Speed of Sound Measurements of n -Dodecane, 2,2,4,4,6,8,8-Heptamethylnonane, and Toluene

Abstract

Abstract Speed of sound data measured using a dual-path pulse-echo instrument are reported for n-dodecane, 2,2,4,4,6,8,8-heptamethylnonane (isocetane), and toluene. These data are reported at temperatures ranging from 230 to 420 K and at pressures up to 49.7 MPa. The combined expanded uncertainty in the speed of sound varies from 0.032 to 0.048% of the measured speed of sound value, which is both fluid- and state-point-dependent. The data for n-dodecane and toluene are compared with the present reference equations of state (EOSs) included in REFPROP version 10.0. These comparisons show that the data reported in this study agree with both of the reference EOSs within their stated uncertainties. No reference EOS is available for isocetane. Therefore, a preliminary EOS was obtained by using the fitting tools available in ThermoData Engine. The preliminary EOS for isocetane provides comparable performance to those of toluene and n-dodecane in reproducing the speed of sound values. Comparisons to these EOSs will be used to inform the development of a surrogate mixture model for alternative aviation fuels.