Tsiolkovsky
Mechanical
- May 20, 2010
- 58
Can someone please correct me on my interpretation and explanation of polytropic efficiency, because Saravanamuttoo et al explanations are pretty atrocious. I see it as (applied to compressors, axial, that is):
NB Assumption: Every individual stage of an axial flow compressor has the same isentropic efficiency to each other
If we cascade more than one stage, the efficiency of the next stage will "act upon" the efficiency of the previous stage thus constantly decreasing overall efficiency as we cascade more.
Thus if we could take one stage to achieve the same pressure rise, the isentropic efficiency will only be multiplied once across the single stage.
In lames terms, if one stage gives 0.9 efficiency and we couple 5 stages, then the overall comp efficiency will be 0.9^ 5 = 0.59049
NB Assumption: Every individual stage of an axial flow compressor has the same isentropic efficiency to each other
If we cascade more than one stage, the efficiency of the next stage will "act upon" the efficiency of the previous stage thus constantly decreasing overall efficiency as we cascade more.
Thus if we could take one stage to achieve the same pressure rise, the isentropic efficiency will only be multiplied once across the single stage.
In lames terms, if one stage gives 0.9 efficiency and we couple 5 stages, then the overall comp efficiency will be 0.9^ 5 = 0.59049
