Study of pulsating flow in close-coupled catalyst manifolds using phase-locked hot-wire anemometry

Abstract

Phase-locked sampling has been applied to hot-wire anemometry in order to investigate the pulsating flow inside two types of automotive exhaust manifolds fitted with a close-coupled catalyst. An isothermal dynamic flow bench has been used to compare the catalyst velocity distribution in steady operation to crank angle resolved velocity distributions measured in pulsating flow. The latter were obtained using phase-locked averaging. A rotating valve and a cylinder head have been used to generate the pulsating flow. Experimental results have proven the addition principle, i.e. the time-averaged velocity distribution in pulsating flow is proportional to a specific linear combination of velocity distributions, resulting from steady flow through each runner.

Experimental study of flow dynamics in close-coupled catalyst manifolds

“…Persoons et al [1] discuss previous research by the present authors, using an isothermal flow rig for generating cold pulsating flow in two types of exhaust manifolds. The present paper discusses results obtained on a charged motored engine (CME) flow rig that generates cold pulsating flow, which enables the use of hot-wire anemometry (HWA).…”

“…The main contribution of Persoons et al [1] is the experimental validation of the addition principle. Persoons et al [2] extends these findings using the CME flow rig.…”

“…Engine (valve timing) 1.2l I-4, DOHC 16 valves (+17 | +250 | -220 | +13) 1 Runners  28 mm, lengths: (#1) 160 mm, (#2) 80 mm, (#3) 160 mm, (#4) 80 mm…”

“…The cold pulsating flow generated by the CME flow rig in the exhaust system is quite different from the isothermal flow rig [1]. By controlling the intake system pressure, the residual cylinder pressure at exhaust valve opening can be adjusted.…”

Effect of engine exhaust gas modulation on the cold start emissions

“…These techniques may be classified as passive and active depending on the need of additional energy sources. Passive techniques are focused on achieving fast light-off by optimization of the exhaust system design that includes the modification of catalytic converter design to improve heat transfer and/or change in the converter position relative to the engine, and the use of close-coupled catalyst (Lee et al, 2002;Persoons et al, 2004) and hydrocarbon traps (Noda et al, 1997;Yamamoto et al, 2002). These methods generally have less fuel penalty.…”