Heterogeneous engine in-cylinder mixing measurements using a tracer technique: Part 2. Final report

A diagnostic technique for determining fluid motion and mixing in heterogeneous internal combustion engines was developed and tested. Once per cycle, a rapid-acting valve injected a small, discrete quantity of a gaseous tracer directly into the combustion chamber. At a specific place and time after tracer injection, a similar valve extracted a small quantity of cylinder gas which was analyzed for cycle averaged tracer concentration. For motored engine tests, an ethane/nitrogen mixture was used as the tracer with a flame ionization detector for gas analysis. Radioactive argon was employed as the tracer for fired engine tests with a sodium iodide scintillation counter as a detector. A mapping in time and space of tracer motion was constructed from data and sources of error discussed. The apparatus worked quite well. The test engine was an open-chambered single-cylinder diesel. Data taken just prior to top center of the compression stroke indicated that the tracer puff remained largely unmixed with air over the short distance between injection and sampling valves. A swirl rate of 2.5 was calculated from motoring data. Firing results showed the tracer pulse higher in peak concentration and more compact than for the motored case