We have accomplished the sought objectives and have progressed further than anticipated.
The experimental facility was manufactured in 2018/9, satisfying O1, and providing the test-rig used in EPIC.
We developed a 1D HRCARS approach to measure gas-phase temperature at high pressures and temperatures. We then used 1D HRCARS to resolve 1D gas temperatures within the thermal boundary layer during gaseous compression and expansion events within facility. HRCARS was combined with PT and LIF to study the transient gaseous heat loss for three important processes occurring at gas/wall interfaces: (a) unburnt gas polytropic compression, (b) FWI, and (c) post-flame gas expansion. Findings are the first of their kind that resolve single-shot, transient heat loss measurements within a developing boundary layer, which satisfy objectives O2 and O3. We have also advanced N2 linewidth models used in Raman spectroscopy.
For O4, we have succeeded the original objective. We measured wall temperature and flame front distributions in a two-walled crevice to investigate transient heat transfer and flame quenching. We collaborated with partners from Princeton University (US) and ONERA (France) to synthesize a new phosphor (ScVO4:Bi3+), providing precise wall temperature measurements at high repetition rates. Our work led to the development of a two-wall quenching model. We further extended our work to 2D high-speed PT. In this work, we discovered new attributes of heat fluxes associated with intrinsic flame features of a flame, including those associated with thermodiffusive instabilities imposed from lean H2-air flames. We have further expanded PT into the field of fire science to study the heat transfer mechanisms responsible for the rate of flame spread along solid surfaces.
We achieved O5 objectives during EPIC, however, the full progression of O5 finished shortly after the duration EPIC in Oct. 2023. This delay was due to the ambitious nature of EPIC and the limitations of COVID protocols. In O5, we developed a novel wavelet-based Optical Flow (wOF) algorithm for ultra-high spatial resolution velocity fields in wall bounded turbulent flows. This effort has enabled the impressive ability to resolve momentum and mass transport within boundary layers. This work was extended further to resolve the evolution of the turbulent boundary layer during FWI, which combined wOF, CARS and LIF diagnostics. Findings describe deviation from canonical boundary layer flows, and provides a priori information for correct modelling of these unique boundary layer flows. Additional measurements of HRCARS, PT, and PIV were conducted during EPIC, and publications resulted shortly after the conclusion of EPIC. In that work, for the first time we resolved the thermal flame structure (flame temperature, thermal flame gradients) in response to wall heat loss.
