Posted tagged ‘impulse turbine’

Frequently Asked Interview Questions for Mechanical Engineers!!

September 18, 2011

1.         What is friction?

2.         What is gear ratio? How it can calculate

3.         What is gyroscopic and gyroscopic effect?

4.         What is mean by Resistance welding
5.         What Is Mean By Ss-314(Stainless Steel Pipe Grade)?
6.         What is pulverization?
7.          What is requirement of bottle filling machine
8.          What is Solution Annealing? kindly explain its process in brief.
9.          What is the basic need for designing the bottle filling machines
10.        What is the critical speed. Compare the critical speed of hollow shaft and solid shaft.
11.        What is the definition of mechanical
12.        What Is The Difference Between Rated Speed And Economic Speed?
13.        What Is The Difference In Is2062 And Is1239
14.        What is the difference between construction of reaction turbine and impulse turbine
15.        What is the difference  between Torque and Power ( layman Idea)?
16.        What is the manufacturing process for impellers of closed, semi open and open type?
17.        What is the principle of operation of simple jet propulsion system?
18.        What is the relationship between cop and hp(horse power) of compressor?
19.        What is the thermodynamics?
20.        What is the use of vanadium (non metal) ?
21.        What is thermodynamics?
22.        What is unit Ps ?
23.        What’s the difference between front and rear wheel drive? on what basis we choose the type of drive?
24.        Whats the range of poissons ratio of a stable material??
25.        When a solid shaft is subjected to tension its linear dimension changes equally as its lateral dimension,then what will               be its poissons
26.        Whether ductile material can fail in brittle manner? WHEN?
27.        Which engine is more suitable over all. petrol engine, diesel engine . what are their differences
28.        Who are the leaders among expansion valve manufacturers? what are the recent developments in the expansion                     valve industry, used in refrigeration abd air-conditioning?
29.        Why Air Conditioner capacity measured in Ton. Like 1.5ton
30.        Why as atmospheric pressure increases,boiling point also increases?
31.        Why desuperheater tubes are bend in shape
32.        Why diesel engine does not have spark plug like petrol engine, how ever petrol is better fuel than diesel?
33.        Why does cycle rim don’t bend even in heavy loads?
34.        Why green curtons are used in hospital?
35.        Why petrol engine gives more power than diesel engine even though diesel engine has high compression ratio?
36.        Why petrol engines have more power than diesel engines of same capacity?
37.        Why the back wheel of tractor is bigger than front wheel?
38.        Why the path of a satellite is always elliptical with earth not at the center of the ellipse?
39.        Why tyres are manufactured in black colour?
40.        Why we cant measure absolute entropy directly,but the change we can?
41.        Why we express the unit of torque in Nm.even though it can be expressed as Joule ( J )?
42.        Why we have to know the specific frequency of any equipment? does anybody know about specific frequency ?
43.        Will you tell me about types and numbers of sensors in Toyota Corolla GLI, Honda Civic and Suzuki Cultus VXRI?
44.        Write down the expression for air standard efficiency of diesel cycle?
45.        You have to design a machine component. For what type of failure (ductile or brittle) you will design?
46.        Even though LPG is economical than petrol,why we are not promoting LPG usage?
47.        Explain bearing nomenclature with example.
48.        Explain Why Nozzles are made convergent and Divergent?
49.        Function of clutch?
50.        How a Diesel Engine Works in Generators?Explain with Labeled Diagram.
51.        How can u increase the efficiency of power plant without changing in effort?
52.        How gravity filling machine is designed
53.        How Hydraulic Power Steering & Clutch works please explain ?
54.        How much efficiency loss will took place in a steam turbine due to low vacuum
55.        how to calculate the speed of conveyor in meter per minute
56.        How to convert from HP to BHP or CC to BHP please explain?
57.        How to find rating of Chiller a.c. plant i.e. how to calculate the a.c. load of an area, needed by Chiller ?
58.        How to measure sound level of engine of tractor?
59.        How turbo charger works?
60.        If I want to set a power plant in desert of ‘Rajasthan’ and I have option of steam and gas power plant. Which plant I                 should set up?
61.        If the blade height is increased,then how it increases the specific speed of centrifugal pump?
62.        If u have to give support in 1 km long bridge,where u will give it & how many?
63.        In a Waste heat recovery boiler feed control valve is after the economizer where as in auxiliary boiler feed control                   valve is given before the economizer.why?
64.        In auto mobile industry for any type of vehicle how can we differentiate 2 stroke and 4 stroke engine….
65.        In hydraulic clutch mechanism can i adjust clutch play? if it is possible please explain ?
66.        increase in unit speed increases the discharge of impulse turbine how?
67.        Name fuels used in nuclear power plant?
68.        On what property u can distinguish material as brittle or ductile?
69.        On what thermodynamic cycle nuclear power plant works?
70.        Pipe. Whats The Concept Behind It?
71.        Purpose of centrifugal pump casing wear ring and impeller wear ring what is back plate in centrifugal pumps and its                 purpose?
72.        Suppose a steel bar of cross sectional area A is subjected to load P at one end and 2P at the other end ,what will be                  the induced
73.        What is vaily gap in welding?
74.        What are engines that use carburetor and that use inductor ? difference between them
75.        What are the conditions considered while evaluating MARGIN OF SAFETY for newly designed mechanical                                components….?
76.        What are the types of welding machine?
77.        What are your significant functional achievements in the present company? How did they contribute to the total                       process
78.        What do you mean gy “Clausius inequality”?
79.        What does a pump develops? Flow or Pressure. Give the Answer with Proper Logic.
80.        What for orifice using in liquid flow line
81.        What is bearing? how many types of bearing
82.        What is difference between sand blasting and grit blasting ? What is its purpose and how is it done ?
83.        What is drive speed & what is driven speed
84.        What is Dry Bulb Temperature and Wet Bulb temperature?
85.        what is electronically operated pneumatic valves? give one example
86.        What is FEED?
87.        A bearing is designated as 6205 , what is it’s bore diameter?
88.        Advantages and disadvantages of using LPG in car?
89.        All Rector or Exchanger have spherical/hemispherical end Why?
90.        Compare Bray-ton and Otto cycle.
91.        Current rating of a 3 phase DG set is 20 Amps, but what will be the per phase current for single phase supply.
92.        Define Overall Heat transfer coefficient.
93.        Does Is 2062 Specifies Only Seamless Pipes Or Erw Pipe Is Also Covered Under Is 2062

