Effects of nozzle geometries and needle lift on steadier string cavitation and larger spray angle in common rail diesel injector

2020 ◽  
pp. 146808742093649
Author(s):  
Zhixia He ◽  
Han Zhou ◽  
Lian Duan ◽  
Min Xu ◽  
Zhou Chen ◽  
...  
Keyword(s):  
Fuel Injection ◽  
Cone Angle ◽  
Common Rail ◽  
Spray Angle ◽  
Injection System ◽  
Three Dimension ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Hole Position ◽  
Nozzle Hole

The cavitating flow in diesel injector nozzles plays a vital role in spray atomization and formation of fuel–air mixture, since vortex-induced string cavitation has recently been found a much more influence on spray compared to the ordinary geometry-induced film cavitation. In this study, in order to investigating string cavitation and its’ enhancement on spray, the visualization experimental platform for the real-size optical tapered-hole nozzle was built based on the high-pressure common rail fuel injection system. Groups of optical nozzles with different geometries were designed for exploring the couple effects of several nozzle geometric parameters, including nozzle sac chamber depth, nozzle-hole position height and needle lift, on the three-dimension vortex flow structure and then on the string cavitation and spray characteristics. Results indicated that the string cavitation characteristics are tightly associated with couple characteristics of the parameters. The stable and strong string cavitation during the whole injection process can be obtained in the Min-sac nozzle with the high hole position under the low needle lift. The string cavitation extends to the nozzle-hole outlet, and subsequently induces the special hollow cone spray with air in the spray center location and corresponding a larger spray cone angle even under not so high injection pressure.

scholarly journals Research on the internal flow and macroscopic characteristics of a diesel fuel injection process

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0255874
Author(s):  
Hua Xia
Keyword(s):  
Fuel Injection ◽  
Cone Angle ◽  
Injection Pressure ◽  
Internal Flow ◽  
Spray Angle ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Injection Process ◽  
Wide Range ◽  
Diesel Fuel Injection

The internal flow and macroscopic spray behaviors of a fuel injection process were studied with schlieren spray techniques and simulations. The injection pressures(Pin)and ambient pressures(Pout)were applied in a wide range. The results showed that increasing the Pin is likely to decrease the flow performance of the nozzle. Furthermore, increasing the Pin can increase the spray tip penetration. However, the effect of Pin on the spray cone angle was not evident. The spray cone angle at an injection pressure of 160MPa was 21.7% greater than at a pressure of 100MPa during the initial spraying stage. Additionally, the discharge coefficient increased under high Pout, and the decrease in Pout can promote the formation of cavitation. Finally, increasing the Pout can decrease the penetration, while the spray angle becomes wider, especially at the initial spray stage, and high Pout will enhance the interaction of the spray and the air, which can enhance the spray quality.

Experimental study of the effect of n-butanol additive on spray characteristics of biodiesel in a high-pressure common-rail injection system

2018 ◽  
Vol 233 (2) ◽  
pp. 211-220 ◽  
Author(s):  
Bolun Yi ◽  
Wei Fu ◽  
Lanbo Song ◽  
Fengyu Li ◽  
Tao Liu ◽  
...  
Keyword(s):  
High Speed ◽  
Cone Angle ◽  
Density Ratio ◽  
Common Rail ◽  
Injection System ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Spray Tip Penetration ◽  
Blended Fuel

The aim of this study was to investigate the spray characteristics of biodiesel and n-butanol/biodiesel blended fuel. The spray tip penetration and the spray cone angle were tested and analyzed. A constant volume chamber and high-speed camera were used to observe the spray evolution and a common-rail system was employed to change the injection pressure. The results show that the spray tip penetration and the spray cone angle of biodiesel are larger than those of blended fuel in most cases. n-Butanol additive changes the relationship between angle and density ratio to a certain degree. The experimental trend lines support the penetration model proposed by Hiroyasu and Arai in terms of similar proportional relation on time after start of injection, and the empirical equations provide reasonable agreement with the experimental data of the spray tip penetration.

Investigation of the Influence of Injection Rate Shaping on the Spray Characteristics in a Diesel Common Rail System Equipped with a Piston Amplifier

2005 ◽  
Vol 127 (6) ◽  
pp. 1102-1110 ◽  
Author(s):  
J. Benajes ◽  
R. Payri ◽  
S. Molina ◽  
V. Soare
Keyword(s):  
Cone Angle ◽  
Injection Pressure ◽  
Injection Rate ◽  
Common Rail ◽  
Injection System ◽  
Common Rail System ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Common Rail Injection System ◽  
Common Rail Injection

The quality of the mixing process of fuel and air in a direct injection diesel engine relies heavily on the way the spray develops when injected into the combustion chamber. Among other factors, the spray development depends on the injection rate of the fuel delivered by the injector. The paper presents a study, at both a macroscopic and microscopic level, of a Diesel spray generated by a common-rail injection system featuring a piston pressure amplifier. By modifying the timing and the duration of the injector and amplifier piston actuation, it is possible to obtain high injection pressures up to 180MPa, and different shapes for the injection rate, which would not be achievable with a regular common rail injection system. The spray evolution produced by three different injection rate shapes (square, ramp, and boot) has been investigated in an injection test rig, by means of visualization and PDPA techniques, at different injection conditions. The main conclusions are the important effect on spray penetration of the initial injection rate evolution and the small influence of the maximum injection pressure attained at the end of the injection event. Smaller or even negligible effects have been found on the spray cone angle and on the droplet Sauter mean diameter.

