Investigation of Vaporized Kerosene Injection and Combustion in a Supersonic Model Combustor

Injection and combustion of vaporized kerosene was experimentally investigated in a Mach 2.5 model combustor at various fuel temperatures and injection pressures. A unique kerosene heating and delivery system, which can prepare heated kerosene up to 820 K at a pressure of 5.5 MPa with negligible fuel coking, was developed. A three-species surrogate was employed to simulate the thermophysical properties of kerosene. The calculated thermophysical properties of surrogate provided insight into the fuel flow control in experiments. Kerosene jet structures at various preheat temperatures injecting into both quiescent environment and a Mach 2.5 crossflow were characterized. It was shown that the use ofvaporized kerosene injection holds the potential of enhancing fuel-air mixing and promoting overall burning. Supersonic combustion tests further confirmed the preceding conjecture by comparing the combustor performances of supercritical kerosene with those of liquid kerosene and effervescent atomization with hydrogen barbotage. Under the similar flow conditions and overall kerosene equivalence ratios, experimental results illustrated that the combustion efficiency of supercritical kerosene increased approximately 10-15% over that of liquid kerosene, which was comparable to that of effervescent atomization.

Performance of a Supersonic Model Combustor using Vaporized Kerosene Injection

Characteristics of supersonic combustion by injecting kerosene vapor into a Mach 2.5 crossflow at various preheat temperatures and pressures were investigated experimentally. A two-stage heating system has been designed and tested, which can prepare heated kerosene of 0.8 kg up to 820 K at pressure of 5.5 Mpa with minimum/negligible fuel coking. In order to simulate the thermophysical properties of kerosene over a wide range of thermodynamic conditions, a three-component surrogate that matches the compound class of the parent fuel was employed. The flow rate of kerosene vapor was calibrated using a sonic nozzle. Computed flow rates using the surrogate fuel are in agreement with the experimental data. Kerosene jets at various preheat temperatures injecting into both quiescent environment and Mach 2.5 crossflow were visualized. It was found that at injection pressure of 4 Mpa and preheat temperature of 550 K the kerosene jet was completely in vapor phase, while keeping almost the same penetration depth as compared to the liquid kerosene injection. Supersonic combustion tests were also carried out to compare the combustor performance for the cases of vaporized kerosene injection, liquid kerosene injection, and effervescent atomization with hydrogen barbotage, under the similar stagnation conditions. Experimental results demonstrated that the use of vaporized kerosene injection leads to better combustor performance. Further parametric study on vaporized kerosene injection in a supersonic model combustor is needed to assess the combustion efficiency as well as to identify the controlling mechanism for the overall combustion enhancement.

Investigation of Vaporized Kerosene Injection and Combustion in a Supersonic Model Combustor

Injection and combustion of vaporized kerosene was experimentally investigated in a Mach 2.5 model combustor at various fuel temperatures and injection pressures. A unique kerosene heating and delivery system, which can prepare heated kerosene up to 820 K at a pressure of 5.5 MPa with negligible fuel coking, was developed. A three-species surrogate was employed to simulate the thermophysical properties of kerosene. The calculated thermophysical properties of surrogate provided insight into the fuel flow control in experiments. Kerosene jet structures at various preheat temperatures injecting into both quiescent environment and a Mach 2.5 crossflow were characterized. It was shown that the use ofvaporized kerosene injection holds the potential of enhancing fuel-air mixing and promoting overall burning. Supersonic combustion tests further confirmed the preceding conjecture by comparing the combustor performances of supercritical kerosene with those of liquid kerosene and effervescent atomization with hydrogen barbotage. Under the similar flow conditions and overall kerosene equivalence ratios, experimental results illustrated that the combustion efficiency of supercritical kerosene increased approximately 10-15% over that of liquid kerosene, which was comparable to that of effervescent atomization.

Heat Transfer of Aviation Kerosene at Supercritical Conditions

The heat transfer characteristics of China no. 3 kerosene were investigated experimentally and analytically under conditions relevant to a regenerative cooling system for scramjet applications. A test facility developed for the present study can handle kerosene in a temperature range of 300-1000 K, a pressure range of 2.6-5 MPa, and a mass How rate range of 10-100 g/s. In addition, the test section was uniquely designed such that both the wall temperature and the bulk fuel temperature were measured at the same location along the flowpath. The measured temperature distributions were then used to analytically deduce the local heat transfer characteristics. A 10-component kerosene surrogate was proposed and employed to calculate the fuel thermodynamic and transport properties that were required in the heat transfer analysis. Results revealed drastic changes in the fuel flow properties and heat transfer characteristics when kerosene approached its critical state. Convective heat transfer enhancement was also found as kerosene became supercritical. The heat transfer correlation in the relatively low-fuel-temperature region yielded a similar result to other commonly used jet fuels, such as JP-7 and JP-8, at compressed liquid states. In the high-fuel-temperature region, near and beyond the critical temperature, heat transfer enhancement was observed; hence, the associated correlation showed a more significant Reynolds number dependency.

OpenOffice.org对非BMP平面字符支持的实现

Unicode标准中的非BMP平面字符多用于古籍研究或者少数民族语言文字,由于这些字符的使用面特别窄,多数软件系统包括办公软件都不支持对这些字符的处理。本文以开源办公套件OpenOffice.org为基础,分析了它对非BMP平面支持的现状,然后着重探讨了实现对非BMP平面字符的全面支持所需要解决的一系列问题,并分别给出了合理的改进方案,最后以CJK和藏文为例展示了改进后的效果。

Study of turbulent heat transfer of aviation kerosene flows in a curved pipe at supercritical pressure

The now and heat transfer characteristics of China No. 3 aviation kerosene in a heated curved tube under supercritical pressure are numerically investigated by a finite volume method. A two-layer turbulence model, consisting of the RNG k-epsilon two-equation model and the Wolfstein one-equation model, is used for the simulation of turbulence. A 10-species kerosene surrogate model and the NIST Supertrapp software are applied to obtain the thermophysical and transport properties of the kerosene at various temperature under a supercritical pressure of 4 MPa. The large variation of thermophysical properties of the kerosene at the supercritical pressure make the flow and heat transfer more complicated, especially under the effects of buoyancy and centrifugal force. The centrifugal force enhances the heat transfer, but also increases the friction factors. The rise of the velocity caused by the variation of the density does not enhance the effects of the centrifugal force when the curvature ratios are less than 0.05. On the contrary, the variation of the density increases the effects of the buoyancy. (C) 2010 Elsevier Ltd. All rights reserved.

基于代理模型的水下滑翔机机翼设计优化方法

在复杂工程系统的概念设计优化中,高精度数值分析方法得到广泛应用,将高精度数值分析与优化方法有机结合,对设计空间展开全面搜索与寻优,已经成为现代设计优化方法的重要发展方向。以水下滑翔机的概念设计为研究对象,引入代理模型,控制高精度分析试验的数量,有效地化解精度与效率之间的矛盾。将参数化几何建模、网格划分以及流体数值模拟分析集成为自动分析流程,并以此为基础采用试验设计理论,构建代理模型,解决水下滑翔机机翼的多目标设计优化问题。给出基于代理模型的设计优化过程,并系统地比较几种试验设计方法的适应性,重点讨论多项式响应面和径向基函数代理模型,所得代理模型相对误差小于2%。采用梯度寻优方法与遗传算法在给定设计空间内进行全面搜索,获得机翼的最佳平面构形,水下滑翔机的升阻比提高6.76%,俯仰力矩的绝对值由0.2760N•m降低为0.0015N•m,提高水下滑翔机的运动性能。