A hydraulic machine, such as a pump, turbine, fan, or compressor, functions by exchanging energy with the fluid that is passing through it. This lesson focuses on a fan, a hydraulic device that interacts with air as a fluid. Hydraulic machines can be classified in many different ways: According to how they exchange energy with the fluid + Receive the energy of the fluid, and convert it into mechanical energy (water turbine, wind turbine ...) + Supply power for fluids (pumps, fans, compressors, etc.) According to the principle of interaction with fluids in the energyexchange process + The turbomachinery van machine uses the rotation of an impeller (including the blades) to exchange kinetic and potential energy with the fluid. The fluid velocity, outlet, and inlet pressure are characteristic parameters for determining the operating state. Divided into 2 subclasses: centrifuges and axial machines. + The volumetric machine exchanges energy with the fluid on the principle of compressing the liquid in a closed volume under the effect of hydrostatic pressure, with the form of energy exchange being pressure. The volumetric machine is capable of working with high pressure but with a small flow. Machine speed is a parameter that determines machine operation.
HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY Faculty of Transportation Engineering Department of Aerospace Engineering AERO ENGINEERING LAB _ REPORT Lesson 2: SURVEY THE CHARACTERISTIC OF CENTRIFUGAL FAN (Group _ Class CC01) List of group members: Name Nguyễn Ngọc Minh Trịnh Ngọc Thành Lê Việt Hùng ID 2052598 2052709 2052502 Lê Hồng Quân 2053369 Nguyễn Vương Sáng 2053397 Task contribution Data process and graphing Data process and graphing Search theory and report Check and edit report follow by the requirements of lecturer Check and edit report follow by the requirements of lecturer Table of contents Hydraulic machine Figure Head distribution to flow rate in some van machines Figure Centrifugal vane machine model Experiment equipment Figure Centrifugal fan model FM40 .8 Figure Sensors and their characteristic on the suction and discharge pipe 2.1 Experimental system setup 10 Figure Connect the experiment device's wire 11 2.2 Noteworthy quantities 11 The survey of the centrifugal fan characteristic curve 12 3.1 Experiment purposes and requirements 12 3.2 Principle 12 3.3 Experiment operation 12 3.3.1 Experiment steps by steps 12 3.3.2 Data and processing 13 Table Resultant at fan setting 100 - 3540 RP 14 Table Resultant at fan setting 60 - 2124 RPM 15 Figure Characteristic of fan at 100 percent 15 Figure Characteristic curve of fan at 60 percent 15 Figure System impedance and P-Q performance curves .16 Hydraulic machine A hydraulic machine, such as a pump, turbine, fan, or compressor, functions by exchanging energy with the fluid that is passing through it This lesson focuses on a fan, a hydraulic device that interacts with air as a fluid Hydraulic machines can be classified in many different ways: According to how they exchange energy with the fluid + Receive the energy of the fluid, and convert it into mechanical energy (water turbine, wind turbine ) + Supply power for fluids (pumps, fans, compressors, etc.) According to the principle of interaction with fluids in the energy-exchange process + The turbomachinery/ van machine uses the rotation of an impeller (including the blades) to exchange kinetic and potential energy with the fluid The fluid velocity, outlet, and inlet pressure are characteristic parameters for determining the operating state Divided into subclasses: centrifuges and axial machines + The volumetric machine exchanges energy with the fluid on the principle of compressing the liquid in a closed volume under the effect of hydrostatic pressure, with the form of energy exchange being pressure The volumetric machine is capable of working with high pressure but with a small flow Machine speed is a parameter that determines machine operation The proper sort of hydraulic system should be used according to the function (head height, flow rate) A machine is selected