機車引擎油膜動態之研究

Study of Characteristics of Fuel Film Dynamics for Scooter Engine

柯政廷(Cheng-Ting Ke)

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(2008年)

摘要

本研究配合國內機車產業的需求與發展，針對機車燃油噴射系統所產生的壁濕現象(wall wetting)進行探討。首先使用Matlab/Simulink建立非線性機車引擎模型，再使用系統判別中遞迴最小平方法(Recursive Least Square, RLS)將非線性的油膜動態模型辨識為一階線性模型，接著利用機車引擎模型模擬所辨識出之油膜動態模型，由模擬結果顯示，預估之油膜動態相當準確。再針對不同的引擎操作狀態，如噴射正時、進氣溫度…等進行實驗，定量地求得進氣管壁上之燃油沈積比例(x)及油膜蒸發常數(τ)，藉此求出油膜動態之特性參數。將實驗操作點設定在引擎轉速為3000rpm、節氣門開度為25%的運轉條件下，由實驗結果可發現，當進氣溫度提高，燃油沈積比例(x)及油膜蒸發常數(τ)會隨之降低。而在噴射正時方面，當燃油於汽門開啟時噴射，燃油沈積比例(x)及油膜蒸發常數(τ)亦有降低之趨勢。在不同轉速與負荷的實驗方面，實驗轉速定在2000rpm至7000rpm，以每1000rpm做為一測試條件點，由實驗結果發現，當引擎轉速增加，連帶增加進氣氣流的動能，提高熱傳與質傳的速度，使得燃油不易累積於壁面上，燃油沈積比例(x)及油膜蒸發常數(τ)有降低的現象。

關鍵字

油膜動態 ； 壁濕現象 ； 系統判別

並列摘要

This paper investigated the phenomenon about wall wetting in scooter engine. A nonlinear engine model is established by Matlab/Simulink to simulate the fuel film dynamics. The fuel film dynamics model will be identified as the first order model. The recursive least squared technique is employed to identify the wall-wetting phenomena. The simulation results show that proposed model for fuel film dynamics has good results as predict. In the engine experiment, the author set up different engine operation conditions, for example, various fuel injection timings and intake temperatures. The experimental results show that when the intake temperature increased, the portion of fuel that deposited on the manifold wall (x) and the time constant of the fuel evaporation process (τ) will be decreased. Moreover,x and τ decreased as the fuel injected and the intake valve opened at the same time. As engine speed increases,x and τ will decrease due to an increase in forced heat and mass convection.

並列關鍵字

Fuel Film Dynamics ； Wall Wetting ； System Identification

參考文獻

[2] 環保署空氣品質保護及噪音管制處，「低污染車輛推廣」，http://www.epa.gov.tw/F/

[7] J. B. Heywood, “Internal Combustion Engine Fundamentals,” McGraw-Hill Publishing Company, 1988.

[8] Z. Ye, “A Simple Linear Approach for Transient Fuel Control,” SAE Paper No. 2003-01-0360.

[10] D. Blomqvist, S. Byttner, U. Holmberg, and T. Rögnvaldsson, “Different Strategies for Transient Control of the Air-Fuel Ratio in a SI Engine,” SAE Paper No. 2000-01-2835.

[11] A. D. Gaeta, S. Santini, L. Glielmo, F. D. Cristofaro, C. D. Giuseppe, and A. Caraceni, “An Algorithm for the Calibration of Wall-Wetting Model Parameters,” SAE Paper No. 2003-01-1054.