Measurement of cyclone separator

Transcription

1 Measurement of cyclone searator. Aim of the measurement Cyclones are widely used in industry (in food and chemical industry, in energy technology and in buildings) to remove dust and other articles from an air or gas stream. Aim of the measurement is to get acquainted with the exerimental test rig built in the laboratory of the Deartment of Hydrodynamic Systems and to determine the following characteristics of the cyclone: co =f (v ie ) Pressure dro in the unloaded cyclone as a function of air velocity, c =f (v ie ) Pressure dro in the cyclone as a function of air velocity during article transort, v t =f (R) Tangential velocity distribution along the radius. where, v ie means the average velocity at cyclone inlet.. General descrition of the test rig The sketch of the exerimental test rig is resented in Figure. The mixture enters the system at the feeder () and comes in the cyclone (3) through a ie. The ie is connected to the cyclone in tangential direction therefore a circular flow develos inside the cyclone. Behind the inlet the air flows in siral attern downwards along the wall of the cyclone. Larger articles in the circulatory stream have too much inertia to follow the tight curve of the flow so they strike the outside wall, where by friction they are broken and finally fall to the bottom of the cyclone. The transort medium (air) flows through the outlet ie towards the filter (5), where the fine dust fraction is searated. The air leaves the filter through the orifice (6), streams through the fan (), then through the butterfly valve (7) out to the environment. The flow-rate in the system can be set by the butterfly valve. 3. Technical data of the test rig Fan Tye: KNV 50 Production number: 4930

2 Driving electric motor for the feeder Tye: HZFP-63B-4DR/06- Production number: Manometer Tye: ROSENMÜLLER Production number: 4386 Orifice Diameter of the ie: D=80 [mm] Diameter of the orifice throat: d=50 [mm] 4. The measured and comuted quantities 4.. Pressure dro in the cyclone The ressure dro in the cyclone ( c ) will be determined by a U-tube manometer connected to the inlet and discharge of the cyclone. The ressure dro will be calculated from the deviation of manometer (h c ) in the following manner: h h h [m] c c cj víz cb g h [Pa] where h c [m]: total dislacement of water column in the manometer c [Pa]: ressure dro in the cyclone g [m/s ]: gravitational acceleration g=9,8m/s water [kg/m 3 ]: density of medium in the manometer water = 000 kg/m 3 c 4. Flow-rate measurement The flow rate will be measured by a flange ta orifice (the ratio of orifice throat diameter to the diameter of the ie is d / D 50 /80 0, 65 ). Measuring tube of the inclined micro manometer will be set vertically during the measurements both for unloaded oeration and transort. It means, that sin=. The ressure difference on the orifice can be calculated from the manometer reading l as follows: g l sin [Pa] alcohol

3 where [Pa]: ressure difference between ressure-tas alcohol [kg/m 3 ]: density of alcohol in manometer (9): alcohol = 800 kg/m 3 l [m]: liquid level in the manometer tube (9) [m]: angle between manometer tube and horizontal lane Flow-rate is roortional with the square root of ressure dro through the orifice: Q d 4 air where d [m]: orifice throat diameter α: orifice flow coefficient : exansion factor (, because of low ressure dro) air [kg/m 3 ]: air density (ustream of orifice for inlet ressure and temerature T ) we assume that T = T 0. T = 73 K air b = 760 mmhg = 0396 Pa =,93 kg/m 3 T T According to MSZ ISO 567- the orifice flow coefficient (α) is can be calculated as: C 4 where C is the discharge coefficient, which can be determined by the Stolz formula: C 0, , 03 The Reynolds-number above is: where D [m]: inner ie 8 Re. v D Re v [m/s]: fluid velocity through the ie [m /s]: kinematic viscosity of air 3

4 Alying the above written relations, the flow rate can be obtained in an iterative manner. First the air velocity (v ) will be aroached (say v = m/s), then the Reynolds number (Re), the discharge coefficient (C), and the orifice flow coefficient () will be calculated. Then a new velocity will be aroached as: v air d D This method has to be alied reeatedly until the relative error between consecutive velocities becomes less than %. As the velocity is given, the flow rate will be determined using the above written formula. Density and viscosity for actual ressure and temerature are: air T T and - absolute ressure in [Pa] T and T - temerature in [K] t - temerature in [C] = 3,3 0-6 m /s , t0 The ressure dro characteristic curves deend on the inlet velocity (v ie ). To obtain the inlet velocity, the flow rate through the orifice has to be reduced to the inlet ressure: where Q in Q in g hc Then the inlet velocity can be calculated by substituting D in =55mm. in v 0 ie water Qin D in 4 4

