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

非预混湍流火焰的传热特性和传热中的正常现象：反梯度扩散

• 批准号: 09650235
• 负责人: TAGAWA Masato
• 金额: $ 1.47万
• 依托单位: Nagoya Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650235/
• 关键词: Combustion; Turbulence; Laser-Doppler Velocimetry; Thermocouple; Turbulent Heat Flux; Counter-Gradient Diffusion; Simultaneous Measurement; Response Compensation Y.

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

研究结果已发表在以下三篇论文中。(1)“一种估算燃烧流动中热偶时间常数的双热电偶探头技术：一阶滞后系统的现场参数辨识”：由两个直径不等的细丝热电偶组成的双热电偶探头是一种无需对热电偶响应进行任何动态校准即可估算热电偶时间常数的新技术。该技术最适合测量湍流燃烧中的温度波动。在本研究中，评估了该技术的可靠性和适用性，在被加热的圆柱体的湍流尾迹(不燃烧)。同时使用快速响应的细丝电阻温度计(冷丝)来提供参考温度。对冷线测量和补偿热电偶测量的定量和详细比较表明，以前的估计方案给出了…更多的热电偶时间常数小于适当的值，除非热电偶信号中的噪声可以忽略和/或两个热电偶探头的空间分辨率足够高。对该方案进行了改进，使两个补偿热电偶输出之间的相关系数达到最大。改进后的方案提供了更好的热电偶响应补偿。本方法一般适用于一阶滞后系统的现场参数辨识。(2)“高温湍流速度和温度的同时测量”：本文介绍了一种简单可靠的高温湍流速度和温度的同时测量技术，包括燃烧。这项技术是基于激光多普勒测速仪(LDV)和补偿细丝热电偶的组合。这项研究的一个中心问题是找出所提出的技术的适用性和可靠性。为此，将Tagawa，Shimoji和Ohta，1998)的双热电偶测头与LDV相结合，实现了热电偶时间常数的现场测量和热电偶响应的精确补偿。该技术在加热圆柱体后面的湍流尾迹中进行了测试，加热圆柱体的温度场为常温，波动幅度相对较小。这使得能够对测量精度进行关键评估。结果表明，该方法具有较高的可靠性，能有效地研究各种非等温湍流流动中的热传递过程。(3)《弯曲矩形管道中湍流火焰的传热特性》：对弯曲矩形管道(180度弯曲)中非预混湍流火焰的传热特性进行了实验研究。利用激光测速和细丝热电偶相结合的方法，测量了雷诺应力分量和湍流热流密度等速度场和热场的关键湍流量。这些测量结果直接证明了逆梯度热传输的发生，这可以归因于弯曲管道径向存在强烈的压力梯度。用阴影技术显示温度场，揭示了高压侧和低压侧燃烧气团的完全不同的行为，这些观察结果有助于我们解释有燃烧的湍流中逆梯度热传输的发生机制。较少

项目成果

田川正人: "乱流燃焼場における速度と温度の同時測定" 豊田研究報告. 51. 73-81 (1998)

Masato Takawa：“湍流燃烧场中速度和温度的同步测量”丰田研究报告 51. 73-81 (1998)。

田川正人: "二線式熱電対による変動温度測定法の精度評価と改良" 日本機械学会論文集(B編). 64. 3077-3083 (1998)

田川正人：“使用两线热电偶的脉动温度测量方法的精度评估和改进”日本机械工程学会会刊（B 版）64. 3077-3083（1998 年）。

M.Tagawa: "A two-thermocouple probe technique for estimating thermocouple time constants in flows with combustion : in situ parameter-identification of a first-order lag system" Review of Scientific Instruments. 69. 3370-3378 (1998)

M.Takawa：“用于估计燃烧流中热电偶时间常数的双热电偶探针技术：一阶滞后系统的原位参数识别”科学仪器评论。

M.Tagawa, T.Shimoji and Ohta: "Improvement of a two-thermocouple probe technique for fluctuating temperature measurement" Trans.Japan Society of Mechanical Engineers. Vol.64. 3077-3083 (1998)

M.Takawa、T.Shimoji 和 Ohta：“用于波动温度测量的双热电偶探头技术的改进”横贯日本机械工程师学会。

M.Tagawa: "A two-thermocouple probe technique for estimating thermocouple time constants in flows with combustion:In situ parameter-identification of a first-order lag system" Review of Scientific Instruments. 69. 3370-3378 (1998)

M.Takawa：“用于估计燃烧流中热电偶时间常数的双热电偶探针技术：一阶滞后系统的原位参数识别”科学仪器评论。