International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 05 | May -2017
p-ISSN: 2395-0072
www.irjet.net
Design of Experiment Technique for Improving the Performance of Stirling Engine S. Venkatesh1, I. Bruno clement 2, M. Avinasilingam3, E. Arulkumar4
1Assistant
professor, Mechanical Engineering, Sri Eshwar College of Engineering, Coimbatore. 2Bimetal bearings limited, Coimbatore. 3.4 UG Scholars, Mechanical Engineering, Sri Eshwar College of Engineering, Coimbatore.
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Abstract - The aim of this design is to improve the
type Stirling engine, beta type Stirling engine, and gamma type Stirling engine. Alpha type Stirling engine consists of two power pistons whereas beta and gamma type Stirling engines consists of one displacer and one power piston.
performance of Stirling engine. Stirling engine performance is mainly identified by its efficiency. The efficiency of Stirling engine is affected by many parameters such as total swept volume, temperature of the hot source, the dead volume ratio, the temperature ratio, and phase angle, area of the displacer section, exchanger piston conductivity, and regenerator effectiveness. Among all these parameters, the ones which critically influence the efficiency of Stirling engine is identified and is optimized with the help of design of experiment technique. The obtained results show that the optimal values of identified parameters increases the efficiency of engine by 2% comparing to other optimal values. A new design is proposed relating to the obtained optimal values and a prototype is fabricated.
1.1 Study of Various Parameters of Stirling Engine The performance of the Stirling engine depends on many thermal and geometrical parameters. These parameters differs by their influence on the efficiency of Stirling engine, therefore a detailed study is carried out to identify the parameters which have critical results over the efficiency of the Stirling engine. According to Cheng and Yang [2] an optimal combination of phase angle and swept volume ratio increases the shaft work of the engine. Effects of the dead volume ratio, temperature ratio to increase the efficiency of the engine are studied. According to Cheng and Yang [2] the shaft work of the engine increases only when the swept volume ratio is in the region of low temperature ratio. In the swept volume region there lies a critical value. Over this critical value of swept volume ratio the shaft work of the engine begins to vary inversely. On increasing the swept volume ratio the shaft work of the engine increases till the critical value. After this critical value of swept volume ratio the shaft work of the engine decreases. This indicates that an optimal value of swept volume ratio is needed to increase the performance of Stirling engine. The effect of phase angle result in the variation of the shaft work. Therefore an optimal phase angle is needed for getting the optimal shaft work. The values of the optimal phase angle mentioned [2] are 30˚ for α-type, 80˚ for β-type and 100˚ for γtype, these optimal values can also be referred to the values according to the results given by Kirkley [3] and Senft [4]. It is stated [2] that the shaft work attains a peak value for the βtype Stirling engine and for γ-type Stirling engine the shaft work is the least. The parameter temperature ratio vary the performance of Stirling engine. The temperature difference between the regions of expansion and compression gets decreased as the temperature ratio is elevated. As the temperature ratio attains a critical value the shaft work of engine suddenly decreases, drops to zero and even gets vanished as it progresses. This critical value of temperature ratio is low. With this low temperature ratio only the γ-type engine is most suitable to produce the shaft work comparing to other types α- and β-type engines [2]. The temperature ratio represents the ratio of the temperature in compression region to the expansion region [2]. Actually the temperature ratio depends on engine speed, regenerator effectiveness, mass of
Key Words: Stirling engine, Performance, Parameters, Design of experiment, Taguchi
1. INTRODUCTION Stirling engine is a simple external combustion engine which uses the heat to produce work. A simple Stirling engine consists of a heat source, displacer cylinder, power cylinder, displacer, power piston, transfer tubes and a flywheel with connecting rods connected to displacer and the power piston. The working fluid can be air, hydrogen or helium. The concept is that the thermal heat from heat source is used to heat air in the displacer cylinder. Due to thermal expansion the pressure of air increases. This increasing pressure of air pushes the displacer forward and gets transferred to power cylinder through the transfer tubes and in turn the power piston in the power cylinder is also pushed forward. In the compression area of the cylinders the pressure of air decreases, gets compressed and is again retarded back to the expansion area of the cylinders. This concept makes the displacer and power piston to move in and out of the engine and a mechanical motion is produced. This mechanical motion is used to produce the desired work. This is how a simple Stirling engine works. An ideal Stirling cycle consists of four thermodynamic processes: Isothermal compression process, constant volume process with heat addition, isothermal expansion process and constant volume process with heat rejection. Based on different mechanical configurations Stirling engine is classified into three types [1]. They are alpha
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