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While the pressure to invest in electrified powertrains is unavoidable, you can’t simply drop overnight a technology that has powered our mobility for more than a century. So there is still a huge amount of research and development work being done to improve the combustion engine – whether petrol or diesel.
The basic principles of mixing fuel and air and then igniting it are unlikely to change, but the technologies that make up combustion engines are being honed, improved and advanced in significant areas.
Controlling cylinders
Whether an engine is four-, six- or eight-cylinder you don’t need them all if the vehicle is travelling at a steady state which is why firms have looked at using cylinder deactivation technology to improve performance and efficiency.
Volkswagen successfully used Cylinder on Demand systems in four-cylinder petrol engines, but now firms are looking at how the technology could benefit diesels too.
Supplier company FEV developed a Dynamic Skip Fire system – an advanced, software-based, cylinder deactivation technology – which has the ability to selectively deactivate cylinders on a cylinder event-by-event basis to match the torque demand at optimum fuel efficiency while maintaining acceptable levels of noise, vibration and harshness (NVH).
Gasoline direct-injection systems have allowed OEMs to better control fuel sprayed into the combustion chamber, but the race is now on to increase the pressures at which these systems work.
Tier-one supplier Delphi has had 350bar systems in series production since 2016 – a step up from older 200bar technology – but is now developing systems that work at 500bar. The advantage of these higher-pressure systems is that particulate numbers can be reduced, making powertrains far cleaner. The challenge is achieving higher pressures without placing an undeliverable burden on the fuel pump.
Intelligence is key
The number of sensors on passenger vehicles is increasing enormously as powertrain complexity grows, and the data that’s pulled in is being fed back into the development process to improve engine technology and also warn users of possible faults.
Mahle’s intelligent bearings track operating conditions in real time, providing accurate information about temperature in the system with data transmitted wirelessly to the user – whether an R&D department or garage mechanic.
The same measurement method forms the basis of the supplier’s piston monitoring concept. Crucially, the energy consumption of the sensors is covered by the motion of the piston via an energy-harvesting system, so it doesn’t put unnecessary additional demands on the powertrain.
So, whether it’s to refine the combustion process or warn users they need to head to their dealer, the number of sensors is only going to grow.
Varying the valvetrain
The valvetrain plays a critical role in the operation of any combustion engine, making sure it can adapt to whatever load is placed on it through precisely controlling the air/fuel mix.
Tier-one supplier Schaeffler has developed numerous technologies to help maximise efficiency, and has now introduced an electric cam phasing unit. It makes rapid adjustments based on speed and temperature and allows the valve timing to be optimised throughout the entire operating and temperature range.
This is important as hybrids become more commonplace, as internal combustion engines in these vehicles have to be started with significantly greater frequency. The electric cam phasing unit ensures that this process takes place quickly and efficiently and without having a negative impact on NVH.
Powertrain technology is likely to remain incredibly reliant on the combustion engine for decades to come, so making units as efficient, reliable and clean as possible will be critical.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.