PARALLEL THREE-DIMENSIONAL NUMERICAL SIMULATION OF HYDROGEN SUDDEN RELEASE THROUGH A SONIC JET
Reza Khaksarfard and Marius Paraschivoiu
ConcordiaUniversity
Montreal, Quebec, Canada
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SESSION: 1.1 Hydrogen release, mixing and distribution
Abstract
The pollution problems and global warming due to carbon dioxide and other emissions increases the need for a cleaner source of energy such as hydrogen. Hydrogen is an affordable, low-polluting, renewable and efficient energy, but investigating the parameters related to combustibility of hydrogen shows that hydrogen is combustible at concentrations between 4% and 74%.Furthermore, Hydrogen flame speed is very high in comparison with other gases such as methane. Also hydrogen needs lower ignition energy. Therefore the safety of hydrogen is important for an increase use in industries such as the automobile transportation industry.
Hydrogen has low-energy content per unit volume and it should be stored in high pressure tanks.Computational Fluid Dynamics (CFD) is used to simulate the hydrogen release through a sonic jet. The objective of this work is to understand the physics regarding the sudden release of hydrogen from a high pressure reservoir and to analyze the jet of hydrogen near the exit of reservoir. Due to the high pressure ratio of reservoir to environment (more than 400), shock occurs in the near field of sonic jet. In this situation the flame front moves at a supersonic speed and a strong shockwave happens. Explosion regarding development of a shock wave is called detonation which is the most dangerous type of explosion.
In order to accurately simulate the near jet flow, the numerical code has to include the real gas model. All Jacobian matrices and flux calculating methods are modified for real gas simulation. Euler equations are applied, and an implicit first-order in time and second order in space scheme is used. The mesh used is a 3D tetrahedral grid and is generated with GAMBIT. The computational domain is a cylinder.
Since the area of release is very fine relative to the whole domain, the elements near the jet exit are much smaller than the elements near the far field. This situation increases the total number of elements which increases the memory. Parallel processing is used to overcome the memory requirements. Also the small size elements decrease the time steps and the convergence time becomes very large. Parallel code allows decreasing the total computational time.METIS software is used for grid partitioning needed for parallel processing.
In this paper the ideal gas model is given and compared with the resultsof “M. Radulescu and C. Law, The transient start of supersonic jets, accepted for publication in journal of fluid mechanic”.In order to accurately find out the characteristics of the jet,a real gas model is investigated. Thedeveloped real gas model is presented and compared with ideal gas results. This real gas model can accurately predict the near field of the sonic jet.