[1D] Refine grid after expanding domain width

The test for a sufficiently wide domain short circuits the normal control logic
which makes a call to refine() after each successful steady-state solve. This
caused failures for certain cases where sucessive solutions on wider grids with
only a few points still failed to satisfy the gradient criterion at the edges of
the domain.

interfaces/cython/cantera/onedim.py

@@ -508,7 +508,7 @@ class FreeFlame(FlameBase):
             # The domain is considered too narrow if gradient at the left or
             # right edge is significant, compared to the average gradient across
             # the domain.
-            if mLeft > 0.05 or mRight > 0.05:
+            if mLeft > 0.02 or mRight > 0.02:
                 raise DomainTooNarrow()
 
             if original_callback:
@@ -527,6 +527,8 @@ class FreeFlame(FlameBase):
                     print('Expanding domain to accomodate flame thickness. '
                           'New width: {} m'.format(
                           self.flame.grid[-1] - self.flame.grid[0]))
+                if refine_grid:
+                    self.refine(loglevel)
 
         self.set_steady_callback(original_callback)
 

interfaces/cython/cantera/test/test_onedim.py

@@ -170,6 +170,16 @@ class TestFreeFlame(utilities.CanteraTest):
         Tad = self.gas.T
         self.assertNear(Tad, self.sim.T[-1], 2e-2)
 
+    def test_auto_width2(self):
+        self.create_sim(p=ct.one_atm, Tin=400, reactants='H2:0.8, O2:0.5',
+                        width=0.1)
+
+        self.sim.set_refine_criteria(ratio=4, slope=0.8, curve=0.8)
+        self.sim.solve(refine_grid=True, auto=True, loglevel=0)
+        self.assertNear(self.sim.u[0], 17.02, 1e-1)
+        self.assertLess(self.sim.grid[-1], 2.0) # grid should not be too wide
+
+
     def test_converge_adiabatic(self):
         # Test that the adiabatic flame temperature and species profiles
         # converge to the correct equilibrium values as the grid is refined