Numerical model for predicting thermodynamic cycle and thermal efficiency of a beta-type Stirling engine with rhombic-drive mechanism

2010 ◽  
Vol 35 (11) ◽  
pp. 2590-2601 ◽  
Author(s):  
Chin-Hsiang Cheng ◽  
Ying-Ju Yu
Keyword(s):  
Numerical Model ◽  
Thermal Efficiency ◽  
Thermodynamic Cycle ◽  
Stirling Engine ◽  
Drive Mechanism

scholarly journals A Theoretical Study on the Thermodynamic Cycle of Concept Engine with Miller Cycle

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1051
Author(s):  
Jungmo Oh ◽  
Kichol Noh ◽  
Changhee Lee
Keyword(s):  
Compression Ratio ◽  
Thermal Efficiency ◽  
Engine Performance ◽  
Thermodynamic Cycle ◽  
Expansion Ratio ◽  
Boost Pressure ◽  
Miller Cycle ◽  
Compression Pressure ◽  
Air Mass ◽  
Atkinson Cycle

The Atkinson cycle, where expansion ratio is higher than the compression ratio, is one of the methods used to improve thermal efficiency of engines. Miller improved the Atkinson cycle by controlling the intake- or exhaust-valve closing timing, a technique which is called the Miller cycle. The Otto–Miller cycle can improve thermal efficiency and reduce NOx emission by reducing compression work; however, it must compensate for the compression pressure and maintain the intake air mass through an effective compression ratio or turbocharge. Hence, we performed thermodynamic cycle analysis with changes in the intake-valve closing timing for the Otto–Miller cycle and evaluated the engine performance and Miller timing through the resulting problems and solutions. When only the compression ratio was compensated, the theoretical thermal efficiency of the Otto–Miller cycle improved by approximately 18.8% compared to that of the Otto cycle. In terms of thermal efficiency, it is more advantageous to compensate only the compression ratio; however, when considering the output of the engine, it is advantageous to also compensate the boost pressure to maintain the intake air mass flow rate.

A New Concept of Externally Heated Engine—Comparisons with the Stirling Engine

1996 ◽  
Vol 210 (5) ◽  
pp. 363-371 ◽  
Author(s):  
L Brzeski ◽  
Z Kazimierski
Keyword(s):  
Low Power ◽  
Power Density ◽  
Internal Combustion Engines ◽  
Thermodynamic Cycle ◽  
Rotational Frequency ◽  
Stirling Engine ◽  
Maximum Pressure ◽  
Combustion Engines ◽  
Working Medium ◽  
Engine Cylinder

This paper presents a new concept of the externally heated valve (EHV) engine. Air can be used as a working medium in the closed cycle of this engine. Heat delivered to the working air can come from a combustion chamber or another heat generator of an arbitrary type. The engine construction and the thermodynamic cycle performed by it are original and entirely different from the well-known Stirling engine. The main disadvantage of the Stirling engine is its low power density, that is the low power obtained per litre of the engine cylinder volume. In the case of the engine presented here it is possible to achieve power density and efficiency similar to those typical of advanced internal combustion engines. Comparisons between the power of the Stirling engine and the power of the new engine have been performed for the same engine capacity, rotational frequency and maximum and minimum temperatures of the cycle. At the same minimum pressure of the working gas in both engines, the power of the EHV engine is several times higher than that of the Stirling engine, while, on the other hand, at the same maximum pressure of the working gas in both engines, the power of the EHV engine is 20 per cent higher than that of the Stirling engine power. The efficiencies of both engines do not differ significantly from each other.

