Development of Laser-Doppler Vibrating Tube Densimeter with High Accuracy at High Temperatures and Pressures.

我们开发了一种新的振动管密度计，能够测量高达870 K和高达70 MPa的压力。密度计特点是一个δ形的设计，以增强振动谐波的长度，激光多普勒振动检测，宽范围压电输入刺激，所有振动模式的实时显示，以及所有磁铁和管附件的边缘化。振动刺激被应用到一个管子中，用一个压电式演员的时间一步来填充一个管子，其兴趣的物质。输入刺激是完全由计算机感知的。一个氦-霓虹灯激光振动计被用来检测瞬态振动变化，并提供了所有振动模式的FFT分析仪。在校准中，第5-D1振动模式被用来实现最大的灵敏度。一种统计方法已被应用于开发一种校准方程，该方程有效地超过了温度和压力的一个宽范围。一个流动装置是在高温和高压条件下构建的PVT。该系统由一个注射泵进料，高温烤箱，配有预热、密度计和注射泵接收器。当接收机泵在恒定流动模式下运行时，进料泵在恒定压力模式下运行，由于该设备、水、甲醇或水+甲醇混合物的密度在超关键条件下测量了0.006克/厘米的准确性，而接收机泵在恒定压力模式下运行，因此，该数值比分辨率大得多。一种新的密度测量仪，用激光检测方法提取磁铁，并扩展当前振动类型密度测量仪的范围。

We have developed a new vibrating tube densimeter that is capable of measurements of up to 870 K and pressures to 70 Mpa. The densimeter features a δ-shaped design to enhance the length of vibration harmonics, laser-doppler detection of of vibration, wide-range piezoelectric input stimulus, real-time display of all vibration modes, and the elimination of all magnets and tube attachments. Vibrational stimulus is applied to a tube filled with the substance of interest over a time step with a piezoelectric actuator. The input stimulus is simultaneously sensed by computer. A helium-neon laser vibrometer is used to detect transient vibrational changes and an FFT analyzer provides all vibration modes. In the calibrations, the 5ィイD1thィエD1 vibrational mode was used to achieve the greatest sensitivity. A statistical method was applied to develop a calibration equation that was valid over a wide range of temperatures and pressures. A flow apparatus was constructed to PVT at high-temperature and high-pressure conditions. The system consisted of a syringe pump feed, high temperature oven with preheat, densimeter and syringe pump receiver. The feed pump was run in constant flow mode while the receiver pump was run in constant pressure mode.With this apparatus, densities of water, methanol, or water+methanol mixtures were measured at supercritical conditions with an accuracy of 0.006g/cmィイD13ィエD1, which is fairly larger number than the resolution. The new densimeter along with the laser detection method eliminates magnets and extends the range of current vibration-type densimeters.