Fuel Economy Benefits for Commercial Diesel Engines with Waste Heat Recovery 2015-01-2807

In the near future engine emitted carbon dioxides (CO₂) are going to be limited for all vehicle categories with respect to the Green House Gases (GHG) norms. To tackle this challenge, new concepts need to be developed. For this reason waste heat recovery (WHR) is a promising research field.

For commercial vehicles the first phase of CO₂ emission legislation will be introduced in the USA in 2014 and will be further tightened towards 2030. Besides the US, CO₂ emission legislation for commercial engines will also be introduced in Europe in the near future. The demanded CO₂ reduction calls for a better fuel economy which is also of interest for the end user, specifically for the owners of heavy duty diesel vehicles with high mileages. To meet these future legislation objectives, a waste heat recovery system is a beneficial solution of recovering wasted energies from different heat sources in the engine. Specifically the considerable amount of exergy in the exhaust gas, which results from its high temperature and mass flow, has a large recovery potential. By utilizing a waste heat recovery system a portion of this exergy can be converted into an effective power form, which then will be used as entire engine power output. The major challenge ahead is the recovery of the wasted exhaust energy with the maximum possible system efficiency.

In this paper different technologies for waste heat recovery systems will be discussed and most feasible applications for the heavy duty and industrial engines will be shown. Furthermore an application of an Organic Rankine Cycle (ORC) as waste heat recovery system for commercial vehicles will be introduced. Additionally, an adequate working fluid and system layout, which are considered for thermodynamic calculations, will be in focus. The second major part of this paper will be the simulation work. In addition to the presentation of the simulation tools and system layouts, results for the fuel saving potential of a specific ORC application will be given.