Search Results

Intake-generated flow fields and subsequent combustion characteristics were studied respectively in a reciprocating piston water analog flow apparatus and in firing engines. Three 1.6L, I4, 4-valve engine cylinder heads were tested with and without one intake port blocked to generate six distinctly different inducted flow fields. Fluid velocity distributions and flow field structure (“zero mean motion”, “swirl”, and “tumble”) were determined at BDC of the induction stroke using 2-D or 3-D particle tracking velocimetry. Swirl ratios based on steady-flow data were also obtained. The burn duration for each case was determined from cylinder pressure data. The results show that burn duration decreased with increases in tumble or swirl strength. Previously observed correlations between burn duration and swirl hold if swirl is the major component of the large-scale motion.

An experimental and analytical study was conducted to investigate the effects of load control with port throttling on stability and fuel consumption at idle. With port throttling, the pressure in the intake port increases during the valve-closed period due to flow past the throttle. If the pressure in the port recovers to ambient before the valve overlap period, back flow into the intake system from the cylinder is eliminated. This allows increased valve overlap to be used without increasing the residual mass fraction in the cylinder. Results showed that, with high valve overlap and port throttling, idle stability and fuel consumption can be maintained at values associated with low overlap in a conventionally throttled engine. However, implementation of this concept in production is regarded to require precision-fit and balanced port throttles, an external vacuum pump for vacuum systems support, and revision of the PCV system.