scholarly journals Investigation of Puffing and Micro-Explosion of Water-in-Diesel Emulsion Spray Using Shadow Imaging

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2281 ◽  
Author(s):  
Mhadi A. Ismael ◽  
Morgan Heikal ◽  
A. A. Aziz ◽  
Cyril Crua ◽  
Mohmmed El-Adawy ◽  
...  
Keyword(s):  
Droplet Size ◽  
High Speed ◽  
Elevated Temperatures ◽  
Injection Pressure ◽  
Image Processing Algorithm ◽  
Long Distance ◽  
Secondary Atomization ◽  
High Injection ◽  
Digital Microscope ◽  
Injection Pressures

Water-in-diesel emulsions potentially favor the occurrence of micro-explosions when exposed to elevated temperatures, thereby improving the mixing of fuels with the ambient gas. The distributions and sizes of both spray and dispersed water droplets have a significant effect on puffing and micro-explosion behavior. Although the injection pressure is likely to alter the properties of emulsions, this effect on the spray flow puffing and micro-explosion has not been reported. To investigate this, we injected a fuel spray using a microsyringe needle into a high-temperature environment to investigate the droplets’ behavior. Injection pressures were varied at 10% v/v water content, the samples were imaged using a digital microscope, and the dispersed droplet size distributions were extracted using a purpose-built image processing algorithm. A high-speed camera coupled with a long-distance microscope objective was then used to capture the emulsion spray droplets. Our measurements indicated that the secondary atomization was significantly affected by the injection pressure which reduced the dispersed droplet size and hence caused a delay in puffing. At high injection pressure (500, 1000, and 1500 bar), the water was evaporated during the spray and although there was not enough droplet residence time, puffing and micro-explosion were clearly observed. This study suggests that high injection pressures have a detrimental effect on the secondary atomization of water-in-diesel emulsions.

scholarly journals Large-Eddy Simulation Study of Ultra-High Fuel Injection Pressure on Gasoline Sprays

2020 ◽  
Author(s):  
S. Wadekar ◽  
A. Yamaguchi ◽  
M. Oevermann
Keyword(s):  
Large Eddy Simulation ◽  
Droplet Size ◽  
Injection Pressure ◽  
Air Entrainment ◽  
Entrainment Rate ◽  
Eddy Simulation ◽  
High Injection ◽  
Large Eddy ◽  
The Impact ◽  
Injection Pressures

Abstract The development of gasoline spray at ultra-high injection pressures was analyzed using Large-Eddy simulation (LES). Two different nozzle hole geometries, divergent and convergent shape, were considered to inject the fuel at injection pressures ranging from 200 to 1500 bar inside a constant volume spray chamber maintained at atmospheric conditions. The discrete droplet phase was treated using a Lagrangian formulation together with the standard spray sub-models. The numerical results were calibrated by reproducing experimentally observed liquid penetration length and efforts were made to understand the influence of ultra-high injection pressures on the spray development. The calibrated model was then used to investigate the impact of ultra-high injection pressures on mean droplet size and droplet size distribution. In addition, the spray-induced large-scale eddies and entrainment rate were evaluated at different ultra-high injection pressures. Overall, simulation results showed a good agreement with available measurement data. At ultra-high injection pressures mean droplet sizes were significantly reduced and comprised very high velocities. Integral length scales of spray-induced turbulence and air entrainment rate into the spray were larger at higher injection pressure compared to lower ones. Graphic abstract

Study of Diesel Air-Fuel Mixing and Combustion at High Injection Pressures in a Rapid Compression Machine

2012 ◽  
Author(s):  
I. Pribicevic ◽  
T. Sattelmayer
Keyword(s):  
Injection Pressure ◽  
Nozzle Diameter ◽  
Oh Radicals ◽  
Rapid Compression Machine ◽  
Spray Cone ◽  
Spray Penetration ◽  
High Injection ◽  
Fuel Mixing ◽  
Rapid Compression ◽  
Injection Pressures

