Evaluation of thermal boundary layer interaction in shock tube sampling for kinetic studies

摘要

In shock tube studies of reaction kinetics the gas to be analyzed is often leaked through a pin hole at the tube end wall into a mass spectrometer. Such samples may be influenced by the growing thermal boundary layer (Tbl) at the cold end wall. In order to assess the effect of this cooling on kinetic measurements, the temperature history of the gas sample reaching the analyzer must be known. This paper allows, based on independent orifice flow and Tblsolutions and their limited interaction, an evaluation of the extent of gas cooling. It shows that the simple flow hemispherendash;Tbloverlay greatly overestimates cooling, that Tblgrowth is retarded in the vicinity of the orifice, and that centerhyphen;core sampling with a skimmer is strongly favored. It provides the kineticist with the basic tools required to assess these effects and gives some illustrative kinetic examples.