Abstract
An “absolute enthalpy” is defined which has the advantage that the enthalpies of different systems are similar and compatible quantities regardless of differences in state or chemical composition. An enthalpy-fuel/air ratio diagram for equilibrium state combustion gases is formulated using absolute enthalpies. On this diagram, virtually all processes which involve combustion and combustion product gases—and which are entirely within the scope of the first law of thermodynamics—can be represented by straight lines. Such a diagram therefore provides a very rapid and flexible method of solving many frequently occurring combustion problems. Procedures for handling the following typical problems are developed: Determination of adiabatic flame temperatures, theoretical heat releases, combustion efficiencies (from experimental temperature measurements), and the adiabatic mixing of two streams. Absolute enthalpy and heat-capacity data for (CH2)y-air (in 100 R increments) and (CH3)y-air (in 50 K increments) systems are tabulated for lean and rich composition ranges. Above ~ 3000 R ~ 1400 K the enthalpy and heat-capacity functions are pressure sensitive and the tabulated data are for 1 atm.
