(An) implementation of a numerical model for dynamics simulation in large boilers and its application

Abstract

A major objective in boiler design is maximization of thermal efficiency of the system under imposed load requirements. Although the design is based on a boiler``s performance during steady state operations, a boiler , in fact, operates under a series of transient conditions such as daily load demand changes. Moreover, a modern large boiler operates at high pressure and temperature and its design margin is narrow. Thus, a boiler should be validated for intended or unintended transients, whether it reliably follows load changes and remains in safe operation limits. To predict a boiler``s transient behavior quantitatively, a model should be provided by experiments or numerical analysis, and should reproduce physical phenomena in real operation. In large boilers, it is difficult to reproduce experimental conditions or to build down-scale facilities. Therefore, a numerical prediction using mathematical models based on basic conservation rules is preferable. There are a number of work on establishing numerical models for boiler``s behavior. The work has a variety of complexities depending on model``s details, simplification levels, and numerical solution methods. Most of the work adopts similar equations, and the models can be constructed by repetitive applications of basic conservation rules. However, most of the work emphasizes formulation or numerical analysis of their specific systems, and they lack a systematic procedure for establishing mathematical models and a consideration on a general structures of a numerical models. In this work, a mathematical model is established for a large steam boiler, which occupies a major part in the production of heat and/or electricity. Transient behaviors of a boiler are simulated with this model. A boiler is decomposed into a few of commonly used components according to their functions and physical processes. Generalized component models are built with some simplifications. If necessary, dynamic characteristics of component m...