ashfordeOU Turbofan Cycle (propulsion/turbofan/turbofan-cycle)
Use when the task is turbofan cycle parameter evaluation: bypass ratio, propulsive efficiency, net thrust, and specific thrust.
Domain quick reference
Units are SI throughout:
- Mass flow m_dot in kg/s.
- Velocities in m/s.
- Thrust in N (newtons).
- Efficiency eta_p dimensionless.
- Bypass ratio B dimensionless.
The four parameters:
- Bypass ratio B = m_dot_fan / m_dot_core, the fan stream mass flow divided by the core stream mass flow.
- Propulsive efficiency eta_p = 2*v0/(v0 + vj), the fraction of jet kinetic energy converted to useful thrust power, from flight velocity v0 and jet velocity vj.
- Net thrust F = m_dot_total*(vj - v0), total mass flow times the jet-to-flight velocity change.
- Specific thrust F/m_dot_total, net thrust per unit total mass flow (m/s).
- Turbofan cycle practice sits in the FAR-33 engine design context.
Workflow
- Collect the fan and core mass flows; compute the bypass_ratio.
- Collect the flight and jet velocities; compute the propulsive_efficiency.
- Collect the total mass flow, jet velocity, and flight velocity; compute the thrust.
- Divide net thrust by total mass flow with the specific_thrust.
- Gate the engine cycle assessment on the four parameters.
Pitfalls
- Unit confusion: mass flow in kg/s, velocities in m/s, thrust in N, efficiency dimensionless.
- Using total thrust instead of net thrust (the vj - v0 term).
- Treating bypass ratio as a mass fraction: B is a ratio of two mass flows, not a fraction of total flow.
Behavior contract (gate 3)
The bypass, efficiency, thrust, and specific-thrust logic is exercised by the gate 3 contract test: scripts/test_turbofan_cycle.py against scripts/turbofan_cycle_logic.py (stdlib unittest, offline). Run: python3 scripts/test_turbofan_cycle.py
Compliance
- Standards referenced, not reproduced: FAR-33 is US government work (public domain); the cycle parameters are common propulsion methodology, summary-only per standards-map.yaml.
- compliance: STANDARDS-REF, gated: false.