AC 6-10 Test Data

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Axial compressor cascade

Application Challenge 6-10 © copyright ERCOFTAC 2004

Test Data

Overview of Measurements

Experimental investigations on the boundary layer and loss behaviour on a high turning compressor cascade up to 0.90 inlet Mach number were performed in the High Speed Cascade Wind Tunnel of DFVLR Braunschweig. The tunnel was installed in a tank which could be evacuated from 1 to 0.05 bar and an independent variation of Mach number and Reynolds number was possible. The degree of turbulence at inlet was about 5% using grids of crossed bars upstream of the cascade. The tunnel geometry is described in section 1.4. The design point of the V2 cascade is given by an inlet Mach number of 0.85, Reynolds number of 5E5 (based on blade chord), inlet flow angle of 139.5° and flow turning of 50°.

Wake traverse measurements (total pressure, static pressure and outlet flow angle) at mid-span position of blade number 8 were performed with a wedge type probe located at 30% of true chord axially downstream of the blade trailing edge. Figure 2.1 shows a diagram of the wedge probe used and Figure 2.2 shows the location of the measuring plane. Surface pressure distributions also at the midspan position were measured using static pressure tappings on the suction and the pressure sides of the blades adjacent to the center blade.

Figure 2.1 Wedge probe

Figure 2.2 V2 Cascade geometry and locations of measurement planes

x/l	YPS/l	x/l	YSS/l
0	0.0049	0	0.0049
0.0003	0.0033	0.0014	0.0082
0.0012	0.0017	0.0020	0.0087
0.0020	0.0009	0.0054	0.0112
0.0040	0.0001	0.0120	0.0156
0.0066	0.0003	0.0254	0.0244
0.0103	0.0018	0.0355	0.0309
0.0196	0.0034	0.0665	0.0493
0.0242	0.0071	0.1017	0.0683
0.0335	0.0106	0.1341	0.0840
0.0662	0.0222	0.1672	0.0983
0.0992	0.0329	0.2007	0.1113
0.1325	0.0428	0.2348	0.1229
0.1660	0.0519	0.2655	0.1320
0.1997	0.0601	0.3004	0.1409
0.2336	0.0674	0.3317	0.1576
0.2677	0.0738	0.3672	0.1538
0.3020	0.0793	0.3989	0.1581
0.3314	0.0834	0.4348	0.1615
0.3659	0.0873	0.4667	0.1633
0.4005	0.0903	0.4988	0.1639
0.4351	0.0924
0.4698	0.0936
0.4995	0.0940

Symmetrical for x/l = 0 – 0.5 and 0.5 – 1.0 respectively. Leading radius r_N/l = 0.0049 Trailing edge radius r_H/l = 0.0049 Table 2.1 Profile coordinates for the ECA2-V2 cascade.

Boundary layer measurements were carried out at different positions on the blade suction side at the midspan position. Figure 2.2 shows the locations of the inlet and exit measuring planes and the locations of the boundary layer measurements. These boundary layer measurements were carried out with a specially developed two finger probe (see Figure 2.3). The probe was calibrated for Mach and Reynolds number, flow angle and turbulence level. Corrections were applied from these calibrations on the basis of a comparison with flat plate experiments and with measurements by a Laser-Doppler anemometer. There is a high level of confidence in the experimental data and the case was chosen by AGARD Working Group 18.

Figure 2.3 Two finger boundary layer probe

Overview of tests

All the tests were carried out at an inlet Reynolds number of 5E5 based on blade chord and with a freestream turbulence intensity of 5%. The results are presented in two groups. EXP1-4 investigated a range of inlet mach numbers from 0.3 to 0.85 for the design inlet angle of 49.5 degrees and a constant Ω of 1.20. EXP7-EXP10 then demonstrated the influence of inlet angle at constant Mach number (M₁=0.8) on different Ω values. These tests are summarized in Table Exp-A.

In all tests the measured parameters were:

• Total pressure, static pressure and outlet flow angle at the mid-span position of blade number 8 at 30% of true chord axially downstream of the blade trailing edge.

• Surface pressure distributions also at the midspan position on the suction and the pressure sides of the blades adjacent to the center blade.

• Boundary layer measurements (total and static pressure through the boundary layer) were carried out at different positions (see Figure 2.2) on the blade suction side at the midspan position.

The data corresponding to these measurements is summarized in Table Exp-B.

Boundary Data

At the inlet boundary (station 1) the flow can be assumed steady, uniform pitchwise and turbulent. The turbulent intensity was calculated using a single hotwire probe placed normal to the freestream velocity from which a fluctuating velocity was obtained.

Pressure and temperature data is measured at the inlet and outlet.

The outflow measurement plane is located far enough downstream of the blade trailing edge to have no effect on the flow over the blade. The blade surfaces and the wall boundaries are considered to be smooth. The pitchwise boundaries for the measurement blade can be considered to be periodic.

Measurement Errors

The errors in measurement quantities for all tests are:

α = ±0.2degrees

M = ±0.003

ζ₁ = ±0.001

Cp = ±0.005

The boundary layer probe was calibrated for Mach and Reynolds number, flow angle and turbulence level. Corrections were applied from these calibrations on the basis of a comparison with flat plate experiments and with measurements by a Laser-Doppler anemometer.

