Browse Prior Art Database

Boundary Layer Control on Shroud Surface

IP.com Disclosure Number: IPCOM000128747D
Published in the IP.com Journal: Volume 5 Issue 10A (2005-10-25)
Included in the Prior Art Database: 2005-Oct-25
Document File: 2 page(s) / 281K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

The performance of centrifugal compressors is dominated by the aerodynamic performance of the impeller and the diffuser immediately downstream of it. The performance depends on compressor surge, compressor speed at a given pressure ratio and compressor efficiency. Usual requirements are occurrence of surge at a flow rate which should be as low as possible and high performance. At present, the compressor discharge flow at surge is reduced by recirculating flow around the impeller leading edge. This method reduces the compressor efficiency. Surge can also be delayed by use of a device which imparts swirl to the flow upstream of the impeller in the same sense as the impeller rotation. This device is costly since it usually imparts movable inlet guide vanes. These vanes also cause aerodynamic loss. For unshrouded impellers flow that has passed through the impeller tip clearance has high entropy and causes regions of high incidence on diffuser vanes. The suggested solution is concerned with the effective removal of a small portion of the impeller exit flow before the remainder of the flow enters the diffuser. Typically this proportion would be two percent of the total flow through the impeller. This proportion is taken from the area of the impeller shroud casing just downstream of the impeller. The flow which is bled off is predominantly flow that has passed over the impeller tip and is of high entropy and high swirl. This flow is reintroduced to the compressor upstream of the impeller in a manner that does not disturb the main inflow.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

S

Boundary Layer Control on Shroud Surface

Idea: Dr. Paul Eifion Roach, GB-Lincoln; Francis Joseph Geoffrey Heyes, GB-Lincoln

The performance of centrifugal compressors is dominated by the aerodynamic performance of the impeller and the diffuser immediately downstream of it. The performance depends on compressor surge, compressor speed at a given pressure ratio and compressor efficiency. Usual requirements are occurrence of surge at a flow rate which should be as low as possible and high performance.

At present, the compressor discharge flow at surge is reduced by recirculating flow around the impeller leading edge. This method reduces the compressor efficiency. Surge can also be delayed by use of a device which imparts swirl to the flow upstream of the impeller in the same sense as the impeller rotation. This device is costly since it usually imparts movable inlet guide vanes. These vanes also cause aerodynamic loss. For unshrouded impellers flow that has passed through the impeller tip clearance has high entropy and causes regions of high incidence on diffuser vanes.

The suggested solution is concerned with the effective removal of a small portion of the impeller exit flow before the remainder of the flow enters the diffuser. Typically this proportion would be two percent of the total flow through the impeller. This proportion is taken from the area of the impeller shroud casing just downstream of the impeller. The flow which is bled off is predominantly flow that has passed over the impell...