C_4_Selection-压气机设计初步类型选取原则
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n /(n 1) 3.5 * 0.857 3, pt 3 pt1 (1 0.4 * 0.65 *1.0 2 ) 3 2.000 Tt1 20 C 293.1 K , at1 RTt1 1306.1 m/s, u 2 1306.1 m/s !!!
• Limited by mechanical properties
– A non-dimensional enthalpy rise and flow for a certain impeller size and tip speed: V hs t1 2t1 s 2 • Head rise Flow D2 u2 u2 coefficient coefficient – A non-dimensional angular velocity or size for a given volume flow and head 1 1 rise: 2 4 Vt1 h s • Specific Specific s Ds D2 3 1 speed diameter h 4 2
• Refrigeration applications not limited by mechanical properties
– At 340 m/s a very high pressure rise
M u 2 2.143,
pt 3 pt1 (1 0.216 * 0.65 * 2.1432 ) 4,82 11.0
– Gas properties • Molecular weight / Toxicity – Available design experience – International standards – Available driver (motor, gas turbine, steam turbine, turbocharger turbine) – Economics: initial cost, energy costs and operating costs – Size – Available materials – Maximum allowable operating speed – Requirements on the performance map (operating range, efficiency) – Application (for example, low frontal area and weight in jet engines)
Page 1
C_4: Compressor selection
C_4.1 Influences on the design C_4.2 Cordier or Balje diagram C_4.3 Effect of gas properties
Michael Casey
Version: August 2015
Compressors (C) C_4: Compressor selection
Prof. Michael Casey MA, DPhil, FIMechE, CEng, FASME
Retired Professor of Thermal Turbomachinery in the University of Stuttgart
An educational course on compressors based on lectures given by the author in the University of Stuttgart
Michael Casey
Version: August 2015
Compressors C_4_Selection
– Pressure ratio usually limited by Mach number
Michael Casey
Version: August 2015
Compressors
C_4_Selection
Page 8
C_4.1.7
Pressure ratio with low molecular weight gas
Michael Casey
Version: August 2015
Compressors
C_4_Selection
Page 4
C_4.1.3
Effect of radial compressor speed and size
Microcompressors Small turbocharger compressors n 60u2 / D2 Large turbocharger compressors Classical process compressors 1000000
– At 340 m/s hardly any pressure rise at all
M u 2 0.263,
pt 3 pt1 (1 0.4 * 0.65 * 0.2632 )3 1.055
– At least 13 stages needed for a pressure ratio of 2 at 340 m/s
RT – Radial Turbocompressor
Suction Volume Nm3 / s
Michael Casey
Version: August 2015
Compressors
C_4_Selection
Page 6
C_4.1.5
Effect of gas on pressure ratio
Gas : CH 2 FClF3 , M 102.0, R 8314.4 / 102 81.5 J/kg/K
1.216, ( 1) 5.63, p 0.857, 0.65, M u 2 1.0
n /(n 1) 5.63 * 0.857 4.82, pt 3 pt1 (1 0.216 * 0.65 *1.0 2 ) 4.82 1.88 Tt1 20 C 293.1 K , at1 160.1 m/s, u 2 160.1 m/s
• Pressure ratio depends on blade speed and speed of sound
– For fixed speed we get • More pressure ratio on a cold day
at1 RTt1
• (see chapter C_3 for derivation of the equation above) Michael Casey
Selection diagram for industrial compressor types
• Standard types from MAN Turbo
Discharge Pressure (bara)
600 400 200 100 60 40 20 10 6,0 4,0 2,0 0,4 1,0 2,0 4,0 10 20 40 60 100 200 400
ln(2) / ln(1.055) 12.9
Michael Casey
Version: August 2015 Compressors C_4_Selection Page 9
C_4.2.1
How do we determine the size, speed and type of machine?
