rotating equipment: pumps, compressors, &...

Rotating Equipment: Pumps, Compressors, &

Turbines/Expanders

Chapters 2 & 9

Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])

TopicsFundamentals

▪ Starting relationships

• Thermodynamic relationships

• Bernoulli’s equation

▪ Simplifications

• Pumps – constant density compression

• Compressors – reversible ideal gas compression

▪ Use of PH & TS diagrams

▪ Multistaging

Efficiencies

▪ Adiabatic/isentropic vs. mechanical

▪ Polytropic

Equipment

▪ Pumps

• Centrifugal pumps

• Reciprocating pumps

• Gear pumps

▪ Compressors

• Centrifugal compressors

• Reciprocating compressors

• Screw compressors

• Axial compressors

▪ Turbines & expanders

• Expanders for NGL recovery

• Gas turbines for power production

o What is “heat rate”?

2


Fundamentals


Review of Thermodynamic Principals1st Law of Thermodynamics – Energy is conserved

▪ (Change in system’s energy) = (Rate of heat added) – (Rate of work performed)

▪ Major energy contributions

• Kinetic energy – related to velocity of system

• Potential energy – related to positon in a “field” (e.g., gravity)

• Internal energy – related to system’s temperature

o Internal energy, U, convenient for systems at constant volume & batch systems

o Enthalpy, H = U+PV, convenient for systems at constant pressure & flowing systems

4

E Q W = −

= + +2

ˆ ˆ2 c c

u gE U h

g g

= + +2

ˆ ˆ2 c c

u gE H h

g g


Review of Thermodynamic Principals

2nd Law of Thermodynamics▪ In a cyclic process entropy will either stay the same (reversible process) or

will increase

Relationship between work & heat▪ All work can be converted to heat, but…

▪ Not all heat can be converted to work

5


Common Paths for Heat and Work

6

Isothermal constant temperature ΔT = 0

Isobaric constant pressure ΔP = 0

Isochoric constant volume ΔV = 0

Isenthalpic constant enthalpy ΔH = 0

Adiabatic no heat transferred Q = 0

Isentropic(ideal reversible)

no increase in entropy ΔS = 0


1st Law for steady state flowEquation 1.19a (ΔH ΔU for flowing systems)

For adiabatic, steady-state, ideal (reversible) flow (using WS as positive value)

▪ The work required is inversely proportional to the mass density

7

2

ˆ2 c c

u gH z Q W

g g

+ + = −

2

1

2 2

1 1

2

2

ˆ ˆ2

ˆ2

ˆ ˆ

s

c c

P

c cP

P P

s

P P

u gW H z

g g

u gV dP z

g g

dPW V dP

= + +

= + +

=


Thermodynamics of Compression

Work depends on path – commonly assume adiabatic or polytropic compression

Calculations done with:▪ PH diagram for ΔH

▪ Evaluate integral using equation of state

• Simplest gas EOS is the ideal gas law

• Simplest liquid EOS is to assume incompressible (i.e., constant density with respect to pressure)

8

= = 2

1

P

s

P

W VdP H

−= = =

2 2

1 1

2 11P P

s

P P

dP P PW dP


Liquid vs. Vapor/Gas Compression

Can compress liquids with little temperature change

9

GPSA Data Book, 13th ed.

ΔH for gas compression much

larger than for liquid pumping


Mechanical Energy BalanceDifferential form of Bernoulli’s equation for fluid flow (energy per unit mass)

▪ Frictional loss term is positive

▪ Work term for energy out of fluid – negative for pump or compressor

If density is constant then the integral is straight forward – pumps

If density is not constant then you need a pathway for the pressure-density relationship – compressors

10

( )( ) ( )

2

ˆˆ 02

s f

d u dPg dz d w g d h+ + + + =

( )2

ˆˆ 02

s f

u Pg z w g h

+ + + + =

( ) 2

1

2

ˆˆ 02

P

s f

P

u dPg z w g h

+ + + + =


Pump equationsPumping requirement expressed in terms of power, i.e., energy per unit time

Hydraulic horsepower – power delivered to the fluid

▪ Over entire system

▪ Just across the pump, in terms of pressure differential or head:

Brake horsepower – power delivered to the pump itself

11

( ) ( )( )

( ) ( )( ) ( )( ) ( )( )

= − = + + +

= + + +

2

hhp

2

ˆˆ2

1ˆ2

s f

f

u PW m w V g z g h

V P V g z V g h V u

( )= = hhp hhp or W V P W V gH

=

hhp

bhp

pump

WW


Pump equations for specific U.S. customary unitsU.S. customary units usually used are gpm, psi, and hp

