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Combustion Modes in a Diesel-CNG Dual Fuel Engine
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
AVL Sweden.
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
2011 (English)In: SAE Technical Paper 2011-01-1962, 2011, Society of Automotive Engineers of Japan, Inc , 2011, 2387-2398 p.Conference paper, Published paper (Refereed)
Abstract [en]

Diesel Dual Fuel, DDF, is a concept where a combination of methane and diesel is used in a compression ignited engine, maintaining the high compression ratio of a diesel engine with the resulting benefits in thermal efficiency.

One benefit of having two fuels on board the vehicle is the additional degree of freedom provided by the ratio between the fuels. This additional degree of freedom enables control of combustion phasing for combustion modes such as Homogenous Charge Compression Ignition, HCCI, and Partly Premixed Compression Ignition, PPCI. These unconventional combustion modes have great potential to limit emissions at light load while maintaining the low pumping losses of the base diesel engine.

A series of tests has been carried out on a single cylinder lab engine, equipped with a modern common rail injection system supplying the diesel fuel and two gas injectors, placed in the intake runners. Four load points are investigated and three different types of combustion are evaluated.

The study confirmed the desirable emission characteristics of HCCI and PPCI combustion and demonstrated the potential to control the combustion phasing by utilizing all degrees of freedom provided by a common rail injection system and two fuels.

Place, publisher, year, edition, pages
Society of Automotive Engineers of Japan, Inc , 2011. 2387-2398 p.
Keyword [en]
Diesel Dual Fuel, Biogas, DDF, CNG, methane, HCCI, PPC, PPCI, RCCI
Keyword [sv]
Förbränningsmotorteknik, metan
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-65693DOI: 10.4271/2011-01-1962Scopus ID: 2-s2.0-84881193912OAI: oai:DiVA.org:kth-65693DiVA: diva2:483553
Conference
JSAE Powertrains, Fuels & Lubricants
Projects
Diesel Dual Fuel
Note
QC 20120202Available from: 2012-02-02 Created: 2012-01-25 Last updated: 2014-09-15Bibliographically approved
In thesis
1. Advancing the Limits of Dual Fuel Combustion
Open this publication in new window or tab >>Advancing the Limits of Dual Fuel Combustion
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

There is a growing 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 Diesel Dual Fuel, DDF, engine is an attractive concept. The primary fuel of the DDF 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. The DDF engine is from a combustion point of view a hybrid between the diesel and the otto engine and it shares characteristics with both.

This work identifies the main challenges of DDF operation and suggests methods to overcome them. Injector tip temperature and pre-ignitions have been found to limit performance in addition to the restrictions known from literature such as knock and emissions of NOx and HC. HC emissions are especially challenging at light load where throttling is required to promote flame propagation. For this reason it is desired to increase the lean limit in the light load range in order to reduce pumping losses and increase efficiency. It is shown that the best results in this area are achieved by using early diesel injection to achieve HCCI/RCCI combustion where combustion phasing is controlled by the ratio between diesel and methane. However, even without committing to HCCI/RCCI combustion and the difficult control issues associated with it, substantial gains are accomplished by splitting the diesel injection into two and allocating most of the diesel fuel to the early injection. HCCI/RCCI and PPCI combustion can be used with great effect to reduce the emissions of unburned hydrocarbons at light load.

At high load, the challenges that need to be overcome are mostly related to heat. Injector tip temperatures need to be observed since the cooling effect of diesel flow through the nozzle is largely removed. Through investigation and modeling it is shown that the cooling effect of the diesel fuel occurs as the fuel resides injector between injections and not during the actual injection event. For this reason; fuel residing close to the tip absorbs more heat and as a result the dependence of tip temperature on diesel substitution rate is highly non-linear. The problem can be reduced greatly by improved cooling around the diesel injector. Knock and preignitions are limiting the performance of the engine and the behavior of each and how they are affected by gas quality needs to be determined. Based on experiences from this project where pure methane has been used as fuel; preignitions impose a stricter limit on engine operation than knock.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. v, 56 p.
Series
Trita-MMK, ISSN 1400-1179
Keyword
Diesel Dual Fuel, Methane, CNG, Biogas, Injector, Coking, Knock, Pre-ignition, Preignition, HCCI, PPCI, PPC, RCCI
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-96945 (URN)978-91-7501-427-2 (ISBN)
Presentation
2012-06-15, B319 Gladan, Brinellvägen 83, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
Diesel Dual Fuel
Note
QC 20120626Available from: 2012-06-26 Created: 2012-06-13 Last updated: 2012-06-26Bibliographically approved
2. 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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