A First Implementation of an Efficient Combustion Strategy in a Multi Cylinder Two-Stage Turbo CI-Engine Producing Low Emissions While Consuming a Gasoline/EHN Blend 2013-24-0103

A Gasoline Compression Ignition combustion strategy was developed and showed its capabilities in the heavy duty single cylinder test-cell, resulting in indicated efficiencies up to 50% and low engine out emissions applying to EU VI and US 10 legislations while the soot remained at a controllable 1.5 FSN. For this concept a single-cylinder CI-engine was used running at a lambda of ∼1.6 and EGR levels of ∼50% and a modified injection strategy. Part of this strategy was also the use of a gasoline blended with an ignition improver, giving the blend a cetane number in the range of regular diesel; ∼50. In this paper a step is taken towards implementation of this combustion concept into a multi-cylinder light duty standalone CI-engine.

A standard CI-engine was modified so that its gas-exchange system could deliver the requested amounts of EGR and lambda. A long-route EGR system was installed, furthermore a two stage turbocharger system delivered the boost and increased the overall engine efficiency. A blend of gasoline RON 87 and 5 vol.% EHN was tested and with a cetane number of 55 it showed the right auto-ignition capabilities.

Injection sweeps regarding: EGR amount, rail pressure, timing main combustion peak, separation between pilot and main injection and pilot amount were performed. These sweeps resulted in an optimal injection strategy for this test engine in two engine load points both at 6 bar BMEP but at 1000 and 1500 rpm. As requested the soot emissions remained below 1.5 FSN, the NO_x levels were at 2.82 and 3.20 g/kWh for 1000 and 1500 rpm respectively. Efficiency for the engine load point at 1000 rpm was 34.4 % for the load point at 1500 rpm this was 23.4% due to the excessive pressure loss over the engine created by the modified gas-exchange system.