An opportunity to discuss turbocharger usage and design with Softinway engineer Ursula Shannon in a question and answer format:
What are some of the major current turbocharger design challenges?
When it comes to turbocharger design, there are two challenges that engineers generally face. “Turbo lag” and turbo boost power at varying engine RPMs. “Turbo lag” is the time that it takes for the engine to produce enough exhaust to start the turbocharger “working”. This can vary greatly depending on engine size, turbocharger geometry, exhaust output etc. Ideally, engineers want to reduce this “Turbo lag” by as much as possible in any given situation, as during that time, the exhaust is “wasted” in a sense. Finding the most efficient configuration with all of the parameters in mind can be a very challenging scenario from a design perspective.
The turbo boost design challenge is one of efficiency at variable exhaust outputs. A smaller charger for example will start to boost at lower engine speeds while a larger one will start to boost at engine speeds. The trade off however is that a smaller turbo will start to create what is known as back pressure at higher speeds, and this results in a loss of potential power. A larger turbocharger, will be able to create more overall boost at higher speeds, however the “Turbo Lag” is more pronounced as more engine exhaust is required. Minimizing these trade offs is another key challenge in turbocharger design.
Finally, the process of turbocharger design process itself is complex, and requires highly specialized software such as our own here in Softinway (AxSTREAM).
AxSTREAM Turbocharger Design Software ( Flowpath Design and Optimization )
AxSTREAM Turbocharger Design Software (Compressor 1D Design and Analysis)
What are some design changes do you see coming to turbochargers in the future?
As I mentioned some of the challenges engineers face in turbocharger design, currently many technologies and methods are being developed to alleviate some of the issues faced.
Two stage turbochargers are good example of trying to offer a solution to the boost powers at varying engine outputs, using a smaller turbocharger that operates at low RPMs and a larger turbocharger that operates at higher RPMs.
Electronic energy storage setups are currently being developed and used in European race cars which uses the output side of the turbocharger as a sort of generator which stores energy in a battery from turbocharger operations and acts as a boost during a turbocharger’s lag period.