Explain the various types of scramjet combustors.
Scramjet (supersonic combustion ramjet) engines present a much different situation for the combustor than conventional gas turbine engines (scramjets are not gas turbines, as they generally have few or no moving parts). While scramjet combustors may be physically quite different from conventional combustors, they face many of the same design challenges, like fuel mixing and flame holding. However, as its name implies, a scramjet combustor must address these challenges in a supersonic flow environment. For example, for a scramjet flying at Mach 5, the airflow entering the combustor would nominally be Mach 2. One of the major challenges in a scramjet engine is preventing shock waves generated by the combustor from traveling upstream into the inlet. If that were to happen, the engine may unstart, resulting in loss of thrust, amongst other problems. To prevent this, scramjet engines tend to have an isolator section immediately ahead of the combustion zone
