一个独特的高温,高剪切粘度计的研制

一个独特的高温,高剪切粘度计的研制

Introduction

Engine lubricant viscosity is an essential property that affects fuel economy. Viscosity is a crucial parameter to measure for oil analysis due to the importance of oil conditioning and lubrication [1]. Viscosity enables machines to operate at various temperature conditions. In general, viscosity tends to decrease with increased temperature and vice versa which explains why lubricant oils flow smoother in summer than they do in winter. Therefore, it is important to specify the grade of lubricant oil for proper usage.

图1. SAE J300机油粘度表[3]

主要发动机润滑油是由汽车工程师学会(SAE)的粘度分级系统协会分类为如图1所示。这些粘度等级确定哪个特定的发动机润滑油适合于不同的发动机。现代发动机润滑油是多级品级,必须符合粘度为低和高的温度。的5W SAE粘度等级是指在低温下的粘度变薄的润滑油,并把它在启动过程中其增强的发动机保护,并同时流动更快降低长期佩戴[4]。30 SAE粘度等级是指在100℃的高温下另一个粘度规格。它也有一个较低的数量,其对应于较薄的油。

粘度主要是定义为两个方面:运动粘度和绝对(或动态)粘度[5,6]。油的运动粘度被定义为在重力的作用下所述电阻流量和为流体的固有电阻的测量当没有施加外力流动。[6]。在另一方面,动态粘度被定义为流体的电阻当施加外力流动。此外,流体罐的密度直接影响的运动粘度的值,而在动态粘度它不[6]。

除两个主要的粘度,高温,高剪切(HTHS)粘度直接影响操作发动机的燃料效率和耐久性。它是例如活塞环和衬里,和齿轮的接触点[3]用于有效地测量充分加热的油的在150℃的温度的能力的一些方法中,快速移动的发动机部件的窄开口之间的一个。随着HTHS的增加,发动机部件加强了保护价值。为了确定用于环和轴承的油的润滑质量,HTHS性能测试是根据SAE的要求[7]意在302℉(150℃)。

大多数现代石油润滑剂的配制与添加剂用于各种目的,例如控制油的氧化,减少磨损/擦伤,并防止腐蚀从摩擦和酸[8]。既然是固有的是粘度容易受到温度的影响,产业一直在尝试使用适当的添加剂,以产生润滑油,其从副歌温度变化下的粘度损失。这些添加剂是粘度指数改进剂,也被称为粘度调节剂,其主要是油溶性的聚合物和共聚物[9]。小,线圈状的聚合物分子展开并膨胀随着温度的升高,产生了较高的粘度相比精油。有益的是增加摩擦的液体,以补偿粘度的降低所造成的更高的温度[9]。粘度指数是无量纲数,表示与温度成比例增加[7]的粘度损失的量。

Figure 2. Viscosity Index – schematic [9]

The VI scale consists of high and low limit points. The high VI-oils is more desirable because it has minimal viscosity changes with respect to changes in temperature [9]. While many lubricant oils contain additives that are not heavily affected by the change in temperature, these formulated lubricant oils are commonly non-Newtonian, which has viscosities that vary with shear rate and shear stress [8]. At low temperatures, the lubricant oils demonstrate Newtonian behavior which retains constant viscosity. However, viscosity decreases as the shear rate climbs to critical value.

的润滑油被暴露于极端条件同时具有高剪切速率和温度范围从105至107秒-1和100〜170℃,分别[8]。HTHS实验模拟这些真实的操作条件,以获得润滑油的准确粘度测量。两种最常见的粘度测量是旋转和毛细管粘度计类型。本文将讨论的高温,高剪切实验的毛细管粘度计。这是简单的构造和操作,并且具有较少的苛刻的温度控制的要求[8]。的毛细管粘度计需要具有精确规定的尺寸,如内直径和长度的毛细管。的时间将用于液体通过毛细管的流动进行测量。

The capillary viscometer has been designed for measuring the viscosity of the lubricant oils at a given temperature of 150℃ and 106 sec-1 shear rate which meets the specification of SAE viscosity classification J300. The portable computer embedded in the HTHS viscometer offers automatic calculations for viscosity and shear rate [12]. The capillary viscometer is rudimentary in obtaining data for pressure versus flow rate and provides a better understanding of the disturbances in the capillary tube caused by a pressure drop. It is found in literature that excess pressure drops were larger for non-Newtonian fluids compared to Newtonian fluids as both have a similar viscosity [8,14-16].

Measuring viscosity at high temperature high shear, the capillary viscometer is operated complying to ASTM method (D5481). This test method achieves the viscosity of engine oils through a single apparatus at a fixed temperature and single shear rate. It suggests an appropriate shear rate of 1.4*106 s-1 at the wall which leads to diminution in discrepancy between this test method [13]. It is required to make calibrations with Newtonian oils with viscosities from 2 to 5 mPa-s at 150℃ to determine the viscosity of a sample oil [13]. The calibration must be done with at least four different standard oils and the sample is pressurized under direct contact with the driving gas, Nitrogen. [11,13].

