External: K.E., gravitational P.E., electrostatic P.E.. • Internal: .... air at 300 K,
speed of sound ~ 350 m/s → 100 m/s ... M. Nakahara and H. Kohama, “Junkers
High Pressure Air Compressor-A Case of Technology Transfer ... pe e ta ppa atus
...
Understanding: U d t di Th The P Path th tto Hi Highh Efficiency Chemical Engines Chris F. F Edwards Kwee Yan Teh, Shannon Miller, Matthew Svrcek, Sankaran Ramakrishnan, and Adam Simpson Advanced Ad dE Energy S Systems t L Laboratory b t Department of Mechanical Engineering Stanford University
40%
34%
>74% of U.S. CO2 is emitted by engines.
Engines • All engines have ha e three essential feat features: res – they produce work (by definition) – they require a resource (1st Law) – they reject energy to surroundings (2nd Law) Energy E Resource
Engine Rejected Energy (surroundings)
Work
Efficiency Limits • Only O l four f ways to t transfer t f energy: – work (entropy free) – heat (energy transfer due to ΔT ) – matter (internal and external) • External: K.E., gravitational P.E., electrostatic P.E. • Internal: thermal, chemical, nuclear
– radiation di ti ((nott considered id d h here))
• It is i the th combination bi ti off energy resource and d surroundings that determines the ultimate efficiency ffi i lilimitation it ti off an engine i ((exergy). )
Classifying y g Engines g by Energy Resource Sun Moon
Space Atmosphere
High K.E.
Surface Anthrosphere Biosphere Water Lithosphere Accumulated Hydrosphere Geothermal
Resources
Radiation Engines (e.g., PV) Kinetic Engines (e.g., Wind) Heat Engines (e.g., Geo) Gravity Engines ((e.g., g , Hydro) y ) Nuclear Engines (e.g., BWR) Chemical Engines (e.g., ICE)
Chemical Exergy gy of Some Fuels Fuel Species+ Methane Methanol Carbon Monoxide Acetylene Ethylene Ethane Ethanol Propylene Propane Butadiene i-Butene i-Butane n-Butane n-Pentane i-Pentane B Benzene n-Heptane i-Octane n-Octane Jet-A y g Hydrogen
Chemical Formula CH4 CH3OH CO C2H2 C2H4 C2H6 C2H5OH C3H6 C3H8 C4H6 C4H8 C4H10 C4H10 C5H12 C5H12 C6H6 C7H16 C8H18 C8H18 C12H23 H2
Chem. Exergy† MJ per fuel k l kmol k kg 832 722 275 1267 1361 1497 1363 2001 2151 2500 2644 2800 2805 3460 3454 3299 4769 5422 5424 7670 236
51.9 22.5 9.8 48.7 48.5 49.8 29.6 47.6 48.8 46.2 47.1 48.2 48.3 48.0 47.9 42.2 42 2 47.6 47.5 47.5 45.8 117.2
ΔH° Reaction* MJ per fuel k l kmol k kg -803 -50.0 -676 -21.1 -283 -10.1 -1257 -48.3 -1323 -47.2 -1429 -47.5 -1278 -27.7 -1926 -45.8 -2043 -46.3 -2410 2410 -44.5 44.5 -2524 -45.0 -2648 -45.6 -2657 -45.7 -3272 -45.3 -3265 -45.2 -3169 3169 -40.6 40 6 -4501 -44.9 -5100 -44.7 -5116 -44.8 -7253 -43.4 -242 -120.0
ΔG° Reaction* MJ per fuel k l kmol k kg -801 -49.9 -691 -21.6 -254 -9.1 -1226 -47.1 -1316 -46.9 -1447 -48.1 -1313 -28.5 -1937 -46.0 -2082 -47.2 -2421 2421 -44.7 44.7 -2560 -45.6 -2712 -46.7 -2717 -46.7 -3353 -46.5 -3347 -46.4 -3190 3190 -40.8 40 8 -4625 -46.2 -5259 -46.0 -5261 -46.1 -7440 -44.5 -225 -111.6
ΔS° Reaction* kJ/K per fuel k l kmol k kg
Exergy to LHV R i Ratio
-5.2 -0.33 50.4 1.57 -98.2 -3.51 -104.6 -4.02 -25.2 -0.90 60.5 2.01 117.7 2.56 36.6 0.87 129.2 2.93 36.9 0.68 120.2 2.14 214.4 3.69 200.0 3.44 271.3 3.76 277.0 3.84 69.4 69 4 0.89 0 89 415.0 4.14 531.4 4.65 487.1 4.26 626.4 3.74 -56.2 -27.88
1.037 1.068 0.971 1.008 1.029 1.048 1.067 1.039 1.053 1.038 1.047 1.058 1.056 1.057 1.058 1.041 1 041 1.060 1.063 1.060 1.057 0.977
+All species taken as ideal gases. †Environment taken as: 25°C, 1 bar, 363 ppm CO2, 2% H2O, 20.48% O2, balance N2 . *Reaction with stoichiometric air at 25°C, 1 bar. All products present as ideal gases, including water.
Fuel Conversion Efficiency potential (maximum first-law efficiency based on LHV) of most fuels is ~100%.
Conversion Efficiency of Engines 100.0
Savery, Newcomen (
