Mathematical Modeling and Research of the Low-Potential Part of the TPP Power Unit in the Problems of its Design and Operation

Abstract

The purpose of the work is to create mathematical models and computer programs for solving the problems of designing and operating the low-potential part of the power unit of a thermal power plant (TPP). The tasks of designing the thermal circuit of the TPP power unit are the synthesis of the optimal thermal circuit in terms of structure and parameters in the basic mode of operation and calculations of the circuit in modes other than the basic one. An important task of power unit operation is the training of its personnel. Computer simulators are the effective facilities of such training. Mathematical models of static and dynamic modes of the power unit, which are necessary for the performance of these tasks, were developed using the method of Institute of Mechanical Engineering Problems of the National Academy of Sciences of Ukraine — VNTU of the logic-numerical modeling of power plants (PP). The components of the method are the following techniques: transfer of structural and technological structures of the PP, logical-numerical modeling of physical processes in the PP equipment, identification of mathematical models of the PP equipment, management of software implementation of the PP mathematical model. PP structures are transferred by graphs. Processes are described by the equations in the form of products of numerical and expressive functions. The essence of the identifiable model of the equipment element to determine its characteristics is as follows: 1) the basis of the model is the integral (simplified) method of determining this characteristic; 2) the method is supplemented by a system of identifying equations, the type of which is established on the basis of mathematical processing of the material based on the results of a physical experiment; 3) empirical coefficients in this system are considered average values and may change in specific cases of model implementation; 4.) it is assumed that for this model it is possible to obtain some limited information about the characteristics of the modeled element; 5) the task is to choose the values of the empirical coefficients of the model so that the deviations of the values of the characteristics determined using the model from the known ones are minimal. Model identification based on experimental (calculated or actual) data is performed by the method of least squares. Management of software implementation of the PP model consists of internal and external. Internal management consists in ensuring the functioning of the operator system as a whole (with the codes of nodes and arcs) graph and its information network. Depending on the logical information contained in the technological graph, the expressive functions of the logical-numerical modules take specific values, which results in the formation and solution of a system of equations and inequalities. External control of the independent variables of the mathematical model is performed using their optimization program or from the display screen for variant calculations. According to the mentioned method, mathematical models of static modes of the block for its design and mathematical models of dynamic modes of the block for the computer simulator were developed. Calculation programs for reservoirs and oil coolers have also been developed.

Today, the ambient temperature exceeds the design temperature, which led to underproduction of electricity by the TPP unit. The results of the study of modern hydrological regimes of the reservoir are presented, the expediency of increasing the heat exchange surfaces of the condenser and oil cooler is shown. Economic vacuums in the condenser of the operating unit for the increased, as compared the design values of water temperatures in the reservoir are calculated.

To acquire the skills of managing the equipment of the low-potential part, a training lesson was developed, which is performed on the computer simulator of the unit. The purpose of the training lesson is to start and create a vacuum in a condensing unit. The main tasks of the lesson are to fill part of the inter-tube space of the condenser with water from the chemically treated water supply tanks, supply circulating water from the reservoir to the condenser tubes, and reduce the pressure of the medium in the inter-tube space of the condenser from atmospheric to vacuum. The fulfillment of the tasks of the training lesson is the compliance of the achieved parameters of the condensing unit with their normative values.