A parcel of air rides the whole engine, with the gas laws computed live
This is an isometric cutaway of a turbofan jet engine mounted on a test stand. A single glowing parcel of air leaves the Intake and rides the engine's own centreline through the Fan, a Compressor stage ring it laps once per stage, the Combustor -- where a second, golden fuel token flies in and merges with it -- the Turbine, and finally the Exhaust Nozzle. Click the parcel's station labels for the write-up, or just watch: every station it passes recomputes its pressure, temperature and speed from scratch.
The parcel's glow colour is its actual temperature. Its size is its actual pressure. The short trail behind it is its actual speed. None of the three is decoration; all three are read straight out of the model each time a station fires.
Genuinely computed, live, in your browser: isentropic compression through
the fan and every compressor stage, each with its own efficiency; the combustor's
temperature rise from a straight fuel-energy balance, capped at a turbine-inlet material
limit; the turbine's temperature drop, fixed by exactly how much shaft work the fan and
compressor are drawing; real choked-nozzle gas dynamics, including the critical-pressure-ratio
check that decides whether the jet chokes at Mach 1 or fully expands; the nozzle exit area
from the continuity equation; and the thrust equation itself, mass flow times exit velocity
plus the pressure term when choked. Dragging Throttle or Compressor stages recomputes every
downstream station from these formulas -- nothing is interpolated. It is all in
js/model.js, about 230 lines, worth reading on its own.
Scaled down: mass flow runs 12-26 kg/s and thrust tops out in the tens of kilonewtons, both a small-engine scale rather than a wide-body turbofan's several hundred kg/s and several hundred kilonewtons. The stage slider maxes out at 10; real multi-spool compressors split 8-14 stages across two or three independently spinning shafts.
Assumed: every component efficiency (fan, compressor stage, turbine, nozzle), the fan and per-stage pressure ratios and how they rise with throttle, the combustor's pressure loss, the turbine-inlet temperature limit, and the station Mach numbers used only to convert the cycle's total conditions into the static numbers a travelling parcel would read. No engine manufacturer publishes these for a specific engine; this model uses textbook-typical figures for an engine of this size class.
Deliberately simplified: there is no separate bypass duct. A real high-bypass turbofan sends most of its intake air around the core through the fan alone, and that bypass stream -- not the core -- produces most of a real turbofan's thrust. This simulation sends all of the flow through the core so there is exactly one parcel to follow from Intake to Nozzle; see the Fan write-up. It is also a single-spool model: the fan and every compressor stage share one shaft, where a real large turbofan splits low- and high-pressure sections onto independent shafts at different speeds.
Scenery: the casing shapes, the test-stand struts, the fuel tank and the crates are illustrative, not measured from a real engine drawing. Treat the engine as an illustration and the numbers on the panel as the lesson.
The first time the parcel reaches a station it stops for long enough to read that station's write-up -- between 9 and 26 seconds -- and a progress bar under the panel text shows how much of the stop is left. The compressor's ten possible laps share a single write-up: only the first lap gets the long stop, the rest get a short beat so you can watch the stage count and the pressure climb without re-reading the same paragraph ten times. Space holds any stop indefinitely, S steps one station at a time, and the Speed slider scales everything, reading stops included. Reset (⟲) replays the slow tour; Run keeps what you have already read.
Built from the isometric-explainer skill. All code and copy original.