Influence of injector nozzle design and cavitation on coking phenomenon

Argueyrolles, B.; Dehoux, Stephan; Gastaldi, Patrick; Grosjean, Lysiane; Lévy, F.; Michel, Anne; Passerel, D.

doi:10.4271/2007-01-1896

Cited by 40 publications

(68 citation statements)

References 11 publications

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“…The deposits can also reduce the hydraulic diameter of the nozzle hole, resulting in a reduction in the quantity of injected fuel and reduced quality and consistency of injection [3][4][5]; all of which cause a reduction in engine power [6]. The deposits can also increase cavitation, which can then lead to further coking of the nozzle [7]. Injector needle sticking can occur and eventually injector failure [8,9].…”

Section: Introductionmentioning

confidence: 99%

A quantitative analysis of nozzle surface bound fuel for diesel injectors

Turner

Sykes

Sercey

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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In a fuel injector at the end of the injection, the needle descent and the rapid pressure drop in the nozzle leads to discharge of large, slow-moving liquid structures. This unwanted discharge is often referred as fuel 'dribble' and results in near-nozzle surface wetting, creating fuel-rich regions that are believed to contribute to unburnt hydrocarbon emissions. Subsequent fluid overspill occurs during the pressure drop in the expansion stroke when residual fluid inside the nozzle is displaced by the expansion of trapped gases as the pressure through the orifices is equalised, leading to further surface wetting. There have been several recent advancements in the characterisation of these near nozzle fluid processes, yet there is a lack of quantitative data relating the operating conditions and hardware parameters to the quantity of overspill and surface-bound fuel. In this study, methods for quantifying nozzle tip wetting after the end of injection were developed, to gain a better understanding of the underlying processes and to study the influence of engine operating conditions. A high-speed camera with a longdistance microscope was used to visualise fluid behaviour at the microscopic scale during, and after, the end of injection. In order to measure the nozzle tip temperature, a production injector was used which was instrumented with a type K thermocouple near one of the orifices. Image post-processing techniques were developed to track both the initial fuel coverage area on the nozzle surface, as well as the temporal evolution and spreading rate of surface-bound fluid. The conclusion presents an analysis of the area of fuel coverage and the rate of spreading and how these depend on injection pressure, in-cylinder pressure and in-cylinder temperature. It was observed that for this VCO injector, the rate of spreading correlates with the initial area of fuel coverage measured after the end of injection, suggesting that the main mechanism for nozzle wetting is through the impingement of dribble onto the nozzle. However, occasional observations of the expansion of orifice-trapped gas were made that lead to a significant increase in nozzle wetting. KeywordsDiesel; end of injection; dribble; surface wetting; image processing Introduction Increasingly strict emissions standards place considerable pressure on the automotive industry to increase the efficiency of, and reduce the emissions of the engine. This is primarily done by optimising the fuel-air mixing processes that occur inside the combustion chamber. Since the fuel air mixing is affected by the fuel injection equipment (FIE), much of the research efforts have been in improving the injector design and spray characteristics. This has resulted in the numbers of holes in the injector tip increasing with subsequent designs, as well as increases in the operating pressure, with typical systems operating with common rail pressures of over 200 MPa. These increasingly harsh conditions are believed to accelerate the formation and growth of deposits in and arou...

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Section: Introductionmentioning

confidence: 99%

A quantitative analysis of nozzle surface bound fuel for diesel injectors

Turner

Sykes

Sercey

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

View full text Add to dashboard Cite

show abstract

“…The high injection pressure is because of the better mixing achievable [27]. The different types of injectors with different geometries, produces different amount of losses in fuel flow rate based on these different injectors [29,30]. Different types of injectors have different pattern nozzle, the nozzle concept is that after the closing of the nozzle in high pressure part of the combustion process, the fuel is stored in the injector holes.…”

Section: Fuel Injection Pressure and Nozzle Characteristics Powermentioning

confidence: 99%

Modeling of Common Rail System and Constant Volume Chamber in Biodiesel Combustion: A Review

