Simulation of Large State Variations in Steam Power Plants: Dynamics of Large Scale Systems

ISBN-13: 9783540180531 / Angielski / Miękka / 1987 / 110 str.

Richard Dolezal

Opis

The present simulation method has been developed at the Institute for Power Technology and Steam Generation (IVD) of the University of Stuttgart. It is being successfully employed in the analysis of processes involving large state changes such as start-ups, shut downs, malfunctions and failures in steam power generating unit, which is a large scale system consisting of several subsystems with distributed parameters, to which the steam generator also belongs. This research resulted from the increasing use of the once-through boiler, while simultaneously raising the steam parameters into the region of the supercritical state, using sliding pressure operation, combined processes with gas and steam turbines etc. The objective of this system simulation is to reduce losses of heat and condensate and to minimise unavoidable thermal stresses. The project was financed between 1979 and 1983 by the German Research Society (DFG) as part of the special research section Nr. 157 'Thermal power plants'. The Westfalen Power Company Inc. (VEW) sponsored the start-up code 'DYSTAR'. We would like to express our thanks for this support. The following members of the IVD were involved in this research project: Dr.-Ing. J. Kley Dipl.-Ing. G. Riemenschneider Dr.-Ing. A. Rolf Dipl.-Ing. U. Mayer Dipl.-lng. E. Dr.-lng. M. Klug Pfleger Dr.-Ing. G. Berndt Presently it is intended to use this non-linear, time-variant model of a power generating unit with a variable process and system struc ture as the basis for simple code versions, which one can employ e.g."

Spis treści

List of Symbols.- I Non-Linear Time-Variant Model.- 1. Introduction.- 1.1 The Purpose of a Power Plant Unit Model.- 1.2 The Current State of the IVD Mathematical Model and its Practical Realisation.- 1.3 Collaboration with Power Utilities.- 1.4 Objectives of Further Research.- 2. The Limitations of Process Simulation Using Linearised, Time-Invariant Differential Equations.- 3. The Dynamic Behaviour of a Two-Flow Heat Exchanger.- 3.1 Heat Balances.- 4. The Algorithm of Analytical Approximation.- 4.1 Forms of Recuperator.- 4.2 The Analytical Approximation.- 4.3 The Solution of the Differential Equations.- 4.3.1 Initial Conditions.- 4.3.2 Boundary Conditions and Time Segmentation.- 4.3.3 Integration of the Equations.- 4.3.4 Determination of £ with a Two Flow Heat Exchanger…..20.- 4.4 Temperature Net.- 5. Change of the Inlet Temperature in an Unheated Pipe as an Example of a Disturbance on the Hot Water Flow Side.- 5.1 Determination of k.- 5.2 Computed Transient Curves.- 5.3 Comparison with Profos’ Model.- 6. The Decoupled Algorithm.- 6.1 Recuperator and Regenerator.- 6.2 Simulation of a Two-Flow Recuperator.- 6.3 The Decoupling of the Heat Balance.- 6.4 Advantages and Drawbacks of the Decoupled Algorithm.- 6.5 The Dynamics of Two Flow Recuperators as an Example of the Decoupled Computation.- 6.5.1 Parallel Flow Arrangement.- 6.5.2 Counter Flow Arrangement.- 6.6 Decoupling in other Heat Exchanger Types.- 6.6.1 Cross-Flow Heat Exchanger.- 6.6.2 Three-Flow Heat Exchanger.- II Non-Linear, Time-Variant Process Models.- 7. Two Flow Heat Exchanger with a One-Phase Compressible Working Medium Flow.- 7.1 Balance Equations.- 7.1.1 The Mass Balance.- 7.1.2 The Momentum Balance.- 7.1.3 The Energy Balance.- 7.1.3.1 Energy Balance of the Mass Flow.- 7.1.3.2 The Heat Balance of the Thick-Walled Tube.- 8. Two-Phase Flow of the Working Medium.- 8.1 Determining the Local State of the Working Medium.- 8.2 Balance Equations with Wet Steam as the Working Medium.- 8.2.1 The Energy Balance.- 8.2.2 Momentum and Mass Balances.- 8.3 The Heat, Mass and Momentum Balances with Generalised Parameters.- 8.4 Flow Charts of the Code of a Simple Heat Exchanger.- 9. The Direction of the Propagation of a Disturbance in a Boiler.- 9.1 The Momentum Balance of a Segment.- 9.2 ‘Downstream’ Iteration of Pressure.- 9.3 ‘Upstream’ Calculation Procedure.- 9.3.1 Nature of the Process.- 9.3.2 The Flow Chart.- 9.3.3 Turbine Emergency Stop.- 10. Model of the Steam Generator and the Power Generating Unit.- 10.1 Processes in the Steam Generator.- 10.2 Segmentation of the Steam Generator Model.- 10.3 Correlation Table for the Boiler.- 10.4 Process Flow Chart.- 10.4.1 Hot Side (Flue Gas Side).- 10.4.2 Cold Side.- 10.4.3 The Simulation Procedure for the Cold Side.- 10.4.4 Control Loops in the Boiler.- 10.4.5 Temperature Differences in Thick-Walled Component Parts.- III Power Generating Unit and Large State Variations.- 11. Power Generating Unit Model.- 11.1 Power Generating Unit Subsystems.- 11.2 Scope of PGU Simulation.- 12. Starting-Up Process Model.- 12.1 The Starting-Up Procedure.- 12.2 Construction of the Process Model.- 12.3 Cold Start Procedure in Detail.- 12.4 Variable Process and System Structures.- 12.5 Optimisation of the Starting-Up Process.- 12.6 Comparison of the Simulation Results with Measurements.- 13. Malfunctions and Failures.- 13.1 The Purpose of Failure Analysis.- 13.2 The Required Size of a Simulation Code.- 13.3 Quantities to be Analysed in Failures.- 13.4 Frequent Large State Variations in the PGU.- 13.5 Failure of Feed-Water Pump.- 13.5.1 Description of the Unit.- 13.5.2 The Failure Development…..97.- 13.5.3 Failure Recognition.- 13.5.4 Optimal Elimination of the Failure.- 13.6 Turbine Emergency Stop.- References.