Say I want to make a reverse hybrid rocket motor, that runs on a gaseous/liquid fuel which is passed by a solid oxidizer. Would KNO3 make a good oxidizer? Or does this concept not work with Liquid fuels?
In theory this should work, You may run into problems regarding keeping the potassium nitrate solid as it may tend to fall apart. Finding a binder that would keep the potassium nitrate solid but not turn itself into a solid fuel may be a challenge. You could also maybe just compact the potassium nitrate onto itself to hold its shape. Either way it will be a challenge but again in theory this should work.