Diesel air-fuel mixing and combustion have been investigated in a Rapid Compression Machine (RCM). The measurements were performed at high injection pressures up to 260 MPa and under reacting and non-reacting conditions. The spray was injected through solenoid-controlled multi-hole injectors. Two nozzles were applied with orifice diameters of 175 μm (D175) and 150 μm (D150), respectively. The visualization of the penetration of the liquid and the gaseous phase as well as the spray cone angle under evaporative, non-reacting conditions was carried out by the shadowgraph imaging technique in combination with a high speed camera. For combustion studies the flame luminosity of the flame as well as the chemiluminescence signals emitted by the OH radicals in the UV range were detected. Investigations revealed different behavior of the macroscopic spray characteristics with the two applied nozzles when increasing the injection pressure from 200 MPa to 260 MPa. With the larger nozzle diameter (D175) the spray penetration and the spray propagation velocity increase as the injection pressure is increased. On the contrary to that, with the smaller nozzle diameter (D150) an increase of the injection pressure had no effect on the spray velocity. With 260 MPa a higher spray penetration was only observed at the beginning of the injection due to the faster opening of the needle. The further propagation of the tip of the spray was similar with 200 MPa and 260 MPa. With both applied nozzles the injection pressure has little effect on the penetration length of the liquid phase. At an applied injection pressure of 200 MPa the near-nozzle spray angle is wider with D175, whereas similar spray angles were observed at 260 MPa. From the measurements in reacting atmosphere an earlier ignition of the fuel and a faster combustion could be shown with nozzle D150. In addition, a higher combustion pressure was measured. This can be attributed to better air-fuel mixing and a higher premixed portion, which was confirmed by the analysis of the spray angles in the far-nozzle region obtained from the shadowgraph images at non-reacting conditions.

Effect of ultra-high injection pressure up to 50 MPa on macroscopic spray characteristics of a multi-hole gasoline direct injection injector fueled with ethanol

2017 ◽  
Vol 232 (8) ◽  
pp. 1092-1104 ◽  
Author(s):  
Xiang Li ◽  
Yi-qiang Pei ◽  
Jing Qin ◽  
Dan Zhang ◽  
Kun Wang ◽  
...  
Keyword(s):  
High Speed ◽  
Direct Injection ◽  
Cone Angle ◽  
Injection Pressure ◽  
Fuel Mixture ◽  
Gasoline Direct Injection ◽  
Spray Characteristics ◽  
High Injection ◽  
High Injection Pressure ◽  
Wall Impingement

This research systematically studied the effect of injection pressure on macroscopic spray characteristics of a five-hole gasoline direct injection (GDI) injector fueled with ethanol, especially under ultra-high injection pressure up to 50 MPa. The front and side views of sprays were photographed by the schlieren method using a high-speed camera. Various parameters, including spray development stages, cone angle, penetration, area and irregular ratio, were fully analyzed to evaluate macroscopic characteristics of the whole spray and spray core with varying injection pressure. The results demonstrated that the effect of ultra-high injection pressure on macroscopic spray characteristics was significant. As injection pressure increased from 10 MPa to 50 MPa, the occurrence time of branch-like structure decreased; the cone angle increased little; the area increased significantly; the area ratio dropped by 6.4 and 5.8 percentage points on average for the front view and side view spray, respectively. There was a significant increase in the trend for penetration as the injection pressure rose from 10 MPa to 30 MPa. However, this trend became weak when the injection pressure further increased. The penetration ratio under ultra-high injection pressure was slightly higher than it was under 10 or 20 MPa. Ultra-high injection pressure would not obviously raise the possibility of spray/wall impingement, but led to the impingement quantity increasing to some extent. Increasing injection pressure could enhance the vortex scale, finally resulting in better air/fuel mixing quality. Ultra-high injection pressure was a potential way to improve air/fuel mixture homogeneity for a GDI injector fueled with ethanol.

