Background As early as 1920 it was known that Pennsylvania crude oils were better than the Gulf Coast (Texan) crude oils. Pennsylvania crude had the best viscosity temperature characteristics while the Gulf Coast crude had the worst since its viscosity varied much more with temperature. From the engineering viewpoint there was a need for a parameter which would accurately describe the viscosity-temperature characteristics of the oils. In 1929 a 'Viscosity Index' was developed by Dean and davis The reference oils have been selected in such a way that one of them has the viscosity index equal to zero (vi0)and the other has the viscosity index equal to one hundred (vl=100) at 100 F(37.8 C) but they both have the same viscosity as the oil of interest at 210 F(98.89 C). Since pennsylvania and gulf Coast oils have the same viscosity at 210 F(98.9 C they were initially selected as reference oils. Oils made from Pennsylvania crude were assigned the viscosity index of 100 whereas oils made from the gulf Coast crude the viscosity index of o
16 As early as 1920 it was known that Pennsylvania crude oils were better than the Gulf Coast (Texan) crude oils. Pennsylvania crude had the best viscosity temperature characteristics while the Gulf Coast crude had the worst since its viscosity varied much more with temperature. From the engineering viewpoint there was a need for a parameter which would accurately describe the viscosity-temperature characteristics of the oils. In 1929 a ‘Viscosity Index’ was developed by Dean and Davis. The reference oils have been selected in such a way that one of them has the viscosity index equal to zero (VI=0) and the other has the viscosity index equal to one hundred (VI=100) at 100°F (37.8°C) but they both have the same viscosity as the oil of interest at 210°F (98.89°C). Since Pennsylvania and Gulf Coast oils have the same viscosity at 210°F (98.9°C) they were initially selected as reference oils. Oils made from Pennsylvania crude were assigned the viscosity index of 100 whereas oils made from the Gulf Coast crude the viscosity index of 0. Background
H U 100VI 378 Temperature°C 989 Evaluation of viscosity index 润滑 17
润 滑 17 Evaluation of viscosity index
实际测定某润滑油的粘度指数时,只需测出其在40℃和100℃时的运 动粘度值,然后按照GBT199588(或 ASTMD2270查表计算该油的 粘度指数。 V<100时即U>)l L-U 100 L-H 润滑
18 实际测定某润滑油的粘度指数时，只需测出其在40℃和100 ℃时的运 动粘度值，然后按照GB/T 1995—88 (或ASTM D2270)查表计算该油的 粘度指数。 VI < 100时[即U＞H)]： 100 − − = L H L U VI 润 滑
>100时即U<H: 1≈10 +100 0.00715 其中:N= lg H-1gu gU H:高粘度标准油在40℃粘度表中查得;L:低粘度标准油在40℃粘度,表 中查得;U:试油在40℃时粘度,测得U:试油在100℃时粘度,测得。 润滑
19 VI ＞ 100时[即U＜H]： 100 0.00715 10 1 + − = N VI 其中： lg ' lg lg U H U N − = H:高粘度标准油在40℃粘度,表中查得；L:低粘度标准油在40 ℃ 粘度，表 中查得;U:试油在40 ℃时粘度，测得;U’:试油在100 ℃时粘度，测得。 润 滑
Example Find the viscosity index of an oil which has a kinematic viscosity at 40C of 140=135 mm2/s and at 100%C of 0100=17 mm2/s. From Table in GB/T 1995-88 for 1100=17 mm/s, L=369.4 and H= 180.2 can be found. Substituting into the viscosity index equation yields: VI=(3694-135)/(3694-180.2)×100=123.9
20 Find the viscosity index of an oil which has a kinematic viscosity at 40°C of υ40 = 135 mm2 /s and at 100°C of υ100 = 17 mm2 /s. From Table in GB/T 1995—88 for υ100 = 17 mm2 /s, L = 369.4 and H = 180.2 can be found. Substituting into the viscosity index equation yields: VI = (369.4 − 135) / (369.4 − 180.2)× 100 = 123.9 Example: