Rotor Design Research Papers

Effect Of Different Configurations Of Mechanical Aerators On Oxygen Transfer And Aeration Efficiency With Respect To Power Consumption

by Samir Deshmukh

2022

This paper examines the use of mechanical aerator for oxidation-ditch process. The rotor, which controls the aeration, is the main component of the aeration process. Therefore, the objective of this study is to find out the variations in... more

Fig. 1 Variation of over all Oxygen Transfer Coefficient Kya with aerator Speed for different aerators It is quite evident from figure that the K,a values obtained with CBR aerator at speed ranging from 36 to 60 rpm, are much higher than that of other three aerators. Therefore CBR emerges as a potential aerator out of the other three configurations for any given speed.

Fig. 2 Variation of Dissolve Oxygen (mg/L) with Time for Different Depth of immersion for CBR Aerator Figure (2) shows the variation of increase in D.O concentration against time for CBR aerator. It can be easily identified that the maximum D.O concentration value of 8.2 mg/L can only be achieved by maintaining the 5.5 cm depth of immersion. Further increase or decrease in depth of immersion decreases the D.O concentration.

Figure (3) is a plot of depth of immersion with K,a and power, which signifies that with increase in depth of immersion, there is marginal rise in K,a value, but on other hand it suggests that with increase in depth of immersion the power consumption rises sharply, which is obvious because at larger depths the aerator is required to handle large water volume. Fig. 3 Influence of Depth of Immersion on Overall Oxygen Transfer Coefficient & Power (W)

Fig. 4 Variation of Dissolve Oxygen with Time for different Aerators at speed 36 RPM and 5.5 Depth of Immersion Effect of time of aeration on the dissolved oxygen level with different aerator configurations and at different speeds have been studied from figures (4),(5),(6) and (7). The depth of immersion is kept constant at 5.5 cm for all aerators. In figure (4), the variation of DO with Time for all the aerators at 36 rpm is shown.

Figure (6) shows that at 48 rpm the dissolved oxygen saturation concentration value of 8.2 mg/L is achieved in 30 min, where as there is no apparent improvement in the saturation values of CRWR and CFR. Fig. 6 Variation of Dissolve Oxygen with Time for different Aerators at speed 48 RPM and 5.5 Depth of Immersion

Fig. 5 Variation of Dissolve Oxygen with Time for different Aerators at speed 42 RPM and 5.5 Depth of Immersion Similar trend is observed with figures (8),(9) and(10) which are plotted for speeds 42, 48 and 60 rpm respectively.

Fig. 7 Variation of Dissolve Oxygen with Time for different Aerators at speed 60 RPM and 5.5 Depth of Immersion Figure (7), illustrates that the CBR aerator again reaches the value of 8.2 mg/L in 30 min at speed of 60 rpm. CRWR, CFR and Brush aerator attains 80% to 90% of saturation concentration value but time required is higher than 45 min. Therefore it can be seen that as the speed increases the time required reaching the maximum dissolved oxygen saturation concentration value decreases. In other words with increase in speed less time is required to attain maximum value of dissolved oxygen saturation concentration.

Fig. 8 Variation of K,a(h) & Aeration Efficiency(kgO,/kWh) with Rotor Type & Speed of aerator (RPM) Variation of AE and K,a for different blade tip angles and speed:

Fig. 9 Variation of K,a(h"') & Aeration Efficiency (kgO,/kWh) For different blade angles & Speed of aerator(rpm) Three configurations were developed by changing the blade tip angles (27°, 47° and 60°) and their performance was evaluated for K,a and AE with respect to speed. Each configuration was tested for the aerator speed of 42, 48 and 60 rpm and the plot was obtained. From figure (9) it is observed that at 48 rpm and 47° blade tip angle the optimum value of K,a is observed to be 10.33 h' for which the CBR aerator recorded the highest value of AE, which is to the tune of 2.269 kgO./kWh. This is because of the AE is mainly dependent on power and as stated earlier the power required increases with increase in speed and depth of immersion. From figure it can be seen that even though the values of K,a at 60 rpm and for blade tip angles of 27°, 47° and 60° are more than that of 48

Fig. 10 Effect of Speed on Aeration efficiency for CBR aerator at depth of immersion of 5.5 cm

Fig. 12 Relationship between Observed power values (W) & Calculated power values (W) Fig. 11 Relationship between Observed Overall Transfer coefficient (K,a) & Calculated Overall Transfer coefficient (K;a).

