The hot-gas engine known as the Stirling engine is a promising heat engine with a high efficiency, multi-fuel capability, low emission, quiet operation, very low maintenance requirement and long life. The Stirling engine works by using the pressure p changes resulting from cyclically heating and cooling the enclosed charge gas. The ideal Stirling machines can be considered as a cylinder containing two opposite pistons, with a regenerator between the pistons. One of the two volumes between the regenerator and the pistons is the expansion space (E-space) at a high heater temperature TE. The other one is the compression space (C-space) at a low cooler temperature TC. The engine operates on a closed regenerative thermodynamic cycle, with the same ideal efficiency as the Carnot cycle. In the ideal Stirling engine, as the motion of the pistons is discontinuous, the process of compression takes place wholly in cold space and the process of expansion takes place wholly in hot space. In practice the pistons, connected with crankshaft by means of a wide spectrum of mechanical linkage, move in quasi-sinusoidal mode. Working fluid flow is controlled by volume changes, so that there is a net conversion of heat to work. Both power and efficiency strongly depends on control of volume variations over the engine cycle. This paper presents a new Stirling engine model based on dimensionless analysis. The proposed model assumes sinusoidal variations of hot and cold swept volumes with a phase angle ƒÒ between their minimal values. Other engine control parameters are relative ones, which enable to obtain general directions for rough optimal calibration of wide spectrum of actual Stirling machines. Two constrained optimization problems of two and five parameters are formulated and solved using the model. Maximized criterion ƒ¶ is cycle work per unit of mean pressure and total swept volume. The optimal values of volume control such as phase angle, amplitude ratio of swept volumes are presented for different constraints imposed on temperature ratio and relative dead volumes. The elaborated non-dimensional Stirling model is a suitable tool for preliminary design. The maximization of the index ƒ¶ enables to determine the optimal division of total dead and swept volumes as well as the optimal volume phase angle ƒÒƒx. The obtained results show that volumes (both dead and swept) of hot cells of hot-gas engines should be greater than cold parts. The angle ƒÒƒx approaches ƒà/2 as dead volume increases.
Dimensionless Analysis of Stirling Engine using Optimization Methods / IMPERO ABENAVOLI, Romano; M., Carlini; K., Rudzinska; H., Kormanski. - (2009). (Intervento presentato al convegno International Stirling Engine Conference tenutosi a Groningen, Netherlands nel 2009).
Dimensionless Analysis of Stirling Engine using Optimization Methods
IMPERO ABENAVOLI, Romano;
2009
Abstract
The hot-gas engine known as the Stirling engine is a promising heat engine with a high efficiency, multi-fuel capability, low emission, quiet operation, very low maintenance requirement and long life. The Stirling engine works by using the pressure p changes resulting from cyclically heating and cooling the enclosed charge gas. The ideal Stirling machines can be considered as a cylinder containing two opposite pistons, with a regenerator between the pistons. One of the two volumes between the regenerator and the pistons is the expansion space (E-space) at a high heater temperature TE. The other one is the compression space (C-space) at a low cooler temperature TC. The engine operates on a closed regenerative thermodynamic cycle, with the same ideal efficiency as the Carnot cycle. In the ideal Stirling engine, as the motion of the pistons is discontinuous, the process of compression takes place wholly in cold space and the process of expansion takes place wholly in hot space. In practice the pistons, connected with crankshaft by means of a wide spectrum of mechanical linkage, move in quasi-sinusoidal mode. Working fluid flow is controlled by volume changes, so that there is a net conversion of heat to work. Both power and efficiency strongly depends on control of volume variations over the engine cycle. This paper presents a new Stirling engine model based on dimensionless analysis. The proposed model assumes sinusoidal variations of hot and cold swept volumes with a phase angle ƒÒ between their minimal values. Other engine control parameters are relative ones, which enable to obtain general directions for rough optimal calibration of wide spectrum of actual Stirling machines. Two constrained optimization problems of two and five parameters are formulated and solved using the model. Maximized criterion ƒ¶ is cycle work per unit of mean pressure and total swept volume. The optimal values of volume control such as phase angle, amplitude ratio of swept volumes are presented for different constraints imposed on temperature ratio and relative dead volumes. The elaborated non-dimensional Stirling model is a suitable tool for preliminary design. The maximization of the index ƒ¶ enables to determine the optimal division of total dead and swept volumes as well as the optimal volume phase angle ƒÒƒx. The obtained results show that volumes (both dead and swept) of hot cells of hot-gas engines should be greater than cold parts. The angle ƒÒƒx approaches ƒà/2 as dead volume increases.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
