Ethanol: flexible friend or biohazard?

Increasing the ethanol content in fuels is one way to reduce carbon emissions but there are a number of technical challenges to consider

Published:  16 November, 2018

I am starting to get the impression that governments and vehicle manufacturers are beginning to panic. Let’s begin by accepting that personal transportation vehicles will not be powered by hydrocarbon fuels for much longer. This statement includes hybrid and battery powered vehicles for the same reason. We are being subject to a whole raft of short term impractical solutions, the latest of which and the subject of this topic is bio-ethanol fuels.

The reason I express this opinion is the true impact on emissions, from production, refinement, and transportation are not included in statistics on their environmental effect. Bio-mass fuel for electricity generation is a perfect example of this. The EU has decreed that emission monitoring of stack emissions need not be published, also excluded are the felling, drying, production and transportation influences.

Political initiative
I will begin with the political initiative, a reduction in greenhouse gas emissions, reduction in fossil fuel dependency, alternative fiscal revenue for the farming community, and a reduction in EU farming subsidies. Try not to laugh it’s all true. As third world nations starve, we grow fuel!

Ethanol is a hydrocarbon c2h5oh. Octane 104. The fuel is produced from a fermentation process from fast growing energy crops, sugar cane, wheat, maize, and sometimes bio-degradable waste animal feed and timber. The claim is that due to the renewable factor it has an advantage over fossil fuel. Vehicles can operate with up to 85% bio-content, with no operational disadvantages with high CO2 reduction. I can confirm from my European motorcycle tour this year, that e10 bio-ethanol fuel is widely available.

Considerations
Just before you dash out to join the Green Party, there are some technical considerations the government seems to have overlooked. Bio-ethanol fuel is corrosive, copper, aluminium, plastics and rubber list among its appetite. Just before I forget, there is a critical lubrication service update; this is due to an increase in fuel oil contamination.

I think you’re starting to get the picture, now let’s focus on its combustion problems. It has a unique evaporation envelope around 78ºC. It also requires a significant increase in fuel quantity on cold start, often requiring a pre-heater system, and a much-modified ignition profile. However, on the positive side once efficient combustion is achieved the knock resistance affords a more aggressive ignition angle and increased cylinder pressures.

I am going to focus on Audi who have offered a flexi fuel A4 since 2009! It could operate up e85 with no modification. To my knowledge there are no or very few bi-ethanol vehicles in the UK. You may have noticed warning stickers in the fuel filler cap on most vehicles, expressing non- bio compatibility.

So, back to my point: Why is the uk government considering a pilot trial for e10? Currently all gasoline sold in the uk can have e5 content without any notification at the pumps.

Requirements
Moving on to the technical requirements, the Audi flexi-fuel engine is based on the 2.0 tfsi, with Bosch med 17.1 control. Sequential mapped ignition, with knock control, digital hot film air mass measurement. Fuelling is homogenous direct injection, with port injection on cold start. Intake cam adjustment with avs on the exhaust cam.

Due to low vaporisation when cold, ‘autarkic cold start’ ,the air fuel mixture cannot form the required composition for ignition. Significant modification to con rods and bearings are required to withstand higher cylinder pressure. Modifications to the variable load in- tank pump components and wiring prevent corrosion damage. An additional digital fuel quality sensor is fitted to the
low-pressure fuel line, this enables critical adjustment to thermodynamic fuel properties and ignition maps.
 
Bosch injection control strategy includes injection on intake and compression, with multiple strike on compression when cold, with additional injection pressure of 150 bar. A new aluminium manifold with a port injector is fitted to avoid pre-heaters on cold start.
The point I am trying to make here is not based on a simple pessimistic naivety, but a serious concern that not enough focus is being applied to a long-term strategic solution. Two key prerequisites will have to be recognised, the first is a reconstruction of social order around a coherent public transport system, and the second a recognition that private vehicle transport is a privilege and not an automatic right.


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