Compressors, Fans & Blowers

Differentiate between fan, blower and compressor.

Compare axial flow compressor with centrifugal flow compressor.

The rotational speed of a two-bladed axial flow fan is $2900 \text{ rpm}$. At the mean radius of $16.5 \text{ cm}$, the rotor blades operate at $C_l = 0.8$ with $C_p = 0.045$. The inlet guide vanes produce a flow angle of $20^\circ$ to the axial direction and the axial velocity through the stage is constant at $20 \text{ m/s}$. For the mean radius, determine the rotor relative flow angles, the stage efficiency, the rotor static pressure increase, and the size of the blade chord needed for this duty.

Differentiates among compressors, fans and blowers.

Deduce the work done and efficiency equation of fan with help of parametric analysis.

A centrifugal fan running at 1500 rpm has inner and outer diameters of the impeller as 0.2 m and 0.24 m. The absolute and relative velocities of air at entry are 21 m/s and 20 m/s, respectively, and those at exit are 25 m/s and 18 m/s, respectively. The flow rate is 0.6 kg/s, and the motor efficiency is 80%. Determine (i) the stage pressure rise, (ii) the degree of reaction and (iii) the power required to drive the fan. Assume the flow to be incompressible with the density of air as $1.22 \text{ kg/m}^3$.

Explain the effects of blade profile on the working of a centrifugal compressor.

What are the methods adopted to increase the efficiency of the centrifugal pump by altering the shape of the casing of chamber surrounding the impeller? Briefly explain with neat sketches.

A three-stages centrifugal pump has impeller 40 cm in diameter and 2 cm wide. If the blade angle at outlet is $45^\circ$ and the area occupied by the thickness of the vanes may be assumed 8% of the outlet area. If the pump delivers $3.6 \text{ m}^3/\text{min}$ when running at 920 rpm, determine (i) power of the pump, and (ii) Manometric head.

Prove that the work done by a single stage reciprocating compressor without clearance volume for isentropic compression is $W = m c_p (T_1 - T_2)$, where the symbols have their usual meaning.

Estimate the minimum work required to compress $1.5\text{ kg}$ of air from $1.0\text{ bar, } 27^\circ C$ to $20\text{ bar}$ in two stages, if the law of compression is $pv^{1.25} = \text{constant}$ and intercooling is perfect. Take $R = 287\text{ J/kg-K}$.

Explain the influence of impeller blade shape on the performance of centrifugal compressor.

What is surging in axial flow compressor? How do you control a compressor surge?

A three stage compressor delivers air at $70\text{ bar}$ from an atmospheric pressure of $1\text{ bar}$ and $30^\circ\text{C}$. Assuming the intercooling complete, estimate the amount of minimum work required to deal with $1\text{ kg}$ of air. Also find the amount of heat rejected in each intercooler. The index of compression is $1.2$ throughout. Take $c_p$ for air $= 1.005\text{ kJ/kg-K}$.

Differentiate among fan, blower and compressor in respect of specific ration and pressure rise.

Derive the formula of workdone by reciprocating air compressor with clearance volume and polytropic process.

Estimate the minimum work required to compress 1kg of air from 1 bar $27^{\circ}C$ to 16 bar in two stages, if the law of compression is $Pv^{1.25} = \text{Constant}$ and the intercooling is perfect. Take $R=287\text{ J/kg}^{\circ}\text{K}$.

Define fan, compressor, and blower in respect of specific ratio and rise in system pressure.

Classify the air compressor according to working, action and number of stages.

A centrifugal blower running at $8000 \text{ rpm}$, compresses $5 \text{ m}^3\text{/s}$ of air from $1 \text{ bar}$ and $15 ^\circ\text{C}$ to $2 \text{ bar}$. The index of compression $n = 1.3$. The velocity of flow is $70 \text{ m/s}$ and is constant throughout the impeller. The impeller diameter at inlet and outlet are $0.3 \text{ m}$ and $0.6 \text{ m}$ respectively. Determine (i) the impeller blade angles at inlet and outlet, and (ii) the impeller width at inlet and outlet.

Describe the working principle an axial flow multistage drum type compressor with neat sketch.

Write short notes on hydraulic torque converter with neat sketch.

What is surge in open channel flow? Describe the working principle of surge tank in hydro-electric power plant with neat sketch.