MECHANICAL ENGINEERING

POWER STEERING

2013-12-31T13:17:00.003+05:30

POWER STEERING:

Power steering assists the driver of an automobile in steering by directing a portion of the vehicle’s power to traverse the axis of one or more of the road wheels. As vehicles have become heavier and switched to front wheel drive, particularly using negative offset geometry, along with increases in tire width and diameter, the effort needed to turn the steering wheel manually has increased often to the point where major physical exertion is required. To alleviate this, auto makers have developed power steering systems: or more correctly power-assisted steering on road going vehicles there has to be a mechanical linkage as a fail safe. There are two types of power steering systems hydraulic and electric/electronic.

What is DTSI Technology & DTS-Si Technology ?

2013-12-31T13:15:00.003+05:30

What is DTSI Technology & DTS-Si Technology ?

In DTSi, instead of 1 we are using 2 spark plugs. Flame front formed is able to consume more air-fuel mixture as compared with 1 spark plug, thus more complete burning and more efficiency.

In DTS-Si, with addition of 2nd spark plug, what they are doing is relocating valves position. With proper designing of inlet and outlet valves you can induce extra swirl for inoming air fuel mixture. Due to turbulence, extra efforts are provided for proper mixing of air and fuel. (We can not allow petrol to go in liquid droplet form, it should be finely atomized). With well atomized air fuel mixture, efficiency increases.

Slider Crank and Slotted Lever Quick return motion mechanism

2013-12-25T14:06:00.004+05:30

Slider Crank and Slotted Lever Quick return motion mechanism

What is the difference between nozzle and diffuser?

2013-12-25T14:01:00.002+05:30

What is the difference between nozzle and diffuser?

A nozzle is a device that increases the velocity of a fluid at the expense of pressure.
A diffuser is a device that increases the pressure of a fluid by slowing it down.

Degree of Freedom

2013-12-04T18:37:00.000+05:30

Degree of Freedom :-

The degree of freedom can be defined as the minimum number of independent coordinates which can specify the position of the system completely.
There are total 6 degree of freedom.
Among them 3 are Transnational, 3 are rotational.
The degree of freedom of a body decreases by applying constrains for the body.

Injection molding

2013-12-04T18:36:00.001+05:30

Injection molding :-

Injection molding is a manufacturing process for producing parts by injecting material into a mold. Injection molding can be performed with a host of materials, including metals, glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers.

Material for the part is fed into a heated barrel, mixed, and forced into a mold cavity where it cools and hardens to the configuration of the cavity.

Injection molding is used to create many things such as wire spools, packaging, bottle caps, automotive dashboards, pocket combs, some musical instruments (and parts of them), one-piece chairs and small tables, storage containers, mechanical parts (including gears), and most other plastic products available today. Injection molding is the most common modern method of part manufacturing; it is ideal for producing high volumes of the same object.

Thermoelectrically operated fan using a candle

2013-12-04T18:35:00.005+05:30

Thermoelectrically operated fan using a candle.

( Operate a fan with the candle during power cuts/ villages where there is no power!!)

Innovation at its best.

W engines - what does the W stand for?

2013-12-04T18:34:00.001+05:30

W engines - what does the W stand for?
......................................................................
With the aim of building even more compact units with a large number of cylinders, the design features of the V and VR engines were combined to produce the W engines.
As with the V engines, the cylinders are distributed to two banks. In the W8 and W12 engines, these banks of cylinders are aligned at a V-angle of 72° in relation to one another. As in the VR engine, the cylinders within each bank maintain an angle of 15°.

When the W engine is viewed from the front, the cylinder arrangement looks like a double-V. Put the two Vs of the right and left cylinder banks together, and you get a W. This is how the name "W engine" came about.

Honing

2013-12-04T18:33:00.003+05:30

Honing :
Honing is an abrasive machining process that produces a precision surface on a metal workpiece by scrubbing an abrasive stone against it along a controlled path. Honing is primarily used to improve the geometric form of a surface, but may also improve the surface texture.
Typical applications are the finishing of cylinders for internal combustion engines, air bearing spindles and gears. There are many types of hones but all consist of one or more abrasive stones that are held under pressure against the surface they are working on.
In terms of sharpening knives, a honing steel does not actually hone knives, but simply realigns the metal along the edge.