Ramsy

Khalid

Jaat

2015

AMM

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ABSTRACT. Among the challenges faced by diesel engines combustion nowadays are to reduce emission especially Nitrogen Oxide (NO x ) and Particular Matter (PM) while enhancing fuel efficiency and power. The purpose of this review is to explore the mixture formation of biodiesel combustion using constant volume chamber and optical visualization. This paper will review the development of a single-shot combustion system and constant volume chamber. An overview of the relation of mixture formation and combustion process in diesel combustion is provided first. This review has shown that the application of Rapid compression Machine (RCM) is used to simulate actual condition especially the injection pressure and air motion. The review also found that the mixing between fuel and air is unavoidable and very important during ignition delay period thus predominantly influences the exhaust emission. The detailed behaviour of injection characteristic that strongly effects the mixture formation especially the spray evaporation and spray interference are discussed.

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“…For example, deposits lead to an increase in air pollutant emissions [1, 2], a decrease in quality of injection [2,3,4] and further coking of the nozzle [5]. Understanding of the fuel dribbling process is particularly important for the development of a strategy for optimal use of fuels.…”

Section: Introductionmentioning

confidence: 99%

Quantification of diesel injector dribble using 3D reconstruction from x-ray and DBI imaging

Sechenyh

Turner

Sykes

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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Post-injection dribble is known to lead to incomplete atomisation and combustion due to the release of slow moving, and often surface-bound, liquid fuel after the end of the injection event. This can have a negative effect on engine emissions, performance, and injector durability. To better quantify this phenomenon we present a new image processing approach to quantify the volume and surface area of ligaments produced during the end of injection, for an ECN 'Spray B' 3-hole injector. Circular approximation for cross-sections was used to estimate three-dimensional parameters of droplets and ligaments. The image processing consisted in three stages: edge detection, morphological reconstruction, and 3D reconstruction. For the last stage of 3D reconstruction, smooth surfaces were obtained by computation of the alpha shape which represents a bounding volume enveloping a set of 3D points. The object model was verified by calculation of surface area and volume from 2D images of figures with well-known shapes. We show that the object model fits non-spherical droplets and pseudo-cylindrical ligaments reasonably well. We applied our processing approach to datasets generated by different research groups to decouple the effect of gas temperature and pressure on the fuel dribble process. High-speed X-ray phase-contrast images obtained at room temperature conditions (297 K) at the 7-ID beamline of the Advanced Photon Source at Argonne National Laboratory, together with diffused back-illumination (DBI) images captured at a wide range of temperature conditions (293-900 K) by CMT Motores Térmicos, were analysed and compared quantitatively. KeywordsDiesel injector; dribble; ligament; droplet shape; atomisation. IntroductionThe end-of-injection (EOI) fuel dribble causes a formation of unburned hydrocarbons and decreases the performance of internal combustion engines in a variety of ways. For example, deposits lead to an increase in air pollutant emissions [1, 2], a decrease in quality of injection [2,3,4] and further coking of the nozzle [5]. Understanding of the fuel dribbling process is particularly important for the development of a strategy for optimal use of fuels. However, observing the transient end-of-injection processes is particularly challenging due to the extreme operating conditions and the microscopic scales involved. Consequently, there is a lack of quantitative information on the fuel dribble events and the parameters that affect them. Recently published studies [6][7][8][9][10] demonstrate different aspects of the EOI fuel dribble based on a qualitative and quantitative analysis of experimental images of the injection process. The following important factors affecting the mechanism of the fuel dribble were studied: peak injection velocity [7], needle closing speed [7], in-cylinder pressure [6,7], injection pressure [6], fuel mass expulsion [9], bubble ingestion at the EOI [10], liquid length recession at the EOI [8] and different flow characteristics at the EOI [11]. The present study is dedicated to a qua...

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Influence of injector nozzle design and cavitation on coking phenomenon

Cited by 40 publications

References 11 publications

A quantitative analysis of nozzle surface bound fuel for diesel injectors

A quantitative analysis of nozzle surface bound fuel for diesel injectors

Modeling of Common Rail System and Constant Volume Chamber in Biodiesel Combustion: A Review

Quantification of diesel injector dribble using 3D reconstruction from x-ray and DBI imaging

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