內燃機排氣系統設計改善

Exhaust System Design Improvement of Internal Combustion Engine

林裕豐(Yu-Feng Lin)

指導教授 ： 吳浴沂

國立臺北科技大學/機電學院/車輛工程系所/碩士(2010年)

摘要

本論文在於改善內燃機排氣系統，設計符合各項空間限制、達到觸媒前移、符合觸媒流場均勻度 (uniformity)0.85以上、及維持現有性能要求之新式排氣系統。
論文分為3D設計及模擬分析兩個主要階段：
3D設計階段：依相關限制要求，採用4管合2管再合成1管(4-2-1)構形排氣歧管設計，新觸媒位置較基礎引擎設計前移44.9mm，符合觸媒前移的要求。另運用提昇氣流吹送面積概念，變更採用傳統概念設計之排氣合管段角度，完成第2種新概念排氣歧管設計。
模擬分析階段：
- 計算流體力學：在各缸單獨排氣的穩態條件下進行流場分析，計算觸媒截面上氣流均勻度，作為觸媒使用率指標，計算結果新概念排氣歧管設計較傳統概念設計形式佳，四缸皆符合均勻度0.85要求。
- 性能模擬：模擬結果顯示，使用新概念設計之排氣系統引擎性能模型之最大馬力、扭力性能達到75.98ps@6000rpm及104.08N.m@4500rpm，與基礎引擎性能模型模擬結果，及基礎引擎測試結果，整體性能差異在1.5%以內，符合設定之性能目標。
結果顯示：新概念排氣系統之設計，以4-2-1排氣歧管形式配置，達成觸媒前移44.9mm，達成均勻度指標，並維持現有基礎引擎馬力、扭力性能，達到基礎引擎排氣系統改善之目的。

關鍵字

觸媒 ； 排氣 ； 計算流體力學

並列摘要

This paper is focus on exhaust system performance improvement. To design a new exhaust system which has to keep several design limitation. 1st one is set catalyst position closer to cylinder head. 2nd is satisfy engine room space limitation. 3rd is satisfy catalyst flow uniformity index equal to 0.85 or more. 4th is keeping engine performance compares with base engine.
This paper includes 2 steps, one is 3d model design step and the other is simulation step.
3D design step: Following the exhaust system layout limitation, choosing 4-2-1#1 exhaust concept to design new exhaust system. For new concept exhaust system has been created which has new catalyst position 44.9mm closer to the cylinder head than base engine. And following new flow distribution concept to change exhaust flow angle between end of manifold and catalyst front end to increase distribution area of flow into catalyst.
Simulation step:
- Computational Fluid Dynamics: Each cylinder was simulated in steady state condition to calculate flow uniformity (γ) on section of catalyst. Result of flow uniformity will be a index of catalyst utilization. For the final result of uniformity shows that new concept exhaust system is better the traditional one and satisfies 0.85 requirement。
- Performance simulation: Performance of engine simulation model which using new exhaust system has max. power (75.98ps@6000rpm) and max. torque (104.08N.m@4500rpm). To compare with performance of base engine simulation model and real engine test. It shows that difference of overall performance is in 1.5% which satisfies performance requirement.
Follow each result of 2 steps above; the new concept exhaust manifold can keep performance in position of catalyst 44.9mm closer to cylinder head condition, and satisfies uniformity index which should improve exhaust system performance of base engine.

並列關鍵字

Catalyst ； Exhaust gas ； CFD

參考文獻

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