From turbo-machines to solar chimneys

[摘要] ENGLISH ABSTRACT: This dissertation is basically a summary, with some interpretation, of published researchby the author. The scope is limited to the fields of turbo-machinery, computational fluiddynamics and solar chimney power plants.The main contribution in the field of turbo-machinery in general is in the developmentof a through-flow method that automatically satisfies mass conservation. Concerningfan design, the contributions are the realization of the importance of the exitkinetic energy in the determination of the efficiency of rotor-only axial flow fans, andthe quantification of the effect of off-axis inflow into cooling system fans on their performance.In the field of centrifugal fans and compressors an original, unifying modelfor the prediction of slip factor was developed. To investigate accident scenarios inclosed cycle gas turbine nuclear reactors, all possible operational modes of multi-stageaxial compressor operation caused by flow and rotation direction were investigated experimentallyand computationally. Spanning the fields of turbo-machinery and solarchimneys, the basic theory of solar chimney turbines was developed, showing that highturbine efficiency was possible.In the field of solar chimneys, an original thermodynamic approach was developedto predict the main relationships that govern solar chimney performance, and to solvethe through-flow equations for non-ideal systems with losses. Equations for the accuratedetermination of all the thermodynamic variables in a solar chimney as dependent onchimney height, wall friction, additional losses, internal drag and area change werederived and solved. Coefficients of wall friction, bracing wheel loss and exit kineticenergy were determined experimentally, and empirical equations were developed topredict the loss coefficient of the collector to turbine transition section and and theturbine inlet flow angle. A simple power law approach allowed the calculation of theoptimal turbine pressure drop in solar chimney power plants. A comparison of two setsof equations used to calculate the heat fluxes into, inside and leaving the solar collector,resulted in similar air temperature rises in the collector, and similar produced power.It turned out however that the optimal flow for minimal turbine pressure drop wasdependent on the heat transfer models.Investigation of the performance of various solar chimney turbo-generator layoutsusing analytical models and optimisation techniques showed that the optimal numberof turbines varies with plant size, but the individual turbine size, the number of bladesand even the efficiency remains close to constant. It was found that the cost of a turbogeneratorsystem, however, varies significantly with size. A joint paper with severalGerman universities and institutions did a comparative cost analysis of solar chimneypower plants

[发布机构] Stellenbosch University