Internal Combustion Engine Waste Heat Research Articles

Review of Organic Rankine Cycles for Internal Combustion Engine Waste Heat Recovery: Latest Decade in Review

The last decade (2013–2023) was the most prolific period of organic Rankine cycle (ORC) research in history in terms of both publications and citations. This article provides a detailed review of the broad and voluminous collection of recent internal combustion engine (ICE) waste heat recovery (WHR) studies, serving as a necessary follow-on to the author’s 2013 review. Research efforts have targeted diverse applications (e.g., vehicular, stationary, and building-based), and it spans the full gamut of engine sizes and fuels. Furthermore, cycle configurations extend far beyond basic ORC and regenerative ORC, particularly with supercritical, trilateral, and multi-loop ORCs. Significant attention has been garnered by fourth-generation refrigerants like HFOs (hydrofluoroolefins), HFEs (hydrofluoroethers), natural refrigerants, and zeotropic mixtures, as research has migrated away from the popular HFC-245fa (hydrofluorocarbon). Performance-wise, the period was marked by a growing recognition of the diminished performance of physical systems under dynamic source conditions, especially compared to steady-state simulations. Through advancements in system control, especially using improved model predictive controllers, dynamics-based losses have been significantly reduced. Regarding practically minded investigations, research efforts have ameliorated working fluid flammability risks, limited thermal degradation, and pursued cost savings. State-of-the-art system designs and operational targets have emerged through increasingly sophisticated optimization efforts, with some studies leveraging “big data” and artificial intelligence. Major programs like SuperTruck II have further established the ongoing challenges of simultaneously meeting cost, size, and performance goals; however, off-the-shelf organic Rankine cycle systems are available today for engine waste heat recovery, signaling initial market penetration. Continuing forward, next-generation engines can be designed specifically as topping cycles for an organic Rankine (bottoming) cycle, with both power sources integrated into advanced hybrid drivetrains.

Research on Gas Recycling of Free-Piston Expander–Linear Generator for Organic Rankine Cycle of Vehicle

A (FPE-LG) is a new type of vehicle waste heat recovery device based on an organic Rankine cycle. It is expected to achieve the reuse of vehicle internal combustion engine waste heat and improve the comprehensive utilization rate of energy. To enable the FPE-LG to recover exhaust gas to a greater extent in practical applications, based on the FPE-LG coupling gas storage tank test platform, the gas is discharged from the expander cylinder. This paper analyzes the influence of differences to the tank volume, intake pressure, intake duration time, expansion duration time and exhaust duration time on piston motion characteristics and gas storage and release time during the cycle, and verifies the feasibility of gas working as a recycling medium. The results showed that the energy storage of lithium batteries increases with the increase of intake pressure, and the energy stored in lithium batteries during gas release is higher than that during gas storage; the intake duration time, expansion duration time and exhaust duration time have little effect on the storage of lithium battery energy during the cycle. When the intake pressure is 0.5 MPa, the volume of the gas tank is 30 L, and the intake duration time, expansion duration time and exhaust duration time are 50 ms, 80 ms and 30 ms, respectively, the maximum actual stroke of the piston can reach 89.592 mm.

Thermodynamic Performance Analyses and Optimization of Dual-Loop Organic Rankine Cycles for Internal Combustion Engine Waste Heat Recovery

Waste heats of an internal combustion engine (ICE) are recovered by a dual-loop organic Rankine cycle (DORC). Thermodynamic performance analyses and optimizations are conducted with 523.15–623.15 K exhaust gas temperature (Tg1). Cyclopentane, cyclohexane, benzene, and toluene are selected as working fluids for high-temperature loop (HTL), whereas R1234ze(E), R600a, R245fa, and R601a are selected as working fluids for low-temperature loop (LTL). The HTL evaporation temperature, condensation temperature, and superheat degree are optimized through a genetic algorithm, and net power output is selected as the objective function. Influences of Tg1 on system net power output, thermal efficiency, exergy efficiency, HTL evaporation temperature, HTL condensation temperature, HTL superheat degree, exhaust gas temperature at the exit of the HTL evaporator, heat utilization ratio, and exergy destruction rate of the components are analyzed. Results are presented as follows: the net power output is mainly influenced by HTL working fluid. The optimal LTL working fluid is R1234ze(E). The optimal HTL evaporator temperature increases with Tg1 until it reaches the upper limit. The optimal HTL condensation temperature increases initially and later remains unchanged for a cyclopentane system, thus keeping constant for other systems. Saturated cycle is suitable for cyclohexane, benzene, and toluene systems. Superheat cycle improves the net power output for a cyclopentane system when Tg1 is 568.15–623.15 K.