It has been estimated that the simulation equation (1) and (2) predict the values of K,a and power with an average standard error of estimation of 0.0164 and 7.66 respectively and with R? values of 0.979 and 0.989 respectively, when compared with experimentally determined values. Thus equations (1) and (2) are justifiable by taking into consideration all of the experimental errors themselves. Therefore above equations may be used with confidence for predicting the Kya and power (P) and can be considered as design equations for CBR aerator.

Ky .@ VALUES OBTAINED FOR DIFFERENT SPEEDS FOR VARIOUS CONFIGURATIONS OF AERATORS tatiana © laa wii” Satie * itis Plot for variation of Kya with speed for all configurations of aerator is represented in figure (1). TABLE I

PERFORMANCE OF CBR AERATORS W.R.T. Kya , POWER AND A.E. FOR DIFFERENT BLADE ANGLES AND SPEEDS TABLE-II

MAXIMUM AERATION EFFICIENCY FOR TYPICAL AERATORS.[13]

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Drainage of a Water Tank with Pipe Outlet Loaded by a Passive Rotor

by Mohamed Elgamal

2022, Water

The optimal design of pipe outlets is an essential objective for many engineering projects. For the first time, this paper reports the results of a laboratory investigation on the effect of using a passive rotor (added at the pipe outlet)... more

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Design and Mechanism Analysis of Paddlewheel Aerator with Movable Blades

by Samsul Bahri

2021, IOP Conference Series: Materials Science and Engineering

The successful of intensive aquaculture is strongly influenced by the ability of the farmers to overcome the deterioration of water quality. The problem is low dissolved oxygen through aeration process. The aerator device which widely... more

Figure 1. Paddlwheel aeator based of Taiwan design Various models of paddle wheel aerator are offered in market. Aerator based on Taiwan design is widel} used by consumers due to affordable price, light in weight and corrosion-resistant but has low efficiency as shown Figure 1 [1][5]. Aerator that was designed and fabricated by Taiwan has SAE (standar« aeration efficiency) value of 1.063 kg O2 kW h" [6]. Bhuyar et al. designed aerator with SAE value 2.269 kg Or kWh’ [7]. The most appropriate paddle wheel aerator was designed by Moore and Boyc with SAE value 2.54 kg O2 kWh''. Some of fabrications use aerator design with specification 2.25-7.: kW and SOTR 17.4- 23.2 kg O2 h" and average value of SAE was 2.2 kg O2 kW h' [8].

Figure 2. Torque measurement scheme 2.2.2. Power measurement. Paddlewheel power measurement was done by measuring the electrical power consumption of electric motors using Ammeter (DO2A) which was connected to an electrical outlet. Reading the power measurement value (Watt) was done by using a digital video camera recording on display Ammeter. Rated power was taken on the average value that often was showed from the reading video playback recording for each treatment testing.

Figure 3. Wheel structure with movable blade The wheel structure consisted of two main components i.e.stationary and rotary component as shown it Figure 3.

The maximum displacement of follower for one rotation 50 mm with angle of rotation 125° is shown in Figure 5. The maximum velocity of follower was 45.84 m/s as shown in Figure 6.

The constant acceleration was 6.09 m/s” as shown in Figure 7.

3.2.2. Angle of pressure. Angle of pressure determines the smoothness of cam movement. The analysis of angle of pressure was illustrated in Figure 3. Angle of pressure (@) for every angular position was equated as follows: IOP Conf. Series: Materials Science and Engineering 532 (2019) 012011 doi:10.1088/1757-899X/532/1/012011

Based on the calculation, some of spring data were collected, including installed length, operating length, operating force, springs material, wire diameter, average diameter, inside diameter, outside diameter, free length, number of coils and allowable shear stress for blade-opening springs. The magnitude was 75 mm, 25 mm, 2.45 N, 49.05 N, chromium-vanadium A231, 2 mm, 2 mm, 10.5 mm, 14.5 mm, 80 mm, 12 coils and 922.74 MPa, respectively. The magnitude for blade-closing spring was 124 mm, 38 mm, 2.45 N, 264.50 N, chromium-vanadium A231, 2 mm, 2 mm, 8 mm, 125 mm, 130 mm, 20 coils and 815.75 MPa, respectively. IOP Conf. Series: Materials Science and Engineering 532 (2019) 012011 doi:10.1088/1757-899X/532/1/012011

