Ettlingen, Germany
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Kuznetsov M.,Karlsruhe Institute of Technology | Grune J.,Pro Science GmbH | Kobelt S.,Karlsruhe Institute of Technology | Sempert K.,Pro Science GmbH | Jordan T.,Karlsruhe Institute of Technology
Fusion Engineering and Design | Year: 2011

This work addresses the hydrogen safety issue of an International Thermonuclear Experimental Reactor (ITER) in case of a loss of vacuum accident (LOVA) scenario. In this scenario, accidentally generated hydrogen mixed with injected air could be ignited at reduced, sub-atmospheric pressures. The general question is whether the induced combustion pressure could exceed the ITER vacuum vessel design pressure. The paper presents the results of large scale dynamic experiments on hydrogen ignition and combustion at reduced pressures in the presence of a turbulent air jet injected into the hydrogen atmosphere. Experiments have been performed in a cylindrical vessel with a volume of 8.8 m3 filled with hydrogen at an initial pressure of 200 mbar. The orifice size of 6 mm i.d. was chosen to model in the same time scale the real leak through a 100 mm × 100 mm area into the ITER vacuum vessel with a volume of about 3000 m3. The structure and dynamics of the air jet into the hydrogen atmosphere at different initial pressures were investigated using microscopic liquid droplets as markers. During the combustion tests, it was found that more distant ignition positions and stronger ignition energies lead to maximum combustion pressures that are lower than the design pressure of the ITER vacuum vessel. © 2011 Elsevier B.V. All rights reserved.


Grune J.,Pro Science GmbH | Sempert K.,Pro Science GmbH | Kuznetsov M.,Karlsruhe Institute of Technology | Breitung W.,Karlsruhe Institute of Technology
International Journal of Hydrogen Energy | Year: 2011

In order to simulate an accidental hydrogen release from the low pressure pipe system of a hydrogen vehicle a systematic study on the nature of transient hydrogen jets into air and their combustion behaviour was performed at the FZK hydrogen test site HYKA. Horizontal unsteady hydrogen jets with an amount of hydrogen up to 60 STP dm3 and initial pressures of 5 and 16 bar have been investigated. The hydrogen jets were ignited with different ignition times and positions. The experiments provide new experimental data on pressure loads and heat releases resulting from the deflagration of hydrogen-air clouds formed by unsteady turbulent hydrogen jets released into a free environment. It is shown that the maximum pressure loads occur for ignition in a narrow position and time window. The possible hazard potential arising from an ignited free transient hydrogen jet is described. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.


Friedrich A.,Pro Science GmbH | Veser A.,Pro Science GmbH | Stern G.,Pro Science GmbH | Kotchourko N.,Pro Science GmbH
International Journal of Hydrogen Energy | Year: 2011

In the frame of the EC-funded project HYPER [1] Pro-Science GmbH performed distribution and combustion experiments on the hazard potential of a severe hydrogen leakage inside a fuel cell cabinet using a generic enclosure model with the dimensions of a commercially available fuel cell application. Hydrogen amounts from 1.5 to 15 g were released within 1 s into the enclosure. In distribution experiments the effects of different venting characteristics and different amounts of internal enclosure obstruction on the hydrogen concentrations measured at fixed positions in- and outside the model were investigated. Subsequently combustion experiments with ignition positions in- and outside the enclosure and two different ignition times were performed. BOS (Background-Oriented-Schlieren) observation combined with pressure and light emission measurements were performed to describe characteristics and hazard potential of the induced hydrogen combustions. The experiments provide new experimental data on the distribution and combustion behaviour of hydrogen releases into a partly vented and partly obstructed enclosure with different venting characteristics. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.


