Engine Cycles Compared (P–V)
This page is a **single P–V canvas** with a **dropdown** to load **Carnot**, **Otto**, **Diesel**, **Stirling**, or a **Rankine P–v sketch**. Gas cycles reuse the **same closed-form geometry** as the dedicated labs: **nR = 1**, **γ = 1.4**, Carnot/Stirling isotherms in kelvin, Otto/Diesel air-standard legs. **Rankine** replays the **qualitative four-corner loop** from the Rankine simulator (normalized ṕ sliders and turbine quality **x₄**), **not** steam-table volumes. The plot **auto-scales** axes to the active cycle so each loop is readable; **numeric P and V are not a universal calibration** across cycle types. Displayed **η** matches textbook formulas for the gas cycles; for Rankine it is a **rough area-based proxy** for teaching only.
Who it's for: Students who have met individual cycle pages and want side-by-side shape comparison without juggling browser tabs.
Key terms
- P–V diagram
- Carnot cycle
- Otto cycle
- Diesel cycle
- Stirling cycle
- Rankine cycle
- thermal efficiency
- auto-scale axes
How it works
Switch among **Carnot**, **Otto**, **Diesel**, **Stirling**, and a **Rankine P–v sketch** on one canvas. **Four colors** trace the loop in **parametric order** (0–25%, 25–50%, …); the physical meaning of each segment depends on the cycle (e.g. Carnot starts on the **hot isotherm**, not compression). Gas cycles match the standalone labs (**nR = 1**, **γ = 1.4**); Rankine is a **qualitative** sketch.
Frequently asked questions
- Why do the axis numbers jump when I change cycles?
- Each cycle is drawn in its own natural model units with automatic padding. The goal is to compare **shapes** and **process labels** (colored legs), not to read one universal pressure-volume scale across engines.
- Is Rankine here as accurate as the full Rankine page?
- No. Only the **P–v cartoon** is shared; the T–s dome and enthalpy-based discussion stay on the Rankine lab. Efficiency on this page is an illustrative ratio, not a plant heat balance.
- Does Stirling really reach Carnot efficiency?
- The **ideal** Stirling with a **perfect regenerator** and reversible isothermal/isochoric legs has the **same efficiency limit** as Carnot between the same reservoirs. Real machines have losses and imperfect regeneration.
More from Thermodynamics
Other simulators in this category — or see all 24.
Diesel Cycle (PV)
Air-standard: adiabat compress, isobaric heat, adiabat expand, isochoric out; η(ρ_c, β).
Maxwell’s Demon (Toy)
2D billiards + gate: fast |v| crosses; ⟨|v|⟩ left/right + Landauer note.
Leidenfrost Effect (Toy)
T_plate vs ~200 °C threshold: vapor gap and lifetime curves — pedagogical, not measured boiling data.
Peltier & Seebeck (Schematic)
Current pumps heat across junction; ΔT drives toy mV — same couple, two modes.
Joule Expansion
Ideal gas into vacuum: Q = W = ΔU = 0; ΔS = nR ln 2 when volume doubles.
2D Ising Model
Square lattice Metropolis: kT/J vs |m| and E; T_c ≈ 2.27; optional field h.