iTurbo: Exhaust Energy Recovery in Low Carbon Vehicles by Intelligent Turbocharging

Low Carbon Vehicles and challenging emissions standards are pushing the engine boosting system beyond the limits of current technology with the aim to aggressively downsize the internal combustion engine. This approach is one of the most promising engineering solutions to achieve a rapid, large scale decarbonisation of road transport. However, a detailed analysis of turbocharging options and matching techniques for the future gasoline and diesel engines is essential if we expect to meet the needs of heavily downsized engines and future hybrid power trains (including range extenders). The actual state of the art for downsizing has moved towards the introduction of more complex systems; such as double stage turbo system, a combination of turbocharger and volumetric compressor or electric assisted supercharger/turbocharger combination. These go well beyond the traditional optimization of single stage turbocharger. Energy utilisation can be improved in all these cases if the turbocharger design/selection is taken in the context of its true operating environment by carefully considering the unsteady flow energy contained in the exhaust engine stream. This proposal addresses recognised boosting needs in two fundamental manners. Firstly, it will propose methods for the treatment of turbocharger selection in the direction of enhanced energy recovery at present not embedded in the selection, matching and design process of engine technology. Secondly, it will investigate and propose the transfer to the automotive industry of the concept of active control in turbocharger operation by means of pulse matching techniques, developed in the Turbocharger Group at Imperial College London.iTurbo is focused on future air management strategies to make low carbon engine technologies harness the available exhaust energy in reciprocating engines. The state of the art in design and engine air management only makes use of the steady turbomachinery component maps, thus forcing the design, matching and eventual installation along lines of quasi-steady operation. Critically, such an approach does not harness the full energy potential contained in an unsteady flow. This study will therefore investigate the potential for a better selection of air management components (compressor, turbine, electric assisted, superchargers, etc) in view of the reality of a fully pulsating exhaust flow.One novel potential technology to be assessed in this study is the Active Flow Control Turbocharger (ACT) developed by the proposer's group. This technology has been the basis of an EPSRC grant and a Carbon Trust Incubator award; it still remains laboratory based and has not shown its potential at engine level. In this patented technology, a Variable Geometry Turbine (VGT) turbocharger system is tuned to follow the engine generated exhaust pulse by means of a fast actuated nozzle. It aims to make better use of the exhaust gas energy of the engine than in current VGT turbochargers. The appeal and ultimate transfer of this technology to the automotive industry will only be made possible once the predicted gains of engine performance are made apparent. It therefore needs the close collaboration and integration of turbocharger developers to ensure a clear commercial path for the technology implementation. In order to address this final need, the current feasibility study includes time for interactions with turbocharger developers and OEMs to explore the implementation of the technology in future development programs.

The project's impact statement may be summarised as: * To achieve quantified reduction of CO2 emissions through the introduction of the Active Control Turbocharger (ACT) and the assessment of practical areas for further development prior to its implementation (reliability, serviceability and robustness). * To achieve a quantified reduction of CO2 emissions through improvements in engine/turbocharger matching through the reliable integration of flow unsteadiness into the design and selection process for turbochargers. * To develop closer relation between the OEMs and the turbocharger developers to address the key boosting technologies and unsteady considerations associated with their application in the light of the more complex systems proposed.