固态流化单喷嘴破碎水合物深度预测新模型及验证

A new model for predicting hydrate breaking depth of single nozzle in solid fluidization exploitation and its verification

为提升固态流化开采中喷嘴对天然气水合物的射流破碎效率,推动固态流化开采规模化、商业化应用,基于CFD和现有单喷嘴射流破碎实验结果,开展了射流压力、收缩段长度和喷嘴直径对锥直形单喷嘴射流速度分布的影响规律研究,并建立了固态流化单喷嘴破碎水合物深度预测新模型。研究结果表明:(1)锥直形喷嘴射流核心段长度与喷嘴直径呈正相关关系,而与射流压力、收缩段长度无关;(2)射流基本段速度衰减与喷嘴直径和射流压力呈负相关,而与收缩段长度无关。进一步结合非成岩水合物临界破碎速度方程,初步建立了极限破碎深度随单喷嘴直径和射流压力变化的数学模型,并基于单喷嘴射流破碎实验结果进行了模型验证与修正。结论认为:(1)建立的极限破碎深度模型是正确的,修正后模型的计算结果与实验值的最大偏差为7.7%,能够满足固态流化实际工程对水合物破碎的要求;(2)建议开展组合喷嘴极限破碎深度模型研究,分析多个喷嘴组合情况下布置夹角和布置间距对极限破碎深度的影响,最终形成一套水合物高效破碎工具设计方法。

In order to improve the jet breaking efficiency of the nozzle on natural gas hydrate in solid fluidization exploitation and promote the large-scale industrial application of solid fluidization exploitation,this paper studies the influential laws of jet pressure,contraction section length and nozzle diameter on the distribution of the jet velocity of single cylindrical cone-shaped nozzle based on CFD and existing single-nozzle jet breaking experimental results.In addition,a new model for predicting the hydrate breaking depth of single nozzle in solid fluidization exploitation is established.And the following research results are obtained.First,the length of the core jet section of cylindrical cone-shaped nozzle is positively correlated with nozzle diameter,but is independent of jet pressure and constricted section length.Second,the velocity attenuation of the basic jet section is negatively correlated with nozzle diameter and jet pressure,but is independent of constricted section length.Furthermore,a mathematical model of ultimate breaking depth varying with single nozzle diameter and jet pressure is preliminarily established based on the critical breaking velocity equation of non-diagenetic hydrate,and it is verified and modified based on single-nozzle jet breaking experimental results.In conclusion,the newly established model of ultimate breaking depth is correct,and the maximum error between the calculation result by the modified model and the experimental result is 7.7%,which can meet the requirements for hydrate breaking in actual solid fluidization engineering.It is recommended to research the model of ultimate breaking depth for combined nozzle and analyze the influences of included angle arrangement and spacing arrangement on ultimate breaking depth under the conditions of multiple-nozzle combination,so as to ultimately form a set of design methods of efficient hydrate breaking tools.