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[samples] Fix heat release in ic_engine.py #820

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Mar 23, 2020
Merged

[samples] Fix heat release in ic_engine.py #820

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e8c1bf2
[samples] Fix heat release in ic_engine.py
ischoegl Mar 11, 2020
1113ebb
[thermo] Prevent creation of pre-existing extra SolutionArray columns
ischoegl Mar 20, 2020
871617e
[thermo] Add unit test for invalid extra SolutionArray column names
ischoegl Mar 20, 2020
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10 changes: 10 additions & 0 deletions interfaces/cython/cantera/composite.py
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Original file line number Diff line number Diff line change
Expand Up @@ -513,9 +513,15 @@ def __init__(self, phase, shape=(0,), states=None, extra=None):
self._indices = list(np.ndindex(self._shape))
self._output_dummy = self._states[..., 0]

reserved = self.__dir__()

self._extra = {}
if isinstance(extra, dict):
for name, v in extra.items():
if name in reserved:
raise ValueError(
"Unable to create extra column '{}': name is already "
"used by SolutionArray objects.".format(name))
if not np.shape(v):
self._extra[name] = [v]*self._shape[0]
elif len(v) == self._shape[0]:
Expand All @@ -526,6 +532,10 @@ def __init__(self, phase, shape=(0,), states=None, extra=None):

elif extra and self._shape == (0,):
for name in extra:
if name in reserved:
raise ValueError(
"Unable to create extra column '{}': name is already "
"used by SolutionArray objects.".format(name))
self._extra[name] = []

elif extra:
Expand Down
11 changes: 4 additions & 7 deletions interfaces/cython/cantera/examples/reactors/ic_engine.py
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Original file line number Diff line number Diff line change
Expand Up @@ -155,7 +155,7 @@ def piston_speed(t):
# set up output data arrays
states = ct.SolutionArray(
cyl.thermo,
extra=('t', 'ca', 'V', 'm', 'mdot_in', 'mdot_out', 'dWv_dt', 'heat_release_rate'),
extra=('t', 'ca', 'V', 'm', 'mdot_in', 'mdot_out', 'dWv_dt'),
)

# simulate with a maximum resolution of 1 deg crank angle
Expand All @@ -169,17 +169,14 @@ def piston_speed(t):
# calculate results to be stored
dWv_dt = - (cyl.thermo.P - ambient_air.thermo.P) * A_piston * \
piston_speed(sim.time)
heat_release_rate = - cyl.volume * ct.gas_constant * cyl.T * \
np.sum(gas.standard_enthalpies_RT * cyl.thermo.net_production_rates, 0)

# append output data
states.append(cyl.thermo.state,
t=sim.time, ca=crank_angle(sim.time),
V=cyl.volume, m=cyl.mass,
mdot_in=inlet_valve.mdot(sim.time),
mdot_out=outlet_valve.mdot(sim.time),
dWv_dt=dWv_dt,
heat_release_rate=heat_release_rate)
dWv_dt=dWv_dt)


#######################################################################
Expand Down Expand Up @@ -221,7 +218,7 @@ def ca_ticks(t):

# heat of reaction and expansion work
fig, ax = plt.subplots()
ax.plot(t, 1.e-3 * states.heat_release_rate, label=r'$\dot{Q}$')
ax.plot(t, 1.e-3 * states.heat_release_rate * states.V, label=r'$\dot{Q}$')
ax.plot(t, 1.e-3 * states.dWv_dt, label=r'$\dot{W}_v$')
ax.set_ylim(-1e2, 1e3)
ax.legend(loc=0)
Expand All @@ -247,7 +244,7 @@ def ca_ticks(t):
######################################################################

# heat release
Q = trapz(states.heat_release_rate, t)
Q = trapz(states.heat_release_rate * states.V, t)
print('{:45s}{:>4.1f} kW'.format('Heat release rate per cylinder (estimate):',
Q / t[-1] / 1000.))

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4 changes: 4 additions & 0 deletions interfaces/cython/cantera/test/test_thermo.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1641,6 +1641,10 @@ def test_slicing_ndim(self):
self.assertArrayNear(col3.T, 900*np.ones(2))
self.assertArrayNear(row2.T, 900*np.ones(5))

def test_extra(self):
with self.assertRaises(ValueError):
states = ct.SolutionArray(self.gas, extra=['creation_rates'])

def test_append(self):
states = ct.SolutionArray(self.gas, 5)
states.TPX = np.linspace(500, 1000, 5), 2e5, 'H2:0.5, O2:0.4'
Expand Down