Annex 51: Methane Emission Control
The use of methane (natural gas, biogas) for transport will increase. Dual diesel fuel (DDF) technology could bring the efficiency of gas engines close to that of diesel engines, but Annex 39 clearly demonstrated that methane slip is a serious problem for current DDF engines. Alternatively, advanced SI technologies (e.g. variable valve trains, cylinder de-activation, high-level EGR) could be applied to increase engine efficiency. However, there is a need for methane catalysts, and the performance and durability of current methane catalysts are not satisfactory.
A new Annex will be based on the experience from Annex 39 to improve engine out methane emissions as well as methane catalyst efficiency and methane emissions from other part of the vehicle. The Annex will also continue following up heavy-duty methane vehicle fleets, thus adding on to data already available.
Purpose and Objectives
Combustion engines for vehicles can be replaced by / converted to LNG (Liquefied Natural Gas) operation. This has benefits in terms of CO2, NOx and particulate emissions. CO2 reductions are due partly to the fact that the ratio between carbon and hydrogen is less for natural gas than for liquid hydrocarbons (diesel, gasoline etc.), and partly because the engines can have greater efficiency than the traditional ones, depending on the combustion principle chosen. Concerning greenhouse gas effects, it is a disadvantage that the engines emit significantly larger quantities of unburned methane than the traditional ones. As methane is a 20 times more powerful greenhouse gas than CO2, the overall result can easily be an increase in greenhouse gas emissions from vehicles, if the engines are converted to LNG.
There is much experience from unburnt hydrocarbons in automobile engines. This experience has resulted in engines with very low emissions of hydrocarbons. Methane is, however, a particularly stable hydrocarbon and is not converted as efficiently as other hydrocarbons in combustion engines. At the higher temperatures during the main combustion methane is combusted as other hydrocarbons. However, in colder areas near the walls and in crevices, some unburned hydrocarbons escape the main combustion. These hydrocarbons are normally post oxidized in the hot combustion gas. Methane, however, is too stable a molecule to be converted at these lower temperatures. This also causes problems with conversion of methane in after treatment systems like three-way catalytic converters. The onboard storage system for methane, compressed or liquefied, could also be a source of methane emissions from the vehicle.
The purpose of this project is thus to understand and identify causes of the high emissions of unburned methane or emissions of methane from other parts than the engine and assign the best ways to reduce these emissions.
- WP 0: Project Management
- The project management will be taken care of in by The Technical University of Denmark.
- WP 1: Application of Natural Gas in Combustion Engines
- An overview of the application of natural gas in combustion engines for transportation purposes will be given. The WP will focus on road and marine transportation since these are the transport sectors where the ideas of implementing methane in the form of natural gas or biogas are mostly dominating.
- WP 2: Fundamental Investigations of Methane Combustion
- The project is carried out partly as a theoretical study of the fundamental physical / chemical processes in a natural gas engine. Mathematical models of the processes that describe the phenomena during the conversion of the fuel in the engine will be formulated. The models will describe the influence of the combustion principle, spark-ignition or "dual fuel" (DF), the combustion chamber geometry and the application of mixed fuels. It is known that for example mixtures of natural gas and smaller amount of hydrogen makes it possible to reduce the emission of unburned methane as the hydrogen promotes the combustion of methane. DME is another fuel option to promote methane conversion. The models will be verified in engine experiments where the relevant engine parameters are varied in order to verify the models.
- The reduction of unburned methane from engines can be reduced by after treatment in a catalytic converter in the exhaust pipe. However, it is still difficult to convert the methane at the temperatures that are available. Studies of the most suitable catalyst materials / systems, and the conversion of methane at different concentrations, temperatures and pressures will be carried out.
- WP 3: Methane emissions from other parts of the vehicle than the engine and exhaust system
- Compared with liquid fuels like diesel, gaseous fuels possess a higher risk to escape from the vehicle. During refueling the connection and disconnection of the dispensing nozzle might result in small amounts of methane escaping to the ambient air. Storage of fuel, both liquefied and compressed methane, could be vented out to the atmosphere to avoid overpressure. High pressure fuel lines and joint could also be a source of leakage which needs to be investigated. The purpose of this WP is to study possible methane emissions from other parts of the vehicle than the engine or exhaust system. If possible the emissions should also be quantified.
- WP4: Natural Gas Application in LD Vehicles
- An overview of the knowledge about unburned methane from LD vehicle engines today will be given. The study will reveal the available data that can be used for verifying the models developed in WP 2. Furthermore, the study will focus on present technologies available and the policy/future plans for implementing methane containing fuels for these vehicles.
- WP 5: Natural Gas Application in HD Vehicles
- An overview of the knowledge about unburned methane from HD vehicle engines today will be given. The study will reveal the available data that can be used for verifying the models developed in WP 2. Furthermore, the study will focus on present technologies available and the policy/future plans for implementing methane containing fuels for these vehicles.
- WP 6: Natural Gas Application in Marine Engines
- An overview of the knowledge about unburned methane from marine engines today will be given. The study will reveal the available data that can be used for verifying the models developed in WP 2. Furthermore, the study will focus on present technologies available and the policy/future plans for implementing methane containing fuels for the marine sector.
|Project Duration||June 2014 - December 2018|
|Participants||Denmark, Finland, Germany, Japan LEVO, Korea, Sweden, Switzerland|
|Total Budget||~ 500,000 €|
Prof. Jesper Schramm
Technical University of Denmark (DTU)
Nils Koppels Allé, Bldg 403
phone: +45 4525 4179
fax: +45 45884325