1. Turbomachinery Lecture 1 Pumps, Turbines Subcomponents
Units, Constants, Parameters
Thermodynamics
- ME3280 / ME6160

2. Turbomachinery
Turbomachine: A device in which energy is transferred to or from a continuously flowing fluid through a casing by the dynamic action of a rotor.
Rotor or impellor: Changes stagnation enthalpy of fluid moving through it by either doing positive or negative work.
Works on fluid to produce either power or flow
Turbomachine categories:
Those which absorb power to increase fluid pressure or head [compressor, pump].
Fan: pressure rise up to lbf/in2
Blower: pressure between lbf/in2
Compressor: pressure rise above 40 lbf/in2
Those which produce power by expanding fluid to lower pressure or head [turbine].

3. Turbomachinery Turbomachine classification
Impulse: pressure change takes place in one or more nozzles
Reaction: takes place in all nozzles
Path of through flow
Mainly or wholly parallel to axis of rotation: axial flow machine
Mainly or wholly in a plane perpendicular to axis of rotation: radial flow machine

4. Brayton Thermodynamic Cycle for Single Spool Turbojet Engine

5. Meridional Projection of Axial & Centrifugal Compressor Stages
Essentially constant radius
Substantial change in radius

6. Turbomachinery - Pumps
Positive Displacement: moving boundary forces fluid along by volume changes.
Reciprocating, rotary: piston, screw, ...
Dynamic: momentum change by means of moving blades or vanes (No closed volume).
Axial, centrifugal, mixed
Fluid increases momentum while moving through open passages and then converts high velocity to pressure rise in diffuser section
In radial machines doughnut-shaped diffuser is called a scroll
Through a casing Not wind mills, water wheels or propellers
Flow conditioning Stators, scrolls

7. Turbomachinery - Pumps
Screw
Centrifugal
Axial

8. Turbomachinery - Turbines
Extracts energy from a fluid with high head [pump run backwards].
Reaction turbine: fluid fills blade passages and pressure drop occurs within the impeller.
Low-head, high-flow devices
V across rotor increases, p decreases
Stators merely alter direction of flow
Impulse turbine: converts high head to high velocity using a nozzle; then strikes blades as they pass by.
The impeller passages are not fluid filled, and the jet flow past the blades is essentially at constant pressure.
Discharge velocity  relative inlet velocity across rotor
no net change in p across rotor
stators shaped to increase V, decrease p

9. Gas Generator Purpose: Supply High-Temperature and High-Pressure Gas
compressor, combustor, turbine

10. Turbojet Purpose: Provide High-Velocity Thrust
inlet, compressor, combustor, turbine, nozzle

11. Turbofan
Purpose: Produce Lower-Velocity Thrust Through the Addition of a Fan
inlet, fan, compressor, combustor, turbine, nozzle
Stations
0=1= Upstream
2 =compressor inlet
2.5=low-to-high comp
3 =combustor inlet
4 =turbine inlet
4.5=high-to-low turb.
5 =nozzle inlet
8 =exit

12. Turboprop
Purpose: Produce Low-Velocity Thrust Through Addition of a Propeller

13. Turboshaft
Purpose: Produce Shaft Power for Rotating Component [Not for Thrust] - helicopter

14. Low BPR
BPR= mass flow through bypass/mass flow through core

15. High BPR

16. Gas Turbine Components
Main Flow-Path Components of a Gas Turbine Engine:
inlet
compressor
combustor
turbine
nozzle
Secondary Flow-Path Components:
disk cavities
cooling flow bleed ducts
bearing compartments

17. Inlet
Inlet Reduces the Entering Air Velocity to a Level Suitable for the Compressor
Often Considered Part of Nacelle
Critical Factors:
Mach Number
Mass Flow
Attached Flow
Subsonic Inlet
Divergent area used
to reduce velocity
Supersonic Inlet
Shocks often used to
achieve reduced velocity
and compression
Nacelle
Engine Inlet

