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Research Papers: Gas Turbines: Cycle Innovations

The Expansion-Cycle Evaporation Turbine

[+] Author and Article Information
N. G. Barton

 Sunoba Pty Ltd, P.O. Box 1295, Macquarie Centre, NSW 2113, Australianoel.barton@sunoba.com.au

J. Eng. Gas Turbines Power 134(5), 051702 (Mar 05, 2012) (7 pages) doi:10.1115/1.4004743 History: Received July 17, 2011; Revised July 24, 2011; Published March 05, 2012; Online March 05, 2012

This paper investigates a continuous-flow heat engine based on evaporative cooling of hot air at reduced pressure. In this device, hot air is expanded in an expansion turbine, spray-cooled to saturation and re-compressed to ambient pressure in several stages with evaporative cooling between each stage. More work is available in expansion than is required during re-compression, so the device is a heat engine. The device provides a relatively cheap way to boost the power output of open-cycle gas turbines. The principal assumptions for the theoretical model developed herein are that air and water vapor are regarded as ideal gases with constant specific heat capacities. In the absence of losses associated with expansion and compression, the engine produces more power as the inlet temperature and the pressure ratio increase. The effects of irreversibilities are subsequently included in the expansion and compression stages, with realistic values used for the adiabatic efficiencies of turbine and fans. Purification and injection of water are also considered in the overall energy budget. As a typical result for the new engine, if the inlet air is the exhaust of a 56 MW open-cycle gas turbine, the adiabatic efficiencies of turbine and fan are 0.9, the pressure ratio is 6.5 and there is four-stage re-compression, then the power output is 20.5% that of the gas turbine. The power output is sensitive to the adiabatic efficiencies of turbine and fans.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

Illustrating the ECET concept. Here the ECET has 4-stage inter-cooled re-compression and is deployed downstream of an open-cycle gas turbine.

Grahic Jump Location
Figure 2

P-υ indicator diagram for the loss-free ECET thermodynamic cycle for the case with r = 6.5, T1 = 508degC, Pa1 = 92.5 kPa, Pυ1 = 8.8 kPa and 1-stage re-compression. P (y-axis, kPa) is the total pressure and υ (x-axis, m3/kg) is the specific volume. Numbers denote stations as used in Sec. 2.

Grahic Jump Location
Figure 3

Loss-free specific work output (y-axis, kJ/kg dry air) for the 10-stage ECET as a function of pressure ratio r (x-axis, dimensionless) and inlet temperature T1

Grahic Jump Location
Figure 4

Loss-free specific water consumption (y-axis, liters/kWhr) for the 10-stage ECET as a function of pressure ratio r (x-axis, dimensionless) and inlet temperature T1

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