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Jamie Turner, director, Lotus Engineering powertrain

Automotive Engineer: How will biofuels affect the engine of 2018?

Jamie Turner: With 2015 bringing the introduction of legislation to cap average carbon dioxide emissions from all new passenger cars at 125 g/km, increasing emphasis will be placed on renewable alcohols. Engines will need to be more flexible in their fuelling, with flex-fuel vehicles in common use. An alcohol fuel derived from renewable sources is potentially one of the most accessible options and would allow society to transfer relatively easily and quickly to a sustainable, renewable, environmentally-neutral energy economy. We are currently focusing our research on bio-derived ethanol and renewable synthetic methanol in high blends. I propose methanol as the ‘end game’, because it’s already a proven internal combustion engine fuel, can be synthesized from a huge range of feedstocks and by careful management of the production and use cycle could be made to be 100% carbon neutral. What’s more, with some of the possible feedstocks there is the possibility to manufacture all the fuel energy we need, for which there is a limit on ethanol.

As well as being green, the great benefit of synthetic methanol is that it can be used in similar engine and fuel systems to those already fitted to current cars. Furthermore, methanol can be stored, transported and retailed in much the same way as today’s liquid fuels, i.e. in a modified (but existing) infrastructure. This is a major difference to the introduction of the molecular hydrogen energy economy, estimates for the cost of which have been put at a trillion dollars for the US alone – chiefly driven by distribution and storage. Research into sustainable alcohols is progressing on a number of fronts at Lotus and partner institutions, including further development of the Exige 265E as a test-bed for future alcohol fuel technologies.

AE: How big will engines be in 2018?

JT: With an increased number of flex-fuel engines by that time, an optimised alcohol engine could downsize a gasoline engine by a further 20%. An average four-stroke spark-ignition car in 2018 optimized for alcohol, (still capable of operation at a lower output on gasoline, to ensure mobility during alcohol fuel introduction) might have a 750cc engine with an advanced pressure-charging system. In addition, a cooled exhaust gas recirculation at full load to reduce peak combustion temperatures, extending the knock limit and pushing thermal efficiency to in excess of that achievable with diesel engines.

There is currently more research being conducted into two-stroke and such engines in this case would have a slightly larger swept volume, possibly 1.2 litres and operate predominantly in Homogeneous Charge Compression Ignition (HCCI) combustion. Two-strokes can afford to have a larger swept volume because they do not suffer from throttling loss like the four-stroke engine does.

AE: What sort of valvetrain/induction developments do you expect?

JT: I expect two-stage turbo charging to be commonplace. Switching valve trains will also be dominant with some fully variable valve trains more frequently used in the more prestigious engines, though they will need to have been productionized in heavy duty diesel engines first. These are likely to be electro-hydraulic in nature, such as the system Lotus is currently producing.

AE: How will combustion strategies develop?

JT: Homogeneous Charge Compression Ignition will certainly be a production technology in one form or another, leading to cleaner combustion, better emissions and improved fuel economy. There could be significant developments in two-stroke combustion, something which we are researching. This is tied to variable compression ratio which is seen as a definite enabler for HCCI in some circles. New architectures such as monoblock construction (with the cylinder head and block combined) with integrated exhaust manifolds will help to reduce base engine costs to offset the increase in technology in other areas.

AE: What will be the cutting edge engine technology of 2018?

JT: Reciprocating engines will continue to dominate, although plug-in hybrids and even pure electric vehicles will not be unusual. It is clear that battery production technology will need to progress to reduce costs. Direct injection will be the norm on spark-ignition engines above 100 bhp and it will be a major, but gradual change over this period. Some engine architectural changes can be expected, but electronics are likely to progress at a faster rate. In-cylinder pressure measurement as a direct input to the engine management system will be common, particularly in diesel engines, but also for gasoline HCCI combustion systems.
The question of which fuels will be used is a very interesting proposition. Without a very serious breakthrough in hydrogen storage technology, it is likely that the hydrogen economy will not start to occur in this period. As a consequence, the fuel cell engine looks extremely unlikely.

Therefore the focus will shift to renewable alcohols and other low-carbon-footprint fuels, such as biomass, gas-to-liquid (BTL and GTL) and diesel, made using the Fischer-Tropsch process. Gasoline can be manufactured by such routes, but since the well-to-wheels efficiency achievable by the whole fuel-and-engine system cannot be as high as with an optimised engine operating on a renewable alcohol, it poses the question, is there a need to use F-T gasoline? As discussed, using methanol as a renewable fuel is a more readily accessible step, and in any renewable energy future, achieving the maximum efficiency for the whole system will be paramount.

Looking further into the future, thermodynamically, we feel that future research into the gas turbine engine would be worthwhile in this time scale as a longer-term competitor to the diesel engine in series hybrid vehicles. We do however accept that the cost implications need to be investigated more thoroughly. With regard to electric hybrids in general, a significant amount will have plug-in capability and hub motor technologies will also be common in the market place. Introduction of kinetic energy recovery devices are also a serious possibility for vehicles with higher-power-to-weight ratios.

Ultimately, once the internal combustion engine, with its ability to consume mixtures of fuels, has brought pure methanol onto the forecourt, the direct methanol fuel cell (DMFC) could become the primary power source in vehicles. The DMFC will likely triumph over the hydrogen fuel cell not because of any inherent advantage in the fuel cell itself, but because economics can be used to draw its fuel into filling stations. Although introducing a synthetic alcohol energy economy centred on methanol would undoubtedly be more expensive than continuing with fossil fuel, from a global warming viewpoint, it is implementable in a logical manner with a soft start and can be promoted by taxation breaks for ethanol/gasoline flex-fuel cars.

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