Experimental Investigations of Cycle-to-Cycle and Cylinder-to-Cylinder Variation of PCCI Combustion With High Injection Pressures

2010 ◽  
Author(s):  
S. Juttu ◽  
S. S. Thipse ◽  
Praveen Mishra ◽  
N. B. Dhande ◽  
N. V. Marathe ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Heat Release ◽  
Injection Pressure ◽  
Combustion Mode ◽  
Operating Range ◽  
High Injection ◽  
Wide Range ◽  
Significant Difference ◽  
Low Load ◽  
Injection Pressures

Recently HCCI combustion concept has gained the attention of industry and academia due to its potential to reduce NOx and PM emissions simultaneously from diesel engines. The HCCI concept also called as Partially-Premixed Charge Compression Ignition (PCCI) when heavy fuel like diesel is used as fuel. To achieve homogeneous mixture of diesel+air+residual gases, high injection pressures are required with fine atomization. The cycle-to-cycle and cylinder-to-cylinder variations in rail pressure and EGR ratio caused to variations in engine performance. In this study combustion stabilities and cycle-to-cycle variations of diesel engine operated in PCCI combustion mode were investigated at different fuel injection pressures on a 4-cylinder, 4-stroke diesel engine. The experiments were conducted with 500bar, 1000bar, 1500bar and 1800bar injection pressures at low load (IMEP = 2bar) and 50% load (IMEP = 8.5bar) at 2500 and 3000 rpm. No EGR was used at low load condition and 50% EGR was used at 50% load at all injection pressures. In-cylinder pressures of 100 cycles were recorded for each test conditions running with PCCI mode. Consequently, cycle-to-cycle variations of the maximum Rate of Heat Release (ROHRmax), maximum Total Heat Release (THRmax), IMEP and Pmax were analyzed and evaluated using Coefficient of Variation (COV) of each parameter. The significant difference in COV from cylinder-to-cylinder was observed at higher injection pressures. With high injection pressures, wide range of cycle-to-cycle variations were observed in engines operated in PCCI combustion mode limiting the injection pressure and operating range of engine. The results show that the injection pressure need to be optimized with respect to load to control the PCCI combustion at constant EGR ratio to minimize the cycle-to-cycle variations and also extend the operating range of PCCI mode.

Experimental Study on Spray Characteristics of Diesel Engines and Analysis of Fuel Dripping Phenomenon

2014 ◽  
Vol 1078 ◽  
pp. 271-275 ◽  
Author(s):  
Yu Qiang Wu ◽  
Qian Wang ◽  
Zhi Sheng Gao ◽  
Zhou Rong Zhang ◽  
Li Ming Dai
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Cone Angle ◽  
Digital Camera ◽  
Injection Pressure ◽  
Fuel Mixture ◽  
Long Distance ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Spray Cone

Experimental study on macroscopic spray characteristics of a certain type of domestic common rail injectors under the conditions of different injection pressures was carried out through a high-speed digital camera. Furthermore, a fuel dripping phenomenon at the end stage of injection was observed through the high-speed digital camera equipped with a long-distance microscope, and a further analysis of the phenomenon was made. The results show the increase in the injection pressure can evidently enhance spray cone angle and expand the scope of spray field in combustion chamber, which is conducive to air-fuel mixture. The spray cone angle during the development spray shows a double-peak shape. And the long response-time of seating of solenoid valve core that disables the injection cutting off in time is one of factors causing fuel dripping phenomenon.

Modified Single-Fluid Cavitation Model for Pure Diesel and Biodiesel Fuels in Direct Injection Fuel Injectors

2012 ◽  
Author(s):  
Kaushik Saha ◽  
Ehab Abu-Ramadan ◽  
Xianguo Li
Keyword(s):  
Saturation Pressure ◽  
Injection Pressure ◽  
Wall Roughness ◽  
Cavitation Model ◽  
Fluid Mixture ◽  
Fuel Injectors ◽  
Cavitation Inception ◽  
High Injection ◽  
Biodiesel Fuels ◽  
Injection Pressures

A cavitation model has been developed for the internal two-phase flow of diesel and biodiesel fuels in fuel injectors under high injection pressure conditions. The model is based on the conventional single-fluid mixture approach with modification in the phase change rate expressions and local mean effective pressure, considering the effects of viscous stresses and turbulent pressure fluctuations, and also takes into account the effects of turbulence, compressibility and wall roughness. The model is validated by comparing the model predictions of probable cavitation regions, velocity distribution, fuel mass flow rate and pressure with the experimental measurement available in literature. It is found that cavitation inception for biodiesel occurs at a higher injection pressure, compared to diesel, due to its lower saturation pressure. However, supercavitation occurs for both diesel and biodiesel at high injection pressures. RNG k–ε model for turbulence modeling is reliable by comparing its performance with realizable k–ε and SST k–ω models. The effect of liquid phase compressibility becomes considerable for very high injection pressures. Wall roughness is not an important factor for cavitation in fuel injectors.

