NPSS cycle solver: residual convergence without a documented positive mass-flow guard

NPSS closes an off-design thermodynamic cycle by driving residual and target equations to zero with an iterative solver. The documented stopping rule is a residual tolerance combined with an iteration limit, not a test for physical feasibility. This means the solver can report convergence at a mathematically valid but non-physical root—for example, non-positive mass flow or pressure—depending on the initial guess and solver settings.

The configuration surface that matters is the solver tolerance and iteration controls together with user-supplied initial guesses. No single documented switch guarantees a physically valid operating point for every cycle. A desired behavior would be an optional per-variable bound or residual guard that rejects iterations producing non-positive mass flow or pressure, so that convergence implies feasibility. Whether such a guard exists as a documented default or configurable option is release-sensitive and must be confirmed against the manual for the installed NPSS version.

• Are per-variable bounds or feasibility guards documented in the current NPSS release for off-design cycle solvers?
• If not, is the only mitigation to supply physically plausible initial guesses and post-check converged mass flows and pressures?
• Which manual section or configuration block defines the exact stopping rule and any available physical-bound options for a specific NPSS version?