一种新型等动力采样头的数值模拟

Numerical Simulation of an Isokinetic Sampler

针对船舶发动机进口空气含盐量的测量设计了一种等动力采样头。通过计算流体动力学(CFD)方法对设计的等动力采样头进行了数值模拟,得到了其头部流场分布、在不同粒径下流场滑移速度分布和滑移速度梯度分布,对比分析了其与美国EPA标准采样头在不同工况下的采样误差。并研究了采样头安装角度和采样速度变化对采样精度的影响。计算结果表明:该等动力采样头的性能明显优于EPA标准采样头的性能;随着液滴粒径的增大,采样误差增加;随着来流速度的减小,采样误差降低;当采样头偏转3°时,在三种粒径下采样误差最大仅为1.87%;在采样速度偏差士10%的情况下,采样误差全都不高于2.71%。为今后空气含盐量的高精度测量提供了技术支撑。

An isokinetic sampler which used for measuring of salt content in imported air of marine engine was designed.Numerical simulation of an isokinetic sampler was conducted to study the performance,and the flow field,the distributions of the slip velocity and slip velocity gradient were obtained.Comparative analysis of sampling error between the isokinetic sampler and EPA standard sampler was carried out in different working conditions.And the influences of the sampler installation angle and the sampling speed variation on the sampling accuracy were studied.The simulation results showed that the performance of the isokinetic sampler is better than that of the EPA standard sampler.With the increase of droplet size,the sampling error increases;with the decrease of the flow velocity,the sampling error is reduced.When the sampler deflects of 3 degrees,under the condition of three different particle size,the maximum sampling error is only 1.87%.Each of the sampling error is no more than 2.71%in the case of the sampling speed variation in ±10%.It provides the technical support for the high precision measurement of the salt content in the future.