MCE-5 VCRi: Pushing back the fuel consumption reduction limits

It’s multi-fuel

MCE‑5 VCRi: An IC engine paving the way to the post-oil era

We consume more oil every day than we discover. The increased scarcity and then the quasi-disappearance of oil is inevitable – it’s only a matter of time. As of the next decade, oil production will no longer fully cover market needs, and this will directly impact its price. To attenuate the effects of costly oil, it will be necessary to use other energy sources, such as biomass (ethanol, alcohols, CEE, vegetable oils, EMHV, ETBE, MTBE), natural gas, coal and in the long term, hydrogen produced with renewable energies or nuclear power.

Supply-demand imbalance will lead to a high increase
in the price of crude oil within the next 20 years

Biomass, whether oil, alcohol or biogas,
will play a major role in coming years

There are several possible scenarios with respect to cars using these energy resources.

The first and most probable scenario consists in using these non-petroleum energy sources to produce gas and diesel. According to this scenario, we will continue to have easy-to-use fuels, which are completely compatible with existing distribution networks and vehicle fleets. The production of synthetic gasoline and diesel will use hydrogenation or carbonization processes. We should see the development of BTL (Biomass To Liquid), CTL (Coal To Liquid) or GTL (Gas To Liquid) mainly based on the Fischer-Tropsch or Bergius processes and their variants. Certain conversion units will be able to simultaneously use energy with high carbon contents (coal) and others with low carbon contents (gas) to ensure a carbon budget as neutral as possible. Nuclear energy could supply the electricity, heat and even hydrogen required for these transformation processes, while producing minimum CO2. According to this first scenario, the production of gasoline and diesel will eventually become a real synthetic industry, similar to the petrochemical industry.

The second scenario consists in developing vehicles adapted to each fuel. This involves planning a storage system for the specific fuel, as well as an engine with an adapted compression ratio, fuel supply and engine management systems. In this case, certain vehicles would be designed and optimized for natural gas, while others would be adapted to ethanol or different types of gasolines. This approach is costly and complex, because not only must the vehicles be modified but an appropriate distribution network must also be planned for each type of fuel. There will be different deployment and market acceptance issues for this second scenario: it will be difficult, for example, to sell natural gas vehicles in the absence of a sufficiently dense natural gas refueling network. Moreover, setting up such a network when the fleet of natural gas vehicles is too small is not profitable. Changing over to other fuels can also lead to problems with behavioral habits and feelings of insecurity that will slow people buying into them. Simplifying the distribution and use of fuels is essential: in France, instead of developing service stations distributing E85 (15% gasoline and 85% ethanol), we could have incorporated more ethanol into standard fuels without any modification to service stations or vehicles. This strategy could have been used since farms cannot produce enough to increase the ethanol content in gasoline to such a point that gasoline engines would have to be modified.

Conventional crude oil will progressively give way to other energy sources

The MCE‑5 VCRi variable compression ratio makes
it possible to optimise the use of different
fuels with variable characteristics

The MCE‑5 VCRi can run equally as well on natural
gas or gasoline, with a better efficiency than
a fixed compression ratio engine running
only on natural gas or only on gasoline

For all of these reasons, it’s probable that the future will be based on a third scenario, which will be a combination of the first two. Indeed, standard fuels are destined to become “cocktails” made up of different energy sources. Due to this, it will be more difficult to guarantee the fuel characteristics as precisely as we do today without making it expensive. For this reason, it will be vital for engines to automatically adapt to large variations in quality and characteristics while drawing the best performance and efficiency with minimal pollutant emissions. To achieve this result, engines will have to be truly flexfuel/multifuel, which means that they’ll require a variable compression ratio.

The compression ratio is in fact the main characteristic enabling the adaptation of an engine to a fuel whose octane number is more or less high. Since it has a variable compression ratio, the MCE‑5 VCRi engine can automatically adapt to any fuel, regardless of its octane number. With an appropriate engine management system, the MCE‑5 VCRi could in future “learn” which fuel it is dealing with by detecting its characteristics (knock detection at certain operating points). Hence, it will be able to select its “sub-program” and function with a higher compression ratio when using a fuel with a high octane number, and vice versa for a fuel with a low octane number. This basic characteristic enables the elimination of any knock phenomenon when consuming a fuel with a low octane number (i.e.: SP 95 or lower), and avoiding any useless loss in efficiency when running on a fuel with a high octane number (i.e.: SP 98, gasoline with a high ethanol content, natural gas). This function also allows starting the engine at -20°C on pure ethanol, avoiding fuel additives with toxic anti-knock agents (example: MTBE), or automatically adapting the engine management program to strong variations in the quality of natural gas depending in its origin.

