analysis of water injection into high-temperature mixture of ...

7and water injection duration angle θ W. It was defined by dividing the total water-fuelratio injection respect to water injection duration angle, equation can be written as,• ⎛ ⎞⎛ − ⎞X ⎟⎜θ θWsw ,m = ⎟W⎝⎜dt ⎟⎜⎜⎟MW⎠⎝ θ ⎠wWEq.2-3Where θs,Wis start angle for mass of water injected and MWWis molecular weight ofwater. Eq.2-2 shown that the thermodynamic properties change with respect to thecrank angle, but at the same time the properties are also functions of temperature andpressure. The following equations and thermodynamic properties will be shown inChapter 3.A study of gas cycles as models of internal combustion engines is useful forqualitatively illustrating some of the important parameters influencing engineperformance, that is, the engine’s efficiency and work output. In theoretical fuel-aircycles work and efficiency can be calculated by meaning of the indicated valueswhich the following definitions are done by the gas. That is the indicated work andthe indicated efficiency.The indicated mean effective pressure (IMEP) is the net work per unitdisplacement volume done by the gas during compression through expansion stroke.The pressure in the cylinder initially increases during the expansion stroke due to theheat addition from the fuel, and then decreases due to the volume increase. It can beobtained to find through integration over a working cycle for the indicated work percycle [7]. Equation can be written as,WCV( IMEP)∫ PdV VdEq.2-4= =W CVWhere is the work done by gas over a working system that the method toanalysis is using the area within the cycle of pressure-volume diagram, V disdisplacement volume. So, the indicated mean effective pressure according to any ofthe gas cycle models is,W CVIMEP = Eq.2-5π2 / 4 stroke( b )The appropriate definition of thermal efficiency for any cycles is clear. Whena fuel is burned rather than heat being transferred to produce work, it is usuallyassumed that the efficiency is the ratio of the net work done per unit mass of fuelinjected to the heat of combustion. According to the principles of thermodynamics,this definition is not necessarily correct if prefers that [6],WCVη = Eq.2-6WCV,maximum possible