Figure illustrates how three common hydraulic machine types (volumetric machine, centrifugal vane machine, and axial guide vane machine) used in water pumps distribute heads according to flow rate Figure Head distribution to flow rate in some van machines For centrifugal vane machines, the fluid enters the center of the revolving blades in the rotors and pushes the centrifuge outside, where it is then collected by a collecting chamber and sent to the exit Large kinetic energy is transferred to the fluid at high spinning speeds The conversion of kinetic energy into pressure results in the pressure differential between the outflow and intake Machines with centrifugal vane motion are employed in several industries Low static pressure, noise, and other factors are restrictions, nevertheless Figure Centrifugal vane machine model The characteristic quantities of centrifugal fan machines include: Volume flow rate measured by barrier ring: - The actual volume flow rate have the following function: Qv=Cd Q Tℎeoryeory - The theory flow rate can be calculated using: QTℎeoryeory =V A Velocity of the fluid V: V= QTℎeoryeory A - Since the air is incompressible at the operate condition of the centrifugal fan machine Thus, Q at inlet equal Q at outlet (Continuity of the flow) Q inlet =Q outlet To calculate the flow rate of discharge we can instead calculate the flow rate at the inlet of the fan - Using Bernoulli equation for the total pressure at the inlet of the centrifugal fan: P 1= ρ V 21 + ρg ℎeory1 + Because the machine is located at the same level, we can neglect the effect of the heigh h The equation ρg ℎeory1 which is the hydrostatic pressure at heigh h become P0 ρ V 21 P 1= + P0 + Now we replace the V1 for Q/A1 Qinlet = Ainlet √ 2( P1 − P0 ) ρ While A is area at the inlet: A= π d2 The equation become: π d2inlet √2(P − P 0) Q inlet = 4ρ - P1 − P0=∆ P which is the differential pressure at the orifice The final equation become: Cdπ d 2inlet √2 ∆ P Q inlet = 4ρ Total pressure supplied by the centrifugal fan: - The total pressure supplied by the centrifugal fan is actually the energy supplied by the fan Ptf =∆ E=E − E - Where E1 and E2 is the total energy per unit volume at the inlet and outlet of the fan acquired from the Bernoulli’s equation: E2 = P2 + ρV 22 + ρg ℎeory2 ρV 21 E1 = P1 + + ρgℎeory - Replace E1 and E2 in to the first equation: ρV 22 ρV 21 Ptf =( P − P1 ) + − +( ρg ℎeory2 − ρg ℎeory1) 2 ( - ) Because the machine is located at the same height, therefore, [h1 = h2 ] and: ( ρg ℎeory2 − ρg ℎeory1 )=0 The final equation of pressure generated by the fan become: Ptf =( P − P1 ) +¿ With: (SI units) 𝑑 : flow barrier diameter Delta 𝑃 : the pressure difference when passing through the flow barrier 𝜌 : the density of air Cd : flow rate coefficient 𝐴 : cross-sectional area 𝑃1 , 𝑃2 : impeller front and rear pressure 𝑉1, 𝑉2 : fan inlet and outlet velocities Experiment equipment The experimental set consists of a centrifugal fan mannequin as proven in Figure 8, an IDF7 data processor, and two impellers with exclusive blades which are set in variousdirections The device is linked to the pc by means of the USB port Figure Centrifugal fan model FM40 FM40 operates with one of two handy impellers (backward-curved blades and forward-curved blades) with rotational velocity managed by using an interactive program The impeller is placed in the manifold and related to two ducts (one is a suction pipe, and one is a discharge pipe) positioned at right angles to every other On these two pipes are sensors and different devices as follows (Figure 9): Suction pipe: sensor measures inlet stress and stress earlier than the fan, temperature sensor, honeycomb grid stabilizes the glide before it enters the fan Discharge pipe: sensor measures the fan outlet pressure, and a waft control device There is also a torque sensor on the motor shaft Figure Sensors and their characteristic on the suction and discharge pipe Note: The glide manipulate device does no longer keep a regular waft in case of being nearly closed and small drift but will be greater steady as the opening gradually increases FM40's two impellers are numbered: (1) backward-curved blades and (2) forward curved blades as proven in Figure 10 Figure FM40's two impellers Note: Impeller number two is out of the shaft, and the vibration is greatest when the motor pace is 25% Do now not function the gadget at this speed! 