EFFECT OF ENGINE OPERATING CONDITION ON THERMODYNAMIC CYCLE

A sophisticated software is developed for the calculation of thermodyn amic cycle and entropy change in a turbocharged, direct-injection, die sel engine based upon the measured cylinder pressure and shaft encoder output. Assumptions of homogeneous mixture and equilibrium thermodyna mic properties for the products of combustion are made and the tempora l variation in fluid thermodynamic state is effectively progress in a pseudo quasi-steady manner through a series of adjacent equilibrium st ates, each separated by a relatively small but finite interval of one- degree crank angle. The thermodynamic properties are calculated by eit her of two equivalent formulations-equilibrium constants or minimisati on of Gibbs free energy, and are expressed in algebraic equations for the partial derivative of internal energy and gas constant with respec t to temperature, pressure and equivalence ratio. The effect of engine operating conditions on the thermodynamic cycle is studied. Results s how that the dynamic fuel injection timing and hence the ignition dela y are strongly dependent on the operating conditions, which explains t he reason for incorporating a fuel injection control system in modern vehicular engines for the optimisation of engine combustion cylcle.