Effect of flat-wall impingement on diesel spray combustion

Proceedings of the Institution of Mechanical Engineers, Part D:

et al. 2017

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The objective of this study is to obtain an enhanced understanding of the effect of split injection on mixture formation and combustion processes of diesel spray. A two-dimensional (2D) piston cavity of the same shape as that used in a small-bore diesel engine was employed to form the impinging spray flame. The fuel was injected into a high pressure, high temperature constant volume vessel through a single-hole nozzle with a hole diameter of 0.11 mm. The injection process comprised a pre-injection followed by the main injection. The main injection was carried out either as a single injection of injection pressure 100 MPa (Pre + S100), or by two types of split injection of injection pressure 160 MPa. The latter two types were defined by mass fraction ratios 1:1 and 3:1 (Pre + D160_1-1, Pre + D160_3-1). In order to observe the spray mixture formation process, the tracer laser absorption scattering (LAS) techique was adopted. Tracer LAS fuel with 97.5 vol% of n-tridecane and 2.5 vol% of 1-methylnaphthalene (a-MN) was employed. The spatial distributions of the vapor and liquid phases and the spray mixture formation characteristics in the 2D piston cavity for the three injection strategies were investigated. The diesel spray combustion and soot formation processes were studied using a highspeed video camera. The flame structure and soot formation process were examined using two-color pyrometry. The experimental results revealed that the split-injection vapor distribution was significantly more homogeneous than that of the single injection. The main injection fuel caught up with the pre-injection fuel and provided the spray tip with substantial additional momentum, enabling it to advance further. A high soot concentration and low temperatures appeared near the cavity wall region under the three injection strategies. The soot reduction rate for split injection was higher than that for single injection. The second main injection caught up with the previous injection's flame, which deteriorated the combustion and resulted in higher soot generation. The effect of split injection on the process of soot evolution finished at the same time as that of single injection.

Section: Introductionmentioning

confidence: 99%

Effect of split injection on mixture formation and combustion processes of diesel spray injected into two-dimensional piston cavity

Yang

Yamakawa

Proceedings of the Institution of Mechanical Engineers, Part D:

et al. 2017

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“…At the impingement distance of 50 mm with longer impinging path, combustion became slow with lower temperature and soot formation was reduced due to the improved fuel air mixing before the occurrence of combustion. According to Li et al 12 experiment, combustion is enhanced by increasing the impingement distance. As shown in Figure 11, distribution of flame is similar to KL factor, thereby temporal changes of luminous flame area are also similar to the KL factor.…”

Section: Resultsmentioning

confidence: 99%

Experimental study on flat-wall impinging spray flame and its heat flux on wall under diesel engine–like condition: First report—effect of impingement distance

Mahmud

Kurisu

Proceedings of the Institution of Mechanical Engineers, Part D:

et al. 2018

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Reducing heat loss is one of the most important development concerns for improving the thermal efficiency of the diesel engine. In order to know heat transfer through the combustion chamber wall more clearly, the effects of flame impingement on transient heat flux to the wall were investigated. Using a high-pressure and high-temperature chamber under diesel engine–like conditions, fuel was injected from a single-hole injector against an impingement wall. Surface heat flux of the impingement wall was measured by temperature with three thin film thermocouple heat flux sensors. Simultaneously, luminous flame, flame temperature, and soot distribution were also investigated. The results showed that temperature near the wall and flame contact area have great influence on the local heat flux. Furthermore, local heat flux, combustion, and soot formation reached maximum levels at some spray impingement distance to the wall.

“…Thus, h(x, y) can be calculated because the tridecane volume was calculated as 10% of the mixture, and the averaged reference dry image was obtained before the liquid deposited on the glass. Then DI(x, y) can be calculated using equation (1). Eventually, one point with h(x, y) and DI(x, y) was obtained.…”

Section: Image Processingmentioning

confidence: 99%

“…This is due to the better air and mixture control by DI compared to port fuel injection. [1][2][3] However, the impingement of liquid fuel on the wall of the combustion chamber and piston is a major drawback of this technique, because wall wetting leads to pool fires linked with rich diffusion flames on the top of the liquid deposit. 4,5 This can contribute to unwanted pollutant formation and an increase in unburned hydrocarbons.…”

Section: Introductionmentioning

confidence: 99%

Effect of spray impingement distance on piston top fuel adhesion in direct injection gasoline engines

Luo

International Journal of Engine Research

Uchitomi

et al. 2018

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Direct injection is an attractive technology for improving fuel economy and engine performance in gasoline engines. However, the adhered fuel formed on the piston surface has significant influence on the combustion efficiency and emissions. To obtain a better understanding of fuel adhesion, this work involved investigation of the spray and impingement on a flat wall through a mini-sac injector with a single hole. Different impingement distances and injection pressures were investigated. The evolution of the impinging spray was obtained by the Mie scattering method. The refractive index matching method was applied to measure fuel adhesion. The mass, area, and thickness of adhesion under different conditions were compared. The experimental results show that the fuel adhesion on the wall increases significantly with a large impingement distance. Moreover, the maximum thickness increases and the thickness uniformity of the fuel adhesion declines under a large impingement distance condition.