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The main objective of the current paper was to investigate the fluid flow and pressure loss characteristics of DPF substrates with asymmetric channels utilizing 3-D Computational Fluid Dynamics (CFD) methods. The ratio of inlet to outlet channel width is 1.2. First, CFD results of velocity and static pressure distributions inside the inlet and outlet channels are discussed for the baseline case with both forward and reversed exhaust flow. Results were also compared with the regular DPF of same cell structure and wall material properties. It was found that asymmetrical channel design has higher pressure loss. The lowest pressure loss was found for the asymmetrical channel design with smaller inlet channels. Then, the effects of DPF length and filter wall permeability on pressure loss, flow and pressure distributions were investigated.

Emissions sample probes are widely used in engine and vehicle emissions development testing. Tailpipe bag summary data is used for certification, but the time-resolved (or modal) emissions data at various points along the exhaust system is extremely important in the emission control technology development process. Exhaust gas samples need to be collected at various locations along the exhaust aftertreatment system. Typically, a tube with a small diameter is inserted inside the exhaust pipe to avoid any significant effect on flow distribution. The emissions test equipment draws a gas sample from the exhaust stream at a constant volumetric flow rate (typically around 10 SLPM). The sample probe tube delivers exhaust gas from the exhaust pipe to emissions test equipment through multiple holes on the surface of tube. There can be multiple rows of holes at different axial planes along the length of the sample probe as well as multiple holes on a given axial plane of the sample probe.

Multidimensional modeling is used to study air-fuel mixing in a direct-injection spark-ignition engine. Emphasis is placed on the effects of the start of fuel injection on gas/spray interactions, wall wetting, fuel vaporization rate and air-fuel ratio distributions in this paper. It was found that the in-cylinder gas/spray interactions vary with fuel injection timing which directly impacts spray characteristics such as tip penetration and spray/wall impingement and air-fuel mixing. It was also found that, compared with a non-spray case, the mixture temperature at the end of the compression stroke decreases substantially in spray cases due to in-cylinder fuel vaporization. The computed trapped-mass and total heat-gain from the cylinder walls during the induction and compression processes were also shown to be increased in spray cases.

In modeling of engine fuel-air mixing, it is desired to be able to predict fuel spray atomization under different injection and ambient conditions. In this work, a previously developed sheet atomization model was studied for this purpose. For sprays from a pressure-swirl injector, it is assumed in the model that the fuel flows out the injector forming a conical liquid film (sheet), and the sprays are formed due to the disintegration of the sheet. Modified formulations are proposed to estimate sheet parameters including sheet thickness and velocity at the nozzle exit. It was found that the fuel flow rate of a swirl injector satisfied the correlation well. Computations of correlation well. Computations of the sprays injected in an engine with a side-mounted injector were performed for conditions that duplicated a set of experiments performed in an optical engine. The computed results were compared with the spray images obtained from the optical engine using elastic (Mie) scattering.