A propeller 2m in diameter and like the one for which characteristics arc given in Fig

Explain why the thrust of a fixed-pitch propeller decreases with increasing forward speed.

What limits the rotational speed of a propeller?

What thrust is obtained from a propeller 3m in diameter that has the characteristics given in Fig. 14.3 on p. 520 of 14.1 when the propeller is operated at an angular speed of II 00 rpm and an advance velocity of zero? Assume p = 1.05 kg/m3

What thrust is obtained from a propeller 3 m in dian1eter that has the characteristics given in Fig. 14.3 on p. 520 of 14.1 when the propeller is operated at an angular speed of 1400 rpm and an advance velocity of 80 km/h? What power is required to operate the propeller under these conditions? Assume p = 1.05 kglm3

A propeller 8ft in diameter has the characteristics shown in Fig. 14.3 on p. 520 of 14.1. What thrust is produced by the propeller when it is operating at an angular speed of 1200 rpm and a forward speed of 30 mph? What power input is required under these operating conditions? If the forward speed is reduced to zero, what is the thrust? Assume p = 0.0024 slugstfe.

A propeller 8 ft in diameter, like the one for which characteristics are given in Fig. 14.3, on p. 520 of 14. I, is to be used on a swamp boat and is to operate at maximum efficiency when cruising. If the cruising speed is to be 30 mph, what should the angular speed of the propeller be? Assume p = 0.0024 slugs/ft3 .

For the propeller and conditions described in Prob. 14.6, determine the thrust and the power input.

A propeller is being selected for an airplane that will cruise at 2000 m altitude, where the pressure is 60 kPa absolute and the temperature is l0C. The mass of the airplane is 1200 kg, and the planform area of the wing is 10m2 The lift-to-drag ratio is 30: I. The lift coefficient is 0.4. The engine speed at cruise conditions is 3000 rpm. The propeller is to operate at maximum efficiency, which corresponds to a thrust coefficient of 0.025. Calculate the diameter of the propeller and the speed of the aircraft.

If the tip speed of a propeller is to be kept below 0.8c, where c is the speed of sound, what is the maximum allowable angular speed of propellers having diameters of 2 m ( 6.56 ft), 3m (9.84 ft), and 4 m (13.12 ft)? Take the speed of sound as 335 m /s (1099 ft/s)

For the propeller and conditions described in Prob. 14.10, determine the thrust and the power input. Assume p = 1.2 kg/m3 .

A propeller 2m in diameter and like the one for which characteristics arc given in Fig. 14.3 on p. 520 of 14.1 is used on a swamp boat. If the angular speed is 1000 rpm and if the boat and passengers have a combined mass of 300 kg, estimate the initial acceleration of the boat when starting from rest. Assume p = 1.1 kglm'.

Answer the following questions about axial-flow pumps. a. Axial-flow pumps are best suited for what conditions of head produced and discharge? b. For an axial-flow pump, how does the head produced by the pump and the power required to operate a pump vary with flow rate through the pump?

If a pump having the characteristics shown in Fig. 14.7 on p. 524 of 14.2 has a diameter of 40 em and is operated at a speed of 1000 rpm, what will be the discharge when the head is 3m?

The pump used in the system shown has the characteristics given in Fig. 14.8 on p. 525 of 14.2. What discharge will occur under the conditions shown, and what power is required?

If the conditions are the same as in Prob. 14.15 except that the speed is increased to 900 rpm, what discharge will occur, and what power is required for the operation?

For a pump having the characteristics given in Fig. 14.7 or 14.8 of 14.2, what water discharge and head will be produced at maximum efficiency if the pump diameter is 20 in. and the angular speed is II 00 rpm? What power is required under these conditions?

A pump has the characteristics given by Fig. 14.7 on p. 524 of 14.2. What discharge and head will be produced at maximwn efficiency if the pump size is 50 em and the angular speed is 45 rps? What power is required when pumping water at 10C under these conditions?

For a pump having the characteristics of Fig. 14.7 on p. 524 of~ 14.2, plot the head-discharge curve if the pwnp is 14 in. in diameter and is operated at a speed of 1000 rpm.

