Experimental evaluation of 1-D computer codes for the simulation of unsteady gas flow through engines: A first phase

This paper reports on the first phase of an experimental evaluation of five different methods for the mathematical modeling of unsteady gas flow in engine ducting. The five methods under investigation are the homentropic method of characteristics, the non-homentropic method of characteristics, the two-step Lax-Wendroff method with flux corrected transport, the Harten-Lax-Leer upstream difference method and the Blair method of pressure wave propagation through finite spaces. A single cycle pressure wave generator consisting of a cylinder, connected via a sliding valve to a long duct, has been designed and built. The pressure waves it creates closely mimic those to be found in i.c. engines. A series of tests have been conducted to simulate exhaust and intake flow in a constant area duct sufficiently long, to permit wave observation unclouded by superposition effects and to determine the accuracy of the simulation methods and the cylinder to pipe boundary conditions. A computer simulation of the test apparatus has been written for each of the five theoretical methods using the Queen`s University of Belfast (QUB) non-isentropic treatment of the boundary conditions. The accuracy of each prediction method is then correlated with the experimental results. As might be expected, most of the computer codesmore » produce good correlation for unsteady flow in a constant area duct. 24 refs., 30 figs.« less

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