Domain: Engineering — Energy Engineering
Target concept: Two identical Stirling engines, one with an insulated hot end, compared by rotational speed

Video generation prompt: Two identical desktop Stirling engines are placed side by side; the hot cylinder on the left is insulated, while the one on the right is exposed. Identical burners are ignited simultaneously beneath both hot ends.

Evaluation guide:
(i) Target concept: Thermal resistance governs steady-state power output in identical Stirling engines under equal heating input.
Minimum mechanism: Working gas must undergo cyclic expansion/contraction driven by temperature difference; insulation impedes heat flow into hot space, lowering dT/dt and peak ΔT achievable at steady state; exposed hot cylinder enables faster heat conduction, sustaining higher ΔT and thus greater pressure swing and torque.
(ii)Storyline: Frame 0–1: Static shot showing two identical engines side-by-side, left hot cylinder wrapped (dull, non-reflective), right hot cylinder bare (shiny metal), two identical burners unlit beneath. Frame 2–3: Simultaneous flame ignition under both burners (flames appear in same frame or adjacent frames with no visible lag). Frame 4–10: Continuous rotation of both engines; left crank/flywheel motion visibly slower in angular displacement and frequency than right; insulation remains intact, bare metal remains uncovered; no extraneous motion, occlusion, or lighting disruption; viewpoint remains fixed, frontal, and level.

Manual:
Experimental Procedure
1. Place two identical desktop Stirling engines side-by-side on a stable surface.
2. Wrap insulating material fully around the hot cylinder of the left engine; leave hot cylinder of right engine bare.
3. Position identical burners directly beneath each hot cylinder.
4. Ignite both burners simultaneously.
Observation of Experimental Phenomena
Left engine rotates slower than right engine; rotational speed difference is visually sustained after ignition.
Summary of Experimental Principles
Insulation reduces heat transfer rate to working gas in left engine → lower temperature gradient across engine → reduced pressure differential → lower net work per cycle → slower rotational speed. Right engine, with exposed hot cylinder, achieves higher thermal conduction → larger temperature gradient → greater work output → faster rotation.

Prompt Grounding rubric:
level_1: Fewer than two Stirling engines are shown, or the two engines are not both visible together in the same frame side by side, or no burner is visible beneath one or both hot cylinders, or the left hot cylinder is left completely bare with no insulating wrap at all, or the right hot cylinder is wrapped in insulating material to roughly the same extent as the left (so the two hot ends cannot be told apart by insulation), or one burner is still completely unlit while the other has already been burning for an extended stretch of the shown sequence.
level_2: Two Stirling engines are shown side by side, but the setup is only partly correct: for example, the left hot cylinder has some insulating material yet a large portion of bare metal is still exposed (partial rather than full coverage), or the right hot cylinder (while still clearly mostly bare metal, unlike the left) carries a small extra strip, tag, or patch of insulating-looking material on part of its surface, or the two burners are visibly mismatched in size or flame-tip shape, or both flames do ignite but with a short, perceptible gap between them (on the order of a second or two) rather than together.
level_3: Two Stirling engines of matching size and flywheel design sit side by side in the same frame; the left engine's hot cylinder is fully wrapped in a distinct insulating material (e.g., a dull fibrous or ceramic sleeve); the right engine's hot cylinder is bare, reflective metal; a burner sits directly beneath each hot cylinder; both flames appear together in the same frame (or within an imperceptibly short gap), matching the prompt's simultaneous-ignition setup.
level_4: Everything described for score 3 holds, and in addition the insulating wrap on the left cylinder is clearly different in color and texture from the bare metal on the right (e.g., matte gray sleeve versus polished chrome), the two starting flames are matched in height and color at the moment of ignition, and the insulation is fitted to seat fully around the left cylinder with no visible gap that exposes bare metal underneath.
level_5: Everything described for score 4 holds, and in addition the left cylinder's insulation shows no torn seams or slipped sections, the right cylinder shows no trace of insulating material or residue anywhere on its surface, both burners are centered directly under their respective hot cylinders with no visible lateral offset, and the two engines are framed at matching scale and distance from the camera so their construction can be compared directly.