Figure 9. Free body diagram for analysis of angle of pressure IOP Conf. Series: Materials Science and Engineering 532 (2019) 012011 doi:10.1088/1757-899X/532/1/012011 By neglecting F; and Feat the last 3 equations, normal force of cam acting on follower was:

Equation of cam velocity is written as follows: Equation of cam acceleration is written as follows:

Table 1. Pressure angle of follower The largest angle of pressure between cam and follower was 41.40°. This magnitude was too large and not necessary for cam-follower mechanism as it required high force and caused mechanism failure that led to machine damage.

The results of normal force, vertical force and horizontal force are shown in Table 2. The maximur torque required to activate blade mechanism was 80.09 N-m.

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Principles of aeration

by Dr. Karri R A M A R A O

2021, Principles of aeration and Emergency aeration

In most natural waters, the supply of oxygen to water (diffusion from the atmosphere and production from underwater photosynthesis) exceeds the amount used in oxygen-consuming processes, and fish seldom have problems obtaining enough... more

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Advances in Mechanical Engineering

by Amedeo Amoresano

2021

The analysis two-phase flow inside centrifugal pumps is a fundamental issue in several engineering applications. This often represents a bad working condition with respect to single phase one, causing head reduction, efficiency decrease,... more

Ficure 1: Cylindrical coordinates for the bubble motion analysis.

Starting from vector Euler’s Equation in cylindrical coordi- nates and taking into account hypotheses 2, 3, and 6 the following equations can be formulated: Integrating these two equations, pressure field can be evaluated in two extreme cases: only water inside the impeller and only gas inside the impeller.

Figure 5: Separation inside a moving duct between air and water in slug flow.

where drag coefficient Cz can be evaluated by Reynolds number [17] and virtual mass coefficient C, is assumed to be 0.5 as for a spherical droplet [17].

FiGure 3: Dimensioned sketch of the rotor. Ficure 2: Centrifugal pump with suction duct and flange, both transparent.

FicurE 7: Schematic representation of layers hierarchy.

Ficure 8: Polar coordinates of bubble trajectories for different diam- eter.

FiGure 9: Bubble diameter percentage reduction versus time.

Ficure 10: Polar coordinates of bubble trajectories for different water flow rates (dy) = 0.1 mm).

Ficure Ll: Percentage change of bubble diameter for different water flow rates (dy) = 0.1 mm).

Nomenclature to noncondensable gas dissolved in water to be extracted and thermally exploited, both for thermal and electrical power generation. The right understanding of condition leading to two-phase flow regime is a fundamental issue for the best operation of such plants, as in many other industrial applications as previously mentioned.

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Dibyanandh

by Alok Kumar Jena

2017

A comparative study

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Design Characteristics of Spiral Aerator

by SUBHA ROY

2017

In this study, the performance of a spiral aerator, a modified design of the paddlewheel aerator, was evaluated to determine its applicability in aquaculture ponds. The aeration characteristics of the spiral aerator were determined by... more

Figure 3. Effects of Reynolds criterion on E.

FicureE 7. Variation of aeration cost (AC) with rotational speeds (N) at C, = 1 mg/L (dissolved oxygen concentration in pond) and different pond sizes (V).

Ficure 8. Variation of aeration cost (AC) with rotational speeds (N) at C, =2 mg/L (dissolved oxygen concentration ir pond) and different pond sizes (V).

Figure 9. Variation of aeration cost (AC) with rotational speeds (N) at C, = 3 mg/L (dissolved oxygen concentration in pond) and different pond sizes (V).

