Wednesday, September 23, 1998

(Dr. Scott Bair, advisor)

"The Measurement of Diesel Fuel Properties"

__Abstract__

Cummins Engine, a diesel engine manufacturer, has supported the measurement of thermodynamic properties for seven diesel fuels between temperatures of 00 and 1000 C and pressures between atmospheric and 350 MPa. The properties are required to perform flow analysis within a fuel system. Data was also generated for fluids with well-accepted published data and the results compared. The techniques used were also applied to several liquid lubricants.

Refractive index was found from Snell's law using a high-pressure refractometer and related to density using the Lorenz-Lorentz relationship. Density was also measured by direct measurement of volume. A falling body viscometer was used to determine viscosity and the Doolittle Free Volume equation was used to make a third estimate of density from these viscosity data. Acoustic "time of flight" measurements gave the speed of sound and with density provided the adiabatic bulk modulus. The Tait equation was fitted to the density data and differentiated with respect to pressure to determine the isothermal bulk modulus. The ratio of adiabatic to isothermal bulk moduli was then taken to determine the ratio of specific heats. An estimate of the phase transition pressure was also determined for each fluid at a given temperature by detection of a yield stress.

Viscosity and density were found to behave normally, each increasing with pressure and decreasing with temperature. Density measurements from direct volume measurement provided the smoothest curves with the closest agreement to well accepted published data. The ratios of specific heats were above one and approached one as pressure was increased. This is also expected, as a fluid becomes less compressible as it is compacted and incompressible fluids have a ratio of specific heats equal to one. This is due to a relatively low accuracy of the speed of sound measurements.