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Recovering heat from exhaust gases using the Rankine thermodynamic cyclea is one of the avenues being explored to reduce the energy consumption of IC engines.

Tried and tested for stationary applications, such as power plants, this technology becomes highly complex for transport applications due to extremely transient operating conditions, making an efficient supervision and control system essential.

Three application scenarios have been considered by IFPEN’s teams:
 

  • light-duty vehicles
      
  • trucks,
      
  • and diesel-electric railcarsb.
     

For each scenario, the design of a pilot Rankine system required new model-based control developments:
 

  • for the control of superheating at the evaporator outlet (see figure): a new non-linear command law, enabling temperature and pressure control, was proposed;
       
  • for the energy supervision of the Rankine system: a dynamic optimization approach, enabling the calculation of control setpoints as a function of operating conditions, was developed to maximize energy efficiency.

 

Régulation de surchauffe, sortie évaporateur
Superheating control, evaporator outlet.

 

Experimental validation of the system demonstrated that it could be maintained in conditions enabling continuous energy recovery, even over highly dynamic road cycles(1). It was thus verified that the improvement in energy saving associated with real-time dynamic optimization was significant compared to existing technology (+ 7 %)(2).

This pioneering work now represents a benchmark in the sector of Rankine system control.
 


a- Adiabatic cycle enabling the conversion of heat into mechanical work.
    
b- The latter have been the focus of co-development with Enogia.

 

(1)  J. Peralez, M. Nadri, P. Dufour, P. Tona, A. Sciarretta. Organic Rankine Cycle for Vehicles: Control Design and Experimental Results - IEEE Transactions on Control Systems Technology, 2017, 25(3), pp. 952 - 965. 
>> DOI: 10.1109/TCST.2016.2574760
    
(2)  J. Peralez, P. Tona, M. Nadri, P. Dufour, A. Sciarretta. 
Optimal control for an organic rankine cycle on board a diesel-electric railcar - Journal of Process Control, vol. 33, 2015, pp. 1-13, ISSN 0959-1524. 
>> DOI : 10.1016/j.jprocont.2015.03.009


Scientific contact: paolino.tona@ifpen.fr

>> ISSUE 30 OF SCIENCE@IFPEN