oemof · fwitte · Jun 10, 2025 · Jun 5, 2025 · Jun 5, 2025 · Jun 5, 2025
diff --git a/docs/whats_new/v0-8-2.rst b/docs/whats_new/v0-8-2.rst
@@ -12,6 +12,22 @@ API changes
   :ref:`in the docs <tespy_subsystems_label>`
   (`PR #652 <https://github.com/oemof/tespy/pull/652>`__).
 
+New Features
+############
+- The combustion based component classes :code:`CombustionChamber`,
+  :code:`DiabaticCombustionChamber` and :code:`CombustionEngine` can now handle
+  carbonmonoxide as fuel
+  (`PR #674 <https://github.com/oemof/tespy/pull/674>`__).
+
+Other Changes
+#############
+- The partial derivatives for specified temperature are only calculated towards
+  enthalpy and pressure, not towards the fluid compostion. The reason for this
+  is, that it is not intended, that the composition of a fluid can be
+  determined by specifying temperature. Removing this saves a lot of
+  computational overhead for mixtures
+  (`PR #674 <https://github.com/oemof/tespy/pull/674>`__).
+
 Contributors
 ############
 - Francesco Witte (`@fwitte <https://github.com/fwitte>`__)
diff --git a/src/tespy/components/combustion/base.py b/src/tespy/components/combustion/base.py
@@ -47,7 +47,7 @@ class CombustionChamber(Component):
 
     Available fuels
 
-    - methane, ethane, propane, butane, hydrogen
+    - methane, ethane, propane, butane, hydrogen, carbon monoxide, nDodecane
 
     Inlets/Outlets
 
@@ -334,21 +334,22 @@ def calc_lhv(self, f):
         hf['propane'] = -103.8
         hf['butane'] = -125.7
         hf['nDodecane'] = -289.4
+        hf['CO'] = -110.5
         hf[self.o2] = 0
         hf[self.co2] = -393.51
         # water (gaseous)
         hf[self.h2o] = -241.826
 
         key = set(list(hf.keys())).intersection(
-                set([a.replace(' ', '')
-                     for a in CP.get_aliases(f)]))
+            set([a.replace(' ', '') for a in CP.get_aliases(f)])
+        )
 
         val = (
             -(
                 self.fuels[f]['H'] / 2 * hf[self.h2o]
                 + self.fuels[f]['C'] * hf[self.co2]
                 - (
-                    (self.fuels[f]['C'] + self.fuels[f]['H'] / 4) * hf[self.o2]
+                    (self.fuels[f]['C'] + self.fuels[f]['H'] / 4 - self.fuels[f]['O'] / 2) * hf[self.o2]
                     + hf[list(key)[0]]
                 )
             ) / inl[0].fluid.wrapper[f]._molar_mass * 1000
@@ -601,17 +602,20 @@ def stoichiometry(self, fluid):
         n_oxy_stoich = {}
         n_h = 0
         n_c = 0
+        n_o = 0
         for f in self.fuel_list:
             n_fuel[f] = 0
             for i in inl:
                 n = i.m.val_SI * i.fluid.val[f] / inl[0].fluid.wrapper[f]._molar_mass
                 n_fuel[f] += n
                 n_h += n * self.fuels[f]['H']
                 n_c += n * self.fuels[f]['C']
+                n_o += n * self.fuels[f]['O']
 
             # stoichiometric oxygen requirement for each fuel
             n_oxy_stoich[f] = n_fuel[f] * (
                 self.fuels[f]['H'] / 4 + self.fuels[f]['C']
+                - self.fuels[f]['O'] / 2
             )
 
         n_oxygen = 0
@@ -622,7 +626,7 @@ def stoichiometry(self, fluid):
 
         ###################################################################
         # calculate stoichiometric oxygen
-        n_oxygen_stoich = n_h / 4 + n_c
+        n_oxygen_stoich = n_h / 4 + n_c - n_o / 2
 
         ###################################################################
         # calculate lambda if not set
@@ -662,7 +666,7 @@ def stoichiometry(self, fluid):
             if self.lamb.val < 1:
                 n_fuel_exc = (
                     -(n_oxygen / n_oxygen_stoich - 1) * n_oxy_stoich[fluid]
-                    / (self.fuels[fluid]['H'] / 4 + self.fuels[fluid]['C'])
+                    / (self.fuels[fluid]['H'] / 4 + self.fuels[fluid]['C'] - self.fuels[fluid]['O'] / 2)
                 )
             else:
                 n_fuel_exc = 0
@@ -994,6 +998,7 @@ def calc_lambda(self):
 
         n_h = 0
         n_c = 0
+        n_o = 0
         for f in self.fuel_list:
             for i in inl:
                 n_fuel = (
@@ -1002,14 +1007,15 @@ def calc_lambda(self):
                 )
                 n_h += n_fuel * self.fuels[f]['H']
                 n_c += n_fuel * self.fuels[f]['C']
+                n_o += n_fuel * self.fuels[f]['O']
 
         n_oxygen = 0
         for i in inl:
             n_oxygen += (
                 i.m.val_SI * i.fluid.val[self.o2]
                 / inl[0].fluid.wrapper[self.o2]._molar_mass
             )
-        n_oxygen_stoich = n_h / 4 + n_c
+        n_oxygen_stoich = n_h / 4 + n_c - n_o / 2
         return n_oxygen / n_oxygen_stoich
 
