Numerical simulation of rapid expansion of supercritical carbon dioxide

Abstract

Axisymmetric rapid expansion of supercritical carbon dioxide is investigated in this article. The extended generalized Bender equation of state is used to give a good description of the fluids over a wide range of pressure and temperature conditions. The locations of Mach disks are analyzed and compared with an experimental correlation for the case where there is no plate positioned in front of the nozzle exit. It is found that the disagreement between our numerical results and the experimental formula is very small when the pressure ratio is small, and increases as the pressure ratio increases. It is also found that with different equations of state, the predicted positions of Mach disks do not differ a lot, but the temperature profiles in the chamber differ a lot. The case where there is a plate positioned in front of the nozzle exit is also studied in this article. A universal similarity solution is obtained.

Numerical simulation of particle formation in the rapid expansion of supercritical solution process

“…(1)-(8) and the moments Eqs. (64)-(67) is exactly the same as what was used in [33]: The characteristic-based splitting scheme plus artificial viscosity to capture the shocks, using a finite element numerical toolbox femLego [39]. At every time step, the fluid equations are solved first, and then the moment equations are solved.…”

“…More details can be found in [33]. The dimensionless parameters that appear here are: Reynolds number Re = L * v * /Á 0 , which measures the relative importance of inertia to viscous stresses, Á 0 comes from the assumption that the dynamic viscosity depends linearly on density = Á 0˜ [27];…”

“…He included gradient contributions in both the entropy and the internal energy, leading to a generalized pressure tensor term in the system of equations. We will use this model to calculate the flow field and thermodynamic variables, but instead of van der Waals equation of state, we use the egB equation of state, since previous studies [5,14,33] showed that the cubic equation of state is not suitable for supercritical expansion calculations.…”

The Flow Characteristics of Supercritical Carbon Dioxide (SC-CO2) Jet Fracturing in Limited Perforation Scenarios

“…For the SC-CO 2 jet fracturing, the flow field of SC-CO 2 jet is the essential key question that has attracted much attention from scholars. Firstly, the SC-CO 2 free jet has been studied by researchers, including the jetting structure and flow field [12][13][14]. The comparison and sensitivity analysis of SC-CO 2 jet in oil and gas fracturing is explored by using the computational fluid dynamics method [15].…”

“…The results show that the pressurization plays a more important role in jet fracturing with an increase in pressure difference, ambient pressure, nozzle diameter, and fluid temperature. However, the investigation of convection heat transfer of CO 2 in a vertical tube shows that a high Reynolds number affects the SC-CO 2 jet flow field in the perforation tunnel [14]. Many researchers have found that the turbulent mixing layer and discontinued jet properties is an essential factor for the pressurization.…”