How to run a cycle 01 Choose the layer. The tab bar switches between Ideal gas and Real fluid; each layer has its own route, /engineering/cycles/ideal and /engineering/cycles/real. 02 Set the state and the cycle parameters. Ideal cycles share a working fluid, inlet temperature T₁ in kelvin and pressure p₁ in kPa; each tab adds its own fields — r and q_in for Otto and Atkinson, r and r_c for Diesel, r_p, T₃ and loss settings for Brayton, T_h and T_c for Carnot and Stirling. 03 Read the cards before the curves. Efficiency, the Carnot bound, net work, heat in/out and mean effective pressure sit above the state table and the P-v / T-s plots; a strip below repeats Atkinson, Otto and Diesel at the same r and heat input. 04 Drive the real-fluid cycles. Rankine opens at 3 MPa / 350 °C → 75 kPa, with optional reheat or one open feedwater heater (reheat wins); refrigeration and heat pump share one R134a cycle. Add a mass flow or cooling load for kW/MW, or load CoolProp for REFPROP-grade properties. Worked readouts All readouts are the panel's own display.
Input
Displayed readouts
Otto: r = 8, T₁ = 300 K, p₁ = 100 kPa, q_in = 1800 kJ/kg
η 56.472% , Carnot bound 90.619% , w_net 1,016.5 kJ/kg , MEP 1,349.3 kPa , state 3 3197.91 K
Diesel: r = 18, r_c = 2
η 63.158% , w_net 604.8 kJ/kg
Brayton: r_p = 8, T₃ = 1300 K
η 44.796% ; η_c 0.8 / η_t 0.85 → 27.411% ; regeneration ε = 0.8 → 54.912%
Atkinson: r = 8, q_in = 1800 kJ/kg
η 66.637%
Rankine: 3 MPa / 350 °C → 75 kPa
η 25.80% , w_turbine 686.2 / w_pump 3.03 kJ/kg , quality 0.863 , 20 kg/s → 13.663 MW
R134a: −20 °C / 40 °C
COP 2.58 , COP_hp 3.58 , q_evap 130.15 kJ/kg , throttle quality 0.389 , 3.5 kW load → 1.356 kW
At 15 MPa / 600 °C → 10 kPa, reheat lifts efficiency from 41.59% to 43.47% and exit quality from 0.72 to 0.92 .
What the numbers assume The ideal layer is a cold-air-standard analysis: constant γ, constant cp and cv, reversible processes, so Otto and Brayton efficiency depends only on ratios, not on heat added. The real-fluid layer interpolates built-in saturation tables (water, R134a) and an ideal-gas superheat model, marking the result as fallback data; CoolProp replaces it with Helmholtz free-energy equations of state. Every cycle is checked twice — net work must equal heat in minus heat out, and efficiency must stay under 1 − T_min/T_max.
Limits to keep in mind
Cold-air standard, not a simulation. Constant specific heats and reversible processes mean no combustion chemistry, valve timing or friction; use this layer to compare shapes and check textbook answers, not to predict an engine's fuel consumption.
Fallback properties carry a known error. Without CoolProp, real-fluid states come from built-in tables (water 5–20,000 kPa, R134a −40 to 90 °C): enthalpy and entropy are off by roughly 0.5–1% and efficiency by about half a point. Inputs outside the tables are refused, never extrapolated. What it does not do. No start-up transients, boiler or heat-exchanger sizing, combustion modelling, or refrigerants other than R134a. Convert the pressures and temperatures you type in the pressure converter and temperature converter ; dynamic system simulation lives in the Engineering Lab . The efficient-looking diesel is not the efficient shape The comparison strip at r = 8 and q_in = 1800 kJ/kg reads Atkinson 66.64% , Otto 56.47% , Diesel 40.10% — the diesel cycle comes last, not first. Constant-pressure heat addition makes it the least efficient of the three at identical compression ratio and heat input; the r = 18 preset reaches 63.158% only because of the higher ratio. The other naming trap is r itself: Brayton's r_p = 8 is a pressure ratio (η 44.796% ), not Otto's compression ratio r = 8 (η 56.472% ), and the two are unrelated.
Where it fits Textbook and homework checks Cengel Example 10-1 is the Rankine preset: 3 MPa / 350 °C → 75 kPa reads η 25.80% against the textbook's 26.0% and quality 0.863 against 0.8861. The gap is the declared fallback property model; loading CoolProp tightens it.
Engines, hybrids and heat pumps Otto at r = 8 reads 56.472% , and r = 16 triggers the knock-limit warning; Atkinson's complete expansion reaches 66.637% at the same r, which is why hybrids use it. R134a at −20 / 40 °C gives COP 2.58 for cooling, 3.58 as a heat pump, and a 3.5 kW load draws 1.356 kW .
Privacy Everything except CoolProp runs inside your browser and nothing is uploaded; Load CoolProp and recompute downloads that package from the network, and the calculation still runs locally.
References
Wikipedia, Otto cycle — η = 1 − r^(1−γ). en.wikipedia.org （访问日期：2026-10-01）
Wikipedia, Diesel cycle — the cutoff ratio and the r_c → 1 limit. en.wikipedia.org （访问日期：2026-10-01）
Wikipedia, Brayton cycle — pressure ratio, back work and regeneration. en.wikipedia.org （访问日期：2026-10-01）
Wikipedia, Rankine cycle — reheat and feedwater regeneration. en.wikipedia.org （访问日期：2026-10-01）
Wikipedia, Vapor-compression refrigeration — COP and the expansion valve. en.wikipedia.org （访问日期：2026-10-01）
Bell et al., CoolProp (Ind Eng Chem Res 53:2498–2508, 2014) — the optional Helmholtz-EOS property backend. coolprop.org （访问日期：2026-10-01）
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Updated 2026-10-01