Secondary air valve for IC engine afterburner - has flap with natural frequency chosen to avoid resonance with exhaust

摘要

A six cylinder internal combustion engine has the exhaust passages (23) from the cylinders (C1-C6) grouped in pairs as the arms of a Y. The exhaust manifold (22) has three branches (22a, 22b, 22c) which connect to the three outlets. Secondary air for after burning the exhaust gases is introduced into the manifold through three flap valves (24, 26, 28). Each valve has a flexible flap covering an opening. The flap is lifted when the pressure in the exhaust is less than atmospheric. Two of the valves (24, 26) open into one branch (22a) of the manifold and the third into another branch. The natural frequency of the flaps is between 190 and 300 Hz. This prevents interference between the natural frequency and exhaust pulsations at high speeds.