Reciprocating Expander for an Exhaust Heat Recovery Rankine Cycle for a Passenger Car Application

Abstract

Nowadays, on average, two thirds of the fuel energy consumed by an engine is wasted through the exhaust gases and the cooling liquid. The recovery of this energy would enable a substantial reduction in fuel consumption. One solution is to integrate a heat recovery system based on a steam Rankine cycle. The key component in such a system is the expander, which has a strong impact on the system’s performance. A survey of different expander technologies leads us to select the reciprocating expander as the most promising one for an automotive application. This paper therefore proposes a steady-state semi-empirical model of the expander device developed under the Engineering Equation Solver (EES) environment. The ambient and mechanical losses as well as internal leakage were taken into account by the model. By exploiting the expander manufacturer’s data, all the parameters of the expander model were identified. The model computes the mass flow rate, the power output delivered and the exhaust enthalpy of the steam. The maximum deviation between predictions and measurement data is 4.7%. A performance study of the expander is carried out and shows that the isentropic efficiency is quite high and increases with the expander rotary speed. The mechanical efficiency depends on mechanical losses which are quite high, approximately 90%. The volumetric efficiency was also evaluated

Performance Analysis of a Reciprocating Piston Expander and a Plate Type Exhaust Gas Recirculation Boiler in a Water-Based Rankine Cycle for Heat Recovery from a Heavy Duty Diesel Engine

“…However, it should be possible to maintain a given expander power output while reducing the expander's speed (and thus the impact of friction) and also reducing the live steam pressure by up to 30%. These findings clearly confirm how sensitive the performance of a piston expander is to both its design and the applied system pressures, as it was previously concluded by other groups in the field [19,20]. boiler's maximum steam delivery rate of around 10-15 g/s.…”

“…The overall expander efficiency peaked at values of 50%, which is on the lower end compared to the results presented by other researchers [19][20][21]. Beside the non-optimal expander design, one reason for a lower efficiency might be that the results in this study describe the overall expander efficiency, which includes the mechanical losses.…”

Sizing models and performance analysis of volumetric expansion machines for waste heat recovery through organic Rankine cycles on passenger cars

“…It is based on the model developed in [12]. The same phenomena as those described above are expected to occur within this machine.…”

Study on Mixed Working Fluids with Different Compositions in Organic Rankine Cycle (ORC) Systems for Vehicle Diesel Engines

“…El-Emam et al [10] analyzed the thermodynamic and economic performances on a geothermal regenerative ORC system. Several scholars have considered the use of ORC systems to recover engine waste heat [11][12][13][14]. Domingues et al [15] evaluated the vehicle exhaust waste heat recovery potential by using a Rankine cycle.…”