Abstract

Combustion properties of cryogenic hydrogen at different conditions are analyzed. Flammability limits, auto-ignition temperature, laminar flame velocities, cryogenic jet fire demonstrate a very high danger due to the higher density of combustion system. A series of more than 100 experiments with hydrogen-air mixtures have been performed at cryogenic temperatures from 90 to 130K and ambient pressure. A wide range of hydrogen concentrations from 8 to 60%H₂ in a shock tube of 5-m long and 54 mm id was tested. Flame propagation regimes were investigated for all hydrogen compositions at three different blockage ratios 0, 30% and 60% as a function of initial temperature. Piezoelectric pressure sensors and InGaAs photo-diodes have been applied to monitor the flame and shock propagation velocity of the combustion process. The critical expansion ratio s* for an effective flame acceleration to the speed of sound was experimentally found at cryogenic temperatures. The detonability criteria for smooth and obstructed channels were used to evaluate the detonation cell sizes at cryogenic temperatures as well. The main peculiarities of cryogenic combustion with respect to the safety assessment were that the maximum combustion pressure was several times higher and the run-up-distance to detonation was two times shorter compared to ambient temperature independent of the lower chemical reactivity at cryogenic conditions. It was found that factors of higher density and expansion ratio lead to higher hydrodynamic flame instability and compensate the lack of reactivity at cryogenic temperatures.

Biography

Prof. Dr. Mike Kuznetsov is currently the Principal Researcher responsible for hydrogen combustion and detonation experiments at the HYKA test site of the Karlsruhe Institute of Technology, Germany. Dr. Kuznetsov is the professor of Nanjing University and an invited Professor at CNRS (Centre National de la recherche scientifique), Orléans, France. He received his bachelor and master degrees in Nuclear Engineering at the Saint-Petersburg Institute of Technology, and PhD degree in Physics of Combustion and Explosions at the Kurchatov Institute, Russia. He was the Head of the Combustion Dynamics Laboratory at the Kurchatov Institute, Russia. His professional experience accounts for almost 40 years. His current research focuses on large-scale experiments on hydrogen combustion and detonations with respect to hydrogen safety. He is a member of ANS, ASME, SMIRT, and the German section of Combustion Institute. He is a member of the Steering Committee of the International Atomic Energy Agency. He was a member of international groups investigating Chernobyl and Fukushima accidents on nuclear power plants. The total number of scientific publications is more than 380, including 3 patents, 127 scientific papers in refereed journals and 250 scientific papers in refereed conference proceedings.