The Benefits of an Inverted Brayton Bottoming Cycle as an Alternative to Turbocompounding

2015 ◽  
Vol 138 (7) ◽  
Author(s):  
Colin D. Copeland ◽  
Zhihang Chen
Keyword(s):  
Internal Combustion Engine ◽  
Thermal Efficiency ◽  
Heat Recovery ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Critical Parameters ◽  
Specific Power ◽  
Brayton Cycle ◽  
Exhaust Gas ◽  
Otto Cycle

The exhaust gas from an internal combustion engine contains approximately 30% of the thermal energy of combustion. Waste heat-recovery systems aim to reclaim a proportion of this energy in a bottoming thermodynamic cycle to raise the overall system thermal efficiency. The inverted Brayton cycle (IBC) considered as a potential exhaust-gas heat-recovery system is a little-studied approach, especially when applied to small automotive power plants. Hence, a model of an air-standard, irreversible Otto cycle and the IBC using finite-time thermodynamics (FTT) is presented to study heat recovery applied to an automotive internal combustion engine. The other two alternatives power cycles, the pressurized Brayton cycle and the turbocompounding system (TS), are compared with the IBC to specify the strengths and weaknesses of three alternative cycles. In the current paper, an irreversible Otto-cycle model with an array of losses is used as a base for the bottoming cycle. The deviation of the turbomachinery from the idealized behavior is described by the isentropic component efficiencies. The performance of the system as defined as the specific power output and thermal efficiency is considered using parametric studies. The results show that the performance of the IBC can be positively affected by five critical parameters—the number of compression stages, the cycle inlet temperature and pressure, the isentropic efficiency of the turbomachinery, and the effectiveness of the heat exchanger. There exists an optimum pressure ratio across the IBC turbine that delivers the maximum specific power. In view of the specific power, installing a single-stage of the IBC appears to be the best balance between performance and complexity. Three alternative cycles are compared in terms of the thermal efficiency. The results indicate that the pressurized and IBCs can improve the performance of the turbocharged engine (TCE) only when the turbomachinery efficiencies are higher than a value which changes with the operating condition. High performance of the IBC turbomachinery is required to ensure that the TCE with the IBC is superior to that with TS.

The Benefits of an Inverted Brayton Bottoming Cycle as an Alternative to Turbo-Compounding

2015 ◽  
Author(s):  
Colin D. Copeland ◽  
Zhihang Chen
Keyword(s):  
Internal Combustion Engine ◽  
Thermal Efficiency ◽  
Heat Recovery ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Critical Parameters ◽  
Specific Power ◽  
Brayton Cycle ◽  
Exhaust Gas ◽  
Otto Cycle

The exhaust gas from an internal combustion engine contains approximately 30% of the thermal energy of combustion. Waste heat recovery systems aim to reclaim a proportion of this energy in a bottoming thermodynamic cycle to raise the overall system thermal efficiency. The inverted Brayton cycle considered as a potential exhaust-gas heat-recovery system is a little-studied approach, especially when applied to small automotive power-plants. Hence, a model of an air-standard, irreversible Otto-cycle and the inverted Brayton cycle using finite-time thermodynamics (FTT) is presented to study heat recovery applied to an automotive internal combustion engine. The other two alternatives power cycles, the pressurized Brayton cycle and the turbo-compounding system, are compared with the inverted Brayton cycle (IBC) to specify the strengths and weaknesses of three alternative cycles. In the current paper, an irreversible Otto-cycle model with an array of losses is used as a base for the bottoming cycle. The deviation of the turbomachinery from the idealized behavior is described by the isentropic component efficiencies. The performance of the system as defined as the specific power output and thermal efficiency is considered using parametric studies. The results show that the performance of the inverted Brayton cycle can be positively affected by five critical parameters — the number of compression stages, the cycle inlet temperature and pressure, the isentropic efficiency of the turbomachinery and the effectiveness of the heat exchanger. There exists an optimum pressure ratio across the IBC turbine that delivers the maximum specific power. In the view of the specific power, installing a single-stage of the inverted Brayton cycle appears to be the best balance between performance and complexity. Three alternative cycles are compared in terms of the thermal efficiency. The results indicate that the pressurized and inverted Brayton cycles can improve the performance of the turbocharged engine only when the turbomachinery efficiencies are higher than a value which changes with the operating condition. High performance of the IBC turbomachinery is required to ensure that the turbocharged engine with the inverted Brayton cycle is superior to that with turbo-compounding system.

Review of Exhaust Gas Heat Recovery Mechanism for Internal Combustion Engine Using Thermoelectric Principle

2018 ◽  
Author(s):  
Souvik Singh Rathore ◽  
Anand Singh ◽  
Prashant Kumar ◽  
Nazish Alam ◽  
Mithilesh Kumar Sahu ◽  
...  
Keyword(s):  
Internal Combustion Engine ◽  
Heat Recovery ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Exhaust Gas ◽  
Recovery Mechanism

Modeling and Simulation of an Inverted Brayton Cycle as an Exhaust-Gas Heat-Recovery System

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Zhihang Chen ◽  
Colin Copeland ◽  
Bob Ceen ◽  
Simon Jones ◽  
Alan Agurto Goya
Keyword(s):  
Heat Exchanger ◽  
Internal Combustion Engine ◽  
Thermodynamic Model ◽  
Heat Recovery ◽  
Test Bench ◽  
Combustion Engine ◽  
Brayton Cycle ◽  
Exhaust Gas ◽  
Recovery System ◽  
Heat Recovery System

