THERMODYNAMICS FUNDAMENTALS REVIEW

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THERMODYNAMICS
FUNDAMENTALS REVIEW JOHN LEWIS
xbee146/TRAINING/FUNDAMENTALS/fundamentals1new.ppt
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WHAT WE WILL D0 - TRANSITION FROM THE
CLASSROOM TO THE REAL WORLD..
REVIEW THE FUNDAMENTAL PHYSICAL
RELATIONSHIPS WE ACTUALLY USE IN GAS TURBINE
PERFORMANCE ENGINEERING
LEARN BY DOING (PROBLEMS) WHY ? PREPARE FOR
COURSE MATERIAL THAT FOLLOWS
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A VISUALIZATION OF FUEL ENERGY





Elevator holds 25 people

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A VISUALIZATION OF FUEL ENERGY
1 lb Jet Fuel 18400 BTU 18400 x
778 14,315,200

(BTU) x (Ft-Lb/BTU) Ft Lb


Elevator holds 25 people

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A VISUALIZATION OF FUEL ENERGY
1 lb Jet Fuel 18400 BTU 18400 x
778 14,315,200

(BTU) x (Ft-Lb/BTU) Ft Lb

1 ave/
person 150 lbs 1 Story 20

Lifting Work 150 x 20 3000
Ft-Lbs
14,315,200 / 3000
4,770 floor-people Elevator holds 25
people 1 lb
fuel can lift 25 people
4770/25 190 floors !!!
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WHAT ARE THE FUNDAMENTAL RELATIONSHIPS ?
(FOR CONTROL VOLUMES) 1. ENERGY CONSERVATION
(1ST LAW) 2. ADIABATIC PROCESS
RELATIONSHIP CONNECTS PRESSURES WITH
TEMPERATURES (COMPRESSORS TURBINES)
3. COMPRESSIBLE FORM OF BERNOULLI ( STATIC VS
TOTAL TEMPERATURES AND PRESSURES) 4. MOMENTUM
BALANCE USING STREAM THRUST
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CONTROL VOLUMES FIXED MASS
FIXED SYSTEM
MOVES IN SPACE MASS
FLOWS THROUGH (LAGRANGIAN)
(EULERIAN)
W

v V p

T

h m,T,h,p
in
out


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FUNDAMENTALS
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FIRST LAW ENERGY BALANCE (ENERGY OUT) - (ENERGY
IN) (HEAT ADDED) - (WORK DONE) Wout x
h,out - Win x h,in Qadded
- PWRshaft
Qadded
Ein Win x h,in
Eout Wout x h,out
(control volume)

PWR,shaft
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RELATIONSHIP CONNECTING PRESSURE AND TEMPERATURE
FOR AN (IDEAL) ADIABATIC PROCESS Compression
(Compressors) and Expansion (Turbines)
Pout/Pin (Tout/Tin)Cp/R Cp
constant pressure specific heat
R gas constant R Cp - Cv
(Note R/Cp (k-1)/k exponent)
(Holds only if Cp is assumed
constant for entire process)
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TOTAL AND STATIC QUANTITIES FOR
PRESSURES AND TEMPERATURES 1. Total
Energy is Fixed htotal
hstatic 1/2 V2 /Jgc h - BTU/lb V- ft/sec
gc 32.2 ft/sec/sec J 778 Ft-Lb/BTU
2. Process is adiabatic (diffusion and/or
expansion) Ptotal /
Pstatic (Ttotal/Tstatic)Cp/R
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MOMENTUM BALANCE CAN BE EXPRESSED USING STREAM
THRUST (Fstream) Fstream (W x V)/gc
Area x ( Pstatic - Pbar)
Funbalanced Fstr, out - Fstr,in
Fstream,in
Fstream,out

Fconstraint Funbalanced
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LETS LEARN BY DOING ..
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SHAFT
OUTSIDEAMBIENT
AMBIENT
INLET COMPRESSOR BURNER
TURBINE NOZZLE DIFFUSER
TURBOJET ENGINE SCHEMATIC
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BASIC GAS TURBINE THERMODYNAMIC
PROCESSES TYPE
WORK IDEAL
1. COMPRESSION IN
ISENTROPIC

(REVERSIBLE
ADIABATIC) 2. EXPANSION (TURBINE) OUT
3. HEAT
ADDITION NONE
COMPLETE (COMBUSTOR)
CONSTANT
PRESSURE 4. DIFFUSION (DIFFUSER) NONE
ISENTROPIC 5. EXPANSION
(NOZZLE) NONE
ISENTROPIC
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GRAPHICAL REPRESENTATION OF BASIC PROCESSES
COMPRESSION
P CONSTANT
ACTUAL
T
IDEAL
EXPANSION
S
ACTUAL
T
IDEAL
S
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(ADIABATIC) EFFICIENCY DEFINITIONS COMPRESSION
COMPRESSOR EFFICIENCY IDEAL D h /
ACTUAL D h EXPANSION TURBINE
EFFICIENCY ACTUAL D h / IDEAL D h

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JET ENGINE THERMODYNAMIC CALCULATIONS-
PROBLEM 1 (SEA LEVEL STATIC) Pressure -



psia
P/P .05
Wa 100 lbs/sec Press Ratio
101
Eff. 85 Shaft pwr -BTU/Sec
Eff. 90
Wf
lbs/sec

2000 F
Temp
(R)


Enthalpy-


BTU/LBm BURNER ENERGY (HV 18400
BTU/Lb)
Cp 0.24 BTU/Lbm-Degree

R 53.3
Ft-Lbf/Lbm-Degree

J 778 Ft-lbf/BTU
THRUST Cp/R


htot - hstatic
V Fstr,out
Fstr,in
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JET ENGINE THERMODYNAMIC CALCULATIONS-
PROBLEM 1 (SEA LEVEL STATIC)


50.62 Pressure - 14.696
146.96
139.61
14.696

psia
P/P .05
Wa 100 lbs/sec Press Ratio
101
Shaft pwr
-BTU/Sec
13,608

Wf 1.8 lbs/sec



Temp (R) 58.67
1085.7
2460 1903 1337

Enthalpy- 124.48
260.56 590.4
456.7 320.8


BTU/LBm THRUST Fnet 5,765 lbs
COMPLETE ENGINE



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JET ENGINE THERMODYNAMIC CALCULATIONS-
PROBLEM 2 (IN FLIGHT-fixed Properties) Pressure
- 3.468


psia

P/P .05 Wa 100 lbs/sec
Press Ratio 201
Eff. 85 Shaft pwr
-BTU/Sec Eff. 90 Vflt 800 ft/sec

Wf
lbs/sec



Temp (R) 394.1

3000

Enthalpy-


BTU/LBm BURNER ENERGY (HV 18400
BTU/Lb)
Cp 0.24 BTU/Lbm-Degree

R
53.3 Ft-Lbf/Lbm-Degree

J 778
Ft-lbf/BTU THRUST
Cp/R

htot -
hstatic V Fstr,out
Fstr,in
Fnet