 

Authors:  S. J. Kirkpatrick, G. P. Blair, R. Fleck, R. K. McMullan 
Title:  Experimental Evaluation of 1D Computer Codes for the Simulation of Unsteady Gas Flow Through Engines  A First Phase 
Date:  September 1416, 1994 
Published:  SAE OffHighway and Powerplant Congress  Milwaukee, Wisconsin  SAE 941685 
Abstract: 
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 nonhomentropic method of characteristics, the twostep Lax
Wendroff method with flux corrected transport, the HartenLaxLeer 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. The cylinder and the ducts of the device can be filled with any gas and at elevated temperatures.
A perfect seal exists between the cylinder and the valve thus enabling mass flow correlation. The initial
cylinder pressure may be set to simulate an induction or an exhaust process. The duct attached to the
pressure wave generator can simulate virtually any configuration to be found on an i.c. engine. Pressure
and temperature are recorded by transducers positioned at various locations in the apparatus and stored
using a highspeed data acquisition system.
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) nonisentropic 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 codes produce good correlation for unsteady flow in a constant area duct. However, this paper
is the first in a series of papers, which will report the exposition of the various computer codes to
increasingly difficult pipe modeling geometry and thermodynamic discontinuities.
You may obtain a copy of this paper by calling SAE Customer Service at 18776067323 (tollfree in the U.S. and Canada) or 17247764970.

