An experimental investigation into the soot particle emissions at early injection timings in a single-cylinder research diesel engine. (15th May 2022)

• Record Type: Journal Article
• Authors: Wang, Yifeng; Zhuang, Yuan; Yao, Minfa; Qin, Yanzhou; Zheng, Zhunqin
• Is Part Of: Fuel. Volume 316(2022)
• Publication Date: 2022-05-15
• Subjects: Diesel engine -- Soot particle -- Early injection -- Wall-wetting; LTC low temperature combustion -- RCCI reactivity controlled compression ignition -- EGR exhaust gas recirculation -- CA ATDC crank angle after top dead center -- HRTEM high-resolution transmission electron microscopy -- PM particulate matter -- PAHs polycyclic aromatic hydrocarbons -- HCCI homogeneous charge compression ignition -- PPCI partially premixed compression ignition -- PN particle number counts -- PCCI premixed charge compression ignition -- UHC unburned hydrocarbons -- IMEP indicated mean effective pressure -- SOC start of combustion -- SOI start of the fuel injection event -- dp primary particles diameter -- Rg the radius of gyration -- df fractal dimension of soot particles -- CFD computational fluid dynamics -- La fringe length, Tf: fringe separation distance -- Fd fringe tortuosity; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2022.123288
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Effect of Early-injection on smoke emissions and engine performance were examined. Soot emission at early injection timings was reduced using highly volatile fuels. As the injection timing was advanced, more loose soot aggregates were produced. The RCCI mode is an effect method to reduce soot emissions at early injection timing. Abstract: Engine experiments were performed to examine the effect of early-injection on smoke emissions and engine performance under typical low temperature combustion (LTC) and reactivity controlled compression ignition (RCCI) operating conditions. On that basis, the influence of exhaust gas recirculation (EGR), intake pressure, fuel properties and fuel injection strategy on the engine-out soot emissions at early injection timings was also assessed. At last, the morphology, nanostructure characteristics of exhaust soot particles were analyzed. The test results showed when the injection timing was advanced before −30° crank angle after top dead center (CA ATDC) and earlier, the fuel spray impinged onto the piston crown surface, and a part of fuel entered into the squish zone and expanded to reach the cylinder liner wall and entered into the crevice volume, leading to a continuous increase in soot emissions, the peak smoke emission was found to occur at −55° CA ATDC. By adopting fuels with high volatilities and a RCCI fuel delivery strategy, soot emissions can be effectively reduced at early timings. Most of the high-resolution transmission electron microscopy (HRTEM) images of the sampled soot particles showed small spherical particles with a wide range of size distribution connected, and "onion-like" fringe arrangement was found in most of the images. As the fuel injection timing was retarded from −55° to −35° CA ATDC, the samples exhibited more highly organized carbon nanostructures; the fringe tortuosity and separation distance increased, while the fringe length decreased. The formation of more ordered arrangement of graphene layers led to significant resistance to oxidation.