Embed Size (px)
Citation preview
11
An efficiency measurement campaignon gearboxes
Steve Dereyne, Pieter Defreyne, Elewijn Algoet, Stijn Derammelaere, Kurt Stockman
2EN 50598‐2
Control
Motivation
• To reduce/optimize energy consumption, total system analysis is needed:
1. load profile analysis2. component loss characterization 3. drive train synthesis
2
3
Motivation
• Research questions related to gearboxes
– Is the rated efficiency in catalogs reliable?
– What about the efficiency at part load operation?
– What is the impact of design parameters, sizing, … on efficiency?
3
4
• Efficiency per gear pair in scientific literature:
94%‐99%
Spur and helical gear
20%‐90%
Worm gear
93%‐99%
Bevel (helical) gear
40%‐90%
Spiroidgear
50%‐95%
Hypoidgear
Bearinglosses
Seal losses
Gear Losses
Churninglosses
• Gearbox efficiency is a combination of losses
4
State of the art
5
• Few info about gearbox efficiency values in catalogs
• No info concerning measurement conditions
• No standardization to measure gearbox efficiency
• Consequence: Efficiency values not comparable
Source: Gear manufacturer catalog
5
Is the rated efficiency in catalogsreliable?
6
• 0,12 kW – 15 kW, 1000Nm, 3000 rpm(under construction: 150 kW, 45 kNm)
• Direct method: back‐to‐back electrical with reducer gearbox
• Efficiency accuracy: ±1%;
• EEMODS 2013, Rio
ratio i = cte. (mech. fixed)
6
Test bench & test procedure
7
• No measurement standards for gearboxes exist• A measurement flowchart was designed:
‐ guarantee accurate and reproducible results
Running‐in procedure
• ±48h• Stabilization of η andat nominal load
• Teeth smoothing
Start‐up procedure
• Restart from Tamb
• Check if ηandare in regime
Efficiency map measurement
• Define measuring grid
• Measure η at regime temperature
7
Test bench & test procedure
8
• Several comparisons: technology; brand; ratio; power
• Overview of tested equipment:
Brand A
Brand B
Brand C
Brand C
Brand C
Brand D
Brand D
Brand E
Brand E
BrandE
Brand F
Brand F
Brand F
Type Right angled
Right angled
Right angled
Right angled
Right angled
Right angled
Right angled
Right angled
Right angled Straight Right
angledRight angled
Right angled
Technology Worm Helical bevel
Helical bevel
Helical worm
Helical spirod
Helical bevel
Helical worm
Helical bevel
Helical worm helical Helical
worm Helical worm
Helical worm
Stages 1 2 3 2 2 3 2 3 2 2 2 2 2
Ratio 80 77.76 72,54 71,75 74,98 72,21 77 11,41 11,67 10,93 87,65 68,44 30,26 Torque (Nm) 450 505 186 167 180 190 180 434 373 390 285 270 260
Power (kW) 0,82 0,95 0,37 0,35 0,36 0,39 0,34 5,58 4,7 5,23 0,69 0,82 1,51 Catalog efficiency 62% 95% 96% 62% ±90% 95% 78% 94% 90% 96% 69% 71% 83%
8
Is the rated efficiency in catalogsreliable?
9
• Efficiency at nominal load and speed• Catalog and measured efficiency value are not equal 9
‐25
0
25
50
75
100
‐11%
+11% ‐8%
‐6%
‐25% ‐8%
‐8%
+2%
+2%
‐1%
‐10% ‐9%
‐4%
Efficiency (%
)
Catalog efficiency Measured efficiencyDelta efficiency
Is the rated efficiency in catalogsreliable?
10
• Internal manufacturer info:
Catalog efficiency≠
Real efficiency
Note: small ratio’s OK
No obligations by standards !
Catalog value
200Nm
800Nm∆4%
∆10%
Is the rated efficiency in catalogsreliable?
11
• Ƞmax nominal torque• Torque ↓ then Ƞ ↓• Speed variation Ƞ=
11
Input speed (rpm)
Out
put t
orqu
e (N
m)
Helical bevel brand D / i72,21 / 3 stage / 1400rpm / 190Nm / 0,39kW
89
88
87
8685
84 83 82 8077
74
86 83
79
736669
76
6168 70
72
8279
76
8685
87
84
0 500 1000 1500 2000 2500 30000
20
40
60
80
100
120
140
160
180
200
Effi
cien
cy (%
)
0
10
20
30
40
50
60
70
80
90
100
Most tested gearboxes have similar efficiency maps
+
Efficiency at part load operation?