An axial-flow blower is used for a wind tunnel that has a test section measuring 60 em by 60 em and is capable of airspeeds up to 40 m/s. If the blower is to operate at maximum efficiency at the highest speed and if the rotational speed of the blower is 2000 rpm at this condition, what are the diameter of the blower and the power required? Assume that the blower has the characteristics shown in Fig. 14.7 on p. 524 of 14.2. Assume p = 1.2 kg/m3

An axial-flow blower is used to air-condition an office building that has a volume of I O' m3 It is decided that the air at 60F in the building must be completely changed every IS min. Assume that the blower operates at 600 rpm at maximum efficiency and has the characteristics shown in Fig. 14.7 on p. 524 of 14.2. Calculate the diameter and power requirements for two blowers operating in parallel.

An axial fan 2m in diameter is used in a wind tunnel as shown (test section 1.2 m in diameter; test section velocity of 60 m/s). The rotational speed of the fan is 1800 rpm. Assume the density of the air is constant at 1.2 kglm3 . '!here are negligible losses in the tunnel. The performance curve of the fan is identical to that shown in Fig. 14.7 on p. 524 of 14.2. Calculate the power needed to operate the fan.

The radial flow pump is best suited for what ondition~ of head produced and discharge?

A pump is used to pwnp water out of a reservoir. What limits the depth for which the pump can draw water?

If a pump having the characteristics given in Fig. 14.10 on p. 528 of 14.3 is doubled in size but halved in speed, what will be the head and discharge at maximum efficiency?

A pump having the characteristics given in fig. 14.10 on p. 528 of 14.3 pumps water at 20C from a reservoir at an elevation of 366 m to a reservoir at an elevation of 450 m through a 36-cm steel pipe. If the pipe is 61 0 m long, what will be the discharge through the pipe?

If a pump having the characteristics given in Fig. 14.1" or 14.11 (both in 14.3) is operated at a speed of 1600 rpm, wha: will be the discharge when the head is 135 ft?

If a pump having the performance curve shown is operated at a speed of 1600 rpm, what will be the maximum possible head developed?

If a pump having the characteristics given in Fig. 14.11 on p. 528 of~ I 4.3 is 40 em in diameter and is operated at a speed of 25 rps, what will be the discharge when the head is 50 m?

A centrifugal pump 20 em in diameter is used to pump kerosene at a speed of 5000 rpm. Assume that the pump has the characteristics shown in Fig. 14.1 I on p. 528 of 14.3. Calculate the flow rate, the pressure rise across the pump, and the power required if the pump operates at maximum efficiency.

Answer the following questions regarding pump sizing and selection. a. What is the difference between a system curve and a pump curve? Explain. b. The operating point for a pump system is established by what condition?

The value of the specific speed suggests the type of pump to be used for a given application. A high specific speed suggests the use of what kind of pump?

The pump curve for a given pump is represented by hp.pump = 20 [I - C~oYJ where hp.pump is the head provided by the pump in feet and Q is the discharge in gpm. The system curve for a pumping application is hp.r = 5 + 0.002Q2 where hp.sys is the head in feet required to operate the system and Q is the discharge in gpm. Find the operating point (Q) for (a) one pump, (b) two identical pumps connected in series. and (c) two identical pumps connected in parallel.

What is the suction specific speed for the pump that is operating under the conditions given in Prob. 14.15? Is this a safe operation with respect to susceptibility to cavitation?

What type of pwnp should be used to pump water at a rate of 10 cfs and under a head of 30ft? Assume N = 1500 rpm.

For the most efficient operation, what type of pump should be used to pump water at a rate of 0.10 m3 /s and under a head of 30 m? Assume n = 25 rps

What type of pump should be used to pump water at a rate of 0.40 m3 /s and under a head of 70 m? Assume N = 1100 rpm.

A pump is needed to pump water at a rate of 0.2 m3 /s from the lower to the upper reservoir shown in the figure. What type of pump would be best for this operation if the impeller speed is to be 600 rpm? Assume f = 0.02 and K, = 0.5.

Plot the five performance curves from Fig. 14.15 on p. 534 of* I 4.5 for the different impeller diameters in terms of the head and discharge coefficients. Use impeller diameter for D.

The pressure rise associated with gases in a compressor causes the gas temperature to increase as well.'lhe ratio of final temperature to initial temperature is less than the ratio of final pressure to initial pressure. Will the final density be (a) less or (b) greater than the initial density?

