I have recently some research about Siemens turbine, specially SGT400 model. this type of turbine can be used as a generator and also as a compressor. Both of them has a core "core engine " http://www.energy.siemens.com/hq/en/power-generation/gas-turbines/sgt-400.htm I need to know is it possible to use core engine which designed for generator in compressor mode practically. In fact, my question focused on this subject " is it risky? or what kind of problem may be happens if we use these core engine instead of each other, is it any difference in their designs and so on. " I read all Siemens documents about SGT400. but i have no drawings and i m not expert in this filed :( Its highly appreciated if you help me in this regards.