Further Studies of Unsteady Gas Flow in the Manifolds of Multi-Cylinder Automobile Engines

  • Alan Blair

Student thesis: Doctoral ThesisDoctor of Philosophy


This thesis describes an investigation into the general principles of unsteady flow in pipe systems, with analysis of specific flow regions in the manifolds of a carburetted, four-stroke, automotive engine. The unsteady flow calculation is effected by the method of characteristics under the assumption of one-dimensional, compressible fluid flow. A quasi-steady approach is adopted for the analysis of flow at restrictions and boundaries.

A laser anemometer has been used to measure unsteady velocity in constant and varying area flow, this information together with the pressure-time history then permitting the measured and predicted correlation of the individual Riemann variables. Correlation was generally good although certain discrepancies were evident in the varying area analysis.

With a view to verifying the assumption of quasi-steady conditions, a comprehensive study of the steady flow characteristics of a carburetter and poppet valves was then followed by unsteady flow tests on each component. An adiabatic carburetter model was established which gave good unsteady pressure and flow correlation. Good correlation was also observed using steady flow poppet valve coefficients in unsteady flow.

In a series of firing engine tests, upstream tuning was applied to a BL 2.0 litre, 'O'-series engine, to establish the effect upon engine breathing under different conditions. Predictions from the existing gas dynamics engine model were then correlated with the measured results. The performance trends were well-predicted, but part-throttle correlation
was generally poor.
Date of Award1986
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorGordon Blair (Supervisor)

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