is calculated to be 1.889 W-c.c.−1 by theoretical prediction and 1.725 W-c.c.−1 by tested result. The impact of the geometrical dimensions is investigated to survey the optimal piston diameter which is related to compression ratio and swept volume.

Kinematic and thermodynamic operational analysis of rhombic-drive Stirling engine prototype

This operational analysis is aimed for the next development of rhombic-drive beta-configuration Stirling engine prototype. The kinematic analysis focused on the adjustment of crank radius and connecting rod length, for achieving optimum phase angle setting and suitable eccentricity ratio based on geometrical constraints. The isothermal thermodynamic analysis is carried out to predict the engine performance between the baseline and proposed design parameters. The reciprocating displacement of moving pistons, volumetric displacement, cyclic pressure, energy produced and thermal efficiency are derived and solved. The results show that the reduction of crank radius increases the eccentricity ratio, while both reduction of connecting rod length and crank radius increase the phase angle setting. It is found that as the phase angle setting increase, the engine power output and thermal efficiency increase. The magnitudes of engine power and thermal efficiency may be elevated by modifying the geometrical design and operating condition.

Design a Solar Powered Stirling Engine Prototype to Produce Electricity

For the concerns of environmental issue such as global warming, sustainable and green way to produce energy is highly in demand. Dish Stirling system is one of the most efficient system among others concentrated solar power technologies. However, the system is in disadvantage in terms of cost and reliability when compare to others CSP technologies. In this study, a fundamental prototype of solar powered dish Stirling engine is designed, manufactured, and tested. One component of the prototype which is the power piston is malfunctioning. It was found that the accuracy requirement of the manufacturing of the prototype was high and it requires high skill and experience in machining process.

A new non-ideal second order thermal model with additional loss effects for simulating beta Stirling engines

In this paper, comprehensive governing differential equations of Stirling engines have been developed by coupling the effect of gas leakage through the displacer gap, gas leakage into the crank case and the shuttle heat loss into the traditional model. Instantaneous pressures and temperatures of the working fluid in the engine were evaluated at same time step. The present model was deployed for the thermal simulation of the GPU-3 Stirling engine and the obtained results were robustly compared to experimental data as well as results from previous numerical models. Then, parametric studies were conducted to assess the impact of geometrical and operating parameters on the performance of Stirling engines working with helium or hydrogen. Results suggest that the modifications made in this model led to better accuracy and consistency in predicting the experimental data of the prototype engine at all speeds, compared with most previous models. It was found that there exists a minimum dimensionless gap number, for every engine pressure below which mass leakage into the compression volume may not impact the brake power and energetic efficiency of the engine. In addition, an optimum mean effective pressure was found for maximum energetic efficiency of the engine. This optimum value is higher for helium gas than for hydrogen gas. Further results indicated that the brake power and energetic efficiency of the prototype Stirling engine can be significantly improved by 30% and 18%, respectively, provided that the heater temperature is raised to 850 °C while the cooler temperature is reduced to 0 °C.

Experimental characterization of an innovative low-temperature small-scale Rotary Displacer Stirling Engine

This study experimentally investigates a low-temperature, small-scale, Rotary Displacer Stirling Engine (RDSE) prototype for the first time. The RDSE represents a novel configuration utilizing a rotary displacer rather than the reciprocating displacer found in many conventional Stirling configurations. The study aims to systematically evaluate the effect of working fluid, phase angle, heat input and charge pressure. The performance of the RDSE is compared to some of the previously reported performances of Stirling engines using the dimensionless Beale (Bn) and West (Wn) numbers. Initial results indicate that 125° phase angle provides more power than the theoretically optimum 90° phase angle. The results also show comparable Bn and significantly higher Wn values (0.047 and 0.465, respectively) compared to earlier studies, and suggest that the RDSE can potentially be a competitive alternative to other SE configurations.

Design and construction of an Alfa Type Stirling Engine as a teaching prototype

This paper shows the design and construction of a Stirling engine prototype as an alternative to generate electricity as well as a teaching tool to be used with mechanical electrical engineering students. The engine will be coupled with a DC generator feeding a LED. The projected outcome power is 6W at a 12 V operation level.

Numerical modeling and optimization of beta-type Stirling engine

Numerical modelling can significantly contribute to the performance enhancement and technological advancement of Stirling engines. In this paper, a practically feasible thermodynamic model was developed for beta type of Stirling engines with rhombic-drive mechanism. Quasi-steady flow approach was adopted to analyze the heat transfer and flow friction effects of the heater, cooler, and regenerator on the performance of engine. The numerical model predicts the output power and thermal efficiency while considering the pressure drop in heat exchangers and numerous power and thermal losses. A parametric study is utilized to investigate the impact of operating and geometric parameters on the power output and efficiency of the Stirling engine. A combination of optimized temperature ratio, swept volume, regenerator matrix porosity, phase angle, pressure and engine frequency are assessed. The optimized model is then compared and validated against the experimental data obtained from the General Motor’s prototype of GPU-3 Stirling engine. Substantial improvement on the performance of the engine is achieved by optimizing the operating and geometric parameters of the engine.

