超临界压力下航空煤油圆管流动和传热的数值研究

Numerical study of convective heat transfer of aviation kerosene flows in pipe at supercritical pressure

关键词:  超临界态+  煤油  传热  数值计算

Key words:  Supercritical state +  Kerosene  Heat transfer  Numerical calculation

摘要:

对超临界压力下大庆RP-3航空煤油在小管道内的流动、传热过程进行了数值研究。湍流模拟采用了RNG k-ε两方程模型和Wolfstein一方程模型结合的两层模型;同时,采用煤油的10组分替代模型以及NIST Super-trapp程序库对大庆3号航空煤油的热物理和输运特性进行了确定。圆管传热的计算条件为:入口压力4 MPa,入口温度300 K,质量流量范围:0.06～0.12 kg/s,壁面热流密度范围:300～700 kW/m2。计算结果显示,煤油的流动和传热特性比水、二氧化碳等简单化合物复杂得多。在超临界压力下,煤油的吸热升温导致其热物理特性以及流动特性均发生剧烈变化,其中,雷诺数沿管道方向上升了至少一个量级,而普朗特数下降了一个量级。在加热开始段,煤油的对流传热系数迅速上升;当壁面温度超过其拟临界温度后,对流传热系数略有所回落;随着煤油温度的进一步上升,传热系数又得到明显增强。计算表明,煤油对流换热特性的变化与煤油复杂的高温热物理特性以及湍流流动在近壁区的增强和抑止有关。

Abstract:

Flow and heat transfer characteristics of China No.3 aviation kerosene in a heated tube and under supercritical pressure were investigated numerically.A two-layer turbulent model,consisting of RNG k-ε model and Wolfstein one-equation model,was used for the simulation of turbulence.A 10-species kerosene surrogate model and NIST Supertrapp software were applied to obtain thermophysical and transport properties of the Daqing No.3 kerosene at varied temperature.Flow conditions of the current study were listed as following: the inlet pressure was 4 MPa;the inlet temperature was 300 K;the mass flows were set from 0.06 to 0.12 kg/s;the wall heat flux was varied from 300 to 700 kW/m2.Results showed that the kerosene thermophysical and flow properties change significantly as the fuel temperature increases along the tube length,of which Reynolds number increases by at least one magnitude and Prandtl number decreases by one magnitude.The heat transfer coefficient increases at the beginning section of the tube,then it decreases slightly as the wall temperature approaches the pseudo-critical temperature,and after that,the heat transfer coefficient rises again,indicating heat transfer enhancement.The current study indicated that the variation in the heat transfer properties can attribute to the complicated thermophysical characteristics of the supercritical kerosene and the change in the turbulence intensity in the near wall region.