Abstract
Keywords
Intake manifold, polymer, power, torque, noise
Abstract
In this study, a prototype polymeric air intake manifold (PAIM) was designed and fabricated to investigate the potential benefits with respect to power, torque as well noise and vibration characteristics, by comparing it with the existing metallic counterpart (of steel and aluminium). The air intake manifolds have been design designed for a 2.0-litre, 4-cylinder prototype engine.
The PAIM investigated in this study has exhibited higher maximum power (of 144.9 kW) compared to the metal air intake manifold (MAIM) (which recorded 142.5 kW), hence showing an enhancement of 2.4 kW (3.2 Ps). Both manifolds achieved maximum power at the same engine speed of 7 000 rpm. The better performance recorded by the PAIM is in general attributed to the increased design and manufacture flexibility afforded by polymers.
In terms of vibration and noise emission, at relatively low engine speeds, the PAIM has also shown to be superior compared to the MAIM over the full range of frequencies considered in this study. This trend however appeared to diminish with engine speed (and larger throttle opening positions), possibly due to the presence of other sources of noise from the engine that have become more dominant at these more extreme testing conditions, thus masking sounds coming specifically from the manifolds. Further, when the throttle opening was reduced to 20%, the PAIM was only superior at frequencies up to approximately 1 000 Hz, after which the trend reversed. This observation may have been attributed to the natural frequency of the PAIM itself, being in resonance with the vibration of the engine at this specific test point. Another possible reason could be related to the calibrated map itself such as ignition angle, injection duration or the variable valve timing, which had deviated but was not detected. The map used for this testing was initially calibrated for the MAIM to achieve peak performance and was not tuned to the PAIM. Further work is required to fully understanding the reason for this, and to ascertain if this is a genuine phenomenon.
The PAIM only appeared to be inferior to the MAIM in terms of the maximum torque (viz. 205.8 Nm versus 212.3 Nm, the difference being 6.5 Nm), and achieving it at a higher engine speed (of 6 500 rpm versus 6 000 rpm) compared to the MAIM.