摘要
在均相流理论的基础上,对气粉两相流喷管的壅塞现象进行了实验考察和理论分析.选择金属铝粉、三氧化二铝粉、空心三氧化二铝粉为固相,空气为气相,通过喷管流动实验测定了不同粉剂与固气比下的气粉两相流达到壅塞的临界压强比,计算得到了表观音速等参数,并在此基础上定义了两相流的有效绝热指数和固相的有效热容.结果表明,在两相流未达到壅塞前,质量流量与滞止压强呈三次曲线关系;在壅塞后质量流量与滞止压强呈线性关系.固相的浓度和物性对气粉两相流的临界参数有明显的影响,固相的有效热容随固气比的增加而减小,随固相导热系数的增大和粒度的减小而增大;对确定的喷管和粉剂粒度,固相的相对有效热容随其导温系数的增大而增大.对常见的气粉两相流,固相对混合物热容的贡献很小,可以用气相的绝热指数按两相平衡流模型近似计算气粉两相流的表观音速.
Based on the theory of two-phase homogeneous equilibrium model （HEM）, the choking phenomena of gas-powder flow were experimentally studied and theoretically analyzed. Experiments were conducted in a horizontal constant cross-section duct with three kinds of powder： Al2O3, hollow Al2O3 and A1, with different densities, specific heat capacities and thermal conductivities, in order to understand the relationship between the mass flow-rate and the inlet stagnant pressure, Applying the choking principle, the apparent critical pressure ratio and apparent sonic velocity （ASV） of gas-powder flow were determined. Considering the thermal relaxation of the two-phase flow, the effective specific heat capacity （ESHC） of solid phase, the effective isoentropic exponent （EIE） of the mixture and the relative effective specific heat capacity （RESHC） were defined, The experimental resuits show that, with the increase of the stagnation pressure, the mass flow rate increases as a cubic polynomial function before choking and linearly after choking. The influence of the physical properties of powders on ASV of gas-powder flow is obtained by the comparison between experimental results of different powders. When solid mass loading （SML） is small, ASV is mainly affected by the thermal conductivity of the powder. When SML is large, the density of the powder affects ASV instead, ESHC of the solid phase decreases with the increase of its loading. The thermal conductivity is the main factor to affect ESHC, while density is hardly so, ESHC of the solid phase is very small （〈0.5%）, and may be ignored. Therefore, the isoentropic exponent of the gas phase can be used as that of the mixture to calculate the ASV of gas-particle flow.
出处
《过程工程学报》
EI
CAS
CSCD
北大核心
2005年第6期591-596,共6页
The Chinese Journal of Process Engineering
关键词
气粉两相流
壅塞现象
表观临界压强比
表观音速
有效绝热指数
有效热容
gas-particle flow
choking phenomenon
apparent critical pressure ratio
apparent sonic velocity
effective isoentropic exponent
effective specific heat capacity
