Abstract

In this study, a methodology for optimal sizing of waste heat recovery (WHR) systems is presented. It deals with dynamic engine conditions. This study focuses on Euro-VI truck applications with a mechanically coupled Organic Rankine Cycle-based WHR system. An alternating optimization architecture is developed for optimal system sizing and control of the WHR system. The sizing problem is formulated as a fuel consumption and system cost optimization problem using a newly developed, scalable WHR system model. Constraints related to safe WHR operation and system mass are included in this methodology. The components scaled in this study are the expander and the EGR and exhaust gas evaporators. The WHR system size is optimized over a hot World Harmonized Transient Cycle (WHTC), which consists of urban, rural and highway driving conditions. The optimal component sizes are found to vary for these different driving conditions. By implementing a switching model predictive control (MPC) strategy on the optimally sized WHR system, its performance is validated. The net fuel consumption is found to be reduced by 1.1% as compared to the originally sized WHR system over the total WHTC.

Highlights

  • Optimal sizing of the waste heat recovery (WHR) system is necessary to maximize the WHR power output and fuel economy of the vehicle. This is challenging, since there are many factors that affect the optimality of WHR system size, including: driving conditions, system constraints, and the control strategy

  • The standalone WHR system with feed forward controller is simulated on a 3D design grid of different sizes of exhaust gas recirculation (EGR) evaporator, exhaust evaporator and expander for a hot-start World Harmonized Transient Cycle (WHTC)

  • For the purpose of benchmarking, the optimal component sizes associates with the two different optimization criteria are compared for a mass constraint equal to the original mass of the system: Mmtotax = 210 kg, which is indicated in the plots of Figure 10 by the blue vertical lines

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Summary

Introduction

Heavy-duty (HD) engines are the workhorse in the transport sector. Driven by societal concerns about global warming and energy security, this sector faces enormous challenges to dramatically reduce green house gas emissions and fuel consumption over the upcoming decades. In the EU, CO2 legislation for HD vehicles is in preparation. For 2050, a 60% CO2 reduction sectorial target is set

80 Organic Rankine Cycle Technology for Heat Recovery
System description
General problem definition
Optimization methodologies
Feedforward pump control
Scalable WHR system model
Expander
Evaporators
WHR system size optimization
Objective functions
Sizing optimization problem
Sizing optimization for different system mass
Best WHR sizing per objective function
Selected optimal scaling of WHR components
Simulation results
Findings
Conclusions
Full Text
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