5 th meeting of GRB Informal Group ASEP

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5 th meeting of GRB Informal Group ‘ASEP’ Potentials of exhaust systems with valves

5 th meeting of GRB Informal Group ‘ASEP’ Potentials of exhaust systems with valves Filip Dörge Page 1

Valves in exhaust systems : general overview of possible acoustical efficiency improvements Engine noise

Valves in exhaust systems : general overview of possible acoustical efficiency improvements Engine noise Passive exhaust systems Exhaust systems with a valve Back pressure Flow noise Page 2

Example of a silencer equiped with an auto-actuated valve u. Valve closed at low

Example of a silencer equiped with an auto-actuated valve u. Valve closed at low exhaust gas volume flow uvalve opens automatically at high exhaust gas volume flow Page 3

Example 1: FLOW NOISE REDUCTION (engine noise and backpressure unchanged) Passive exhaust system SPL

Example 1: FLOW NOISE REDUCTION (engine noise and backpressure unchanged) Passive exhaust system SPL [d. B(A) at 50 cm] Exhaust system with a valve Valve opens here 6 d. B Engine speed [rpm] Page 4

Example 2: ENGINE NOISE REDUCTION (flow noise and backpressure unchanged) Passive exhaust system SPL

Example 2: ENGINE NOISE REDUCTION (flow noise and backpressure unchanged) Passive exhaust system SPL [d. B(A) at 50 cm] Exhaust system with a valve Valve opens here Engine speed [rpm] Page 5

Example of an exhaust system equipped with an auto-actuated valve and with BY-PASS OF

Example of an exhaust system equipped with an auto-actuated valve and with BY-PASS OF THE REAR SILENCER Front silencer Catalytic converters Rear silencer Valve by-passing the rear silencer at high rpm’s Page 6

View on the measured prototype exhaust system Catalytic converters Front silencer Rear silencer Valve

View on the measured prototype exhaust system Catalytic converters Front silencer Rear silencer Valve by-passing the rear silencer at high rpm’s Page 7

Test results Switch point by pass closed by pass open Page 8

Test results Switch point by pass closed by pass open Page 8

Test results u Campbell diagram: colours indicate sound level Engine speed [rpm] by pass

Test results u Campbell diagram: colours indicate sound level Engine speed [rpm] by pass closed by pass open 6000 d. B(A) 70 1000 20 20 0 frequency [Hz] 5000 Page 9 0 5000 frequency [Hz]

THANK YOU ! Page 10

THANK YOU ! Page 10