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Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988.Physics of Nuclear Kinetics. Addison-Wesley Pub. Nuclear and Particle Physics. Clarendon Press 1 edition, 1991, ISBN: 978-0198520467 Nuclear Reactor Engineering: Reactor Systems Engineering, Springer 4th edition, 1994, ISBN: 978-0412985317 Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0- 471-39127-1. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 8-1. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983). This relationship is shown in the figure for κ = 1.4, representing ambient air. Lowering the exhaust temperature causes the lowering of the energy rejected to the atmosphere. This creates more mechanical power output and lowers the exhaust temperature. A higher compression ratio permit the same combustion temperature to be reached with less fuel, while giving a longer expansion cycle. It is very useful conclusion, because it is desirable to achieve a high compression ratio to extract more mechanical energy from a given mass of air-fuel mixture. Thermal efficiency for Otto cycle – κ = 1.4 When we rewrite the expression for thermal efficiency using the compression ratio, we conclude the air-standard Otto cycle thermal efficiency is a function of compression ratio and κ = c p /c v. In this equation, the ratio V 1/V 2 is known as the compression ratio, CR. We can simplify the above expression using the fact that the processes 1 → 2 and from 3 → 4 are adiabatic and for an adiabatic process the following p,V,T formula is valid: Substituting these expressions for the heat added and rejected in the expression for thermal efficiency yields: Therefore the heat added and rejected are given by: Since during an isochoric process there is no work done by or on the system, the first law of thermodynamics dictates ∆U = ∆Q. The heat absorbed occurs during combustion of fuel-air mixture, when the spark occurs, roughly at constant volume. Therefore we can rewrite the formula for thermal efficiency as:
COMPRESSION RATIO PLUS
Since energy is conserved according to the first law of thermodynamics and energy cannot be be converted to work completely, the heat input, Q H, must equal the work done, W, plus the heat that must be dissipated as waste heat Q C into the environment. The thermal efficiency, η th, represents the fraction of heat, Q H, that is converted to work. In general the thermal efficiency, η th, of any heat engine is defined as the ratio of the work it does, W, to the heat input at the high temperature, Q H.