CN2783299Y - Hole mouth test device with moveable contact - Google Patents

Abstract

The utility model discloses a testing instrument with a moveable contact used for a pipe nozzle of an orifice. The utility model is provided with a self-circulation water feeder, wherein a water pump is arranged in the self-circulation water feeder; the water pump is controlled by a silicon controlled stepless speed regulator; the self-circulation water feeder is connected with a constant-pressure water tank and a water return tank; the constant-pressure water tank is provided with an overflow plate and a water stabilizing orifice plate; the constant-pressure water tank is connected with the self-circulation water feeder by a water feeding pipe and a water draining pipe; the constant-pressure water tank is provided with a pipe nozzle of an orifice, a switching plate, a scale and a pressure measuring pipe facing the wall surface of the water return tank; a water outlet of the water return tank is provided with a self-circulation water return device. The utility model adopts an independent self-circulation constant-pressure water supply system; therefore, the utility model is operated conveniently and visually and is suitable for modern teaching requirements; meanwhile, experimental layout sites are saved. A movable contact is skillfully arranged at the orifice mouth of a thin wall; the shrinking diameter of the jet flow of the orifice can be precisely measured by a vernier caliper; the precision reaches 0.01 mm. A device for measuring partial vacuum is arranged at a cylindrical pipe nozzle of a rectangular inlet. The utility model has the advantages of convenience and direct viewing performance.

Description

Aperture nozzle experiment device with mobile contact

Technical field

The utility model relates to the experimental measurement instrument, relates in particular to a kind of aperture nozzle experiment device with mobile contact.

Background technology

The flow phenomenon that fluid flows out through the aperture is orifice outflow, and it goes out the stream condition can be to decide going out under the head to go out stream under stream or the varying head, can be to flow in the air, also can be to flow in the fluid of same medium.The short tube that a length is about 3～4 times of orifice diameter is installed on the circumference in aperture, and such short tube claims the cylindrical outer tube mouth.Ozzle can be divided into by its shape: streamlined ozzle, cylindrical outer tube mouth, conical ozzle.Fluid this short tube of flowing through, and form full-section pipe-flow at the outlet section, this flow phenomenon is called vertical water outflowing jet.

The aperture ozzle is a kind of equipment that is used to measure flow, also is hydraulic facilities common on the engineering simultaneously.

Aperture ozzle education experiment is one of (the important teaching of fluid mechanics) content.Yet for a long time, there is certain drawback in traditional aperture ozzle experiment instrument on structural arrangement and teaching means: one, and traditional experiment instrument structure is numerous and jumbled, and huge tanks is arranged, bigger confession, backwater facility and weighing equipment, occupation of land is many like this, energy consumption big, complex structure; Its two, be to measure the side contracted diameter of aperture jet, people once used up scheming, did not but have a kind of high-precision short-cut method feasible all the time.

Summary of the invention

The purpose of this utility model provides a kind of aperture nozzle experiment device with mobile contact.

It has self-circulating water feeder, is provided with water pump in self-circulating water feeder, water pump is controlled by the controllable silicon stepless speed adjusting gear, self-circulating water feeder and constant pressure water tank, return flume join, be provided with overflow plate and water stabling aperture board in the constant pressure water tank, constant pressure water tank is connected with downcomer by upper hose with self-circulating water feeder,, constant pressure water tank is provided with aperture ozzle, switch boards, scale and piezometric tube towards the wall of return flume, and the return flume water delivering orifice is established the self-loopa water recovery apparatus.

Advantage of the present utility model:

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

2) between each aperture and ozzle, be provided with switch boards, can be under the full-water level state free handover measurement ozzle, and can therefore not cause spray splash phenomenon when cutting off or open;

3) be provided with movable contact fine at place, thin-walled aperture, utilize vernier caliper can accurately measure the contracted diameter of aperture jet, precision reaches 0.01mm, is provided with the device of measuring parital vacuum at right angle import cylinder ozzle place, and is easy, directly perceived.

Description of drawings

Accompanying drawing is the aperture nozzle experiment device with mobile contact structural representation.

Embodiment

Aperture nozzle experiment device with mobile contact has self-circulating water feeder 1, is provided with water pump in self-circulating water feeder, water pump is by 3 controls of controllable silicon stepless speed adjusting gear, self-circulating water feeder joins with constant pressure water tank 4, return flume 10, be provided with overflow plate 5 and water stabling aperture board 6 in the constant pressure water tank 4, constant pressure water tank 4 is connected with downcomer by upper hose with self-circulating water feeder 1, constant pressure water tank 4 is provided with aperture ozzle 7, switch boards 8, scale 11 and piezometric tube 12 towards the wall of return flume 10, and return flume 10 water delivering orifices are established the self-loopa water recovery apparatus.Aperture ozzle 7 is respectively loudspeaker inlet nipple, right angle inlet nipple, taper ozzle, aperture.