18. Fan/Compressor Axial-Flow Fan Axial-Flow Compressor
Low-Pressure
High-Pressure
Centrifugal Compressor
Mixed Axial/Radial Flow
Fan
Low-Pressure Compressor
High-Pressure Compressor

19. Combustor
Designed to Burn a Mixture of Fuel and Air and Deliver to Turbine
Uniform Exit Temperature
Complete Combustion
Exit Temperature Must Not Exceed Critical Limit Set By Turbine Metal + Cooling Design
Combustor

20. Turbine
Extracts Kinetic Energy form Expanding Gases and Converts to Shaft Horsepower to Drive the Compressor/Fan
Axial Flow Turbine
High Flow Rates
Low-Moderate Pressure Ratios
Centrifugal Turbine
Lower Flow Rates
Higher Pressure Ratio
High-Pressure Turbine
Low-Pressure Turbine

21. Nozzle
Increase the Velocity of the Exhaust Gas Before Discharge from the Nozzle and Straighten Gas Flow From the Turbine
Convergent Nozzle Used When Nozzle Pr < 2 (Subsonic Flow)
Convergent-Divergent Nozzle Used When Nozzle Pr > 2
Often incorporate variable geometry to control throat area
Nozzle

22. 3 Planar Views of
a Turbomachine

23. Cross Flow Area Variation in Compressor & Turbine Rotors
Diffuser
Nozzle
Cross Flow Area

24. Favorable [Turbine] & Unfavorable [Compressor] Pressure Gradients
Bernoulli: dp dV

25. Turbine
Compressor
Thermophysical Process
Across an Adiabatic
Stator

26. Compressibility Can Be A Major Issue in Nozzle Flows
Subsonic
Supersonic nozzle
Subsonic
Subsonic diffuser

27. Gas-Turbine Design Process
Well Developed
Developed - Fairly Mature
Determine “Steady” and Unsteady Coupling Effects Between the Components
Multi-Component 3-D Steady and Unsteady-Flow Analysis
Developed - Improvements Required
Determine Unsteady-Flow Interaction Effects on Performance (e.g.. Wake / Blade, Shock / Blade, Potential, Thermal, and Structural Interactions
Multi-Stage Turbomachinery 3-D Unsteady-Flow Analysis
Under Development
Multi-Stage Turbomachinery and Secondary Flow Path 3-D Steady-Flow Analysis
Determine Primary Blade-Row and Secondary Flow Path Pressure and Mass-Flow Distribution Interaction Effects
3-D Turbomachinery Airfoil and Design and Analysis
Upon Stacking Airfoil Sections from Structural or Aero Considerations, Determine Single Blade-Row Performance (i.e.. Loading and Pt Losses) and Combustor Heat and NOx Release
Analysis Time and Cost
Turbomachinery 2-D Airfoil Section Design and Analysis
From Velocity Triangles, Determine Airfoil Shape as a Function of Radius for Required Flow Turning and Pressure Rise/Drop
Through-Flow or Streamline (2D x,r) Analysis
From Radial Equilibrium or Axisymmetric Streamline Analysis, Determine Spanwise Variation in Velocity Triangles
Turbomachinery Meanline (1D) Analysis
From Required Compressor / Turbine Work Determine Number of Stages and Velocity Triangles of”Mean Radius” Streamline
Engine Cycle Analysis
From Required Thrust, Determine Work Required by Compressor and Turbine and Heat Addition from Combustor
Fidelity / Complexity

28. Units and Key Constants

29. Conventional Units Parameter English Units SI Units
Distance Feet, Inches Meters, M
Time Seconds Seconds, s
Force Pounds (force), lbf Newton, N
Pressure psf, psi Pascal, Pa (1N/1m2)
bar (105Pa)
1 ft H2O kPa
Mass Pounds (mass), lbm kilogram
Energy Btu Joule, J
Power 1 Hp kWatt

