scholarly journals Optimisation of a Quasi-Steady Model of a Free-Piston Stirling Engine

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 72 ◽  
Author(s):  
Ayodeji Sowale ◽  
Edward Anthony ◽  
Athanasios Kolios
Keyword(s):  
Power Systems ◽  
Thermal Efficiency ◽  
Waste Heat ◽  
Stirling Engine ◽  
Design Parameters ◽  
Free Piston ◽  
Output Performance ◽  
Free Piston Stirling Engine ◽  
External Combustion ◽  
Work Done

Energy from waste heat recovery is receiving considerable attention due to the demand for power systems that are less polluting. This has led to the investigation of external combustion engines such as the free-piston Stirling engine (FPSE) due to its ability to generate power from any source of heat and, especially, waste heat. However, there are still some limitations in the modelling, design and practical utilisation of this type of engine. Modelling of the FPSE has proved to be a difficult task due to the lack of mechanical linkages in its configuration, which poses problems for achieving stability. Also, a number of studies have been reported that attempt to optimise the output performance considering the characteristics of the engine configuration. In this study the optimisation of the second-order quasi-steady model of the gamma-type FPSE is carried out using the genetic algorithm (GA) to maximise the performance in terms of power output, and considering the design parameters of components such as piston and displacer damper, geometry of heat exchangers, and regenerator porosity. This present study shows that the GA optimisation of the RE-1000 FPSE design parameters improved its performance from work done and output power of 33.2 J and 996 W, respectively, with thermal efficiency of 23%, to 44.2 J and 1326 W with thermal efficiency of 27%.

scholarly journals From Beale Number to Pole Placement Design of a Free Piston Stirling Engine

2017 ◽  
Vol 64 (4) ◽  
pp. 499-518 ◽  
Author(s):  
Shahryar Zare ◽  
Alireza Tavakolpour-Saleh ◽  
Amir Omidvar
Keyword(s):  
Closed Loop ◽  
Design Procedure ◽  
Stirling Engine ◽  
Pole Placement ◽  
Design Parameters ◽  
Dynamic Systems Theory ◽  
Design Technique ◽  
Free Piston ◽  
Frictional Damping ◽  
Free Piston Stirling Engine

Abstract In this paper, pole placement-based design and analysis of a free piston Stirling engine (FPSE) is presented and compared to the well-defined Beale number design technique. First, dynamic and thermodynamic equations governing the engine system are extracted. Then, linear dynamics of the free piston Stirling engine are studied using dynamic systems theory tools such as root locus. Accordingly, the effects of variations of design parameters such as mass of pistons, stiffness of springs, and frictional damping on the locations of dominant closed-loop poles are investigated. The design procedure is thus conducted to place the dominant poles of the dynamic system at desired locations on the s-plane so that the unstable dynamics, which is the required criterion for energy generation, is achieved. Next, the closed-loop poles are selected based on a desired frequency so that a periodical system is found. Consequently, the design parameters, including mass and spring stiffness for both power and displacer pistons, are obtained. Finally, the engine power is calculated through the proposed control-based analysis and the result is compared to those of the experimental work and the Beale number approach. The outcomes of this work clearly reveal the effectiveness of the control-based design technique of FPSEs compared to the well-known approaches such as Beale number.

Development and Performance Measurements of a Beta-Type Free-Piston Stirling Engine Along With Dynamic Model Predictions

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Kyuho Sim ◽  
Dong-Jun Kim
Keyword(s):  
Dynamic Model ◽  
Stirling Engine ◽  
Electric Heater ◽  
Performance Measurements ◽  
Free Piston ◽  
Dynamic Behaviors ◽  
Output Performance ◽  
Model Predictions ◽  
And Performance ◽  
Free Piston Stirling Engine

This paper presents the development and performance measurements of a beta-type free-piston Stirling engine (FPSE) along with dynamic model predictions. The FPSE is modeled as a two degrees-of-freedom (2DOF) vibration system with the equations of motion for displacer and piston masses, which are connected to the spring and damping elements and coupled by working pressure. A test FPSE is designed from root locus analyses and developed with flexure springs and a dashpot load. The stiffness of the test springs and the damping characteristics of the dashpot are identified through experiments. An experimental test rig is developed with an electric heater and a water cooler, operating under the atmospheric air. The piston dynamic behaviors, including the operating frequency, piston stroke, and phase angle, and engine output performance are measured at various heater temperatures and external loads. The experimental results are compared to dynamic model predictions. The test FPSE is also compared to a conventional kinematic engine in terms of engine output performance and dynamic adaptation to environments. Incidentally, nonlinear dynamic behaviors are observed during the experiments and discussed in detail.

