High pressure jet

[2] Intentional or accidental release may occur in an industrial settings like natural gas processing plants, oil refineries and hydrogen storage facilities.

[2] A main focus during a risk assessment process is the estimation of the gas cloud extension and dissipation, important parameters that allow to evaluate and establish safety limits that must be respected in order to minimize the possible damage after a high pressure release.

This will lead to the a newly defined expression for the aforementioned pressure ratio and, sub-sequentially, the flow rate equation.

When under-expanded, the jet will have characteristics of a compressible flow, a condition in which pressure variations are significant enough to have a strong effect on the velocity (where it can exceed the speed of sound of the gas), density and temperature.

If we consider the fire triangle model, to induce a combustion reaction three components are needed: a fuel, an oxidizing agent and heat.

Considering a free jet at sub-critical pressure (beyond the nearfield zone), its mean volume fraction axial concentration decay of any gas released in air can be defined as follows:[14] Experimental data of high pressure jets have to be limited in terms of size and complexity of the scenario due to the inherit dangers and expenses correlated to the experiment itself.

Alternative methods to gather data, such as representative models, can be used in order to predict what the maximum extend of the gas cloud at its LFL concentration can reach.

Convergence problems can arise within the simulation as large momentum, mass and energy gradients appear in the volume.

As a consequence, a simpler CFD model can be simulated by using the following diameter (named pseudo-diameter) as the new exit plane:[19] In the process industry, there exist a variety of cases where a high pressure jet release incident can occur.

LNG storage facilities or NG pipeline systems leakage[20] can degenerate into a jet fire and, through a domino effect, cause heavy damage to the workforce, equipment and surrounding environment.

Contour animation of the mole fraction variation (from 0.025 to 0.05) of a Natural Gas jet as it impinges a steel tank done through CFD .
The flow rate of an ideal gas can be represented by the graphed line. As the pressure ratio decreases and the critical value is approached, the flow changes from non-choked to choked, setting an upper limit to the velocity of the gas to the speed of sound of the medium.
The subdivision of a high pressure jet as it expands to the pressure of the surrounding conditions.
A CFD simulation of a natural gas extremely under-expanded jet. Sections where the Mach Number is much higher than 1 are points in which the velocity of the fluid is much higher than the speed of sound, an effect that manifest due to the sudden depressurization of the gas. P ∞ is ambient pressure of 101325 Pa
Jet-tank-ground interaction will have an effect on the maximum extension of the cloud at LFL concentrations. Eddies generated after their interactions will promote gas dissipation. s represents the distance between the center of the two tanks, D is the diameter of the tanks