Spontaneous ignition of isolated n-heptane droplets with initial diameters of 20–100 $\mu \text{m}$ is simulated using air at 4 atm and 700–1200 K, which includes the typical operating conditions of recuperated microturbines. Because some fuel droplets in a combustor may be sprayed or carried to near the recirculation zone, the simulations use a mixture of pure air and hot combustion products as the oxidiser. The flame structures, evaporation times, and autoignition times in both physical and mixture fraction spaces for the different conditions are presented and compared. The variables examined include the air preheat temperature, amount of dilution with hot products, initial fuel droplet diameter, oxidiser temperature, and oxygen concentration. The results show that droplets in pure air at microturbine conditions fully evaporate before ignition, suggesting that a prevaporised concept is suitable for microturbines. The dilution with hot combustion products decreases the ignition delay time mainly by raising the oxidiser temperature. Low-temperature chemistry does not have a significant effect on droplet ignition because adding even a small amount of hot combustion products can increase the oxidiser temperature to higher than the temperatures favourable for low-temperature kinetics. The cool flame is only observed for 100 $\mu \mathrm{m}$ droplets at low temperatures, but two-stage ignition is not observed.

初始直径为 20-100 的孤立正庚烷液滴的自燃$\mu \text{米}$使用 4 atm 和 700–1200 K 的空气进行模拟，其中包括回热微型涡轮机的典型运行条件。由于燃烧器中的一些燃料液滴可能被喷射或携带到再循环区附近，因此模拟使用纯空气和热燃烧产物的混合物作为氧化剂。给出并比较了不同条件下物理和混合分数空间中的火焰结构、蒸发时间和自燃时间。检查的变量包括空气预热温度、热产品稀释量、初始燃料液滴直径、氧化剂温度和氧气浓度。结果表明，微型涡轮机条件下纯空气中的液滴在点火前完全蒸发，这表明预蒸发概念适用于微型涡轮机。用热燃烧产物稀释主要通过提高氧化剂温度来减少着火延迟时间。低温化学对液滴点火没有显着影响，因为即使添加少量热燃烧产物也可以将氧化剂温度提高到高于低温动力学的温度。冷焰只被观察到 100 $\mu \mathrm{米}$液滴在低温下，但没有观察到两级点火。