Glow plugs are widely used to promote the desired cold start and post-cold start combustion characteristics of light duty diesel engines. The importance of the glow plug becomes more apparent when the compression ratio is low. An experimental investigation of combustion initiation and development aided by the glow plug has been carried out on a single cylinder HPCR DI diesel engine with a low compression ratio of 15.5:1. High speed imaging of combustion initiated by the glow plug in a combustion bomb has been used to add understanding of initiation process. Complementary CFD studies have been carried out using ANSYS Fluent 14.0 to explore the interactions between the glow plug and the spray behavior. Observation of successful combustion initiation show that two conditions must be met, compression heating and heat transfer from the glow plug must raise temperature of gas nearby to at least 413ºC and the vapour/air equivalence ratio no lower than 0.15-0.35. The initiation site was at spray edge close to the glow plug, the flame grew locally before expanding downstream in direction of spray penetration after the end of the main injection. Experimental studies carried out on the engine indicated that the engine IMEP, heat release and combustion stability were continuously improved by using the glow plug at ambient temperatures higher than the temperature requiring the glow plug for initiation of combustion. A rapid development of premixed combustion was achieved associated with improved engine work output, heat release rate and cycle-by-cycle stability. The premixed combustion was enhanced by strengthening spray vaporization through the glow plug. In this study, the combustion behavior was enhanced by the glow plug up to ambient temperature of 20ºC. Initiation delay was shortened by a rapid development of combustion aided by the glow plug. An initiation delay model was developed to account for both physical part (transport delay) and chemical part (chemical delay). The transport delay (ms) is equivalent to the time for spray to transport to the vicinity of the glow plug, dictated by parameters including S, distance between the glow plug tip and the injector tip (mm).
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:703206 |
| Date | January 2016 |
| Creators | Li, Qile |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.nottingham.ac.uk/35875/ |
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