Posted: 19 Feb 2011 04:42 AM PST

Hello everyone ever wonder about oils?
Oils are gift of nature to mankind.We sometimes use oils as lotions.But I am talking about lubricating oils.Don't try to use them as lotions.:mrgreen:
Anyways jokes apart.Actually I want to discuss the various properties of lubricating oils and their general types.
1.Viscosity
Viscosity is the property of flow of any liquid to flow.Simply speaking,
A low viscosity oil is very thin and flows readily.
A high viscosity oil is very thick and resists flow.
So it is actually difficult to define a good lubricating oil.It depends under what conditions you use it.To be more scientific there are two types of viscosities

a) Dynamic viscosity : also called as absolute viscosity, the more usual one (typical units Pa·s, Poise, P); and

b) Kinematic viscosity: is the dynamic viscosity divided by the density (typical units m2/s, Stokes, St).

2.Viscosity index:
This is the rate of change of viscosity with respect to temperature.So a single viscosity oil is very thick at low temperatures and very thin at high temperatures.

3.Viscosity numbers:
As any other things oils also have various grades.As the oils used in winter conditions are thick hence the two grades
1.winter
2.Other than winter
the various grades are SAE 0W, SAE 5W, SAE 10W...and so on.As you can easily guess W stands for winter.

4.Multiple-Viscosity oils:
In many applications the changing of viscosity with respect to temperature is undesirable.So we have viscosity index improver.Most automotive manufacturers recommend multi viscosity oils for automobiles.

5.Resistance to carbon formation and oil oxidations:
When the temperature increases,we may face this problem so we need the resistance to it.

6.Corrosion and rust inhibitors:
Additives are put in oils so that oils should protect the parts from rusting in case they come in contact of water.

7.Foaming resistance:
Whenever the moving part moves, it may churn the oil so that it will foam.This reduces the lubricating property of oil.To prevent it we may have the following
1.Additives or
2.A baffle in oil pan and
3.A windage tray between pan and cylinder.

8.Detergent-Dispersants:
These additives act as a soap and they carry dirt and carbon away from oil.

9.Extreme pressure resistance:
The oils also prevent the parts from extreme pressure.As in case of bearings and valves.

10.Energy conserving oils:
These oils reduce fuel consumption when compared to engine operation with a specified engine oil.
There are two types.
EC1 and EC2.EC2 oils provide much better fuel economy than EC1 oils.

11.Synthetic oils:
As modern sciences are advancing we have better oils which are artificially obtained.They are made from certain Carbon compounds and alcohols.
The advantages include
a)They tolerate heat better
b)Produce less sludge
c)Less carbon deposits

So it was all I could do for you.Everything rests with you people.Please correct me wherever I am wrong.

Posted: 19 Feb 2011 03:43 AM PST

The device which mixes air and fuel and supplies the engine with this air-fuel mixture is called a carburettors.It is connected before the engine.A simple carburettor consists of three basic parts.
1.Air horn
2.Float bowl and
3.A throttle body
Now, there is one type of carburettor called as fixed-venturi carburettor.The so called venturi is nothing but the partial vacuum produced due to air flow in carburettor.The region where this partial vacuum is produced is called venturi.The venturi is a small and restricted space.
The air flows in carburettor because the pressure outside is atmospheric while that inside is below atmospheric pressure.
The fuel tank supplies fuel to float bowl with the help of a pump.
Because of the pressure difference the fuel is pushed through the nozzle.The fuel then mixes with the incoming air.
The throttle valve is a component which allows the air to enter in the carburettor.
The more the vacuum generated the more air flows inside.
There is also a type of carburettor called as variable venturi carburettor.So by the name can you guess its working???
:cean:

Basics of Civil Engineering......

Posted: 18 Feb 2011 10:25 PM PST

Hi :cean:

I thought it would be great if we can share the basic concepts, so that aspiring Engineers would understand better about the things they Study. I searched for such thread couldn't find any, and i found many are interested with their own doubts related to some assignment oriented topics. So i thought such thing may help them to understand better. If am wrong do correct.

Come on Civil Engineers, start Knowledge Transfer, don't be selfish.

Note: Do share basic concepts, methods, thumb rules etc. in brief, so that the person
making use wouldn't feel bored.

Crazy Engineers .CoM

Saturday, February 19, 2011

CrazyEngineers Forum - Mechanical & Civil Engineering

CrazyEngineers Forum - Mechanical & Civil Engineering

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