Development and verification of an in-flow water condensation model for 3D-CFD simulations of humid air streams mixing

Abstract

Bulk flow condensation caused by the mixing of air streams at different temperatures and humidities is a thermodynamic process that requires strong assumptions to be calculated with low computational effort. The applicability of a model that correctly predicts this phenomenon has grown recently due in part to the deployment of the Long Route Exhaust Gas Recirculation emission reduction technique in combustion engines and the damage to the turbocharger caused by the condensation produced when the intake air is mixed with the combustion gases. This work is addressed to expose a condensation model that is implemented in a commercial 3D-CFD code and is then verified, checking whether the implemented physical equations are behaving as intended. Finally, a practical application is made, showing the potential of model to predict water condensation in a LR-EGR T-joint.

Centrifugal compressor influence on condensation due to Long Route-Exhaust Gas Recirculation mixing

“…Condensation modeling is a key feature for the current analysis. The model selected was developed and verified by Serrano et al [6] and then validated by Tarí [17] through an experimental campaign of durability tests. For a proper understanding of the phenomena that takes place in the LR-EGR joint, a brief description of this physic process and the approach of the condensation model is provided.…”

“…This may occur in the EGR cooler or in the T-joint upstream the compressor, when the exhaust gases are reintroduced to the intake duct and are mixed with fresh (and potentially cold) air. Condensation in the cooler is usually found during the warming up whereas condensation in the T-joint is strongly noticeable with ambient temperatures below 10 • C [6]. Appearance of liquid water upstream the compressor is critical if droplets reach the impeller.…”

Development of an experimental test bench and a psychrometric model for assessing condensation on a low-pressure exhaust gas recirculation cooler

“…[23][24][25] In addition, it can be found in the mixing region between fresh air and EGR gas, due to its high water content. 26,27 Water droplets can produce an important damage to the compressor impeller, severely reducing its durability. In other research fields, such as steam jets 28,29 or nozzles, 30 water condensation is also a problem.…”

Cylinder-to-cylinder high-pressure exhaust gas recirculation dispersion effect on opacity and NOx emissions in a diesel automotive engine

“…24 In addition, HP configuration needs less exhaust energy because the compressor operates under lower amount of gas. Moreover, the LP EGR presents troubles related to condensation issues at low ambient temperatures when it mixes with ambient air; this effect was recently studied by JR Serrano et al 25 and J Galindo et al 26 to predict the condensation rate and its effect in the rotor of the compressor, respectively. Nevertheless, at low ambient temperature, condensation issues appear in the whole engine and in all its elements, in the HP EGR line for instance, like JM Luján et al 27…”