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Experimental and modeling study of liquid fuel injection and combustion in diesel engines with a common rail injection system

Xu, Leilei LU ; Bai, Xue Song LU ; Jia, Ming; Qian, Yong; Qiao, Xinqi and Lu, Xingcai (2018) In Applied Energy 230. p.287-304
Abstract

Fuel injection is one of the most important processes in compression-ignition internal combustion engines owing to its significant impact on the exhaust emissions and thermal efficiency. In this study, experiments were carried out to investigate the influence of injection pressure and injection timing on the temporal evolution of the injection rate and injection duration in a specially designed experiment rig equipped with a common rail injection system. It is well known that the injection signal from the electronic control unit (ECU) of the injection system, which is often the only injection information available in engine operation and experiments, gives little information about the actual injection rate profile. It is shown in the... (More)

Fuel injection is one of the most important processes in compression-ignition internal combustion engines owing to its significant impact on the exhaust emissions and thermal efficiency. In this study, experiments were carried out to investigate the influence of injection pressure and injection timing on the temporal evolution of the injection rate and injection duration in a specially designed experiment rig equipped with a common rail injection system. It is well known that the injection signal from the electronic control unit (ECU) of the injection system, which is often the only injection information available in engine operation and experiments, gives little information about the actual injection rate profile. It is shown in the present experiments that the actual injection duration is usually longer than the energizing time (ET). The time delay between the actual injection of the fuel and the ECU signal is about 0.3–0.4 ms, and the time delay appears to be insensitive to the injector geometry and injection pressure condition. The injection process can be characterized as five stages, a fast injector valve opening stage, a slow valve opening stage, a valve fully open stage, followed by a slow valve closing stage, and finally a rapid valve closing stage. It is found that the first stage, the fast valve opening stage, is insensitive to the injection pressure and injector nozzle diameter; however, the peak injection rate is a strong function of these parameters. The second and the third stage may not appear with a short injection duration. A new injection model was developed for the common rail injection system, which was capable of simulating the instantaneous fuel injection rate and injection duration for a range of injection pressure and injection duration. The model was shown to be able to replicate the experimental injection rate profile of the present experiments and experiments found in the literature for common rail injection system. The new injection model was applied to predict the effect of injection pressure and injection duration on the performance of a diesel engine under various engine speed and load conditions. The new injection model was shown to be able to describe the injection mass flow rate, which eventually leads to a reasonably good prediction of the variations of the spray development, in-cylinder pressure, heat release rate, and emissions.

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Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
CFD, Common rail injection system, Diesel engine, Injection rate, New injection model
in
Applied Energy
volume
230
pages
18 pages
publisher
Elsevier
external identifiers
  • scopus:85052295337
ISSN
0306-2619
DOI
10.1016/j.apenergy.2018.08.104
language
English
LU publication?
yes
id
f2cc23df-d5cd-4c6d-b90b-317c447ec6d8
date added to LUP
2018-09-25 08:00:36
date last changed
2019-05-21 04:11:22
@article{f2cc23df-d5cd-4c6d-b90b-317c447ec6d8,
  abstract     = {<p>Fuel injection is one of the most important processes in compression-ignition internal combustion engines owing to its significant impact on the exhaust emissions and thermal efficiency. In this study, experiments were carried out to investigate the influence of injection pressure and injection timing on the temporal evolution of the injection rate and injection duration in a specially designed experiment rig equipped with a common rail injection system. It is well known that the injection signal from the electronic control unit (ECU) of the injection system, which is often the only injection information available in engine operation and experiments, gives little information about the actual injection rate profile. It is shown in the present experiments that the actual injection duration is usually longer than the energizing time (ET). The time delay between the actual injection of the fuel and the ECU signal is about 0.3–0.4 ms, and the time delay appears to be insensitive to the injector geometry and injection pressure condition. The injection process can be characterized as five stages, a fast injector valve opening stage, a slow valve opening stage, a valve fully open stage, followed by a slow valve closing stage, and finally a rapid valve closing stage. It is found that the first stage, the fast valve opening stage, is insensitive to the injection pressure and injector nozzle diameter; however, the peak injection rate is a strong function of these parameters. The second and the third stage may not appear with a short injection duration. A new injection model was developed for the common rail injection system, which was capable of simulating the instantaneous fuel injection rate and injection duration for a range of injection pressure and injection duration. The model was shown to be able to replicate the experimental injection rate profile of the present experiments and experiments found in the literature for common rail injection system. The new injection model was applied to predict the effect of injection pressure and injection duration on the performance of a diesel engine under various engine speed and load conditions. The new injection model was shown to be able to describe the injection mass flow rate, which eventually leads to a reasonably good prediction of the variations of the spray development, in-cylinder pressure, heat release rate, and emissions.</p>},
  author       = {Xu, Leilei and Bai, Xue Song and Jia, Ming and Qian, Yong and Qiao, Xinqi and Lu, Xingcai},
  issn         = {0306-2619},
  keyword      = {CFD,Common rail injection system,Diesel engine,Injection rate,New injection model},
  language     = {eng},
  month        = {11},
  pages        = {287--304},
  publisher    = {Elsevier},
  series       = {Applied Energy},
  title        = {Experimental and modeling study of liquid fuel injection and combustion in diesel engines with a common rail injection system},
  url          = {http://dx.doi.org/10.1016/j.apenergy.2018.08.104},
  volume       = {230},
  year         = {2018},
}