Also use the head equation usually using gpm, ft, specific gravity, and hp

12

=

3

fhhp 2

f2

f

in231

gallbgalhp

min in ft lb / secsec in60 12 550

min f

lb1 gal

1714 min in

t hp

W

=

m

2

hhpmf

2f

lb ft8.33719 32.174galgal sechp ft

lb ftmin f

1 galft

39

t lb / secsec 32.17460 550lb secmin

58

hp

mino

oW


Static Head Terms

13

Fundamentals of Natural Gas Processing, 2nd ed.Kidnay, Parrish, & McCartney


Pump ExampleLiquid propane (at its bubble point) is to be pumped from a reflux drum to a depropanizer.

▪ Pressures, elevations, & piping system losses as shown are shown in the diagram.

▪ Max flow rate 360 gpm.

▪ Propane specific gravity 0.485 @ pumping temperature (100oF)

▪ Pump nozzles elevations are zero & velocity head at nozzles negligible

What is the pressure differential across the pump? What is the differential head?What is the hydraulic power?

14

GPSA Data Book, 13th ed.


Pump ExamplePressure drop from Reflux Drum to Pump inlet:

Pressure drop from Pump outlet to Depropanizer:

15

( )

( )( ) ( )

piping

inlet

0.485 62.3665 200.5 0.2

1443.5 psi

203.5 psia

c

gP z P

g

P

= − +

− = − + − −

=

=

( )

( )( ) ( )

piping

outlet

0.485 62.3665 743.0 2.0 1.2 13.0 1.0 9.0

14444.7 psi

264.7 psia

c

gP z P

g

P

= − +

= − − + + + + +

= −

=


Pump ExamplePump pressure differential:

Pump differential head:

Hydraulic power:

16

( ) outlet inletpump

264.7 203.5 61.2 psi

P P P = −

= − =

( ) ( )

( )

( )

( )( )( )

pump pump

pump

14461.2 291 ft

0.485 62.3665

c c

o water

P Pg gh

g g

= =

= − =

( )( ) ( )( )( )hhp hhp

360 gpm 61.2 psi 360 gpm 0.485 291 ft12.85 hp OR 12.84 hp

1714 3958W W= = = =


Gas Compression:PH Diagrams

17

Ref: GPSA Data Book, 13th ed.


TS Diagram

18


Thermodynamics of Ideal Gas Compression

Choices of path for calculating work:

▪ Isothermal (ΔT = 0)

• Minimum work required but unrealistic

▪ Adiabatic & Isentropic (ΔS = 0)

• Maximum ideal work but more realistic

▪ Polytropic – reversible but non-adiabatic

• Reversible work & reversible heat proportionately added or removed along path

• More closely follows actual pressure-temperature path during compression

19

= = =

2 2

1 1

2

1

lnP P

s

P P

dP PW VdP RT RT

P P



Ideal gas isentropic (PV = constant) where = CP/CV

▪ Molar basis

▪ Mass basis

Can also determine discharge temperature

20

( )( )−

= − −

1 /

21

1

11

s

PW RT

P

( )− = = −

−

1 /

1 2

1

ˆ 11

ss

W RT PW

M M P

( )−

=

1 /

22 1

1

PT T

P



Calculation of for gas mixture

Use the ideal gas heat capacities, not the real gas heat capacities

Heat capacities are functions of temperature. Use the average value over the temperature range

21

, ,

, ,

i p i i p i

i V i i p i

x C x C

x C x C R = =

−


Example Calculation:Ideal Gas Laws

For methane:▪ = 1.3

▪ M = 16

▪ T1 = 120oF = 580oR

▪ P1 = 300 psia

▪ P2 = 900 psia

▪ R = 1.986 Btu/lb.mol oR

22

( )

( )( )( )( )

( )( )

( )

( )( )

− −

−

= − = − =

− −

= =

1 / 1.3 1 /1.3

1 2

1

1.3 1 /1.3

2

1.3 1.986 580 9001 1 90 Btu/lb

1 16 1.3 1 300

900580 747°R 287°F

300

s

RT PW

M P

T

440 BTU/lb

525 BTU/lb

Enthalpy Changes:

