Buffer Tube of Silicone Rubber Film for Damping the Pulsating Flow in Exhaust or Induction Systems of Reciprocating Engines

Regarding measurement of the flow rate of exhaust gas or intake air of engines with several instruments, the pulsating flow in systems causes the error in indicated flow values. Usually a buffer tank is employed for decreasing the pulse. However the tank is rather inconvenient. The authors have developed the named “Surge Tube”, which is composed of a thin silicone rubber film tube having a considerable thermal and mechanical durability. In the conditions near atmospheric pressure, the effective volume as a buffer tank is over 100 times the free real tube volume, without any change in dead volume. The static relations between the inner volume change and the pressure are the most important characteristics, depending on the diameter, thickness, volume, and hardness of the silicone rubber film. The dynamic characteristics of the Surge Tubes are shown as the static pressure configurations at the inlet and outlet of the Surge Tube. Though the mean pressure has a serious influence, the damping effects of the Surge Tube of about 2 L are exceeding those of a conventional surge tank of 200 L. For an induction system with a laminar flow meter in a single cylinder diesel engine, the damping effects are compared with a conventional surge tank. The Surge Tube could reduce the pulsations at the allowable level for a flow meter, in the exhaust system of a diesel engine with one cylinder stroke volume 1 L. In a conventional 2 L 4-cylinder gasoline engine, the Surge Tube can reduce the amplitude of exhaust pulsation to less than 1/20. Though the mean pressure is restricted near the atmospheric pressure and the capacity has a limit, the Surge Tubes can be applied very conveniently for gasoline engines as well as diesel engines to decrease the pulsation.