In hypersonic engines, the air gets compressed through aerodynamics and forward velocity. It does not use rotating compressors. When airstream gets injected by hydrogen fuel, it results in combustion, resulting in high forward thrust due to acceleration of exhaust air. You can read about the Hypersonic Technology Demonstrator Vehicle (HSTDV) – unmanned scramjet technology of DRDO in the given link.

Further readings:

1. Advanced Technology Vehicle – India, one of the 4 Countries To Develop Scramjet Engine
2. Reusable Launch Vehicle – Technology Demonstrator (RLV – TD)