Aerospace Engineering Colloquium, Joel Mathew Flammability and Explosion Risk for Novel Fuels/ Working Fluids

Have you ever wondered what it takes to study flames that move so slowly you can almost see them 
dance? As environmental concerns push us to explore cleaner energy and refrigerants, new challenges 
arise when working with fuels like ammonia (NH₃) and refrigerants such as R-32 and R-1234yf. When 
mixed with air, these compounds can sustain flames with very low laminar flame speeds—less than
10 cm/s. But studying these slowly propagating flames isn’t as simple as with typical 
hydrocarbon-fueled flames. Due to
their  sluggish  nature,  they’re  heavily  influenced  by  gravity, buoyancy, and radiation heat 
loss.
In this talk, I’ll share my innovative approach to studying slowly propagating flames by developing 
a general methodology that is applied to NH₃/air flames, using a clever twist—dropping them! A
low-cost, lab-scale drop tower was built to minimize the effects of buoyant convection, allowing 
for the study of these delicate, slow flames in free fall. Additionally, a computational model 
(SRADIF) was developed to account for the radiation heat loss. By combining this methodology with 
experiments over a range of fuel-air ratios, we discovered just how crucial it is to study these 
flames in free fall. Using static setups or failing to account for radiation leads to significant 
errors in flame speed measurements. I’ll also show how comparing  experimental  data  with  
simulations is essential  for understanding these fascinating flames. So, if you’re ready to see
combustion from a new perspective, this talk is for you!