Performance of Working Fluids for Power Generation in a Supercritical Organic Rankine Cycle

2012 ◽  
Author(s):  
Rachana Vidhi ◽  
Sarada Kuravi ◽  
Saeb Besarati ◽  
E. K. Stefanakos ◽  
D. Yogi Goswami ◽  
...  
Keyword(s):  
Power Generation ◽  
Heat Source ◽  
Thermal Efficiency ◽  
Thermodynamic Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluids ◽  
Source Temperature ◽  
Heat Source Temperature ◽  
Organic Fluids

This paper reports on the performance of various organic refrigerants and their mixtures as working fluids for power generation in a supercritical Rankine cycle (SRC) from geothermal sources. Organic fluids that have zero or very low ozone depletion potential and are environmentally safe are selected for this study. Geothermal source temperature is varied from 125–200°C, and the cooling water temperature is changed from 10–20°C. The effect of varying operating conditions on the performance of the thermodynamic cycle has been analyzed. Operating pressure of the cycle has been optimized for thermal efficiency for each fluid at each source temperature. The condensation pressure is determined by the cooling condition and is kept fixed for each condensation temperature. Energy and exergy efficiencies of the cycle have been obtained for the pure fluids as a function of heat source temperature. Mixtures of organic fluids have been analyzed and effect of composition on performance of the thermodynamic cycle has been studied. It is observed that thermal efficiency over 20% can be achieved for 200°C heat source temperature and the lowest cooling temperature. When mixtures are considered as working fluids, the thermal efficiency of the cycle is observed to remain between the thermal efficiencies of the constituent fluids.

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%.

Dynamic Simulation of a Beta-Type Stirling Engine With Cam-Drive Mechanism

2010 ◽  
Author(s):  
Ying-Ju Yu ◽  
Chin-Hsiang Cheng
Keyword(s):  
Dynamic Model ◽  
Dynamic Simulation ◽  
Rotational Speed ◽  
Friction Torque ◽  
Stirling Engine ◽  
Operating Conditions ◽  
Drive Mechanism ◽  
Mass Moment ◽  
State Regime ◽  
The Individual

Dynamic simulation of a beta-type Stirling engine with cam-drive mechanism has been performed. A dynamic model associated with the cam-drive mechanism has been developed. Upon obtaining the gas pressure inside the chambers, the derived dynamic model is used to evaluate the transient rotational speed of the engine before the steady-state regime is reached. The torque of the engine can be calculated as long as the gas force, the inertia torque, the friction torque, and the load torque are evaluated. In this study, the mass moment of inertia of the flywheel is firstly calculated. The friction torque is assumed to be proportional to the time-varied rotational speed which is obtained by experiments. The weight of the individual parts of the engine has also been considered. An extensive parametric study of the engine under different geometrical and operating conditions has been performed and results are presented.

Improving the Efficiency of Stirling Engines for Use in Solar Distributed Electricity, Heating, and Cooling

2013 ◽  
Author(s):  
Travis M. Schubert ◽  
Shirin Jouzdani ◽  
Kevin P. Hallinan
Keyword(s):  
Heat Exchanger ◽  
Thermal Efficiency ◽  
Effective Means ◽  
Heat Engine ◽  
Stirling Engine ◽  
Future Application ◽  
Film Material ◽  
Expansion Chamber ◽  
Thermal Switch ◽  
Low Mass

Limiting solar power is the inability to cost effectively store energy. The most cost effective means to store solar energy is thermally in the ground, which can then be used for direct conversion to electricity. However, doing so is limited by a historically poor thermal efficiency of such engines. A novel Stirling engine is posed which more closely mimics a Carnot heat engine. It does this through the use of a new passive thermal ‘switch’ which permits heat flow into the expansion chamber of the Stirling engine only when the temperature of the chamber is above a desired value. Ideally heat would be added only at the end of the compression stroke and the beginning of the expansion stroke. Central to this thermal switch is the use of a vanadium dioxide (VO2) low mass heat exchanger internal to the expansion chamber. This low mass heat exchanger allows the film material to track and react to the temperature changes within the expansion chamber, permitting it to transfer heat only when needed. An adiabatic model of this enhanced solar Stirling engine is developed. Results indicate that the thermal efficiency can be nearly doubled, delivering a second law efficiency of over 0.6. Further, a year round overall efficiency accounting for losses in the Stirling engine and solar thermal collectors of 7% appears to be feasible when this engine is integrated with ground solar storage, providing the necessary power to meet loads in a low energy residence. Such results demonstrate promise for future application of this technology.

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