Internal combustion engine waste heat recovery by a thermoelectric generator inserted at combustion chamber walls

Internal combustion engine waste heat recovery by a thermoelectric generator inserted at combustion chamber walls

A distributed energy system with advanced utilization of internal combustion engine waste heat

New trigeneration system consists of an internal combustion engine, a power and cooling cogeneration system and an absorption heat transformer system. The exhaust gas is recovered by the power and cooling cogeneration subsystem producing the cooling and power. The jacket water is recovered by the absorption heat transformer subsystem producing lowpressure steam. The exergy performance and the energy saving performance which is evaluated by the primary energy saving ratio of the new distributed energy system are analyzed. The effects of the ratio of the output power and cooling of the power and cooling cogeneration subsystem and the generator outlet temperature of the absorption heat transformer subsystem to the primary energy saving ratio are considered. The contributions of the subsystems to the primary energy saving ratio are quantified. The maximum primary energy saving ratio of the new distributed energy system is 15.8%, which is 3.9 percentage points higher than that of the conventional distributed energy system due to the cascade utilization of the waste heat from the internal combustion engine.

Thermodynamic analysis of dual-loop organic Rankine cycle using zeotropic mixtures for internal combustion engine waste heat recovery

The dual-loop organic Rankine cycle (DORC) is a promising technology for internal combustion engine waste heat recovery. Zeotropic mixtures can improve temperature matches with heat source and sink in the phase change process for its non-isothermal phase change characteristic. Thus, zeotropic mixtures are adopted for high-temperature loop (HTL) and low-temperature loop (LTL) of DORC. Cyclopentane/cyclohexane and benzene/toluene mixtures are used for HTL, whereas isobutane/isopentane (R600a/R601a) mixtures are selected as working fluids for LTL. The mole fraction effects of mixtures on net power output, exergy efficiency, exergy destruction rate (HTL evaporator, condenser/evaporator, LTL preheater, and condenser), and heat utilization ratio of waste heat are analyzed. The influences of engine exhaust gas temperature on net power output and exergy destruction rate are also discussed. Results show that the use of mixtures for the two loops can reduce the exergy destruction rate of HTL evaporator and LTL condenser compared to that of pure working fluids system and the exergy destruction rate of condenser/evaporator compared to that of mixtures using only one loop system. Furthermore, these mixtures increase the heat utilization ratio of waste heat, net power output, and exergy efficiency compared to those of a pure working fluid system. When cyclopentane/cyclohexane or benzene/toluene mixtures are used for HTL and R600a/R601a mixtures are used for LTL, the system net power output relative increment rates of mixture systems are 2.5–9.0% and 1.4–4.3%, respectively, compared to those of corresponding pure working fluids system with 573.15–623.15 K engine exhaust gas temperature.

Numerical analysis of a direct contact membrane distillation system using diesel internal combustion engine waste heat

Numerical analysis of a direct contact membrane distillation system using diesel internal combustion engine waste heat

A Combined Organic Rankine Cycle With Double Modes Used for Internal Combustion Engine Waste Heat Recovery

A combined organic Rankine cycle (ORC) was proposed for both engine coolant energy recovery (CER) and exhaust energy recovery (EER), and it was applied to a gasoline direct injection (GDI) engine to verify its waste heat recovery (WHR) potential. After several kinds of organic working medium were compared, R123 was selected as the working fluid of this ORC. Two cycle modes, low-temperature cycle and high-temperature cycle, were designed according to the evaporation way of working fluid. The working fluid is evaporated by coolant heat in low-temperature cycle but by exhaust heat in high-temperature cycle. The influence factors of cycle performance and recovery potential of engine waste heat energy were investigated by cycle simulation and parametric analysis. The results show that recovery efficiency of waste heat energy is influenced by both engine operating conditions and cycle parameters. At 2000 r/min, the maximum recovery efficiency of waste heat energy is 7.3% under 0.2 MPa brake mean effective pressure (BMEP) but 10.7% under 1.4 MPa BMEP. With the combined ORC employed, the fuel efficiency improvement of engine comes up to 4.7% points under the operations of 2000 r/min and 0.2 MPa BMEP, while it further increases to 5.8% points under the operations of 2000 r/min and 1.4 MPa BMEP. All these indicate that the combined ORC is suitable for internal combustion (IC) engine WHR.

A Commander–Tracker–Executor based energy management framework for an engine waste heat recovery system

Energy management for an internal combustion engine waste heat recovery system presents a complex problem. There are the coupling issues of energy recovery and energy utilization. In addition, there are the problems arising from the large thermal inertia of the energy network. A Commander–Tracker–Executor energy manager framework is proposed as the management solution. Under this approach the Commander is designed to optimally split the engine’s exhaust energy among the different energy devices of the energy network at the lowest fuel cost. A disturbance estimation-based receding horizon controller is designed as a Tracker to follow the Commander’s commands in real time. The Commander’s decisions are made in real time based on each energy device’s efficiency model, the torque demand given by the driver, and the corresponding heat rejection requirement of the whole system. The Tracker works as a trajectory follower to transform the Commander’s decisions into the actuators’ control objectives. The Executor ensures that the energy management goals are achieved in line with the actuators’ control objectives. An energy network constructed of <Engine>- <Power Turbine>- <Organic Rankine Cycle System>- <Electric Cooling system>- <Battery>- <Integrated starter and Generator> has been taken as an example for the simulation study. The simulation results indicate that: the manager exhibited fairly good fuel-saving potentiality along a whole driving cycle; the proposed Commander showed effective exhaust energy splitting performance; and the Tracker scheme demonstrated good tracking capability and robustness.

