The unstart phenomena in a model scramjet with free stream Mach number of 4.5 were investigated at an arc-heated hypersonic wind tunnel. High-speed schlieren imaging and high resonance frequency pressure measurements used to capture the flow features during process. Three conditions tested: (i) low-enthalpy mass loading, (ii) high-enthalpy loading (iii) heat release. It was revealed that threshold time from onset completion depended strongly on rate exchange. negative addition (cooling)...

Abstract

Ethylene flame dynamics in a model scramjet installed an open test section of arc-heated hypersonic wind tunnel are experimentally investigated with freestreams Mach 4.5–9. An ethylene fuel jet is injected into the that autoignited by high-enthalpy flows compressed and decelerated train shock waves boundary layers developing isolator/combustor. The behavior captured high-speed movie camera through optical access windows on characterized surface pressure/temperature traces recorded at five...

Cavity-enhanced combustion in an optical axisymmetric scramjet with a diverging combustor is experimentally investigated Mach 4.5 flows. The emphasizes generic and flameholding dynamics without the corner boundary-layer effects that can distort flame propagation rectangular geometries. Combustion characterized by pressure distributions along wall as well heat flux measurements at exit. Flame structures are resolved instantaneous hydroxyl planar laser-induced fluorescence imaging. cavity...

Dual-mode operation and mode transition are experimentally investigated in optical axisymmetric scramjets Mach 4.5 flows. The scramjet emphasizes generic combustion flameholding dynamics without the corner boundary-layer effects that can distort flame propagation rectangular geometries. Flow characterized by pressure transducers distributed along combustor heat flux measurements at exit. Flame structures resolved instantaneous OH planar laser-induced fluorescence high-speed chemiluminescence...

A new pulsed-arc-heated hypersonic wind tunnel facility, designated as ACT-1 (Arc-heated Combustion Test-rig 1), has been developed and built at the University of Notre Dame in collaboration with Illinois Urbana-Champaign Alta S.p.A. The aim design is to provide a suitable test platform for experimental studies on supersonic turbulent combustion phenomena. composed high temperature gas-generator system model scramjet combustor that installed an open-type vacuum section facility. designed...

The influences of inlet geometry modification on flow and combustion dynamics are experimentally investigated in a model supersonic ramjet (scramjet) installed Mach 4.5 high-enthalpy air freestreams. upper-lip angle (6, 12, 20 deg) the intake contraction ratio (1.3 1.9) chosen as generic design parameters varied. With geometries systematically modified, flowfields inside scramjet visualized at cold conditions (room temperature) using planar laser Rayleigh scattering method (wherein radiation...

Incipient choking and unstart initiation mechanisms are investigated experimentally in an ethylene-fueled constant-area direct-connect supersonic combustor with a circular cross section (diameter of 28 mm) full optical access. The experiments performed the ACT-II pulsed arc-heated hypersonic wind tunnel University Illinois at Urbana–Champaign. extended test time (up to 1 s) visualization capabilities allowed by geometry represent major novelties as compared previous studies. combination...

A new direct-connect supersonic combustor has been designed and tested for the study of plasma-assisted combustion in ACT-II tunnel. Laser-induced plasma ignition was investigated an ethylene-fueled cavity flame holder at Mach 3. Combustor design, geometry, flow characteristics are discussed first part paper. The includes a holder, where ethylene fuel is injected, mixed with entrained air, ignited. Two injector configurations included, one horizontal vertical, which were such way as to...

In this work, time-resolved spectroscopic measurements of non-equilibrium emission from the plenum chamber a Mach 6 arc-heated tunnel are evaluated under three different enthalpy conditions (low, medium, and high) operating with pure N2. Two high-resolution spectral locations, 338–361 nm 373–396 nm, targeted at each condition for total 20 usable time frames. These spectra centered on two vibrational bands (v = 0 +1) first negative system N2+ (B → X), allowing estimations rotational...

Quantitative measurements in high-enthalpy hypersonic wind tunnels, such as arc-heated facilities, have always represented a formidable challenge. Flow contamination, non-uniformity, non-equilibrium thermochemistry, turbulence and electromagnetic noise create an extremely harsh environment for diagnostics, leading to poor signal-to-noise ratios large uncertainties. Tunable-Diode Laser Absorption Spectroscopy (TDLAS) has been proven robust reliable technique investigate high-speed,...

Turbulent flame dynamics in an ethylene-fueled model scramjet is experimentally investigated Mach 4.5 freestream flows with a total temperature of 2600 K using pulsed arc-heated hypersonic wind-tunnel facility at the University Notre Dame. Gaseous ethylene fuel injected into combustor through supersonic nozzle, and autoignited by high-enthalpy that are compressed decelerated train shock waves isolator/combustor. The turbulence level manipulated to investigate influence on combustor. General...

The development of well-characterized, reliable, and cost-effective platforms for experimental aerothermodynamic research is a key factor to advance hypersonic technology. use high-enthalpy tunnels capable producing flows representative flight conditions in high demand material survivability tests, gas/surface interaction studies, high-speed combustion, nonequilibrium, radiative gas dynamics. A new Mach 6, wind tunnel has been constructed tested at the University Tennessee. facility...

Inlet unstart mechanism in an ethylene-fueled model scramjet is investigated using a pulsed arc-heated hypersonic wind tunnel simulating supersonic/hypersonic flight conditions (Mach 4.5, 6, and 9 flows). The inlet ca used by excessive heat release from ethylene combustion reactions with Mach 4.5 freestream flows of 500 K static temperature 2,500 stagnation temperature. Flame evolution during test time approximately 150 milliseconds optically resolved fast framin g camera. An flame...