 
@@ -1218,16 +1224,12 @@ def convergence_check(self):
                     outl.fluid.val[f] = 0.05
 
             elif f == self.co2:
-                if outl.fluid.val[f] > 0.1:
-                    outl.fluid.val[f] = 0.075
-                if outl.fluid.val[f] < 0.001:
-                    outl.fluid.val[f] = 0.02
+                if outl.fluid.val[f] > 0.15:
+                    outl.fluid.val[f] = 0.1
 
             elif f == self.h2o:
-                if outl.fluid.val[f] > 0.1:
-                    outl.fluid.val[f] = 0.075
-                if outl.fluid.val[f] < 0.001:
-                    outl.fluid.val[f] = 0.02
+                if outl.fluid.val[f] > 0.15:
+                    outl.fluid.val[f] = 0.1
 
             elif f in self.fuel_list:
                 if outl.fluid.val[f] > 0:

diff --git a/src/tespy/components/combustion/diabatic.py b/src/tespy/components/combustion/diabatic.py
@@ -42,7 +42,7 @@ class DiabaticCombustionChamber(CombustionChamber):
 
     Available fuels
 
-    - methane, ethane, propane, butane, hydrogen
+    - methane, ethane, propane, butane, hydrogen, carbon monoxide, nDodecane
 
     Inlets/Outlets
 

diff --git a/src/tespy/components/combustion/engine.py b/src/tespy/components/combustion/engine.py
@@ -63,7 +63,7 @@ class CombustionEngine(CombustionChamber):
 
     Available fuels
 
-    - methane, ethane, propane, butane, hydrogen
+    - methane, ethane, propane, butane, hydrogen, carbon monoxide, nDodecane
 
     Inlets/Outlets
 

diff --git a/src/tespy/connections/bus.py b/src/tespy/connections/bus.py
@@ -158,10 +158,14 @@ class Bus:
     25819387.0
     >>> round(chp.Q1.val + chp.Q2.val, 0)
     -8899014.0
+    >>> round(comb_fgc.T.val, 5)
+    443.33078
+    >>> round(fgc_fg.T.val, 5)
+    120.0
     >>> round(fgc_cw.m.val_SI * (fgc_cw.h.val_SI - pu_sp.h.val_SI), 0)
-    12477091.0
+    12477089.0
     >>> round(heat_bus.P.val, 0)
-    12477091.0
+    12477089.0
     >>> round(pu.calc_bus_efficiency(power_bus), 2)
     0.98
     >>> power_bus.set_attr(P=-7.5e6)

diff --git a/src/tespy/connections/connection.py b/src/tespy/connections/connection.py
@@ -11,11 +11,10 @@
 
 import numpy as np
 
-from tespy.components.component import Component
 from tespy.components import Subsystem
+from tespy.components.component import Component
 from tespy.tools import fluid_properties as fp
 from tespy.tools import logger
-from tespy.tools.data_containers import DataContainer as dc
 from tespy.tools.data_containers import FluidComposition as dc_flu
 from tespy.tools.data_containers import FluidProperties as dc_prop
 from tespy.tools.data_containers import ReferencedFluidProperties as dc_ref
@@ -36,7 +35,6 @@
 from tespy.tools.fluid_properties import s_mix_ph
 from tespy.tools.fluid_properties import v_mix_ph
 from tespy.tools.fluid_properties import viscosity_mix_ph
-from tespy.tools.fluid_properties.functions import dT_mix_ph_dfluid
 from tespy.tools.fluid_properties.functions import p_sat_T
 from tespy.tools.fluid_properties.helpers import get_mixture_temperature_range
 from tespy.tools.fluid_properties.helpers import get_number_of_fluids
@@ -765,10 +763,6 @@ def T_deriv(self, k, **kwargs):
             self.jacobian[k, self.h.J_col] = (
                 dT_mix_pdh(self.p.val_SI, self.h.val_SI, self.fluid_data, self.mixing_rule, self.T.val_SI)
             )
-        for fluid in self.fluid.is_var:
-            self.jacobian[k, self.fluid.J_col[fluid]] = dT_mix_ph_dfluid(
-                self.p.val_SI, self.h.val_SI, fluid, self.fluid_data, self.mixing_rule
-            )
 
     def T_ref_func(self, k, **kwargs):
         ref = self.T_ref.ref
@@ -788,11 +782,6 @@ def T_ref_deriv(self, k, **kwargs):
             self.jacobian[k, ref.obj.h.J_col] = -(
                 dT_mix_pdh(ref.obj.p.val_SI, ref.obj.h.val_SI, ref.obj.fluid_data, ref.obj.mixing_rule)
             ) * ref.factor
-        for fluid in ref.obj.fluid.is_var:
-            if not self._increment_filter[ref.obj.fluid.J_col[fluid]]:
-                self.jacobian[k, ref.obj.fluid.J_col[fluid]] = -dT_mix_ph_dfluid(
-                    ref.obj.p.val_SI, ref.obj.h.val_SI, fluid, ref.obj.fluid_data, ref.obj.mixing_rule
-                )
 
     def calc_viscosity(self, T0=None):
         try:

diff --git a/src/tespy/tools/global_vars.py b/src/tespy/tools/global_vars.py
@@ -101,4 +101,7 @@
 