The exhaust gas from an internal combustion engine contains approximately 30% of the thermal energy of combustion. The exhaust-gas heat-recovery systems aim to reclaim a proportion of this energy in a bottoming thermodynamic cycle to raise the overall system thermal efficiency. The inverted Brayton cycle (IBC) considered as a potential exhaust-gas heat-recovery system is a little-studied approach, especially when applied to small automotive power-plants. Hence, a model of the inverted Brayton cycle using finite-time thermodynamics (FTT) is presented to study heat recovery applied to a highly downsizing automotive internal combustion engine. IBC system consists of a turbine, a heat exchanger (HE), and compressors in sequence. The use of IBC turbine is to fully expand the exhaust gas available from the upper cycle. The remaining heat in the exhaust after expansion is rejected by the downstream heat exchanger. Then, the cooled exhaust gases are compressed back up to the ambient pressure by one or more compressors. In this paper, the exhaust conditions available from the engine test bench data were introduced as the inlet conditions of the IBC thermodynamic model to quantify the power recovered by IBC, thereby revealing the benefits of IBC to this particular engine. It should be noted that the test bench data of the baseline engine were collected by the worldwide harmonized light vehicles test procedures (WLTP). WLTP define a global harmonized standard for determining the levels of pollutants and CO2 emissions, fuel consumption. The IBC thermodynamic model was simulated with the following variables: IBC inlet pressure, turbine pressure ratio, heat exchanger effectiveness, turbomachinery efficiencies, and the IBC compression stage. The aim of this paper is to analysis the performance of IBC system when it is applied to a light-duty automotive engine operating in a real-world driving cycle.

Modelling and Simulation of an Inverted Brayton Cycle as an Exhaust-Gas Heat-Recovery System

2016 ◽  
Author(s):  
Z. Chen ◽  
C. D. Copeland ◽  
B. Ceen ◽  
S. Jones ◽  
A. A. Goya
Keyword(s):  
Heat Exchanger ◽  
Internal Combustion Engine ◽  
Thermodynamic Model ◽  
Heat Recovery ◽  
Test Bench ◽  
Combustion Engine ◽  
Brayton Cycle ◽  
Exhaust Gas ◽  
Recovery System ◽  
Heat Recovery System

The exhaust gas from an internal combustion engine contains approximately 30% of the thermal energy of combustion. The exhaust-gas heat-recovery systems aim to reclaim a proportion of this energy in a bottoming thermodynamic cycle to raise the overall system thermal efficiency. The inverted Brayton cycle considered as a potential exhaust-gas heat-recovery system is a little-studied approach, especially when applied to small automotive power-plants. Hence, a model of the inverted Brayton cycle using finite-time thermodynamics (FTT) is presented to study heat recovery applied to a highly downsizing automotive internal combustion engine. IBC system consists of a turbine, a heat exchanger and compressors in sequence. The use of IBC turbine is to fully expand the exhaust gas available from the upper cycle. The remaining heat in the exhaust after expansion is rejected by the downstream heat exchanger. Then, the cooled exhaust gases are compressed back up to the ambient pressure by one or more compressors. In this paper, the exhaust conditions available from the engine test bench data were introduced as the inlet conditions of the IBC thermodynamic model to quantify the power recovered by IBC, thereby revealing the benefits of IBC to this particular engine. It should be noted that the test bench data of the baseline engine were collected by the worldwide harmonized light vehicles test procedures (WLTP). WLTP define a global harmonized standard for determining the levels of pollutants and CO2 emissions, fuel consumption. The IBC thermodynamic model was simulated with the following variables: IBC inlet pressure, turbine pressure ratio, heat exchanger effectiveness, turbomachinery efficiencies, and the IBC compression stage. The aim of this paper is to analysis the performance of IBC system when it is applied to a light-duty automotive engine operating in a real world driving cycle.

scholarly journals Exhaust gas heat recovery through secondary expansion cylinder and water injection in an internal combustion engine

2017 ◽  
Vol 21 (1 Part B) ◽  
pp. 729-743
Author(s):  
Toosi Nassiri ◽  
Amir Kakaee ◽  
Hazhir Ebne-Abbasi
Keyword(s):  
Internal Combustion Engine ◽  
Thermal Efficiency ◽  
Combustion Engine ◽  
Water Injection ◽  
Internal Combustion ◽  
Exhaust Gas ◽  
Exhaust Gases ◽  
Injection Process ◽  
Direct Water Injection ◽  
Novel Concept

To enhance thermal efficiency and increase performance of an internal combustion engine, a novel concept of coupling a conventional engine with a secondary 4-stroke cylinder and direct water injection process is proposed. The burned gases after working in a traditional 4-stroke combustion cylinder are transferred to a secondary cylinder and expanded even more. After re-compression of the exhaust gases, pre-heated water is injected at top dead center. The evaporation of injected water not only recovers heat from exhaust gases, but also increases the mass of working gas inside the cylinder, therefore improves the overall thermal efficiency. A 0-D/1-D model is used to numerically simulate the idea. The simulations outputs showed that the bottoming cycle will be more efficient at higher engines speeds, specifically in a supercharged/turbocharged engine, which have higher exhaust gas pressure that can reproduce more positive work. In the modeled supercharged engine, results showed that brake thermal efficiency can be improved by about 17%, and brake power by about 17.4%.

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