There are three equations for gas path dynamics. They are mass conservation[^1]
$$\frac{d\rho_i}{dt}=\frac{\sum W}{V_i}$$
Momentum Conservation:[^1]
$$\frac{dW_i}{dt}=\frac{\text{force}+\sum PA}{Le_i}$$
Energy Conservation:[^1]
$$\frac{dP_i}{dt}=\frac{\text{power}+\sum W}{V_i}$$
The gas path dynamics can be lumped into a 1-dimensional control volume for each component of the fan, burner, and compressors.[^1] In each control volume, the pressure change, heat transfer, and energy change is input as force or power in the control volume. [^1]
When evaluating the air mass flow, you need a model for air mass flow demand, inlet critical total pressure recovery throughout the operating envelope, a model for inlet critical stream tube area in the entire operating envelope, and a model of inlet spillage drag.[^2]
[[Engine Airflow Model]]
- MultivariablePIControl[^1]
- johnsonExRocketMan2020b[^2]
Backlinks:
[[Compressor Model]]
[[Inlets]]
[[Jet Engine Combustion Chamber Model]]
[[Jet Engine Construction]]
Lumped Parameter Model
Reduced Order Models
[[Spillage Drag]]
[[Tip Jet Dynamics]]
[[Turbojet Engine Inlets]]