| 摘要: | 由於國內汽油市場競爭之因素，目前已有多家石油公司之汽油產品在市面上流通，言午多油商也以混合的方式銷售燃油。然而，此類混合燃料對於空氣污染之整體影響並未明確，也未被詳細的探究。機車是台灣地區空氣污染的主要來源之一，也是環境中多環芳香烴化合物（PAHs）的貢獻源，但目前相關PAHs研究皆著重於環境含量之調查，而鮮有污染源之分析。本研究即探討機車使用混合燃料所排放多環芳香烴化合物之排放特徵為何？本研究將一四行程機車架設於底盤動力計上，以C公司及T公司市售之九二無鉛汽油及九五無鉛汽油作為基本燃料，將相同辛烷值之油品分別以不同體積比例掺配成混合燃料F1~F6，作為本實驗使用之燃料，續以電腦模擬實際單人行車時之負荷參數控制底盤動力計，探討引擎在怠速惰轉（Idling）、30 km/hr及50 km/hr運轉速度下，混合燃料對其排氣中21種PAHs排放特徵之影響。
研究的結果歸納如下：1. 六種混合燃料在引擎三種不同行駛速度條件下，排氣中PAHs的平均濃度皆隨著油品摻配比例中C公司油品含量增加時增加，並且隨著引擎行駛速度的升高，其PAHs排放濃度也愈高。2. 比較六種混合油品單位行駛距離之PAHs排放係數（μg/km）、單位耗油量之總PAHs平均排放係數（μg/ L-fuel）以及排氣中PAHs排放率（μg/min）三種排放因子，發現使用九五無鉛或九二無鉛混合汽油均隨油品摻配比例中C公司油品含量的增加而增加，並且隨著引擎的行駛速度上升而增加。3. 就排氣中PAHs之輸出/輸入質量比值(O/I Ratio)作比較，九五無鉛混合汽油F1~F3總PAHs之O/I平均值分別為0.05、0.06及0.07；九二無鉛混合汽油F4~F6總PAHs之O/I平均值則分別為0.02、0.03以及0.04，大多數PAHs呈現為削減的態勢。4. 以複合模式推估九五無鉛混合汽油的VOCs + NOx排放係數以F3為最高（1513 mg/km），其次為F2，最小為F1（1464 mg/km）；F1、F2及F3之Toxic排放係數分別為36.5 mg/km、36.4 mg/km和36.6 mg/km。九二無鉛混合汽油的VOCs + NOx排放係數以F6為最高（1510 mg/km），其次為F5（1506 mg/km），最小則為F4（1504 mg/km）；Toxic排放係數則以F4為最高（39.5 mg/km），F5居次，最小為F6（37.4 mg/km），九二無鉛混合燃料推估的VOCs + NOx及Toxic排放係數皆較九五無鉛混合燃料為高。5. 將複合模式推估所得出九五及九二無鉛混合汽油排放係數與實驗分析所得總PAHs之平均排放濃度（g/Nm3）、平均BaPeq毒性當量濃（g-BaPeq/Nm3）、平均排放係數（g/L-fuel、g/km）及平均排放率（g/min）作一比較，研究顯示兩者呈反向的趨勢，推測可能係因模式中用於推導之空氣污染物種與本研究中所探討的21種PAHs並不相同，故呈現此不同的趨勢。
Due to competition of Taiwan’s domestic gasoline market, there are different types of gasoline produced by various oil companies and sold in the market at present. It is also a common practice to mix different fuels for selling in some of the gas stations. However, the impact of this practice on air pollution has not been fully explored. Motorcycles are one of the contributors for air pollution in Taiwan, as well as for polycyclic aromatic hydrocarbons (PAHs) released into the environment. Most of the studies on PAHs have been concentrated in the environmental contamination, only very few are to study pollution sources. The main purpose of this thesis research was to investigate the emission pattern of PAHs from motorcycles using mixed fuels. To study the impact of these products, we set up a 4-stroke motorbike on a dynamometer and used mixtures of 92 lead-free gasoline (92-LFG) and 95 lead-free gasoline (95-LFG) sold by company C and T, respectively, as the test fuels. We mixed the gasolines with the same octane value but different volume ratios to prepare test fuels designated as F1~F6. A computer model was used to simulate the load parameter in a real single biking for control of the dynamometer. The experimental design is to investigate the emission patterns of 21 PAHs in engine exhaust using various combinations of different fuels under three different running conditions, namely idling, 30 km/hr and 50 km/hr.
The results of this study are summarized as followed：
1. In the condition of three different kinds of running speed, the average concentration of PAHs in the emission of the six mixed fuels increased when the quantity of company C’s gasoline increased in the mixture. Moreover, by the rising of the engine running speed, the concentration of PAHs emission also elevated.
2. By comparing three emission factors, PAHs emission modulus in the unit running distance, average emission modulus of general PAHs of unit oil consuming quantity, and the PAHs emission rate in the emission, of the six mixed gasoline, we discovered that by using 95 lead-free or 92 lead-free mixed gasoline, those factors increased when the quantity of company C’s gasoline increased in the mixture. Moreover, they also increased with the rising of the engine running speed.
3. The O/I average values of general PAHs for 95 lead-free mixed gasoline, F1~F3, are 0.05, 0.06 and 0.07, respectively. The O/I average values of general PAHs for 92 lead-free mixed gasoline, F4~F6, are 0.02, 0.03 and 0.04, respectively.
4. For VOCs + NOx emission estimation using the complex model based on PAHs emission, F3 has the highest emission (1513 mg/km), followed by F2 and F1 (1464 mg/km). The estimated toxic emission factors of F1, F2 and F3 are 36.5, 36.4 and 36.6 mg/km, respectively. Within the three 92 lead-free mixed fuels, F6 has the highest estimated VOCs + NOx emission (1510 mg/km), which was followed by F5 (1506 mg/km) and F4 (1504 mg/km); however, the latest has the highest toxic emission factor (39.5 mg/km). The above estimated VOCs + NOx emission and toxic emission factors of the 92 lead-free mixed fuels are generally higher than the 95 ones.
5. By using the compound mode, we found that the average emission concentrations of general PAHs, the average poison equivalent concentrations of BaPeq, the average emission modulus, and the average emission rates of 95 lead-free and 92 lead-free mixed gasolines showed an opposite trend, which may be due to the difference between the air pollutants used in the mode and the twenty-one PAHs discussed in this research. |
