Christophe T’Joen

Bio: Christophe T’Joen is an academic researcher from Royal Dutch Shell. The author has contributed to research in topics: Jet (fluid) & Real gas. The author has an hindex of 2, co-authored 4 publications receiving 20 citations.

Investigation of a highly underexpanded jet with real gas effects confined in a channel: flow field measurements

Abstract: This article describes experiments to investigate the fluid-to-wall interaction downstream of a highly underexpanded jet, with a pressure ratio of 120, confined in a channel. Heat transfer induced by Joule-Thomson cooling, which is a real gas effect in such a configuration, has critical implications on the safety of pressurised gas components. This phenomenon is challenging to model numerically due to the requirement to implement a real gas equation of state, the large range of (subsonic and supersonic) velocities, the high turbulence levels and the near-wall behaviour. An experimental setup with simple geometry and boundary conditions, and with a wide optical access was designed and implemented. It consisted of a high-pressure gas reservoir at controlled temperature and pressure, discharging argon through a nozzle into a square channel. This facility was designed to allow for a steady-state expansion from over 120 bar to atmospheric pressure for over 1 min. The choice of fluid, pressure and temperature regulation system, and the implementation of a high pressure particle seeding system are discussed. The gas dynamics of this flow was then investigated by two separate optical techniques. Schlieren measurements were used to locate the position of the Mach disk, and planar particle image velocimetry (PIV) was used to measure the turbulent velocity field in the regions of lower velocity downstream. Mie scattering images also indicated the presence of a condensed argon phase in the supersonic region as expected from previous studies on nucleation. The observed location of the sharp interface at the Mach disk was found to be in excellent agreement with the Crist correlation. Rapid statistics were derived from the PIV measurements at 3 kHz. The recirculation zone was found to extend about 4 channel heights downstream, and in the region between 2 and 3 channel heights downstream, a continuous deceleration on the centerline velocity was observed in line with the narrowing of the recirculation zone. The first and second velocity moments as well as Reynold stresses were quantified, including pdf distributions. In addition, a sensitivity and repeatability analysis, an evaluation of the PIV random uncertainty, as well as an estimation of errors induced by particle inertia were performed to allow for a full quantitative comparison with numerical simulations.

Numerical Investigation and Experimental Comparison of the Gas Dynamics in a Highly Underexpanded Confined Real Gas Jet

Abstract: A numerical study for a supersonic underexpanded argon gas jet driven by a pressure ratio of 120 is described in this work, and the results are compared to experiments. A single phase large-eddy simulation (LES) employing a fully-coupled pressure-based finite volume solver framework is carried out. The numerical results are validated against experimental Schlieren and particle-image-velocimetry (PIV) measurements taken under the same conditions. Due to the high pressure conditions imposed on the gas, real gas effects are taken into account via the Peng-Robinson equation of state. This approach enables the accurate prediction of the gas properties throughout all pressure conditions encountered within this study. Flow velocity data obtained from numerical simulations and experiments are presented, leading to valuable insights into the features of the flow. Comparisons between experimental and numerical Schlieren images show a very good agreement for the location and shape of the main shock structure in the near nozzle exit region. The predicted velocity field further downstream, at a stream-wise distance over 100 nozzle diameters from the nozzle exit, is reasonably close to the PIV data, with less than 25% difference between the root-mean-square (RMS) simulated and experimental velocity field. The agreement obtained in this study is remarkable in light of the challenging flow configuration involving a vast range of flow speeds and time scales. There are also discrepancies, predominantly for the near-throat velocity profiles obtained from PIV measurements and numerical simulations: in the immediate post-shock region the simulation results predict a major converging throat of low, subsonic fluid velocity surrounded by the supersonic shear layer, which is not observed in the experiment.

Particle Image Velocimetry

Abstract: conferencia sobre "Particle Image Velocimetry" de les 13:00-14:00 a la Sala de Juntes de l'FNB impartida pel professor Peter Bueken da l'Antwerp Maritime Acedemy (Belgica)

Fluid injection with supercritical reservoir conditions: Overview on morphology and mixing

Abstract: The present work provides an overview on the possible phase transitions associated with supercritical fluid injection and a detailed evaluation of the mixing process between injectant fluid and quiescent ambience. The experiments cover superheated liquid disintegration, pseudo-boiling transition and single-phase jets under different nozzle pressure ratios. Pseudo-boiling effects emerge when rapid, subsequent changes in pressure/temperature interact with the non-linear behavior of thermodynamic response functions across the Widom line. The associated density fluctuations cause a significant increase in the scattering cross section and may lead to thermo-convective instabilities. Our analysis of the mixing process demonstrates the limited applicability of the adiabatic mixing model, which is often restricted to short residence times even in highly turbulent jets ( Re = O ( 10 5 ) ). Specifically, our findings show the importance of considering all coupled transport processes in the analysis of mixing problems at high pressures, in particular in presence of large mass concentration and temperature gradients.

Investigation of a highly underexpanded jet with real gas effects confined in a channel: flow field measurements

Abstract: This article describes experiments to investigate the fluid-to-wall interaction downstream of a highly underexpanded jet, with a pressure ratio of 120, confined in a channel. Heat transfer induced by Joule-Thomson cooling, which is a real gas effect in such a configuration, has critical implications on the safety of pressurised gas components. This phenomenon is challenging to model numerically due to the requirement to implement a real gas equation of state, the large range of (subsonic and supersonic) velocities, the high turbulence levels and the near-wall behaviour. An experimental setup with simple geometry and boundary conditions, and with a wide optical access was designed and implemented. It consisted of a high-pressure gas reservoir at controlled temperature and pressure, discharging argon through a nozzle into a square channel. This facility was designed to allow for a steady-state expansion from over 120 bar to atmospheric pressure for over 1 min. The choice of fluid, pressure and temperature regulation system, and the implementation of a high pressure particle seeding system are discussed. The gas dynamics of this flow was then investigated by two separate optical techniques. Schlieren measurements were used to locate the position of the Mach disk, and planar particle image velocimetry (PIV) was used to measure the turbulent velocity field in the regions of lower velocity downstream. Mie scattering images also indicated the presence of a condensed argon phase in the supersonic region as expected from previous studies on nucleation. The observed location of the sharp interface at the Mach disk was found to be in excellent agreement with the Crist correlation. Rapid statistics were derived from the PIV measurements at 3 kHz. The recirculation zone was found to extend about 4 channel heights downstream, and in the region between 2 and 3 channel heights downstream, a continuous deceleration on the centerline velocity was observed in line with the narrowing of the recirculation zone. The first and second velocity moments as well as Reynold stresses were quantified, including pdf distributions. In addition, a sensitivity and repeatability analysis, an evaluation of the PIV random uncertainty, as well as an estimation of errors induced by particle inertia were performed to allow for a full quantitative comparison with numerical simulations.

Flow field characteristics of a confined, underexpanded transient round jet

Abstract: The flow field of an impulsively started round, confined nitrogen jet was investigated using combined high speed schlieren imaging and particle velocimetry (PIV) measurements. PIV measurements were carried out at five different, normalized times (55 ≤t*≤ 392) relative to jet intrusion into a constant volume chamber. Between 100