Ficure 10. Variation of aeration cost (AC) with rotational speeds (N) at C, =4 mg/L (dissolved oxygen concentration in pond) and different pond sizes (V). of SAE of 1.0 kg O,/kWh is achieved. However, optimum dynamic conditions will occur corre- sponding to the lowest aeration cost. Therefore, an economic analysis of the aerator has been per- formed. The prime idea was to determine the optimum value of rotational speed for different pond sizes and initial DO values in the pond at which the aeration cost is minimized. The relationship between SAE and FE is expressed in Equation 9. Assuming the water temperature to be 20C, g=9.81 m/sec’, R,=0.3m, AC=9.07x10kg/m?, p= 1000 kg/m? and v,, = 10~° m/sec, SAE can be written in terms of N and E as:

where Cy, =capital cost of an aerator (Rs); O;, = annual operating hours of aerator; SV, [, and MC represent salvage value, interest rate and repair, and maintenance cost of aerators, respec- tively, in terms of percentage of capital cost; L,=useful life of aerator (yr); and LC = labor cost (Rs/h).

®Rs 68.16=$1. TABLE 2. Details of capital cost, useful life, annual operating hours, and other costs of spiral aerator.

Cp = dissolved oxygen concentration in pond. TABLE 3. Optimum rotational speeds (rpm) of spiral aerator at different pond volumes and C,, values.

Ficure 1. Photographic view of the spiral aerator. where P, = total power requirement for aeration (kW) and AE = aeration efficiency of aerator (kg O,/kWh). TABLE |. Pertinent parameters for determination of tota oxygen demand in an Indian major carp (IMC) pond.

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Design of high efficiency surface aerators Part 1. Development of new rotors for surface aerators

by Beatriz Cancino-Madariaga

2016

The main objective of this work was the design of a high efficiency centrifugal surface aerator for fishponds. The proposed system has been designed to be used with photovoltaic panels as an energy supply. The work is presented in three... more

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Design of high efficiency surface aerators

by Beatriz Cancino-Madariaga

2015, Aquacultural Engineering

The main objective of this work was the design of a high efficiency centrifugal surface aerator for fishponds. The proposed system has been designed to be used with photovoltaic panels as an energy supply. The work is presented in three... more

Fig. 1. Drawing of the rotor with inlet and exit angle.

Fig. 2. Drawing of the angles of a blade for axial flow. Fig. 1 shows a general schematic of the rotor with the inlet and exit angles of the blade. The inlet angle is the first angle to have contact with the water when the rotor turns. The exit angle is the blade’s angle that gives the direction to the splashed water. The axial pumps have two principals parts: the impeller, or rotor, which forces the liquid into a rotary motion by impelling action and the pump casing which directs the liquid to the impeller and leads it away at a higher pressure. The impeller vanes and impeller side walls form the impeller channels (Stepanoff, 1993). The theory used for the analysis of the axial flow pump is based on the movement of the liquid when it is flowing between the channels. In the aerator we can considerer that the rotor and the spaces between the blades are the channels where the liquid acquires the velocity and the exit angle. Fig. 2 shows the angles of a blade in an axial flow pump.

Fig. 4. Drawing of the prototype used for the aeration tests. hprof is the distance measured between surface of water to end of blade, or immersion depth.

Fig. 6. General schematic diagram for flat rotors. Fig. 5. Picture of the prototype used for the aeration tests.

Fig. 10. Kinetic 1 type rotor, 6; = 21°. Fig. 9. Conrad propeller.

Fig. 11. Kinetic 2 type rotor, 6; = 26°.

Fig. 12. Kinetic 3 type rotor. Details of the connection between the blade and the body of the rotor

Summary of the criteria and results in the design of the rotor (Cancino, 2001) Table 1 Table 1 shows the steps used for calculating the design parameters of the rotor. Steps 1-3 are based on previous tests— made by the same researchers— with commercial surface aerators (Cancino, 2001). The number of paddles was chosen according to Stepanoff’s work on axial flow pumps. The exit angle (82) was selected between the typical angles used for axial pumps (Stepanoff). The value of D in the previous equations correspond to rotor’s

Summary of rotors studied Table 2 diameter (D ,). The value of K,, was taken from Stepanoff using the previous steps. Step 9 is calculated using Eqs. (11) and (12) and step 8. The final size of D; (step 10) was measured when the rotor was built. With the real size of D,, the values of K, and yw were calculated using Eq. (21) and (22) (steps 11 and 12). The inlet angle £, (step 12) was calculated using the drawing of Euler's triangle for this rotor. Finally, the rate P/k of the rotor was calculated using Euler's triangle and Eq. (20).