𝑊 = ∆𝐻 = 525 − 440 = 85𝐵𝑇𝑈

𝑙𝑏Outlet temperature: 280°F

Compress methane from 300 psia & 120°F to 900 psia


Example Calculation:Using a Simulator

Work Btu/lb Outlet oF

HYSYS Peng-Robinson 86.58 281.8

HYSYS Peng-Robinson & Lee-Kesler 87.34 280.5

HYSYS SRK 87.71 281.2

HYSYS BWRS 87.04 281.1

HYSYS Lee-Kesler-Plocker 87.40 280.6

Aspen Plus PENG-ROB 86.61 282.4

Aspen Plus SRK 87.82 281.8

Aspen Plus BWRS 87.10 281.6

24


Multi-Stage Gas Compression

If customer wants 1,000 psig (with 100 psig & 120oF inlet)…▪ Then pressure ratio of (1015/115) = 8.8

▪ Discharge temperature for this ratio is ~500oF

For reciprocating compressors the GPSA Engineering Data Book recommends ▪ Pressure ratios of 3:1 to 5:1 AND …

▪ Maximum discharge temperature of 250 to 275oF for high pressure systems

To obtain higher pressure ratios higher must use multistage compression with interstage cooling

25


MultistagingTo minimize work need good interstage cooling and equal pressure ratios

The number of stages is calculated using

To go from 100 to 1000 psig with a single-stage pressure ratio of 3 takes 2 (1.98) stages & the stage exit temp ~183oF (starting @ 120oF)

26

( )

( )

1/

2 12

1

ln /

ln

m

P

P

P PPm

P

= =

RR

( )

( )

( )

( )

( )

( )

( )

− −

= = = =

= = + = =

1 / 1.3 1 /1.31/ 1/20.23082

2 1

1

1015ln

ln 8.81151.98 2

ln 3 ln 3

1015120 460 580 2.97 746°R 286°F

115

m

m m

PT T

P


Multistaging

Work for a single stage of compression

Work for two stages of compression (interstage cooling to 120oF)▪ Intermediate pressure

▪ Total work – 13% less work

27

( )

( )( )( )( )

( )( )

( )1 / 1.3 1 /1.3

1 2

1

1.3 1.986 580 1015ˆ 1 1 204 Btu/lb1 16 1.3 1 115

s

RT PW

M P

− − = − = − =

− −

( )( )int 2 1 1015 115 341.7 psiaP P P= = =

( )( )( )

( )( )

( ) ( )1.3 1 /1.3 1.3 1 /1.31.3 1.986 580 341.7 1015ˆ 1 1

16 1.3 1 115 341.7

178 Btu/lb

sW− −

= − + − −

=


Compression EfficiencyCompression efficiencies account for actual power required compared to ideal

▪ Isentropic (also known as adiabatic) efficiency relates actual energy to fluid to energy for reversible compression

▪ Mechanical efficiency relates total work to device to the energy into the fluid

28

( )

( )0 0

IS

IS

S Sfluid

fluid

H WW

H = =

= =

TotalEnergy

ToDevice

EnergyLostTo

Environment

Minimum Energy for Compression

Energy to Overcome Mechanical Inefficiencies – GoesInto Fluid & Increases Temperature{ Total

Energy IntoFluid

0mech

mech mech IS

fluid fluid Stotal

total

W W WW

W = = = =


Compressor Efficiency – Discharge Temperature

GPSA Engineering Data Book suggests the isentropic temperature change should be divided by the isentropic efficiency to get the actual discharge temperature

29

( )( ) ( )1 / 1 /

2 21 1 10

1 1

1S

P PT T T T

P P

− −

=

= − = −

( )( )

( )

( )

( )

1 /

2

101

IS IS

1 /

2

12, 1 1

IS

1

So:

1

1

S

act

act act

P

T PT T

P

PT T T T

−

=

−

−

= =

−

= + = +


Example Calculation:75% isentropic efficiency

ΔS =0Work Btu/lb

ΔS =0Outlet oF

=0.75Work Btu/lb

=0.75Outlet oF

Ideal Gas Equations 90 287 120 343

PH diagram 85 280 113 325

HYSYS Peng-Robinson 86.58 281.8 115.4 325.2

HYSYS SRK 87.71 281.2 116.9 325.2

HYSYS BWRS 87.04 281.1 116.1 325.1

HYSYS Lee-Kesler-Plocker 87.40 280.6 116.5 324.8

30


Polytropic Compression & Efficiency

Definition of polytropic compression (GPSA Data Book 14th ed.):

A reversible compression process between the compressor inlet and discharge conditions, which follows a path such that, between any two points on the path, the ratio of the reversible work input to the enthalpy rise is constant. In other words, the compression process is described as an infinite number of isentropic compression steps, each followed by an isobaric heat addition. The result is an ideal, reversible process that has the same suction pressure, discharge pressure, suction temperature and discharge temperature as the actual process.

