Study of the spray characteristics of a diesel surrogate for diesel engines under sub/supercritical states injected into atmospheric environment
Study of the spray characteristics of a diesel surrogate for diesel engines under sub/supercritical states injected into atmospheric environment
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亚/超临界状态下注入大气环境的柴油机柴油替代品的喷雾特性研究
DOI：
10.1016/j.fuel.2018.05.050
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发表时间：
2018-10
期刊：
影响因子：
7.4
通讯作者：
Xinghe Hou
中科院分区：
文献类型：
--
作者：
Fushui Liu;Yongli Gao;Zheng Zhang;Xu He;Han Wu;Cheng Zhang;Fanming Zeng;Xinghe Hou
碳氢燃料在过热和超临界条件下的喷射特性与传统的液体燃料喷射有很大的不同。本研究采用背光影法和纹影法研究了正庚烷液相和气相的宏观喷射几何形状，考察了燃油温度、喷射压力和喷嘴直径等不同操作条件下喷射模式的差异。此外，还对整体和近场喷雾结构进行了分析，揭示了内部机理。实验过程中，环境保持常压（25 °C, 0.1 MPa）不变，喷射压力在3 ~ 5 MPa范围内变化，始终高于燃油临界压力，燃油温度在25 ~ 300 °C范围内变化，从液态过渡到超临界状态。根据燃料温度和喷雾几何形状确定了四种不同的喷雾状态：液体状态、闪沸状态、近临界状态和超临界状态。根据热力学原理对喷射路径进行了分析。结果表明，在液态状态下，燃料温度对饱和蒸汽温度为98 ℃以下的宏观液相和气相特性影响较小。当温度升高到200 ℃左右，处于闪沸状态时，液、气两相局部喷雾扩散角增大，喷雾的下游液相逐渐消失，气相图像出现高强度湍流。在燃料温度从200 °C到临界点（267 °C）的近临界状态下，汽相局部喷射角开始减小，喷嘴出口处仅能看到一小部分液相，同时可以看到激波沸腾和闪蒸沸腾。当燃油温度超过超临界状态下的临界点时，燃油喷射与燃气喷射相似。在超临界状态下，观察到一种称为马赫盘的稳定激波结构，燃料温度对马赫盘位置和直径的影响很小。而燃油压力和喷管直径对马赫盘位置和直径影响较大。
The spray characteristics of hydrocarbon fuel under superheated and supercritical conditions are quite different from the traditional liquid fuel injection. In this study, the macroscopic liquid phase and vapor phase spray geometry of n-heptane was investigated by Backlit Shadowgraph and Schlieren method to investigate the differences of spray pattern under various operation conditions such as fuel temperature, injection pressure and nozzle diameter. Furthermore, both the overall and near-field spray structures were analyzed to reveal the internal mechanism. During the experiments, the ambient environment was kept constant at atmospheric condition (25 °C, 0.1 MPa), the injection pressure was varied from 3 MPa to 5 MPa, always higher than the fuel critical pressure, and the fuel temperature was changed from 25 °C to 300 °C, spanning from liquid to supercritical state. Four different spray regimes have been identified based on the fuel temperature and spray geometry: liquid regime, flash boiling regime, near-critical regime and supercritical regime. Injection paths were analyzed on the basis of thermodynamic principle. The results showed that the fuel temperature has a minor effect on the macroscopic liquid phase and vapor phase characteristics below saturated-vapor temperature of 98 °C at the liquid regime. As the temperature is increased to about 200 °C, which is in the flash boiling regime, the local spray spreading angle of both the liquid and vapor phases increases, the downstream liquid phase of spray disappears gradually and high-intensity turbulence appears in the vapor phase image. At the near-critical regime where the fuel temperature is from 200 °C to the critical point (267 °C), the local spray angle of vapor phase begins to decrease and only a small area of liquid phase at the nozzle exit can be seen, while both the shock and flash boiling are visible. When the fuel temperature goes beyond the critical point locating in supercritical regime, the fuel spray is similar to a gas jet. The steady shock structure called Mach disk was observed and the fuel temperature has little influence on the Mach disk position and diameter in the supercritical regime. However, the fuel pressure and nozzle diameter significantly affect the Mach disk position and diameter.
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影响因子：
2.6
作者：
B. Chehroudi;R. Cohn;D. Talley
通讯作者：
B. Chehroudi;R. Cohn;D. Talley
DOI：
10.1016/j.ijheatmasstransfer.2014.08.081
发表时间：
2014-12
影响因子：
5.2
作者：
L. Qiu;R. Reitz
通讯作者：
L. Qiu;R. Reitz
DOI：
10.4271/820356
发表时间：
1982-02
期刊：
--
影响因子：
--
作者：
L. Hoppie
通讯作者：
L. Hoppie
DOI：
10.4271/2004-01-0929
发表时间：
2004-03
期刊：
--
影响因子：
--
作者：
S. Saulnier;S. Guilain
通讯作者：
S. Saulnier;S. Guilain
影响因子：
1.9
作者：
J. Pastor;J. Arrégle;A. Palomares
通讯作者：
J. Pastor;J. Arrégle;A. Palomares