A STEADY POINT DOES NOT TELL THE WHOLE STORY.
Follow the rotor energy during acceleration, then inspect a separate compression system where duct inertia and plenum storage can produce surge.
Turbine work must supply compressor work, accessory power and the change in rotor kinetic energy.
Whole-run summary · live values appear above
CAUSE → RESPONSE → COMPARISON
B · solid turquoise A · dashed amber
Time plots share the playback cursor. Design sweeps and phase plots retain their own axes. A stopped run holds its final resolved state.
| Whole-run quantity | A · saved | B · live | B − A | Unit |
|---|
A snapshot includes parameter values and event times. Export retains both configurations and their calculated traces.
THE PHYSICS BEHIND THE RESPONSE
Follow each balance, then connect it to the response above. Open Symbols & units for the notation. A dot denotes a time derivative unless a non-dimensional time is stated.
Turbine power first pays the compressor and accessory demand. The remaining power changes the rotor’s kinetic energy.
Bleed leaves before combustion. Fuel adds both mass and chemical energy; the remaining gas must match the fixed turbine and exhaust areas.
In the separate Greitzer model, duct inertia changes flow and plenum storage changes pressure. This view does not calculate a complete engine transient.
The signed algebraic throttle relation permits reverse flow. Increasing resistance changes the operating point and can destabilise the reduced model.
Equations describe this bounded teaching model. Assumptions and source references are retained below. Internal calculations use SI units; controls and plots show their own labelled units.
Generic sea-level static single-spool engine; reference angular speed 1500 rad/s, initial 70%, compressor efficiency 0.86, turbine 0.90, mechanical/burner efficiency 0.99, accessory load 30 kW. Turbine throat 0.03 m²; exhaust nozzle 0.08 m². Constant gas properties. Compressor map and acceleration fuel schedule are synthetic; turbine must remain choked. Stop at 40–112% speed or T4 > 1850 K. Separate two-state Greitzer model uses Ψc = 0.30 + 0.18[1 + 1.5(φ/0.25−1) − 0.5(φ/0.25−1)³], an instantaneous synthetic map and algebraic throttle. No spatial stall cell, reverse-flow engine thermodynamics, combustor flame model or manufacturer limits.
NASA · Engine transient analysis ↗NASA · Compression-system transients ↗Greitzer · Compression-system model ↗Numerical checks test the stated equations. They do not establish aircraft certification or experimental accuracy. Schematic flow markers indicate direction; their speed is illustrative. No manufacturer geometry or performance data is reproduced. Version: coupled-labs-v1.1.