def sound_speed_grad(tamb, tamb_d):
"""
Sound speed for ideal gaz
"""
R = earth.gaz_constant()
gam = earth.heat_ratio()
vsnd = numpy.sqrt(gam * R * tamb)
vsnd_d = 0.5 * numpy.sqrt(gam * R / tamb) * tamb_d
return vsnd, vsnd_d
def air_density_grad(pamb, pamb_d, tamb, tamb_d):
"""
Ideal gaz density
"""
R = earth.gaz_constant()
rho0 = earth.sea_level_density()
rho = pamb / (R * tamb)
rho_d = pamb_d / (R * tamb) - tamb_d * pamb / (R * tamb**2)
sig = rho / rho0
sig_d = rho_d / rho0
return rho, rho_d, sig, sig_d
def corrected_air_flow(Ptot, Ttot, Mach):
"""
Computes the corrected air flow per square meter
"""
R = earth.gaz_constant()
gam = earth.heat_ratio()
f_M = Mach * (1. + 0.5 * (gam - 1) * Mach**2)**(-(gam + 1.) / (2. *
(gam - 1.)))
CQoA = (numpy.sqrt(gam / R) * Ptot / numpy.sqrt(Ttot)) * f_M
return CQoA
def pressure_altitude_grad(pamb, pamb_d):
"""
Pressure altitude from ground to 50 km
"""
g = earth.gravity()
R = earth.gaz_constant()
Z = numpy.array([0., 10999., 19999., 31999., 46999., 49999.])
dtodz = numpy.array([-0.0065, 0., 0.0010, 0.0028, 0.])
P = numpy.array([earth.sea_level_pressure(), 0., 0., 0., 0., 0.])
T = numpy.array([earth.sea_level_temperature(), 0., 0., 0., 0., 0.])
j = 0
n = len(P) - 1
P[1] = P[0] * (1 + (dtodz[0] / T[0]) * (Z[1] - Z[0]))**(-g /
(R * dtodz[0]))
T[1] = T[0] + dtodz[0] * (Z[1] - Z[0])
while (j < n and pamb < P[j + 1]):
j = j + 1
T[j + 1] = T[j] + dtodz[j] * (Z[j + 1] - Z[j])
if (0. < numpy.abs(dtodz[j])):
P[j + 1] = P[j] * (1 + (dtodz[j] / T[j]) *
(Z[j + 1] - Z[j]))**(-g / (R * dtodz[j]))
else:
P[j + 1] = P[j] * numpy.exp(-(g / R) * ((Z[j + 1] - Z[j]) / T[j]))
if (pamb < P[n]):
raise Exception("pressure_altitude_grad, altitude cannot exceed 50km")
if (0. < numpy.abs(dtodz[j])):
altp = Z[j] + (
(pamb / P[j])**(-(R * dtodz[j]) / g) - 1) * (T[j] / dtodz[j])
altp_d = (T[j] / dtodz[j]) * (-(R * dtodz[j]) /
(g * P[j])) * pamb_d * (pamb / P[j])**(
-(R * dtodz[j]) / g - 1)
else:
altp = Z[j] - (T[j] / (g / R)) * numpy.log(pamb / P[j])
altp_d = -((T[j] * R) / g) * (pamb_d / pamb)
return altp, altp_d
def atmosphere_grad(altp, altp_d, disa, disa_d):
"""
Pressure from pressure altitude from ground to 50 km
"""
g = earth.gravity()
R = earth.gaz_constant()
Z = numpy.array([0., 10999., 19999., 31999., 46999., 49999.])
Z_d = numpy.array([0., 0., 0., 0., 0., 0.])
dtodz = numpy.array([-0.0065, 0., 0.0010, 0.0028, 0.])
dtodz_d = numpy.array([0., 0., 0., 0., 0.])
P = numpy.array([earth.sea_level_pressure(), 0., 0., 0., 0., 0.])
P_d = numpy.array([0., 0., 0., 0., 0., 0.])
T = numpy.array([earth.sea_level_temperature(), 0., 0., 0., 0., 0.])