The course of work of the present utility model is:

Experimental principle

The relevant formula of aperture ozzle is when the constant voltage head issues living free discharge:

Flow rate calculation

Coefficient of flow $\mathrm{\μ}=\frac{Q}{A\sqrt{2g{H}_0}}---\left(2\right)$

Contraction coefficient $\mathrm{\ϵ}=\frac{A_c}{A}=\frac{d_c^2}{d^2}---\left(3\right)$

Efflux coefficient

Resistance coefficient

Experiment records the inflow-rate of water turbine of upstream constant voltage water level and each aperture, ozzle, utilizes above 5 formula, thereby draws aperture, ozzle each hydrodynamic contant under constant voltage, free discharge state of difformity section.

Experiment content

(1) the stream thigh form of observation aperture and each vertical water outflowing jet water column.

Open each aperture ozzle, make it go out stream, observe the stream thigh form of each aperture and ozzle current, shape difference because of various apertures, ozzle, it is also different to cross flow resistance, thereby has caused the stream thigh form of each aperture vertical water outflowing jet also different: fillet vertical water outflowing jet water column is smooth cylinder, and the right angle ozzle is cylindrical twisted shape distortion, the circular cone ozzle is smooth cylinder, and the aperture is then for having the smooth cylinder that side is shunk.

(2) observe orifice outflow in d/H＞0.1 o'clock with in d/H＜0.1 o'clock side shrink situation.

Open big flow, upper pond level is raise, make d/H＜0.1, measure necked-down section diameter d under the respective conditions _cClose low discharge again, the upstream head reduces, and makes d/H＞0.1, measures the necked-down section diameter d of this moment _c' value, can find d when d/H＞0.1 _c' increase, and approach aperture d, this is called incomplete contraction, and predicted by experiment this moment, and μ also increases, and can reach about 0.7.

(3) the parital vacuum degree at observation ozzle place, right angle.

Open right angle inlet nipple jet, promptly can observe, survey pipe place water column and reduce h rapidly _Very=(0.6～0.7) H ₀Illustrate that the right angle inlet nipple produces big vacuum in inflow point.But with empirical value 0.75H ₀Compare, vacuum tightness is less than normal, and its reason mainly is that the right angle import sharp-edged of pmma material is difficult to reach the intensity resemble the metal material.

Achievement is analyzed

(1) in conjunction with the stream thigh feature of observing dissimilar ozzles and orifice outflow, the approach of reason that the analysis stream coefficient of discharge is different and increase conveyance capacity.

With this chamber 2 ^#Aperture and certain experimental data of ozzle experiment instrument are example, and by experimental result as can be known, stream burst form and coefficient of flow are as follows:

The stream thigh of fillet vertical water outflowing jet is smooth cylindrical, μ=0.935;

The stream thigh of right angle vertical water outflowing jet is cylinder twisted shape distortion, μ=0.816;

The stream thigh of garden awl vertical water outflowing jet is smooth cylindrical, μ=0.934;

The stream thigh of orifice outflow has side to shrink near outlet, is smooth cylindrical, μ=0.611.

The reason that influences the coefficient of flow size has:

Near (α) stream strand diameter the outlet, the aperture is d _c=0.962cm, d=1.21cm, then d _c/ d=0.8, all the other are with the outlet internal diameter of ozzle, d _c/ d=1.

(b) the right angle inlet nipple goes out stream, and μ is greater than aperture μ _c, be because behind the former inducer owing to separate, stream burst side shunk and cause that (it is 16cmH that the parital vacuum degree is surveyed in this experiment to parital vacuum ₂O), thus producing swabbing action strengthens conveyance capacity.Latter's orifice outflow stream burst side is atmospheric pressure, and no suction force exists.

(c) the stream thigh of right angle inlet nipple is distortion, illustrates that horizontal rapid pulse is big, and the turbulent fluctuation degree is big, and this is because form the event of whirlpool near the side necked-down section.And the stream thigh of fillet inlet nipple is smooth cylindrical, and horizontal rapid pulse is faint, and this is because import is close to streamlined, is difficult for producing the event of whirlpool, so the right angle ozzle is bigger than the loss of fillet vertical water outflowing jet, the μ value is little.

