Mach Diamond specializes in injector design for bipropellant rocket engines using hypergolic propellants.

The Mach Diamond injector in the photo has 72 pairs of angled orifices, each pair called a “doublet”.  The propellants do not mix until injected into the combustion chamber.  It is an “unlike doublet” design, where each doublet impinges an oxidizer stream with a fuel stream to cause atomization and mixing. A “like doublet”, in contrast, impinges fuel on fuel and oxidizer on oxidizer.

A row of outward-tilted fuel orifices is utilized to impinge liquid fuel on the thrust chamber wall to provide cooling to the thrust chamber. These are called “boundary-layer coolant”, or “BLC” orifices.

A later version of the injector incorporates acoustic cavities into the injector design, which is not shown until the patent application is submitted. Acoustic cavities are tuned recesses adjacent to the combustion chamber to dampen pressure oscillations. The acoustic cavity is a passive device that dampens the pressure oscillations as follows: the pressure wave enters the acoustic cavity, bounces off of the closed bottom of the acoustic cavity, and returns to cancel the next wave entering the cavity. The cavity depths are “tuned” to the frequencies and modes of the combustion instabilities causing the pressure oscillations.