up:: [[Combustion]] Equivalence ratio is the ratio of fuel/oxidizer in current setup to the [[Stoichiometric Ratio]] of fuel to oxidizer $\phi=\frac{\dot m_f/\dot m_o}{(\dot m_f/\dot m_o)_{st}}=\frac{MR}{MR_{st}}$ where MR is [[Mixture Ratio]] Its not commonly used in rocket propulsion but used in the internal combustion engine world $\phi = 1$ - Stoichiometric $\phi < 1$ - Lean $\phi > 1$ - Rich