Steam Boilers, Engines, Nozzles And Turbines MCQ Questions & Answers

41

The velocity of steam leaving the nozzle (V) is given by (where K = Nozzle coefficient or nozzle efficiency and h_d = Enthalpy or heat drop during expansion of steam in a nozzle)

A) V = 44.72 $${{\text{h}}_{\text{d}}}\sqrt {\text{K}} $$ B) V = 44.72 $${\text{K}}\sqrt {{{\text{h}}_{\text{d}}}} $$ C) V = 44.72$$\sqrt {{\text{K}}{{\text{h}}_{\text{d}}}} $$ D) V = 44.72 $${\text{K}}{{\text{h}}_{\text{d}}}$$

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Answer & Solution

Answer: Option C

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42

Reheating of steam in a turbine

A) Increases the work-done through the turbine B) Increases the efficiency of the turbine C) Reduces wear on the blades D) All of these

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Answer & Solution

Answer: Option D

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43

If the critical pressure ratio for steam is 0.546, then the steam is initially

A) Wet steam B) Dry saturated steam C) Superheated steam D) None of these

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Answer & Solution

Answer: Option C

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44

The function of injector used in small steam plants is to

A) Create vacuum in furnace B) Create vacuum at turbine exhaust C) Pump feed water D) Dose chemicals in feed water

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Answer & Solution

Answer: Option C

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45

A condenser where circulating water flows through tubes which are surrounded by steam, in known as

A) Surface condenser B) Jet condenser C) Barometric condenser D) Evaporative condenser

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Answer & Solution

Answer: Option A

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46

A wet vapor can be completely specified by

A) Pressure only B) Temperature only C) Dryness fraction only D) Pressure and dryness fraction

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Answer & Solution

Answer: Option D

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47

A turbine is said to have an axial discharge when the steam leaves the blade tip at _________ to the direction of the blade motion.

A) 60° B) 90° C) 180° D) 270°

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Answer & Solution

Answer: Option B

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48

The draught (in mm of water), for maximum discharge of flue gases through the chimney, is given by (where H = Height of the chimney in meters and T₁ = Absolute temperature of air outside the chimney in K)

A) $$\frac{{{{\text{T}}_1}}}{{88.25{\text{H}}}}$$ B) $$\frac{{88.25{\text{H}}}}{{{{\text{T}}_1}}}$$ C) $$\frac{{{{\text{T}}_1}}}{{176.5{\text{H}}}}$$ D) $$\frac{{176.5{\text{H}}}}{{{{\text{T}}_1}}}$$

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Answer & Solution

Answer: Option D

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49

In a reaction turbine, when steam flows through the fixed blades,

A) Pressure increases while velocity decreases B) Pressure decreases while velocity increases C) Pressure and velocity both decreases D) Pressure and velocity both increases

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Answer & Solution

Answer: Option B

Solution:

In a reaction turbine, the flow of steam goes through both fixed and moving blades. Here's what happens to the steam as it flows through the fixed blades:

The fixed blades, also known as nozzles or guide vanes, serve to direct the flow of steam onto the moving blades at a specific angle. They do not impart any significant kinetic energy to the steam.

As the steam flows through the fixed blades, its pressure decreases. This is because the fixed blades are designed to convert the pressure energy of the steam into kinetic energy by accelerating the steam.

Simultaneously, the velocity of the steam increases as it passes through the fixed blades. This is a result of the pressure drop, which causes the steam to accelerate to maintain conservation of mass.

So, in a reaction turbine, when steam flows through the fixed blades, Option B: Pressure decreases while velocity increases is the correct description of what happens.

50

Over fire burning is the phenomenon of

A) Supply of excess, air B) Supply of excess coal C) Burning CO and unburnt in upper zone of furnace by supplying more air D) Fuel bed firing

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Answer & Solution

Answer: Option C

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Steam Boilers, Engines, Nozzles And Turbines MCQ Questions & Answers | Mechanical Engineering