An Investigation into The Development of an Electrically Assisted Turbocharger with Energy Recovery

An experimental electrically boosted turbocharger system has been developed for a small motorcycle engine intended for use in Formula Student competitions. The system was developed and tested to produce elevated levels of torque at low engine speeds through the use of computer simulations validated by dynamometer testing.

This research took a standard inline two-cylinder engine with a displacement of 471cc and improved its torque output throughout the speed range. The engine was considered as originally designed, in a naturally aspirated state, then modified to be turbocharged, both the NA and the turbocharged engine being simulated and tested. There was less than 5% error between the simulation and test, therefore the simulation was considered suitable as a basis for further development and the turbocharger was modified to accommodate for a 9kW electric motor.

Results from the simulation show that there is a 25% increase in torque at engine idle for the electrically boosted turbo system. Furthermore, the electro-turbocharger engine starts to produce boost pressure at 5500rpm, with the system producing 0.19 bar of gauge boost pressure at engine idle. The same amount of pressure is not produced by the standard turbocharged engine until 6800rpm. The electrically boosted turbocharger system was used to overcome design issues such as turbo-lag and torque levelling. The optimised design demonstrates significant improvements in engine torque and driveability.