Methane flowing at the rate of I kg!s is to be compressed by a noncooled centrifugal compressor from 100 kPa to 165 kPa. The temperature ofthe methane entering the compressor is 27C. The efficiency of the compressor is 70%. Calculate the shaft power necessary to run the compressor.

A 36 kW (shaft output) motor is available to run a noncooled compressor for carbon dioxide. The pressure is to be increased from 100 kPa to ISO kPa.lf the compressor is 60% efficient, calculate the volume flow rate into the compressor.

A water-cooled centrifugal compressor is used to compress air from 100 kPa to 600 kPa at the rate of2 kg/s. The temperature of the inlet air is I5C. The efficiency of the compressor is 50%. Calculate the necessary shaft power.

An impulse turbine will produce no power if the velocity of the jet striking the bucket is the same as the bucket velocity. Explain.

A penstock 1 min diameter and 10 km long carries water at I 0C from a reservoir to an impulse turbine. if the turbine is 85% efficient, what power can be produced by the system if the upstream reservoir elevation is 650 m above the turbine jet and the jet diameter is 16.0 em? Assume that J = 0.016 and neglect head losses in the nozzle. What should the diameter of the turbine wheel be if it is to have an angular speed of 360 rpm? Assume ideal conditions for the bucket design [ Vbucket = (1/2)\lj].

Consider an idealized bucket on an impulse turbine that turns the water through 180. Prove that the bucket speed should be one-half the incoming jet speed for a maximum power production. (Hint: Set up the momentum equation to solve for the force on the bucket in terms of Vj and vbuckct; then the power will be given by this force times Vbucket You can use your mathematical talent to complete the problem.)

Answer the following questions about reaction turbines. a. How does a reaction turbine differ from a centrifugal pump? b. What is meant by the "runner" in a reaction turbine?

For a given Francis turbine, 1 = 60, 2 = 90, r 1 = 5 m, r 2 = 3m, and B = 1m. The discharge is 126 m3 /s, and the rotational speed is 60 rpm. Assume T = l0C. a. What should a 1 be for a nonseparating flow condition at the entrance to the runner? b. What is the maximum attainable power with the conditions noted?c. If you were to redesign the turbine blades of the runner, what changes would you suggest to increase the power production if the discharge and overall dimensions are to be kept the same?

To produce a discharge of3.3 m3 /s, a Francis turbine will be operated at a speed of 60 rpm, r1 = 1.5 m, r2 = 1.20 m, B = 33 em, 1 = 85, and 2 = 165. What should (a) a 1 be for nonseparating flow to occur through the runner? What (b) power and (c) torque should result with this operation? Assume T = 1 0C.

A Francis turbine is to be operated at a speed of 120 rpm and with a discharge of200 m3 /s. If r 1 = 3m, B = 0.90 m, and 1 = 45, what should o: 1 be for nonseparating flow at the runner inlet?

Shown is a preliminary layout for a proposed small hydroelectric project. The initial design calls for a discharge of 8 cfs through the penstock and turbine. Assume 80% turbine efficiency. For this setup, what power output could be expected from the power plant? Draw the HGL and EGL for the system.

What determines the minimum and maximum wind speeds at which a wind turbine can operate?

Using the Internet and other resources, identify at least four types of wind turbines. For each type, describe its distinguishing characteristics and its relative advantages and disadvantages.

Calculate the minimum capture area necessary for a wind turbine that will be required to power the 2 kW demands of an energy-efficient home. Assume a wind velocity of 10 mph and an air density of 1.2 kg/m3

Calculate the maximum power derivable from a conventional horizontal-axis wind turbine with a propeller 2.3 m in diameter in a 47 km/h wind with density 1.2 kglm3

A windmill is connected directly to a mechanical pump that is to pump water from a welllO ft deep as shown. The windmill is a conventional horizontal-axis type with a fan diameter of 10 ft. 'I he efficiency of the mechanical pump is 80%. The density of the air is 0.07 lbm/ft3. Assume the windmill delivers the maximum power available. There is 20 ft of 2-inch galvanized pipe in the system. What would the discharge of the pump be (in gallons per minute) for a 30 mph wind? (1 cfm = 7.48 gpm)