Balance line leakage rate.
Balance line leakage rate.
(OP)
What is balance line leakage rate and how it is related to compressor performance ?
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
Balance line leakage rate.
|
RE: Balance line leakage rate.
Balance line typically goes from a high pressure tapping to the low pressure end of the compressor to help "balance" out the thrust forces.
As it involves moving parts and seals there is some leakage. This is in essence simply a flow from high to low pressure around the compressor and hence if it becomes significant then the compressor is doing the same work, but the overall flow is reduced as some is going back to the low pressure end instead of flowing out of the compressor.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Balance line leakage rate.
Johnny Pellin
RE: Balance line leakage rate.
Physically the internal leakage is through the inter/stage balance piston for back to back. The external leakage for inline and back to back types, is flowing via a pipe physically coming out of the machine from discharge side and going in again on suction side (that is to say it is `end to end`).
The leakage rate depends on several construction and performance factors, some that can be mentioned are
- Operation on the performance map, which typically relates to speed, flow and compression ratio
- Type of seals being used on the balance drum or piston (teeth, stepped, honeycomb, etc.) as well as the geometry (number of teeth, geometry etc.). Increasing the number of teeth will lead to a longer span, well very slightly but noticeable in some cases.
As already pointed out, the `price to pay` for balancing the thrust forces across a machine is performance-efficiency penalty (like LittleInch indicated, leakage accounts as internal recirculation and thus impacts the overall compression work). It also induces increased destabilizing effects in terms of lateral stability (so called cross coupling stiffness) but that is beyond the original question scope.
Not to mention that recirculation on high pressure machine is often causing a non negligible increase of temperature at the suction considering hot gas from discharge side is being mixed with the incoming main suction stream. For instance on some production - upstream applications, the leakages can amount for up to 10 percent of the nominal flow of the machine, and that is by design, one has to be careful.
Hope it helps!