Quote:
Originally Posted by trebuchet03
And a reheat stage  |
Not on a simple gas turbine cycle! On a simple cycle, a reheat stage actually DECREASES efficiency. It will increase power output. But much of this energy will be lost in the form of a REALLY hot exhaust. On the other hand, efficiency can be improved by a reheat stage IF the reheat is used in conjunction with a recuperator (regenerator). A regenerator uses the heat of the exhaust to preheat the air coming out of the compressor before the combustor. So much of this heat is put back into the cycle.
Because a recuperator puts exhaust heat back into the cycle, a recuperator can sometimes also improve the efficiency of a simple cycle. But note the word 'sometimes'. Specifically, a recuperator improves efficiency most in gas turbines of low pressure ratio. But as pressure ratio increases, the compressor outlet temperature INCREASES while the exhaust temperature DECREASES. And as pressure ratio is increased, a point is eventually reached where the compressor outlet is hotter than the exhaust. When this is the case, a recuperator will obviously decrease efficiency.
With this said, a recuperator would DEFINITELY be a good idea on the kind of low pressure ratio, centrifugal gas turbine that would ever likely be used in a road vehicle. On the other hand, a recuperator increases the physical size of the turbine and increases pumping losses. So ultimately, a high pressure ratio, non-recuperated turbine is a better idea. However, such a turbine is not likely to be cost-effective.
On the other hand, I doubt gas turbines will ever make it into mainstream use on road vehicles. Fuel cells appear to have MUCH more promise in terms of efficiency, cost, and practicality.
Eventually it'll be pounded in 
Linear Mode
