Effect of Geometric and Operational Parameters on the Performance of a Beta-Type Stirling Engine: A Numerical Study
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REVIEW PAPER
Effect of Geometric and Operational Parameters on the Performance of a Beta‑Type Stirling Engine: A Numerical Study H. Raghavendra1,2 · P. Suryanarayana Raju1 · K. Hemachandra Reddy2 Received: 5 March 2020 / Accepted: 27 October 2020 © Shiraz University 2020
Abstract This paper describes the development of a mathematical model for a beta-type Stirling engine with rhombic drive mechanism. This model is based on thermodynamics, heat transfer, mass transfer, and machine dynamics considerations, and it estimates the power output and efficiency of a beta-type Stirling engine depending on different geometric and operational variables. The model is used to conduct a parametric investigation on the effect of various geometric and operational parameters on the overall performance of the engine and to shed light on the underlying mechanisms responsible for the observed trends. The results show that the geometric parameters such as the height of the displacer and crank length affect the engine performance by altering the compression ratio of the engine, whereas the impact of width of the regenerative channel is through pumping losses for fluid flow between the hot and cold chambers of the engine. The operational variable, engine speed, is shown to influence the amount of heat transfer to and from the working fluid since it directly affects the residence time of fluid in the hot and cold chambers and accordingly it has a bearing on the engine performance. Keywords Renewable energy · Mathematical model · Stirling engine · Rhombic drive mechanism List of symbols d1 Displacer diameter (mm) d2 Inside diameter of cylinder (mm) G Width of regenerative channel (mm) h Enthalpy (kJ/kg) l1 , l2 , l3 , l4 Link lengths (mm) ld Displacer cylinder length (mm) lt Engine length (mm) L Distance between the gears (mm) Ldt Total length of displacer and its rod (mm) LPt Total length of power piston and its rod (mm) m Mass of the working fluid (kg) ṁ Mass flow rate (kg/s) P Pressure (kPa) Q Volumetric flow rate (m3/s) Qin Input heat transfer per cycle (kJ/cycle)
* H. Raghavendra [email protected] 1
Department of Mechanical Engineering, Madanapalle Institute of Technology & Science, Madanapalle, Andhra Pradesh 517325, India
Department of Mechanical Engineering, JNTUA College of Engineering, Anantapuramu, Andhra Pradesh 515002, India
2
Q̇ in Input heat transfer rate (kJ/cycle) r1 Displacer radius (mm) r2 Inside radius of cylinder (mm) r Radial coordinates R Characteristic gas constant of working fluid (J/ kg k) Rd Crank length (mm) Rt1 Overall resistance to heat transfer between hot source and working fluid in the expansion chamber (°C/kw) Rt2 Overall resistance to heat transfer between cold source and working fluid in the compression chamber (°C/kw) tmax Computation maximum time (s) t Time (s) tP Time period (s) to Reference time (s) T Temperature (k) TH Heat source temperature (k) TL Heat sink temperature (k) U Internal energy (kJ/s) V Volume (m3) v Velocity (m/s) Ẇ out P
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