D.2 Basic Aerodynamic Research Tunnel
5.2 Benchmark Test Cases
The selected test cases for this study include an ultra-high- bypass-ratio fan stage, the NASA-Pratt & Whitney Advanced Ducted Propulsor (ADP) Fan 1; a high-bypass-ratio fan stage,
the NASA-General Electric Source Diagnostic Test (SDT) fan; and a moderate-bypass-ratio fan stage, the NASA- Honeywell Quiet High Speed Fan 2 (QHSF 2). Again, the benchmark cases selected are not meant to be exhaustive, but representative. All three fans were tested in the NASA Glenn Research Center 9- by 15-Foot Low-Speed Wind Tunnel (9×15 LSWT) over the last decade. In all cases, sideline as well as in-duct acoustic measurements were acquired and have been used for the comparison purposes in this study. Owing to the limitations of the codes, only data from the so-called hard- wall configurations, which do not include acoustic treatment inside the fan duct, have been considered in this study.
Table 5.1 shows select design parameters for these three model fans. The fan design conditions represent a significant
value range. The ADP fan has a subsonic design tip speed in contrast to the supersonic design tip speeds for the SDT and QHSF 2 fans. Note the change in the fan bypass ratio, pressure ratio, and tip speed for these fans. The design point corrected inlet weight flows5 are similar for all three. The somewhat lower weight flow for the ADP fan is partly due to the higher rotor hub:tip radius ratio and consequent reduced flow area for that fan. All three fans have a 22-in.-diameter rotor and were tested at a number of fan tip speeds. For the purposes of this study, five fan tip speed conditions have been considered for each fan which include speeds that are representative of the three noise certification points; namely, approach, cutback and takeoff, and two additional intermediate tip speeds. The fan tip speeds investigated in this study are listed in Table 5.2.
5
Corrected flow is the mass flow that would pass through the fan if the inlet pressure and temperature were at the standard day conditions (i.e., pressure = 101.4 kPa (14.696 lbf/in.²) and temperature = 288 K (518.7 °R)).
TABLE 5.1.—MODEL FAN STAGE DESIGN PARAMETERS
Parameter Fan stagea
ADP SDT QHSF 2
Fan speed, rpm 8750 12 656 15 625
Corrected tip speed, m/s (ft/s) 256 (840) 370 (1215) 449 (1474)
Stage pressure ratio 1.29 1.47 1.82
Rotor hub-to-tip radius ratio 0.43 0.30 0.35
Bypass ratio 13.3 8.9 3.8
Corrected specific weight flow, kg/m2-s (lbm/ft2-s) 180.2 (36.9) 204.1 (41.8) 213.4 (43.7) Inlet corrected weight flow, kg/s (lbm/s) 38.9 (85.7) 45.6 (100.5) 44.9 (98.9)
Rotor blade count 18 22 22
Fan exit guide vane count 45 54 50
Core inlet guide vane count 63 None None
Bypass and core duct support struts None None 10
aADP is Advanced Ducted Propulsor, SDT is Source Diagnostic Test, and QHSF 2 is Quiet High Speed Fan 2.
TABLE 5.2.—MODEL FAN TIP SPEED CONDITIONS USED IN THIS STUDY
Fana Condition Corrected speed, rpm Design speed, percent ADP Approach 5 425 62.0 --- 6 700 76.6 Cutback 7 525 86.0 --- 8 345 95.4 Takeoff 8 750 100.0 SDT Approach 7 809 61.7 --- 9 493 75.0 Cutback 11 075 87.5 --- 11 771 93.0 Takeoff 12 657 100.0 QHSF 2 Approach 9 840 63.0 --- 10 935 70.0 Cutback 12 500 80.0 --- 13 280 85.0 Takeoff 14 060 90.0
aADP is Advanced Ducted Propulsor, SDT is Source Diagnostic
A photograph of the ADP fan (Refs. 21 and 22), installed in the 9×15 LSWT, is shown in Figure 5.1. ADP has a relatively low stage pressure ratio of 1.29 and a subsonic design corrected tip speed of 256 m/s (840 ft/s), which avoids the generation of multiple pure tones. A three-dimensional exposed view of the fan stage is depicted in Figure 5.2. The fan stage has 18 rotor blades, 45 radial bypass stator vanes, and 63 radial core stator vanes (the core is passive). It has the highest design bypass ratio (13.3) of the three fans considered in this chapter. Figure 5.3 shows a photograph of the SDT fan (Refs. 23 and 24) installed in the 9×15 LSWT. A three- dimensional exposed view of SDT is shown in Figure 5.4. The fan stage has 22 rotor blades (this rotor is called R4) and 54
radial stator vanes. The SDT fan has a design corrected tip speed of 370.3 m/s (1215 ft/s) and a stage pressure ratio of 1.47. Figure 5.5 shows a photograph of the QHSF 2 (Refs. 25 and 26) model installed in the 9×15 LSWT. The three- dimensional exposed view of this fan is depicted in Figure 5.6 showing its relatively close rotor-stator spacing and its swept stator. The QHSF 2 has the highest design tip speed (449.3 m/s, or 1474 ft/s) of the three model fans in this study. It has 22 rotor blades, 50 swept stator vanes, 10 bypass struts, and 10 struts in its passive core. Its bypass ratio of 3.8, well below that of the other two model fans, is considered moderate.
Figure 5.1.—The 22-in.-diameter Advanced Ducted Propulsor (ADP) Fan 1 installed in the NASA 9- by 15-Foot Low-Speed Wind Tunnel. Traversing microphone (located on white stand) is visible to left of model. Microphone moves on track parallel with axis of fan.
Figure 5.2.—Cross-sectional sketch of ADP Fan 1 model. ADP has 18 rotor blades, 45 fan exit guide vanes, and 63 core inlet guide vanes.
Figure 5.3.—The 22-in.-diameter Source Diagnostic Test (SDT) fan installed in NASA 9- by 15-Foot Low-Speed Wind Tunnel.
Figure 5.4.—Cross-sectional sketch of SDT fan model. SDT has 22 rotor blades and 54 fan exit guide vanes.
Figure 5.5.—The 22-in.-diameter Quiet High-Speed Fan 2 (QHSF 2) fan installed in NASA 9- by 15-Foot Low-Speed Wind Tunnel.
Figure 5.6.—Cross-sectional sketch of QHSF 2 model fan. QHSF 2 has 22 rotor blades, 50 fan exit guide vanes, 10 bypass duct struts, and 10 core duct struts.