An ideal air standard cycle analysis of the solar chimney power plant gives the limiting performance, ideal efficiencies and relationships between main variables. The present paper includes chimney friction, system, turbine and exit kinetic energy losses in the analysis. A simple model of the solar collector is used to include the coupling of the mass flow and temperature rise in the solar collector. The method is used to predict the performance and operating range of a large-scale plant. The solar chimney model is verified by comparing the simulation of a small-scale plant with experimental data. [S0199-6231(00)00503-7]

This project investigates the performance of solar chimney power plant turbines. A solar chimney power plant consists of a tall chimney surrounded by a transparent deck or solar collector. The sun heats the air in the collector through the greenhouse effect. A turbine extracts energy from the hot air rising up the chimney. An investigation of the requirements and operation of such turbines is needed.Correct matching of the turbine to the plant requires the determination of the turbine operational range and other requirements. An air-standard cycle analysis is extended to include component and system losses. Simple steady-state and transient collector models are added to take into account the coupling effect of the collector air temperature rise and mass flow rate on the turbine operation. The predicted turbine operational range for a representative day shows that the expected pressure drop in a full-scale solar chimney turbine is significantly higher than has previously been predicted.A turbine design method is developed and used to design a turbine for the representative day. The methods can easily be extended to include more operating points for a full year of operation. A turbine layout is suggested that uses the chimney support pillars as inlet guide vanes (IGVs). These introduce pre-whirl to the turbine and reduce the amount of exit whirl thus decreasing the kinetic energy at the turbine exit. Non-radial inlet guide vanes add to the torsional stiffness of the chimney base. A matrix throughflow method is used to design the radial to axial duct between the IGVs and rotor. The turbine blade profiles are simulated using a surface-vortex method. This is coupled to an optimisation scheme that minimises both the chord length and maximum flow velocity of the profile to reduce blade drag.An experimental program investigates the performance of the turbine. Volume flow, pressure drop, torque and speed are measured on a scale model turbine to map the turbine performance over a wide range. The velocity and pressure profiles are measured at two design points to investigate the flow through the turbine in more detail. These are compared to the design predictions and used to improve the design method. The experiments show that the design of a solar chimney turbine with a total-to-total efficiency of 85 % -90 % and total-to-static efficiency of 75 % -80 % is possible.

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Chimneys as tall as 1500 m may be important components of proposed solar chimney power plants. The exit air density will then be appreciably lower than the inlet density. The paper presents a one-dimensional compressible flow approach for the calculation of all the thermodynamic variables as dependent on chimney height, wall friction, additional losses, internal drag and area change. The method gives reasonable answers even over a single 1500 m step length used for illustration, but better accuracy is possible with multiple steps. It is also applicable to the rest of the plant where heat transfer and shaft work may be present. It turns out that the pressure drop associated with the vertical acceleration of the air is about three times the pressure drop associated with wall friction. But flaring the chimney by 14 percent to keep the through-flow Mach number constant virtually eliminates the vertical acceleration pressure drop. [S0199-6231(00)03003-3]

In an attempt to reduce engine frontal area, while maintaining a high single stage pressure ratio, mixed flow compressor stages are frequently used in micro gas turbine (MGT) engines. The expansion of the choke margin of such a mixed flow compressor is presented. The use of a crossover diffuser configuration in a mixed flow compressor stage has displayed superior performance results compared to legacy diffuser configurations, especially when geometric restrictions are enforced. A disadvantage of a crossover diffuser configuration is that it typically displays an inferior operating range compared to legacy diffuser configurations. In an attempt to expand the choke margin of a MGT mixed flow compressor, the use of tandem and splitter vane crossover diffuser configurations was evaluated. It was found that a low solidity first vane row configuration provided a 3% increase in choke margin. A splitter vane crossover diffuser configuration provided a 5.9% increase in choke margin. A tandem vaned diffuser with a reduced first row vane number provided a 7.8% increase in choke margin.