Numerical model of the aspiration system of an internal combustion engine

Abstract

A physicomathematical model of flow in the aspiration system of an internal combustion engine operating in a "cold" regime, i.e., for a prescribed motion of the crankshaft, has been constructed. An ideal single-species gas is used. Results of a series of calculations for a time interval of five operation cycles are presented.1. A gas-dynamic model and a calculation algorithm for the aspiration system of a four-cycle piston internal combustion engine is proposed. The aspiration system (Fig. 1) is a combination of four channels 3 that go out from a volumetric unit 2 and shut-off valves 4 that control gas overflow to cylinders 5. A throttle valve 1 ensures contact between the volumetric unit and the power source.The gas motion in the system is calculated using the one-dimensional channel flow equations with friction and heat exchange on the walls, and the laws of mass and energy conservation in the volumetric unit. The pressure and temperature of the gas in the cylinders and at the entrance to the system are assumed to be known. This problem was previously considered with some simplifications [1][2][3][4][5]. The formulation and the methods of solution of similar problems were studied [6][7][8][9].2. A system of equations that describe a one-dimensional unsteady flow of a perfect gas in a channel with friction and heat exchange on the walls is transformed to the form ; az x is the coordinate along the channel axis; F and II are the area and the perimeter of the channel cross section; U, P, T, and p are the velocity, pressure, temperature, and density of the gas; q0 is the heat flux through the side surface of the channel; ~ is the skin friction coefficient; 7 = Cp/Cv, Cp = 7R/(7 -1), Cv = R/(7 -1),

Effect of the interface on the local structure of Ge–Si nanostructures

“…The lattice mismatch between the Si substrate and the overgrown Ge layer allows the formation of selfassembled quantum dots ͑QDs͒ through the Stranski-Krastanov mechanism. 12,13 Shown in the same figure also is a spectrum from a bare Si wafer ͑curve 7͒. In this case the nanostructures are usually formed by annealing of the starting material which can be prepared by cosputtering, ion implantation, etc.…”