30. Equivalent Systems of Units
1 Newton = 1 kg-m/sec2
1 Joule = 1 N-m/sec

31. Important Constants for Air
R=287 J/kg-R = 287 m2/s2-K

32. Useful Equivalents Atmospheric pressure 1 in Hg = 0.49116 psi
2116 psf = 14.7 psi = Bar = 101,325 Pascals

33. For Liquid Water :
U.S. Standard Atmosphere

34. Standard Atmosphere http://www.digitaldutch.com/atmoscalc/index.htm
Altitude
Altitude
Stratosphere
>65,000 ft
36,089 ft
36,089 ft
3.202 psia
psia
59 F
Pressure
Temperature

37. Thermodynamics Review

38. Thermodynamics Review
Thermodynamic views
microscopic: collection of particles in random motion. Equilibrium refers to maximum state of disorder
macroscopic: gas as a continuum. Equilibrium is evidenced by no gradients
0th Law of Thermo [thermodynamic definition of temperature]:
When any two bodies are in thermal equilibrium with a third, they are also in thermal equilibrium with each other.
Correspondingly, when two bodies are in thermal equilibrium with one another they are said to be at the same temperature.

39. Thermodynamics Review
1st Law of Thermo [Conservation of energy]: Total work is same in all adiabatic processes between any two equilibrium states having same kinetic and potential energy.
Introduces idea of stored or internal energy E
dE = dQ - dW
dW = Work done by system [+]=dWout= - pdV
Some books have dE=dQ+dW [where dW is work done ON system]
dQ = Heat added to system [+]=dQin
Heat and work are mutually convertible. Ratio of conversion is called mechanical equivalent of heat J = joule

40. Review of Thermodynamics
Stored energy E components
Internal energy (U), kinetic energy (mV2/2), potential energy, chemical energy
Energy definitions
Introduces e = internal energy = e(T, p)
e = e(T)  de = Cv(T) dT thermally perfect
e = Cv T calorically perfect
2nd law of Thermo
Introduces idea of entropy S
Production of s must be positive
Every natural system, if left undisturbed, will change spontaneously and approach a state of equilibrium or rest. The property associated with the capability of systems for change is called entropy.

41. Review of Thermodynamics
Extensive variables – depend on total mass of the system, e.g. M, E, S, V
Intensive variables – do not depend on total mass of the system, e.g. p, T, s,  (1/v)
Equilibrium (state of maximum disorder) – bodies that are at the same temperature are called in thermal equilibrium.
Reversible – process from one state to another state during which the whole process is in equilibrium
Irreversible – all natural or spontaneous processes are irreversible, e.g. effects of viscosity, conduction, etc.

42. Thermodynamic Properties
Primitive
Derived

43. 1st Law of Thermodynamics
For steady flow, defining:
We can write:
and

44. Equation of State
The relation between the thermodynamic properties of a pure substance is referred to as the equation of state for that substance, i.e F(p, v, T) = 0
Ideal (Perfect) Gas
Intermolecular forces are neglected
The ratio pV/T in limit as p  0 is known as the universal gas constant (R).
p  /T  R = e3
At sufficiently low pressures, for all gases
p/T = R or
Real gas: intermolecular forces are important

45. Real Gas

46. Real Gas

47. 1st & 2nd Law of Thermodynamics
Gibbs Eqn. relates 2nd law properties to 1st law properties:

48. Gibbs Equation Isentropic form of Gibbs equation:
and using specific heat at constant pressure:

49. Thermally & Calorically Perfect Gas
Also, for a thermally perfect gas:
Calorically perfect gas - Constant Cp

50. Isentropic Flow For Isentropic Flow:
Precise gas tables available for design work – Thermally Perfect Gas good for compressors not for turbines because of burned fuel.

51. Gibbs Equation
Rewriting Gibbs Equation:

52. Gibbs Equation
Rewriting Gibbs Equation:

53. Isobars are not parallel

54. Mollier for Static / Total States
Poout
h02
h02i
We will soon see
V2/2
Poin
h01 s