A New Type Partial Flow Dilution Tunnel with Geometrical Partitioning for Diesel Particulate Measurement 2001-01-3579

The authors have developed a new partial flow dilution tunnel (hereafter referred to as PPFT), whose principal device is a flux splitting gas divider, as a new means of measuring particulate emissions which can be applied to transient cycle testing of diesel engines. The advantage of this system is that it can achieve perfect constant velocity splitting by means of its structure, and theoretically can also maintain high splitting performance despite fluctuations in the exhaust flow rate, including those due to engine exhaust pulsation. We compared this system with a full tunnel by analyzing the basic performance of the system and measuring particulate matter (PM) using an actual vehicle engine.

The results obtained from measuring the relative flow rates of exhaust gas show that combining the gas divider with a turbulence reduction screen generates a flow rate distribution with axial symmetry and gives splitting performance with a high degree of correlation (regression line within , coefficient of correlation =0.9990) in any of three test cycles: D13, FTP, or ETC. In addition, a comparison of the total mass of gaseous emission components based on the results of measurements on the raw gas and gas with the emissions diluted by the PPFT demonstrated that even integral values of the gaseous emissions are accurately divided, and that the system has a high degree of repeatability even for transient cycle mode operation.

In comparison with the full tunnel, the maximum deviation in the PM mass rate in steady-state operation was no greater than 12%, and an overall correlation coefficient of 0.9799 was obtained. The average of four PM mass rate measurements was within 2% for all three test modes -D13, FTP, and ETC-and the maximum percentage deviation was within 5%. This means that the PPFT has equivalent characteristics to a full tunnel, and the same high level of repeatability as with a full tunnel was obtained.