Current designs of regenerative gas turbines include high-effectiveness rotary regenerators. The regenerators make the gas turbines highly efficient during steady-state operation. During engine transients, however, engine efficiency can be low because high-effectiveness regenerators tend to have large cores with large thermal masses, and it can take a long time (minutes for example) for these regenerators to reach their steady-state effectivenesses. The following criterion determines the response time of regenerators:
$τss˜(mc)R/Cx,$
where τxx (S) is the time period of transient operation; (mc)R (J/K) is the heat capacity of the core; and Cx (W/K) is the heat-capacity rate of the exhaust. This criterion has been verified through analysis and experimentation. The criterion enables the designer to estimate the fraction of an operating cycle during which the regenerator will have reduced effectiveness.
1.
Beck, D. S., and Wilson, D. G., Gas-Turbine Regenerators, Chapman and Hall, New York, 1996.
2.
London, A. L., Sampsell, D. F., and McGowan, J. G., “The Transient Response of Gas Turbine Plant Heat Exchangers—Additional Solutions for Regenerators of the Periodic-Flow and Direct-Transfer Types,” ASME JOURNAL OF ENGINEERING FOR POWER, Vol. 86, 1964.
3.
User’s manual for RGT-OPT, available from Douglas Stephen Beck, 1996.
4.
Potter, M. C., and Foss, J. F., Fluid Mechanics, Great Lakes Press, Inc., Okemos, MI, 1982.
5.
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6.
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Kays, W. M., and London, A. L., Compact Heat Exchangers, 3rd ed., McGraw-Hill, New York, 1984.
8.
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Wilson, D. G., Design of High-Efficiency Turbomachinery and Gas Turbines, The MIT Press, Cambridge, MA, 1984.
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