Table EXP-A Summary Description of all Test Cases

	GNDPs		PDPs			MPs
	Re	Tu1 %	M1	α1 (deg)	Ω	Detailed Data	DOAPs
	EXP 1	5x105	5	0.3	49.5			1.2	Cp, ω, w/w∞	ζ1, a2, M2
	EXP 2	5x105	5	0.6	49.5			1.2

Table EXP-A Summary description of all test cases

	GNDPs	PDPs (problem definition parameters)				MPs (measured parameters)
	Re1	Tu1 %	M1	α1 (degs)	Ω	detailed data	DOAPs
EXP 1	5E5	5	0.3	49.5	1.2	Cp, ω, w/w∞	ζ1, a2, M2
	Re1	Tu1 %	M1	α1 (degs)	Ω	detailed data	DOAPs
EXP 2	5E5	5	0.6	49.5	1.2	Cp, ω, w/w∞	ζ1, a2, M2
	Re1	Tu1 %	M1	α1 (degs)	Ω	detailed data	DOAPs
EXP 3	5E5	5	0.8	49.5	1.2	Cp, ω, w/w∞	ζ1, a2, M2
	Re1	Tu1 %	M1	α1 (degs)	Ω	detailed data	DOAPs
EXP 4	5E5	5	0.85	49.5	1.2	Cp, ω, w/w∞	ζ1, a2, M2
	Re1	Tu1 %	M1	α1 (degs)	Ω	detailed data	DOAPs
EXP 7	5E5	5	0.8	49.5	1.12	Cp, ω, w/w∞	ζ1, a2, M2
	Re1	Tu1 %	M1	α1 (degs)	Ω	detailed data	DOAPs
EXP 8	5E5	5	0.8	49.5	1.27	Cp, ω, w/w∞	ζ1, a2, M2
	Re1	Tu1 %	M1	α1 (degs)	Ω	detailed data	DOAPs
EXP 9	5E5	5	0.8	52.5	1.12	Cp, ω, w/w∞	ζ1, a2, M2
	Re1	Tu1 %	M1	α1 (degs)	Ω	detailed data	DOAPs
EXP 10	5E5	5	0.8	52.5	1.3	Cp, ω, w/w∞	ζ1, a2, M2

Table EXP-B Summary description of all measured parameters and available datafiles

	MP 1 Cp (pressure coefficient)	MP 2 ω (pressure loss coefficient)	MP 3 w/w∞ (velocity ratio)	DOAPs ζ1 (%), M2,α2 (deg)
EXP 1	exp11.dat	exp12.dat	exp13.dat	exp14.dat
EXP 2	exp21.dat	exp22.dat	exp23.dat	exp24.dat
EXP 3	exp31.dat	exp32.dat	exp33.dat	exp34.dat
EXP 4	exp41.dat	exp42.dat	exp43.dat	exp44.dat
EXP 7	exp71.dat	exp72.dat	Exp73.dat	exp74.dat
EXP 8	exp81.dat	exp82.dat	Exp83.dat	exp84.dat
EXP 9	exp71.dat	exp72.dat	Exp93.dat	exp74.dat
EXP 10	exp81.dat	exp82.dat	Exp103.dat	exp84.dat

Test Case EXP-1

EXP1 Measurements on the V2 high subsonic linear compressor cascade: The test was carried out with an inlet mach number of 0.3 for the design inlet angle of 49.5 degrees and a constant Ω of 1.20. Reynolds number at inlet was 5E5 based on blade chord and turbulence intensity was 5%. Data was recorded for total and static pressure and flow direction at stations 1 and 2 corresponding to inlet and exit planes respectively. Pressure distribution through the boundary layer was recorded at several locations on the blade suction surface.

exp11.dat (ASCII file; headers: Re, Tu; M₁, α₁, Ω. columns: x/l, Cp)

exp12.dat (ASCII file; headers: Re, Tu; M₁, α₁, Ω. columns: y/t, ω)

exp13.dat (ASCII file; headers: Re, Tu; M₁, α₁, Ω, x/l. columns: h, w/w_∞)

exp14.dat (ASCII file; headers: Re, Tu; M₁, α₁, Ω. Data: M₂, α₂, ζ₁)

Test Case EXP-2

See EXP 1: M₁₌0.6, α₁=49.5, Ω=1.2

Test Case EXP-3

See EXP 1: M₁₌0.8, α₁=49.5, Ω=1.2

Test Case EXP-4

See EXP 1: M₁₌0.85, α₁=49.5, Ω=1.2

Test Case EXP-7

See EXP 1: M₁₌0.8, α₁=49.5, Ω=1.12

Test Case EXP-8

See EXP 1: M₁₌0.8, α₁=49.5, Ω=1.27

Test Case EXP-9

See EXP 1: M₁₌0.8, α₁=52.5, Ω=1.12

Test Case EXP-10

See EXP 1: M₁₌0.8, α₁=52.5, Ω=1.3

References

2.1 'Test cases for computation of internal flows in aero engine components', L. Fottner, Propulsion and Energetics Panel Working Group 18, AGARD Advisory report No. 275, 1990.

© copyright ERCOFTAC 2004

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Contributors: Michael Dickens; Alex Read - Computational Dynamics Ltd

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