12
• Part load efficiency is lower– ∆ƞ smaller for high power and small ratio
12
Input speed (rpm)
Out
put t
orqu
e (N
m)
Helical bevel brand D / i72,21 / 3 stage / 1400rpm / 190Nm / 0,39kW
89
88
87
8685
84 83 82 8077
74
86 83
79
736669
76
6168 70
72
8279
76
8685
87
84
0 500 1000 1500 2000 2500 30000
20
40
60
80
100
120
140
160
180
200
Effi
cien
cy (%
)
0
10
20
30
40
50
60
70
80
90
100
∆8%
Input speed (rpm)
Out
put t
orqu
e (N
m)
Helical brand E / i10,93 / 2 stage / 1400rpm / 390Nm / 5,23kW
94
94
91 91
93
94
95
9595
6584
9092
9390
79
93
94
92
9287
0 500 1000 1500 2000 2500 30000
50
100
150
200
250
300
350
400
Effic
ienc
y (%
)
0
10
20
30
40
50
60
70
80
90
100
∆1,5%
0,4kW; i = 72
5kW; i = 11
• Efficiency equal in larger area for higher power and smaller ratio
Efficiency at part load operation?
13
Comparison of 2 similar gears with ≠ ra oHelical ‐ worm
Catalog: worm gears catalog confirms rated valuesOver the entire operating range !!
Results – Ratio dependency
13
Input speed (%)
Out
put t
orqu
e (%
)
Delta efficiency map / helical worm / brand F / i30.26 - i68.44 / 1400rpm / 260Nm - 270Nm
16
17
1716 17
1718
1818
1919
20
20
2020
21
22
2324
21
2017
0 20 40 60 80 100 120 140 160 180 2000
20
40
60
80
100
Effi
cien
cy(%
)
10
15
20
25
30
i: 30,26 vs. 68,44
Brand F Brand F
Technology Helical worm
Helical worm
Stages 2 2
Ratio 68,44 30,26 Torque (Nm) 270 260
Catalog efficiency 71% 83%
14
Helical ‐ bevel gear: internal manufacturer info
Results – Ratio dependency
14
Ratio ↗: ƞ ↘
Power ↗ : smaller ∆
∆11%
Catalog value
15
• Straight versus right‐angled• Efficiency difference?• Price difference?
Results – Type dependency
15
Brand E
Brand E
BrandE
Type Right angled
Right angled Straight
Technology Helical bevel
Helical worm helical
Stages 3 2 2
Ratio 11,41 11,67 10,93 Torque (Nm) 434 373 390
Power (kW) 5,58 4,7 5,23 Catalog efficiency 94% 90% 96%
Type Right angled Straight Right
angled
Technology Helical bevel Helical Helical
worm Catalog efficiency 94% 96% 90%
Measured efficiency 95,5% 95,5% 91,5%
Price (%) 147 54 98
16
• Commonly known: worm gear efficiencyis low and less than bevel gears (Brand D: Δƞ = 17%)– What is the efficiency difference?– In entire working area?
Measurement:
Results – Technology dependency
16
Brand D
Brand D
Type Right angled
Right angled
Technology Helical bevel
Helical worm
Stages 3 2
Ratio 72,21 77 Torque (Nm) 190 180
Power (kW) 0,39 0,34 Catalog efficiency 95% 78%
+ +
1717
Results – Technology dependency– Bevel vs. worm: i = 72 & i = 77
• Bevel gear efficiency highest, at nominal point + 16%
input speed (rpm)
outp
ut to
rque
(Nm
)
delta efficiency map in % between a helical bevel and a helical worm gearbox (2x brand D; i = 72 & i = 77 resp.; delta = bevel - worm)
12
13
14
1514
12
11
17
21 16
18
16 13
16
15
0 500 1000 1500 2000 25000
20
40
60
80
100
120
140
160
180
200
0
5
10
15
20
25
Large efficiency difference
↓Prefer bevel
gears
Note:• Sometimes self‐
locking from worm gears is desired
• Applications withfew running hours
18
Results – External impacts Temperature
18
• Temperature Tamb ↗ then ƞ ↗ (oil viscosity)
• Type of lubricant ?
• further work required
Measurement:Standard lubrication oil SC320 Energy efficient lubrication
(Grease added with Teflon powder)Results:For a tested helical bevel gear: efficiency +2%For a tested worm gear: efficiency ‐15%Lubrication has an impact
19
Option 1: 4p motor, gear ratio 72,5
– Helical worm gear ƞ = 69%
– Selected motor• Pload x 69% = 609W
• 0,75kW motor; ƞ = 72%
• System efficiency:
• 0,69 x 0,72 = 50%
Option 2: 8p motor, gear ratio 37,5
– Helical worm gear ƞ = 85%
– Selected motor• Pload x 85% = 462W
• 0,55kW motor; ƞ = 66%
– System efficiency:
• 0,85 x 0,66 = 56%Efficiency gain = 6%
How to use the results? A simple conveyor belt drive
19
Conveyor belt200 Nm20 rpm
20
General conclusions
• Lack of information about efficiency of gearboxes– Gearbox test rig a lot of new information
• Gearbox efficiency:– Catalog efficiency’s not always trustworthy
• If you want to be sure: gearbox testing of gearbox models
– A lot of parameters involved• Ratio, type, technology, oil, temperature, etc.
20
21
General conclusions
• Gear selection tips1. If possible, choose a straight gearbox
2. Choose a bevel gearbox
3. Choose ratio as low as possible
21
