DE593024C - Method and device for the continuous display of the viscosity of fluids, e.g. B. of lubricating oils - Google Patents

Description

in the.

18 ME?., 1934

ISSUED FEBRUARY 23, 1934

The invention seeks to solve the problem of the lubricity of oils and others To continuously monitor and measure liquids during operation. Namely in motor vehicles, but also generally in all types of prime movers and machines, it is of great importance to read the degree of viscosity on a measuring instrument at any time and then to be able to assess whether ίο the lubricant in the company still meets the requirements of the machine or whether the liquid improves by refilling or has to be replaced with new fluid. The profitability of the company is thereby significantly increased and useless material consumption, material wear and tear or even material destruction is avoided.

It is known that one can measure the viscosity of a liquid by pushes them through a narrow nozzle or capillary tube at a constant speed and measures the pressure in front of the capillary, which is directly proportional to the viscosity. It it has already been proposed to increase the viscosity of a liquid by this method measure that the liquid is poured into a container and then through a plunger 0. Like. Pushes through the outlet nozzle at a constant speed. A continuous measurement of the viscosity is not possible with this device.

The present invention now provides a continuous display that is per se in the Viscosity determination is not new, even for the method of viscosity determination described above in a very simple way and the influence of the specific gravity of the examined liquid largely switched off on the accuracy of the measurement. To of the invention, the pressure difference is used to maintain the flow velocity

between - the pressure in the line before the

Constriction and the total pressure in the constriction measured or obtained equal if »: i the ratio of the total friction in the constriction to the partial friction up to the measuring point in the constriction is.

It is known per se, the flow rate of liquids or gases by maintaining the difference in the pressures in front of and in a narrowing of the line regulate by measuring the pressure at one measuring point on the top and the pressure at the Another measuring point can act on the underside of a piston, depending on the size the pressure difference a valve to maintain the pressure flow rate more or less closes. However, the known devices in question are not for viscous liquids can be used because with viscous liquids significant sources of error occur due to the frictional pressures caused by the viscosity.

As will be shown below, such sources of error are in accordance with the present invention avoided and the flow velocity

constant regardless of toughness.

Let us now derive the equation from Fig. Ι of the drawing, from which it follows that the flow velocity of the liquid is directly related to the pressure difference between a fraction of the pressure in the line a before the constriction b and the entire pressure in the constriction b is proportional. For ίο simplification it is assumed for the time being,

■ that the definite part - the pressure P just

the value - own. According to Fig. Ι now flow

a liquid through a conduit of varying cross-section. The line has measuring points 1, 2 and 3. The cross-sections at measuring points 1 and 3 are the same, i.e. F ₁ = F ₃ . Then the flow velocities at the measuring points 1 and 3 are also equal to one another, i.e. D ₁ = V ₃ . The measuring point 2 is arranged on the narrowed line part &. According to the so-called continuity equation, the speed at measuring point is 2

ν., - ν-.

F ₁ F., *

(i)

If the fluid is smooth, then applies to the prints

P ₃ = P ₁ or P ₁ - P ₁ = ο. (2) According to Toricelli, the pressure difference is

^P i - ^P * = ^Z -S- (ν-ϊ— wf) = 2 · £ --—— ² - · v \. (3)

In this formula, g means the specific weight of the liquid.

If the liquid is viscous, it changes due to the friction that arises Pressure drop equations (2) and (3). It will then

and

P ₁ -P., =

-ZVC ₁ ,., (4)

-O ₁ ⁸ ) + XT-W ₁ -C _1-2 . (5)

In these formulas, ζ denotes the absolute viscosity of the liquid, C ₁₁₂ or C ₁₃ constants for line sections ι to 2 or ι to 3 (in the case of eddy-free flow), which are dependent on the shape of the respective line sections.

If the same friction is provided in the line pieces ι to 2 or 2 to 3, so can be set ί

If one takes this equation (6) into account in equations (4) and (5) and then sets the Equation (4) into equation (5) results in

Since the line part c, which is the measuring point. 3 contains, is located at the end of the line, so is

■ P ₁ = O. (8)

This value, inserted into equation (4), gives

F ₁ -2-W ₁ -Oj,.,. (9Y

Furthermore, by substituting equation (8) into equation (7):

η - O \ - XI O 77— "* * '

From this equation (10) it is clear that the pressure difference - ~ P _{2 is} no longer

depends on the viscosity, but only on the flow velocity. It follows without further ado that the flow velocity remains the same,

if the pressure difference - P., same value

retains.

As will be described below, the pressure difference - ~ ■ - ■ P ₂ must be kept constant in order to keep the flow velocity constant.

