Re: EPR v. N1 for turbofan power setting

From: (R. & L. Chilukuri)
Organization: Univ of California at San Diego
Date:         14 Mar 95 02:34:35 
References:   1 2 3 4
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In article <airliners.1995.251@ohare.Chicago.COM>, 

>: Lakshmi N. Chilukuri ( wrote:
>: : EPR is the ratio of the primary (hot) stream total pressure to the 
>: : total pressure of the freestream. EPR should be greater than 1.0 if 
>: : the engine is running. says...
> The textbook I was reading last night defines Engine Pressure Ratio as
>the the ratio of the pressures recorded at the inlet and in the hot
>exhaust. I dont see how this can be less than one.

I just received flight test data for a RR engine that clearly shows EPR 
to be greater than 1.0 for all power settings, altitudes and freestream 
Mach numbers. 

Perhaps some engineers prefer to subtract 1.0 from the above definition 
of EPR.