Enter Name and Date

MEASUREMENT OF LOSSES THROUGH A TURBINE

• SCOPE OF RESEARCHThe recent rise of fuel costs has directed the design focus ofgas turbine engines to improvements in efficiency while alsominimizing the weight and manufacturing costs. Idealized testconditions are created in the low-speed wind tunnel facility in

G. D. MACISAAC, S. A. SJOLANDER

• MEAUREMENT PROBESA comparison of the measured total pressure is performedusing two accepted measurement instruments. The seven-hole and Kiel pressure probes are depicted in Figure 2.

� Seven-hole pressure probe

• FLOW FIELD ANALYSISTotal pressure losses are commonly presented as contour plots as shown in Figure 3. The highest loss fluid is indicated by red regions while the blue areas indicate no loss fluid.

� A discrepancy between the probes

z/h

0.3

0.4

0.5 CPo

0.00-0.05-0.10-0.15

-0.20-0.25-0.30-0.35-0.40-0.45

-0.50-0.55-0.60-0.65-0.70-0.75

Seven-hole

Higher losses

conditions are created in the low-speed wind tunnel facility in

which a linear cascade of straight blades is used to simulatethe infinite repetition of blades in an actual engine. Of specificinterest is the measurement of the total pressure loss througha turbine bladerow as this relates directly to its efficiency. Thefocus of the current research is the accuracy of the total

pressure measurements within the complex flow field that exitsa turbine bladerow.

• MEASUREMENT LOCATIONSFigure 1 depicts two blades of a linear turbine cascade in

� Seven-hole pressure probe− Measures total pressure, static pressure and all three

velocity components

− Calibration is required to relate the seven port pressures to a total pressure and two flow angles

� Kiel probe− Measures total pressure and is insensitive to flow

misalignment

− Outer sheath directs misaligned flow to inner Pitot tube

� A discrepancy between the probesThe seven-hole probe measures higher losses in the location

noted in Figure 3. The cause of this discrepancy is not fully understood and is currently being investigated.

0.4

0.5 CPo

0.00-0.05-0.10-0.15

-0.20-0.25-0.30-0.35-0.40-0.45

y/s

z

0.0 0.2 0.4 0.6 0.8 1.0

0.0

0.1

0.2

-0.75

-0.80-0.85-0.90-0.95

Kiel

Lower losses

Figure 1 depicts two blades of a linear turbine cascade inwhich both inner passage and downstream experimentalresults are shown. Measurements are made by traversing atwo-dimensional plane in the pitchwise and spanwise

directions.

CPo

0.00-0.05

Spanw

5

6

43

7

12

1.83 OD1.37 ID

.46 OD (7 tubes)

.25 ID

30°

1.60 OD1 45 ID

Seven-hole

Inner Pitot tubeOuter Sheath

y/s

z/h

0.0 0.2 0.4 0.6 0.8 1.0

0.0

0.1

0.2

0.3

-0.45

-0.50-0.55-0.60-0.65-0.70-0.75

-0.80-0.85-0.90-0.95

Lower losses

Figure 2: Nose geometry for the seven-hole and Kiel probe (mm) Figure 3: Total pressure contours for the seven-hole and Kiel probeFigure 1: Cascade nomenclature and measurement planes

-0.10

-0.15-0.20-0.25-0.30-0.35

-0.40-0.45-0.50-0.55-0.60

-0.65-0.70-0.75-0.80

-0.85-0.90-0.95

wis

e (z

/h)

1.45 ID

.46 OD

.38 ID 2X Ø .64 vent holes

Kiel