muller@ecn.purdue.edu (Mark B. Muller) (12/05/90)
From: muller@ecn.purdue.edu (Mark B. Muller) >From: elec140@csc.canterbury.ac.nz >In article <1990Dec3.050627.2654@cbnews.att.com>, henry@zoo.toronto.edu (Henry Spencer) writes: [discussion of eficieny of ramjets deleted] > >If this is true, then where is the distinction between a ramjet and a scramjet? >Is it to do with an external combustion chamber, or is this only one >implementation of a scramjet? > a scramjet is a Supersonic Combustion Ramjet. This means that the flow through the combustion process is supersonic. In a conventional ramjet, even when flying at supersonic speeds, the flow is slowed to subsonic speeds, the fuel added and burned, and then the flow accelerated again before going out the back. The changes in speed are accomplished via the geometry of the inlet and the exhaust nozzle. As far as efficieny goes, it all depends on flight regime. For low subsonic speeds, Turbopros are generally best, while for high subsonic speeds, turbofans are most efficient. In the transonic and low supersonic regime, turbojets become efficient, while at supersonic and high supersonic speeds, ramjets become attractive. At speeds above this (around mach 5), scramjets become "better". Of course, there are other considerations in choice of engines. For example, many subsonic missiles use ramjets or solid rockets to save weight and simplify things, as these engines have few moving parts. *-------------------------------------------------------------------------* * Mark Muller Undergraduate at Purdue University * * muller@gn.ecn.purdue.edu Aeronautics & Astronautics Engineering * *-------------------------------------------------------------------------*