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# lec9 - Chapter 9 M1A2 Abrams with current and proposed 1500...

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1 Chapter 9 Gas Power Systems M1A2 Abrams, with current and proposed 1500 hp turbine engine. Photos courtesy of United States Military Academy Piston-Cylinder Engines 4 Stroke Engine Process • *Intake Stroke • Compression Stroke • Power Stroke (Expansion) • Exhaust Stroke * For Spark Ignition engines, intake is of an air/fuel mixture. For Diesel engines, intake is air only.

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2 Air Standard Analysis The following assumptions are made: Air, an Ideal Gas, is the working fluid Combustion is replaced with Heat Addition (see Chap 13 for details) No exhaust and intake strokes – constant volume heat rejection All processes are internally reversible For Cold-Air Standard, Specific Heats are also assumed constant
3 Properties for Ideal Gases P vn R T P vR T P Vm R T = = = The Ideal Gas Model: () uu T hh T u T R T = ==+ v p du cT dT dh = = Tables A-22(E) and A-23 (E) When specific heats are assumed constant Table A-20(E): 21 v p uucTT hhcTT =− −= Requirements: 1 c c Z P P TT ± ± R R M = Finding Entropy Data For Ideal Gases: Motivation: Application of the 2 nd Law of Thermodynamics frequently requires finding specific entropy data. For use with Table A-22 v p du C T dh C T P T = = = For an Ideal Gas: Using these relations with the T ds equations yields: ( ) 2 22 11 2 1 1 ,, ( ) ( ) l n P sTP sTP sT sT R P ⎛⎞ ⎜⎟ ⎝⎠ oo

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4 Ideal Gases with Constant Specific Heats () 22 11 , , ln ln p TP sT P sTP C R ⎛⎞ −= ⎜⎟ ⎝⎠ , , ln ln v Tv sT v sTv C R + Use Specific heat data in Tables A-20 and A-21 For example: Air (Ideal Gas), Constant Specific Heats P 1 = 3 MPa, P 2 = 1 MPa T 1 = 500 K, T 1 = 300 K Use Table A-20, at T avg = 400 K; C p = 1.013 kJ/kg K Δ s= -0.202 kJ/kg K Isentropic Processes Showing isentropic processes is rapid on T-s or h-s diagrams. However, tabular data may still be used as well. Isentropic Processes with Ideal Gases 2 1 l n P sT sT R P =+ oo For air (Table A-22) only: r r r r P P P P vv = = Constant Specific Heats: 1 1 1 2 k k k v v ==
5 Air Table (A-22) Table A-22

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6 Otto Cycle 4 Internally Reversible Processes:
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lec9 - Chapter 9 M1A2 Abrams with current and proposed 1500...

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