Experimental and Numerical Studies of Diesel Spray Evaporation and Combustion in a Gas Turbine Matrix Burner

2009 ◽  
Author(s):  
Dieter Bohn ◽  
James F. Willie ◽  
Nils Ohlendorf
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Combustion Instability ◽  
Cone Angle ◽  
Spray Angle ◽  
Test Rig ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Flow Simulations ◽  
Air Inlet

Lean gas turbine combustion instability and control is currently a subject of interest for many researchers. The motivation for running gas turbines lean is to reduce NOx emissions. For this reason gas turbine combustors are being design using the Lean Premixed Prevaporized (LPP) concept. In this concept, the liquid fuel must first be atomized, vaporized and thoroughly premixed with the oxidizer before it enters the combustion chamber. One problem that is associated with running gas turbines lean and premixed is that they are prone to combustion instability. The matrix burner test rig at the Institute of Steam and Gas Turbines at the RWTH Aachen University is no exception. This matrix burner is suitable for simulating the conditions prevailing in stationary gas turbines. Till now this burner could handle only gaseous fuel injection. It is important for gas turbines in operation to be able to handle both gaseous and liquid fuels though. This paper reports the modification of this test rig in order for it to be able to handle both gaseous and liquid primary fuels. Many design issues like the number and position of injectors, the spray angle, nozzle type, droplet size distribution, etc. were considered. Starting with the determination of the spray cone angle from measurements, CFD was used in the initial design to determine the optimum position and number of injectors from cold flow simulations. This was followed by hot flow simulations to determine the dynamic behavior of the flame first without any forcing at the air inlet and with forcing at the air inlet. The effect of the forcing on the atomization is determined and discussed.

Impacts of duct inner diameter and standoff distance on macroscopic spray characteristics of ducted fuel injection under non-vaporizing conditions

2020 ◽  
pp. 146808742091471
Author(s):  
Feng Li ◽  
Chia-fon Lee ◽  
Ziman Wang ◽  
Yiqiang Pei ◽  
Guoxiang Lu
Keyword(s):  
Large Scale ◽  
Fuel Injection ◽  
Soot Formation ◽  
Cone Angle ◽  
Mie Scattering ◽  
Standoff Distance ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Inner Diameter

Ducted fuel injection spray is a new technology for reducing soot formation in heavy-duty diesel engines. In this work, the ducted fuel injection spray characteristics with different duct inner diameters and different standoff distances were investigated and compared with free spray. Duct inner diameter ranged from 1.5 to 4 mm, and standoff distance varied between 0.9 and 4.9 mm. Mie-scattering optical technique was used to characterize spray characteristics under various injection pressures in a constant-volume spray chamber. Ambient gas pressure of up to 6 MPa when spraying. The results showed that ducted fuel injection spray with smaller duct has better spray diffusion compared to those of ducted fuel injection sprays with larger ducts and free spray from the perspectives of spray tip penetration, spray cone angle and spray area. Increasing standoff distance could increase spray velocity. Ducted fuel injection spray with smaller duct formed a mushroom-shaped head and large-scale vortex flow close to the duct outlet. All the advantages of ducted fuel injection spray with smaller duct are interpreted as evidence of improving fuel–gas mixing quality significantly.

Influence of Ambient Air Pressure on Pressure-Swirl Atomization

1987 ◽  
Author(s):  
X. F. Wang ◽  
A. H. Lefebvre
Keyword(s):  
Drop Size ◽  
Cone Angle ◽  
Ambient Air ◽  
Air Pressure ◽  
Spray Angle ◽  
Flow Number ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Continuous Increase ◽  
Pressure Swirl

The spray characteristics of six simplex atomizers are examined in a pressure vessel using a standard light diffraction technique. Attention is focused on the effects of liquid properties, nozzle flow number, spray cone angle, and ambient air pressure on mean drop size and drop-size distribution. For all nozzles and all liquids it is found that continuous increase in air pressure above the normal atmospheric value causes the SMD to first increase up to a maximum value and then decline. An explanation for this characteristic is provided in terms of the measurement technique employed and the various competing influences on the overall atomization process. The basic effect of an increase in air pressure is to improve atomization, but this trend is opposed by contraction of the spray angle which reduces the relative velocity between the drops and the surrounding air, and also increases the possibility of droplet coalescence.

