高压旋喷射流流动特性及应用研究

发布时间：2018-07-27 11:03

【摘要】：我国是煤炭消费大国,同时也是煤炭开采大国,煤矿瓦斯灾害一直是困扰煤矿安全高效开采的主要难题,为解决煤矿工程中瓦斯治理难的问题,课题组在多年实践和积累下提出了煤层网格化造缝预抽瓦斯方法,其主体思路是利用高压旋喷射流逐层切割煤岩,引发其裂隙网格化贯通,促使其整体卸压、增透,对提高低透气性煤层的采前预抽效果极其显著。作为一种安全、高效的造缝预抽瓦斯方案,高压旋喷射流技术在此领域的作用正方兴未艾,然而,其相关理论研究较为缺乏,特别是在双壁面受限空间作用的射流湍流特性及射流割缝范围预测等方面涉猎较少。此外,已有试验还表明高压旋喷射流割缝系统工况转换过程中存在显著的瞬变特性,极易诱发煤体失稳、抱钻等现象。针对于此,本文以对称双壁面受限空间射流为研究对象,基于CFD和PIV技术分析了雷诺数、对称双壁面受限空间宽度以及旋转数等因素对其流动特性的影响规律,探讨了割缝断面形貌的形成机理；实验研究了高压旋喷射流割缝系统在工况转换过程中的瞬变特性,分析了喷嘴结构、数量以及阀芯结构变化对系统瞬变性能的影响规律；利用均匀试验方法分析了高压旋喷射流割缝半径随射流压力、喷嘴直径以及钻杆速度的变化规律,研究了割缝半径的预测方法；最后,在平顶山十矿和淮南谢一矿进行了现场试验,探讨了高压旋喷射流煤层内网格化造缝能力和预防煤与瓦斯突出效果。论文主要取得了以下成果： (1)提出了高压旋喷射流对称双壁面受限空间的物理模型,确定了雷诺应力数值计算模型及工况；建立了对称双壁面受限空间实体模型,并采用PIV测试分析了其流场结构与运动特征,验证了高压旋喷射流流动数值模拟方法的可靠性和可信性。 (2)基于雷诺应力湍流模型模拟了高压(高雷诺数)条件下双壁面受限空间内射流压力(雷诺数)、受限空间宽度和旋转速度(旋转数)对射流流动特性的影响规律。结果表明双壁面受限空间射流具有三个主体区域(射流核心段区域、自由射流段区域、双壁面受限段区域)以及两个过渡区域(从核心段至自由射流段过渡区域、自由射流段至壁面受限段过渡区域)；雷诺数未影响主体区域射流的流动规律和动力学特性,但对自由射流至壁面受限段区域影响颇为显著,并使其局部产生负压；双壁面受限空间宽度虽会形成空间上的“迟滞效应”,但对射流流动状态和流动特性影响较小；旋转数促使流动形态和动力学特性分布发生偏向,且在局部区域产生漩涡结构,但基本未影响射流流态区域特征；高压旋喷射流割缝形成的椭圆盘型形貌可判定为局部负压拉应力,壁面冲蚀、冲刷作用以及空间“迟滞效应”作用的协同结果所致。 (3)基于流体过渡过程理论研究了高压旋喷射流割缝系统的过渡过程特性,建立相应的理论模型并对其有效性进行了验证。通过对高压旋喷射流割缝系统瞬变特性的分析,优化了相关执行部件结构及工作参数,保证了系统施工割缝过程转变的安全性。 (4)根据双壁面受限空间射流流动特性和煤体破碎规律,建立了预测高压旋喷射流割缝半径的方法,并采用均匀试验方法进行了实验验证,结果表明割缝半径与喷嘴直径成正比和射流压力的四分之一次方均成正比。 (5)研制出适用于低透气性煤层瓦斯治理的高压旋喷射流割缝增透技术系统成套装备,并在平顶山十矿己15-24080煤层中安全实施。现场试验表明,采用高压旋喷射流割缝技术能够减少钻孔数量,缩短施工钻孔时间,提高施工效率,相对于普通钻孔,割缝钻孔的瓦斯浓度明显增大,且衰减较慢,而流量变化不大,在抽采4个月内,割缝瓦斯抽采纯量提高了3倍以上。 (6)淮南谢一矿B11b煤层现场试验表明,在割缝后60天内,割缝钻孔单孔瓦斯浓度大部分保持在90%左右,相对于未割缝钻孔,单孔瓦斯浓度衰减缓慢。割缝孔瓦斯抽采量同比提高了30%以上,
[Abstract]:China is a big coal consumption country, and it is also a big coal mining country. Coal mine gas disaster is the main problem that plagued coal mine safe and efficient mining. In order to solve the difficult problem of gas management in coal mine, the project group put forward the method of coal seam mesh pre suction gas extraction under many years' practice and accumulation, the main idea of which is to use high pressure spin. The cutting of coal and rock by jet stream causes its crack to be meshed and connected to promote its overall pressure relief and penetration. It is very significant to improve the pre extraction effect of low permeability coal seam. As a safe and efficient seam pre gas extraction scheme, the role of high pressure jet flow technology is in the ascendant, however, its related theoretical research is more important. In particular, the characteristics of the jet turbulence and the prediction of the jet slit range are less involved. In addition, the existing experiments also show that there is a significant transient characteristic in the conversion process of the high pressure jet flow slotting system, which is very easy to induce the instability of the coal body and the drilling.
In this paper, a symmetric double wall confined space jet is used as the research object. Based on CFD and PIV technology, the influence rules of Reynolds number, the limited space width of the symmetrical double wall space and the rotation number on the flow characteristics are analyzed. The formation mechanism of the cross section morphology is discussed, and the experiment is carried out to study the high pressure jet slit system in the work. The influence law of the nozzle structure, quantity and the change of the valve core structure on the transient performance of the system is analyzed. The variation law of the slotting radius with the jet pressure, the diameter of the nozzle and the velocity of the drill rod is analyzed by the uniform test method, and the prediction method of the slotting radius is studied. Finally, the method is used to predict the radius of the slotting. In Pingdingshan ten mine and Xiyi mine in Huainan, the field tests were carried out to discuss the seam building capacity of the internal network of high pressure jet flow and the effect of preventing coal and gas outburst.
