Purpose

This study aims to contrastively investigate the effects of biodiesel and diesel on the power, economy and combustion characteristics of a compression ignition aviation piston engine for unmanned aerial vehicles.

Design/methodology/approach

Biodiesel used as alternative fuel will not be mixed with diesel during experimental study. Pure diesel fuel is used for the comparative test. Same fuel injection strategies, including pilot and main injection, are guaranteed for two fuels in same test points.

Findings

The engine-rated power of biodiesel is lower than diesel, which results in higher specific fuel combustion (SFC) and effective thermal efficiency (ETE). Biodiesel has the faster burning rate, shorter combustion duration. The crank angle of 50% mass fraction burned (CA50) is earlier than diesel. The ignition delay angle of biodiesel and diesel in the pilot injection stage is almost the same at high engine speed. As the speed and load decrease, the ignition delay angle of biodiesel in the pilot injection stage is smaller than diesel. At 100% high load conditions, the fuel-burning fraction of biodiesel in the pilot injection is the same as diesel. The peak heat release rate (HRR) of biodiesel is slightly lower than diesel. At 20% part load conditions, the fuel-burning fraction of biodiesel in the pilot injection stage is lower than diesel. Because of the combustion participation of unburned pilot injected fuel, the peak HRR of biodiesel in the main injection is equal to or even higher than diesel.

Originality/value

The application feasibility of alternative fuel and its effects on aviation engine power, economy and combustion characteristics will be evaluated according to the “drop-in“ requirements and on the low-cost premise without changing the aviation engine structure and parameters.

中文翻译：

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压燃式航空活塞发动机燃烧生物柴油和柴油的性能与燃烧研究

目的

本研究旨在对比研究生物柴油和柴油对无人飞行器用压缩点火航空活塞发动机的功率、经济性和燃烧特性的影响。

设计/方法/方法

在实验研究期间，用作替代燃料的生物柴油不会与柴油混合。纯柴油用于对比试验。相同的燃料喷射策略，包括预喷射和主喷射，在相同的测试点保证两种燃料。

发现

生物柴油的发​​动机额定功率低于柴油，因此具有更高的比燃料燃烧 (SFC) 和有效热效率 (ETE)。生物柴油燃烧速度更快，燃烧持续时间更短。燃烧质量分数为 50%（CA50）的曲轴转角比柴油早。在发动机高转速下，生物柴油和柴油在引燃阶段的点火延迟角几乎相同。随着转速和负荷的降低，生物柴油在引燃阶段的点火延迟角小于柴油。在 100% 高负荷条件下，预喷射中生物柴油的燃料燃烧分数与柴油相同。生物柴油的峰值热释放率 (HRR) 略低于柴油。在 20% 部分负荷条件下，先导喷射阶段生物柴油的燃料燃烧分数低于柴油。

原创性/价值

替代燃料的应用可行性及其对航空发动机功率、经济性和燃烧特性的影响，将按照“随车随用”的要求，在不改变航空发动机结构和参数的前提下，在低成本的前提下进行评估。