Experimental Investigation on Wall Film Distribution of Dimethyl Ether/Diesel Blended Fuels Formed during Spray Wall Impingement

Abstract

Dimethyl ether (DME)/diesel blended fuels are used to improve the emissions caused by spray wall impingement during the early injection period. However, experimental results have showed that the spray wall impingement still cannot be avoided due to the engine structure and low density of the in-cylinder charge at the early injection timing. Furthermore, the wall film formed in the spray wall impingement process directly affects fuel/air mixture formation, combustion, exhaust emissions and oil quality subsequently. In this paper, the wall film distribution of DME/diesel blended fuels formed during the spray wall impingement process has been experimentally investigated. The variations of wall film distribution, wall film area and average thickness with different injection pressures, impingement distances, impingement angles and blending ratios have been discussed under both dry wall and wet wall conditions. Results showed that the wall film distribution styles were mainly determined by the spray impingement momentum. The variation of the wall film area and average thickness were affected by three factors including the impingement momentum, wall film mass and fuel properties. Correlation analysis was introduced in order to evaluate the effect of each impact factor on the variation of wall film area and average thickness.

Experimental Investigation on Effect of Wall Roughness and Lubricant Film on the Adhered Fuel Film of N-Butanol-Diesel Blends after Spray Impingement

“…As shown in Figure 4, the adhered fuel film accumulates around the impacting central point and presents a "mountain" shape. In Reference [31], it has made some similar definitions about thickness and diameter of adhered film, but it didn't consider the effect of the original lubricant film thickness. Therefore, we should re-define the metrical parameters.…”

“…Its working principle is based on the Lambert-Beer law [36], which can calculate the liquid film thickness by using light absorbance after a light beam has passed through the film. Details of this device are described in References [31,35]. To study the effect of wall roughness on the fuel film's characteristics, four circular cold-rolled steel plates with different surface roughness types (Sq = 0.24 µm, 1.00 µm, 1.84 µm, 2.59 µm) have been used.…”

“…In our previous work [30][31][32], we have studied the effect of the injection parameters, ambient parameters, and fuel characteristics on the impingement process and adhered film distribution. However, according to the analysis above, the surface condition of the impinged wall also plays a significant role in droplets' adhesion and splashing.…”

Effect of Fuel Injection Strategy on the Carbonaceous Structure Formation and Nanoparticle Emission in a DISI Engine Fuelled with Butanol

“…This is also important bearing in mind that injection needs to be advanced during boosted operation at high engine speed [15] in order to maintain the aforementioned compromise between intake air velocity and available spray penetration length [11]. The main mechanism is fuel impingement on the piston and liner [16], with significant fuel effects [17]. Wall wetting is directly related to load, meaning that as engine output is increased at fixed rotational speed, larger quantities of fuel need to be injected; several mechanisms during air-fuel mixture formation contribute to complex effects on charge distribution during combustion, that can be identified through combined experimental and numerical investigations [18], [19].…”

Experimental Research on the Injection Rate of DME and Diesel Fuel in Common Rail Injection System by Using Bosch and Zeuch Methods

“…The research on the effects of the spray angle and injection strategies (single injection, multi-injection, etc.) on the combustion characteristics [11][12][13][14] which are composed of particle size distribution [13], spray characteristics in a various pressure condition [14][15][16], combustion and emission performances, and EGR rate [17]-was investigated via numerical and experimental methodologies. Homogeneous charge compression ignition (HCCI) and bulk combustion were also investigated.…”