Scientific and Causal Correctness rubric:
level_1: No rotational motion is visible in either engine; or both engines spin at visually indistinguishable speeds throughout; or the left (insulated) engine's flywheel rotates faster than, or keeps pace with, the right (exposed) engine's flywheel for the entire period both are visibly spinning; or rotation is already underway before either burner's flame appears, showing the motion has no thermal trigger.
level_2: Rotation begins only after both flames appear, and the right engine's flywheel starts out faster than the left's as expected, but at some point during the visible sequence one flywheel's motion stalls (freezes for a beat) or briefly runs in reverse before resuming (an unexplained interruption distinct from a steady, consistent speed difference), so the overall pattern cannot be trusted even though the direction was correct at the start.
level_3: Both flywheels stay still until their own burner's flame appears, then begin turning without freezing or reversing; from that point on, the left engine's flywheel and crank visibly turn slower than the right engine's throughout, and this insulated-left/exposed-right ordering never reverses or stalls during the visible sequence.
level_4: All conditions for score 3 satisfied, AND the left-slower/right-faster relationship holds without a single momentary tie anywhere in the sequence, AND the slower rotation is always seen at the insulated left cylinder while the faster rotation is always seen at the bare right cylinder: the speed and the insulation state never swap engines.
level_5: All conditions for score 4 satisfied, AND the speed gap is large and unambiguous (for instance, the left flywheel completes less than half a turn in the same interval the right flywheel completes a full turn or more), no single frame shows the two speeds crossing over or tying, and the increase in speed visibly tracks the flame and heating rather than any sudden unexplained jump, push, or external disturbance.

Spatiotemporal Consistency rubric:
level_1: One or both Stirling engines disappear from the shot or are replaced by a different object partway through; either engine's position or facing suddenly jumps between two frames with no in-between motion; a burner's flame appears or vanishes within a single frame with no partially-lit transition; a hot cylinder or flywheel visibly bends, stretches, or loses its rigid shape; a flame's brightness or color jumps sharply between adjacent frames while the flame's size stays the same, with no matching change at the burner; or the overall scene lighting abruptly swings from bright to dark (or the reverse) with no connection to either burner igniting.
level_2: One engine flickers out of view or drops out for a noticeable burst of frames and then reappears in the same spot; smoke or flare briefly covers a burner and the burner is never shown again afterward; the tabletop or background changes texture, color, or position partway through the sequence; or there is a visible cut where the shot jumps discontinuously to a different moment.
level_3: Both engines stay fully visible and remain planted in the same spot on the table for the whole sequence: only the crank arm, flywheel, and displacer rod rotate, while the engine housings themselves never slide, tip, or relocate; once lit, each burner's flame stays continuously present without dropping out; neither hot cylinder bends or changes shape; the shadows cast by the two flames and by the engine bodies point in one consistent direction and keep a steady softness across the sequence; the tabletop and background stay static.
level_4: Everything described for score 3 holds, and in addition the rotating parts (crank arm, flywheel, displacer rod) turn with smooth, continuous motion with no freezing on a single frame and no juddering; both burner flames flicker naturally by a similar amount; each engine's crank/piston linkage stays coaxial with its own cylinder rather than drifting sideways out of alignment; and both engines hold the same on-screen size, orientation, and framing relative to the camera as at the start, with neither engine appearing to zoom, rotate as a whole, or drift relative to the other.
level_5: Everything described for score 4 holds, and in addition the motion blur trailing each flywheel visibly scales with its own turning speed (the faster right flywheel shows more blur than the slower left one, never equal or reversed blur), each flame base stays centered under its hot cylinder without lateral creeping, there is no parallax shift between the two engines that would indicate camera movement, and every rotating part stays mechanically linked (the crank never separates from the flywheel, with no component floating free of its housing).