The case studies are intended to show typical examples from the spectrum of the work carried out and provide the available tools for experimental and theoretical safety investigations. Not infrequently, it becomes clear that more accurate scientific analyzes of distribution and combustion states can reveal and explain new surprising effects with safety relevance.
DDT criteria for hydrogen in flat layer
Flame in the premixed combustions, which is initiated by a weak source of energy, begins to propagate slowly with a velocity which depends on the mixture reactivity and varies between several centimeters and several meters per second. Due to existence of obstacles and volume confinement, the flame can undergo strong acceleration and reach velocities up to hundreds meters per second.
Many of the topical studies dedicated to the flame acceleration were performed in obstructed channels and have devoted a special emphasis to the deflagration to detonation transition (DDT). The criteria able to predict flame propagation regime in tube-like configurations were developed. Later such criteria were extended to take into account possible venting. However many of the practical configurations were not studied.
The main goal of the presented study was, on the basis of the parametric study results, try to refine the requirements to geometrical configurations necessary to induce fast flame propagation regime. As a result of the numerical experiments, a criterion accounting the geometrical configuration of the facility and obstacles required for flame acceleration was elaborated.
Concentration measurements in a round hydrogen jet using Background Oriented Schlieren technique
Concentration measurements are of major importance in the studies of the dynamics of gaseous systems. The conventional techniques, such as ‘probe capturing’ detectors and ultra-sound transducers exhibit multiple shortcomings. For example, in case of ‘probe capturing’ the slow response time, and for ultra-sound detectors the low spatial resolution are their typical deficiencies. In the contrast, the optical techniques are commonly free from many disadvantages of the contact methods. The current work is devoted to the development and the usability evaluation of the technique for the concentration measurements based on the Background Oriented Schlieren (BOS) method. Numerous examples demonstrate a possibility to obtain highly detailed BOS object images thus confirming potential of the method as a comprehensive data source. Originally BOS procedure was developed for visualization and acquiring qualitative information only [1-3].