def __init__(self,
engine_type='ATJ',
max_thrust=None,
max_mach=None,
afterburner=False,
k_sfc=1.0,
k_w=1.0,
k_size=1.0,
turbine_inlet_temp=2000,
atmosphere=None, *args, **kwargs):
self.engine_type = engine_type
self.afterburner = afterburner
self.k_sfc = k_sfc
self.k_w = k_w
self.k_size = k_size
self.atmosphere = Atmosphere() if atmosphere is None else atmosphere
self.turbine_inlet_temp = turbine_inlet_temp
if 'bpr' in kwargs:
self.bpr = kwargs.pop('bpr')
if self.bpr < 2.0 and engine_type == 'HBTF':
raise ValueError(
"High By-Pass Turbo-Fans must have by-pass ratios greater than 2.0, not {}".format(
self.bpr))
elif self.bpr > 2.0 and engine_type == 'LBTF':
raise ValueError(
"Low By-Pass Turbo-Fans must have by-pass ratios less than 2.0, not {}".format(
self.bpr))
else:
self.bpr = self._TYPES[engine_type]['bpr']
self.max_mach = max_mach
self.max_thrust = max_thrust
if engine_type not in self._TYPES:
raise ValueError(
"Engine type must be one of these {}, not {}".format(
self._TYPES.keys(), configuration))
self.alphas = self._TYPES[engine_type]['alpha']
self.name = self._TYPES[engine_type]['name']
self._tfsc_coefficients = self._TYPES[engine_type]['tsfc_coefficients']
class Engine(object):
_TYPES = dict(ATJ={
'name': 'Advanced Turbo-Jet (with afterburner)',
'alpha': [1, 1.00, 0.952, 0.30, 0.40, 2.0, 0.7],
'tsfc_coefficients': {'normal': [1.1, 0.30],
'afterburner': [1.5, 0.23]},
'bpr': 0,
},
ATP={
'name': 'Advanced Turbo-Prop',
'alpha': [1, 0.12, 0.000, 1.00, -0.02, -1.0, 0.5],
'tsfc_coefficients': {'normal': [0.18, 0.80]},
'bpr': None,
},
HBTF={
'name': 'High By-Pass Turbo-Fan',
'alpha': [-1, 1.00, 0.568, 0.25, -1.20, 3.0, 0.6],
'tsfc_coefficients': {'normal': [0.45, 0.54]},
'bpr': 6,
},
LBTF={
'name': 'Low By-Pass Turbo-Fan (with afterburner)',
'alpha': [1, 1.00, 0.940, 0.38, 0.40, 2.0, 0.7],
'tsfc_coefficients': {'normal': [0.9, 0.30],
'afterburner': [1.6, 0.27]},
'bpr': 1.5,
})
def __init__(self,
engine_type='ATJ',
max_thrust=None,
max_mach=None,
afterburner=False,
k_sfc=1.0,
k_w=1.0,
k_size=1.0,
turbine_inlet_temp=2000,
atmosphere=None, *args, **kwargs):
self.engine_type = engine_type
self.afterburner = afterburner
self.k_sfc = k_sfc
self.k_w = k_w
self.k_size = k_size
self.atmosphere = Atmosphere() if atmosphere is None else atmosphere
self.turbine_inlet_temp = turbine_inlet_temp
if 'bpr' in kwargs:
self.bpr = kwargs.pop('bpr')
if self.bpr < 2.0 and engine_type == 'HBTF':
raise ValueError(
"High By-Pass Turbo-Fans must have by-pass ratios greater than 2.0, not {}".format(
self.bpr))
elif self.bpr > 2.0 and engine_type == 'LBTF':
raise ValueError(
"Low By-Pass Turbo-Fans must have by-pass ratios less than 2.0, not {}".format(
self.bpr))
else:
self.bpr = self._TYPES[engine_type]['bpr']
self.max_mach = max_mach
self.max_thrust = max_thrust
if engine_type not in self._TYPES:
raise ValueError(
"Engine type must be one of these {}, not {}".format(
self._TYPES.keys(), configuration))
self.alphas = self._TYPES[engine_type]['alpha']
self.name = self._TYPES[engine_type]['name']
self._tfsc_coefficients = self._TYPES[engine_type]['tsfc_coefficients']
def __repr__(self):
return "<Engine {}>".format(self.name)
def tsfc(self, mach, altitude, afterburner=False):
"""
Estimates TSFC as a function of Mach number and altitude.
.. note::
based on Mattingly, 2002 (pp. 71)
:param mach: Mach number at which engine is flying
:param altitude: altitude at which engine is flying
:param afterburner: whether or not afterburners are engaged
:type mach: float
:type altitude: float
:type afterburner: bool
:rtype: float
"""
a, b = self._tfsc_coefficients[
'afterburner'
] if afterburner else self._tfsc_coefficients['normal']
theta = self.atmosphere.temperature(
altitude=altitude) / self.atmosphere.temperature_sl_rankine
return (a + b * mach) * sqrt(theta)
def size(self):
"""
Determines a jet engine's parameters based on Raymer's rules as defined in:
Raymer, D. P., "Aircraft design: a conceptual approach", 3rd Ed., pp. 235
.. note::
Cruise is assumed to be at approximately 36,000 ft (11,000 m) and 0.9 Mach
"""
if self.afterburner:
if self.bpr > 1.0:
raise (NotImplementedError(
"BPR must be less than 1.0 for afterburning engines, bpr = {}".format(
self.bpr)))
self.w = 0.063 * (self.max_thrust ** 1.1) * \
(self.max_mach ** 0.25) * exp(-0.81 * self.bpr)
self.l = 0.255 * (self.max_thrust ** 0.4) * (self.max_mach ** 0.2)
self.d = 0.024 * (self.max_thrust ** 0.5) * exp(0.04 * self.bpr)
self.sfc_max = 2.1 * exp(-0.12 * self.bpr)
self.t_cruise = 2.4 * (self.max_thrust ** 0.74
) * exp(0.023 * self.bpr)
self.sfc_cruise = 1.04 * exp(-0.186 * self.bpr)
else:
self.w = 0.084 * (self.max_thrust ** 1.1) * exp(-0.045 * self.bpr)
self.l = 0.185 * (self.max_thrust ** 0.4) * (self.max_mach ** 0.2)
self.d = 0.033 * (self.max_thrust ** 0.5) * exp(0.04 * self.bpr)
self.sfc_max = 0.67 * exp(-0.12 * self.bpr)
self.t_cruise = 0.60 * \
(self.max_thrust ** 0.9) * exp(0.02 * self.bpr)
self.sfc_cruise = 0.88 * exp(-0.05 * self.bpr)
def thrust_lapse(self, altitude, mach=None, speed=None):
"""
Calculates the reduction in thrust for the engine as a function of altitude and speed.
:param altitude: altitude at which the engine is flying
:param mach: Mach number (optional)
:param speed: speed at which the aircraft is flying (must be specified if mach is None)
:type altitude: float
:type mach: float
:type speed: float
:rtype: float
"""
sign, a1, a2, a3, a4, a5, a6 = self.alphas
if mach is None:
if speed is None:
raise ValueError(
"Must specify Mach number or speed (in ft/sec)")
mach = speed / self.atmosphere.speed_of_sound(altitude)
density_ratio = self.atmosphere.density(
altitude) / self.atmosphere.density_sl
return a1 * (a2 + a3 * (sign * mach - a4) ** a5) * density_ratio ** a6
