REGENERATOR EFFECTIVENESS DURING TRANSIENT OPERATION

Current designs of regenerative gas turbines include high-effectivenes s rotary regenerators. The regenerators make the gas turbines highly e fficient during steady-state operation. During engine transients, howe ver, engine efficiency can be low because high-effectivenss regenerato rs tend to have large cores with largr thermal masses, and it can take a long time (minutes for example) for these regenerators to reach the ir steady-state effectivenesses. The following criterion determines th e response time of regenerators: tau(ss)similar to(mc)(R)/C-X, where t au(ss) (s) is the time period of transient operation; (mc)(R) (J/K) is the heat capacity of the core; and C-x (W/K) is the heat-capacity rat e of the exhaust. This criterion has been verified through analysis an d experimentation. The criterion enables the designer to estimate the fraction of an operating cycle during which the regenerator will have reduced effectiveness.