Twitter headlines« Pintle-Regulated Venturi Induction Prototype Achieves 52 mpg at 65 mph | Main | Japan Airlines Plans Biofuel Demonstration Flight »
Ford, Brunel Studying CAI Combustion with Methanol and Ethanol in Direct Injection Engine
23 June 2008
Researchers at Ford Motor Company’s Dunton Technical Centre (UK) and Brunel University (UK) are studying CAI (controlled auto-ignition, also referred to as HCCI, homogeneous charge compression ignition) combustion of methanol and ethanol as part of a larger, on-going CAI project.
In results presented at the 2008 SAE International Powertrains, Fuels and Lubricants Congress in Shanghai (23-25 June), the researchers found that both oxygenate fuels, methanol and ethanol, can lead to CAI combustion as well as gasoline fuel. The load of CAI combustion was increased and emissions were lower with the two oxygenate fuels. Methanol was found to have highest output and lowest energy consumption among the three fuels tested.
CAI combustion CAI (controlled auto-ignition) combustion, in which the air/fuel mixture is ignited spontaneously like in diesel engine combustion, has the potential to increase fuel economy while simultaneously decreasing NOx emissions. However, applying CAI faces a number of challenges that are the subject of on-going research in the industry: obtaining reliable auto-ignition; controlling ignition and combustion phases; enlarging the CAI operation range; and smoothly switching between CAI and SI (spark ignition) combustion modes.
One way to overcome those challenges is to use different fuels which have more beneficial properties for to CAI.
In their study of the CAI of methanol, ethanol and gasoline, Yufeng Li from Ford and Hua Zhao and Nikolaos Brouzos from Brunel University used a single-cylinder direct gasoline engine outfitted with a prototype GDI (gasoline direct injection) cylinder head supplied by Orbital Engine Corporation Ltd. Orbital features air-assisted direct injection. (Earlier post.)
The engine has a bore of 80mm and a stroke of 89mm; the compression ratio is 10:1. To trap sufficient amounts of residual gases in the cylinder to initiate CAI combustion, the original intake and exhaust camshafts were substituted by those with low lift and short duration.
| Fuel Properties | |||
|---|---|---|---|
| Gasoline (CnH1.87n) | Methanol (CH3OH) | Ethanol (C2H5OH) | |
| Stoichiometric A/F ratio | 14.6 | 6.47 | 9.00 |
| Density (kg/m3) | 720-780 | 792 | 785 |
| RON | 95 | 106 | 107 |
| MON | 80-90 | 92 | 89 |
| Low heating value (MJ/kg) | 44 | 20 | 26.9 |
| Heat of vaporization (kJ/kg) | 305 | 1,103 | 840 |
| LHV of stoich. mixture (MJ/kg) | 2.83 | 2.68 | 2.69 |
| Auto-ignition temperature (°C) | 260-460 | 460 | 360 |
Methanol and ethanol and both oxygenate fuels. The presence of oxygen gives each a lower stoichiometric air/fuel ratio—i.e., they require less air for combustion than does gasoline. Both methanol and ethanol have higher octane numbers than gasoline. In general, higher octane fuels is more difficult to self-ignite.
Methanol has a lower heating value (LHV) half that of gasoline. Ethanol’s LHV is one-third lower than gasoline. Although the three fuels have different LHVs, the LHV of their stoichiometric mixtures remains similar.
Methanol has a heat of vaporization that is 3.5 times higher than gasoline; ethanol’s is 1.5 times higher.
This property may give oxygenate fuels (especially methanol) such different mixture preparation compared to gasoline fuel: lower charge temperature if the mixture is homogeneous, or more complicate thermal distribution if the mixture is not uniformly distributed. Thus, the auto-ignition and CAI combustion process will be affected.
Gasoline also has a lower auto-ignition temperature than methanol, also affecting the initiation of CAI combustion.
From their test results, the team drew three primary conclusions:
Ethanol and ethanol can achieve CAI combustion under conditions similar to those required for gasoline CAI on direct injection SI engines.
Methanol can produce more output and give higher fuel conversion efficiency in CAI combustion than ethanol, which in turn is better than gasoline.
CAI combustion of methanol and ethanol produces less HC and NOx emissions than gasoline CAI combustion.
However, they noted, the test results also show some points which remain unclear and will require further investigation, including:
The relative CAI combustion characteristics of the three fuels seem to vary with the EVC (exhaust valve closure, the mechanism for initiation of self-ignition) or EGR rate. They attributed that variance to the different fuel properties (heat of vaporization, LHV and auto-ignition temperature).
