Charged air loop of the engines. Between engine performance and pollutant emission reduction

When charge air coolers were first introduced in the 1990s, the heat exchanger was sized as a simple component defined simply by its thermal output and pressure drop, a function of intake air flow and air velocity at the front of the vehicle.

The latest engine improvements in terms of fuel economy and compliance with increasingly stringent anti-pollution standards have led to a growing need for charge gas cooling. The introduction of the harmonized WLTC (Worldwide harmonized Light vehicles Test Cycle) cycle, followed by the RDE (Real Driving Emissions) cycle, will accentuate this trend by increasing the rate of use of recycled gases (or external dilution, more commonly known by the acronym EGR for Exhaust Gas Recirculation) on more heavily loaded engine points.

CO ₂ -neutral mobility is the key phrase of the contemporary automotive industry. Moving from carbon-intensive to carbon-neutral mobility cannot be achieved in the very short term; that's why automakers and equipment manufacturers are still working on improving combustion engines to reduce their carbon impact. In future, CO ₂ and, more generally, greenhouse gases will have to be assessed by taking into account the entire life cycle from cradle to grave. But for the moment, only CO ₂ from the tailpipe is taken into account. This is why the energy efficiency of the Internal Combustion Engine (ICE) must be further improved when it is still needed, or simply switched off when another device has the capacity to provide propulsion on its own. This is the golden rule for future hybrid powertrains.

Diesel engines, which are still very competitive in this respect, are now technically ready to comply with future emissions regulations; SCR technologies, Water Charge Air cooling (WCAC) coupled with low- and high-pressure EGR are now widely available on the market, and play a full part in resolving the weaknesses of diesel engines. In any case, the current debate surrounding restrictions on the use of this type of engine has forced automakers and equipment manufacturers to work on the gasoline engine, in order to reinforce the potential of spark-ignition MCI technology, but also to document the possibility of using alternative fuels (ethanol, gas, e-fuel synthetic fuels, hydrogen).

The trend towards engine downsizing and downspeeding is clearly forcing engine manufacturers to better integrate the downstream compressor gas cooling function, for which new requirements and functionalities are emerging, such as :

• a significant reduction in pressure drop in order to increase pressure upstream...