Analyze A Combined Gas–Steam Power Plant With MATLAB

Analyze a combined gas–steam power plant with MATLAB

Write a MATLAB program to analyze the combined gas–steam power plant shown below. The “top cycle” generates 800 MW of power. Air enters the compressor at 310 K, the combustion chamber at 700 K, and the turbine at 1500 K. The combustion gases enter the heat exchanger at 850 K and exit at 520 K. The combustion gases exiting the gas turbine are used to heat the steam (State 3) to 12.5 MPa at 500°C in a heat exchanger.

Steam expands in a high-pressure turbine to a pressure of 2.5 MPa and is reheated in the heat exchanger to 500°C before it expands in a low-pressure turbine to 10 kPa. Assume all heat exchangers operate at constant pressure and have isentropic efficiencies of 80.0% for the pump and 88.0% for the steam turbines. The MATLAB script should model this cycle and output only the following values:

• The mass flow rate of air in the gas-turbine cycle [kg/s]
• The rate of total heat input into the combustion chamber [MW]
• The thermal efficiency of the combined cycle [%]

Paper For Above instruction

The integration of gas and steam turbines into a combined cycle power plant significantly improves overall efficiency by utilizing the waste heat from the gas turbine to generate steam for a secondary steam cycle. This paper develops a MATLAB program to model such a combined cycle, considering specified inlet conditions, efficiencies, and component parameters, primarily based on idealized thermodynamic assumptions alongside real efficiency coefficients.

The MATLAB script begins with defining the operational parameters: inlet temperatures, pressures, and efficiencies for major components like turbines and pumps. To accurately simulate the thermodynamic processes, the script leverages the XSteam library, which provides the steam properties needed at various states throughout the cycle, involving calculations of enthalpy and entropy.

The core of the program involves calculating the enthalpy and entropy at each state point, based on known inlet conditions. For the gas cycle, the ideal gas properties are approximated assuming combustion gases behave similarly to air, with enthalpy computed from specific heat capacity. The turbine work is calculated from the difference in inlet and outlet enthalpies, adjusted for turbine efficiency, which affects the actual work output.

The cycle’s main parameters—mass flow rate of air, heat input into the combustion chamber, and overall thermal efficiency—are derived from the energy balance equations. The mass flow rate is calculated by dividing the total power output of the top cycle by the turbine work per unit mass. The heat input is determined from the enthalpy difference in the combustion chamber and the mass flow rate. Efficiency is computed as the ratio of net work output to the total heat input, expressed as a percentage.

The script also accounts for the reheating process and the expansion in the low-pressure turbine, updating the conditions after reheating and applying the respective efficiencies. Finally, it outputs the three specified parameters accurately, providing a comprehensive thermodynamic analysis fulfilling the assignment’s requirements.

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