CN1595473A - Self-circulating Reynolds experiment instrument with automatic color killing - Google Patents

Abstract

The invention relates to an autocycle Reynold laboratory apparatus with the automatic colour killing display liquid. It has the autocycle feedwater equipment, in which a water pump is installed. The water pump can be controlled by a silicon controlled continuous speed regulator. The constant pressure water tank is connected to the experimental pipes sequentially. There is a flow regulating valve equipped at the tail-end of the experimental pipes, below the export of which, an autocycle water recovery apparatus is installed. The constant pressure water tank is connected to the autocyle feedwater equipment through the upper water pipe and the lower water pipe. There are the overflow plate and the stilling water plate equipped in the constant pressure water tank. A stilling water hole is opened at the side of the stilling water plate. The constant pressure water pipe is divided into the overflow area, the constant pressure area and the stilling water area through the overflow plate and the stilling water plate. There is a container filled with the automatic color killing display liquid on the top of the water tank, beneath which a honeycomb duct with a flow guiding needle is equipped. The invention with easy operations solves the defect of the conventional Reynold laboratory apparatus, which is easy to be dyed by the display liquid and the water can't be reused.

Description

The self-loopa reynolds test instrument of automatic colour killing

Technical field

The present invention relates to the experimental measurement instrument, relate in particular to a kind of self-loopa reynolds test instrument that shows the automatic colour killing of liquid.

Background technology

Two kinds of fluidised forms of fluid have different kinetic characteristics.Laminar flow does not have the particle blending between fluid layer, particle is made orderly rectilinear motion; Turbulent flow is then opposite, and particle blending between fluid layer is unordered random motion.Specifically mobile is turbulent flow or nonturbulent flow (laminar flow), and available Re number is made criterion and differentiated.The existence of laminar flow, two kinds of fluidised forms of turbulent flow has clearly been demonstrated in reynolds experiment.Reynolds test instrument is the experimental apparatus that is specifically designed to reynolds experiment.

The Reynolds education experiment is one of important content of courses of fluid mechanics.Yet traditional reynolds test instrument exists certain drawback:: one, for a constant voltage water level is arranged, a relatively large water system and overflow system must be arranged, floor area is big; Its two, be subjected to vibration interference bigger, water body is difficult to reach stable for the moment; Its three, tracer reagent is serious to the dyeing of water body and experimental channel, water can not reuse first, water consumption is too big, moreover experiment is through water dyeing, surrounding environment is produced pollute.

Summary of the invention

The purpose of this invention is to provide a kind of self-loopa reynolds test instrument that shows liquid with automatic colour killing.

It has self-circulating water feeder, in self-circulating water feeder, be provided with water pump, water pump is controlled by the controllable silicon stepless speed adjusting gear, constant pressure water tank joins with experimental channel successively, the experimental channel afterbody is provided with flow control valve, the self-loopa water recovery apparatus is divided in the experimental channel outlet, constant pressure water tank is connected with downcomer by upper hose with self-circulating water feeder, be provided with overflow plate in the constant pressure water tank, the water-stabilizing board, water-stabilizing board's side direction has steady water hole, overflow plate and water-stabilizing board will be divided into overflow area in the constant pressure water tank, areas of permanent pressure and steady constant pressure water tank top, pool are provided with dress colour killing demonstration liquid container automatically, the demonstration liquid container is divided into the mozzle that has the water conservancy diversion syringe needle, mozzle end syringe needle is aimed at experimental channel inlet center, be equipped with in the said demonstration liquid container and be with automatic colour killing to show liquid, its composition is a phenolphthalein: NaOH=1: 2～3 proportionings, naoh concentration are 1/1000～1/2000.

Advantage of the present invention:

1) change the huge practice of structure in the past, its whole experimental system is dwindled simplification, easy and simple to handle directly perceived, and be suitable for the modern teaching requirement, also saved the experimental arrangement place simultaneously;

2) adopt new type auto colour killing tracer reagent to replace traditional tracer reagent, solved traditional reynolds test instrument equipment and be subject to tracer reagent dyeing, the not recycling defective of water body;

3) adopted independent self-loopa constant pressure water supply system, recycling experiment water body economizes on resources.

Description of drawings

Accompanying drawing is the self-loopa reynolds test instrument structural representation that shows liquid with automatic colour killing.

