Search Results

Knock is a major bottleneck to achieving higher thermal efficiency in spark ignition (SI) engines. The overall tendency to knock is highly dependent on fuel anti-knock quality as well as engine operating conditions. It is, therefore, critical to gain a better understanding of fuel-engine interactions in order to develop robust knock mitigation strategies. In the present work, a numerical model based on three-dimensional (3-D) computational fluid dynamics (CFD) was developed to capture knock in a Cooperative Fuel Research (CFR) engine. For combustion modeling, a hybrid approach incorporating the G-equation model to track turbulent flame propagation, and a homogeneous reactor multi-zone model to predict end-gas auto-ignition ahead of the flame front and post-flame oxidation in the burned zone, was employed.

The CFR engine is the widely accepted platform to test standard Research Octane Number (RON) and Motored Octane Number (MON) for determining anti-knock characteristics of motor fuels. With increasing interest in engine downsizing, up-torquing, and alternative fuels for modern spark ignition (SI) engines, there is a need to better understand the conditions that fuels are subjected to in the CFR engine during octane rating. To take into account fuel properties, such as fuel heat of vaporization, laminar flame speed and auto-ignition chemistry; and understand their impacts on combustion knock, it is essential to estimate accurate cylinder conditions. In this study, the CFR F1/F2 engine was modeled using GT-Power with the Three Pressure Analysis (TPA) and the model was validated for different fuels and engine conditions.

Detailed soot deposition and oxidation characteristics in a diesel particulate filter (DPF) have been experimentally examined on a unique bench-scale DPF test system that has a visualization window. The filtration and regeneration processes were visualized to examine soot deposition and oxidation behaviors on the filter channel surfaces, along with measurements of pressure drop across the filter. The pressure drop caused by trapped soot was separated from the measured total pressure drop by subtracting the pressure drop caused by the clean filter itself. Then, the soot-derived pressure-drop data, normalized (non-dimensionalized) by the volumetric flow rate, exhaust gas viscosity, and DPF volume, were used to compare filtration and regeneration characteristics at different experimental conditions, independently of flow conditions.