sCO2 Brayton Cycle: P-v & T-s Diagrams (Newton-Solved EOS)

This is the 2D companion to the 3D supercritical-CO₂ Brayton cycle scene, and it reaches the same real-gas conclusion by a genuinely independent computational route. Instead of a closed-form cubic root, it solves the Peng-Robinson equation of state for the compressor-inlet molar volume with Newton-Raphson iteration, cross-checks that result live against an independently-coded closed-form solver, and then does something the 3D scene's single density readout cannot: it plots a full P-v isotherm, sweeping pressure at the current temperature so you can see the real-gas curve bulge away from the ideal-gas line as the compressor-inlet temperature approaches the CO₂ critical point at 31.1 °C / 7.38 MPa. A companion T-s diagram plots the six-station Brayton cycle itself, so recuperation, heat addition and heat rejection all read as visible legs on a real thermodynamic diagram instead of six temperature numbers.