(d) though the circular cone ozzle also belongs to the right angle import, because of inlet diameter is gradually little, is difficult for producing and separates, its side necked-down section area is near discharge area (the μ value is in discharge area), so side is shunk and the not obvious conveyance capacity that influences.In addition, from stream burst form, laterally pulsation is also not obvious, illustrates that reducer has stabilization (in engineering or the experiment, in order to improve the stability of active section current, often add a converging transition before active section, utilize this hydraulic performance of convergent just) to fluidised form.Energy loss is little, so its μ value is close with the fillet ozzle.

From above analysis as can be known, in order to strengthen the conveyance capacity of ozzle, entry shape should be made every effort to streamlinedization, as long as with the import cavetto, the effect that improves μ is just very remarkable.The experiment value of the coefficient of flow of aperture and right angle ozzle is bigger than normal than empirical value sometimes, its main cause also with manufacture craft on or import corner angle that use to go up because of carelessness aperture, ozzle worn and torn relevant.

(2) analyze the coefficient of flow μ that improves the sharp-edged thin-walled orifice outflow that shrinks _QFollowing relationship is arranged:

${\mathrm{\μ}}_Q=f(\frac{d}{H},\mathrm{Re},W_e)$

W wherein _eBe weber number.According to this relation, and in conjunction with the coefficient of flow deviation theory value (μ of other these experiments of factor analysis _Q=0.611) reason.

The thin-walled aperture improve under the pinch condition (aperture apart from the adjacent wall identity distance from L＞3d), the factor that influences orifice outflow flow velocity ν has: acting head H, aperture d, the density p of fluid, gravity acceleration g, coefficient of viscosity μ and surface tension coefficient σ, promptly

F(ν、d、H、ρ、g、μ、σ)＝0 (6)

Now utilize the correlationship between π rule analysis flow Q and each physical quantity, inquire into the hydraulic elements relevant then with coefficient of flow.

Because of ν, H, three dimensions of ρ physical quantity independently, have only:

[H]＝[L ¹T ⁰M ⁰]，

[ν]＝[L ¹T ^-1M ⁰]，

[ρ]＝[L ^-3T ⁰M ¹]。

Manage according to π

${\mathrm{\&pi;}}_1=\frac{d}{{\mathrm{\&upsi;}}^{a_1}{\mathrm{<figure-callout\; id="1"\; label="H\; b"\; filenames="Y20042003722000091.png"\; state="\{\{state\}\}">H</figure-callout>}}^{b_{}}{\mathrm{\&rho;}}^{c_1}}---\left(7\right)$

${\mathrm{\&pi;}}_2=\frac{g}{{\mathrm{\&upsi;}}^{a_2}{\mathrm{<figure-callout\; id="2"\; label="H\; b"\; filenames="Y20042003722000091.png"\; state="\{\{state\}\}">H</figure-callout>}}^{b_{}}{\mathrm{\&rho;}}^{c_2}}---\left(8\right)$

${\mathrm{\&pi;}}_3=\frac{\mathrm{\&mu;}}{{\mathrm{\&upsi;}}^{a_3}{\mathrm{<figure-callout\; id="3"\; label="H\; b"\; filenames="Y20042003722000091.png"\; state="\{\{state\}\}">H</figure-callout>}}^{b_{}}{\mathrm{\&rho;}}^{c_3}}---\left(9\right)$

${\mathrm{\&pi;}}_4=\frac{\mathrm{\&sigma;}}{{\mathrm{\&upsi;}}^{a_4}{\mathrm{<figure-callout\; id="4"\; label="H\; b"\; filenames="Y20042003722000091.png"\; state="\{\{state\}\}">H</figure-callout>}}^{b_{}}{\mathrm{\&rho;}}^{c_4}}---\left(10\right)$

According to the dimension harmony principle, the dimension of (7) formula should be

[L]＝[LT ^-1] ^a1[L] ^b1[ML ^-3] ^c1

So have

$\left.\begin{array}{c}L:1=a_1+b_1-3c_1\\ T:0=-a_1\\ M:0={\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="Y20042003722000091.png"\; state="\{\{state\}\}">c</figure-callout>}}_1\end{array}\right\}$

Can solve: a ₁=0, b ₁=1, c ₁=0.

