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

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

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4031790 ◽

2015 ◽

Vol 138 (7) ◽

Cited By ~ 6

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.

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

Volume 8: Microturbines, Turbochargers and Small Turbomachines; Steam Turbines ◽

10.1115/gt2015-42623 ◽

2015 ◽

Cited By ~ 5

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.

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Design of a Method for Test Diagnostics of an Internal Combustion Engine Based on the Analysis of the Exhaust Gas Composition

Elektrotekhnologii i elektrooborudovanie v APK ◽

10.22314/2658-4859-2020-67-1-104-110 ◽

2020 ◽

Vol 67 (1) ◽

pp. 104-110

Author(s):

Aleksandr V. Gritsenko ◽

Grigoriy N. Salimonenko ◽

Maksim V. Nazarov

Keyword(s):

Internal Combustion Engine ◽

Internal Combustion Engines ◽

Combustion Engine ◽

Internal Combustion ◽

Research Purpose ◽

Exhaust Gas ◽

Combustion Engines ◽

Ignition System ◽

Exhaust Gases ◽

Diagnostic Parameters

The introduction of methods for timely diagnostics of internal combustion engines allows maintaining the environmental indicators of the car fleet at the highest level. (Research purpose) The research purpose is in increasing the reliability of diagnostics of internal combustion engines by using data obtained by selective sampling of exhaust gases. (Materials and methods) Informational, mathematical and experimental research methods, including methods for statistical processing of results and analysis of data obtained during experiments were used during the study. (Results and discussion) The main systems that affect the environmental performance of internal combustion engines has been identified: the fuel supply system, the ignition system and the exhaust gas neutralization system. The article describes a generalized mathematical model for calculating the characteristics of exhaust gases. Authors conducted operational tests on 35 internal combustion engines with justification of their number according to standard methods. The actual value of diagnostic parameters was processed into relative percentages for drawing a nomogram. A zero value has been set for the reference state of the elements specified by the manufacturer. (Conclusions) It was found that the dominant number of failures accounted for internal combustion engines, in detail: the ignition system produces 15-25 percent of failures, the power system produces 30-44 percent, the exhaust system produces 10-15 percent. It was found that for unambiguous identification of any combination of factors, it is necessary to have output values of at least three evaluation criteria. It was found that the most sensitive parameters for evaluating the technical condition of the three systems are: changes in the engine crankshaft speed, the parameters of exhaust gas toxicity, CO, CO2, CH, O2 when providing test modes (operation of the internal combustion engine on 1 cylinder at 20 and 40 percent of the throttle opening). The article describes designed a gasoline engine loader for the implementation of diagnostic modes and control of diagnostic parameters, that allows to create operating loads with an accuracy of 0.1 percent.

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