Injector Characterization: 2007 to Present

INJECTION EQUIPMENT– A Bosch, Generation 2 common rail fuel injector equipped with different single-hole axial nozzles has been used for diesel spray experiments at Sandia beginning in 2007. The specifications match the “Spray A” conditions, which is documented in detail. The nozzles all have convergent, hydroground orifices (KS1.5/86 specification by Bosch) and are mini-sac type with a sac volume of 0.2 mm³. Detailed nozzle geometry for single-hole, Spray A and three-hole, Spray B is available.

NOZZLE COEFFICIENTS– The discharge (C_d) and area contraction (C_a) coefficients for these orifices were measured with the injector installed in the Sandia vessel and injecting into atmospheric pressure. The orifice coefficients were determined from long-injection events, where the flow is relatively steady, as shown in Fig. 2.4.1 and Kastengren, 2012. The table below shows C_d values using the measured orifice diameter at the exit of the nozzle rather than the nominal specification [Kastengren, 2012].

Serial #	Min. Orifice Diameter [mm]	Fuel	Fuel injection pressure [MPa]	Fuel temperature [K]	Fuel density [kg/m3]	Cd	Cd uncert.	Ca	Ca uncert.
210370	0.0908	n-dodecane	150	343	713	0.89	0.01	0.98*	–
210675	0.0894	n-dodecane	150	343	713	0.90	0.01	0.98*	0.02
210677	0.0837	n-dodecane	150	343	713	0.89	0.01	0.98*	0.02
210678	0.0886	n-dodecane	150	343	713	0.89	0.01	0.98*	0.02
210679	0.0841	n-dodecane	150	343	713	0.91	0.01	0.98*	0.02

*Because of discovered shortcomings with force measurements at Sandia, C_a is estimated based on measurements performed at CMT for injector 210675. Once again, results are based on the measured nozzle diameter, not the nominal 0.090 mm diameter. (Also see “hydraulic characterization” of ECN1 proceedings.)