Luminescent Measurement Systems for the Investigation of a Scramjet Inlet-Isolator

Abstract

Scramjets have become a main focus of study for many researchers, due to their application as propulsive devices in hypersonic flight. This entails a detailed understanding of the fluid mechanics involved to be able to design and operate these engines with maximum efficiency even at their off-design conditions. It is the objective of the present cold-flow investigation to study and analyse experimentally the mechanics of the fluid structures encountered within a generic scramjet inlet at M = 5. Traditionally, researchers have to rely on stream-thrust analysis, which requires the complex setup of a mass flow meter, a force balance and a heat transducer in order to measure inlet-isolator performance. Alternatively, the pitot rake could be positioned at inlet-isolator exit plane, but this method is intrusive to the flow, and the number of pitot tubes is limited by the model size constraint. Thus, this urgent need for a better flow diagnostics method is addressed in this paper. Pressure-sensitive paint (PSP) has been applied to investigate the flow characteristics on the compression ramp, isolator surface and isolator sidewall. Numerous shock-shock interactions, corner and shoulder separation regions, as well as shock trains were captured by the luminescent system. The performance of the scramjet inlet-isolator has been shown to improve when operated in a modest angle of attack.

Static and Wind-on Performance of Polymer-Based Pressure-Sensitive Paints Using Platinum and Ruthenium as the Luminophore

“…Furthermore, the flow pattern over the surface of an object can be visualised through the “colour map” obtained from the PSP measurements. Throughout the years, many pressure-sensitive paint formulations have been developed and applied to different scenarios, ranging from typical surface pressure measurements on various objects in wind tunnel tests at different speeds [9,10,11,12,13,14,15] to flow and shock structures visualisation [14,15,16], as well as used for measuring altitudes [17]. …”

Potential of Micro-Vortex Generators in Enhancing the Quality of Flow in a Hypersonic Inlet-Isolator

“…The dimension of the scramjet model used in the first and second part of the experiment follows the scramjet geometry reported in Idris et al, [10]. The MVG arrays for the first and second part of the experiments were manufactured to similar dimension reported by Idris et al, [16].…”

“…In the worst-case scenario, the boundary layer separation bubble can induce inlet-unstart, where the flow is totally restricted from going into the combustion chamber thus causing total engine failure. Hence, it has become the focus of many studies in recent years to understand the shock-boundary layer interactions of the flow at the scramjet inlet/isolator section [5][6][7][8][9][10][11][12].…”

Polystyrene Oxygen Optodes Doped with Ir(III) and Pd(II) meso-Tetrakis(pentafluorophenyl)porphyrin Using an LED-Based High-Sensitivity Phosphorimeter

“…For the calibration curves (static sensitivity of the sensors), different concentrations of O were used with nitrogen gas as an inert component (from gas cylinders with an absolute uncertainty <0.05%; Praxair, Araucária, Brazil). The respective phosphorescence lifetimes were obtained from 100 consecutive measurements, with each measurement corresponding to the average of 8 successive decays (SNR is proportional to the square root of the number of decays averaged) [ 33 ]. The acquisition interval of phosphorescence signal used to calculate lifetimes was considered valid between 5 s (time delay after switching off LED to start the acquisition) [ 12 , 34 ], and five-times the time constant pre-measured.…”