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

2017 ◽  
Vol 232 (8) ◽  
pp. 1121-1136 ◽  
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.

Visualization of diesel spray and combustion from lateral side of two-dimensional piston cavity in rapid compression and expansion machine, second report: Effects of injection pressure and interval of split injection

2021 ◽  
pp. 146808742199306
Author(s):  
Chengyuan Fan ◽  
Keiya Nishida ◽  
Yoichi Ogata
Keyword(s):  
Combustion Process ◽  
Injection Pressure ◽  
Lateral Side ◽  
Two Dimensional ◽  
Split Injection ◽  
High Injection ◽  
High Injection Pressure ◽  
Compression And Expansion ◽  
Combustion Processes ◽  
Injection Pressures

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.

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

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.

scholarly journals Optical study on characteristics of non-reacting and reacting diesel spray with different strategies of split injection

2018 ◽  
Vol 20 (6) ◽  
pp. 606-623 ◽  
Author(s):  
Jose M Desantes ◽  
José M García-Oliver ◽  
Antonio García ◽  
Tiemin Xuan
Keyword(s):  
High Speed ◽  
Dwell Time ◽  
Soot Formation ◽  
Operating Conditions ◽  
Split Injection ◽  
Injection Duration ◽  
Soot Mass ◽  
Lift Off ◽  
Combustion Processes ◽  
Injection Strategies

Even though studies on split-injection strategies have been published in recent years, there are still many remaining questions about how the first injection affects the mixing and combustion processes of the second one by changing the dwell time between both injection events or by the first injection quantity. In this article, split-injection diesel sprays with different injection strategies are investigated. Visualization of n-dodecane sprays was carried out under both non-reacting and reacting operating conditions in an optically accessible two-stroke engine equipped with a single-hole diesel injector. High-speed Schlieren imaging was applied to visualize the spray geometry development, while diffused background-illumination extinction imaging was applied to quantify the instantaneous soot production (net result of soot formation and oxidation). For non-reacting conditions, it was found that the vapor phase of second injection penetrates faster with a shorter dwell time and independently of the duration of the first injection. This could be explained in terms of one-dimensional spray model results, which provided information on the local mixing and momentum state within the flow. Under reacting conditions, interaction between the second injection and combustion recession of the first injection is observed, resulting in shorter ignition delay and lift-off compared to the first injection. However, soot production behaves differently with different injection strategies. The maximum instantaneous soot mass produced by the second injection increases with a shorter dwell time and with longer first injection duration.

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

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.

LES Analysis of Mixture Formation and Combustion Processes in a Diesel Spray

2011 ◽  
Vol 5 (2) ◽  
pp. 102-111 ◽  
Author(s):  
Hirokazu Kojima ◽  
Hiroshi Kawanabe ◽  
Takuji Ishiyama
Keyword(s):  
Diesel Spray ◽  
Mixture Formation ◽  
Combustion Processes

Effects of ultra-high injection pressure and micro-hole nozzle on flame structure and soot formation of impinging diesel spray

2011 ◽  
Vol 88 (5) ◽  
pp. 1620-1628 ◽  
Author(s):  
Xiangang Wang ◽  
Zuohua Huang ◽  
Wu Zhang ◽  
Olawole Abiola Kuti ◽  
Keiya Nishida
Keyword(s):  
Soot Formation ◽  
Flame Structure ◽  
Injection Pressure ◽  
Diesel Spray ◽  
High Injection ◽  
High Injection Pressure ◽  
Micro Hole

scholarly journals Flame Front and Burned Gas Characteristics for Different Split Injection Ratios and Phasing in an Optical GDI Engine

2019 ◽  
Vol 9 (3) ◽  
pp. 449 ◽  
Author(s):  
Santiago Martinez ◽  
Simona Merola ◽  
Adrian Irimescu
Keyword(s):  
Flame Front ◽  
Soot Formation ◽  
Direct Injection ◽  
Combustion Process ◽  
Pollutant Emissions ◽  
Optical Data ◽  
Cylinder Pressure ◽  
Split Injection ◽  
Gdi Engine ◽  
Injection Strategies

Direct-injection in spark-ignition engines has long been recognized as a valid option for improving fuel economy, reducing CO2 emissions and avoiding knock occurrence due to higher flexibility in control strategies. However, problems associated with mixture formation are responsible for soot emissions, one of the most limiting factors of this technology. Therefore, the combustion process and soot formation were investigated with different injection strategies on a gasoline direct injection (GDI) engine. The experimental analysis was realized on an optically accessible single cylinder engine when applying single, double and triple injection strategies. Moreover, the effect of fuel delivery phasing was also scrutinized by changing the start of the injection during late intake- and early compression-strokes. The duration of injection was split in different percentages between two or three pulses, so as to obtain close to stoichiometric operation in all conditions. The engine was operated at fixed rotational speed and spark timing, with wide-open throttle. Optical diagnostics based on cycle resolved digital imaging was applied during the early and late stages of the combustion process. Detailed information on the flame front morphology and soot formation were obtained. The optical data were correlated to in-cylinder pressure traces and exhaust gas emission measurements. The results suggest that the split injection of the fuel has advantages in terms of reduction of soot formation and NOx emissions and a similar combustion performance with respect to the single injection timing. Moreover, an early injection resulted in higher rates of heat release and in-cylinder pressure, together with a reduction of soot formation and flame distortion. The double injection strategy with higher percentage of fuel injected in the first pulse and early second injection pulse showed the best results in terms of combustion evolution and pollutant emissions. For the operative condition studied, a higher time for mixture homogenization and split of fuel injected in the intake stroke shows the best results.

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