Micro-hole Nozzle Research Articles

Effects of micro-hole nozzle and ultra-high injection pressure on air entrainment, liquid penetration, flame lift-off and soot formation of diesel spray flame

Increasing the injection pressure and downsizing the nozzle orifice diameter have been major measures for diesel engines to facilitate fuel–ambient gas mixture formation and combustion processes. The objective of this investigation is to carry out a quantitative analysis on the effects of micro-hole nozzle and ultra-high injection pressure on the mixing and combustion characteristics of diesel spray flame. Hence, laser-induced fluorescence and particle image velocimetry technique was employed to quantitatively access the gas entrainment of diesel spray emerging from nozzle with orifice diameter down to 80 µm under injection pressure up to 300 MPa, together with OH* chemiluminescence imaging and two-color pyrometry techniques to resolve the combustion and soot formation processes. Additionally, numerical simulation on the multi-phase flow inside injector nozzle was conducted to obtain information on internal flow dynamics. Experimental results show that over 80% of the ambient gas entrained into a spray pl...

Numerical research of diesel spray and atomization coupled cavitation by Large Eddy Simulation (LES) under high injection pressure

A special spray model is applied to study the spray behavior with high injection pressure and micro-hole nozzle. To reveal the cavitation in diesel nozzle and its influence on spray and atomization, the Large Eddy Simulation (LES) turbulence model is adopted to detect the cavitation, and then the special spray model coupling the cavitation is build. From research results, three important conclusions can be drawn. Firstly, the cavitation flow can raise the effective velocity at the nozzle exit and such effect become even more obvious with higher injection pressure, e.g.180MPa. Secondly, the applied spray model is in good agreement with the spray characteristics and images obtained from the EFS8400 spray test platform. Thirdly, the cavitation with high injection pressure and micro-hole nozzle can increase the spray cone angle and reduce the spray penetration; the cavitation intensity has a great impact on the spray velocity field and vorticity intensity, especially at the initial spray field under the condition of high injection pressure.

SP3-1 Spray, Ignition and Combustion Characteristics of Biodiesel and Diesel Fuels Injected by Micro-Hole Nozzle under Ultra-High Injection Pressure(SP: Spray and Spray Combustion,General Session Papers)

SP3-1 Spray, Ignition and Combustion Characteristics of Biodiesel and Diesel Fuels Injected by Micro-Hole Nozzle under Ultra-High Injection Pressure(SP: Spray and Spray Combustion,General Session Papers)

QUANTITATIVE ANALYSES OF FUEL SPRAY-AMBIENT GAS INTERACTION BY MEANS OF LIF-PIV TECHNIQUE

The in-cylinder fuel-ambient gas mixing property in a direct injection (D.I.) diesel engine significantly influences the ensuing combustion and exhaust emission performance. In this study, the interaction of nonevaporating diesel spray with the surrounding gas was analyzed quantitatively in the quiescent condition at room temperature and with ambient gas pressure of 1 MPa by means of the laser induced fluorescence-particle image velocimetry (LIF-PIV) technique. Particularly, this study focused on the calculation of gas mass flow rate entrained through the entire spray region (spray side periphery and tip region) and total entrained gas-fuel ratio by using the gas velocity data obtained by the LIF-PIV technique. Another focus of this study was the gas entrainment characteristics of diesel spray under a wide range of injection pressures (100, 200, and 300 MPa) and the micro-hole nozzle (0.08mm) condition. The results indicate that the entrained gas mass flow rate at the spray tip region is prominent in the whole periphery and the proportion of gas entrainment at the side surface region increases as the spray develops Higher injection pressure significantly enhances the total entrained gas mass; however the increase of ambient gas/fuel mass ratio becomes moderate gradually as the injection pressure increases. The calculation model proposed by this work is capable of illustrating the ambient gas flow characteristics of the diesel spray accurately.

