Bulk Modulus of Compressibility Measurements of Conventional and Alternative Military Fuels

Principal Investigator: André Boehman, University of Michigan, boehman@umich.edu
Student: Taemin Kim, University of Michigan
Government: Eric Sattler, U.S. Army TARDEC
Industry: Peter Attema, Daimler Trucks North America

Diesel fuel injection systems that rely on the application of hydraulic pressure to the fuel to open a needle that allows fuel to be injected into the engine can be sensitive to the hydraulic properties of the fuel being injected. Two properties of relevance are viscosity and compressibility, which is typically measured and reported in term of the bulk modulus of compressibility. Variations in the bulk modulus of compressibility away from values typical of diesel fuels (or conventional hydrocarbon fuels) can significantly influence the injection timing and combustion behavior of diesel engines when operating on such fuels, leading to changes in engine emissions, and potentially to changes in performance, fuel economy and driveability.

The research objectives of the proposed project are to provide measurements of the compressibility of conventional and alternative diesel and jet fuels of interest to the U.S Army and to serve as an additional, experienced partner with whom to compare compressibility measurements of conventional and alternative military fuels.

In addition, comparisons will be made between JP-8 surrogate fuels being developed by Automotive Research Center researchers (projects 4.6, 4.17, 4.19) and the practical fuels that the surrogates are intended to represent, to ascertain how well the surrogate fuels represent the compressibility of JP-8. While the bulk modulus of compressibility of the surrogate is not one of the properties the surrogate is intended to match, this comparison between JP-8 fuels and the JP-8 surrogate will provide information that can help to anticipate injection timing shifts in subsequent engine testing of the surrogate, if an engine with a pump-line-nozzle injection system is used for such comparisons.