Shock enhancement and control of hypersonic mixing and combustion

Abstract

The possibility that shock enhanced mixing can
\nsubstantially increase the rate of mixing between
\ncoflowing streams of hydrogen and air has been
\nstudied in experimental and computational investigations.
\nEarly numerical computations indicated that
\nthe steady interaction between a weak shock in air
\nwith a coflowing hydrogen jet can be well approximated
\nby the two-dimensional time-dependent interaction
\nbetween a weak shock and an initially circular
\nregion filled with hydrogen imbedded in air. An experimental
\ninvestigation of the latter process has been
\ncarned out in the Caltech 17 Inch Shock Tube in experiments
\nin which the laser induced fluorescence of
\nbyacetyl dye is used as a tracer for the motion of the
\nhelium gas after shock waves have passed across the
\nhelium cylinder. The flow field has also been studied
\nusing an Euler code computation of the flow field.
\nBoth investigations show that the shock impinging
\nprocess causes the light gas cylinder to split into two
\nparts. One of these mixes rapidly with air and the
\nother forms a stably stratified vortex pair which mixes
\nmore slowly; about 60% of the light gas mixes rapidly
\nwith the ambient fluid. The geometry of the flow field
\nand the mixing process and scaling parameters are
\ndiscussed here. The success of this program encouraged
\nthe exploration of a low drag injection system in
\nwhich the basic concept of shock generated streamwise
\nvorticity could be incorporated in an injector for
\na Scramjet combustor at Mach numbers between 5
\nand 8. The results of a substantial computational
\nprogram and a description of the wind tunnel model and preliminary experimental results obtained in the
\nHigh Reynolds Number Mach 6 Tunnel at NASA Langley
\nResearch Center are given here.