Experimental Hemodynamics within the Penn State Fontan Circulatory Assist Device

For children born with a single functional ventricle, the Fontan operation bypasses the right ventricle by forming a four-way total cavopulmonary connection adapting the existing ventricle for the systemic circulation. However, upon adulthood, many Fontan patients exhibit low cardiac output and elevated venous pressure, eventually requiring a heart transplantation. Despite efforts to develop a Fontan pump or use an existing ventricular assist device for failing Fontan support, there is still no device designed or tested for subpulmonary support. Penn State University is developing a hydrodynamically levitated Fontan circulatory assist device (FCAD) for bridge-to-transplant or destination therapy. The FCAD hemodynamics, at both steady and pulsatile conditions for three pump operating conditions, were quantified using particle image velocimetry to determine the velocity magnitudes and Reynolds normal and shear stresses. Data were acquired at three planes (0 mm and ±25% of the radius) for the inferior and superior vena cavae inlets and the pulmonary artery outlet. The inlets had a blunt velocity profile that became skewed towards the collecting volute as fluid approached the rotor. At the outlet, regardless of the flow condition, a high-velocity jet exited the volute and moved downstream in a helical pattern. Turbulent stresses observed at the volute exit were influenced by the rotor's rotation. Regardless of inlet conditions, the pump demonstrated advantageous behavior for clinical use with a predictable flow field and a low risk of platelet adhesion and hemolysis based on calculated wall shear rates and turbulent stresses, respectively.

Numerical Investigation on the Cavity Implementation Methods in Trapped Vortex Combustor

Well-stabilized vortices inside a physical cavity using direct injection of reactants can be used to provide stable combustion with performance benefits. The adaptation of the Trapped Vortex Combustion (TVC) concept involves the placement of the cavity-based flame stabilization device in the main duct of the combustor using annular or planar geometric configurations. In this work, we compare the performance of inner annular, outer annular and planar arrangements of the cavity with dual-vortex structure configuration enabled by a single injection port on the upstream wall of the cavity. The comparison is done using Reynolds Averaged Navier-Stokes (RANS) simulations. The effect of cavity implementation methods on the flame stabilization, temperature distribution at the exit of the combustor and pollutant emissions are analyzed with three combustor operating conditions based on the flow parameters. Significant differences in the flame stabilization are observed in the combustors due to the dissimilarity of the velocity and fuel distribution. The parameter, jet momentum flux ratio, denoted by J, is defined based on the inlet conditions and the estimate of actual cavity flow velocity from numerical results. This parameter is used to correlate the combustor performance among the various configurations studied. The inner annular combustor can be scaled to higher power by increasing the combustor radius (R) with same cavity size, flow parameters and chemical parameters, however, the flame stabilization and performance are affected by the geometric parameters, combustor radius (R) and cavity depth (D). Strategies to scale-up the combustor to obtain the required performance are discussed along with the challenges faced in comparing results of the various configurations studied.

CONTINUOUS-FLOW EXTRACTION OF BIOCOMPOUNDS IN FIXED BED: INFLUENCE OF SWAPPING FROM DIRICHLET TO DANCKWERTS CONDITION AT INLET IN PHENOMENOLOGICAL MODELS

Phenomenological models have increasingly become vital to bioprocess engineering. In continuous-flow biocompounds extraction models, diffusion requires an extra boundary condition at exit (usually null Neumann condition) while either Dirichlet or Danckwerts condition can be imposed at inlet. By taking an extant case study and with the help of an in-house lattice-Boltzmann simulator, this work numerically examines prospective effects of interchanging aforesaid inlet conditions. Trial simulations were performed for scenarios ranging from convective-dominant to diffusive-dominant. Extraction yields numerically simulated under each inlet condition were compared with experimental data. Expected shape of extraction yield curves was simulated whenever process parameters were properly provided and differences due to switching inlet conditions became evident only in diffusion-dominant extraction scenarios. At diffusivities of order 10-6 m2 s-1, numerical results suggest that Danckwerts boundary condition should be preferred at bed inlet.

Superposition Effect of the Leading Edge Film On the Downstream Film Cooling of a Turbine Vane Under Combustor Swirling Outflow

To investigate the superposition effect of the leading edge film on the downstream film cooling under swirling inflow, numerical simulations with three vane models (vane with films on the leading edge only, vane with films on the pressure side and suction side only, full-film cooling vane), two inlet conditions (axial inlet and swirling inlet) are conducted. The results indicate that the leading edge is the area where the film is most affected by the swirling inflow. For full-film cooling vane, the film on the leading edge does not always improve or even reduce the downstream film cooling. Flow mechanism analysis shows that the velocity direction near the downstream wall is governed by the interaction between the direction of swirling inflow and the direction of film hole incidence on the leading edge. A new type of leading edge film proposed by the author is also investigated, with the dividing line of the counter-inclined film-hole row coinciding with the twisted stagnant line to ensure that all films are incident at angles inverse to the direction of the swirling inflow. The new leading edge film successfully changes the velocity direction near the downstream wall and suppresses the deflecting effect on the downstream film. The new leading edge film can increase the overall area averaged cooling effectiveness of the full-film cooling vane by 10%, 15%, 18% and reduce the inhomogeneity by 13%, 19%, 27% over the traditional design, as the coolant mass flow increases.

Experimental Data of Supercritical Carbon Dioxide (sCO2) Compressor At Various Fluid States

This paper presents experimental data on a centrifugal compressor operated with CO2. Temperature and pressure at the inlet of the compressor are varied to cover the supercritical region from the liquid-like to the gas-like region. In addition, inlet conditions in the two-phase region are also included. Thus, the experimental test campaign considers thermodynamic conditions relevant for the future energy conversion with sCO2-Joule cycles. Experimental results are presented as compressor pressure ratio vs inlet mass flow rate at different rotational speeds and throttle positions. Reliable conclusions can be drawn from the experimental results since the reproducibility of the measurements has been demonstrated by conducting experiments in two different test rigs, and measurement uncertainties are reported. The entire compressor geometry is disclosed in a data repository, including CAD models, and input files suitable for mean-line and grid generation programs. Thus, the experimental results are exploitable by the scientific community and pave the road for validated analysis and design tools in the context of the sCO2-Joule cycle. The presented results open the possibility to estimate uncertainties of analysis and design tools with little effort since geometry information can be quickly integrated. The experimental data is already used in this paper to obtain the accuracy of a CFD code and a mean-line program for sCO2. In addition to quantifying uncertainties, the results presented can be used to identify shortcomings of existing tools. This can be an essential step in the exploration of the sCO2-Joule cycle.