Abstract The investigation on the influence of swirl induced piston on the diesel engine characteristics powered using papaya biodiesel blends was studied. Papaya oil biodiesel, extracted from papaya seed, was blended by volume ratio of 25:75, 50:50, 75:25, and 100:0 with diesel and tested in a diesel engine. The fuel properties of the biodiesel blends were tested and a detailed fuel characterization was performed to analyze their feasibility as a partial substitute fuel. The experimental research study using a standard piston revealed that the B25 blend (25% papaya seed biodiesel, 75% diesel) shows Brake Thermal Efficiency (BTE) close to that of sole diesel. In order to improve the engine performance and pollutant emission for the B25 blend, a slight modification on the piston bowl geometry was introduced. Based on this, six helical holes with diameters Φ2, Φ2.5, Φ3, and Φ3.5 were drilled on four different piston crown surfaces to enhance the swirl ratio and turbulence. A numerical investigation was performed initially with modified piston geometries to understand the fundamental effects of swirl air motion due to piston modification. The numerical investigation results show that Φ2.5 mm hole size piston produces better swirl motion with increased uniform swirl velocity. The turbulent kinetic energy for the modified piston was higher compared to convention piston due to swirl enhancement. With this justification, investigation of the B25 blend was performed experimentally with three different pistons having six helical holes of size Φ2, Φ2.5, and Φ3 mm respectively. The experimental results showed improved engine characteristics for Φ2.5 mm hole piston due to swirl enhancement as indicated in the numerical study. The BTE with Φ2.5 mm hole piston for the B25 blend was 5.6% higher when compared to the conventional piston for diesel fuel. On the other hand, exhaust emissions such as HC, CO & Smoke are decreased with Φ2.5 mm hole piston for B25 blend by 17.9%, 30.5%, and 11.6% when compared to the conventional piston for diesel fuel.

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涡流诱导活塞对生物柴油柴油机发动机特性的研究

摘要 研究了涡流诱导活塞对木瓜生物柴油混合动力柴油机特性的影响。从木瓜种子中提取的木瓜油生物柴油与柴油按25:75、50:50、75:25和100:0的体积比混合，并在柴油机上进行测试。测试了生物柴油混合物的燃料特性，并进行了详细的燃料表征，以分析其作为部分替代燃料的可行性。使用标准活塞的实验研究表明，B25 混合物（25% 木瓜种子生物柴油，75% 柴油）的制动热效率 (BTE) 接近单一柴油。为了改善 B25 混合物的发动机性能和污染物排放，对活塞碗几何形状进行了轻微修改。基于此，在四个不同的活塞顶面上钻了六个直径为 Φ2、Φ2.5、Φ3 和 Φ3.5 的螺旋孔，以提高涡流比和湍流。最初使用修改后的活塞几何形状进行了数值研究，以了解由于活塞修改引起的涡流空气运动的基本影响。数值研究结果表明，Φ2.5 mm 孔径的活塞随着均匀涡流速度的增加产生更好的涡流运动。由于涡流增强，改进活塞的湍流动能高于传统活塞。有了这个理由，对 B25 混合物进行了实验研究，使用三个不同的活塞，分别具有六个尺寸为 Φ2、Φ2.5 和 Φ3 毫米的螺旋孔。实验结果表明，Φ2 发动机特性得到改善。5 毫米孔活塞由于涡流增强，如数值研究所示。与用于柴油燃料的传统活塞相比，用于 B25 混合物的 Φ2.5 毫米孔活塞的 BTE 高 5.6%。另一方面，与用于柴油燃料的传统活塞相比，用于 B25 混合物的 Φ2.5 毫米孔活塞使 HC、CO 和烟雾等废气排放减少了 17.9%、30.5% 和 11.6%。