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This work investigates the impact of injector temperature on the characteristics of high-pressure n-dodecane sprays under conditions relevant to heavy-duty diesel engines. Sprays are injected from a pair of single-hole diesel injectors belonging to the family of “Spray C” and “Spray D” Engine Combustion Network (ECN) injectors. Low and high injector temperature conditions are achieved by activating or deactivating a cooling jacket. We quantify spray spreading angle and penetration using high-speed shadowgraphy and long-distance microscopy imaging. We evaluate differences in fuel/air mixture formation at key timings through one-dimensional modeling. Injections from a cooled injector penetrate faster than those from a higher temperature injector, especially for an injector already prone to cavitation (Spray C).

In this paper we describe the experimental apparatus used to validate concepts associated with a bimodal internal combustion engine for use in natural gas vehicles (NGV's). In one mode, all engine cylinders fire normally providing locomotion for the NGV. In the other mode, one cylinder of the engine is used to compress residential natural gas, in multiple stages, to a standard US compressed natural gas (CNG) vehicle storage tank pressure of 250 bar. In the refueling mode, while the single cylinder is compressing natural gas it is powered by natural gas combustion in the remaining engine cylinders. Here we describe the engine dynamometer testing used to validate the bimodal engine design described in a companion paper. More specifically, a base compression ignition engine is powered by an AC motor while pumping air into storage tanks while all relevant thermodynamic parameters are recorded.