31


Polytropic Efficiency

Polytropic path with 100% efficiency is adiabatic & is the same as the isentropic path▪ Polytropic efficiency, p, is related to the isentropic path

In general P > IS

Polytropic coefficient from discharge temperature

32

( )

( )

−

= =

−

1

2 122 1

1 2 1

ln /1 where

1 ln /

T TPT T

P P P

( )

( )

− =

− P

1 /

1 /


Polytropic Efficiency

Actual work is calculated from the polytropic expression divided by its efficiency

Note:

33

( )1 /

1 2

1

ˆ 1ˆ 11

p

act

p p

W RT PW

M P

− = = −

−

0ˆ ˆ

ˆ p Sact

p IS

W WW == =


Why Use Polytropic Equations?

Polytropic equations give consistent P-T pathway between the initial & discharge conditions

34


Effect of Internal Pressure Drops

Pressure drops at the inlet & outlet give an apparent inefficiency of compression▪ Assume isenthalpic pressure drops before & after the actual compression

35


Effect of Internal Pressure Drops

Pressure Reductions

Before Compression

psia

After Compression

psiaWorkBtu/lb

Outlet °F

Efficiency

0% 300 900 86.58 281.8 100%

1% 297 909 88.36 284.7 98%

5% 285 947 95.76 296.8 90%

10% 270 1000 105.7 313.0 82%

15% 255 1059 116.5 330.2 74%

36


Compression vs. Expansion Efficiency

Work to compressor is greaterthan what is needed in the ideal case▪ Work to the fluid

▪ Total work to the device

Work from expander is lessthan what can be obtained in the ideal case▪ Work from the fluid

▪ Total work from the device

37

( )

( )0 0

IS

IS

S Sfluid

fluid

H WW

H = =

= =

mech

0

mech mech IS

fluid

total

fluid Stotal

W

W

W WW =

=

= =

( )

( )( )IS IS 0

0

fluid

fluid S

S

HW W

H =

=

= =

mech

mech mech IS 0

total

fluid

total fluid S

W

W

W W W =

=

= =


Equipment:Pumps, Compressors, Turbines/Expanders


Pump & Compressor Drivers

Internal combustion engines▪ Industry mainstay from

beginning

▪ Emissions constraints

▪ Availability is 90 to 95%

Electric motors▪ Good in remote areas

▪ Availability is > 99.9%

Gas turbines▪ Availability is > 99%

▪ Lower emissions than IC engine

Steam turbines▪ Uncommon in gas plants on

compressors

▪ Used in combined cycle and Claus units

39


Pump Classifications

40



Centrifugal Pump Performance Curves

41



Compressor TypesPositive displacement –compress by changing volume

▪ Reciprocating

▪ Rotary screw

▪ Diaphragm

▪ Rotary vane

Dynamic – compress by converting kinetic energy into pressure

▪ Centrifugal

▪ Axial

42


Reciprocating CompressorsWorkhorse of industry since 1920’s

Capable of high volumes and discharge pressures

High efficiency – up to 85%

Performance independent of gas MW

Good for intermittent service

Drawbacks▪ Availability ~90 to 95% vs 99+%

for others, spare compressor needed in critical service

▪ Pulsed flow

▪ Pressure ratio limited, typically 3:1 to 4:1

▪ Emissions control can be problem (IC drivers)

▪ Relatively large footprint

▪ Throughput adjusted by variable speed drive, valve unloading or recycle unless electrically driven

43


Reciprocating Compressors - Principle of Operation

Double Acting – Crosshead

Typical applications:

▪ All process services, any gas & up to the highest pressures & power

Single Acting - Trunk Piston

Typical Applications:▪ Small size standard compressors

for air and non-dangerous gases

44

Courtesy of Nuovo Pignone Spa, Italy


Reciprocating Compressors - Compression Cycle

45

Suction

Discharge

1

1

2

2 3

3

4

54

5

p0

Pre

ssure

Volume



Reciprocating Compressors - Main Components

46

Pulsation BottlesCrosshead

Cast SteelCrankcase

Cast Iron

Distance Pieces

Slide Body

Connecting Rod

(die forged steel)

Forged

Cylinder

Crankshaft

Forged Steel

Cast

Cylinder

Main Oil Pump

Piston Rod

Rod Packing

PistonCylinder Valve

Counterweight

for balancing Ballast for

balancing ofinertia forces

Pneumatic

Valve

Unloaders

for capacity

control

Oil Wiper

Packing


Reciprocating Compressors

47

https://www.youtube.com/watch?v=E6_jw841vKE

https://www.youtube.com/watch?v=E6_jw841vKE


Rotary Screw CompressorLeft rotor turns clockwise, right rotor counterclockwise.Gas becomes trapped in the central cavity

The Process Technology Handbook, Charles E. Thomas,UHAI Publishing, Berne, NY, 1997.