将样品通过其连接到粘度计电池的优异一部分的10ml注射器引入。样品流过所述毛细管自由使用重力和达到对于其中它达到平衡温度15分钟粘度计电池的填充管内的底部。电池内部的样品的体积被精确地通过施加压力之前吸出样品回注射器中的量来调节。有人建议,最好是在运行测试之前的调整压力。当“运行”开关被启动时,电磁阀同时从关闭大气出并打开加压气体流入的粘性细胞[12]。的毛细管粘度计测量的流动时间到0.01秒与自动内置数字计时器。当气体开始流入细胞,计时器自动启动,将样品从细胞[8]移动后停止。流动时间,压力和温度被显示在便携式计算机的屏幕上。通常,流动时间从20到30秒的范围内,在100〜500 psig的[12]的压力。所记录的流的时间和压力来计算在106个S-1样品的粘度和剪切速率。

Table 1. Known values for Calibration

HTHS实验操作之前,calibrations were performed using Newtonian standard oils. According to the ASTM method (D5481), a specific temperature is required to reach the targeted viscosity for each standard oil as shown in Table 1. The density of the standard oil is used to get the volume of the oil and corresponding flow time after completing the calibration test. The calibration is performed at least three times to get the average volume of each standard oil. When three sets of valid data are input in the calculation interface of the portable computer, the apparatus automatically saves the records and calculates the specified flow time using the average volume. Thereafter, calibration constant calculation is proceeded for each standard oil for at least three times as well. This calibration calculation measures the viscosity of the standard oil with the valid pressure and flow time.

Table 2. Measured viscosity and average value of viscosity of each standard oil

每个标准石油公司一直在不同的粘度ned as shown in Table 2. The three measured viscosities are averaged to a final viscosity that has a slight discrepancy from the known viscosities in Table 1. Errors between the known viscosity and the measured average viscosity are 1.596%, 0.882%, 0.450%, and 1.382%, respectively. These errors might have contributed to the collection of the standard oil from the outlet and oil weight measurements. Bursting is generated at the end of displacing the oil from the cell, which leads to losing some amount of the oil as seceding from a beaker placed under the outlet of the apparatus. In addition, the oil must be collected until the oil mist is completely gone by repeatedly clicking the start and stop button. This step relies on human judgment which may contribute to the inaccuracies. Furthermore, systematic error occurs while the collected oil is measured with a weight scale since it is not stabilized on reading the scale.

Through the HTHS experiment following ASTM test method D5481, the capillary viscometer is a very useful and simple way to measure the viscosity of the lubricant oil. Identifying the proper HTHS viscosity of lubricant oils is of paramount importance in the industry for determining suitable motor engines. The lubricant oils are categorized into lower HTHS viscosity and higher HTHS viscosity. Each classification has its own advantages. The lubrication oils with lower HTHS viscosity provides better fuel economy to the industry and lower greenhouse gas emission. The high HTHS viscosity accomplishes better wear protection for the engine. The most important facet for industries to focus on is finding the appropriate balance between fuel economy and engine protection for the formulation of lubricant oils.

参考

[1]“油粘度 - 它是如何测量和报告。”机械润滑,诺娅公司,https://www.machinerylubrication.com/Read/411/oil-viscosity
[2]“一个油的粘度的重要性。”机械润滑,诺娅公司,https://www.machinerylubrication.com/Read/29185/oil-viscosity-importance
[3] Mesmaeker,大卫D.“A低的HTHS粘度的挑战。”Q8油,科威特石油公司,2017年6月1日,https://www.q8oils.com/automotive/low-viscosity-challenges
[4] “MULTI GRADE CAR ENGINE OILS EXPLAINED.” OPIE OILS.CO.UK, Opie Oils, TecAlliance, https://www.opieoils.co.uk/t-multi-grade-car-engine-oils-explained.aspx
[5]“粘度V级HTHS粘度:?有什么不同,为什么它很重要”路博润添加剂360,路博润公司,2019 4月14日,https://www.lubrizoladditives360.com/viscosity-grade-v-hths-viscosity-whats-the-difference-and-why-is-it-important/
[6] Ranowsky, Amanda. “What is the Difference Between Dynamic and Kinematic Viscosity?” CSC Scientific Blog, CSC Scientific Company, Inc., 15 Jan 2015, https://www.cscscientific.com/csc-scientific-blog/whats-the-difference-between-dynamic-and-kinematic-viscosity
[7]“油粘度”。ZPlusTM的简介#13,ZPlus有限责任公司,2009年6月29日,https://zddplus.com/wp-content/uploads/2017/05/TechBrief13-Oil-Viscosity.pdf
[8] Palekar, Vivek M. Development of A High Shear Capillary Viscometer. The Pennsylvania State University The Graduate School Department of Chemical Engineering, 1993.
[9] “Viscosity index.” Anton Paar, Anton Paar GmbH, https://wiki.anton-paar.com/en/viscosity-index/
[10] Fitch, Jim. “Don’t Ignore Viscosity Index When Selecting a Lubricant.” Machinery Lubrication, Noria Corporation, https://www.machinerylubrication.com/Read/28956/lubricant-viscosity-index
[11]“如何测量粘度。”安东帕,安东帕有限公司,https://wiki.anton-paar.com/en/how-to-measure-viscosity/
[12] Balasubramaniam,瓦苏德万。高剪切流变多级润滑油。化学工程,1992年的美国宾夕法尼亚州立大学的研究生院部。
[13] ASTM D 5481-10, Standard Test Method for Measuring Apparent Viscosity at High-Temperature and High-Shear Rate by Multicell Capillary Viscometer, ASTM International, West Conshohocken, PA, 2010, www.astm.org
[14] Duda, J.L. and Vrentas, J. S., Trans. Soc. Rheo. 17, 89 (1973).
[15] Kim-E., M. E., Brown, R. A. and Armstrong, R. C., J. Non-New. Fluid Mech. 13, 241 (1983).
[16] Sylvester, N. D. and Rosen, S. L., AIChE J. 16, 967 (1970).

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