MSc project: Simulation of Supersonic Under-Expanded Gas Jet

Project description

The transport of natural gas is vitally important for our ever increasing energy needs. To efficiently transport natural gas, long pipes with choke valves are required. The velocity of the natural gas through these choke valves can be supersonic, and the resulting pressure drop can reach several hundred bars [1]. The flows from these valves are referred to as under-expanded supersonic jets. Due to the Joule-Thomson cooling of the expanding gas, very low temperatures (typically up to -80 oC or so) can be found downstream of the valve.

The aim of this project is to perform a numerical study on the structure of highly under-expanded supersonic jets. These jets are formed when gas is discharged from a nozzle fed by a reservoir of such a high pressure, that the gas pressure at nozzle exit is still larger than the ambient pressure. In those cases, it is necessary to take real gas effects into account due to the presence of extremely large pressure differences.

For the successful completion of this project, a multi-step approach involving the tasks outlined below will be proposed.

Firstly, a literature review on supersonic flows and jets [2] is recommended to gain the necessary theoretical background. The next step is to apply commercial CFD tools (e.g. FLUENT) to carry out a preliminary numerical study on a two-dimensional geometry. After identifying and generating the optimal nozzle discharge geometry, inviscid ideal gas simulations parametrized by the increasing ratio between reservoir and ambient pressure will be performed, leading to a characterization of the jet structure for each case. The final step is to perform three dimensional simulations for both ideal gas and real gas. The effect of nozzle geometry, different equations of state as well as Reynolds number will be investigated. The simulation results are to be validated by using in-house simulation tools and by comparison with available experimental and reference numerical results in literature [3,4].

It is the intention that this work will be carried out by a Master student from TU Delft while being located in the team of prof. van Wachem at the Mechanical Engineering Department of Imperial College in London.

Contact

For more information of the project please contact: R.A.W.M.Henkes@tudelft.nl.

People involved

Prof. dr. ir. R.A.W.M. Henkes (Delft University of Technology)

Prof. dr. ir. B. van Wachem (Imperial College London)

References

1. Abdi, M.A. , Jassim, E., Haghighi, M., Muzychka, Y., Applications of CFD in Natural Gas Processing and Transportation, Computational Fluid Dynamics: Chapter 1, InTech, 2010.

2. Shapiro, A.H., The Dynamics and Thermodynamics of Compressible Fluid Flow, The Ronald Press Company, 1954.

3. Crist, S., Sherman, P.M., Glass, D.R., Study of the Highly Underexpanded Sonic Jet, AIAA Journal, Vol.4 No,1, 68-71, 1966. 4. Vuorinen, V., Yu, J., Tirunagari, S., Kaarlo, O., Larmi, M., Duwig, C., Boersma, B.J., Large-eddy simulation of highly underexpanded transient gas jets, Physics of Fluids, 25, 2013.

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