48

Courtesy of Ariel Corp


Rotary Screw CompressorsOil-free

First used in steel mills because handles “dirty” gases

Max pressure ratio of 8:1 if liquid injected with gas

High availability (> 99%)▪ Leads to low maintenance cost

Volumetric efficiency of ~100%

Small footprint (~ ¼ of recip)

Relatively quiet and vibration-free

Relatively low efficiency▪ 70 – 85% adiabatic efficiencies

Relatively low throughput and discharge pressure

Oil-injected

Higher throughput and discharge pressures

Has two exit ports

▪ Axial, like oil-free

▪ Radial, which permits 70 to 90% turndown without significant efficiency decrease

Pressure ratios to 23:1

Tight tolerances can limit quick restarts

Requires oil system to filter & cool oil to 140oF

Oil removal from gas

Oil compatibility is critical

Widely used in propane refrigeration systems, low pressure systems, e.g., vapor recovery, instrument air

49


Dynamic Compressors

Centrifugal ▪ High volumes, high discharge pressures

Axial▪ Very high volumes, low discharge pressures

Use together in gas processing▪ Centrifugal for compressing natural gas

▪ Axial for compressing air for gas turbine driving centrifugal compressor

50


Centrifugal compressors

Single stage (diffuser) Multi-stage

51

Bett,K.E., et al Thermodynamics for Chemical Engineers Page 226


Centrifigual Compressor

52

Siemenshttps://www.energy.siemens.com/br/en/compression-expansion/product-lines/single-stage/stc-sof.htm

https://www.youtube.com/watch?v=s-bbAoxZmBg

https://www.energy.siemens.com/br/en/compression-expansion/product-lines/single-stage/stc-sof.htm

https://www.youtube.com/watch?v=s-bbAoxZmBg


Centrifugal Compressor

53



Centrifugal vs. Reciprocating CompressorsCentrifugal

Constant head, variable volume

Ideal for variable flow

- MW affects capacity

++ Availability > 99%

+ Smaller footprint

- ηIS = 70 – 75%

CO & NOx emissions low

- Surge control required

++ Lower CAPEX and maint.

(maint cost ~1/4 of recip)

ReciprocatingConstant volume, variable pressure

Ideal for constant flow

+ MW makes no difference

- Availability 90 to 95%

- Larger footprint

+ ηIS = 75 – 92%

Catalytic converters needed

++ No surge problems

++ Fast startup & shutdown

54


Turbines & Turboexpanders

Utilize pressure energy to…▪ Reduce temperature of gas & (possibly) generate liquids

▪ Perform work & provide shaft power to coupled equipment

Similar principles to a centrifugal compressor except in reverse

Most common applications:▪ Turboexpander: NGL recovery

▪ Gas turbine: power to drive pumps, compressors, generators, …

55


Turboexpander Cutaway

56

https://www.turbomachinerymag.com/expander-compressors-an-introduction/

Video (LA Turbine. 2:54 minutes): https://www.youtube.com/watch?v=f5Gz_--_NBM

https://www.turbomachinerymag.com/expander-compressors-an-introduction/

https://www.youtube.com/watch?v=f5Gz_--_NBM


Turboexpanders

GPSA Engineering Data Book, 14th ed.


Methane Expansion – Isentropic vs. Isenthalpic

58


Gas Turbine Engine

59

https://aceclearwater.com/product/case-study-ge-power-ducts/

https://aceclearwater.com/product/case-study-ge-power-ducts/


Gas Turbine Coupled to Centrifugal Compressor

60


Industrial Gas Turbines

61

Ref: GPSA Data Book, 13th ed.


What is “heat rate”?