2.1 Experimental system setup Connect the wires of the experimental gadget as proven in Figure 11 Then, flip on the TOTAL and MAINS switches, the “Power” light is on when the energy is on and the “Active” mild is on when the experiment system is related to the computer Note: - The TOTAL and MAINS change should be in the OFF position during the installation - Avoid multiple dismantle and assemble Figure Connect the experiment device's wire 2.2 Noteworthy quantities Constants: Impeller’s diameter D = 180mm Flow rate coefficient Cd = 0.596 Atmospheric pressure Pa = 101 kPa Gravity acceleration g = 9.81m/s2 The diameter of the sunction pipe d1 = 95mm The diameter of the discharge pipe d2 = 75mm Quantities Symbol Measured values The pressure difference between the fan inlet and oulet (Pa) dpf = P2 – P1 The pressure difference at the barrier ring (Pa) dpo The motor shaft’s torque (Nm) t Fluid temperature (oC) Ta Air density(kg/m3) ρair The rotational speed of the motor shaft (rpm) n Calculated values Volume flow rate (m3/s) Qv Inlet velocity (m/s) V1 = Qv/A1 Outlet velocity (m/s) V2 = Qv/A2 Total pressure the fan supplied (Pa) The mechanical power of the motor supplied to the impeller (W) The energy produced by the impeller (energy supplied to the air stream) (W) The energy conversion efficiency from mechanical to pressure (%) ( ( v 22 − v 21 ) ρ) PtF= +( P − P1 ) 2 πn P m= t Pu=Q v PtF E gr = Pu ×100 % Pm The survey of the centrifugal fan characteristic curve 3.1 Experiment purposes and requirements Purpose of the experiment: - To understand the method of surveying and plotting the characteristic curve of a centrifugal fan when operating at a constant speed - Collect data and draw the graphs of: o The fan characteristic curve (types of pressure according to volume flow) o Efficiency vs volume flow rate - Make a comment on the trend of variation, the extreme point of the quantities 3.2 Principle Based on the fan characteristics => Choosing the most suitable fan for the system 3.3 Experiment operation 3.3.1 Experiment steps by steps - Step 1: Set the fan to maximum speed and record the maximum fan flow rate - Step 2: Rotate the fan outlet to position where the flow in minimum and record this value using logging button - Step 3: Determine the flow rate step by dividing the range of values in to more than 10 equal intervals - Step 4: Slowly open the fan outlet and observe the change in the flow rate When the flow rate values fluctuate around the value to get the result, we record the result using logging button - Step 5: Slowly open the fan outlet to next increment and repeat step until acquire maximum flow - Step 6: Save the experimental results 3.3.2 Data and processing Environment’s air condition Since this data did not change very much during the experiment, we can summarize the air properties of the experiment by averaging it: Air density (kg/m3) 1.133 Air temperature() 32.2 Atmospheric pressure 101 Experiment result data Sample Number 10 Fan Discharge Motor Torque t [Nm] Orifice outlet setting Orifice Differential Pressure [kPa] Fan Differential Pressure [kPa] Discharge Coefficient 0.25 0.24 0.24 0.23 0.22 0.20 0.16 0.14 0.14 0.13 0.208 0.197 0.178 0.161 0.129 0.083 0.031 0.012 0.002 0.000 0.233 0.245 0.272 0.299 0.347 0.418 0.504 0.542 0.578 0.596 0.596 0.596 0.596 0.596 0.596 0.596 0.596 0.596 0.596 0.596 Qv [l/s] 103.98 101.17 96.33 91.48 81.76 65.85 39.83 24.80 9.72 4.85 Fan Differential Fan Discharge Pressure [kPa] 0.215 0.212 0.199 0.182 0.154 0.127 0.109 0.098 0.088 0.085 Qv [l/s] 0.00 4.86 14.60 23.36 38.35 49.43 55.10 58.65 60.46 61.43 Cd Mechanical Power Pm [W] 91.69 87.68 88.83 84.24 81.38 75.65 60.75 52.72 52.72 47.57 Inlet Velocity Outlet Velocity V1 [m/s] 14.67 14.27 13.59 12.91 11.54 9.29 5.62 3.50 1.37 0.68 V2 [m/s] 23.54 22.90 21.81 20.71 18.51 14.90 9.02 5.61 2.20 1.10 Total Pressur e ptF [kPa] 0.42 0.43 0.44 0.45 0.47 0.49 0.53 0.55 0.58 0.60 Power Output Fan Efficiency Pu [W] 44.19 43.21 42.04 40.97 38.12 32.56 21.21 13.71 5.64 2.89 Egr [%] 48.20 49.28 47.33 48.64 46.84 43.05 34.92 26.00 10.69 6.08 Total Pressur e ptF [kPa] 0.22 0.21 0.20 0.19 0.18 0.17 0.16 0.16 0.15 0.15 Power Output Fan Efficiency Pu [W] 0.00 1.03 2.95 4.47 6.91 8.42 8.96 9.32 9.27 9.36 Egr [%] 0.00 7.16 18.28 26.54 37.91 39.51 42.74 43.71 42.77 43.23 Table Resultant at fan setting 100 - 3540 RP Sample Numbe r 11 12 13 14 15 16 17 18 19 20 Orifice outlet setting Motor Torque t [Nm] 0.06 0.06 0.07 0.08 0.08 0.10 0.09 0.10 0.10 0.10 Orifice Differential Pressure -0.467 -0.466 -0.463 -0.456 -0.439 -0.420 -0.408 -0.401 -0.397 -0.394 Orifice Differential Pressure [kPa] 0.000 0.000 0.004 0.010 0.028 0.047 0.058 0.066 0.070 0.073 Fan Differential Pressure 0.225 0.222 0.209 0.192 0.164 0.137 0.119 0.108 0.098 0.095 Mechanical Power Pm [W] 14.44 14.44 16.16 16.85 18.22 21.32 20.97 21.32 21.66 21.66 Inlet Velocity V1 [m/s] 0.00 0.69 2.06 3.30 5.41 6.97 7.77 8.27 8.53 8.67 Outlet Velocity V2 [m/s] 0.00 1.10 3.31 5.29 8.68 11.19 12.47 13.27 13.68 13.91 Table Resultant at fan setting 60 - 2124 RPM Characteristic chart 0.70 60.00 0.60 50.00 0.50 40.00 0.40 30.00 0.30 20.00 0.20 10.00 0.10 0.00 103.98 Fan Efficiency (%) Total Pressure (kPa) Fan Performance at 3540 rpm 101.17 96.33 91.48 81.76 65.85 Total Pressure 39.83 24.80 9.72 0.00 4.85 Fan Efficiency Fan Discharge (l/s) Figure Characteristic of fan at 100 percent Fan Performance at 2124 rpm 0.25 50.00 45.00 40.00 35.00 0.15 30.00 25.00 0.10 20.00 15.00 0.05 10.00 5.00 0.00 61.43 60.46 58.65 55.10 49.43 Total Pressure 38.35 23.36 Fan Efficiency Fan Discharge (l/s) Figure Characteristic curve of fan at 60 percent Discussion 14.60 4.86 0.00 0.00 Fan Efficiency (%) Total Pressure (kPa) 0.20 a Comparison with some other characteristic fan Figure System impedance and P-Q performance curves After having some look on other resources, we noticed that the real-world characteristic chart for a centrifugal fan can be much more complicated, as side picture They can be concern about the noise level, Power consumption of the fan too In the context of this experiment, we can compare the fan discharge (Q) – Total pressure (P) chart The Q-P chart of Figure and are similar to the reference Figure 3: increase of airflow will cause decrease of pressure loss / total pressure to decrease b Characteristic of fan result 1) Max efficiency of near 50% is reached at about 90 L/s with fan setting of 100% 2) Max efficiency of near 45% is reached at 55 L/s with fan settings of 60% 3) Pressure supplied by fan decrease as flow rate control increase This is true for fluid theory 4) Maximum fan flowrate at 100% is 103L/s, with generated pressure of 0.55kPa 5) Maximum fan flowrate at 60% is 61L/s, with generated pressure of 21.5kPa Some recommendation about the experiment Problems with COM connection from the experiment device and computer While working with the system, we notice that our supervisor teacher had to turn of and on the computer multiple times just to make the device to connect to the PC on COM6 However, one of our team member had experience with this type of connection, and provided a better way to fix this connection without having to restart the PC, and will save which ever team working on this lots of times Adjusting the exit orifice Session 10 - Centrifugal Fan Features, TechCompass Page 16 of 17 “The flow control device does not keep a steady flow in case of being nearly closed and small flow but will be more stable as the opening gradually increases.” This suggested that we should only work with this fan at orifice output level more than 20%, as lower will cause unstable flow Hence, the experiment working with it from level – is not good It should only be from – The orifice in Figure in the lab already has marks on it, representing different st Lab Documents of Aerospace Engineering – Department of Aerospace Engineering , HCMUT Page 17 of 17