Promptly

${\mathrm{\&pi;}}_1=\frac{d}{H}$

In like manner, try to achieve

${\mathrm{\&pi;}}_2=\frac{\mathrm{gH}}{{\mathrm{\&upsi;}}^2}$

${\mathrm{\&pi;}}_3=\frac{\mathrm{\&mu;}}{\mathrm{\&rho;\&upsi;H}}$

${\mathrm{\&pi;}}_4=\frac{\mathrm{\&sigma;}}{\mathrm{\&rho;H}{\mathrm{\&upsi;}}^2}$

With each π value substitution (6) formula, have

$F(\frac{d}{H},\frac{\mathrm{gH}}{{\mathrm{\&upsi;}}^2},\frac{\mathrm{\&mu;}}{\mathrm{\&rho;\&upsi;H}},\frac{\mathrm{\&sigma;}}{\mathrm{\&rho;H}{\mathrm{\&upsi;}}^2})=0$

Or $\mathrm{\&upsi;}=\sqrt{\mathrm{gH}}\&CenterDot;f_1(\frac{d}{H},\frac{\mathrm{\&mu;}/\mathrm{\&rho;}}{\mathrm{\&upsi;H}},\frac{\mathrm{\&sigma;}/\mathrm{\&rho;}}{{\mathrm{\&upsi;}}^{2}H})$

Again because of Q=A ν, then

$Q=\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="Y20042003722000091.png"\; state="\{\{state\}\}">A</figure-callout>}\sqrt{2\mathrm{gH}}\&CenterDot;f_2(\frac{d}{H},\frac{\mathrm{\&mu;}/\mathrm{\&rho;}}{\mathrm{\&upsi;H}},\frac{\mathrm{\&sigma;}/\mathrm{\&rho;}}{{\mathrm{\&upsi;}}^{2}H})$

Contrast flow rate calculation formula

$Q={\mathrm{\&mu;}}_{Q}A\sqrt{2\mathrm{gH}}$

Coefficient of flow μ then _QShould have

${\mathrm{\&mu;}}_Q=f(\frac{d}{H},\frac{\mathrm{\&mu;}/\mathrm{\&rho;}}{\mathrm{\&upsi;H}},\frac{\mathrm{\&sigma;}/\mathrm{\&rho;}}{{\mathrm{\&upsi;}}^{2}H})$

Or

${\mathrm{\&mu;}}_Q=f(\frac{d}{H},\mathrm{Re},W_e)$

Show that influencing coefficient of flow has three aspect factor.Now in conjunction with experimental result and existing analysis influence to this experimental result.

(a) $\frac{d}{H}<0.1$ The time, current shrink before and after the sharp-edged orifice fully,

To μ _QThere is not influence; Otherwise $\frac{d}{H}>0.1$ The time, shrink not exclusively μ _QIncrease.This experiment d/H=1.21/31.5=0.038＜0.1 is not so there is influence.

When (b) substituting H with characteristic length d, $\mathrm{Re}=\frac{\mathrm{\&upsi;d}}{v},$ When Re is very little, (routine Re＜10 ^4～5), because of the glutinousness influence, make μ _QReduce.This experiment Re ≈ 2 * 10 ⁴, show slightly influentially, make μ _QBe worth less than normal.

(c) W _e=ρ ν ²D/ σ (weber number) represents effect of surface tension.This has only when the aperture little, and stream is strand thin, flows when slow, and effect of surface tension can make μ _QReduce.This experiment d=1.21cm, capillary influence is very little, can omit.

According to above-mentioned analysis, actual measurement μ _QValue is less than normal than theoretical value, and explanation is reasonably, not so, may have other influence factors.As above the sharp-edged of problem (1) described " sharp-edged thin-walled aperture " is worn and torn, so μ _QValue will enlarge markedly.

Claims (2)

1, a kind of aperture nozzle experiment device with mobile contact, 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), self-circulating water feeder (1) and constant pressure water tank (4), return flume (10) joins, be provided with overflow plate (5) and water stabling aperture board (6) in the constant pressure water tank (4), constant pressure water tank (4) is connected with downcomer by upper hose with self-circulating water feeder (1), constant pressure water tank (4) is provided with aperture ozzle (7) towards the wall of return flume (10), switch boards (8), scale (11) and piezometric tube (12), return flume (10) water delivering orifice is established self-loopa water recovery apparatus (2).

2,, it is characterized in that said aperture ozzle (7) is respectively loudspeaker inlet nipple, right angle inlet nipple, taper ozzle, aperture according to the described a kind of aperture nozzle experiment device with mobile contact of claim 1.

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