Effect of Replacement of Butterfly Throttle Body by Barrel Throttle Body on Mass Flow Rate Using CFD.

Paper #:
  • 2017-01-1078

  • 2017-03-28
The purpose of this research is to compare between the butterfly throttle body and a new design of a barrel shape throttle body regarding the mass flow rate of the air sucked by the engine. A throttle body is a main component of the intake system of a vehicle consisting of controlling the volume of air entering the combustion chamber at different RPM. It has a considerable effect on the engine Power and performance especially at high RPM. The butterfly type is more common in commercial vehicles as the maximum rpm reached is 8000-10,000 rpm and due to the simplicity of modelling and manufacturing experience. To overcome these controls with a new design, Simulation using FLUENT ANSYS is held on different opening angles of the 2 throttles and comparison is discussed. A main problem existing in the butterfly throttle body that affects the engine power and increases the pumping losses at high RPM is the restriction from the throttle plate at wide open throttle (WOT). The main benefit of a barrel throttle body is the elimination of this restriction. The design first aimed to maintain linearity between the rotation of the moving rotor with the mass flow rate sucked in the engine, this is achieved by analyzing many profiles and choosing the correct one. A square opening model was best fit to ensure linearity as the projected area may be approximated to be a function of the mass flow rate. A mathematical model is developed to compare with the butterfly model. A turbulent incompressible flow is assumed during static simulation with standard K-epsilon model. A step of 10˚ opening area is taken between a trial and another for each throttle body to draw a (throttle opening-mass flow rate) curve that indicates the improvement done on the barrel one. The curve first shows a better pumping effect for the butterfly type until 25˚ throttle opening. This range is already adjusted for idle position. The curve then indicates identical values with slight increase for the barrel type until 70˚ throttle opening . An enormous increase is then observed in mass flow rate with the barrel type .this indicates a reduced pumping losses during throttling. An increase of 34 % in mass flow rate at Wide open throttle at static modelling is a good indication for better engine performance. Two Validations are required for that model. The first one is done without an engine. A constant mass flow rate is applied at different angles for the two types and the pressure drop is observed. This will allow to validate the simulation results for a throttle working individually. The second validation is more effective as it will indicate the power increase on a working engine (Honda CBR 600 RR). An easy manufacturing technique is used for the barrel type. this will allow for a realistic application of the new design.
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