Design of a Test Rig to Simulate Flow Through a Ribbed Cooling Passage Todd Beirne, Rob Bellonio, Susan Brewton, Avery Dunigan, Jeff Hodges, Scott Walsh, Al Wilder Advisor: Dr. Karen Thole Graduate Assistant: Evan Sewall Mechanical Engineering Dept. December 11, 2002 This design builds on thermo-fluids principles and previous research Background and Motivation for Design Review of Existing Test Rigs h D e L H h D e L H Overview of Final Rig Design
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Design of a Test Rig to Simulate Flow Through a Ribbed Cooling Passage
Todd Beirne, Rob Bellonio, Susan Brewton, Avery Dunigan, Jeff Hodges, Scott Walsh, Al WilderAdvisor: Dr. Karen Thole Graduate Assistant: Evan SewallMechanical Engineering Dept.December 11, 2002
This design builds on thermo-fluids principles and previous research
Background and Motivation for Design
Review of Existing Test Rigs
hDe
L
HhDe
L
H
Overview of Final Rig Design
2
The Brayton Cycle remains the basis for the modern gas turbine engine
T1
T2
T3
T4
s
T
T3
The material melting points limit the rotor inlet temperature and engine performance
Average inlet temperature:
3000OF
Melting point of metal:
~2400OF
3
The drive to increase inlet temperatures leads to innovative blade design
Improved materials
External film cooling
Internal cooling channels
0
500
1000
1500
2000
Gas Metal Coolant
T (oC)
(3000 oF)Incipient Melt
(2400 oF)(2225 oF)(2200 oF)
2X Life
(1000 oF)
Internal channels have ribs that create complex flow and enhance cooling
Two problems with ribs:
[Tafti, 2002]
Flow behavior difficult to model
Lack of detail limits prediction ability
4
We want to create a large-scale environment that simulates the flow
Our clients include researchers, the government, and the engine industry
5
This design builds on thermo-fluids principles and previous research
Background and Motivation for Design
Review of Existing Test Rigs
hDe
L
HhDe
L
HOverview of Final Rig Design
The arrangement of the ribs in the channel can be defined with several parameters
e
L
H
Aspect Ratio=H:L P
α
νVDRe h=
e
6
Focus: The effect of entrance conditions on the heat transfer coefficient
Features: Constant wall heat fluxUnheated Ribs
Han studied the heat transfer and friction in channels with two opposite rib-roughened walls
20DhTest L
20DhEntrance L7K > Re > 90KRe
90alpha
0.021 > e/Dh >0.063
e/Dh10>P/e>40P/e
1:1Aspect Ratio
Test ValuesParameters
[Han, 1984]
Focus: Flow and heat transfer measurements
Features: Constant heat flux on bottom wall only
Top wall held adiabatic
Watanabe and Takahashi simulated and measured a fully developed ribbed channel flow
0.55 mTest L
0.5 mEntrance L
100,000Re
90alpha
0.10e/Dh
10P/e
2:1Aspect Ratio
Test ValuesParameters
[Watanabe and Takahashi, 2002]
7
Past research provides some guidance for the parameters of our test stand
Parameters Past Research Parameters
Virginia Tech Parameters
Aspect Ratio 0.5-1 1:1P/e 10 10
e/Dh 0.021-0.100 0.100
alpha 30, 45, 60, 90 90
Re 240 -100K 10K-100K
Entrance Length 0-20Dh 10Dh
Test Section Length 7-20Dh 15Dh
Average Temp. Difference 15-30C 10-15C
This design builds on thermo-fluids principles and previous research
Background and Motivation for Design
Review of Existing Test Rigs
hDe
L
HhDe
L
HOverview of Final Rig Design
8
Our design allows the study of flow and thermal patterns in a ribbed channel
10 Dh
15 Dh
10 Dh
Thermal Conditioning
Flow Conditioning
Blower Fan
180o Bend
Lexan surface walls
Orifice Plate
The size of the fan must overcome the pressure losses through the system
Flow direction
Back to fan
9
Two main options exist to determine the flow rate of the air in the channel
Venturi Tube[www.quickpage.com/T/triflo]
Orifice Plate[www.quickpage.com/T/triflo]
10% permanent pressure loss
High cost ($900)
44% permanent pressure loss
Low cost ($250)
A circuit diagram helps to visualize system losses
∑∑∑ ++= other
2i
i
ii
2i
itotal ∆P2
vDLfρ
2vkρ∆P
10
Review of the literature suggests a friction factor for 2-wall ribbed channels
[Han 1984]
WHWfHff rs
++
=
0.40)f(Re4.0logf1
sD10s
e−=
2
e
0.53e
P
r
WH2W2.5ln2.5
D2e2.5ln)0.95(
2f
+
−−−
=
[Han 1984]
The system characteristic curve was used to select the fan
0
2
4
6
8
10
12
0 100000 200000 300000
Reynolds Number
Stat
ic P
ress
ure
(in w
ater
)
11
Air flow can be controlled through a variety of options
Inlet Guide Vanes
0
2
4
6
8
10
12
14
0 100000 200000 300000
Reynolds Num ber
Stat
ic P
ress
ure
(in w
ater
)
Damper
0
2
4
6
8
10
12
0 100000 200000 300000
Reynolds Num ber
Stat
ic P
ress
ure
(in w
ater
)
M otor Speed Control
0
2
4
6
8
10
12
0 100000 200000 300000
Reynolds Num ber
Stat
ic P
ress
ure
(in w
ater
)
Low cost, but will change system curve
Low cost, but low resolution of control
High cost, but highest resolution of control
Several components following the fan cool the air and create uniform flow
Flow direction
Back to fan
12
3–Dimensional diffusion to shorten length
7° diffusion to avoid flow separation
Air from the fan passes through a diffuser to prepare flow for conditioning