5 4. 3 Measurement of tangential velocity distribution in the cyclone The tangential velocity distribution in the cyclone will be measured by a three holes gauge. The central stagnation ressure-ta of the gauge will be connected to the ositive ort of an inclined micro manometer, while the twin ressure tas on both sides of the central hole are united and connected to the negative ta, so the ressure difference between the streamwise central hole and the slanted holes are measured. The butterfly valve will be fully oened. A constant flow rate will be set and the gauge will be ulled out by stes of 5 mm. The micromanometer dislacement has to be read for each gauge osition. Attention should be aid that the gauge is directed facing the flow. During the measurement micromanometer tube has to be set to ½ osition (sin=0.5). The deviation of the inclined micromanometer has to be corrected according to the Figure. The ressure difference and velocity can be calculated as written above using the corrected manometer deviation. The tangential velocity (v t ) can be calculated emloying the ressure difference ( dynamic [Pa]) measured by the PITOT-static tube as follows: dynamic air v t v t dynamic air 4. 4 Calculation of the ressure-dro on the filter The system contains a filter after the cyclone to catch the fine dust (which can not be searated by the cyclone) and to avoid it to get into the laboratory through the fan. A U-tube manometer is connected to the ressure-side and discharge of the filter, so the ressure-dro on the filter can be determined as follows: h filter h filter, left h filter, right filter water g h filter When this ressure difference exceeds a rescribed value, the filter has to be cleaned. 5. Starting of the equiment.the manometer will be set, the measuring liquid level must be set to zero.the discharge of the fan will be closed by the butterfly valve for minimizing the ower consumtion during start u 3.The fan will be started 5

6 6. The measurement 6. Measurement of characteristic curve of the cyclone for unloaded oeration and during dust transort. Different oerating oints will be set (0-5 measuring ositions have to be set in such an order, that equal ressure difference stes on the ROSENMÜLLER manometer (9 in Fig. ) can be read). The dislacement of U-tube and inclined micro manometer will be recorded for each butterfly valve setting 3. The average mass flow rate will be calculated in case of transort by measuring the mass of the dust and time during the oeration 4. The measurement will be evaluated 5. The resistance of cyclone will be drawn in function of inlet velocity co = f(v ie ) unloaded oeration c = f(v ie ) during transort 6. Measurement of velocity distribution. The gauge and manometer will be joined with miolan tubes. The manometer will be set to osition : for a better accuracy 3. The butterfly valve will be oened 4. The gauge will be set in streamwise direction 5. The gauge will be ositioned by ulling it out for in 5 mm stes, aying attention to the right streamwise direction 6. The dislacement of the ROSENMÜLLER manometer will be recorded for each gauge osition 7. The measurement will be evaluated 8. The tangential velocity distribution will be drawn as a function of the radius: v t = f(r) The below written geometric data can be alied for the reresentation: D c = 350 mm inner diameter of cylindrical art of the cyclone D u = 85 mm diameter of vertical discharge ie m= 3 mm distance between the late fixed to the gauge and the flange on the cyclone (R= 5.5 mm) (for details see Figure 3.) 6

7 7. Table of measurements Constants: b= mmhgo t 0 = C sin= water = 000 kg/m 3 alcohol = 800 kg/m 3 Measurement of unloaded oeration of the cyclone Cyclone Orifice Orifice Cyclone No. of meas. h cb [mm] h cj [mm] l [mm] h b [mm] h j [mm] h cb [mm] h cj [mm]

8 Measurement of article transort in cyclone Cyclone Orifice Orifice Cyclone No. of meas. h cb [mm] h cj [mm] l [mm] h b [mm] h j [mm] h cb [mm] h cj [mm] Constant data: b= mmhgo t 0 = C sin= water = 000 kg/m 3 alcohol = 800 kg/m 3 8

9 Measurement of ressure distribution No. of meas Disl. [mm] l [mm] Constant data: b= mmhgo t 0 = C sin= water = 000 kg/m 3 alcohol = 800 kg/m 3 9

10 8. Aendix Figure. 0

11 itot-static [Pa] calibration diagram 350 y = 0,89x gauge [Pa] Figure.

12 Figure 3.