Measurement of the pressure difference —_- · - P ₂

is d by two connected at the measuring points 1 and 2, piston or membrane and reaches e, f a surface area _t or / "" own. and a about the fulcrum g pivotable double-armed lever Ii in a particular spot to be explained lever ratio I ₁ : I _2. If one chooses the size of the membrane cross-sections f _x and f ₂ as well as the effective lever arms I ₁ and I ₂ in such a ratio to one another that

fi'h = - f * 'h («)

is, the torque exerted on the lever h in the direction of the arrow i is proportional to the pressure difference --— - P ₂ , as

readily results when you look into the torque

the equation (11) is inserted. So it is Ί · fi-h - P »' / 2 · h proport. - ¹ - P ₂ . (13)

From equation (13) it follows that the

The torque exerted on the lever h in the direction of the arrow i becomes greater the greater

the pressure difference becomes - ± P ₂ , and by-

swept. The deflection at the end of the lever h is therefore always directly proportional to the increase and decrease of this pressure difference.

This dependence of the deflection at the end of the lever h on the mentioned pressure difference

ίο is used according to the invention to maintain the flow velocity. For this purpose, as shown in Fig. 2, a closing element k located in the line part α is connected to the lever h by means of a link in the or the like in such a way that the closing element increases the flow cross-section as the pressure difference ρ increases

- ^ - - P ₂ decreased and increased with decreasing pressure difference. The closing element k is built in such a way that it overcompensates; ie the changes in the flow cross-section upwards or downwards are so great that the pressure difference is always kept constant at a mean value. According to equation (10), however, this maintenance of the pressure difference also means the maintenance of the flow velocity in the line part a. In the device described, the viscosity is measured in a simple manner by a manometer η which is calibrated according to viscosity units and is connected shortly before the constriction b in the line part α. Since, according to equation (9), P ₁ = ζ -V ₁ - C _L3 , when the flow velocity is maintained equal as described above, V ₁

P ₁ = proport. ζ.

(14)

With the measurement of the pressure P ₁ by the manometer η at the measuring point i in the line part α, one has a direct measure of the viscosity.

A spring 0 arranged on the lever h serves as a valve spring to dampen the vibrations that occur.

While in Fig. 2 the pistons or diaphragms d and e are arranged side by side on the lower side of the line, one of these measuring points can also, as can be seen from Fig. 3, be arranged above and the other below. In Fig. 3, the membrane ^ is attached immediately next to the connection point of the pressure gauge η , while the membrane e is below and is connected to the constriction b . With such an arrangement, the two membranes a and e do not interfere in their position; they can be made as large as required, just as equation (11) requires. The pivot point g of the lever Ä lies in this case on the right side of the whole

Device, and the pressures -_-'- ■ and P ₂ act in opposite directions. This results in the same torque as in Fig. 2.

The above formulas were derived on the assumption that the same friction in line sections ι to 2 and 2 to 3, respectively is available. However, if you generally

the friction in the line piece 1 to 2 - the

Total friction in the line piece can be 1 to 3, so equation (6) reads in general

C ₁₃ = Ii-C ₁ ... (6a)

Taking this general equation (6a) into account, we then obtain on the basis of Calculations which completely correspond to the calculations given above, that —- ■ P,

is independent of viscosity and is a pure function of speed. So you can Maintaining the same flow velocity by maintaining the same pressure difference

P 0-

between a certain part of the print

Achieve kes P ₁ in the line before the constriction b and the entire pressure P ₂ in the constriction δ. Here, η means the ratio of the total friction in the line section 1 to 3 to the partial friction in the line section 1 to 2.

Claims (2)

Patent claims: 1. Method for the continuous display of the viscosity of liquids, e.g. B. of lubricating oils, by measuring the pressure upstream of a line section, in particular a capillary, through which the liquid flow is passed at constant speed, characterized in that for the purpose of maintaining the flow speed the pressure difference! - P ₂ ) between the pressure \ η ² J η kes (P ₁ ) in the line before the constriction (δ) and the total pressure (P ₂ ) in the constriction is measured or obtained equal if 11: 1 is the ratio of the total friction in the constriction (in the line part 1 to 3 ) for partial friction up to the measuring point in the constriction (in the line part 1 to 2). 2. Device for carrying out the method according to claim 1, characterized in that that the measurement of the pressure difference (- P ₂ ) is achieved by two pistons or membranes (d, e ) connected to the relevant line points (a, b) , which act on a double-armed lever (Ji) in such a lever ratio (I ₁ : L) , that the torque exerted on the lever is proportional to the said pressure difference will. 3, device according to claim 2, characterized in that a closure member (k) moved by the double-armed lever (A) reduces the flow opening as the pressure difference increases, and vice versa, PJ π η and thereby the flow velocity is kept the same. 1 sheet of drawings