Experimental investigation on characterization of solid soot particle emissions using in-situ developed thermal desorption system from reactivity-controlled compression ignition engine

This study experimentally investigates the solid soot particle number emissions from the gasoline-diesel (GD) and CNG-diesel reactivity-controlled compression ignition (RCCI) engines. The volatile organic fraction should be removed from the sampling gas before particle measurement to analyze the correct number of solid particle emissions. In the present study, a thermodesorption system is developed to remove the volatile particles from the exhaust sample. This study examines the effect of the thermodesorption system on emissions of nanoparticles from the RCCI engine. The intake manifold of the diesel engine is modified to inject gasoline/CNG to run an engine in RCCI mode. The experiments are performed at different fuel premixing ratios (r_p). The fuel is varied by changing the port-injected gasoline/CNG mass. A differential mobility spectrometer has been used to measure the emissions of nanoparticles. The thermophoresis and diffusion particle losses in the thermo-desorption system are estimated. It is found that the diffusion losses are 4.7%, 2.0%, 1.0%, and 0.2% for 10, 30, 50, and 100 nm diameter particles, respectively, whereas the thermophoresis losses are 7.6% for the same particle diameter. The results depict that the developed thermodesorption system can remove volatile particles with high volatile particle removal efficiency. Nucleation mode particles (NMPs) are significantly reduced with the thermodesorption system. The peak of the NMPs in the 10–30 nm size range is reduced by an order of magnitude when sampling is performed with the developed thermo-desorption system at all premixing ratios for gasoline-diesel and CNG-diesel RCCI combustion.