Investigation of the Rheology and Tribology Properties of Mono-Oleate
as an Additive
for SAE J1488-10 Emulsified Fuel-Water
Test Method, 08-R8389
Dr. Andrew Clark
Dr. Peter Lee
Inclusive Dates: 04/01/13 – 04/01/14
Background — Diesel fuel-water separation is a major process for protecting the fuel system and engine components in any vehicle or machine. The water separation process becomes increasingly more difficult with the addition of alternative fuels (biodiesel) and other various additives. Multiple joint industry programs (JIP) and internal research projects have been performed addressing these issues over the past few decades; however, none has investigated the rheology and tribology properties and the resulting fuel water separation characteristics. The objective of this project was to investigate these properties as well as new gas chromatography techniques to better understand fuel water separation, particularly with biodiesel fuels, and how SwRI can assist the industry with improving and standardizing the testing process.
Approach — The technical approach for this project was to use mono-oleates to provide a "standard" compound to simulate biodiesel fuels. Both new technologies and instrumentation were used for evaluating "stable" emulsions in an attempt to add some science to the understanding of fuel water emulsions. Since variability of the mono-oleate is the major issue, mono-oleates from many manufacturers and suppliers were obtained to determine the variability of the products both at a compositional and performance application. Some of the proposed analytical tools/instrumentations to be used for this project include environmental electron microscope (ESEM), GCxGC/MS, water droplet characterization, strain-controlled rheometer, tensiometer, water separation test stand and a laser diffraction particle sizer.
Accomplishments — The GCxGC/MS analysis determined that the selected mono-oleates, at least compositionally, are different; see Figure 1. Although claims that mono-oleates are 50 to 98 percent purity, this analysis illustrates many foreign materials of various quantities that are not in all the samples. The rheology and tribology results did generate some interesting data, but due to the nature of the emulsion, e.g., low viscosity, there was difficulty making the measurements. The cone and bob device was able to differentiate between the mono-oleates, and shows potential for better understanding water separation characteristics. The laser diffraction instrument provided significant data, demonstrating the water droplet distributions generated by each mono-oleate; see Figure 2. The water droplet distributions provided important data to allow us to better understand the impact of different biodiesel fuels and why fuel water separators do not perform as well with biodiesel as compared with just diesel fuel. The data generated from this project has resulted in a joint industry program, and improvements in the industry water separation test method.