Contribution on the Calculation of Gas Turbine Air Heaters Fired With Gas-Coal Mixtures

The design of heaters for closed-cycle gas turbines is different from that of steam generators. The main difference is found in the layout of combustion chambers; it is caused by the working fluid, the heat-transmission coefficient attainable in the tubes, and by the permissible pressure drops. The exact calculation of the heat transmitted in the combustion chamber and of the irradiation curve is a prerequisite for the economical layout of the heater combustion chamber. As suitable calculation methods were not known, the required basis was worked out by subjecting a mine-gas and pulverized-coal-fired combustion chamber of an existing plant to extensive tests. The paper deals with the test plant and the tests carried out. With the test results obtained at this and similar plants the correctness of calculation methods known for determining the heat transmission in pulverized-coal-fired combustion chambers was investigated. For the calculation of heaters, the Wohlenberg method is supplemented by taking higher heating-surface temperatures into consideration. A new method for calculating the irradiation curve in the combustion chamber is shown.