In order to understand CAI combustion with different EVC timing or EGR rate for the three fuels, the researchers will investigate air/fuel/EGR mixture formation and thermal distribution by using optical diagnostics.
Gasoline fuel yields higher NOx emissions at a lower combustion temperature than the two oxygenate fuels at the EVC of -70°CA. Although a lower EGR rate is one of reasons to increase NOx emission for gasoline, other root causes still need to be investigated by measuring and analyzing air/fuel/EGR mixing and thermal distribution.
Injection in the exhaust process may exhibit different CAI combustion characteristics than injection in the intake process because fuels have been greatly vaporized and mixed with air and residuals—i.e., re-conditioned or reformed—during the recompression process. Further investigation of this will aid in understanding CAI combustion differences of methanol and ethanol on port injection SI engines and on direct injection SI engines.
Resources
Yufeng Li, Hua Zhao and Nikolaos Brouzos (2008) CAI Combustion with Methanol and Ethanol in an Air Assisted Direct Injection Gasoline Engine (SAE 2008-01-1673)
June 23, 2008 in Engines, Ethanol, Fuel Efficiency, Methanol | Permalink | Comments (4) | TrackBack (0)
Comments
Posted by: Alex Kovnat | June 23, 2008 at 10:37 AM
Fermentation is only one way to make ethanol from biomass. There is another process using gasification and catalytic synthesis, which yields more energy than fermentation. The synthetic system could produce methanol instead of ethanol if methanol was a more desirable fuel.
Posted by: Reality Czech | June 23, 2008 at 11:28 AM
Coalseam methane is a GHG 21* CO2 equivalent. Currently freely emitted to he atmosphere when the coal is mined. The quantity of recoverable methane is described as mind boggling and sufficient to meet all energy requirements for decades. The unknown quantities can only be guessed.
If a sustainable extraction rate is applied where exploitation is matched to the most efficient longer term recovery, rather than a careless ripp it out approach , a case could be made that we could reduce greenhouse gases while burning fossil fuel.
A case can be made that many coal reserves marked for development have a higher value in the ground.
A few " facts"
Apparently anthropological CO2 emissions 3% 'Natural' 97%
methane emissions 75% - 'natural' 25%
http://www.countercurrents.org/cc-hunt291106.htm
http://news.bbc.co.uk/2/hi/science/nature/6638705.stm
http://www.enn.com/top_stories/article/3935 etc. paste
What are some kinds of carbon offset solutions/approaches and how do you offset the CO2?
A variety of CO2 offsets are offered in the marketplace, by various sources. One example of what constitutes an offset is planting a tree for each ton of CO2 that is being offset. This 'forestry' approach assumes that over the life of the tree it will absorb at least a ton of CO2 and convert it to wood that will survive for hundreds of years. Another common way to offset CO2 is to build windmills or install solar panels to generate power without carbon or other greenhouse emissions. The only problem with relying on companies that sell these self-regulated solutions, is that it's difficult to know if you are receiving a valid offsets
One of the strangest ways offered to offset CO2, is by burning methane gas that would otherwise be released into the atmosphere. Burning methane actually generates 133 pounds of CO2 for every 1000 ft3, of gas that is burned. While its a shock to hear that burning methane offsets CO2, it turns out that each pound of methane released into the atmosphere is as damaging to the earth as 20 pounds of CO2. Thus burning this free methane to emit CO2 actually reduces the greenhouse effect. This is a case of the truth seeming stranger than fiction.
Posted by: arnold | June 23, 2008 at 03:52 PM
This technology seems to have been surpassed (or soon to be) by the MUSIC cylinder head.
Posted by: | June 24, 2008 at 12:10 PM
TrackBack
TrackBack URL for this entry:
http://www.typepad.com/services/trackback/6a00d8341c4fbe53ef00e55368fb708833
Listed below are links to weblogs that reference Ford, Brunel Studying CAI Combustion with Methanol and Ethanol in Direct Injection Engine:
One question I would like to ask is: If you use methanol for your CAI engine, where will it come from? Right now, most of the world's methanol is produced using natural gas as the basic raw material. NG produces less CO2 than coal, but it is still a fossil fuel.
With biomass, hopefully we will see in the foreseeable future processes whereby hemicellulose and cellulose will be broken down into 5 and 6 carbon sugars, for subsequent fermentation. But the output from this process will be ethanol, not methanol.
Methanol is a problematic fuel, in that it is corrosive and its high heat of evaporation makes cold-weather starting very difficult. But, as Dunton Technical Center's research demonstrates, it cannot be ruled out altogether.