One thing that was found to significantly help reduce instability that was not fuel related is the addition of swirl to the oxidiser flow ie by having a swirl injector.
Making this is not straight forward but it has been an interesting challenge.
Due to the design of the injector housing, I have a 15mm disc that can be utilised to either be the injectors or as I found out after trying to drill small holes in at a compound angle, use it to house removable inserts.
The current tune for the motor calls for 8 x 1.6mm injectors hence I went with a 45deg spacing and the maximum inclination I could arrange on my mill with the rotary table installed that being 25deg. After a little bit of modelling I came up with a 14deg angle for bringing the streams towards the centre such that they would not impinge on the preheater insulation sleeve.
Due to the compound angle, a number of machining steps are needed to drill the holes 'straight' and the give the injector heads (M5x16mm brass hex head bolts) room to pull down onto a flat.
In the end, it came out quite well
But installing some longer screws it is easier to visualise the stream paths
Will make up the injectors as soon as the brass bolts get here..... they are not easy to find these days!
