Visual analyses of end of injection liquid structures and the behaviour of nozzle surface-bound fuel in a direct injection diesel engine

Dan Sykes, Guillaume de Sercey, Martin Gold, Richard Pearson, Cyril Crua

Research output: Chapter in Book/Conference proceeding with ISSN or ISBNConference contribution with ISSN or ISBNResearchpeer-review

Abstract

Multiple injection strategies are implemented in the majority of modern diesel engines, increasing the frequency of transient injection phases and thus, end of injection (EOI) events. Recent advances in diagnostic techniques have identified several EOI phenomena pertinent to nozzle surface wetting as a precursor for deposit formation and a potentially contribution to unburnt hydrocarbon emissions. To investigate the underlying processes, high-speed optical measurements at the microscopic scale were performed inside an idling diesel engine. Visualisation of the injector nozzle surface and near nozzle region permitted an in-depth analysis of the post-injection phenomena and the behaviour of fuel films on the nozzle surface. Inspection of the high-speed video data enabled an interpretation of the fluid dynamics leading to surface wetting, elucidating the mechanisms of deposition and spreading. As the needle re-seats, the abrupt pressure drop inhibited atomisation, with large, slow moving, liquid structures released into the cylinder with the capability of impinging on nearby surfaces, creating localised fuel rich regions, or escaping through the exhaust, contributing towards un-burnt hydrocarbon emissions. Large ligaments remained attached to the nozzle, subsequently splitting and retracting back onto the surface. The inertia of the fuel leaving the orifices is known to induce rarefaction within the nozzle, equalised through the ingestion of in-cylinder gas and surface-bound fuel. The EOI event was succeeded by further surface wetting due to the expansion of orifice-trapped gas dislodging nozzle-residing fuel and causing it to overspill onto the external surface. The drop in in-cylinder pressure elicited bubbling within the surface-bound fuel, further increasing the film’s spreading rate. The resulting film bubble agglomerations collapsed in large chain reactions, projecting more fuel into the cylinder. Large quantities of projected fuel were visibly drawn towards the exhaust valves, potentially contributing to un-burnt hydrocarbon emissions.
Original languageEnglish
Title of host publicationInternational Powertrains, Fuels & Lubricants Meeting
Place of PublicationUnited States
PublisherSAE International
Volume2019-January
EditionJanuary
DOIs
Publication statusPublished - 15 Jan 2019
EventSAE International Powertrains, Fuels and Lubricants Meeting - Rio de Janeiro, Brazil
Duration: 5 May 2010 → …

Publication series

NameSAE Technical Papers

Conference

ConferenceSAE International Powertrains, Fuels and Lubricants Meeting
Period5/05/10 → …

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Direct injection
Diesel engines
Nozzles
Liquids
Engine cylinders
Wetting
Hydrocarbons
Orifices
Gas cylinders
Ligaments
Atomization
Seats
Fluid dynamics
Needles
Pressure drop
Deposits
Agglomeration
Visualization
Inspection

