Partially Premixed Combustion is a concept able to combine low
smoke and NOx emissions with high combustion controllability and
efficiency. It is of interest to be able to utilize PPC in a large
operating region in order to meet the Euro VI emission legislation
without relying on NOx aftertreatment.
This paper investigates the differences in PPC characteristics
for three fuels; Diesel Swedish Mk 1, Low Octane Gasoline (70
Octane) and US Standard Gasoline (87 Octane). Engine operating
conditions, combustion characteristics, emissions and efficiency
are in focus.
The experiments were carried out at a range of operating points
on a Volvo MD13 which is a six-cylinder heavy-duty engine. At each
operating point three combinations of EGR level and λ-value were
evaluated. 1. High EGR/High λ, 2. High EGR/Reduced λ, and 3.
Reduced EGR/High λ.
Further, for all these three conditions, four combustion timings
were tested reaching from advanced combustion timing at 3 CAD ATDC
to retarded combustion timing at 9 CAD ATDC. The indicated load and
the combustion timing were controlled cylinder individually by a
feedback controller.