Embodiment

Automatically the self-loopa reynolds test instrument of colour killing has self-circulating water feeder 1, in self-circulating water feeder, be provided with water pump, water pump is by 3 controls of controllable silicon stepless speed adjusting gear, constant pressure water tank 4 joins with experimental channel 8 successively, experimental channel 8 afterbodys are provided with flow control valve 9, self-loopa water recovery apparatus 2 is divided in the experimental channel outlet, constant pressure water tank 4 is connected with downcomer by upper hose with self-circulating water feeder 1, be provided with overflow plate 7 in the constant pressure water tank 4, the water-stabilizing board 6, water-stabilizing board's 6 side direction have steady water hole, overflow plate 7 and water-stabilizing board 6 will be divided into overflow area 10 in the constant pressure water tank, areas of permanent pressure 11 and steady pool 12, constant pressure water tank 4 tops are provided with dress colour killing demonstration liquid container 5 automatically, demonstration liquid container 5 is divided into the mozzle that has water conservancy diversion syringe needle 13, mozzle end syringe needle is aimed at experimental channel 8 inlet centers, be equipped with in the said demonstration liquid container 5 and be with automatic colour killing to show liquid, its composition is a phenolphthalein: NaOH=1: 2～3 proportionings, naoh concentration are 1/1000～1/2000.

The course of work of the present invention is: under the constant voltage head, flow in the flow regulation valve regulation experimental channel, show that liquid (look water) flows in the experimental channel simultaneously, see through the interior formed streamline of liquid that shows of observation experiment pipeline and can determine water body laminar flow in the pipeline, two kinds of fluidised forms of turbulent flow.

Experiment of the present invention, the pipe Reynolds number, its computing formula is:

$\mathrm{Re}=\frac{\mathrm{\υd}}{v}=\frac{4Q}{\mathrm{\πdv}}=\mathrm{KQ}----\left(1\right)$

$K=\frac{4}{\mathrm{\πdv}}----\left(2\right)$

In the formula:

The Re--Reynolds number;

υ--rate of flow of fluid;

The v--fluid viscosity;

D--pipe diameter;

Overcurrent flow in the Q--pipe.

Experiment records flow Q in the experimental channel, experimental channel inner diameter d and experiment water temperature t, and fluid viscosity v tables look-up through water temperature t and obtains, and utilizes above 2 formula, but the Reynolds number of water body in the experiment with computing pipeline.

Automatic colour killing of the present invention shows that the principal ingredient of liquid is phenolphthalein and NaOH mixed solution, the characteristic of phenolphthalein solution for weak subtract and acid condition under be colourless, when solution alkalescence reached certain value, it is red that solution shows.The reagent course of work in the present invention is: phenolphthalein and NaOH are in phenolphthalein: NaOH=1: 2～3 ratios are measured respectively, phenolphthalein fully dissolves with anhydrous alcohol, the NaOH dissolved in distilled water, concentration is 1/1000～1/2000, after with two kinds of reagent mix, stir, it is red that reagent shows, and this is automatic colour killing and shows liquid.Show that liquid places in the demonstration liquid container,, advance with experiment water body associated movement by entering in the pipeline of mozzle syringe needle, can demonstrate fluidised form in the pipeline, be back in the self-circulating water feeder through water body behind the experimental channel, water body is in neutral state in the self-circulating water feeder, show the liquid caustic soda reduction, it is colourless that solution shows, both colour killing automatically, through working long hours, the experiment water body is alkalized, and it is red that water body shows, and adds an amount of watery hydrochloric acid in the water body, neutralization, water body gets final product colour killing.Show that liquid is pollution-free to water body, tube wall and surrounding environment.

Experiment content

(1) observes two kinds of fluidised forms.

Start water pump and supply water, make water tank be filled with water to overflow situation, after stable, open variable valve slightly, and inject color water in experimental channel, make the color current in line.The laminar flow state of the movement observation in-pipe flow by the color water particle, then, progressively drive big variable valve, the hydraulic characteristic that laminar flow changes to turbulent flow is observed in variation by color water straight line, after treating complete turbulent flow to occur in the pipe, progressively turn down variable valve again, can be observed the hydraulic characteristic that changes laminar flow by turbulent flow into.

(2) measure critical Reynolds number, reproduce reynolds experiment overall process then.