Cite this

Sykes, D., de Sercey, G., Gold, M., Pearson, R., & Crua, C. (2019). Visual analyses of end of injection liquid structures and the behaviour of nozzle surface-bound fuel in a direct injection diesel engine. In International Powertrains, Fuels & Lubricants Meeting (January ed., Vol. 2019-January). (SAE Technical Papers). United States: SAE International. https://doi.org/10.4271/2019-01-0059
Sykes, Dan ; de Sercey, Guillaume ; Gold, Martin ; Pearson, Richard ; Crua, Cyril. / Visual analyses of end of injection liquid structures and the behaviour of nozzle surface-bound fuel in a direct injection diesel engine. International Powertrains, Fuels & Lubricants Meeting. Vol. 2019-January January. ed. United States : SAE International, 2019. (SAE Technical Papers).
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abstract = "Multiple injection strategies are implemented in the majority of modern diesel engines, increasing the frequency of transient injection phases and thus, end of injection (EOI) events. Recent advances in diagnostic techniques have identified several EOI phenomena pertinent to nozzle surface wetting as a precursor for deposit formation and a potentially contribution to unburnt hydrocarbon emissions. To investigate the underlying processes, high-speed optical measurements at the microscopic scale were performed inside an idling diesel engine. Visualisation of the injector nozzle surface and near nozzle region permitted an in-depth analysis of the post-injection phenomena and the behaviour of fuel films on the nozzle surface. Inspection of the high-speed video data enabled an interpretation of the fluid dynamics leading to surface wetting, elucidating the mechanisms of deposition and spreading. As the needle re-seats, the abrupt pressure drop inhibited atomisation, with large, slow moving, liquid structures released into the cylinder with the capability of impinging on nearby surfaces, creating localised fuel rich regions, or escaping through the exhaust, contributing towards un-burnt hydrocarbon emissions. Large ligaments remained attached to the nozzle, subsequently splitting and retracting back onto the surface. The inertia of the fuel leaving the orifices is known to induce rarefaction within the nozzle, equalised through the ingestion of in-cylinder gas and surface-bound fuel. The EOI event was succeeded by further surface wetting due to the expansion of orifice-trapped gas dislodging nozzle-residing fuel and causing it to overspill onto the external surface. The drop in in-cylinder pressure elicited bubbling within the surface-bound fuel, further increasing the film’s spreading rate. The resulting film bubble agglomerations collapsed in large chain reactions, projecting more fuel into the cylinder. Large quantities of projected fuel were visibly drawn towards the exhaust valves, potentially contributing to un-burnt hydrocarbon emissions.",
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Sykes, D, de Sercey, G, Gold, M, Pearson, R & Crua, C 2019, Visual analyses of end of injection liquid structures and the behaviour of nozzle surface-bound fuel in a direct injection diesel engine. in International Powertrains, Fuels & Lubricants Meeting. January edn, vol. 2019-January, SAE Technical Papers, SAE International, United States, SAE International Powertrains, Fuels and Lubricants Meeting, 5/05/10. https://doi.org/10.4271/2019-01-0059

Visual analyses of end of injection liquid structures and the behaviour of nozzle surface-bound fuel in a direct injection diesel engine. / Sykes, Dan; de Sercey, Guillaume; Gold, Martin; Pearson, Richard; Crua, Cyril.

International Powertrains, Fuels & Lubricants Meeting. Vol. 2019-January January. ed. United States : SAE International, 2019. (SAE Technical Papers).

Research output: Chapter in Book/Conference proceeding with ISSN or ISBNConference contribution with ISSN or ISBNResearchpeer-review

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AU - de Sercey, Guillaume

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AU - Pearson, Richard

AU - Crua, Cyril

PY - 2019/1/15

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AB - Multiple injection strategies are implemented in the majority of modern diesel engines, increasing the frequency of transient injection phases and thus, end of injection (EOI) events. Recent advances in diagnostic techniques have identified several EOI phenomena pertinent to nozzle surface wetting as a precursor for deposit formation and a potentially contribution to unburnt hydrocarbon emissions. To investigate the underlying processes, high-speed optical measurements at the microscopic scale were performed inside an idling diesel engine. Visualisation of the injector nozzle surface and near nozzle region permitted an in-depth analysis of the post-injection phenomena and the behaviour of fuel films on the nozzle surface. Inspection of the high-speed video data enabled an interpretation of the fluid dynamics leading to surface wetting, elucidating the mechanisms of deposition and spreading. As the needle re-seats, the abrupt pressure drop inhibited atomisation, with large, slow moving, liquid structures released into the cylinder with the capability of impinging on nearby surfaces, creating localised fuel rich regions, or escaping through the exhaust, contributing towards un-burnt hydrocarbon emissions. Large ligaments remained attached to the nozzle, subsequently splitting and retracting back onto the surface. The inertia of the fuel leaving the orifices is known to induce rarefaction within the nozzle, equalised through the ingestion of in-cylinder gas and surface-bound fuel. The EOI event was succeeded by further surface wetting due to the expansion of orifice-trapped gas dislodging nozzle-residing fuel and causing it to overspill onto the external surface. The drop in in-cylinder pressure elicited bubbling within the surface-bound fuel, further increasing the film’s spreading rate. The resulting film bubble agglomerations collapsed in large chain reactions, projecting more fuel into the cylinder. Large quantities of projected fuel were visibly drawn towards the exhaust valves, potentially contributing to un-burnt hydrocarbon emissions.

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Sykes D, de Sercey G, Gold M, Pearson R, Crua C. Visual analyses of end of injection liquid structures and the behaviour of nozzle surface-bound fuel in a direct injection diesel engine. In International Powertrains, Fuels & Lubricants Meeting. January ed. Vol. 2019-January. United States: SAE International. 2019. (SAE Technical Papers). https://doi.org/10.4271/2019-01-0059