Experimental Study of Diesel Spray and Combustion Processes under Split Injection Strategy—Phenomena Observation from Lateral Side of a Two-Dimensional Piston Cavity in RCEM

The effect of split injection on the fuel spray and combustion processes in a rapid compression and expansion machine was investigated using the visualization process. A two-dimensional piston cavity, designed with the cross section of a reentrant piston, was installed in the combustion chamber to observe the combustion process from the lateral side. Combustion experiments were conducted with injection pressures of 80 MPa, 120 MPa, and 180 MPa and an O2 concentration of 15%. The spray/wall interaction, mixture distribution, and ignition location were investigated using the shadow method. Along with natural flame luminescence, different spray impinging behaviors on combustion process were studied. Furthermore, the combustion characteristics of in-cylinder pressure, apparent heat release rate, and combustion phase were recorded and analyzed simultaneously. The results showed that both high injection pressure and split injection with a longer interval effectively improved the combustion performance. In addition, when the pilot injection was advanced further, the injection interval had a larger influence in reducing soot generation, while the effect of high injection pressure on heat release decreased. Flame separation was found to occur at high injection pressures. It was observed that the flame separation caused by the strong spray momentum was beneficial for reducing soot generation owing to the greater fuel-air interaction area. The spray and combustion processes were investigated in detail, and the significant effects of different injection pressures and injection intervals on combustion performance with the split injection method were highlighted.

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

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/0954407017724246 ◽

2017 ◽

Vol 232 (8) ◽

pp. 1121-1136 ◽

Cited By ~ 5

Author(s):

Kang Yang ◽

Hirotaka Yamakawa ◽

Keiya Nishida ◽

Youichi Ogata ◽

Yusuke Nishioka

Keyword(s):

Soot Formation ◽

Single Injection ◽

Injection Pressure ◽

Diesel Spray ◽

Two Dimensional ◽

Mixture Formation ◽

Split Injection ◽

Main Injection ◽

Combustion Processes ◽

Injection Strategies

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 (α-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 high-speed 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.

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Experimental study on microscopic and macroscopic characteristics of diesel spray with split injection

Fuel ◽

10.1016/j.fuel.2016.01.083 ◽

2016 ◽

Vol 174 ◽

pp. 140-152 ◽

Cited By ~ 33

Author(s):

Ziman Wang ◽

Hongming Xu ◽

Changzhao Jiang ◽

Miroslaw L. Wyszynski

Keyword(s):

Experimental Study ◽

Diesel Spray ◽

Split Injection

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Visualization of diesel spray and combustion from lateral side of two-dimensional piston cavity in rapid compression and expansion machine

International Journal of Engine Research ◽

10.1177/1468087420962298 ◽

2020 ◽

pp. 146808742096229

Author(s):

Chengyuan Fan ◽

Daoyuan Wang ◽

Keiya Nishida ◽

Yoichi Ogata

Keyword(s):

High Speed ◽

Combustion Process ◽

Video Camera ◽

Lateral Side ◽

Two Dimensional ◽

Split Injection ◽

Compression And Expansion ◽

Color Video ◽

Wall Interaction ◽

Injection Strategies

Effect of spray/wall interaction in a rapid compression and expansion machine on mixture formation, ignition location, and soot generation was investigated. A two-dimensional piston cavity designed as the cross section of a reentrant piston was utilized to observe the spray and combustion process from the lateral side. The experiment was conducted at 120 MPa injection pressure under single and split injection strategies with an ambient gas of 15% O2 concentration. A shadow methodology was applied to investigate the interaction between the fuel spray and the piston cavity. Combined with the natural flame luminosity captured by a high-speed color video camera, the behaviors of the impinging spray and the combustion process were studied. The combustion characteristics of the in-cylinder pressure, heat release and combustion phase were recorded and analyzed simultaneously. The results showed that the split injection strategies effectively softened the heat release trace and promoted the onset of the main combustion. The cool-flame phenomenon was captured by using the high-speed color video camera, and the intense ignition was observed when the pilot spray was controlled to impinge on the lower lip of the piston rim. Moreover, results also showed that further extending the mixing process of the pilot spray is inclined to form a homogeneous mixture which was beneficial for the promotion of low-temperature combustion and the reduction of soot generation. This research provides a detailed investigation on the spray and combustion process and it highlights the significant effect of spray/wall interaction on the subsequent combustion process.

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Effects of dwell time of split injection on mixture formation and combustion processes of diesel spray

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/09544070211053693 ◽

2021 ◽

pp. 095440702110536

Author(s):

Samir Chandra Ray ◽

Jaeheun Kim ◽

Scinichi Kakami ◽

Keiya Nishida ◽

Youichi Ogata

Keyword(s):

Dwell Time ◽

Equivalence Ratio ◽

Diesel Spray ◽

Spray Combustion ◽

Mixture Formation ◽

Split Injection ◽

Lean Mixture ◽

Rich Mixture ◽

The Rich ◽

Combustion Processes

The effects of dwell time on the mixture formation and combustion processes of diesel spray are investigated experimentally. A commercial multihole injector with a 0.123 mm hole diameter is used to inject the fuel. The injection procedure is either a single or split injection with different dwell times, whereas the total amount of injected fuel mass is 5.0 mg per hole. Three dwell times are selected, that is, 0.12, 0.32 and 0.54 ms, with a split ratio of 7:3 based on previous findings. The vapour phase is observed, and the mixture formation pertaining to the equivalence ratio is analysed using the tracer laser absorption scattering (LAS) technique. A high-speed video camera is used to visualise the spray combustion flame luminosity, whereas a two-colour pyrometer system is used to evaluate the soot concentrations and flame temperature. An analysis of the mixture formation based on the spray evaporating condition reveals a more concentrated area of the rich mixture within a 0.32 ms dwell time. In the shortest dwell time of 0.12 ms, the equivalence ratio distribution decreases uniformly from the rich mixture region to the lean mixture region. In the case involving a shorter dwell time, a suitable position for the second injection around the boundaries of the first injection is obtained by smoothly growing the lean mixture and avoiding the large zone of the rich mixture. Therefore, the shortest dwell time is acceptable for mixture formation, considering the overall distribution of the equivalence ratios. Spray combustion analysis results show that the soot formation rate of the single injection and 0.32 ms dwell time case is high and decreases quickly, implying a rapid reduction in the high amount of soot. Consequently, 0.12 ms can be considered the optimal dwell time due to the ignition delay and relatively low soot emission afforded.

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