Injector
Flow Rate
Assuming that the Nitrous has a pressure of ~ 55 Bar and that we have a pressure of 35 Bar in the combustion chamber (figures taken from here) then we can get a rough estimate of the flow rate using a simple injector (i.e. with sharp orifices created using drill bits in a 'shower head' configuration).
Using Q = A*Cd*sqrt((2*DeltaP)/Rho) we can show that for a configuration of n 2mm diameter holes (where Cd is roughly 0.61) then Q = n*3*10^-4 m^3s^-1 and the mass flow rate is .048n kg s^-1.
Recirculation
In order to reduce pressure instabilities it is recommended to have a recirculation zone near the injector by providing a sufficiently large gap between the injector and the top of the fuel grain (will try and upload a diagram of this later).
