# Toward the Utilization of 3D Blading in the Cantilevered Stator from Highly Loaded Compressors
## 2 Research Object and Investigation Methodology
### Experimental Method  
To check the effect of the 3D blading technique, a cantilevered stator in the existing test facility was redesigned and measured experimentally to reveal the variations of the flow field. The experiment was conducted in the low-speed large-scale axial compressor (LSLSAC) test facility at Beihang University. As shown in Figure 3a, the LLSAC, whose hub-to-tip ratio is 0.75, adopts the 1.5 stage configuration, with a row of inlet guide vanes. The rotor and stator blades are nearly radially stacked by the controlled diffusion airfoil (CDA). The rotating speed is 1100 rpm, which is the same as the numerical simulation. At the design point, the stage loading coefficient is approximately 0.46 (based on midspan velocity), whereas the nominal rotor tip clearance and stator hub clearance are 1.5% and 1.0% blade height, respectively.  
As shown in Figure 3b, five measurement planes are arranged along the axial direction, where multiple static pressure taps are installed on the casing wall. The mass flow coefficient is monitored by the four circumferential static pressure taps at Plane 0, while the static pressure rise of the compressor is measured by circumferential static pressure taps at Plane 1 and Plane 5. The outlet total pressure is measured by the pitot probes at Plane 5. It should be mentioned that the inlet total pressure is the ambient pressure, which is measured by an atmospheric pressure gauge. Moreover, a torque meter is used to measure the input shaft power to the compressor, which is utilized to calculate the efficiency of the compressor. The torque efficiency is calculated as follows:  
\[\eta=\frac{30}{\pi}\frac{kR}{k-1}\frac{m_{0}T_{0}^{*}\left[(p_{5}^{*}/p_{2}^{* })^{(k-1)/k}-1\right]}{Mn}, \tag{1}\]  
where \(M\) denotes the torque, \(n\) is the rotating speed, and \(m_{0}\) and \(T_{0}^{*}\) are the mass flow rate and the total temperature at the compressor inlet (Plane 0), respectively.  
To obtain the 3D velocity and pressure profiles at the stator inlet and outlet, measurement at Planes 3 and 4 was executed using an L-shaped five-hole probe. In the radial direction, the nearest measurement point to the hub and the shroud wall was 2.0% and 2.5% blade height, respectively. Moreover, a novel zonal method was utilized to process the pressure data, through which the measurement angle range was extended to \(\pm 60^{\circ}\)[36]. The pressure was acquired by the Rosemount pressure transducers, whose measurement range and uncertainty were \(\pm 6.22\) KPa and 0.025% FS, respectively. Error analysis demonstrated  
Figure 3: Schematics of the LLSAC. (**a**) Geometry configuration; (**b**) measurement locations.  
that the measurement uncertainties of the five-hole probe were 0.5\({}^{\circ}\) for the flow angles, 1% (normalized by the flow dynamic pressure) for the total pressure, 2% (normalized by the flow dynamic pressure) for the static pressure, and 1% for the flow velocity [36].  
In the present study, oil-flow visualization tests were conducted to exhibit the flow patterns in the stator blade passage. The material used to make the skin-friction lines was a mixture of industrial silicone. The running time of each test was between 5 and 10 min.