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

The effects of ultra-high injection pressure ( P inj = 300 MPa) and micro-hole nozzle ( d = 0.08 mm) on flame structure and soot formation of impinging diesel spray were studied with a high speed video camera in a constant volume combustion vessel. Two-color pyrometry was used to measure the line-of-sight soot temperature and concentration with two wavelengths of 650 and 800 nm. A flat wall vertical to the injector axis is located 30 mm away from the injector nozzle tip to generate impinging spray flame. Three injection pressures of 100, 200 and 300 MPa and two injector nozzles with diameters of 0.16 and 0.08 mm were used. With the conventional injector nozzle (0.16 mm), ultra-high injection pressure generates appreciably lower soot formation. With the micro-hole nozzle (0.08 mm), impinging spray flame shows much smaller size and lower soot formation at the injection pressure of 100 MPa. The soot formation is too weak to be detected with the micro-hole nozzle at injection pressures of 200 and 300 MPa. With eliminating the impact of injection rate on soot level, both ultra-high injection pressure and micro-hole nozzle have an obvious effect on soot reduction. Soot formation characteristics of impinging spray flame were compared with those of free spray flame using both the conventional and micro-hole nozzles. With the conventional nozzle, flat wall impingement deteriorates soot formation significantly. While soot formation characteristics of free spray flame with the micro-hole nozzle are not altered obviously by flat wall. Liquid length of the 0.16 mm nozzle is longer than the impingement distance and liquid length of the 0.08 mm nozzle is shorter than the impingement distance . Liquid impingement upon the wall is responsible for the deteriorated soot level of impinging flame compared to that of free flame with the conventional nozzle.

J0801-1-2 スプリット噴射による二元燃料ディーゼル機関の燃焼改善に関する研究([J0801-1]エンジン,動力システムにおける燃焼技術(1))

The purpose of this study is to realize high-efficient dual fuel combustion with natural gas and diesel fuel. Diesel fuel was injected directly into combustion chamber of a single cylinder diesel engine. And diesel fuel was injected through micro-hole nozzle with a common rail system. The natural gas was injected at an intake port as premixed gas. In order to distribute diesel fuel spray in combustion chamber, one diesel injection event was split into twice ones, where diesel fuel was injected earlier than usual and around TDC. In this study exhaust emissions and heat release characteristics were investigated. The result show that a timing and an amount of 1^<st> injection significantly influence on unburned emissions and thermal efficiency. And it seems that precise control of diesel fuel distribution has a great importance to combustion performance of natural gas with diesel fuel.

An experimental study on flat-wall-impinging spray of microhole nozzles under ultra-high injection pressures

The objective of the study is to provide information on the spray and mixture formation process of the microhole nozzle ( d=0.08mm) under an ultra-high injection pressure ( Pinj=300MPa). Flat-wall-impinging sprays were focused on and the laser absorption-scattering technique was adopted to obtain qualitative and quantitative information under various conditions. The spray and mixture characteristics of the conventional nozzle and microhole nozzles were compared; the advantages and disadvantages of microhole nozzles under different conditions were also discussed. Spray tip penetration length data were collected and compared with the predicted values using the gas jet theory. The results showed that the combination of the microhole nozzle and ultra-high injection pressure was very effective for obtaining the optimal penetration length, fast vaporization, and a high air entrainment rate.

1716 希薄・均一なディーゼル噴霧の着火および燃焼に及ぼす燃料組成の影響

In order to make clear the effects of fuel properties on the ignition of the homogeneous and dilute diesel fuel spray made by hi-pressure injection and micro-hole nozzle, mixed fuel with n-Decane (Cetane Number : 78.8) and α-Metylnaphthalene (Cetane Number : 0) were used in this study. These mixed fuel had different Cetane Numbers but made to have same n-Decane partial equivalence ratio in fuel spray (φnD) by using different hole-diameter nozzle. The ignition delay under the condition that ignition occurred during fuel injection period (diffusion condition) depended on nozzle diameter. On the other hands in the case that ignition (premix condition) occurred after injection ignition delay depended on φnD. The combustion efficiency is also affected by φnD in the premix condition.

Performance and Exhaust Emission in a Premixed Compression Ignition Engine with High Pressure Fuel Injection Near a Top Dead Center.

Premixed lean diesel combustion was performed in a condition that a fuel injection timing was near top dead center. To promote fuel-air mixing a micro-hole nozzle (nozzle hole diameter is 0.08 mm) and high pressure injection (up to 250 MPa) were used. Low cetane number fuel was used for main injector mounted at the bore center to make ignition delay. Small quantity of high cetane number fuel was supplied from two side injectors to control the ignition timing. As a result, low NOx combustion was realized in an operating codition when the ignition started after several crank angles from injection end. Important factor to realize this combustion is to complete the fuel injection and vaporization before ignition.

