Quiz: Mechanical Engineering

Exam: UPPSC AE/Lecturer

Topic: Power Plant

Each question carries 1 mark

Negative marking: 1/4 mark

Time: 8 Minutes

Q1. If the dryness fraction of a sample by throttling calorimeter is 0.8 and that by separating calorimeter is also 0.8, then the actual dryness fraction of sample will be taken as

(a) 0.8

(b) 0.8

(c) 0.64

(d) 0.5

Q2. The capacity of boiler is defined as

(a) The volume of feed water inside the shell

(b) The volume of the steam space inside the shell

(c) The maximum pressure at which steam can be generated

(d) Amount of water converted into steam from 100°C to 110°C in one hour

Q3. William’s law gives a straight-line graph between the rate of steam consumption and (a) pressure of steam

(b) temperature of steam

(c) volume of steam

(d) indicated horse power

Q4. The speed ratio in Parson’s reaction turbine for maximum efficiency of the turbine is

(a) cosα/2

(b) (〖cos〗^2 α)/2

(c) cosα

(d) 〖cos〗^2 α

Q5. The enthalpy drop in impulse steam turbine takes place in

(a) Fixed and moving blades

(b) Only in moving blades

(c) Nozzles

(d) No enthalpy drop

Q6. What is the work ratio when W_net=500kJ/kg,W_turbine=600kJ/kg and W_compressor=100kJ/kg

(a) 5/6

(b) 1/6

(c) 6/5

(d) 1/5

Solutions

S1. Ans. (c)

Sol. Let, x_1=0.8= dryness fraction of steam considering separating calorimeter

x_2=0.8= dryness fraction of steam entering the throttling calorimeter

Also let x = Actual dryness fraction of steam in the sample

x =x_1×x_2= 0.8×0.8= 0.64

S2. Ans. (d)

Sol. The capacity of boiler is defined as amount of water converted into steam from 100°C to 110°C in one hour.

S3. Ans. (d)

Sol. William’s law gives a straight-line graph between the rate of steam consumption and indicated horse power.

S4. Ans. (c)

Sol. The speed ratio in Parson’s reaction turbine for maximum efficiency of the turbine is 〖cos〗^2 α.

Its maximum efficiency is (2〖cos〗^2 α)/(1+cosα)

S5. Ans. (c)

In case of impulse steam turbine there is enthalpy drop in nozzle.

In case of reaction turbine, the expansion of steam takes place partly in the fixed blade and partly in the moving blades. So, enthalpy drop takes place partly in moving blade and partly in fixed blade.

S6. Ans. (a)

Sol. Work ratio is the ratio of network to turbine work

W.R.=W_net/W_turbune =500/600=5/6