Assessment of waste heat recovery system for automotive engine with weight effect

Abstract

As additional weight leads to work loss in vehicles, the effect of weight on the final net power output of waste heat recovery (WHR) systems for automotive engines must be considered. In previous studies, it was difficult to directly evaluate the effect of weight from the theoretical weight of undeveloped WHR systems. Therefore, this study proposes an antidromic approach to determine the maximum allowable weight, which can be used as a reference for optimizing the weight and manufacturing WHR systems. A CO2-based transcritical power cycle (CTPC) with four different configurations was used as the WHR system, and the system was simulated under the overall conditions of a gasoline engine. From the system aspect, the proposed assessment method could obtain the maximum allowable weight of CTPC systems when producing a considerable output, as well as the maximum weight limit when the negative effect of the CTPC weight is equal to the positive effect of the CTPC output. From the component aspect, as additional components (preheater and regenerator) increase both the power output and work loss due to the increase in weight, the assessment method can also be used to evaluate whether additional components benefit the WHR system.