Implement reduced head and flow method

We should implement the reduced head and flow method for conversion of cases where we only have one speed.

```math
\
y_{p_{red}} = y_p(k_v Z_1 R T_1)_{ref} / (k_v Z_1 R T_1)
```

```math
\dot{V}_{red} = \dot{V}\sqrt{(k_v Z_1 R T_1)_{ref} / (k_v Z_1 R T_1)}
```