Optimal Thermal Control of a Chamber Furnace

Abstract

When using local automatic control systems, the temperature and excess pressure of the hot gas in a chamber furnace are generally chosen independently, without regard for their interrelationships. At the same time, regulation of the fuel and air consumption involves changes in not only the temperature but also the pressure in the furnace chamber. That, in turn, changes the gas transfer with the surroundings and has a considerable influence on the temperature in the working chamber. As a result, the combustion of the gaseous fuel is excessive, and consequently furnace operating costs are increased unnecessarily. With constant volume of combustion products in such furnaces, control of the thermal power entails combining different components of the gaseous fuel with specified temperature in the working volume. On the basis of Bellman dynamic programming, the control of the heat-treatment cycle in the furnace may be optimized by selecting the optimal fuel composition (in terms of fuel cost) for each quantization period. The fuel cost is regarded as a linear function of the mean consumption of the individual fuel components in the quantization periods. Its minimum value for each instant is found by linear programming. An algorithm is developed for determining the optimal consumption of individual components of the gaseous fuel and also the consumption of the excess air, which is used in automatic control of the temperature and excess pressure of the hot gas within the working volume of the furnace. The proposed automatic control system not only permits optimization of the heating process in terms of the cost of the individual fuel components but also ensures autonomous control of the temperature and excess pressure of the hot gas in the working volume of the chamber furnace. With real-time control and cost optimization of the fuel components, the system is self-adjusting.