CEAS Aeronautical Journal

, Volume 6, Issue 1, pp 39–47

# Numerical investigation of the influence of the camber distribution at the rotor tip on the efficiency at different tip clearances

• Henner Schrapp
• Denes Fischer
• Jens Ortmanns
• Markus Goller
• Bronwyn Power
Original Paper

## Abstract

The present paper reports on numerical investigations into the relationship of compressor efficiency drop due to increased rotor tip clearance and the rotor tip camber distribution in a 1.5 stage low-speed axial flow compressor. Starting from a baseline compressor, six alternative designs were derived. In these redesigns the tip section camber line of the rotor was replaced by an analytically given camber distribution. These camber lines used for the redesigns ranged from extreme front load to extreme rear load. The new camber line styles were blended into the original blade over the upper 30 % of blade height. For each of these variations a design speed characteristic was calculated for five different rotor tip clearances. From these characteristics the compressor efficiency at the design flow rate was extracted. Based on these values an exchange rate could be calculated relating compressor overall efficiency to rotor tip clearance height. It turned out that the rotor tip camber line style does not have an impact on this exchange rate. It could be shown that rotor losses are only affected slightly by the rotor tip camber line style and that the pressure rise that the tip vortex experiences as it travels through the passage is generally unchanged from one tip camber line style to the other.

## Keywords

Tip clearance losses Camber line Clearance flow

## List of symbols

$$c[\mathrm {m}]$$

Chord length

$$c_{\mathrm {ax}}$$$$[\mathrm {m}]$$

Axial chord length

$$c_{p}$$$$[1]$$

Pressure coefficient

$$D$$$$[\mathrm {m}]$$

Diameter

$$\eta$$$$[1]$$

$$h$$$$[1]$$

Annulus height

$$\Delta \!{h}$$ [m2/s2]

Specific work input

$$\kappa$$$$[^{\circ }]$$

$$\nu$$$$[1]$$

Hub–to–tip ratio

$$p$$$$[\mathrm {Pa}]$$

Static pressure

$$p_t$$$$[\mathrm {Pa}]$$

Stagnation pressure

$$r$$$$[\mathrm {m}]$$

$$\mathrm {Re}'$$$$[1]$$

Reynolds number based on relative inlet velocity and blade chord

$$s$$$$[\mathrm {m}]$$

$$\tau$$$$[\mathrm {m}]$$

Tip clearance height

$$t$$$$[\mathrm {m}]$$

$$T_t$$$$[\mathrm {K}]$$

Stagnation temperature

$$U$$ [m/s]

$$v_{\mathrm {ax}}$$[m/s]

Axial velocity

$$x$$$$[\mathrm {m}]$$

Axial coordinate

$$\psi$$$$[1]$$

Work coefficient $$(\Delta \!{h}/{U^ 2})$$

$$\varphi$$$$[1]$$

Flow coefficient $$(\dot {m}/{\rho\,AU })$$

$$\theta$$$$[1]$$

Angular coordinate

$$\zeta _{V1}$$$$[1]$$

Loss coefficient

## Notes

### Acknowledgments

The authors would like to thank Rolls–Royce Deutschland Ltd & Co KG for encouraging and approving the publication of this work.  The investigations were conducted as part of the joint research project AeroBlisk in the frame of the LuFo IV program and as part of the European Union funded framework 7 project LEMCOTEC. This work was funded by Rolls–Royce Deutschland, the Bundesministerium für Wirtschaft und Technologie (BMWi) as per resolution of the German Federal Parliament under the Grant No. 20T0901A and the European Union under Grant Agreement No. 283216.

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© Deutsches Zentrum für Luft- und Raumfahrt e.V. 2014

## Authors and Affiliations

• Henner Schrapp
• 1
• Denes Fischer
• 1
• Jens Ortmanns
• 1
• Markus Goller
• 1
• Bronwyn Power
• 2
1. 1.Rolls–Royce Deutschland Ltd & Co KGBlankenfelde-MahlowGermany
2. 2.Rolls–Royce CorporationIndianapolisUSA