Further analysis of a compression-expansion machine for a Brayton Waste Heat Recovery cycle on an IC engine

Abstract

In order to comply with the legislation, car manufacturers are looking for a way to lower the CO2 emission by improving engine efficiency. About one third of the fuel combustion energy is wasted through exhaust gasses. Waste Heat Recovery (WHR) could improve engine efficiency by recovering a part of exhaust gasses energy. In this study, the potential use of an open loop Brayton cycle with a volumetric compression expansion machine for exhaust gas waste heat recovery was investigated. The use of the Brayton cycle system with only two main elements, a heat exchanger and a volumetric machine, could be very interesting due to its compactness and versatility. However, the publications on this subject are scarce. The present paper aims at bridging this knowledge gap by studying the cycle viability for passenger car application characterized by low temperatures, variable working conditions and several restrictions of available space and weight. The simulated vehicle was a Ford Mondeo family car with an Ecoboost 2.0 engine. The main components of the Brayton cycle WHR system model were a heat exchanger and an alternating piston machine that was used both as a compressor and as an expander. Theoretical studies were conducted in the compression-expansion machine model in order to determine the main parameters that influence the cycle and optimise those parameters in order to obtain the maximum recuperated power. The conclusion was that the cycle viability is not clear because cycle losses are in the same order of magnitude as the recuperated power. Considering future improvements of the compressionexpansion machine and the heat exchanger, the recuperated power could be positive. Nevertheless, it is hard to expect that recuperated power would be sufficient to justify the application of this WHR system in the vehicle.

Expander Technologies for Automotive Engine Organic Rankine Cycle Applications

“…Recently, technologies to recover wasted heat in internal combustion engines have been studied intensively. According to the open literature [31][32][33][34], there are several common technologies in WHR; namely, the organic Rankine Cycle (ORC), Thermo-electric generation (TEG) [35], and turbo-compounding (TC) [36]. However, the investigation of TEG and TC is beyond the scope of this study.…”

Theoretical and experimental investigation of an absorption refrigeration and pre-desalination system for marine engine exhaust gas heat recovery

“…Marine diesel engines have been widely used as the primary power suppliers for fishing and merchant ships [1]. When a marine diesel engine operates in the zone of good efficiency, only 30-45% of the energy obtained by fuel combustion can be transferred into shaft power output [2][3][4], while approximately one third of the energy is wasted along with the exhaust gases [5]. Consequently, the waste heat recovery of engine exhaust gas is important for improving the fuel efficiency and achieving the goal of energy conservation in marine diesel engines [6,7].…”

Use of LNG Cold Potential in the Cogeneration Cycle of Ship Power Plants

“…The Brayton cycle, because of its small size and mass and relatively easy integration into transport systems, is increasingly being used as a versatile tool to improve energy efficiency and eco-efficiency and to practically reduce the CO 2 emissions of internal combustion engines of all purposes [63][64][65][66][67].…”

“…In automotive transport, the Brayton cycle is used for either traditional oil-based fuel-driven transport means (ICEs) [67] or electric transport [66]. Because of multi-variability, the parametric optimization of the cycle is performed using mathematical modeling methods.…”

“…For natural gas (NG)-powered transport, even more opportunities to increase the energy efficiency of recovery systems exist. This is primarily applicable to maritime transport because of large engine rooms, which have sufficient space to install the systems of Rankine and Brayton cycles [65][66][67][68].…”