Measurements of lengths described in Fig. 6 for each flat rotor studied Table 3

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Design of high efficiency surface aerators

by Beatriz Cancino-Madariaga

2015, Aquacultural Engineering

The main objective of this work was the design of a high efficiency centrifugal surface aerator for fishponds. The proposed system has been designed to be used with photovoltaic panels as an energy supply. The work is presented in three... more

Fig. 4. Drawing of the prototype used for the aeration tests. Nprof is the distance measured between surface of water to end of blade, or immersion depth.

Fig. 5. Picture of the prototype used for the aeration tests.

Fig. 6. General schematic diagram for flat rotors.

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Design of high efficiency surface aerators

by Beatriz Cancino-Madariaga

2015, Aquacultural Engineering

The main objective of this work was the design of a high efficiency centrifugal surface aerator for fishponds. The proposed system has been designed to be used with photovoltaic panels as an energy supply. The work is presented in three... more

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Design characteristics of pooled circular stepped cascade aeration system

by Avinash Kumar

2014

Aeration experiments were conducted in a brick masonry tank of dimension 4 m × 4 m × 1.5 m to study the design characteristics of pooled circular stepped cascade (PCSC) aeration system. Based on dimensional analysis, non-dimensional... more

Fig. 1. Schematic sectional view of experimental setup for testing of pooled circulat stepped cascade.

Fig. 3. Schematic view of modified propeller pump.

Fig. 4. Variation of NDSAE with Re for different sizes of PCSC.

Fig. 6. Variation of Ne with Re for different sizes of PCSC.

Fig. 5. Variation of NDSAE with Fr for different sizes of PCSC.

Fig. 7. Variation of Ne with Fr for different sizes of PCSC.

Schedule of experiments to optimize the geometric parameters of CSC aerators based on central composite rotatable design (CCRD) - Series | Table 1

Schedule of experiments to optimize the geometric parameters of PCSCP aerators - Series II.

Schedule of experiments for testing of prototype PCSC aerators — Series IV.

Schedule of experiments to optimize the dynamic parameters - Series III.

Experimental results for optimization of N, H/R, and V/R,? — Series I. Table 5 graphs. Regression and ANOVA analysis were conducted for fitting the second order polynomial equation and to examine the statisti- cal significance of the model terms. The significance of the model terms were evaluated by F-test. The adequacy of the polynomial model equation was determined using coefficient of determina- tion (R2), adjusted R, lack of fit and adequate precision. The fitted polynomial equation was expressed as three-dimensional surface plots to visualize the relationship between the responses and the experimental levels of each factor used in the design and to investi- gate the interaction amongst the variables. To optimize the level of each factor for maximum response, “Numerical Optimization” pro- cess was carried out keeping the criteria of independent variables within the range. the central opening of the cascades. the outlet of the propeller pump was opened from all the sides to facilitate the water discharge all around the cascade (Figs. 2 and 3). The pump-motor specifica- tions are: kW - 0.18, rpm - 2750, voltage - 415 V, current - 0.52 A, frequency — 50 Hz, efficiency (electrical to mechanical) - 64%, Make - Kirloskar Electric Co. Ltd., Hubli, India. The specifications of the propeller (Make: Nan Rong Hai Co. Ltd., Taiwan) are: (i) material — high density polyethylene (HDP), (ii) number of paddles - 4, (iii) total diameter — 100 mn, (iv) inlet and exit angles - 15° and 25°, (v) inner and outer width of paddles - 27 and 50 mm and (vi) length of paddles - 30mm. The power consumptions were measured using MECO 3 phase 4 wire power analyzer. The specifications of MECO 3 phase 4 wire power analyzer are as follows: voltage/phase - 50-300 V (P-N), current/phase - 0.2 A to 1.2 A, frequency 45-55 Hz, power factor - 0.300 Lag (L) to 1.000-0.300 Lead (C), operating con- ditions - 0 to 50°C (RH< 70%), Make — Meco Instruments Pvt. Ltd., Navi Mumbai, India. The wire power consumption of the pump (0.16 kW) remained same for all the PCSC aerators as the total dynamic head was maintained the same. The brake power of the pump was calculated by deducting the losses from the wire power. The losses include frictional losses in couplings and bearings, power transmission losses in gearboxes, conversion losses from electrical to mechanical power etc. The losses were calculated by running the pump dry i.e., without the load and the power consumption was found to be 0.11 kW. Therefore, the brake power of the aerator was taken as (0.16-0.11) kW=0.05 kW.

