Analyzing the Performance of a Dual Loop Organic Rankine Cycle System for Waste Heat Recovery of a Heavy-Duty Compressed Natural Gas Engine

Abstract

A dual loop organic Rankine cycle (DORC) system is designed to recover waste heat from a heavy-duty compressed natural gas engine (CNGE), and the performance of the DORC-CNGE combined system is simulated and discussed. The DORC system includes high-temperature (HT) and low-temperature (LT) cycles. The HT cycle recovers energy from the exhaust gas emitted by the engine, whereas the LT cycle recovers energy from intake air, engine coolant, and the HT cycle working fluid in the preheater. The mathematical model of the system is established based on the first and second laws of thermodynamics. The characteristics of waste heat energy from the CNGE are calculated according to engine test data under various operating conditions. Moreover, the performance of the DORC-CNGE combined system is simulated and analyzed using R245fa as the working fluid. Results show that the maximum net power output and the maximum thermal efficiency of the DORC system are 29.37 kW and 10.81%, respectively, under the rated power output condition of the engine. Compared with the original CNG engine, the maximum power output increase ratio and the maximum brake specific fuel consumption improvement ratio are 33.73% and 25%, respectively, in the DORC-CNGE combined system. OPEN ACCESSEnergies 2014, 7 7795

Energy and Exergy Analysis of Different Exhaust Waste Heat Recovery Systems for Natural Gas Engine Based on ORC

“…They concluded that variations in engine rotational speed must be determined to evaluate the true performance of the combined system.Regarding ORC and stationary compressed natural gas (CNG) engines integration, two approaches have been studied: the use of multiple temperature loops for WHR from the engine intercooler, cooling system, and exhaust gases, and the use of single-temperature loops for WHR from engine exhaust. Within the first approach, Yao et al [12] were the first ones to propose an ORC system for WHR from the engine intercooler, exhaust gases, and cooling system by using a low and a high-temperature loop. Their ORC system used R245fa and achieved 10.8% thermal efficiency and 26.9 kW of power, which increased overall power production by 33.7%, keeping the same fuel consumption.…”

Ideal Point Design and Operation of CO2-Based Transcritical Rankine Cycle (CTRC) System Based on High Utilization of Engine’s Waste Heats

“…While, engine coolant is a relative low grade waste heat, whose temperature is below 100 • C, but still significant due to the comparative amount of waste heat [2]. Using a thermodynamic cycle to generate extra power is a high-efficiency way among the technologies of E-WHR, mainly including single-loop organic Rankine cycle (ORC) [3,4], dual-loop ORC [5,6], steam Rankine cycle [7,8], CO 2 -based transcritical Rankine cycle (CTRC). Moreover, thermodynamic cycle is a feasible scheme to make a combined recovery of exhaust gas and engine coolant.…”

Working fluid selection for an Organic Rankine Cycle utilizing high and low temperature energy of an LNG engine

“…Their another related work estimated that ORCturbocompounding results in FCE improvements of 10% while maintaining the essential low NOx characteristics of ALPING combustion [14]. B. Yao [16]designed a dual loop organic Rankine cycle system for waste heat recovery of a heavy-duty compressed natural gas (CNG) engine, in which cycle R245fa was used as the working fluid. Together with B. Yao, S. Song et al [17] designed a set of ORC systems with internal heat exchanger to recover exhaust energy of a stationary compressed natural gas engine.…”

“…There are only a few works concerning about ORC combining natural gas engines [13][14][15][16][17]. K. K. Srinivasan et al [13] examined the EWH recovery potential from an advanced Low Pilot Ignited Natural Gas (ALPING) low temperature combustion using a bottoming ORC.…”