Kotchourko N.,Pro Science GmbH | Kuznetsov M.,Karlsruhe Institute of Technology | Kotchourko A.,Karlsruhe Institute of Technology | Grune J.,Pro Science GmbH | And 2 more authors.
International Journal of Hydrogen Energy | Year: 2014

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. Originally, the BOS procedure was developed for visualization and acquiring qualitative information only. In the current work it was shown that if supplementary information concerning the studied object can be accomplished, then in some cases not only qualitative but quantitative information can be obtained as well. In the case of axial symmetry of an object, the BOS method can be used for evaluation of the distribution for both concentration gradient and the concentration itself. The method was applied for the study of free expanding vertical axisymmetric hydrogen jets. In the course of the study the quasi-stationary hydrogen jet evolved from a nozzle of 21 mm internal diameter with constant mass flow rate equal to 3 g/s was examined. To validate the concentration values obtained using the proposed technique an independent set of simultaneous measurements were performed by sampling probe method. Various locations of 'probe capturing' to be measured by the gas analyzer at different locations were utilized. To obtain source images the digital single-lens reflex camera with a resolution 4368 × 2912 pixels was used. The raw images were processed with a computer program based on a PIV-type cross-correlation algorithm extended with the proposed procedure. Results of the trials demonstrated ability of the proposed technique successfully predict concentration distributions with satisfactory accuracy. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Grune J.,Pro Science GmbH | Sempert K.,Pro Science GmbH | Kuznetsov M.,Karlsruhe Institute of Technology | Jordan T.,Karlsruhe Institute of Technology
International Journal of Hydrogen Energy | Year: 2014

Spontaneous ignition processes due to high pressure hydrogen releases into air are known phenomena. The sudden expansion of pressurized hydrogen into a pipe, filled with ambient air, can lead to a spontaneous ignition with a jet fire. This paper presents results of an experimental investigation of the visible flame propagation and pressure measurements in 4 mm extension tubes of up to 1 m length attached to a bulk vessel by a rupture disc. Transparent glass tubes for visual observation and shock wave pressure sensors are used in this study. The effect of the extension tube length on the development of a stable jet fire after a spontaneous ignition is discussed. © 2014 Hydrogen Energy Publications, LLC. All rights reserved.


Grune J.,Pro Science GmbH | Sempert K.,Pro Science GmbH | Kuznetsov M.,Karlsruhe Institute of Technology | Jordan T.,Karlsruhe Institute of Technology
International Journal of Hydrogen Energy | Year: 2014

In order to simulate an accidental hydrogen release from the high pressure pipe system of a hydrogen facility a systematic study on the nature of transient hydrogen jets into air and their combustion behavior was performed at the KIT hydrogen test site HYKA. Horizontal unsteady hydrogen jets from a reservoir of 0.37 dm3 with initial pressures of up to 200 bar have been investigated. The hydrogen jets released via round nozzles 3, 4, and 10 mm were ignited with different ignition times and positions. The experiments provide new experimental data on pressure loads and heat releases resulting from the deflagration of hydrogen-air clouds formed by unsteady turbulent hydrogen jets released into a free environment. It is shown that the maximum pressure loads occur for ignition in a narrow position and time window. The possible hazard potential arising from an ignited free transient hydrogen jet is described. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Kuznetsov M.,Karlsruhe Institute of Technology | Kobelt S.,Karlsruhe Institute of Technology | Grune J.,Pro Science GmbH | Jordan T.,Karlsruhe Institute of Technology
International Journal of Hydrogen Energy | Year: 2012

Hydrogen behavior at elevated pressures and temperatures was intensively studied by numerous investigators. Nevertheless, there is a lack of experimental data on hydrogen ignition and combustion at reduced sub-atmospheric pressures. Such conditions are related to the facilities operating under vacuum or sub-atmospheric conditions, for instance like ITER vacuum vessel. Main goal of current work was an experimental evaluation of such fundamental properties of hydrogen-air mixtures as flammability limits and laminar flame speed at sub-atmospheric pressures. A spherical explosion chamber with a volume of 8.2 dm 3 was used in the experiments. A pressure method and high-speed camera combined with schlieren system for flame visualization were used in this work. Upper and lower flammability limits and laminar flame velocity have been experimentally evaluated in the range of 4-80% hydrogen in air at initial pressures 25-1000 mbar. An extraction of basic flame properties as Markstein length, overall reaction order and activation energy was done from experimental data on laminar burning velocity. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.