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.

Autoignition characteristics of diesel spray under different injection pressures and cold start strategy for compression ignition engines

2020 ◽  
pp. 146808742093460
Author(s):  
Ziming Yang ◽  
Fushui Liu ◽  
Yikai Li
Keyword(s):  
High Speed ◽  
Injection Pressure ◽  
Cold Start ◽  
Diesel Spray ◽  
High Speed Photography ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Application Range ◽  
Compression Ignition Engines ◽  
Injection Pressures

Poor cold start performance is one of the main factors restricting the application range of compression ignition engines. Stable flame generation in the cylinder is the prerequisite for the successful start of the engine. In order to explore ways to improve the cold start ability of the compression ignition engine, the ignition characteristics of diesel sprays at different injection pressures were studied in a constant volume combustion chamber. A high-speed photography technique was used to obtain the color images of the initial flames of diesel free sprays. And the yellow flame is introduced as the criterion for a successful flame generation. It was found that under moderate injection pressures, the reactant concentration and energy dissipation rate reached equilibrium. Under this condition, the duration of the blue flame is relatively stable, and it is most conducive to the generation of the yellow flame in the cylinder. The negative temperature coefficient phenomenon is also observed, and the temperature range in which this phenomenon occurs is identical with the change of injection pressure. A cold start strategy for the compression ignition engine is proposed by controlling the compression-end temperature in the cylinder to be higher than the threshold ignition temperature of diesel spray.

Injection Characteristics of Coal-Water Slurries in Medium-Speed Diesel Equipment

1992 ◽  
Vol 114 (3) ◽  
pp. 522-527 ◽  
Author(s):  
L. G. Dodge ◽  
T. J. Callahan ◽  
T. W. Ryan ◽  
J. A. Schwalb ◽  
C. E. Benson ◽  
...  
Keyword(s):  
Diesel Fuel ◽  
Cone Angle ◽  
Injection Pressure ◽  
Elevated Pressure ◽  
Injection System ◽  
Spray Characteristics ◽  
Minimal Impact ◽  
Jet Mixing ◽  
High Injection ◽  
Injection Pressures

The injection characteristics of several micronized coal-water slurries (CWSs, where “s” implies plural) were investigated at high injection pressures (40 to 140 MPa, or 6,000 to 20,000 psi). Detailed spray characteristics including drop-size distributions and cone angles were measured using a continuous, high-pressure injection system spraying through various hole shapes and sizes into a continuous, elevated-pressure air flow. Penetration and cone angle were also measured using intermittent injection into an elevated-pressure quiescent chamber. Cone angles and fuel-air mixing increased rapidly with the relatively constant cone angles of diesel fuel. However, even at high injection pressures the CWSs mixed with air more slowly than diesel fuel at the same pressure. The narrower CWS sprays penetrated more rapidly than diesel fuel at the same injection pressures. Increasing injection pressure dramatically reduced drop sizes in the CWS sprays, while increasing injection pressure reduced drop sizes in the diesel fuel sprays more gradually. The CWSs produced larger average drop sizes than the diesel fuel at all conditions, except for some hole shapes at the highest injection pressures where the average sizes were about the same. Varying the hole shape using converging and diverging holes had a minimal impact on the spray characteristics. A turbulent jet mixing model was used to predict the penetration rate of the CWS fuel jets through different orifice sizes and into different air densities. The jet model also computes the liquid fuel-air ratio through the jet. The work reported here was abstracted from the more complete report by Schwalb et al. (1991).

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