 }
 
-combustion_gases = ['methane', 'ethane', 'propane', 'butane', 'hydrogen', 'nDodecane']
+combustion_gases = [
+    'methane', 'ethane', 'propane', 'butane', 'hydrogen', 'nDodecane',
+    'CO'
+]
diff --git a/tests/test_components/test_combustion.py b/tests/test_components/test_combustion.py
@@ -33,9 +33,9 @@ def setup_method(self):
 
     def setup_CombustionChamber_network(self, instance):
 
-        self.c1 = Connection(self.air, 'out1', instance, 'in1')
-        self.c2 = Connection(self.fuel, 'out1', instance, 'in2')
-        self.c3 = Connection(instance, 'out1', self.fg, 'in1')
+        self.c1 = Connection(self.air, 'out1', instance, 'in1', label="air")
+        self.c2 = Connection(self.fuel, 'out1', instance, 'in2', label="fuel")
+        self.c3 = Connection(instance, 'out1', self.fg, 'in1', label="fluegas")
         self.nw.add_conns(self.c1, self.c2, self.c3)
 
     def setup_CombustionEngine_network(self, instance):
@@ -79,29 +79,61 @@ def test_CombustionChamber(self):
         instance.set_attr(lamb=None)
         self.nw.solve('design')
         self.nw._convergence_check()
-        msg = ('Value of thermal input must be ' + str(b.P.val) + ', is ' +
-               str(instance.ti.val) + '.')
+        msg = f'Value of thermal input must be {b.P.val}, is {instance.ti.val}.'
         assert round(b.P.val, 1) == round(instance.ti.val, 1), msg
         b.set_attr(P=None)
 
         # test specified thermal input for CombustionChamber
         instance.set_attr(ti=1e6)
         self.nw.solve('design')
         self.nw._convergence_check()
-        ti = (self.c2.m.val_SI * self.c2.fluid.val['CH4'] *
-              instance.fuels['CH4']['LHV'])
-        msg = ('Value of thermal input must be ' + str(instance.ti.val) +
-               ', is ' + str(ti) + '.')
+        ti = (
+            self.c2.m.val_SI * self.c2.fluid.val['CH4']
+            * instance.fuels['CH4']['LHV']
+        )
+        msg = f'Value of thermal input must be {instance.ti.val}, is {ti}.'
         assert round(ti, 1) == round(instance.ti.val, 1), msg
 
         # test specified lamb for CombustionChamber
         self.c3.set_attr(T=None)
         instance.set_attr(lamb=1)
         self.nw.solve('design')
         self.nw._convergence_check()
-        msg = ('Value of oxygen in flue gas must be 0.0, is ' +
-               str(round(self.c3.fluid.val['O2'], 4)) + '.')
-        assert 0.0 == round(self.c3.fluid.val['O2'], 4), msg
+        o2 = round(self.c3.fluid.val['O2'], 4)
+        msg = f'Value of oxygen in flue gas must be 0.0, is {o2}.'
+        assert 0.0 == o2, msg
+
+    def test_CombustionChamberCarbonMonoxide(self):
+        instance = CombustionChamber('combustion chamber')
+        self.setup_CombustionChamber_network(instance)
+
+        # connection parameter specification
+        air = {'N2': 0.7556, 'O2': 0.2315, 'Ar': 0.0129}
+        fuel = {'CO': 1}
+        self.c1.set_attr(fluid=air, p=1, T=30)
+        self.c2.set_attr(fluid=fuel, T=30, m=1)
+        instance.set_attr(lamb=3)
+
+        self.nw.solve('design')
+        self.nw._convergence_check()
+        assert instance.fuels["CO"]["LHV"] == pytest.approx(10112000, 1e-3)
+
+        molar_flow = {}
+        for c in self.nw.conns["object"]:
+            molar_flow[c.label] = {
+                key: value["mass_fraction"]
+                / value["wrapper"]._molar_mass * c.m.val_SI
+                for key, value in c.fluid_data.items()
+            }
+        o2 = molar_flow["air"]["O2"]
+        co2 = molar_flow["fluegas"]["CO2"]
+        assert o2 == pytest.approx(co2 * 1.5, 1e-3)
+
+        self.c3.set_attr(T=1500)
+        instance.set_attr(lamb=None)
+        self.nw.solve('design')
+        self.nw._convergence_check()
+        assert self.c3.T.val == pytest.approx(1500)
 
     def test_CombustionChamberHighTemperature(self):
         instance = CombustionChamber('combustion chamber')