Institute of Agricultural Engineering, Work Group on Trace Gas and Odour Measurement, University of Bonn, Nussallee 5, D-53115 Bonn, Germany.
J Chromatogr A. 2013 Apr 19;1286:200-7. doi: 10.1016/j.chroma.2013.02.057. Epub 2013 Feb 26.
For olfactometric measurements in combination with gas chromatography a device is needed to split the GC effluent between the detector and the sniffing port. Fixed split ratios are obtained by simple flow splitters with appropriate restrictions towards the two outlets. Variable split ratios are possible with additional control flows. One such device is a dome splitter with one input flow (the GC effluent), two output flows (to the two outlets) and two control inputs. Preliminary experiments revealed deviations from the expected split ratios of such a device. The dimensioning of the flow restrictors at only one working point was not sufficient to obtain the expected split ratios over the whole temperature range of a GC run. Therefore a physical model of the flow system has been developed, taking into account the temperature dependence of the restrictors and the internal pressure in the dome. This included the solution of the flow (respectively the mass) balance under the condition of a compressible, isothermal and laminar flow regime. The measurements are in good agreement with theoretical calculations. The model can therefore be used to optimise the dimensions of the restrictions and to calculate the effective split ratio at a given temperature during the GC run.
对于与气相色谱法结合的嗅闻测量，需要一种设备将 GC 流出物在检测器和嗅闻口之间进行分流。通过对两个出口具有适当限制的简单分流器可获得固定的分流比。通过附加控制流可实现可变的分流比。一种这样的设备是具有一个输入流（GC 流出物）、两个输出流（到两个出口）和两个控制输入的穹顶分流器。初步实验表明，这种设备的预期分流比存在偏差。仅在一个工作点上对限流装置进行尺寸设计不足以在 GC 运行的整个温度范围内获得预期的分流比。因此，已经开发了一种考虑到限流装置的温度依赖性和穹顶内的内部压力的流动系统的物理模型。这包括在可压缩、等温且层流流动条件下求解流量（或质量）平衡。测量结果与理论计算吻合良好。因此，该模型可用于优化限制装置的尺寸，并在 GC 运行期间计算给定温度下的有效分流比。
