Heat Transport Characteristics of a Non-Premixed Turbulent Flame and nomaly in Heat Transfer : Counter-Gradient Diffusion

结果已在以下三篇论文中报告。摘要是：（1）“一个双热电偶探头技术估计热电偶时间常数的燃烧流：在现场参数识别的一阶滞后系统”：一个双热电偶探头，由两个细线热电偶的不相等的直径，是一种新的技术估计热电偶时间常数没有任何动态校准的热电偶响应。该技术最适用于测量湍流燃烧中的温度波动。在本研究中，该技术的可靠性和适用性进行了评估，在一个加热的气缸（无燃烧）的湍流尾流。同时使用快速响应的细丝电阻温度计（冷丝）提供参考温度。冷丝测量和补偿热电偶测量之间的定量和详细的比较表明，以前的估计方案给出了 关于我们 热电偶时间常数小于适当值，除非热电偶信号中的噪声可以忽略和/或双热电偶探头的空间分辨率足够高。该方案已被改进，以最大限度地提高两个补偿热电偶输出之间的相关系数。改进的方案提供了更好的热电偶响应补偿。该方法一般适用于一阶滞后系统的现场参数辨识。(2)“高温湍流中速度和温度的同时测量”：本文论述了一种简单可靠的同时测量高温湍流（包括燃烧）中速度和温度的技术。该技术是基于激光多普勒测速仪（LDV）和补偿细线热电偶的组合。本研究的一个中心问题是找到所提出的技术的适用性和可靠性。为此目的，一个双热电偶探头与细冷丝（田川，Shimoji和太田，1998年），使在现场测量热电偶的时间常数和准确的补偿的热电偶响应，结合LDV。该技术是在湍流尾流背后的加热气缸，其热场是普通的温度和波动相对较小的幅度进行测试。这使得能够对测量精度进行严格的评估。结果表明，该技术是高可靠性的，是有效的研究各种非等温湍流传热过程。(3)“弯曲矩形通道内湍流火焰的传热特性”：对弯曲矩形通道（180 °弯曲）内非预混湍流火焰的传热特性进行了实验研究。采用LDV和细丝热电偶相结合的技术测量了速度场和温度场的关键湍流量，如雷诺应力分量和湍流热通量。这些测量结果显示了发生反梯度热传输的直接证据，这可以归因于弯曲管道的径向方向上存在强压力梯度。阴影技术显示的温度场揭示了完全不同的行为之间的燃烧气体包的高，低压侧的流动，和观察可能有助于我们解释的逆梯度热传输的湍流与燃烧的发生机制。少

The results have been reported in the following three papers. The abstracts are :(1) "A two-thermocouple probe technique for estimating thermocouple time constants in flows with combustion : in situ parameter-identification of a first-order lag system" : A two-thermocouple probe, composed of two fine-wire thermocouples of unequal diameters, is a novel technique for estimating thermocouple time constants without any dynamic calibration of the thermocouple response. This technique is most suitable for measuring fluctuating temperatures in turbulent combustion. In the present study, the reliability and applicability of this technique are appraised in a turbulent wake of a heated cylinder (without combustion). A fine-wire resistance thermometer (cold wire) of fast response is simultaneously used to provide a reference temperature. A quantitative and detailed comparison between the cold-wire measurement and the compensated thermocouple ones shows that a previous estimation scheme gives ther … More mocouple time constants smaller than appropriate values, unless the noise in the thermocouple signals is negligible and/or the spatial resolution of the two-thermocouple probe is sufficiently high. The scheme has been improved so as to maximize the correlation coefficient between the two compensated- thermocouple outputs. The improved scheme offers better compensation of the thermocouple response. The present approach is generally applicable to in situ parameter-identification of a first-order lag system.(2) "Simultaneous Measurement of Velocity and Temperature in High Temperature Turbulent Flows" : This paper deals with a simple and reliable technique for simultaneous measurement of velocity and temperature in high-temperature turbulent flows, including combustion. The technique is based on the combination of a laser Doppler velocimeter (LDV) and a compensated fine-wire thermocouple. A central issue of this study is to find the applicability and reliability of the technique proposed. For this purpose, a two-thermocouple probe with a fine cold wire (Tagawa, Shimoji and Ohta, 1998), which enables in situ measurement of thermocouple time constants and accurate compensation of the thermocouple response, is combined with the LDV.The technique is tested in a turbulent wake behind a heated cylinder, whose thermal field is of ordinary temperature and fluctuates with relatively small amplitude. This enables critical assessment of the measurement accuracy. The results show that the technique is highly reliable and is effective in investigating heat transport processes in various non-isothermal turbulent flows.(3) "Heat transport characteristics of a turbulent flame formed in a curved rectangular duct" : Heat transport characteristics of a non-premixed turbulent flame formed in a curved rectangular duct (180-degree bend) are investigated experimentally. Key turbulence quantities of velocity and thermal fields such as Reynolds stress components and turbulent heat fluxes are measured using a combined LDV and fine-wire thermocouple technique. These measurements show direct evidence of the occurrence of counter-gradient heat transport, which can be ascribed to the existence of a strong pressure gradient in the radial direction of the curved duct. The shadowgraph technique for visualizing the temperature field reveals totally different behavior of the burned gas parcels between the high- and the low-pressure sides of the flow, and the observations may help us explain the mechanism of the occurrence of the counter-gradient heat transport in turbulent flows with combustion. Less