缸內直噴(GDI)引擎是一項節能且低汙染之技術，比起傳統岐管噴射(PFI)引擎可更精準地控制油氣混和比；而缸內直噴噴嘴之設計對於GDI引擎之性能有重要的影響，其噴嘴需提供穩定之供油量以及具有高重複性之噴霧幾何，才能使引擎正常運作。本研究針對電磁力驅動之渦旋式GDI噴嘴進行設計，已完成電磁線圈與渦旋產生器之基本設計，亦進行改變噴嘴之噴孔尺寸進行實驗觀察：包括流率量測、噴霧發展過程、霧化角分析、噴嘴延遲分析以及粒徑量測。實驗結果顯示，在相同噴注時間(5ms)及噴注壓力(103.4bar)下，當噴嘴孔徑由0.55mm (L/D=0.5)增大為0.7mm (L/D=0.5)時，燃料流量增加約56%，霧化角增加10度；當0.7mm孔徑噴嘴之L/D由1.0縮小至0.5時，流量增加約11.6%，霧化角增加約3度，但噴霧不穩定性亦提高；故若要獲得較大的噴霧霧化角，可將孔徑擴大，但為了避免噴霧之不穩定，可將L/D進行適當之調整。本實驗研究亦顯示，噴霧粒徑會隨噴油壓力上升而下降；在孔徑為0.55mm (L/D=0.5)之條件，其噴霧粒徑體積累積百分比的趨勢與使用商用噴嘴之結果相近，已部分滿足缸內直噴噴嘴設計之霧化需求。本論文之結果顯示孔徑對於缸內直噴之渦漩式噴嘴的噴霧霧化有重要的影響，應為噴嘴設計之重要參數。

Gasoline direct injection (GDI) engine design is a low emission and energy saving technology. Comparing to the traditional port fuel injection (PFI), GDI can have more precise control of air fuel ratio, thus to reduce the hydrocarbon emission from engine. The design of the fuel injector of GDI engine is vital. The injector is required to provide a stable fuel supply and to have high repeatability of the injecting spray geometry in order to make the engine work properly. This research focuses on the design of a swirling-type solenoid valve for the use of GDI engine. The laboratory has completed the fundamental coil and the swirl generator designs of a fast-response fuel injector. This thesis study has performed the experimental observations to characterize the spray from the self-designed fuel injector with different orifice sizes and L/Ds (orifice length to diameter ratio) at various fuel injection duration time and injection pressures. The responding flow rate, spray angle, droplet size, injection delay as well as the detailed spray developing process at different conditions have been analyzed. The results show that the amount of fuel flow increases by 56% when the orifice of the fuel nozzle changes from 0.55mm (L / D = 0.5) to 0.7mm (L / D = 0.5) in the 5ms injection duration at the injection pressure of 103.4bar, while the spray angle increases about 10 degrees. When the L / D of the 0.7mm orifice reduces from 1 to 0.5 at the same injection duration and injection pressure, the amount of fuel flow increases about 11.6%, while the spray angle increases 3 degrees, however, the spray shows less stable as the L/D decreases. The results also show the droplet sizes decreases as the injection pressure rises. Foe the self-designed injector with orifice diameter of 0.55mm (L / D = 0.5), the cumulative percentage of spray droplet volume distribution shows comparative trends to that from commercial GDI injector. This research revealed that the choice of the orifice size of a swirling-type GDI injector strongly affects the atomization of the swirling liquid jet and is a crucial parameter in design.

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