Fluid Machines – Pumps and Turbines

September 18, 2011

 

What is a fluid Machine ?
A fluid machine is a device which converts the energy stored by a fluid in to mechanical energy or work.

 

What are positive displacement machines ?
The machine functioning depend essentially on the change of volume of a certain amount of fluid within the machine. There is a physical displacement of the boundary of certain fluid hence it is called positive displacement machine. 

Based on the direction of fluid flow how are the fluid machines classified ?
According to the flow direction of fluid, the fluid machines are classified as
Axial flow machines – The main flow direction is parallel to the axis of the machine.
Radial flow machines – The main flow direction is perpendicular to the axis of the machine ie. in radial direction
Mixed flow machines – The fluid enters radially and leaves axially or vice-versa. 

What is a turbine ?
A turbine converts the energy of the fluid in to mechanical energy which is then utilized in running a generator of a power plant. 

State the difference between impulse and reaction turbines ?
At the inlet of the turbine the energy available is only kinetic energy, the turbine is known as impulse turbine. If the inlet of the turbine, possesses kinetic energy and pressure energy, the turbine known as reaction turbine. 

What are Homologous units ?
In utilizing scale models in designing turbo machines, geometric simililitude is necessary as well as geometrically similar velocity diagrams at entrance and exit from impellers. Two geometrically similar units having similar vector diagrams are called homologous units. 

