Experimental and Numerical Analyses of Liquid and Spray Penetration under Heavy-Duty Diesel Engine Conditions

Abstract

The modeling of fuel sprays under well-characterized conditions relevant for heavy-duty Diesel engine applications, allows for detailed analyses of individual phenomena aimed at improving emission formation and fuel consumption. However, the complexity of a reacting fuel spray under heavy-duty conditions currently prohibits direct simulation. Using a systematic approach, we extrapolate available spray models to the desired conditions without inclusion of chemical reactions. For validation, experimental techniques are utilized to characterize inert sprays of n-dodecane in a high-pressure, high-temperature (900 K) constant volume vessel with full optical access. The liquid fuel spray is studied using high-speed diffused back-illumination for conditions with different densities (22.8 and 40 kg/m 3 ) and injection pressures (150, 80 and 160 MPa), using a 0.205-mm orifice diameter nozzle. High-speed Schlieren imaging is used to analyze the influence of these boundary conditions on the spray penetration. Simulations of the fuel spray are performed using a dedicated computational mesh with refinements at the known location of the jet to capture the smallest scales of interest. Using a blob injection model refined with a primary atomization and secondary breakup model, correct trends and good agreement are achieved for both liquid and spray penetration. The capability of capturing the trends at largely varying boundary conditions with a single computational approach provides a solid base for future work.

Transient Flame Development in a Constant-Volume Vessel Using a Split-Scheme Injection Strategy

“…Experiments were conducted in an optically-accessible, highpressure, high-temperature, constant-volume vessel, capable of reaching ambient conditions characteristic for current generations of compression-ignition engines [27,28]. The ambient environment in the current study targets the Spray A condition of the Engine Combustion Network (ECN), with a local gas temperature of 900 K, oxygen concentration of 15 vol%, and a density of 22.8 kg/m 3 [26].…”

A comprehensive methodology for computational fluid dynamics combustion modeling of industrial diesel engines

“…High-speed liquid-and vapor-phase fuel penetration were measured for non-reacting experiments using DBI and Schlieren, respectively. Further details about the employed optical techniques can be found here [20,27]. The experimental results reported in this work were constructed using ensemble averages of at least 10 individual recordings.…”

“…To better predict the fuel-air mixing process, local refinement was used in the region where the spray evolves, where mesh size ranges from 0.3 to 1 mm. The spray model presented in this work was extensively validated in [20], where a suitable methodology for a consistent comparison between computed and DBI experimental data of liquid penetration was also developed. In particular, a light scattering model was implemented by the authors following the recent methods suggested by Magnotti and co-authors [21].…”

“…For further details related to the computation of the liquid penetration value and its comparison with experimental data, the reader is referred to [20], where the effects of spray model constants on computed extinction profiles are presented in detail.…”

“…Different cylinder heads and injectors were used: with the O-Bowl, the engine runs with a 0.5 swirl ratio and a 9-hole nozzle while H-Bowl was tested with a 8-hole nozzle and higher swirl (1.3). The compression ratio from the H-Bowl is 20.5 which is slightly higher than the one of the O-Bowl (20): for this reason, SOI time was adjusted in order to achieve the same break mean effective pressure (bmep) for any load with the two bowl configurations. Same NO x levels were experimentally achieved from the A75 and Cruise load points, respectively.…”