Alternative method for bulk modulus estimation of Diesel fuels

• An alternative method for the estimation of fuel bulk modulus has been developed.
• Time lags between energizing and injection rate of injectors do not depend on fuel type.
• Initial time lag between energizing and injection rate depends only on the injector type.
• Rear time lag depends on both injector type and injection pressure in piezoelectric injectors.

The knowledge of Diesel fuel properties has great relevance for the analysis and comprehension of phenomena related to fuel injection, fuel–air mixture formation and diesel combustion processes. This work proposes an alternative method for estimating the bulk modulus of diesel fuels by means of an experimental installation commonly used for determining fuel injection rates from common rail injection systems. Three fuels were tested in the mentioned installation: commercial Diesel fuel (blended with 5.8% of biodiesel), hydro-treated vegetal oil (HVO) and gas to liquid (GTL) fuel from natural gas by means of low temperature Fischer Tropsch process. Results were obtained by testing two different injectors (solenoid operated and piezoelectric injectors) under different injection pressures and energizing times. Fuel temperature at inlet of the high pressure injection pump was controlled, keeping constant the pressure inside the fuel injection indicator. From the experimental work, data analysis and post-processing, bulk modulus of fuels tested has been estimated and compared to results obtained by diverse authors with different experimental installations and methods. Results obtained in this work show small differences compared to published data. Additionally, the initial time lag between the signal of the electric pulse when the injector is energized and the beginning of the injection rate profile depends only on the type of injector without influence of type of fuel and operating conditions. However, the rear time lag between both mentioned profiles depends only on injector type (when the solenoid operated injector was tested) while, with piezoelectric injector, it also depends on both energizing time of the injector and injection pressure.