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

A throttle valve is one of the main components of the intake system of a vehicle and is used to control the air flow rate into the combustion chamber at different engine speeds. Consequently, it has considerable effect on the engine power and performance especially at high engine speeds. The butterfly throttle valve is more common in commercial vehicles due to its simplicity. However, the butterfly throttle plate may affect the engine performance by incurring some pumping losses at high engine speeds even with the plate at wide open throttle (WOT) position. Hence it is proposed in this research work to replace and compare the performance of a spark ignition engine butterfly throttle valve to a newly designed barrel-shaped one with regards to the induced air mass flow rate. The main benefit of the proposed barrel-shaped throttle valve is the elimination of the flow restriction at WOT and high engine speeds. An additional design goal is to maintain linearity between the rotation of the valve core and the mass flow for any given pressure drop. A number of core profiles are considered and ultimately a valve with a square core is chosen since it exhibited a nearly linear relationship between the projected area and the mass flow rate. To assess the valve performance a steady state computational model of both valve designs is developed using ANSYS-FLUENT and the flow is investigated at different openings. The model predictions showed a smaller pumping loss associated with the butterfly valve until 30˚ throttle opening. Between 30˚and 70˚ throttle openings, both designs have shown similar performance. However, beyond 70˚ throttle opening, a significant performance enhancement is observed with the proposed barrel type. Specifically, an increase of 34% in mass flow rate at WOT is observed as an indication of better engine performance with the proposed throttle valve design. This is particularly important for racing vehicles.