8. Component Matching Flashcards
1
Q
what are the three compressor and turbine matching criteria for a gas generator
A
- same rotational speed: N_C = N_T = N
- same mass flow rate: 𝑚̇_C = 𝑚̇_T = 𝑚̇
- same power: W_dotx,C = -W_dotx,T
2
Q
what is the total-total pressure rise coefficient in an axial compressor, dP_0 / ρU^2
A
- dP_0 / ρU^2 = nΨ = n*dh_0/U^2
- n = efficiency
3
Q
what is the flow coefficient φ for a multistage compressor
A
- φ = 𝑚̇ / ρUA_x
4
Q
what are the two most hazardous conditions to affect a compressor installation
A
- rotating stall
- surge
5
Q
what is rotating stall
A
- a local compressor instability caused by separated flow
6
Q
what is surge
A
- a global system instability caused by flow reversal
- normally preceded by rotating stall
7
Q
what is the non-dimensional time constant parameter in the ODE for surge, B
A
- B = U/2a * sqrt(Vol_p/A_c*L_c)
- Vol_p = plenum volume
- A_c*L_c = inlet duct volume
8
Q
what is the bypass ratio BPR for a geared turbofan
A
- BPR = 𝑚̇_fan / 𝑚̇_core
9
Q
what is the gear ratio G
A
- G = w_fan / w_LPT
10
Q
what does it mean if G = 1
A
- G = 1 means there is no gearbox
11
Q
what is the LPT stage loading coefficient Ψ_LPT in terms of the fan stage loading coefficient Ψ_fan
A
- Ψ_LPT = Ψ_fan * (G*r_fan/r_LPT)^2 * BPR/N_LPT