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS

2013-12-04T18:32:00.002+05:30

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS:-

1.). What is anisotropy ?

Ans: The phenomenon of different properties in different directions is called anisotropy.

2.)What is vapour pressure and when it becomes important ?

Ans: Vapour pressure is the partial pressure created by the vapour molecules when evaporation takes place within an enclosed space. It becomes important when negative
pressures are involved.

3.)Explain absolute viscosity ?

Ans: It is the ratio of shear stress and the gradient of velocity with distance between a fixed plate and moving plate (Its unit is Pa . s).

4.)What do you understand by acoustic velocity ?

Ans: Acoustic velocity is the speed of a small pressure (sound) wave in a fluid.

Tubeless tires

2013-12-04T18:31:00.004+05:30

Tubeless tires :
Tubeless tires or tyres (in some Commonwealth Nations) are pneumatic tires that do not require a separate inner tube.
Unlike traditional pneumatic tires which use a separate inner tube, tubeless tires have continuous ribs molded integrally into the bead of the tire so that they are forced by the pressure of the air inside the tire to seal with the flanges of the metal rim of the wheel.

FIRE TUBE BOILERS

2013-12-04T18:30:00.005+05:30

FIRE TUBE BOILERS :
In fire tube boiler, hot gases pass through the tubes and boiler feed water in the shell side is converted into steam. Fire tube boilers are generally used for relatively small steam capacities and low to medium steam pressures. As a guideline, fire tube boilers are competitive for steam rates up to 12,000 kg/hour and pressures up to 18 kg/cm2. Fire tube boilers are available for operation with oil, gas or solid fuels. For economic reasons, most fire tube boilers are nowadays of “packaged” construction (i.e. manufacturers shop erected) for all fuels.

Direct injection

2013-12-04T18:29:00.003+05:30

Direct injection:-

With direct injection, the fuel is injected directly into the combustion chamber which is usually formed by a cavity in the piston crown.

This cavity is carefully shaped to promote air swirl and the direction of the injector nozzle ensures that rapid mixing of the fuel and air assists complete combustion.

Advantages - It is claimed that direct injection gives higher thermal efficiency with lower fuel consumption. This is bought about by the fact that no heat is lost or power wasted in pumping air through a restricted opening into the separate chamber or in discharging the gases from the chamber. This gives easier starting and generally this type of engine does not require a starting aid device, such as glow plugs.

Disadvantages - This kind of injection is prone to “diesel knock”.

Stress Concentration

2013-12-02T20:16:00.000+05:30

A stress concentration (often called stress raisers or stress risers) is a location in an object where stress is concentrated. An object is strongest when force is evenly distributed over its area, so a reduction in area, e.g., caused by a crack, results in a localized increase in stress. A material can fail, via a propagating crack, when a concentrated stress exceeds the material's theoretical cohesive strength. The real fracture strength of a material is always lower than the theoretical value because most materials contain small cracks or contaminants (especially foreign particles) that concentrate stress. Fatigue cracks always start at stress raisers, so removing such defects increases the fatigue strength.

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS

2013-12-02T20:13:00.002+05:30

MECHANICAL ENGINEERING JOB INTERVIEW QUESTIONS:-

1.)How many governors are needed for safe turbine operation? Why?

Ans.-Two independent governors are needed for safe turbine operation. One is an over speed or emergency trip that shuts off the steam at 10 percent above running speed (maximum speed). The second, or main governor, usually controls speed at a constant rate; however, many applications have variable speed control.

2.)How is a fly ball governor used with a hydraulic control?

Ans.-As the turbine speeds up, the weights are moved outward by centrifugal force, causing linkage to open a pilot valve that admits and releases oil on either side of a piston or on one side of a spring-loaded piston. The movement of the piston controls the steam valves.

3.)What is meant by critical speed?

Ans.-It is the speed at which the machine vibrates most violently. It is due to many causes, such as imbalance or harmonic vibrations set up by the entire machine. To minimize damage, the turbine should be hurried through the known critical speed as rapidly as possible. (Caution, be sure the vibration is caused by critical speed and not by some other trouble).

