Inverted Brayton Cycle With Exhaust Gas Condensation

Ian Kennedy, Zhihang Chen, Simon Jones, Bob Ceen, Colin Copeland

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

Approximately 30% of the energy from an internal combustion engine is rejected as heat in the exhaust gases. An inverted Brayton cycle (IBC) is one potential means of recovering some of this energy, in order to improve the overall system efficiency. When a fuel is burnt, water and CO2 are produced and expelled as part of the exhaust gases. In an IBC, in order to reduce compression work, the exhaust gases are cooled before compression up to ambient pressure. If coolant with a low enough temperature is available, it is possible to condense some of the water out of the exhaust gases, further reducing compressor work.
In this study the condensation of exhaust gas water is studied. The results show that the IBC can produce about 50 kW/kg/s for the conditions investigated. The main factors that influence the power output are heat exchanger pressure drop, turbine expansion ratio and coolant temperature. A lower coolant temperature significantly increases power output, particularly when condensation occurs. Larger turbine expansion ratios produce more power and slightly lower the temperature at which condensation onset occurs. The system is very sensitive to heat exchanger pressure drop, as larger pressure drops increase the compressor pressure ratio whilst leaving the turbine expansion ratio unchanged. Higher turbine inlet pressures can also increase net power, but the higher exhaust backpressures pressures may increase engine pumping losses.
Finally, for conditions when condensation is possible, the water content of the exhaust gas has a significant influence on power output. The hydrogen to carbon ratio of the fuel has the most potential to vary the water content and hence the power generated by the system. If there is no condensation, water content has a small impact on performance. The effect on power in the condensing region is predominantly due to reduced mass flow in the compressor.
LanguageEnglish
Title of host publicationASME Turbo Expo 2017 Conference Proceedings
Place of PublicationCharlotte, U. S. A.
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Print)9780791850954
DOIs
StatusPublished - 2017

Fingerprint

Brayton cycle
Exhaust gases
Condensation
Turbines
Coolants
Water content
Pressure drop
Compressors
Heat exchangers
Plant expansion
Water
Intake systems
Temperature
Internal combustion engines
Compaction
Engines
Hydrogen
Carbon

Cite this

Kennedy, I., Chen, Z., Jones, S., Ceen, B., & Copeland, C. (2017). Inverted Brayton Cycle With Exhaust Gas Condensation. In ASME Turbo Expo 2017 Conference Proceedings [GT2017-64695] Charlotte, U. S. A.: American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/GT2017-64695

Inverted Brayton Cycle With Exhaust Gas Condensation. / Kennedy, Ian; Chen, Zhihang; Jones, Simon; Ceen, Bob; Copeland, Colin.

ASME Turbo Expo 2017 Conference Proceedings. Charlotte, U. S. A. : American Society of Mechanical Engineers (ASME), 2017. GT2017-64695.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Kennedy, I, Chen, Z, Jones, S, Ceen, B & Copeland, C 2017, Inverted Brayton Cycle With Exhaust Gas Condensation. in ASME Turbo Expo 2017 Conference Proceedings., GT2017-64695, American Society of Mechanical Engineers (ASME), Charlotte, U. S. A. https://doi.org/10.1115/GT2017-64695
Kennedy I, Chen Z, Jones S, Ceen B, Copeland C. Inverted Brayton Cycle With Exhaust Gas Condensation. In ASME Turbo Expo 2017 Conference Proceedings. Charlotte, U. S. A.: American Society of Mechanical Engineers (ASME). 2017. GT2017-64695 https://doi.org/10.1115/GT2017-64695
Kennedy, Ian ; Chen, Zhihang ; Jones, Simon ; Ceen, Bob ; Copeland, Colin. / Inverted Brayton Cycle With Exhaust Gas Condensation. ASME Turbo Expo 2017 Conference Proceedings. Charlotte, U. S. A. : American Society of Mechanical Engineers (ASME), 2017.
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N2 - Approximately 30% of the energy from an internal combustion engine is rejected as heat in the exhaust gases. An inverted Brayton cycle (IBC) is one potential means of recovering some of this energy, in order to improve the overall system efficiency. When a fuel is burnt, water and CO2 are produced and expelled as part of the exhaust gases. In an IBC, in order to reduce compression work, the exhaust gases are cooled before compression up to ambient pressure. If coolant with a low enough temperature is available, it is possible to condense some of the water out of the exhaust gases, further reducing compressor work.In this study the condensation of exhaust gas water is studied. The results show that the IBC can produce about 50 kW/kg/s for the conditions investigated. The main factors that influence the power output are heat exchanger pressure drop, turbine expansion ratio and coolant temperature. A lower coolant temperature significantly increases power output, particularly when condensation occurs. Larger turbine expansion ratios produce more power and slightly lower the temperature at which condensation onset occurs. The system is very sensitive to heat exchanger pressure drop, as larger pressure drops increase the compressor pressure ratio whilst leaving the turbine expansion ratio unchanged. Higher turbine inlet pressures can also increase net power, but the higher exhaust backpressures pressures may increase engine pumping losses.Finally, for conditions when condensation is possible, the water content of the exhaust gas has a significant influence on power output. The hydrogen to carbon ratio of the fuel has the most potential to vary the water content and hence the power generated by the system. If there is no condensation, water content has a small impact on performance. The effect on power in the condensing region is predominantly due to reduced mass flow in the compressor.

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