Experiences with a Mini-Dilution System for Engine Homologation and Development

The full-flow CVS dilution system is defined by the US EPA for particulate measurement of Heavy-Duty (HD) Diesel engines. Such systems are bulky and expensive. The EEC (1), Brazil and many other countries have therefore accepted the use of so-called “Partial-Flow Dilution Systems” (PDS) for homologation of HD engines. The ISO TC70 (2) committee even recommends such systems for the emissions measurement of Off-Road Diesel engines. Such systems sample and dilute only a fraction of the total exhaust, therefore they are much smaller than a full-flow CVS.

However, it is required that the most important properties and conditions of a full-flow CVS systems are also fulfilled by a PDS. Therefore an accurate sampling and dilution control must be implemented in all Partial-Flow Dilution Systems (which makes such systems more complicated than a full-flow CVS). Various types of control have been developed and are described in the EEC and ISO regulations. Their advantages and drawbacks will be discussed in the paper. Special emphasis will be given to their applicability for the steady-state tests defined by the EEC, Brazil and ISO for engine homologation. Comparison of this system with full-flow CVS data are also presented.

Moreover, the possibilities to use such an equipment for transient (US HD-cycle) testing during development phases and for quasi-transient testing are discussed. Future application for gaseous emission measurement in future LEV and ULEV testing will be investigated.