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Nozzle Coking in CNG-Diesel Dual Fuel Engines: 2014-01-2700
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.ORCID iD: 0000-0002-4243-7134
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
2014 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Nozzle coking in diesel engines has received a lot of attention in recent years. High temperature in the nozzle tip is one of the key factors known to accelerate this process. In premixed CNG-diesel dual fuel, DDF, engines a large portion of the diesel fuel through the injector is removed compared to regular diesel operation. This can result in very high nozzle temperatures. Nozzle hole coking can therefore be expected to pose a significant challenge for DDF operation.In this paper an experimental study of nozzle coking has been performed on a DDF single cylinder engine. The objective was to investigate how the rate of injector nozzle hole coking during DDF operation compares to diesel operation. In addition to the nozzle tip temperature, the impact of other parameters on coking rate was also of interest.Start of injection, λ, diesel substitution ratio and common rail pressure were varied in two levels starting from a common baseline case, resulting in a total of 10 operating cases. These cases were run for three and a half hours in steady-state, using standard injectors and zinc contaminated diesel to accelerate the coking process. The zinc was added in form of zinc neodecanoate, similar to the practice in the standardized tests used to study nozzle coking in diesel engines.After the tests the injectors were disassembled and the steady state flow through the injector nozzles was measured to isolate the effect of nozzle hole coking. The results show significant coking from only a few hours of testing. The most challenging case was the combination of high nozzle tip temperature from DDF operation with low injection pressure. The flow loss from operation in DDF mode was far more severe compared to diesel operation. Elemental analysis of the deposits shows similar composition resulting from diesel and DDF operation. In the DDF deposits higher concentrations of elements from the engine oil were found in addition to higher carbon content. It is concluded that injector nozzle coking is a challenge which requires appropriate attention when developing DDF engines.

Place, publisher, year, edition, pages
2014.
National Category
Energy Engineering
Research subject
Machine Design
Identifiers
URN: urn:nbn:se:kth:diva-151190OAI: oai:DiVA.org:kth-151190DiVA: diva2:746997
Conference
SAE Powertrains, Fuels & Lubes 2014
Funder
Swedish Energy Agency
Note

QC 20140915

Available from: 2014-09-15 Created: 2014-09-15 Last updated: 2014-09-15Bibliographically approved
In thesis
1. On Combustion in the CNG-Diesel Dual Fuel Engine
Open this publication in new window or tab >>On Combustion in the CNG-Diesel Dual Fuel Engine
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Currently there is a large interest in alternative transport fuels. There are two underlying reasons for this interest: the desire to decrease the environmental impact of transports and the need to compensate for the declining availability of petroleum. In the light of both these factors, the CNG-diesel dual fuelengine is an attractive concept. The primary fuel of the dual fuel engine is methane, which can be derived both from renewables and from fossil sources. Methane from organic waste, commonly referred to as biomethane, can provide a reduction in greenhouse gases unmatched by any other fuel. Furthermore, fossil methane, natural gas, is one of the most abundant fossil fuels.Thedual fuelengine is, from a combustion point of view, a hybridof the diesel and theOtto-engineand it shares characteristics with both.

From a market standpoint, the dual fuel technology is highly desirable; however, from a technical point of view it has proven difficult to realize. The aim of this project was to identify limitations to engine operation, investigate these challenges, and ,as much as possible, suggest remedies. Investigations have been made into emissions formation, nozzle-hole coking, impact of varying in-cylinder air motion, behavior and root causes of pre-ignitions, and the potential of advanced injection strategies and unconventional combustion modes. The findings from each of these investigations have been summarized, and recommendations for the development of a Euro 6 compliant dual fuel engine have been formulated. Two key challenges must be researched further for this development to succeed: an aftertreatment system which allows for low exhaust temperatures must be available, and the root cause of pre-ignitions must be found and eliminated.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. x, 98 p.
Series
TRITA-MMK, ISSN 1400-1179 ; 2014:08
National Category
Energy Engineering
Research subject
Machine Design
Identifiers
urn:nbn:se:kth:diva-151188 (URN)978-91-7595-243-7 (ISBN)
Public defence
2014-09-26, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency
Note

QQC 20140915

Available from: 2014-09-15 Created: 2014-09-15 Last updated: 2014-09-15Bibliographically approved

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