The continuing tightening of emission regulations has encouraged extensive research into fuel spray vaporising and combustion. This thesis is an investigation into the effect that the cylinder boundaries have upon the quantity and composition of the unburnt hydrocarbons present in the exhaust gas and particulate matter. To determine the cylinder boundaries' effect on the exhaust hydrocarbon content a series of engine tests was completed. The engine used for these experiments was a modem four cylinder turbo charged direct injection diesel engine, operated at five steady state test points. The test consisted of two standard engine builds to determine the accuracy of measurement and to supply a base point for comparison. The second test used standard pistons with modified oil control rings to increase the oil film thickness. The final test used pistons with the top ring moved nearer the top of the piston by 5.5 mm to reduce the top land crevice volume by ?55%.The composition of the particulate soluble organic fraction (SOF) for the test using the low tangential load oil control piston ring was shown to have a greater fuel content than for other tests, showing that adsorption of the fuel in the lubricating oil contributes to the particulate. The reduction of the top ring crevice volume produced similar quantities of particulate SOF but it consisted of generally lighter hydrocarbon species. The effects of these changes were replicated in a mathematical model which calculated the in cylinder values for fuel, soot, temperature and hydrocarbons. The model also simulated the oxidation of hydrocarbons at the cylinder boundary and consisted of 3 primary zones; the combustion chamber, crevice volume and oil film. This research shows that careful design of engine components can influence the quantity and composition of the particulates exhaust gas and allow the reduction of regulated components.

The study of single-plume sprays into cross-flowing air is found extensively in literature, however, with the continued development of the Spark Ignition Direct Injection (SIDI) engine, the behaviour of multi-plume sprays in cross-flowing conditions is of interest. In the present work, the injection of a multi-plume spray into a high-velocity cross-flow is investigated; an experimental apparatus capable of providing a cross-flow with core velocities higher than 200 m/s is developed; analysis techniques are developed to characterize the cross-flow and multi-plume spray independently; the multi-plume spray is characterized as it issues into the cross-flowing air. The round air jet used for the cross-flow was designed using the concepts put forth for the design of wind tunnel contractions. The axial and radial velocities were measured using a Particle Image Velocimetry system from LaVision Inc. and the potential core length determined for the core velocities corresponding to Mach numbers of 0.35 and 0.58. It was determined that the potential core length increases with increasing Mach number and that increased compressibility, leads to reduced mixing within the core. Furthermore, velocity profiles of the air jet show that self-similarity is preserved within the shear layer of the initial region. The multi-plume spray was also characterized in quiescent conditions for 10 and 15 MPa injection pressures. It was found that the penetration depth and spray width increased with increasing injection pressure, but that the spray angle decreased with increasing pressure. The increase in penetration depth is consistent with the findings presented in literature, while the decrease in spray angle with increasing pressure is contrary to literature. Next, the multi-plume spray, injected at 10 and 15 MPa, is characterized as it issues into the cross-flowing air stream at Mach numbers equal to 0.35 and 0.58. The tail length and penetration are measured and it is found that for the first, the cross-flow velocity is the primary factor with higher cross-flow velocity resulting in a longer tail length, while for the latter, the injection pressure is the major factor, with higher injection pressures resulting in higher penetrations. That being said, the injection pressure does play a small role in the tail length, with the 15 MPa injection having a slightly longer tail length than the 10 MPa injection in the Mach number 0.58 cross-flow. This is attributed to the finer atomization, which is expected from the 15 MPa injection and which leads to quicker entrainment of fuel droplets into the cross-flow. The spray axis was predicted for each set of conditions from 0.1 ms to 1.0 ms after Start of Fuel (SOF). It was found that before 0.3 ms, the spray retains its multi-plume nature, while after 0.3 ms it behaves like a single-plume spray. Once the spray has crossed this transition point, the spray axis is temporally independent and can be predicted by the logarithmic models, similar to those used for single-plume sprays in cross-flow. The accuracy of this fit is improved upon, with the presentation of a modified correlation, which includes the momentum flux ratio inside of the logarithmic term. Finally, the multi-plume spray issuing into the cross-flow is characterized using PIV to measure droplet velocities. It is observed that the cross-flow momentum is imparted to the smaller droplets within the 15 MPa spray more easily than to those of the 10 MPa injection, but that the 15 MPa sprays also retain their momentum in the radial direction longer than the 10 MPa sprays. As such, the 10 MPa sprays align with the cross-flow axis faster.

Due to the fact that cross flow fuel injection is widely used in gas turbine engines combustors, it is important to understand the mechanisms that control the spray breakup within the cross flow. In spite of a lot of work done in this field, very few studies have been carried out under conditions typical of aerospace applications. This thesis describes a series of experiments carried out to simulate these conditions in order to characterize the formation of spray within a high speed, high pressure and high temperature cross flow close to conditions typical of aerospace applications. Fuel spray characteristics were studied for Jet-A fuel injected into a crossflow (M=0.2 and M=0.35) of preheated (T=555K) air at a chamber pressure of 4 atm. It was seen that larger droplets could be found in the periphery of the spray while smaller droplets could be found closer to the injection plate. In most cases, the droplet velocities were seen to lag the incoming air flow velocity by 20-40% and a spray hat structure was created by the jet in crossflow near the injection wall most likely caused by vortex flow created around the liquid column (jet). The influence of Weber number was then studied. It was seen that shear breakup mechanism dominates at We greater than about 100. Droplets diameters were found to be in the range of 15-30 microns for higher values of We, while larger droplets (100-200 microns) were observed at Weber number of 33. The initial sharp-edged injector was then replaced by a smooth-edged injector having. Spray characteristics from the two injectors were compared. The spray produced by the smooth countersunk injector penetrated further into the test section away from the injector orifice by approximately 2mm. This injector also produced droplets with a significantly smaller mean diameter (D10). The average droplet velocities in the vertical direction deviated from the incoming air flow velocity to a lesser degree using the countersunk injector. Meanwhile, droplets from this injector had a higher average velocity in the direction of fuel injection between the core of the spray and the orifice wall.