A problem on Pelton wheel:

**Problem (2 Part b)**

A 4-jet Pelton wheel is supplied from a reservoir in which the water surface is elevated 400 m above the axis of its nozzles through a 500 m long 750 mm diameter pipeline in which a friction head loss of 15 m occurs. The nozzles are 75 mm in diameter and each has a coefficient of velocity of 0.98. The buckets are installed at a radius of 600 mm, move at 48% of the jet speed, deflect the relative flow through an angle of 160° and reduce the relative velocity by 16% due to friction over their surface. The mechanical efficiency is 97%. Find:

a) The coefficient of friction in the pipeline.

b) The speed of rotation of the Pelton wheel.

c) The overall efficiency of the turbine.

d) The power output.

For Solutions look to this file:P2b.doc

**Quiz #7:**

ME 485- Quiz# 7a Name: List No:

1. In Pelton turbine the jet flow rate depends on:

a) The pipe flow rate

b) The number of jets

c) The number of buckets

d) above (a,b)

2. For Pelton wheel turbine with a net head of 250 m and a head loss of 10 m it Is true that the effective head is:

a) 10m

b) 250m

c) 240m

d) 260m

3. For Pelton wheel turbine with a net head of 200 m, and a nozzle coefficient (K_{N})= 0.95 and a rotor efficiency = 0.93 the jet velocity =…………….m/s and the total efficiency=………………….

- A pipe line with a mass flow rate of 600 kg/s which feeds a four jet water Pelton turbine, then the Q
_{jet}=……………m^{3}/s

**Quiz #7 **Solution:Q7.doc

**Quiz #8a:**

ME 485- Quiz# 8a Name: List No:

1. For NPSHA and NPSHR it is true that:

a. Both NPSHA and NPSHR are function of the piping system.

b. Both NPSHA and NPSHR are function of the pump

c. NPSHA is a function of the piping system and NPSHR is a function of the pump.

d. NPSHR is a function of the piping system and NPSHA is a function of the pump.

2. For a water pump the suction tank is open to the atmosphere *p*_{atm} = 101 kP, the saturation pressure at water temperature is 7 kPa, the pump is installed 5 m above the suction tank, and frictional head losses in the suction pipe is 0.5 m, Then NPSHA=………………m.

3. The velocity triangle of a centrifugal compressor with a positive prerotation at the inlet it is true that:

a) *a*_{1}>0

b) *b*_{1}=0

c) *a*_{1}=0

d) *a*_{1}<0

4. For a water pump if the suction specific speed is 3, the rotational speed is 1500 RPM, and the mass flow rate is 9 kg/s then NPSHR is:

a) 1750 m b)much less than 1750 m c) much more than 1750 m d) can't be found

**Quiz #8ab:**

ME 485- Quiz# 8ab Name: List No:

1. The most correct choice is:

a. Both NPSHA and NPSHR don't depend on the piping system.

b. Both NPSHA and NPSHR depend on the piping system

c. Only NPSHA depends on the piping system.

d. Only NPSHR depends on the piping system.

2. For a water pump the suction tank is open to the atmosphere *p*_{atm} = 102 kPa, the saturation pressure at water temperature is 8 kPa, the pump is installed 4.5 m above the suction tank, and frictional head losses in the suction pipe is 1 m, Then NPSHA=………………m.

3. The velocity triangle of a centrifugal compressor with no prerotation at the inlet it is true that:

a) *a*_{1}>0

b) *b*_{1}=0

c) *a*_{1}=0

d) *a*_{1}<0

4. For a heavy oil pump at sea level, if the suction specific speed is 3, and Ω is 1500 radian/s, and the mass flow rate is 9 kg/s then theoretically NPSHR is:

a) 1750 m b) much less than 1750 m c) much more than 1750 m d) can't be found

**Quiz #8a&8ab **Solutions:Q8.doc

**Quiz #9:**

ME 485- Quiz# 9a Name: List No:

- Stage reaction °R=50% when:

a) Δh_{static (stator)}= 2 Δh_{static (rotor)} b) Δh_{static (stage)} =2 Δh_{static (rotor)}

c) Δh_{static (rotor) }= 2 Δh_{static (stage)} d) Δh_{static (rotor) }= 2 Δh_{static (stator)}

- If the impeller exit of an air centrifugal compressor has a radial velocity (C
_{2}r_{ }=30m/s) and area of 0.1m^{2} and the of static pressure is 300 kPa, and the static temperature is 100^{o}C,R =0.287 kJ/kgK then the mass flow rate=……… kg/s

- For an axial turbine it is assumed that:

a) ΔW_{s}=0 b) U_{2}^{2 }= U_{1}^{2} c) W_{2}^{2 }= W_{1}^{2} d) C_{2}^{2 }= C_{1}^{2}

- If the stage reaction (°R) of a turbine is100% then:

a) Δh_{static (stator )}=0 b) Δh_{static (rotor) }= 0 c) Δh_{static (stator )} = Δh_{static (rotor)} d) Δh_{static (stage)} =0

**Quiz #9**Solutions:Q9.doc