Experimental study of spray characteristics of biodiesel blending with diethyl carbonate in a common rail injection system

2017 ◽  
Vol 233 (2) ◽  
pp. 249-262 ◽  
Author(s):  
Wei Fu ◽  
Lanbo Song ◽  
Tao Liu ◽  
Qizhao Lin
Keyword(s):  
Cone Angle ◽  
Injection Pressure ◽  
Injection System ◽  
Diethyl Carbonate ◽  
Spray Characteristics ◽  
Projected Area ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Common Rail Injection System ◽  
Common Rail Injection

The objective of this paper is to investigate the spray macroscopic characteristics of biodiesel, diethyl carbonate (DEC)-biodiesel blends and diesel fuel based on a common-rail injection system. The spray tip penetration, spray cone angle and the spray projected area were measured through a high-speed photography method. The experimental results reveal that injection pressure and ambient pressure have significant effects on the spray characteristics. Higher injection pressure makes the spray tip penetration increase, while higher back pressure inside the chamber leads to the enlargement of the spray cone angle. The addition of DEC causes the blends fuels to have a shorter penetration and larger spray projected area, which reveals the potential capacity to improve the atomization process compared with biodiesel. The estimation of spray droplet size indicates that DEC30 generates a smaller Sauter mean diameter (SMD) because of its lower surface tension and viscosity. Model predictions were illustrated and compared with current work.

Effect of Injection Rate Shaping Over Diesel Spray Development in Non Reacting Evaporative Conditions

2012 ◽  
Author(s):  
Raul Payri ◽  
Jaime Gimeno ◽  
Michele Bardi ◽  
Alejandro Plazas
Keyword(s):  
Fuel Injection ◽  
Cone Angle ◽  
Injection Rate ◽  
Effective Diameter ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Test Conditions ◽  
Needle Position ◽  
Rate Shaping ◽  
Wide Range

A prototype Diesel common rail direct-acting piezoelectric injector has been used to study the influence of fuel injection rate shaping on spray behavior (liquid phase penetration) under evaporative and non-reacting conditions. This state of the art injector allows a fully flexible control of the nozzle needle, enabling various fuel injection rates typologies under a wide range of test conditions. The tests have been performed employing a novel continuous flow test chamber that allows an accurate control on a wide range of thermodynamic test conditions (up to 1000 K and 15 MPa). The temporal evolution of the spray has been studied recording movies of the injection event with a fast camera (25 kfps) by means of the Mie scattering visualization technique. The analysis of the results showed a strong influence of needle position on the behavior of the liquid length. The needle position controls the effective pressure upstream of the nozzle holes. Higher needle lift is equivalent to higher effective pressures. According to the free-jet theory, the stabilized liquid-length depends mainly on effective diameter, spray cone-angle and fuel/air properties and does not depend on injection velocity. Therefore, higher injection pressures gives slightly lower liquid length due to small change in the spray cone-angle. However, partial needle lifts has an opposite effect: lower effective pressure upstream of the nozzle holes shows a dramatic increase on the spray cone-angle, reducing the liquid length. This behavior could be explained mainly due to the fact that the flow direction upstream of the nozzle holes is affecting the area coefficient, or in other words, the effective diameter of the holes.

Effect of Various Injection Pressures on Spray Characteristics of Karanja Oil Methyl Ester (KOME) and Diesel in a DI Diesel Engine

2015 ◽  
Vol 787 ◽  
pp. 815-819
Author(s):  
Vaibhav Prakash ◽  
B. Praveen Ramanujam ◽  
C. Sanjeev Nivedan ◽  
N. Nallusamy ◽  
P. Raghu
Keyword(s):  
Methyl Ester ◽  
Fuel Injection ◽  
Cone Angle ◽  
Injection Pressure ◽  
Spray Cone Angle ◽  
Penetration Length ◽  
Spray Cone ◽  
Di Diesel Engine ◽  
Fuel Injection Pressure ◽  
Karanja Oil

The performance and emissions from diesel engines are greatly influenced by the degree of atomization of the fuel spray. The characteristics of the spray affect the physics of formation of the air-fuel mixture. They depend on density and viscosity of fuel, injection pressure, pressure and temperature of fuel. The spray structure is primarily dependent on the fuel injection pressure. This study involves the carrying out of experimental investigations on biodiesel and diesel fuel sprays in a DI diesel engine for different injection pressures. The spray cone angle and spray tip penetration length are studied experimentally. Using spray visualization system and image processing techniques, the experimental data is obtained. The fuels used are Karanja oil methyl ester (KOME) and diesel. The experimental results show that, as the injection pressure increases, the spray cone angle decreases for KOME and similar trends are observed with diesel. In addition, spray penetration length increases with increase in injection pressure and the value of the same was slightly higher for KOME than that of diesel. The results also reveal similarities in spray characteristics of both the test fuels.

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