An Actuator

2013-12-02T20:12:00.001+05:30

An actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, typically electric current, hydraulic fluid pressure, or pneumatic pressure, and converts that energy into motion. An actuator is the mechanism by which a control system acts upon an environment. The control system can be simple (a fixed mechanical or electronic system), software-based (e.g. a printer driver, robot control system), or a human or other agent.

VALVE TIMING DIAGRAM

2013-12-02T20:09:00.003+05:30

VALVE TIMING DIAGRAM :-

The above diagram is for a Caterpillar series 3600 turbo charged after cooled engine. As can be seen from the timing diagram, the induction stroke commences when the inlet valve opens 10° before TDC when air is drawn into the cylinder as the piston moves down. The inlet valve closes 1° before BDC.

The air is now trapped in the cylinder and as the piston rises on the compression stroke, the air is compressed. As the air is compressed, it rises in temperature. When the piston reaches 19° before TDC, the injection of fuel commences and continues until 73° after TDC.

The heat in the compressed air ignites the fuel and combustion takes place. The gases expand forcing the piston down on the power stroke.

The exhaust valves opens at 26° before BDC and the exhaust gases commence and are discharged as the piston rises on the exhaust stroke. Most of the exhaust gases have been discharged as the piston nears TDC. However, at 10° before TDC, the inlet valve opens and air enters the cylinder and helps discharge any remaining exhaust gases until the exhaust valve closes at 3° after TDC.

The whole cycle is then repeated.

Both the exhaust valve and inlet valve are open from 10° before TDC to 3° after TDC, an overlap of 13°. This is referred to as “valve overlap” and ensures that all the exhaust gases are discharged from the cylinder and the cylinder receives a fresh charge of air to make it more efficient when combustion next takes place.

Therefore there is one power stroke for every cycle or two revolutions of the crankshaft.

Funny Facts About Engineers: [A MUST READ]

2013-12-02T20:07:00.004+05:30

Funny Facts About Engineers: [A MUST READ]

1. For engineers every course apart from engineering is easy.
2. An engineer has the power of getting up at 9.25 am and reaching the class at 9.30 am.
3. T-shirt and jeans are engineer's national dress and Maggi is the national food.
4. A normal person will fix the broken things but an engineer will first break a thing and then he would fix it.
5. An engineer can build a car, spaceship and they even can make time machine. However, he just can’t build a relationship with a girl.
6. An engineer doesn't care for the rise in price of petrol or gold but he gets mad when cigarette costs Rs.5.50 instead of 5.20.

P.S: Add your own facts and tag your friends who can relate to this.

Heat Treatment

2013-12-02T20:05:00.005+05:30

Heat Treatment:-

Heat Treatment is the controlled heating and cooling of metals to alter their physical and mechanical properties without changing the product shape. Heat treatment is sometimes done inadvertently due to manufacturing processes that either heat or cool the metal such as welding or forming.

Heat Treatment is often associated with increasing the strength of material, but it can also be used to alter certain manufacturability objectives such as improve machining, improve formability, restore ductility after a cold working operation.Thus it is a very enabling manufacturing process that can not only help other manufacturing process, but can also improve product performance by increasing strength or other desirable characteristics.

Traction control system

2013-12-02T20:04:00.000+05:30

Traction control system :-

A traction control system (TCS), is typically (but not necessarily) a secondary function of the anti-lock braking system (ABS) on production motor vehicles, designed to prevent loss of traction of driven road wheels. When invoked it therefore enhances driver control as throttle input applied is mis-matched to road surface conditions (due to varying factors) being unable to manage applied torque.

Intervention consists of one or more of the following:

>Reduces or suppress spark sequence to one or more cylinders
>Reduce fuel supply to one or more cylinders
>Brake force applied at one or more wheels
>Close the throttle, if the vehicle is fitted with drive by wire throttle
>In turbo-charged vehicles, a boost control solenoid can be actuated to reduce boost and therefore engine power.

Mechanical Engineering Interview Questions with answers

2013-12-02T15:07:00.002+05:30

Mechanical Engineering Interview Questions with answers

1. What is the difference between Technology and Engineering?

Ans. 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.

2. How to Measure Temperature in Wet Bulb Thermometer?

Ans. Wet bulb temperature is measured
in a wet bulb thermometer by covering
the bulb with a wick and wetting it with
water. It corresponds to the dew point
temperature and relative humidity.