T_d = numpy.array([0., 0., 0., 0., 0., 0.])
if (Z[-1] < altp):
raise Exception("atmosphere_grad, altitude cannot exceed 50km")
j = 0
while (Z[1 + j] <= altp):
T[j + 1] = T[j] + dtodz[j] * (Z[j + 1] - Z[j])
T_d[j + 1] = T_d[j] + dtodz_d[j] * (Z[j + 1] - Z[j]) + dtodz[j] * (
Z_d[j + 1] - Z_d[j])
if (0. < numpy.abs(dtodz[j])):
B1 = 1 + (dtodz[j] * (Z[1 + j] - Z[j])) / (T[j] + disa)
B1_dz = (dtodz[j] * (Z_d[1 + j] - Z_d[j])) / (T[j] + disa)
B1_dt = (dtodz_d[j] * (Z[1 + j] - Z[j])) / (T[j] + disa) - (
dtodz[j] * (Z[1 + j] - Z[j]) * disa_d) / (T[j] + disa)**2
B2 = -g / (R * dtodz[j])
B2_dt = (g * dtodz_d[j]) / (R * dtodz[j]**2)
P[1 + j] = P[j] * B1**B2
P_d[1 + j] = P[j] * (
B2 * B1_dz * B1**(B2 - 1) + (B1**B2) *
(B2_dt * numpy.log(B1) + B2 * B1_dt / B1)) + P_d[j] * B1**B2
else:
B3 = -(g / R) * ((Z[1 + j] - Z[j]) / (T[j] + disa))
B3_d = -(g / R) * ((Z_d[1 + j] - Z_d[j]) /
(T[j] + disa)) + (g / R) * ((Z[1 + j] - Z[j]) *
(T_d[j] + disa_d) /
(T[j] + disa)**2)
P[j + 1] = P[j] * numpy.exp(B3)
P_d[j + 1] = P_d[j] * numpy.exp(B3) + P[j] * B3_d * numpy.exp(B3)
j = j + 1
if (0. < numpy.abs(dtodz[j])):
B1 = 1 + (dtodz[j] * (altp - Z[j])) / (T[j] + disa)
B1_dz = (dtodz[j] * (altp_d - Z_d[j])) / (T[j] + disa)
B1_dt = (dtodz_d[j] *
(altp - Z[j])) / (T[j] + disa) - (dtodz[j] * (altp - Z[j]) *
disa_d) / (T[j] + disa)**2
B2 = -g / (R * dtodz[j])
B2_dt = (g * dtodz_d[j]) / (R * dtodz[j]**2)
pamb = P[j] * B1**B2
pamb_d = P[j] * (
B2 * B1_dz * B1**(B2 - 1) + (B1**B2) *
(B2_dt * numpy.log(B1) + B2 * B1_dt / B1)) + P_d[j] * B1**B2
else:
B3 = -(g / R) * ((altp - Z[j]) / (T[j] + disa))
B3_d = -(g / R) * ((altp_d - Z_d[j]) /
(T[j] + disa)) + (g / R) * ((altp - Z[j]) *
(T_d[j] + disa_d) /
(T[j] + disa)**2)
pamb = P[j] * numpy.exp(B3)
pamb_d = P_d[j] * numpy.exp(B3) + P[j] * B3_d * numpy.exp(B3)
tamb = T[j] + dtodz[j] * (altp - Z[j]) + disa
tamb_d = T_d[j] + dtodz_d[j] * (altp - Z[j]) + dtodz[j] * (altp_d -
Z_d[j]) + disa_d
return pamb, pamb_d, tamb, tamb_d, dtodz[j]
def eval_bli_nacelle_design(this_nacelle,Pamb,Tamb,Mach,shaft_power,hub_width,body_length,body_width):
"""
BLI nacelle design
"""
gam = earth.heat_ratio()
r = earth.gaz_constant()
Cp = earth.heat_constant(gam,r)
(rho,sig) = earth.air_density(Pamb,Tamb)
Vsnd = earth.sound_speed(Tamb)
Re = earth.reynolds_number(Pamb,Tamb,Mach)
Vair = Vsnd*Mach
# Precalculation of the relation between d0 and d1
#-----------------------------------------------------------------------------------------------------------
body_bnd_layer = resize_boundary_layer(body_width,hub_width)
# Electrical nacelle geometry : e-nacelle diameter is size by cruise conditions
#-----------------------------------------------------------------------------------------------------------
r0 = 0.5*body_width # Radius of the fuselage, supposed constant
d0 = jet.boundary_layer(Re,body_length) # theoritical thickness of the boundary layer without taking account of fuselage tapering
r1 = 0.5*hub_width # Radius of the hub of the efan nacelle
d1 = lin_interp_1d(d0,body_bnd_layer[:,0],body_bnd_layer[:,1]) # Thickness of the BL around the hub
deltaV = 2.*Vair*(this_nacelle.efficiency_fan/this_nacelle.efficiency_prop - 1.) # speed variation produced by the fan
PwInput = this_nacelle.efficiency_fan*shaft_power # kinetic energy produced by the fan