Yanez J.,Karlsruhe Institute of Technology | Kuznetsov M.,Karlsruhe Institute of Technology | Grune J.,Pro Science GmbH
Combustion and Flame | Year: 2015

This work addresses the experimental investigation and analytical interpretation of a flame subject to acoustic-parametric instability exited by self-generated pressure pulses. The research presented herein was carried out with lean hydrogen-air mixtures during flame propagation in a smooth channel with an open end. It was found that very lean mixtures with hydrogen concentrations in air of less than 14% vol. H2 generate acoustic oscillations due to flame instabilities, which, in turn, significantly influence the propagation of the flame. Above a 14% vol. H2 concentration in the air, the flame becomes relatively stable with respect to self-generated acoustic perturbations. It was also found that an external polychromatic sound with a dominant frequency of 1000Hz inhibits the instabilities and results in a reduced flame propagation velocity. Numerical solutions of the Searby and Rochwerger analytical formulation for the acoustic-parametric instability were utilized in order to analyze the experiments and study the influence of different parameters on the existence of a spontaneous transition from the acoustic to the parametric instability. © 2015 The Combustion Institute.


Grune J.,Pro Science GmbH | Sempert K.,Pro Science GmbH | Kuznetsov M.,Karlsruhe Institute of Technology | Jordan T.,Karlsruhe Institute of Technology
Journal of Loss Prevention in the Process Industries | Year: 2013

This paper presents results of an experimental investigation on fast flame propagation and the deflagration-to-detonation transition (DDT) and following detonation propagation in a semi-confined flat layer filled with stratified hydrogeneair mixtures. The experiments were performed in a transparent, rectangular channel open from below. The combustion channel has a width of 0.3 m and a length of 2.5 m. The effective layer thickness in the channel was varied by using different linear hydrogen concentration gradients. The method to create quasi-linear hydrogen concentration gradients that differ in the range and slope is also presented. The ignited mixtures were accelerated quickly to sonic flame speed in the first obstructed part of the channel. The interaction of the fast flame propagation with different obstacle set-ups was studied in the second part of the channel. The experimental results show an initiation of DDT by one additional metal grid in the obstructed semi-confined flat layer. Detonation propagation and failed detonation propagation were observed in obstructed and unobstructed parts of the channel. © 2013 Elsevier Ltd.


Grune J.,Pro Science GmbH | Sempert K.,Pro Science GmbH | Haberstroh H.,Karlsruhe Institute of Technology | Kuznetsov M.,Karlsruhe Institute of Technology | Jordan T.,Karlsruhe Institute of Technology
Journal of Loss Prevention in the Process Industries | Year: 2013

This paper presents results of an experimental investigation on the deflagration and deflagration-to-detonation transition (DDT) in an obstructed (blockage ratio BR = 50%), semi-confined flat layer filled with uniform hydrogen-air mixtures. The effect of mixture reactivity depending on flat layer thickness and its width is studied to evaluate the critical conditions for sonic flame propagation and the possibility for detonation onset. The experiments were performed in a transparent, rectangular channel with a length of 2.5 m. The flat layer thickness was varied from 0.06 to 0.24 m and the experiments were performed for different channel widths of 0.3, 0.6 and 0.9 m. The experimental results show flame velocity vs. hydrogen concentration for different thicknesses and widths of the semi-confined flat layer. Three different flame propagation regimes were observed: slow subsonic flame (M << 1), sonic deflagration (M ~ 1) and detonation (M >> 1). It is shown that flame acceleration (FA) to sonic speed is independent of the width of the flat layer. The critical expansion ratio for effective flame acceleration to sonic speed was found to be linearly dependent on the reciprocal layer thickness. © 2011 Elsevier Ltd.

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