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

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 were used to generate the pulsating flow. Experimental results proved 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.