#===========================================================================================================
def fct_power_1(y,PwInput,deltaV,rho,Vair,r1,d1):
(q0,q1,q2,v1,dVbli) = jet.air_flows(rho,Vair,r1,d1,y)
Vinlet = Vair - dVbli
Vjet = Vinlet + deltaV
Pw = 0.5*q1*(Vjet**2 - Vinlet**2)
y = PwInput - Pw
return y
#-----------------------------------------------------------------------------------------------------------
fct_arg = (PwInput,deltaV,rho,Vair,r1,d1)
# Computation of y1 : thickness of the vein swallowed by the inlet
output_dict = fsolve(fct_power_1, x0=d1, args=fct_arg, full_output=True)
y1 = output_dict[0][0]
(q0,q1,q2,v1,dVbli) = jet.air_flows(rho,Vair,r1,d1,y1)
MachInlet = v1/Vsnd # Mean Mach number at inlet position
Ptot = earth.total_pressure(Pamb,MachInlet) # Stagnation pressure at inlet position
Ttot = earth.total_temperature(Tamb,MachInlet) # Stagnation temperature at inlet position
MachFan = 0.5 # required Mach number at fan position
CQoA1 = jet.corrected_air_flow(Ptot,Ttot,MachFan) # Corrected air flow per area at fan position
eFanArea = q1/CQoA1 # Fan area around the hub
fan_width = numpy.sqrt(hub_width**2 + 4*eFanArea/numpy.pi) # Fan diameter
Vjet = v1 + deltaV # Jet velocity
TtotJet = Ttot + shaft_power/(q1*Cp) # Stagnation pressure increases due to introduced work
Tstat = TtotJet - 0.5*Vjet**2/Cp # static temperature
VsndJet = numpy.sqrt(gam*r*Tstat) # Sound velocity at nozzle exhaust
MachJet = Vjet/VsndJet # Mach number at nozzle output
PtotJet = earth.total_pressure(Pamb,MachJet) # total pressure at nozzle exhaust (P = Pamb)
CQoA2 = jet.corrected_air_flow(PtotJet,TtotJet,MachJet) # Corrected air flow per area at nozzle output
nozzle_area = q1/CQoA2 # Fan area around the hub
nozzle_width = numpy.sqrt(4*nozzle_area/numpy.pi) # Nozzle diameter
this_nacelle.hub_width = hub_width
this_nacelle.fan_width = fan_width
this_nacelle.nozzle_width = nozzle_width
this_nacelle.nozzle_area = nozzle_area
this_nacelle.width = 1.20*fan_width # Surrounding structure
this_nacelle.length = 1.50*this_nacelle.width
this_nacelle.net_wetted_area = numpy.pi*this_nacelle.width*this_nacelle.length # Nacelle wetted area
this_nacelle.bnd_layer = body_bnd_layer
this_nacelle.body_length = body_length
return
def fan_thrust(nacelle, Pamb, Tamb, Mach, PwShaft):
"""
Compute the thrust of a fan of given geometry swallowing free air stream
"""
gam = earth.heat_ratio()
r = earth.gaz_constant()
Cp = earth.heat_constant(gam, r)
#===========================================================================================================
def fct_power(q, PwShaft, Pamb, Ttot, Vair, NozzleArea):
Vinlet = Vair
PwInput = nacelle.efficiency_fan * PwShaft
Vjet = numpy.sqrt(2. * PwInput / q +
Vinlet**2) # Supposing isentropic compression
TtotJet = Ttot + PwShaft / (
q * Cp) # Stagnation temperature increases due to introduced work
TstatJet = TtotJet - 0.5 * Vjet**2 / Cp # Static temperature
VsndJet = earth.sound_speed(TstatJet) # Sound speed at nozzle exhaust
MachJet = Vjet / VsndJet # Mach number at nozzle output
PtotJet = earth.total_pressure(
Pamb, MachJet) # total pressure at nozzle exhaust (P = Pamb)
CQoA1 = corrected_air_flow(
PtotJet, TtotJet,
MachJet) # Corrected air flow per area at fan position
q0 = CQoA1 * NozzleArea
y = q0 - q
return y