(1) a physical model of symmetric double wall confined space with high pressure jet flow is proposed. The numerical model and working condition of Reynolds stress are determined. A symmetric double wall limited space entity model is established. The structure and motion characteristics of the flow field are analyzed by PIV test. The reliability of the numerical simulation method of high pressure jet flow flow is verified and the reliability of the numerical simulation method is verified. Trustworthiness.
(2) based on the Reynolds stress turbulence model, the influence of the jet pressure (Lei Nuoshu) on the confined space within the confined space under the condition of high pressure (high Reynolds number), the limited space width and the rotation velocity (rotation number) on the flow characteristics of the jet. The results show that the two wall confined space ejection has three main regions (the jet core region, free jet). The Reynolds number does not affect the flow law and dynamic characteristics of the jet in the main region, but it has a significant influence on the free jet to the wall limited section, and makes it part of the region, and two transition regions (the transition region from the core to the free jet section, the free jet section to the transition region of the wall limited section). Negative pressure is produced; the limited space width of double wall surface will form a "hysteresis effect" in space, but it has little influence on the flow state and flow characteristics of the jet. The rotation number causes the distribution of flow morphology and dynamics to occur in the deviation, and the vortex structure is produced in the local region, but it does not affect the regional characteristics of the jet flow. The shape of the elliptical disc formed by the jet slit can be determined as the result of the local negative pressure tensile stress, the wall erosion, the scour effect and the synergistic result of the space "hysteresis effect".
(3) based on the theory of fluid transition process, the characteristics of the transition process of the high pressure jet slit system are studied, the corresponding theoretical model is established and its validity is verified. Through the analysis of the transient characteristics of the high pressure swirling jet slit system, the structure and the working parameters of the related components are optimized, and the construction slotting process of the system is ensured. The security of the transformation.
(4) according to the flow characteristics of the confined space jet and the breaking law of the coal body, a method to predict the cutting radius of the high pressure jet flow is established, and the uniform test method is used to verify the experimental results. The results show that the radius of the slotting is proportional to the diameter of the nozzle and the 1/4 square of the jet pressure.
(5) a complete set of equipment for high pressure jet flow seams is developed for the treatment of low permeability coal seam gas, and it is carried out safely in 15-24080 coal seam of Pingdingshan ten mine. The field test shows that the high pressure rotary jet slit technology can reduce the number of drilling holes, shorten the drilling time and improve the construction efficiency. Through drilling, the gas concentration in the slotted hole is obviously increased, and the attenuation is slow, but the flow rate is not changed. In the 4 months of extraction, the pure gas extraction is increased by more than 3 times.
(6) the field test of the B11b coal seam in the Shiyi mine of Huainan shows that the gas concentration of the single hole in the slotted hole is mostly kept around 90% within 60 days after the slotting, and the gas concentration of the single hole is slowly decreased compared with the non slit drilling. The gas extraction capacity of the slotted hole is increased by more than 30% over the same period.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TD712

【参考文献】