A novel methodology on beta-type Stirling engine simulation using CFD
Abstract
There are no models in scientific literature that satisfyingly simulate the behaviour of real Stirling engines, once that performance prediction models estimate errors above 7%, a barrier to be broken in new engine projects. This work presents a methodology that aims not only to reduce the error in the prediction of the indicated power in beta-type Stirling engines, but also to facilitate extrapolation without the necessity of experimental data. For that, strategies are combined to calculate initial and boundary conditions which are used on a transient simulation in computational fluid dynamics. The first-order model of Schmidt allows to calculate the pressure inside the engine exactly when the power piston is on the bottom dead centre with an average error of 21.3%. The temperature on displacer piston faces can be acquired through a steady-state simulation in CFD (without piston movement). In this methodology, the pressure and the temperature profile are respectively used as initial and boundary conditions for a transient simulation in ANSYS® Fluent, reducing the stabilisation time. The inclusion of the Discrete Ordinates radiation model increases the displacer's frontal face temperature by 132.2 K and results in an indicated power prediction improvement with an error reduction from -14.4% to -2.6% when compared to experimental values. In this way, the presented methodology consists in the combination of first-order mathematical models with CFD simulations, which enables extrapolation for other conditions in beta-type Stirling engines without the necessity of initial and boundary experimental conditions, obtaining an error around -2.6% (2.70 W for experimental and 2.63 W for simulation). Thus, with this methodology, it is possible to design a new project of beta-type Stirling engines through laboratory prototypes enhancing the power accurately.
- Publication:
-
Energy Conversion and Management
- Pub Date:
- March 2019
- DOI:
- 10.1016/j.enconman.2019.01.075
- Bibcode:
- 2019ECM...184..510C
- Keywords:
-
- Beta-type Stirling engine;
- Simulation methodology;
- Experimental tests;
- CFD;
- Radiation model