Accession Number:

AD0683127

Title:

DETERMINING THE DIAMETERS OF ENGINE EXHAUST LINES FOR THE CASE OF AN IMPULSE SUPERCHARGER SYSTEM,

Descriptive Note:

Corporate Author:

FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OHIO

Personal Author(s):

Report Date:

1968-08-23

Pagination or Media Count:

12.0

Abstract:

A method is proposed for determining the exhaust pipe diameter which gives minimum gas energy losses in a high-speed two-stroke engine with exhaust turbine. Analysis of experimental data on the operation of these engines shows that the principal losses in the exhaust system are those due to sudden expansion as the gas flows through the valves into the manifold, and those in the exhaust line itself. Other losses due to localized resistances besides those in the valves may be accounted for by including them in the equivalent length of the exhaust line. Heat leakage through the walls of the line is small and may be disregarded. Thus the problem reduces to finding the exhaust pipe diameter which gives minimum hydraulic losses in the exhaust valves and line for given values of cyclic mass flow, tubing length and effective cross sectional area of the exhaust valves. The procedure is based on derivation of an expression for the gas energy lost in terms of the coefficient of localized drag, the drag coefficient with respect to length, the dimensions of the tubing, and the density of gas. This formula is derived by integrating the expression for the element of energy loss with respect to time from the instant when the gas leaves the cylinder to the instant when the gas leaves the exhaust line. Numerical analysis of this expression shows that deviation from optimum toward smaller diameters causes a more rapid increase in losses than when the diameter is increased past optimum. Thus if it becomes necessary for some reason to use tubing which differs from the optimum size, it is better to use a larger size. Author

Subject Categories:

  • Aerodynamics
  • Fluid Mechanics
  • Jet and Gas Turbine Engines

Distribution Statement:

APPROVED FOR PUBLIC RELEASE