A. measure the lower critical Reynolds number

Open variable valve, make in the pipe turbulent fully, progressively close control valve for small flows again, only permitted in the adjustment process to turn down, mustn't drive big flow control valve, and behind flow of every adjusting (promptly turning down valve one time), need wait to stablize a period of time and observe its form again, until making the color current just in line, show promptly by turbulent flow just to transfer laminar flow to that can record lower critical Reynolds numerical value this moment is between 2000～2300.And Reynolds the time to draw the lower critical Reynolds number that the garden pipe flows in experiment be 2320, reason is that the lower critical Reynolds number is not to have nothing to do with interference is absolute yet, it is that interference at environment is minimum that Reynolds experimentizes, water body before testing in the water tank just draws through the careful measurement of repeated multiple times under long stable case.And a large amount of experiments of descendant are difficult to repeat to draw the accurate numerical value of reynolds experiment, usually between 2000～2300 owing to be subjected to the environmental interference factor affecting.Therefore, from the engineering practicality, the garden pipe lower critical Reynolds number of introducing in the textbook generally is 2000.If it is too little to record Reynolds number, should drives valve and to turbulent flow, remeasure again.

B. measure and go up critical Reynolds number

Open water pump, behind the water tank overflow, crack variable valve makes and occurs laminar flow in the pipe, drives big variable valve gradually, notes, is only permitted out mustn't close minor valve greatly, treats that the color current just scatter, and shows by laminar flow just to transfer turbulent flow to that the critical NR of going up is promptly arranged.According to measuring, last critical Reynolds number measured value is within 3000～5000 scopes, and with the speed of operation, the turbulent fluctuation degree of water tank, and extraneous interference etc. is closely related.Relevant scholar has done a large amount of tests, have 12000, have 20000, have in addition 40000.In the actual current, interference always exists, and is underrange so go up critical Reynolds number, no practical significance.

Achievement is analyzed

(1) the fluidised form criterion adopts dimensionless group, and does not adopt critical flow velocity.

In the experiment of Reynolds before 1883, discovery garden pipe flows and exists two kinds of fluidised forms---laminar flow and turbulent flow, and exists the critical flow velocity υ that laminar flow is converted into turbulent flow _c', υ _c' relevant with the diameter d of the viscosity v of fluid, garden pipe, promptly

υ _c′＝f(v，d)??????????????(3)

Therefore, in a broad sense, υ _c' can not be as the criterion of flowing state transition.

In order to differentiate fluidised form, Reynolds has been done a large amount of experiments to different tube diameters, different viscous liquid, has drawn with the criterion of dimensionless group (υ d/v) as pipe stream fluidised form.He has not only disclosed the rule of flowing state transition deeply, but also sets up the model with the research that experimentizes of the method for nondimensionalization for the descendant.Lei Liefa with non-dimension analysis can draw the dimensionless number that comes to the same thing with Reynolds number.

Can think that the funtcional relationship of formula (3) can represent with the product of index.Promptly

${\mathrm{\υ}}^{\′}=K{v}^{{\mathrm{\α}}_1}{d}^{{\mathrm{\α}}_2}----\left(4\right)$

Wherein K is a certain dimensionless factor.

The dimension relation of formula (4) is

$\left[{\mathrm{LT}}^{-1}\right]={\left[L^2{T}^{-1}\right]}^{{\mathrm{\α}}_1}{\left[L\right]}^{{\mathrm{\α}}_2}----\left(5\right)$

From the dimension harmony principle,

L：2α ₁+α ₂＝1

T：α ₁＝-1

Simultaneous solution gets: α ₁=1, α ₂=-1.

With The above results, substitution formula (4),

${\mathrm{\υ}}^{\′}=K\frac{v}{d}$ Or $K=\frac{{\mathrm{\υ}}^{\′}d}{v}----\left(6\right)$

Whether the mensuration of K value has been finished in reynolds experiment, and be the checking of constant.The result obtains K=2320.So dimensionless number υ d/v has just become to be suitable for any caliber.The criterion of the flowing state transition of any Newtonian fluid.Because the contribution of Reynolds, υ d/v names and is Reynolds number.

Perfect along with the dimensional analysis theory utilizes dimensional analysis to draw dimensionless group, study the relation between a plurality of physical quantitys, become one of important means of experimental study now.