Technology competition in the internal combustion engine waste heat recovery: a patent landscape analysis

Fuel prices and tightening emission standards have challenged the dominance of internal combustion engines. As a response to this changed business context, the automotive industry has shown active interest in waste heat recovery technologies, which have seen rapid development in recent years. This paper uses a literature review and patent landscape analysis to study key emerging technologies in the field, namely, thermoelectric generators, and Rankine cycle and organic Rankine cycle systems. The state-of-the-art review highlights the challenges, advantages and future prospects of the selected technologies. The patent analysis reveals the leading countries, principal technological development indicators and most important actors active in the field. The results indicate a growing trend of patenting in all selected technologies. The United States and Japan are by far the most dominant countries in the waste heat recovery area, although their relative share of patent applications is declining. By applying a patent landscape approach, the study offers a quantitative perspective on current developments in waste heat recovery technology, provides indicators of future trends, and contributes to debate about technological competition in the automotive industry. Based on the conducted analyses, thermoelectric generators seems to be the most developed of the alternatives and closest to commercial application. Rankine cycle-based technologies, although less well developed, potentially offer greater environmental gains and better efficiency than thermoelectric generators. The study provides valuable information for stakeholders interested in waste heat recovery technologies and gives policymakers perspectives regarding different technological options in development of cleaner engine solutions.

Experimental and simulative investigation of a micro-CCHP (micro combined cooling, heating and power) system with thermal management controller

A micro-CCHP (micro combined cooling, heating and power) system is proposed and investigated. It mainly consists of an internal combustion engine (ICE), an adsorption chiller (AD), a thermal management controller (TMC) and some other devices. The waste heat of ICE is collected and managed by the TMC. So the waste heat can be automatically assigned to different water cycles for heating, cooling, or to be released. Considering the complexity of micro-CCHP system, both experiment and simulation are conducted. Firstly, the experimental system and methodologies are described in detail. Then, simulation models of ICE and AD are proposed in order to simulate the system performance. Based on results of experiment and simulation, system characteristics for heating and cooling are investigated. Some influence factors are taken into account, such as the part load ratio of ICE, buffer tank set point temperature, hot water tank set point temperature, chilled water temperature and cooling water temperature of AD. Results show that the system can realize 17.7 kW heating output, 6.5 kW cooling output and 16 kW electric output simultaneously. The experimental primary energy ratio reaches 0.765 in heating mode and 0.56 in cooling mode.

Internal combustion engine waste heat potential for an automotive absorption system of air conditioning Part 1: tests on the exhaust system of a spark-ignition engine

AbstractMeasurements have been carried out on a four-cylinder spark-ignition engine to estimate the amount of heat recoverable in particular when the engine runs at low loads. Such heat is sufficient to feed an absorption cooling system for car air conditioning when the speed is over a threshold value. Data for the design of a heat recovery system are reported and discussed.

Internal combustion engine waste heat potential for an automotive absorption system of air conditioning Part 2: the automotive absorption system

AbstractAn automotive air conditioning system based on absorption cycles has been studied. Such a system uses the recovered heat available in the engine exhaust gas. The lithium bromide-water pair is recommended as the working mixture owing to its present technological application level. A possible arrangement of the absorption system for this purpose is proposed. The suitability of such a system has been investigated, taking operating conditions and other standard requirements into account. Finally, the particular features of the proposed scheme are pointed out, and a borderline (at least in stationary conditions) is located in the power-velocity diagram.

Internal combustion engine waste heat potential for an automotive absorption system of air conditioning Part 2: The automotive absorption system

An automotive air conditioning system based on absorption cycles has been studied. Such a system uses the recovered heat available in the engine exhaust gas. The lithium bromide-water pair is recommended as the working mixture owing to its present technological application level. A possible arrangement of the absorption system for this purpose is proposed. The suitability of such a system has been investigated, taking operating conditions and other standard requirements into account. Finally, the particular features of the proposed scheme are pointed out, and a borderline (at least in stationary conditions) is located in the power-velocity diagram.

Internal combustion engine waste heat potential for an automotive absorption system of air conditioning Part 1: Tests on the exhaust system of a spark-ignition engine

Measurements have been carried out on a four-cylinder spark-ignition engine to estimate the amount of heat recoverable in particular when the engine runs at low loads. Such heat is sufficient to feed an absorption cooling system for car air conditioning when the speed is over a threshold value. Data for the design of a heat recovery system are reported and discussed.