endwall ribs are both tilted toward the downstream direction along the inlet and outlet legs, Fig. 1(b). The sectional twin-vortical flow cells tripped by the two pairs of ribbed endwalls and wavy sidewalls are orthogonal as indicated by the conceptual flow structure shown by Fig. 1(b). Geometric specifications for the ribbed endwall and the wavy sidewall of each twin-pass test channel are characterized by five dimensionless parameters, namely width (W) to channel height (H) ratio of 0.5, 1 or 2, wall-wave amplitude (a) to channel width (W) ratio of 2.4 mm/40 mm = 0.06, wall-wave amplitude (a) to wave-pitch (k) ratio of 2.4/17 mm = 0.14, rib height (e) to rib pitch (P) ratio of 4 mm/40 mm = 10 and rib height (e) to channel hydraulic diameter (d) ratios of 4 mm/
47 mm = 0.085 (AR = 0.5), 4 mm/0.036 mm = 1.11 (AR = 1) and
4 mm/0.025 mm = 1.6 (AR = 2).
The two opposite rib floors (1) and (2) are forged from stainless steel foils into the specified geometry with 0.1 mm thick and
40 mm wide. The basically uniform heat flux over each ribbed end- wall is generated by feeding electrical current through the two stainless steel ribbed foils (1) and (2) which are connected in ser- ies. As the width-to-thickness ratio of each stainless steel foil is about 400, the one-dimensional wall conduction with negligible conductive heat flux through the foil thickness is emulated. The ribbed endwall (1) over which the full-field distributions of wall temperature (Tw) are scanned by the infrared camera is sand- wiched between Teflon end plate (3) and (4), Teflon frame (5) and Teflon divider (6). Another heating foil (2) is attached on Teflon back plate (7). The two Teflon sidewalls (8), two opposite ribbed heating foils (1) and (2), the undulant central divider (6) and the Teflon end plate of the rectangular bend (3) construct the present two-pass test channel. The length and nominal width of Teflon central divider (6) is 209.7 mm and 20 mm, respectively, with the circular top edge of radius 10 mm. The distance between divi- der-tip and the outer edge of the rectangular bend is one channel width of 40 mm for all three test channels. A series of axial bolts and four draw bolts (9) between the outer wall of the rectangular bend and the bottom Teflon end plate (4) are used to tighten the complete test assembly. Prior to the experimental tests, the test section is pressurized to the pressure level required for reaching the maximum Re. With these pressurized tests, both airflow and heat flux are supplied and the scale-plate is used to detect the deformation over the ribbed foil. With present Re range, the de- tected deformations over the ribbed foil are negligible and, in par- ticular, any deformation over the heated rib floor will affect the infrared signal emission, which can be readily identified from the full-field wall temperature scan by present IR thermo-graphic sys- tem. To simulate the abrupt flow entry condition, a cylindrical air plenum chamber (10) with a segregation plate to separate the flow streams into the inlet leg and out of the outlet leg is installed. The sectional area ratio of present flow entrance is 3.53:1. The two ends of each stainless steel heating foil (1) and (2) are clamped be- tween two pairs of copper plates (11) and (12) which connect with the controllable heater power supply. A type K thermocouple (13) is installed inside the entry plenum chamber (10) at the location immediate upstream the entry plane of the inlet leg to measure the inlet fluid temperature. Reynolds number at the flow entry is
determined from the measured air mass flow rate (m_ ) with the
endwall ซี่โครงที่ทั้งสองจะยืดไปทางทิศทางปลายน้ำตามร้านและทางเข้าของขา Fig. 1(b) เซลล์คู่ vortical flow ตัด tripped โดยสองคู่ endwalls รม และ sidewalls หยักเป็น orthogonal ตามที่ระบุ โดย flow แนวคิดโครงสร้างแสดง โดย Fig. 1(b) Specifications เรขาคณิต ribbed endwall และหยักที่แก้มของแต่ละสถานีทดสอบผ่านทวิมีลักษณะสูง (e) กับซี่โครง pitch (P) อัตราส่วน 4 มม. 40 มม. = 10 และซี่โครง (e) ช่อง โดย five dimensionless พารามิเตอร์ คือความกว้าง (W) ต่ออัตรา 0.5, 1 หรือ 2 กำแพงคลื่นคลื่น (a) อัตราส่วนความกว้าง (W) ช่องของ 2.4 mm / 40 มม. = 0.06 กำแพงคลื่นคลื่น (a) อัตราส่วนช่วงคลื่น (k) ของ 2.4/17 mm = 0.14 ความสูง (H) ช่องซี่โครง อัตราส่วนเส้นผ่าศูนย์กลางไฮดรอลิก (d) มม. 4 /มม. = 0.085 47 (AR = 0.5), 4 mm / 0.036 mm = 1.11 (AR = 1) และมม. 4 มม. 0.025 = 1.6 (AR = 2) floors ซี่โครงข้ามสอง (1) และ (2) ถูกหลอมขึ้นมาจากสแตนเลสฟอยล์เป็นเรขาคณิต specified กับ 0.1 มม.หนา และ40 mm wide. The basically uniform heat flux over each ribbed end- wall is generated by feeding electrical current through the two stainless steel ribbed foils (1) and (2) which are connected in ser- ies. As the width-to-thickness ratio of each stainless steel foil is about 400, the one-dimensional wall conduction with negligible conductive heat flux through the foil thickness is emulated. The ribbed endwall (1) over which the full-field distributions of wall temperature (Tw) are scanned by the infrared camera is sand- wiched between Teflon end plate (3) and (4), Teflon frame (5) and Teflon divider (6). Another heating foil (2) is attached on Teflon back plate (7). The two Teflon sidewalls (8), two opposite ribbed heating foils (1) and (2), the undulant central divider (6) and the Teflon end plate of the rectangular bend (3) construct the present two-pass test channel. The length and nominal width of Teflon central divider (6) is 209.7 mm and 20 mm, respectively, with the circular top edge of radius 10 mm. The distance between divi- der-tip and the outer edge of the rectangular bend is one channel width of 40 mm for all three test channels. A series of axial bolts and four draw bolts (9) between the outer wall of the rectangular bend and the bottom Teflon end plate (4) are used to tighten the complete test assembly. Prior to the experimental tests, the test section is pressurized to the pressure level required for reaching the maximum Re. With these pressurized tests, both airflow and heat flux are supplied and the scale-plate is used to detect the deformation over the ribbed foil. With present Re range, the de- tected deformations over the ribbed foil are negligible and, in par- ticular, any deformation over the heated rib floor will affect the infrared signal emission, which can be readily identified from the full-field wall temperature scan by present IR thermo-graphic sys- tem. To simulate the abrupt flow entry condition, a cylindrical air plenum chamber (10) with a segregation plate to separate the flow streams into the inlet leg and out of the outlet leg is installed. The sectional area ratio of present flow entrance is 3.53:1. The two ends of each stainless steel heating foil (1) and (2) are clamped be- tween two pairs of copper plates (11) and (12) which connect with the controllable heater power supply. A type K thermocouple (13) is installed inside the entry plenum chamber (10) at the location immediate upstream the entry plane of the inlet leg to measure the inlet fluid temperature. Reynolds number at the flow entry isdetermined from the measured air mass flow rate (m_ ) with the
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