Study on Ignition Delay and Combustion of Diesel Spray with High Pressure Fuel Injection and a Micro-Hole Nozzle Using a Rapid Compression Machine. Consideration of Non-Uniformity of Equivalence Ratio inside a Spray.

Study on Ignition Delay and Combustion of Diesel Spray with High Pressure Fuel Injection and a Micro-Hole Nozzle Using a Rapid Compression Machine. Consideration of Non-Uniformity of Equivalence Ratio inside a Spray.

Improvement of Combustion in a Direct Injection Diesel Engine by Micro-Hole Nozzle.

In an attempt to promote the atomization of fuel spray and the mixing of fuel and air in diesel engines, a micro-hole nozzle which has orifices with a diameter smaller than 0.10 mm was developed. In this study, the combustion tests were carried out using a single cylinder diesel engine equipped with a micro-hole nozzle and a common rail type high-pressure fuel injection system. A comparison with the results of a conventional nozzle experiment showed that the peak of initial premixed combustion increased, but the peak of diffusion combustion decreased. As a result, when nozzle orifice diameter become small from φ0.15 mm to φ0.10 mm, the combustion was accompanied by smokeless with the same levels of NOx emission and fuel economy. And results of a comparison the toroidal type chamber with the shallow dish type chamber revealed that the optimization of combustion chamber is necessary for the increase of the injection stage with increasing of the number of nozzle orifice. If an orifice diameter becomes φ0.06 mm, the diffusion combustion can not be observed and the combustion is formed of only premixed combustion. The combustion in the case of φ0.06 mm was accompanied with the drastic deterioration of fuel economy, smoke and HC with all over load. But the micro-hole nozzle has a potential for the formation of the lean and homogeneous premixed mixture until the fuel-air mixture ignites.

Study on Premixed Combustion of Diesel Spray with High Pressure Fuel Injection and a Micro-Hole Nozzle Using a Rapid Compression Machine. 2nd Report, Improvement of Combustion Using Low Cetane Number Fuel.

This study was aimed at reducing Soot and NOx by uniform and lean distribution of fuel in diesel spray using high-pressure fuel injection and a micro-hole nozzle. But this injection system made ignition delay shorter. So that, it couldn't completely make uniform and lean distribution of fuel in diesel spray. Then, in addition to this injection system, using low cetane number of fuel, which can not easily ignited, we made ignition delay longer, and attempted to make complete uniform and lean distribution of fuel in diesel spray. The combustion event was observed by high-speed direct photography, ignition and combustion was analyzed by the combustion chamber pressure history, and KL values and flame temperatures was analyzed by the two-color method from the two dimensional flame image.

Study of diesel spray combustion and ignition using high-pressure fuel injection and a micro-hole nozzle with a rapid compression machine: improvement of combustion using low cetane number fuel

This study aimed to reduce NO x and soot by creating a more homogeneous lean fuel distribution in a diesel spray using high-pressure fuel injection and a micro-hole nozzle. This injection system shortened the ignition delay, but a homogeneous lean fuel distribution in the diesel spray was not achieved. Using a lower cetane number fuel, the resulting longer ignition delay made a uniform, lean fuel distribution in the diesel spray possible with this injection system. Ignition and combustion were analyzed by the combustion chamber pressure history, and flame temperatures and KL values were analyzed by the two-color method.

Study on Premixed Combustion of Diesel Spray with High-Pressure Fuel Injection and a Micro-Hole Nozzle Using a Rapid Compression Machine. Improvement of Combustion Using Low Cetane Number Fuel.

This study aimed to reduce NO and soot by establishing fuel lean and uniform mixture in diesel spray using high-pressure fuel injection and a micro-hole nozzle. To avoid short ignition delay by micro-hole nozzle and high pressure fuel injection, low cetane number fuel was induced to shift the ignition timing after the end of fuel injection. The combustion event was observed by high-speed direct photography, ignition and combustion were analyzed by the combustion chamber pressure history, and KL values and flame temperatures were analyzed by the two color method from the two dimensional flame image.

Ignition, Combustion and Emissions in a DI Diesel Engine Equipped with a Micro-hole Nozzle.

Ignition, Combustion and Emissions in a DI Diesel Engine Equipped with a Micro-hole Nozzle.