The extreme flexibility of MCE‑5 VCRi should accompany the development of new fuels without having to make concessions in the engine’s energy efficiency, regardless of the different fuels that it runs on. Today’s “flexfuel” cars are based on a compromise: when they run on gasoline, their efficiency is lower than that of cars running exclusively on gasoline, and when they run on ethanol, their efficiency is lower than that of cars running only on ethanol. While they are supposed to reduce CO2 emissions, these flexfuel cars do not use the fuels at their maximum efficiency – this strategy goes against its objective. This result is due to the absence of a variable compression ratio (VCR): without VCR, an intermediate compression ratio must be found that is an acceptable compromise. This is done to the detriment of the flexfuel car’s final energy efficiency, but it is the only way to allow the car to use both conventional gasoline and ethanol. In future, MCE‑5 VCRi technology will eliminate this compromise so that all fuels will be used at their maximum efficiency in flexfuel cars. Thanks to MCE‑5 VCRi, it will even be possible to distribute cheap “generic” gasoline whose characteristics will vary according to supply or regulatory constraints: the engine will automatically adapt to this gasoline to get the best fuel efficiency, in totally safe conditions for the engine.

It’s impossible to speak of the diversification of energy resources for cars without focusing on the specific case of natural gas. This essentially fossil and potentially renewable (biogas) energy source is destined to become a strategic ally of the automobile in coming years, and particularly as of 2020-2025.

Natural gas is a low carbon fuel. When directly burned in a combustion engine, it emits roughly 20% less CO2 with the same service provided. This characteristic drastically reduces the carbon footprint of the vehicles running on it. Moreover, natural gas is present in large quantities and better distributed across the world than oil is, which should reduce the energy dependence of western transportation on politically unstable countries. What’s more, a fairly dense network of gas transmission pipelines ensures the transport of natural gas from the areas of production to the different areas of consumption. In areas with high population density, natural gas is delivered directly into homes.

As previously explained, it’s technically possible to convert natural gas into gasoline or even diesel (GTL: gas to liquids). However, this conversion eats up roughly 35 to 40% of the energy contained in the gas, representing a huge waste and an economic loss. The GTL industry requires approximately 10 joules of “gas” to produce 6 joules of “gasoline” so that from well to tank, the gasoline produced from natural gas emits 30% more CO2 than the gasoline produced from oil. In addition, once the gas has been transformed into gasoline, we lose the 20% reduction in CO2 emissions per km that the direct combustion of natural gas provides to vehicles. Used at a large scale for cars, natural gas must therefore absolutely be consumed as is, without any prior conversion. This means that the gas must be stored on board under high pressure (roughly 200 bar) in cylinder-, spherical- or toiraodal-shaped tanks. Heavier and bigger than gasoline tanks, these gas reservoirs take up a lot of room. In this context, engine efficiency becomes a determining factor to ensure that the vehicle has enough range without sacrificing too much on-board volume. This energy efficiency objective is directly served by the increase in energy efficiency provided by MCE‑5 VCRi technology via the optimization of the compression ratio, hard downsizing and reduced friction.

In the medium term, be it of fossil or renewable origin, unconverted natural gas for cars will be an excellent complement or even an alternative to oil. Nevertheless, to ensure its commercial success and to support the development of the required network of service stations, vehicles will also have to be able to consume gasoline with a high efficiency and without compromising vehicle performance. This will necessarily require a variable compression ratio such as the one proposed by MCE‑5 VCRi. Indeed, the MCE‑5 VCRi can run equally as well on natural gas or gasoline, with a better efficiency than a fixed compression ratio engine running only on natural gas or only on gasoline. The strategic advantages to be gained from this feature are immense in the next 20 to 30 years and go largely beyond the scope of automobiles. The goal is sustain individual mobility, on which a large part of our economic system is based, by smoothly accompanying the inevitable depletion of oil reserves, whose first effects will already be visible between 2010 and 2020.