Maximum Work of Free-Piston Stirling Engine Generators

2017 ◽  
Vol 42 (2) ◽  
Author(s):  
Shinji Kojima
Keyword(s):  
Stirling Engine ◽  
Joule Heat ◽  
Adjoint Equations ◽  
Carnot Cycle ◽  
Work Loss ◽  
Free Piston ◽  
Maximum Work ◽  
Free Piston Stirling Engine ◽  
Work Done

AbstractUsing the method of adjoint equations described in Ref. [1], we have calculated the maximum thermal efficiencies that are theoretically attainable by free-piston Stirling and Carnot engine generators by considering the work loss due to friction and Joule heat. The net work done by the Carnot cycle is

Design and Performance of a Diaphragm Free-Piston Stirling Engine for Power Production From Low-Temperature Heat Sources

2018 ◽  
Author(s):  
Anas Nawafleh ◽  
Khaled R. Asfar
Keyword(s):  
Low Temperature ◽  
Waste Heat ◽  
Engine Performance ◽  
Surface Friction ◽  
Stirling Engine ◽  
Operating Conditions ◽  
Physical Parameters ◽  
Free Piston ◽  
And Performance ◽  
Free Piston Stirling Engine

This paper addresses modeling, design, and experimental assessment of a Gamma type low-temperature differential free-piston Stirling engine. The most advanced third-order design analysis method is used to model, simulate and optimize the engine. Moreover, the paper provides an experimental parametric investigation of engine physical parameters and operating conditions on the engine performance. The experimental test results are presented for a model validation, which shows about a 5% to 10% difference in the simulation results. The aim of this study is to design a Stirling engine capable of harvesting low-temperature waste heat effectively and economically and convert it to power. The engine prototype is designed to increase the engine performance by eliminating the main losses occurred in conventional Kinematic engines. Thus, elastic diaphragm pistons are used in this prototype to eliminate the surface friction of the moving parts, the use of lubricant, and to provide appropriate seals. In addition, flat plate heat exchangers, linear flexure bearing, a stainless-steel regenerator and a polyurethane displacer are outlined as the main components of the engine. Experiments successfully confirm the design models for output power and efficiency. Furthermore, it is revealed that the displacer-to-piston natural frequency ratio is an important design point for free-piston Stirling engines and should be addressed in the design for optimum power output.

Design of a Free Piston Stirling Engine Power Generator

2019 ◽  
Author(s):  
Ruijie Li ◽  
Yuan Gao ◽  
Koji Yanaga ◽  
Songgang Qiu
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
High Efficiency ◽  
Waste Heat ◽  
Combustion Engine ◽  
Engine Performance ◽  
Flow Distribution ◽  
Stirling Engine ◽  
Free Piston ◽  
Free Piston Stirling Engine

Abstract Free Piston Stirling Engine is an external combustion engine, which can use diversified energy resources, such as solar energy, nuclear energy, geothermal energy, biomass, industrial waste heat etc. and is suitable for the remote area power generation due to the advantage of robustness, durability, reliability, and high efficiency. In this work, a Free Piston Stirling Engine has been designed based on the numerical simulation results and previous experimental experience. Direct Metal Laser Sintering method has been adopted for the manufacturing of the key components including the displacer cap, displacer body, piston housing, cold heat exchanger, and regenerator. One dimension analysis using Sage software has been conducted. The designed engine has a power output of 65W with the hot and cold end temperature is 650°C and 80°C respectively, and charge pressure is 1.35 MPa. Finite Element Method has been used to analyze the structural stress of the engine, which is operated at the high temperature and high pressure, to determine if it is able to tolerate the operating condition designed by the Sage according to the Section VIII Division 2 of the ASME Boiler and Pressure Vessel (BPV) Code. In addition, Computational Fluid Dynamics (CFD) method has been used to investigate the flow distribution in heat exchangers (heat acceptor, regenerator, and heat rejecter), as the heat exchanger performance affect the engine performance greatly. Considering the large mesh number, a quarter of the heat exchangers have been investigated, in order to reduce the mesh numbers and accelerate the calculation speed.

scholarly journals Numerical Analysis of the Adiabatic and Quasi Steady Model of Free Piston Stirling Engine

2018 ◽  
Vol 198 ◽  
pp. 04005
Author(s):  
Ayodeji Sowale ◽  
Athanasios J. Kolios
Keyword(s):  
Output Power ◽  
Stirling Engine ◽  
Operating Conditions ◽  
Design Parameters ◽  
Stable Operation ◽  
Free Piston ◽  
Temperature Efficiency ◽  
Mathematical Equations ◽  
Free Piston Stirling Engine ◽  
Good Agreement

This study presents the numerical simulation of the adiabatic and Quasi steady models of the free piston Stirling engine, the mathematical equations are presented, and design parameters are determined and used as input for the simulation. The simulations are computed under adiabatic and Quasi operating conditions, and their output results are compared. The similarities and differences in the model predictions in terms of the pressure to volume diagram, the amplitudes of the pistons and displacer, temperature, efficiency, power output and stable operation are observed and investigated. The models are validated against the experimental output and the results show a good agreement with the experiment. The adiabatic model predicted an output power of 862 W, while Quasi steady model predicted more accurate output power of 997W at frequency of 30 Hz in relation to the 1000 W of the experimental output. The effects of the variation of engine’s parameters on the output power are also observed and presented.

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