Experimental study on particle size distribution of gasoline compression ignition (GCI) at low-load condition

A modified single-cylinder test engine was utilized in this study to figure out the effects of injection timing, exhaust gas recirculation (EGR) and Polyoxymethylene dimethyl ethers (PODE) additive on particle size distribution characteristics. The study was performed under gasoline compression ignition (GCI) mode, whose injection timing range was varied from -22 to -10 ?CA ATDC under the examined condition, and particle size distributions were measured by an exhaust particle size spectrometer TSI EEPS 3090. The results showed that, the nuclei-mode highly dominates the particle size distribution, and the particle size corresponded to peak particle number tends to be uniformly distributed around 20 nm regardless of the combustion control parameters and fuel properties. A unimodal distribution is appeared without and with EGR, while the particle size distribution shifts to the larger size and peak particle number is lower with the advance of injection timing. Compared with the no EGR case, an overall increase of particle number can be observed by applying EGR. Furthermore, the peak particle number and particle number concentration can be greatly reduced by more than two orders of magnitude by adding 10% PODEn, but further increasing blending ratio of PODEn to 20% has much less effect. In a last step, indicated specific particle number (ISPN) was analyzed, suggesting that the ISPN of both total particles and particles smaller than 50 nm exhibits increase first and then decrease with the increase of EGR. Overall, the particle number control of GCI mode should be based on the well matching of combustion control parameters and fuel properties.

Automated summary

The study found that under gasoline compression ignition (GCI) mode, the particle size distribution is mainly in nuclei-mode with the particle size distributed around 20 nm. Both with and without EGR, a unimodal distribution is observed. Advancing injection timing shifts the particle size distribution towards larger sizes.