0.65, M u 2 1.0, 1.4, ( 1) 3.5 p 6 / 7 0.857, n /(n 1) 3.5 * 0.857 3.0
pt 3 pt1 (1 0.4 * 0.65 *1.0 2 ) 3 2.000 Tt1 20 C 293.1 K, at1 RTt1 343.2 m/s, u2 343.2 m/s
pt 3 pt1 1 ( 1)M
2 n /( n 1) u2
• Hydrogen compressor – low molecular weight gas
Gas : H 2 , M 2, R 8314.4 / 2 4157.2 J/kg/K
1.4, ( 1) 3.5, p 0.857, 0.65, M u 2 1.0
u2 r2 ( D2 / 2)
• These can be combined into four useful dimensionless groups and particular choices of these dimensionless parameters are advantageous
s
V
t1
Michael Casey
Version: August 2015
Compressors
C_4_Selection
Page 3
C_4.1.2
Other influences on the design
• Compression tasks can often be met with different designs. • The technical choice of design and type is influenced not only by the non-dimensional coefficients but also influenced by
Standard Compressor Types
R – Radial A – Axial AV - Axial mit verstellbaren Leitschaufeln B - Barrel Z - Cooling S – Sidestream RIK – Radial with integrated cooler
u2 r2
Speed [rpm]
n 100000
10000
u2 m / s
200 320 500
1000
10
100
1000
Diameter [mm] D2
M百度文库chael Casey
Version: August 2015 Compressors C_4_Selection Page 5
C_4.1.4
Version: August 2015 Compressors C_4_Selection Page 7
C_4.1.6
Pressure ratio with high molecular weight gas
pt 3 pt1 1 ( 1)M
2 n /( n 1) u2
• Refrigeration compressor – high molecular weight gas
Compressors
C_4_Selection
Page 2
C_4.1.1
Influence of design data
• Four key items of data are needed to specify a single-stage compressor application:
– – – – The pressure rise, or isentropic enthalpy rise, hs The inlet volume flow rate, V t1 The rotor casing diameter at impeller outlet, D2 The rotor angular velocity, or blade tip-speed
pt 3 pt1 1 ( 1)M
2 n /( n 1) u2
• Radial compressor with air at 20°C and tip speed Mach number of 1.0
Gas : Air, M 28.97, R 8314.4 / 28.97 287.1 J/kg/K
• Limited by mechanical properties
– A non-dimensional enthalpy rise and flow for a certain impeller size and tip speed: V hs t1 2t1 s 2 • Head rise Flow D2 u2 u2 coefficient coefficient – A non-dimensional angular velocity or size for a given volume flow and head 1 1 rise: 2 4 Vt1 h s • Specific Specific s Ds D2 3 1 speed diameter h 4 2
• Refrigeration applications not limited by mechanical properties
– At 340 m/s a very high pressure rise
M u 2 2.143,
pt 3 pt1 (1 0.216 * 0.65 * 2.1432 ) 4,82 11.0
– Gas properties • Molecular weight / Toxicity – Available design experience – International standards – Available driver (motor, gas turbine, steam turbine, turbocharger turbine) – Economics: initial cost, energy costs and operating costs – Size – Available materials – Maximum allowable operating speed – Requirements on the performance map (operating range, efficiency) – Application (for example, low frontal area and weight in jet engines)
Page 1
C_4: Compressor selection
C_4.1 Influences on the design C_4.2 Cordier or Balje diagram C_4.3 Effect of gas properties
Michael Casey
Version: August 2015
Compressors (C) C_4: Compressor selection
Prof. Michael Casey MA, DPhil, FIMechE, CEng, FASME
Retired Professor of Thermal Turbomachinery in the University of Stuttgart
An educational course on compressors based on lectures given by the author in the University of Stuttgart
Michael Casey
Version: August 2015
Compressors C_4_Selection
– Pressure ratio usually limited by Mach number