A novel second-order thermal model of Stirling engines with consideration of losses due to the speed of the crack system

Very accurate second-order thermal models have been developed for the thermal simulation of Stirling engines in recent years. One of the last ones is the comprehensive polytropic model of Stirling engine called the CPMS model. The accuracy of the CPMS model was found to be sufficient for the nominal operation of a prototype Stirling engine known as the GPU-3 engine. Nevertheless, the accuracy of the CPMS model was drastically reduced at high rotational speeds of the engine. In this paper, power loss and pressure change due to the inertial force of the crank system were integrated into the CPMS thermal model in order to compensate inaccuracy of the CPMS model at high rotational speeds. Moreover, the effect of rotational speed on the gas temperature in heater and cooler was also incorporated. A precise model for evaluating the mechanical friction loss was also employed and compared with the simple frictional model of the simple frictional model used in the CPMS. The model was examined on the GPU-3 engine, and it was found that it has superior accuracy compared to the previous thermal model over the entire working regime of the GPU-3 engine.

Numerical thermodynamic model of alpha-type Stirling engine

The objective of this study is to develop accurate practical thermodynamic model for alpha-type Stirling engine with Ross Yoke mechanism. Thermal, pumping, and regeneration loses are considered in developing the thermodynamic model. Two methods for solving the governing equations are proposed. The model is used to predict the power output, and the thermal efficiency. The proposed model is validated against experimental data available from the General Motor GPU-3 Stirling engine prototype. Parametric study is used to investigate the effect of geometric and operation parameters on the engine performance. The effect of regenerator effectiveness, the dead volume ratio, regenerator thermal conductivity, and the heat source temperature, the swept volume ratio on the maximum on engine performance are evaluated. It is found that significant improvement on engine performance can be achieved by optimizing geometric and operating parameters.

Influence of phase angle and dead volume on gamma-type Stirling engine power using CFD simulation

This work presents the development and validation of computational fluid dynamics (CFD) model of 500W gamma-type Stirling engine prototype to highlight the effects posed by phase angle and dead volume variations on engine performance. The model is based on a realistic Local Thermal Non-Equilibrium (LTNE) approach for porous domains in the engine (cooler and regenerator). The simulation results showed an acceptable degree of accuracy of 9% and 5%, respectively when comparing with experimental results in predicting the indicated and cooling powers at different heating temperatures. It is found that the maximum indicated power is achieved at a phase angle of 105° rather than at the common phase angle of 90°. The dead volume (connecting pipe) is observed to pose negative effects on engine indicated power and therefore, an optimum value of pipe diameter exists.

Enhanced thermodynamic modelling of a gamma-type Stirling engine

Modelling can substantially contribute to the development of Stirling engines technology and help understanding the fundamental processes of the real cycle for further performance improvement. In the present work, an enhanced thermodynamic model for Gamma-type Stirling engine simulation was developed based on the reconfiguration of non-ideal adiabatic analysis. The developed model was validated against experimental measurements on Stirling engine prototype (ST05 CNC), available at University of Birmingham. Good agreement was found between the model and experiment in predicting the indicated power, shaft power and thermal efficiency at different operating conditions. A parametric study was carried out to investigate the effect of phase angle, gas type, regenerator matrix type and dead volume on engine performance. The feasibility of utilizing the stored cold energy of LN2 to maximize the shaft power was also presented. Results showed that shaft power can be significantly enhanced by 49% for helium and 35% for nitrogen when cooling temperature is lowered to −50°C while heating temperature remains constant at 650°C.

Double acting Stirling engine: Modeling, experiments and optimization

A three phase free piston type double acting Stirling engine model is proposed and validated using experimental results. The modeling strategy is based on a combination of two sub-models: a global thermal model of the engine to deal with heat sources coupling and a detailed equivalent electrical network model which accounts for the gas and mechanical dynamic physics of the engine. Derived features, such as the amplitude, the frequency, the compression and the expansion powers are then finally obtained. The model is experimentally validated with a prototype of a free piston Stirling engine. Mean error on the amplitude, the frequency, the internal temperatures and the compression and expansion powers is 9%, so the model is considered accurate enough to predict performances.For optimization purpose, a numerical analysis is performed selecting the three following critical parameters: (i) dead volume of the chambers, (ii) natural frequency of the mechanical oscillators and (iii) thermal conduction between hot and cold sides. Smaller dead volume, large oscillating mass and high insulation are to be sought for maximizing the performances. With a pressurization of 3bar, a theoretical useful power of 18W can be reach with conservative modification of the existing prototype. Moreover, energy and exergy analyses highlight the main losses in the system: thermal leakage, gas spring hysteresis as well as heat transfer and viscous dissipation in the heat exchangers.