innovation Was te Heat Recovery Improving Comercial Vehicle Fuel Eficiency Reduction of fuel consumption for commercial powertrains has always been a high priority. Consequently, traditional optimization potentials like combustion system optimization or friction reduction seem to be mostly exhausted. However, a new opening seems to be the recovery of waste heat. From the various possibilities of waste heat recovery investigated by AVL, the Rankine cycle has been selected as the likely solution for commercial vehicle applications. After intensive simulation and concept evaluations AVL demonstrated the real world fuel saving potential of such a WHR system on a HD truck engine meeting Euro VI emissions norms. The system tested included one evaporator replacing the EGR cooler and a second evaporator in the exhaust system, downstream of the aftertreatment system. A piston expander was selected allowing flexible operation with regard to choice of working fluid and waste heat sources. 2 6 F o c u s working fluid as well as the chosen hardware. It has been demonstrated that a fuel efficiency improvement of more than 5% can be realized by applying such a WHR system. This was possible even on a highly optimized commercial vehicle engine. Consequently it can be assumed that this technology will be applied by OEMs to further improve fuel efficiency respectively to further reduce Total Cost of Ownership for the end customer. The WHR technology can be applied for both, on-road as well as off-road applications. However, the achievable efficiency gains will depend on the individual load cycle of the application, whereas cycles with a high load factor will provide the highest potential. Based on the results achieved, AVL is continuing to industrialize the WHR system for commercial engines and to develop the technology towards series production implementation. < After comprehensive evaluations, both, water and ethanol were used as working fluids. In order to fully exploit the potential of the WHR system under real world conditions the development also included a WHR control system for the transient control of the entire system. This was calibrated to achieve the highest efficiency gain in the system, as well as to manage appropriate system durability under transient operation. A key part of the developed closedloop > It has been demonstrated that a WHR system can deliver a fuel efficiency improvement of more than 5 percent can be. model based functionality are virtual sensors (models) controlling the mass flow for the EGR and exhaust steam generators. The developed control software can be applied independently from the selected > Heimo Schreier, Product Manager Commercial Powertrain Systems
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