3. What are the Advantages and Disadvantages of using LPG in Car?

Ans. Advantages
1. Complete combustion
2. Fuel saving
3. Homogenous combustion
Disadvantages
1. As complete combustion is
occurring ,more heat liberated,not
advised for long journey, engine will be
over heated 2. Installation is difficult
3. Reduce engine life efficiency

4. What is the difference between Speed and Economic Speed?

Ans. The rated speed tells us about the
maximum speed which can be achieved by
a vehicle or some other machine but the
economical speed means the speed limit
at which the machine works efficiently
with least consumption of fuel.eg-in
normal bikes(not racing),the max.speed
limit shown on speedometer is upto 120
kmph but companies always advice their
customers to drive such bikes at around
60 kmph to have maximum mileage.

5. What is Powder Technology?

Ans. Powder technology is one of the
ways of making bearing material. In this
method metals like bronze, Al, Fe are
mixed and compressed to make an alloy.

6. State all the laws of Thermodynamics?

Ans. There are three laws of the
thermodynamics. First Law: Energy can
be neither created nor destroyed. It
can only change forms. In any process
in an isolated system, the total energy
remains the same. Second Law: When
two isolated systems in separate but
nearby regions of space, each in
thermodynamic equilibrium in itself, but
not in equilibrium with each other at
first, are at some time allowed to
interact, breaking the isolation that
separates the two systems, and they
exchange matter or energy, they will
eventually reach a mutual
thermodynamic equilibrium. The sum of
the entropies of the initial, isolated
systems is less than or equal to the
entropy of the final exchanging
systems. In the process of reaching a
new thermodynamic equilibrium, entropy
has increased, or at least has not
decreased. Third Law: As temperature
approaches absolute zero, the entropy of
a system approaches a minimum.

LATEST MECHANICAL ENGINEERING RESEARCH NEWS UPDATE (November 30, 2013)

2013-12-02T15:01:00.002+05:30

LATEST MECHANICAL ENGINEERING RESEARCH NEWS UPDATE (November 30, 2013)

Liquid Fuel Made from Carbon Dioxide for the First Time.

Details - On Iceland’s Southern Peninsula, a new facility constructed next to a geothermal power plant has managed to successfully demonstrate the direct conversion of carbon dioxide into methanol fuel, perhaps for the first time.

Methanol can be used for a variety applications, including making paints. The facility belongs to Carbon Recycling International, a company determined to prove that converting CO2 into methanol does not have to be a very complex and energy-intensive process. The installation takes its supplies from the geothermal power plant next door, thus reducing its neighbor's emissions. Though this method works, it is unlikely that it will applied anywhere else in the world any time soon. In order for this approach to be effective, a conversion facility needs to be built in an area where both electrical power and carbon dioxide come cheap. Iceland has a medium cost of just four cents per kilowatt-hour of electricity.

Additionally, the geothermal power plants releases highly concentrated streams of carbon, as opposed to fumes, like coal-fired power plants do. This allows the conversion facility to capture and separate carbon with lower overall costs, and with fewer requirements in terms of technology and power consumption, Technology Review reports.

2 & 4 Stroke engine Difference

2013-12-01T00:11:00.001+05:30

2 & 4 Stroke engine Difference:

In case of two stroke engine, rotation of crank shaft will be power stroke for every one rotation. During compression stroke, fuel will flow towards the crank case(suction) and during power stroke, exhaust will emit the burnt fuel through the transfer ports.

Glowplug indicator light

2013-12-01T00:09:00.003+05:30

In older generation diesel-engine vehicles, unlike in a gasoline-engine vehicle, the operator did not simply turn the key to the "start" position and have the engine immediately start. Instead, the operator turned the key to the "on" position for a long duration; the glowplug relay switches the glowplugs on, and a light (see picture at right) on the instrument cluster illuminates. This process is called "pre-heating" or "glowing". According to Bosch: "Older engines used a glow period of up to 21 seconds whereas more modern engines use around a 6 to 8 second heat period and provide after glow at a reduced voltage"

Types of suspension systems.

2013-12-01T00:08:00.001+05:30

Types of suspension systems.