Define specific speed based on power.
The specific speed (Ns ) of turbine is defined as the speed of some unit of series of such size that it produces unit power with unit head. . 

Define specific speed based on discharge.
The specific speed ( Ns ) of the pump is defined as the speed of some unit of the series of such size that it delivers unit discharge at unit speed 

What is the significance of specific speed ?
The specific speed inversely proportional to the head across the machine. So low specific speed corresponds to high head across it and vice-versa.
The specific speed is directly proportional to the discharge through the machine or power produced by the machine. So low specific speed therefore refers to low discharge or low power machine and vice-versa. 

Name the main parts of a radial flow reaction turbine ?
i) Casing ii) Guide vane iii) Runner iv) Draft tube. 

What is the purpose of the guide vanes in radial flow reaction turbine ?
The purpose of the guide vane is to convert a part of pressure energy of the fluid at its entrance to the kinetic energy and then direct the fluid on to the number of blades. 

What is a draft tube ? In which turbine it is mostly used.
The draft tube is a conduit which connects the runner exit to the trail race, when water is being finally discharged from the turbine. In reaction turbine , the draft tube is mostly used. 

What is the primary function of a draft tube ?
The primary function of the draft tube is to reduce the velocity of the discharged water to minimize the loss of kinetic energy at the outlet. 

Name the main parts of Kaplan turbine.
i). Scroll casing ii). Guide vanes iii). Hub with vanes iv). draft tube 

Name the main parts of pelton wheel .
i) Nozzle ii) Runner with buckets iii) Casing. 

An inward flow reaction turbine running at 250rpm has D1 = 1m, b1 = 0.2m, D2 = 0.5m and b3 = 0.3m. If the water enters the wheel radially at 3.5m/s velocity, determine the discharge and velocity of the flow at the outlet. Assume vane thickness at the extremities to be negligible.
Q = p D1 b1 Uf1 = p D2 b2 Uf2 = p x 1 x 0.2 x 3.5 = 2.199 m3/s
Uf2 = 2.99/ (p x 0.5 x 0.3) = 4.666 m/s 

What are the different performance characteristic curves ?
i) Variable speed curves (or) main characteristics
ii) Constant seed curves (or) operating characteristics
iii) Constant efficiency curves (or) Muschel characteristics 

Give an example for a low head turbine , a medium head turbine and a high head turbine.
Low head turbine – Kaplan turbine
Medium head turbine – Francis turbine
High head turbine – Pelton wheel. 

what are the purposes of casing of a centrifugal pump
i) To provide water to and from the impeller
ii) To partially convert the kinetic energy in to pressure energy 

What are the different types of casing in centrifugal pump ?
i) Volute casing ii) Turbine casing (or) casing with guide blades 

What is a positive displacement pump ?
In the case of positive displacement pumps, the fluid is physically pushed from an enclosed space. The positive displacement pumps can be either reciprocating type or rotary type. 

Where is the reciprocating pump well suited ?>
The reciprocating pump is well suited for relatively small capacities and high heads. 

what are the main components of a reciprocating pump ?
1)cylinder 2) Piston 3) suction valve 4) Delivery valve 5) Suction pipe 6) delivery pipe 7) crank shaft and connecting rod mechanism. 

Define coefficient of discharge of reciprocating pump.
The ratio between the actual discharge and theoretical discharge is known as coefficient of discharge. Cd = Qact / Qthe. 

Define slip of the reciprocating pump. When does the negative slip occurs ?
The difference between theoretical discharge and actual discharge is called the slip of the pump.
Slip = Qthe. – Qact , % of slip = (Qthe. – Qact ) x 100 / Qthe.
Negative slip occurs when delivery pipe is short suction pipe is long and pump is running at high speed. 

