Measurement of Unsteady Flow in an Exhaust Manifold

Requirements of friendly environmental car have increased in recent years. The advancement of fuel efficiency, the clean exhaust gas, and so on by improvement of the exhaust systems are requested in the automobile industry. The flow structure inside the exhaust manifold affects the performance of the exhaust systems. The present study is carried out to understand the characteristics of the unsteady flow in an exhaust manifold under a room temperature condition. The flow is measured by a hot-wire anemometry and some laser techniques. It is confirmed that the flow direction in the exhaust manifold changed between -40deg. to 10deg. of the BTDC, because the pressure inside the cylinder at the BTDC becomes negative under the motoring engine condition.環境対応車の需要が急激に高まる中、排気系による燃費向上や排ガス浄化などの技術向上が期待されている。今回それらの性能に大きく関わるエキゾーストマニホールド内の流れを理解するため、常温非定常流を発生させ熱線風速計及びレーザー計測を行い流れの特性を明らかにする。本実験により、排気集合部の流れが計測できた。