The ISO 8178 Draft for Particulate Measurement of Off-Highway Diesel engines specifies partial-flow dilution systems as the preferred measurement equipment. Two critical points of such systems are presented in this paper:
First, the correct implementation and/or determination of exhaust sampling and dilution ratio within the accuracy limits of ISO 8178.
Second, the influence of size, length and temperature conditioning of the transfer tube and tunnel on particulate formation, deposition and re-entrainment.
As a result of our investigations, recommendations for the proper layout of a partial-flow dilution system are given. Such a system will yield particulate emission values closely following the values obtained with a full-flow CVS system, where engine size permits the comparison. Where the engine size precludes the full-flow dilution, a particulate test equipment with proven correlation to a CVS system should be used