#-----------------------------------------------------------------------------------------------------------
NozzleArea = nacelle.nozzle_area
FanWidth = nacelle.fan_width
Ptot = earth.total_pressure(Pamb, Mach) # Total pressure at inlet position
Ttot = earth.total_temperature(Tamb,
Mach) # Total temperature at inlet position
Vsnd = earth.sound_speed(Tamb)
Vair = Vsnd * Mach
fct_arg = (PwShaft, Pamb, Ttot, Vair, NozzleArea)
CQoA0 = corrected_air_flow(
Ptot, Ttot, Mach) # Corrected air flow per area at fan position
q0init = CQoA0 * (0.25 * numpy.pi * FanWidth**2)
# Computation of the air flow swallowed by the inlet
output_dict = fsolve(fct_power, x0=q0init, args=fct_arg, full_output=True)
q0 = output_dict[0][0]
if (output_dict[2] != 1):
raise Exception("Convergence problem")
Vinlet = Vair
PwInput = nacelle.efficiency_fan * PwShaft
Vjet = numpy.sqrt(2. * PwInput / q0 + Vinlet**2)
eFn = q0 * (Vjet - Vinlet)
return (eFn, q0)
def fan_thrust_with_bli(nacelle, Pamb, Tamb, Mach, PwShaft):
"""
Compute the thrust of a fan of a given geometry swallowing
the boundary layer (BL) of a body of a given geometry
The amount of swallowed BL depends on the given shaft power and flying
conditions.
"""
gam = earth.heat_ratio()
r = earth.gaz_constant()
Cp = earth.heat_constant(gam, r)
#===========================================================================================================
def fct_power_bli(y, PwShaft, Pamb, rho, Ttot, Vair, r1, d1, nozzle_area):
(q0, q1, q2, Vinlet, dVbli) = air_flows(rho, Vair, r1, d1, y)
PwInput = nacelle.efficiency_fan * PwShaft
Vjet = numpy.sqrt(2. * PwInput / q1 + Vinlet**2)
TtotJet = Ttot + PwShaft / (
q1 * Cp) # Stagnation temperature increases due to introduced work
Tstat = TtotJet - 0.5 * Vjet**2 / Cp # Static temperature
VsndJet = earth.sound_speed(Tstat) # Sound speed at nozzle exhaust
MachJet = Vjet / VsndJet # Mach number at nozzle output
PtotJet = earth.total_pressure(
Pamb, MachJet
) # total pressure at nozzle exhaust (P = Pamb) supposing adapted nozzle
CQoA1 = corrected_air_flow(
PtotJet, TtotJet,
MachJet) # Corrected air flow per area at nozzle position
q = CQoA1 * nozzle_area
y = q1 - q
return y
#-----------------------------------------------------------------------------------------------------------
nozzle_area = nacelle.nozzle_area
bnd_layer = nacelle.bnd_layer
Re = earth.reynolds_number(Pamb, Tamb, Mach)
d0 = boundary_layer(
Re, nacelle.body_length
) # theorical thickness of the boundary layer without taking account of fuselage tapering
r1 = 0.5 * nacelle.hub_width # Radius of the hub of the eFan nacelle
d1 = lin_interp_1d(d0, bnd_layer[:, 0],
bnd_layer[:, 1]) # Using the precomputed relation
Ttot = earth.total_temperature(
Tamb, Mach) # Stagnation temperature at inlet position
rho, sig = earth.air_density(Pamb, Tamb)
Vsnd = earth.sound_speed(Tamb)
Vair = Vsnd * Mach
fct_arg = (PwShaft, Pamb, rho, Ttot, Vair, r1, d1, nozzle_area)
# Computation of y1 : thikness of the vein swallowed by the inlet
output_dict = fsolve(fct_power_bli,
x0=0.50,
args=fct_arg,
full_output=True)
y = output_dict[0][0]
if (output_dict[2] != 1):
raise Exception("Convergence problem")
(q0, q1, q2, Vinlet, dVbli) = air_flows(rho, Vair, r1, d1, y)
PwInput = nacelle.efficiency_fan * PwShaft
Vjet = numpy.sqrt(2. * PwInput / q1 + Vinlet**2)
eFn = q1 * (Vjet - Vinlet)
return (eFn, q1, dVbli)