Experimental results for optimization of P. and Ne — Series II. Table 8

Coefficient of determination (R?)=0.951; adjusted R? =0.907; standard deviation (S.D.)= 1.562 x 10~°; coefficient of variation (C.V.)=7.41%; mean =2.107 x 10-°; adequate precision = 20.141. ANOVA analysis of the response surface quadratic model - Series I. Table 6

Optimum values of geometric parameters for pooled circular stepped cascade. Table 9

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Selection of aerators for intensive aquacultural pond

by Avinash Kumar

2014

Aeration cost is the third largest cost in intensive aquaculture system after post larvae and feed cost representing about 15% of total production cost. Therefore, selection of aerators plays a major role in maximizing the profit in such... more

Fig. 2. Variation of aeration cost with hours of aeration for different aerators and pond sizes for C, = 1 ppm.

Fig. 3. Variation of aeration cost with hours of aeration for different aerators and pond sizes for C, = 2 ppm

Fig. 4. Variation of aeration cost with hours of aeration for different aerators and pond sizes for C, = 3 ppm.

Fig. 5. Variation of aeration cost with hours of aeration for different aerators and pond sizes for C, = 4ppm.

Wire power, SOTR and SAE of different type of aerators. Table 1

* Rs 55=1 $ approximately. Capital cost, useful life and other fixed costs of different type of aerators. Table 2

Usefulness of various aerators at different C, values for different pond volumes. Table 3

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Optimization of Positional Angle of Propeller–Aspirator Pump Aerator and Its Performance Evaluation at Different Dynamic Condition

by Avinash Kumar

2014

Aeration test was conducted in a brick masonry tank of dimension 5 × 3 × 1.5 m 3 to evaluate the optimum geometric condition of Propeller -aspirator pump aerator, i.e., positional angle of propeller shaft (α).The results indicated a... more

The aeration experiments were conducted in a brick masonry tank of dimension 5 x 3 x 1.5 m’. The ositional angle of propeller shaft (inclination of the shaft with the horizontal water surface) can bx hanged by changing the position of an arm attached to the supporting structure. The atmospheric air enter: 1rrough the hole A of the propeller shaft due to suction created by the aspirator. Water drawn through th ole B is thoroughly mixed with the air and is finally splashed into the atmosphere. Initially the tap wate: yas deoxygenated using 0.1 mg/L of cobalt chloride and 10 mg/L of sodium sulphite for each 1 mg/L o: issolved oxygen present in water [11]. Thereafter the aerator was operated at the desired conditions as pe 1e experimental design and readings were taken at timed intervals till DO increased from zero to about 80% aturation. The DO deficit was computed for each time. Finally the values of SOTR and SAE wer alculated using Eq. 1 and 2 respectively. Fig.1. Experimental setup for testing of propeller-aspirator-pump aerator.

Fig.2. Variation of E with positional angle of propeller shaft.

However, no unique relationship could be established between Re and E 4.2.2 Effect of Re and Fr on Ne

4.3. Optimum dynamic condition for propeller-aspirator-pump aerator

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Performance evaluation of propeller-aspirator-pump aerator

by Avinash Kumar

2014

Aeration experiments were conducted in a brick masonry tank of dimension 5.25 m Â 2.87 m Â 1.57 m to study the effects of positional angle of propeller shaft (a), submergence depth and rotational speed of shaft on standard aeration... more

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Provided for non-commercial research and education use. Not for reproduction, distribution or commercial use.

A. Kumar et al./Aquacultural Engineering 42 (2010) 70-74 Fig. 1. Experimental set-up for testing of propeller-aspirator-pump aerator.

Fig. 2. Variation of E with positional angle of propeller shaft. A. Kumar et al. /Aquacultural Engineering 42 (2010) 70-74 water to be aerated was fixed in a similar fashion as stated ir Section 3.3.1.

Fig. 5. Effects of Reynolds criterion on power number Ne. The effect of Re and Fr on Ne is shown in Figs. 5 and 6, respectively. It can be seen from Fig. 5 that the data points for different submergence depths are close to each other and could be well fitted by the following equation:

Fig. 6. Effects of Froude criterion on power number Ne. References

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