Differentiate between single acting and double acting reciprocating reciprocating pump.
In single acting pump, there is one suction valve and one delivery valve. On the backward stroke of the piston, the suction valve opens and water enters into the cylinder space. On the forward stroke, the suction valve closes and delivery valve opens, the water is forced through the delivery pipe.
In the double acting pump, there are two suction valves and two delivery vales one in the front and one in the rear. When the piston moves backward, the suction valve in the front opens and delivery valve in the rear opens and water is forced through it. When the piston moves forward, the suction valve in the rear opens and delivery valve in the front opens and water is forced through it. 

What is an indicator diagram of a reciprocating pump ?
The indicator diagram of a reciprocating pump is the diagram which shows the pressure head in the cylinder corresponding to any position during the suction and delivery strokes. 

A single acting single cylinder reciprocating pump has the following characteristics.
Discharge = 6 lps, suction head = 4m, Delivery head = 20m, Find the energy required to drive the pump.
Energy required = r g Q ( Hs + Hd ) Watts = (1000 x9.81 x 6×10-3 x (4 + 20) / 1000
= 1.409 kW. 

What is an air vessel and what is its purpose ?
An air vessel is a closed chamber connected on the suction or delivery or both sides of the reciprocating pump to obtain a more uniform flow. 

Name some rotary positive displacement pumps.
a. Gear pumps.
b. Vane Pumps.
c. Piston pumps.
d. Screw pumps.


MECHANICAL ENGG QUESTIONS-2

August 22, 2011

01-interview-interview questions-placement paper-interview questions and answers-mechanical interview tips-interview skills-interview preparation

  • Different between technology & engineering?

Engineering is application of science. Technology shows various methods of Engineering. A bridge can be made by using beams to bear the load,by an arc or by hanging in a cable; all shows different technology but comes under civil engineering and science applied is laws of force/load distribution.

  • how a diesel engine works in generator?

Diesel engine is a prime mover,for a generator,pump,and for vehicles etc.generator is connected to engine by shaft.mostly in thermal power plat ,there is an engine is used to drive generator to generate power.

  • WHAT IS THE OTHER NAME OF MICROMETER & VERNIER CALLIPER

Micrometer’s other name is Screw Gauze & Vernier caliper’s other name is slide caliper.

  • What is flashpoint?

Flash point: the lowest temperature at which the vapor of a combustible liquid can be ignited in air.

  • what is basic difference between impulse turbine and reaction turbine?

In impulse turbine, jet is used to create impulse on blades
which rotates the turbine and in reaction turbine, no jet
is used pressure energy is converted into kinetic energy.

In impulse turbine fluid enter& leave with same energy ,but in reaction turbine fluid enter with pressure energy&
leaves with kinetic energy

In impulse turbine all the pressure drops in nozzle only &
in reaction turbine pressure drops both fixed & moving
blades.the difference is due to blade profiles.

  • What is the need for drafting?

Drafting is the allowance give to casting process.it also used to remove the casting from mould without damage of
corners.

  • what is the difference between BSP thread and BSW thread?

The British Standard Pipe thread (BSP thread) is a family
of standard screw thread types that has been adopted
internationally for interconnecting and sealing pipe ends
by mating an external (male) with an internal (female) thread.
British Standard Whitworth (BSW) is one of a number of
imperial unit based screw thread standards which use the
same bolt heads and nut hexagonal sizes.

  • What is refrigerant?

Any substance that transfers heat from one place to another,
creating a cooling effect. water is the refrigerant in absorption machines.

  • The amount of carbon present in Cast Iron

Carbon is basically present in the form of cementite in cast iron.Its percentage lies in the range of 2.03-6.67(% by weight of cementite for Cast Iron.If the amount is less than the above range than it is stainless steel.

  • What are the loads considered when designing the Nut and Bolts?

Shear Loads & crushing loads

  • what is the effect of reheat on rankine cycle? 1.efficiency increases 2.work output increases 3. both 4. none of these.

1.Efficiency increases.

this prevents the vapor from condensing during its expansion which can seriously damage the turbine blades, and improves the efficiency of the cycle, as more of the heat flow into the cycle occurs at higher temperature.