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## The influence of gas doping on self-ignition of hydrogen during high-pressure release into air

### Wojciech Rudy

#### Abstract

Hydrogen is the most widespread element in the universe. Its unique properties let one conclude that in the not so distant future it may be one of the main energy carriers in the world. Hydrogen usage entails some problems especially in a matter of safety. These problems are caused by some of hydrogen’s properties, namely: low density, propensity for leakage, low ignition energy and wide flammability range which creates ignition, explosion or even detonation hazards. Low hydrogen density (at normal conditions) enforces high pressure gaseous or low pressure liquid state storage to get rational tank dimensions. High pressure hydrogen ignition during discharge into the air and without a distinct ignition source had been reported for the first time in the 20s of the 20th century. From that time hydrogen was called ‘self ignitable’. In the 70s of the 20th century ‘diffusion ignition’ was described as an ignition in a thin diffusion layer between hydrogen and pre-heated air by leading shock wave. In recent years one could observe an increase in interest in hydrogen technologies and safety issues corresponding to them, including uncontrolled ignition during discharge into the air from high-pressure installations. Latest experimental as well numerical works focus mainly on the detailed description of the self-ignition mechanism according to different initial and boundary conditions including: initial pressure influence, nozzle diameter, extension channel geometry: diameter, length, cross-section shape or obstacle presence in front of the hydrogen stream. Despite of this research there is still lack of experimental data concerning the influence of different gases doping to hydrogen on the self-ignition occurrence. This kind of data would allow to understand the nature of the self-ignition phenomenon itself and deliver the knowledge for prevention or at least for decreasing the self-ignition probability. This thesis is a result of experimental and numerical works performed by the author on hydrogen and hydrogen blends (with methane or nitrogen) ignition processes during highpressure release into the air. The experimental research and zero-dimensional calculations (Cantera code) were conducted in the Faculty of Aeroengines in the Institute of Heat Engineering of Warsaw University of Technology, while two-dimensional calculations (KIVA3V code) were performed during author’s 10-week fellowship at the University of Warwick under prof. Jennifer Wen supervision. Both experimental and numerical research showed significant gas (methane or nitrogen) doping to hydrogen influence on the self-ignition process. For the same doping fractions (5% and 10% vol.) a stronger effect of methane addition rather than nitrogen addition was observed. The experimental research was carried out for initial pressure range of 2 – 17.2 MPa, extension tubes diameters: 6, 10, and 14 mm and lengths: 10 – 100 mm. The highest doping influence was recorded for the longest tube of 100 mm. For this tube length 5% of doping gas in hydrogen blend resulted in 2.46 and 2.12 increase in initial pressure necessary for the ignition to occur for methane and nitrogen respectively in comparison to pure hydrogen case. 10% of nitrogen caused 2.85 increase in the minimum pressure of the ignition and 10% of methane did not end in ignition for the maximum channel length (100 mm) and initial pressure range up to 15.3 MPa.
Record ID
WUTc8f1e45c497e43cfa086d9a3c809cfd0
Diploma type
Doctor of Philosophy
Author
Title in Polish
Wpływ domieszkowania gazów na występowanie samozapłonu wodoru podczas wysokociśnieniowego wypływu do powietrza
Title in English
The influence of gas doping on self-ignition of hydrogen during high-pressure release into air
Language
(en) English
Certifying Unit
Faculty of Power and Aeronautical Engineering (FPAE)
Discipline
energetics / (technology domain) / (technological sciences)
Status
Finished
Defense Date
15-12-2014
Title date
16-12-2014
Supervisor
External reviewers
Tomasz Dobski Tomasz Dobski,, External affiliation of publication: Politechnika Poznańska
Andrzej Szlęk Andrzej Szlęk,, External affiliation of publication: Silesian University of Technology
Pages
119
Keywords in English
xxx
Abstract in English
Hydrogen is the most widespread element in the universe. Its unique properties let one conclude that in the not so distant future it may be one of the main energy carriers in the world. Hydrogen usage entails some problems especially in a matter of safety. These problems are caused by some of hydrogen’s properties, namely: low density, propensity for leakage, low ignition energy and wide flammability range which creates ignition, explosion or even detonation hazards. Low hydrogen density (at normal conditions) enforces high pressure gaseous or low pressure liquid state storage to get rational tank dimensions. High pressure hydrogen ignition during discharge into the air and without a distinct ignition source had been reported for the first time in the 20s of the 20th century. From that time hydrogen was called ‘self ignitable’. In the 70s of the 20th century ‘diffusion ignition’ was described as an ignition in a thin diffusion layer between hydrogen and pre-heated air by leading shock wave. In recent years one could observe an increase in interest in hydrogen technologies and safety issues corresponding to them, including uncontrolled ignition during discharge into the air from high-pressure installations. Latest experimental as well numerical works focus mainly on the detailed description of the self-ignition mechanism according to different initial and boundary conditions including: initial pressure influence, nozzle diameter, extension channel geometry: diameter, length, cross-section shape or obstacle presence in front of the hydrogen stream. Despite of this research there is still lack of experimental data concerning the influence of different gases doping to hydrogen on the self-ignition occurrence. This kind of data would allow to understand the nature of the self-ignition phenomenon itself and deliver the knowledge for prevention or at least for decreasing the self-ignition probability. This thesis is a result of experimental and numerical works performed by the author on hydrogen and hydrogen blends (with methane or nitrogen) ignition processes during highpressure release into the air. The experimental research and zero-dimensional calculations (Cantera code) were conducted in the Faculty of Aeroengines in the Institute of Heat Engineering of Warsaw University of Technology, while two-dimensional calculations (KIVA3V code) were performed during author’s 10-week fellowship at the University of Warwick under prof. Jennifer Wen supervision. Both experimental and numerical research showed significant gas (methane or nitrogen) doping to hydrogen influence on the self-ignition process. For the same doping fractions (5% and 10% vol.) a stronger effect of methane addition rather than nitrogen addition was observed. The experimental research was carried out for initial pressure range of 2 – 17.2 MPa, extension tubes diameters: 6, 10, and 14 mm and lengths: 10 – 100 mm. The highest doping influence was recorded for the longest tube of 100 mm. For this tube length 5% of doping gas in hydrogen blend resulted in 2.46 and 2.12 increase in initial pressure necessary for the ignition to occur for methane and nitrogen respectively in comparison to pure hydrogen case. 10% of nitrogen caused 2.85 increase in the minimum pressure of the ignition and 10% of methane did not end in ignition for the maximum channel length (100 mm) and initial pressure range up to 15.3 MPa.
Thesis file
• File: 1
Rudy.pdf
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Citation count
2

Uniform Resource Identifier
https://repo.pw.edu.pl/info/phd/WUTc8f1e45c497e43cfa086d9a3c809cfd0/
URN
urn:pw-repo:WUTc8f1e45c497e43cfa086d9a3c809cfd0

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