Heat rate is the amount of fuel gas needed (expressed heating value) to produce a given amount of power▪ Normally LHV, but you need to make sure of the basis

Essentially the reciprocal of the thermal efficiency

▪ Example: Dresser-Rand VECTRA 30G heat rate is 6816 Btu/hp·hr

Includes effects of adiabatic & mechanical efficiencies

62

( )=

2544Thermal efficiency

Btu LHVHeat rate,

hp hr

= =2544

Thermal efficiency 0.37326816


Combustion

chamber

Compressor Turbine Load

Gas Turbine Engine

From: F.W.Schmuidt, R.E. Henderson, and C.H. Wolgemuth,

“Introduction to Thermal Sciences, second edition” Wiley, 1993

shaft shaft

Atmospheric air

Fuel

Combustion

products

Assumptions

To apply basic thermodynamics to the process above, it is necessary to make a number of

assumptions, some rather extreme.

1) All gases are ideal, and compression processes are reversible and adiabatic (isentropic)

2) the combustion process is constant pressure, resulting only in a change of temperature

3) negligible potential and kinetic energy changes in overall process

4) Values of Cp are constant

P1

P2

P3

P4

Gas Turbine Engine

63


Te

mp

era

ture

T

Entropy S

P2 = P3

Patm = P1 = P4

1

2

3

4

wS = -∆h = -CP∆T (9.1 and 1.18)

Note the equations apply to both the compressor and the turbine,since

thermodynamically the turbine is a compressor running backwards

Neglecting the differences in mass flow rates between the compressor and

the turbine, the net work is:

wnet = wt – wc = CP(T3 – T4) – (T2 -T1)

Since (T3 – T4) > (T2 – T1) (see T – S diagram)

Since wnet is positive work flows to the load

Gas Turbine Engine

64


GT - Principle of Operation

65

Simple Cycle Gas Turbine

4

3

2

A B

Temperature °F

Entropy

1

Theoretical Cycle

Axial

Compressor

Combustion Chamber

H.P./L.P. Turbine

Fuel Gas

Air

Exhaust Gas (~950°F)

1

34

~1800 -2300°F

~650 - 950°F

Ideal Cycle Efficiency

Real Cycle

Centrifugal

Compressor

2

( )1 /

4 1 1

3 2 2

1 1id

T T P

T T P

−

− = − = −

−


Modeling Gas Turbine with Aspen Plus

Basics to tune model▪ Combine heat rate & power output to determine the fuel required

▪ Determine the air rate from the exhaust rate

▪ Adjust adiabatic efficiencies to match the exhaust temperature

▪ Adjust the mechanical efficiencies to match the power output

66


Summary


SummaryWork expression for pump developed assuming density is not a function of pressure

Work of compression is much greater than that for pumping – a great portion of the energy goes to increase the temperature of the compressed gas

Need to limit the compression ratio on a gas

• Interstage cooling will result in decreased compression power required

• Practical outlet temperature limitation – usually means that the maximum compression ratio is about 3

There are thermodynamic/adiabatic & mechanical efficiencies

• Heat lost to the universe that does affect the pressure or temperature of the fluid is the mechanical efficiency

68


Supplemental Slides


Reciprocating Compressors

70


Propane Refrigeration Compressors

71


Propane Compressors with Air-cooled Heat Exchangers

72


Reciprocating Compressor at Gas Well

73



2 stage 2,000 HP Reciprocating Compressor

74



Oil-Injected Rotary Screw Compressor

75



Two-stage screw compressor

76

Courtesy of MYCOM / Mayekawa Mfg


Centrifugal Compressors – Issues Surge

• Changes in the suction or outlet pressures can cause backflow; this can become cyclic as the compressor tries to adjust. The resulting pressure oscillations are called SURGE

Stonewall

• When gas flow reaches sonic velocity flow cannot be increased.

Inlet Volume Flow

Rate

Pre

ss

ure

He

ad

Su

rge L

ine

Sto

ne

wa

ll L

ine

Centrifugal

Reciprocating

Axial

77


Air & Hot Gas PathsGas Turbine has 3 main sections:

A compressor that takes in clean outside air and then compresses it through a series of rotating and stationary compressor blades

78

EXHAUSTFRESH AIR

MECHANICALENERGY

COMPRESSION



A combustion section where fuel is added to the pressurized air and ignited. The hot pressurized combustion gas expands and moves at high velocity into the turbine section.

79

EXHAUSTFRESH AIR

MECHANICALENERGY

COMBUSTION

COMPRESSION



A turbine that converts the energy from the hot/high velocity gas flowing from the combustion chamber into useful rotational power through expansion over a series of turbine rotor blades

80

EXHAUSTFRESH AIR

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