(2) laminar flow and difference such as the following table of turbulent flow aspect kinematics characteristic and dynamics:

	Kinematics characteristic	Dynamics
			Laminar flow	1. particle is made laminar flow regularly.2. cross-sectional flow distributes parabolically.3. motion key element pulse free phenomenon.	1. there is not mass transport between fluid layer.2. there is not momentum-exchange between fluid layer.3. the energy loss of unit mass is directly proportional with the first power of flow velocity.
Turbulent flow	1. random motion is done in the mutual blending of particle.2. cross-sectional flow is pressed index law cloth.3. irregular pulsation phenomenon takes place in motion key element.	1. mass transport is arranged between fluid layer.2. there is momentum-exchange between fluid layer.3. the energy loss of unit mass becomes ratio with (1.75～2) power of flow velocity.

(3) physical significance of Reynolds number.

Reynolds number can be seen the ratio of liquid stream inertial force and viscous force as.Be appreciated that this point can analyze from the dimension of inertial force and viscous force.

Wherein volume W is a characteristic length

L cube, i.e. [W]=[L] ³Acceleration Dimension with recently the representing of the dimension of feature flow velocity and time, promptly $\left[\frac{\mathrm{d\υ}}{\mathrm{dt}}\right]=\frac{\left[\mathrm{\υ}\right]}{\left[t\right]}$ So the dimension of inertial force is

$\left[\mathrm{\ρ}\right]\left[W\right]\left[\frac{\mathrm{d\υ}}{\mathrm{dt}}\right]=\left[\mathrm{\ρ}\right]{\left[L\right]}^3\frac{\left[\mathrm{\υ}\right]}{\left[t\right]}$

Viscous force $T=\mathrm{\μ\ω}\frac{\mathrm{du}}{\mathrm{dn}},$ Wherein the dimension of area ω be characteristic length L square, i.e. [ω]=[L] ², current gradient Dimension available feature flow velocity and the expression recently of the dimension of characteristic length L, promptly $\left[\frac{\mathrm{du}}{\mathrm{dn}}\right]=\frac{\left[\mathrm{\υ}\right]}{\left[L\right]}$ So the dimension of viscous force is

$\left[\mathrm{\μ}\right]{\left[L\right]}^2\frac{\left[\mathrm{\υ}\right]}{\left[L\right]}=\left[\mathrm{\μ}\right]\left[L\right]\left[\mathrm{\υ}\right]$

The ratio of inertial force and viscous force dimension is

$=\frac{\left[\mathrm{\ρ}\right]\left[L\right]\left[L\right]}{\left[\mathrm{\μ}\right]\left[t\right]}=\frac{\left[\mathrm{\υ}\right]\left[L\right]}{\left[v\right]}$

The dimension of following formula is identical with the dimension of Reynolds number, and the characteristic length L in the formula represents with diameter d at Guan Liuzhong, then represents with the waterpower radius R in open channel.

By above analysis as can be known, Reynolds number can characterize the ratio of inertial force and viscous force.

Claims (1)

1, a kind of self-loopa reynolds test instrument that shows liquid with automatic colour killing, it is characterized in that it has self-circulating water feeder (1), in self-circulating water feeder, be provided with water pump, water pump is controlled by controllable silicon stepless speed adjusting gear (3), constant pressure water tank (4) joins with experimental channel (8) successively, experimental channel (8) afterbody is provided with flow control valve (9), self-loopa water recovery apparatus (2) is divided in the experimental channel outlet, constant pressure water tank (4) is connected with downcomer by upper hose with self-circulating water feeder (1), be provided with overflow plate (7) in the constant pressure water tank (4), water-stabilizing board (6), water-stabilizing board (6) side direction has steady water hole, overflow plate (7) and water-stabilizing board (6) will be divided into overflow area (10) in the constant pressure water tank, areas of permanent pressure (11) and steady pool (12), constant pressure water tank (4) top is provided with dress colour killing demonstration liquid container (5) automatically, demonstration liquid container (5) is divided into the mozzle that has water conservancy diversion syringe needle (13), mozzle end syringe needle is aimed at experimental channel (8) inlet center, be equipped with in the said demonstration liquid container (5) and be with automatic colour killing to show liquid, its composition is a phenolphthalein: NaOH=1: 2～3 proportionings, concentration sodium hydroxide are 1/1000～1/2000.

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