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Cyclic variability in internal combustion engines (ICEs) arises from multiple concurrent sources, many of which remain to be fully understood and controlled. This variability can, in turn, affect the behavior of the engine resulting in undesirable deviations from the expected operating conditions and performance. Shot-to-shot variation during the fuel injection process is strongly suspected of being a source of cyclic variability. This study focuses on the shot-to-shot variability of injector needle motion and its influence on the internal nozzle flow behavior using diesel fuel. High-speed x-ray imaging techniques have been used to extract high-resolution injector geometry images of the sac, orifices, and needle tip that allowed the true dynamics of the needle motion to emerge. These measurements showed high repeatability in the needle lift profile across multiple injection events, while the needle radial displacement was characterized by a much higher degree of randomness.

Fuel efficiency and emission performance sensitivity to fuel reactivity was examined using Delphi’s second-generation Gasoline Direct-Injection Compression Ignition (Gen 2.0 GDCI) multi-cylinder engine. The study was designed to compare a US market gasoline (RON 92 E10) to a higher reactivity gasoline (RON 80) at four operating conditions ranging from light load of 800 rpm / 2.0 bar gross indicated-mean-effective pressure (IMEPg) to medium load of 2000 rpm / 10.0 bar IMEPg. The experimental assessment indicated that both gasolines could achieve good performance and Tier 3 emission targets at each of the four operating conditions. Relative to the RON 92 E10 gasoline, better fuel consumption and engine-out emissions performance was achieved when using RON 80 gasoline; consistent with our previously reported single-cylinder engine research [1].

The effect of wall temperature on single-surface flame quenching distance was characterized for atmospheric, premixed methane-air flames. The study includes a comparison of the wall temperature dependent, single-surface flame quenching distance for laminar and turbulent flames. The laminar flame-Wall interaction was studied for flames that were configured at angles near 0° and 45° relative to a temperature-controlled surface. For each flame quenching configuration, the flame quenching distance was chosen as the location from the surface for which a constant value of C2 concentration occurred; spatially resolved measurements of C2 concentration were obtained with the technique of laser-induced fluorescence. The results indicated that the single-surface flame quenching distance, for each flame configuration, decreased with increasing wall temperature.

The effect of wall temperature on single surface flame quenching and flame structure of an atmospheric premixed methane-air flame was studied. The luminous region of a laminar flame was located at an angle of 45 degrees to a temperature- controlled surface. C2 laser-induced fluorescence was used as an indicator of flame position while Raman spectroscopy was used to determine gas temperature profiles near the surface. These measurements were conducted for wall positions (vertical distance from the surface) ranging from 50 mm to 1.0 mm and wall temperatures ranging from 150 °C to 600 °C. C2 laser-induced fluorescence measurements indicated flame position is affected by the presence of a surface and the surface temperature. Larger C2 fluorescence intensity values were observed for higher wall temperatures at all distances from the surface.