Speed of sound measurement in ethyl tert-butyl ether and tert-amyl methyl ether by Brillouin light scattering

Ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) have been considered as the potential fuel additives as the replacement of methyl tert-butyl ether (MTBE). Now it is necessary to supplement and perfect the thermophysical properties of oxygenates, including acoustic property. In this paper, speed of sound in ETBE and TAME were measured by Brillouin light scattering from 293.15 K to 680 K and from saturated vapor pressure to 10 MPa, including saturated liquid/vapor, compressed liquid and supercritical region. It is estimated that u (T) = 0.01 K under saturated condition; u (T) = 0.02 K, u (p) = 0.015 MPa for p < 5.5 MPa, u (p) = 0.03 MPa for p > 5.5 MPa under compressed liquid and supercritical conditions; and the relative expended uncertainty in the speed of sound is estimated to be less than 0.5% with coverage factor of k to be 2. Moreover, the reference relations of the speed of sound for saturated liquid, vapor and compressed state are presented for interpolation with the average absolute deviation of 0.23%, 0.07% and 0.33% for ETBE and 0.34%, 0.24% and 0.29% for TAME, respectively.