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Ricardo

Neville Jackson, Ricardo technology director


How will biofuels affect the engine of 2018?

Bio-mass will make up an increasing proportion of the fuels used in the transport sector and by 2018 could reach around 10% of total content. The majority of this is likely to be blended into conventional oil based fuels and used by the total vehicle parc. We also believe that increases in biofuel content must be based on second-generation biofuels that are more carbon efficient and do not compete with the food supply chain. The blended fuels, if produced with low biofuel content, are unlikely to affect the design of the base engine. However, it is likely that fuel systems will change over time to be more tolerant to biofuel content. At higher biofuel concentrations (such as E85) the engine requires changes to the calibration due to significant variations in energy density and in this respect we would expect the new engines of 2018 to be feature flex-fuel capability across a wide spectrum of bio-fuels, with fuel-sensing adaptive calibrations ensuring that drivers have predictable, uniform and reliable performance.

How big will engines be in 2018?

We expect the recent increases in the specific power of diesel and gasoline engines to continue for some time to come, enabled by more capable and flexible boosting systems. This offers the prospect of aggressive downsizing to reduce friction losses, providing an improvement in fuel economy. Downsizing combined with hybridization is also an effective strategy to improve fuel economy. We are already seeing the diminishing use of engine capacity as a marketing device for new vehicles. By 2018 customers will be more used to making purchase decisions based on quoted figures of power, torque and fuel economy, with engines downsized and with fewer cylinders than today’s equivalents.

What sort of valve train/induction developments do you expect?
Both diesel and gasoline engines will tend to incorporate more complex air handling and valve train systems. Between now and 2018 the challenge for diesel will be to remain competitive on price while achieving ultra-low NOx and lower fleet-averaged CO2. We have demonstrated the feasibility of a diesel engine offering a competitive power rating of 65kW/l but with test bed engine-out NOx levels within US Tier II/Bin 5 limits (roughly equivalent to one-sixth those of Euro 5). This was based on the use of two-stage series-sequential turbocharging and advanced exhaust gas recirculation, together with closed-loop cylinder pressure-based engine controls. Our objective is to mix engine technologies such as these with appropriate aftertreatment systems in order to deliver cost-optimized solutions tailored for the specific needs of each market and vehicle segment.

For gasoline engines the challenges is driven squarely by the need to improve fuel economy, closing the cap on diesel while aiming to maintain its inherent price advantage. Air handling systems will look increasingly similar between gasoline and diesel, with use of boosting far more commonplace. Charge dilution is likely to be used on many engines as a means of boosting fuel economy, using excess air or EGR, the latter to avoid the necessity for NOx aftertreatment with its associated costs. Synergies between valvetrain concepts and DI combustion are also likely to be apparent in the 2018 product portfolio, using cam phasing, cam-profile switching and variable valve-lift systems.

How will combustion strategies develop?

The use of closed-loop cylinder pressure based engine control systems and strategies is likely to be commonplace by 2018 as an enabler for combustion efficiency and emissions reduction improvement efforts. Modeling and simulation techniques have made rapid progress in the past 10 years and when combined with advanced electronic systems, will enable model based closed loop systems to run in real time as a basis for engine hardware control. This approach can substantially reduce calibration effort and also enables adaptive tolerance to variations in fuel specification and component wear, ensuring optimum operation for the life of the engine.

In general, diesel combustion systems will follow a trend of generally lower compression ratio, higher fuel injection pressures, and cooler combustion using super cooled EGR. For gasoline engines the synergic use of advanced valvetrain technologies, downsizing, boosting, charge dilution and controlled auto-ignition for part of the duty cycle is likely to be used in dependent on individual product and market niche needs. It is unlikely that we will see a combined diesel and gasoline engine by 2018 as extremes of operation require different combustion regimes for each fuel, but part load operating strategies are likely to be very similar.

What will be the cutting edge engine technology of 2018?

This is perhaps the most difficult question to answer other than to say that tomorrow’s state-of-the-art is likely to at least in part be driven by today’s advanced research. As such, advanced concepts such as the highly downsized 2/4SIGHT engine may feature amongst the cutting edge product technologies of the day. This concept uses a direct-injection gasoline combustion system in which the design of intake and exhaust ports, combined with appropriate changes in fuel injection, ignition and valve timing, enable operation both in two-stroke and four-stroke modes. Through the use of an advanced valvetrain and a sophisticated control system to manage driver demands and coordinate operation of the boost and charge air system together with the valves and fuel injection equipment at an individual cylinder level, smooth transitions between two- and four-stroke operation without torque interruption have been shown to be possible. The drive to improved efficiency may also result in more complex thermodynamic cycles, with many more systems recovering waste exhaust energy. Ricardo has been active in these more complex cycles for many years enabling substantial improvements in thermal efficiency. These types of systems are more likely to appear in larger marine engines initially but could appear in long haul truck applications by 2018.

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