Pulsating flow phenomena in exhaust manifolds
File(s)
Author(s)
Nikita, Christina
Type
Thesis
Abstract
The objective of this work was to evaluate the accuracy of pressure losses predictions from 1-D gas dynamics models through the experimental study of the pressure wave action, the interference of flow pulses amongst cylinders and the turbulent structures established in the exhaust manifold flow. These phenomena have an effect on the exergy levels available at the end of the manifold and, in the case of turbocharged engines, they reduce the amount of energy in the exhaust gases that can be translated into useful work.
The evaluation of the accuracy of 1-D pressure loss models was done by reference to results from a newly developed experimental apparatus which used pressurised air at ambient temperature. The setup incorporated poppet valves that allowed the generation of pressure pulses to propagate through a model T60o manifold. The downstream end of the manifold was altered between open and 20% and 42% restricted ends; the latter two by the use of orifice plates. Static pressure measurements were obtained across the junction area for open end and restricted manifold end cases, at a range of engine speeds (950-2000rpm) and load points. The parametric studies focused on the investigation of the behaviour of the acoustic waves under a spectrum of different conditions. Velocity measurements using Particle Image Velocimetry (PIV) were also obtained in the junction and outlet duct in the plane of symmetry of the T60o manifold. The velocity measurements were used to evaluate the contribution of the acceleration of the bulk flow, the diffusion losses and the acoustic phenomena to the static pressure losses measured. An analysis of the predictions of two 1D software packages (Gasdyn and GTPower) was also performed by reference to the pressure measurements. Finally, the evaluation was extended by reference to CFD simulations (OpenFOAM) of pulsating flow in T and Y manifolds.
The evaluation of the accuracy of 1-D pressure loss models was done by reference to results from a newly developed experimental apparatus which used pressurised air at ambient temperature. The setup incorporated poppet valves that allowed the generation of pressure pulses to propagate through a model T60o manifold. The downstream end of the manifold was altered between open and 20% and 42% restricted ends; the latter two by the use of orifice plates. Static pressure measurements were obtained across the junction area for open end and restricted manifold end cases, at a range of engine speeds (950-2000rpm) and load points. The parametric studies focused on the investigation of the behaviour of the acoustic waves under a spectrum of different conditions. Velocity measurements using Particle Image Velocimetry (PIV) were also obtained in the junction and outlet duct in the plane of symmetry of the T60o manifold. The velocity measurements were used to evaluate the contribution of the acceleration of the bulk flow, the diffusion losses and the acoustic phenomena to the static pressure losses measured. An analysis of the predictions of two 1D software packages (Gasdyn and GTPower) was also performed by reference to the pressure measurements. Finally, the evaluation was extended by reference to CFD simulations (OpenFOAM) of pulsating flow in T and Y manifolds.
Version
Open Access
Date Issued
2017-01
Date Awarded
2017-08
Advisor
Hardalupas, Yannis
Taylor, Alexander M.K.P.
Sponsor
Volvo Car Corporation, (Sweden)
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)