Michael Casey
Version: August 2015
Compressors
C_4_Selection
Page 8
C_4.1.7
Pressure ratio with low molecular weight gas
Michael Casey
Version: August 2015
Compressors
C_4_Selection
Page 4
C_4.1.3
Effect of radial compressor speed and size
Microcompressors Small turbocharger compressors n 60u2 / D2 Large turbocharger compressors Classical process compressors 1000000
– At 340 m/s hardly any pressure rise at all
M u 2 0.263,
pt 3 pt1 (1 0.4 * 0.65 * 0.2632 )3 1.055
– At least 13 stages needed for a pressure ratio of 2 at 340 m/s
RT – Radial Turbocompressor
Suction Volume Nm3 / s
Michael Casey
Version: August 2015
Compressors
C_4_Selection
Page 6
C_4.1.5
Effect of gas on pressure ratio
Gas : CH 2 FClF3 , M 102.0, R 8314.4 / 102 81.5 J/kg/K
1.216, ( 1) 5.63, p 0.857, 0.65, M u 2 1.0
n /(n 1) 5.63 * 0.857 4.82, pt 3 pt1 (1 0.216 * 0.65 *1.0 2 ) 4.82 1.88 Tt1 20 C 293.1 K , at1 160.1 m/s, u 2 160.1 m/s
• Pressure ratio depends on blade speed and speed of sound
– For fixed speed we get • More pressure ratio on a cold day
at1 RTt1
• (see chapter C_3 for derivation of the equation above) Michael Casey
Selection diagram for industrial compressor types
• Standard types from MAN Turbo
Discharge Pressure (bara)
600 400 200 100 60 40 20 10 6,0 4,0 2,0 0,4 1,0 2,0 4,0 10 20 40 60 100 200 400
ln(2) / ln(1.055) 12.9
Michael Casey
Version: August 2015 Compressors C_4_Selection Page 9
C_4.2.1
How do we determine the size, speed and type of machine?
0.65, M u 2 1.0, 1.4, ( 1) 3.5 p 6 / 7 0.857, n /(n 1) 3.5 * 0.857 3.0
pt 3 pt1 (1 0.4 * 0.65 *1.0 2 ) 3 2.000 Tt1 20 C 293.1 K, at1 RTt1 343.2 m/s, u2 343.2 m/s
pt 3 pt1 1 ( 1)M
2 n /( n 1) u2
• Hydrogen compressor – low molecular weight gas
Gas : H 2 , M 2, R 8314.4 / 2 4157.2 J/kg/K
1.4, ( 1) 3.5, p 0.857, 0.65, M u 2 1.0
u2 r2 ( D2 / 2)
• These can be combined into four useful dimensionless groups and particular choices of these dimensionless parameters are advantageous
s
V
t1
Michael Casey
Version: August 2015
Compressors
C_4_Selection
Page 3
C_4.1.2
Other influences on the design
• Compression tasks can often be met with different designs. • The technical choice of design and type is influenced not only by the non-dimensional coefficients but also influenced by
Standard Compressor Types
R – Radial A – Axial AV - Axial mit verstellbaren Leitschaufeln B - Barrel Z - Cooling S – Sidestream RIK – Radial with integrated cooler
u2 r2
Speed [rpm]
n 100000
10000
u2 m / s
200 320 500
1000
10
100
1000
Diameter [mm] D2
M百度文库chael Casey
Version: August 2015 Compressors C_4_Selection Page 5
C_4.1.4
Version: August 2015 Compressors C_4_Selection Page 7
C_4.1.6
Pressure ratio with high molecular weight gas
pt 3 pt1 1 ( 1)M
2 n /( n 1) u2
• Refrigeration compressor – high molecular weight gas
Compressors
C_4_Selection
Page 2
C_4.1.1
Influence of design data
• Four key items of data are needed to specify a single-stage compressor application:
– – – – The pressure rise, or isentropic enthalpy rise, hs The inlet volume flow rate, V t1 The rotor casing diameter at impeller outlet, D2 The rotor angular velocity, or blade tip-speed
pt 3 pt1 1 ( 1)M
2 n /( n 1) u2
• Radial compressor with air at 20°C and tip speed Mach number of 1.0
Gas : Air, M 28.97, R 8314.4 / 28.97 287.1 J/kg/K