Fuel additives are compounds used to enhance the quality and efficiency of the fuels. Sometimes, the additive is injected into the gasoline itself; at other times, the fuel additive is added from outside. The aim of fuel additives is to improve or maintain the optimum performance of the engines.

Fuel additives may boost the octane level of the gasoline. This helps the engine derive more power from the same amount of gas. This offers the ability to travel longer with the same amount of fuel.

Engine maintenance is another task of fuel additives. With these types of additives, the focus is on preventing the gathering of sludge and other unwanted deposits in different areas of the engine.

Because of lesser buildup of sludge in the lines and in the various moving parts on the motor, the
engine life is effectively prolonged.

Types of additives range wide and include metal deactivators, oxygenates, corrosion inhibitors and antioxidants.

For a true rolling of a four wheeled vehicle moving on a curved track, the straight lines drawn through all the wheel axes must intersect at the instantaneous centre.

The Ackermann steering uses the two front steered wheels pivoted at the finishing points of an axle-beam. There is an original Ackermann linkage which usually has parallel set track-rod-arms ensuring that both steered wheels swivel equally. Consequently, the projection lines do not meet at one point.
In case both of the front wheels are allowed follow their own natural paths, they would ultimately

converge and come across each other. As the vehicle will have to move along one mean path, so both of the wheel tracks would conflict which may cause tyre slip and tread scrub.

Therefore a modified linkage is used at inclined track-rod arms so that the inner wheel swivels about the king-pin a little bit more than the outer wheel.

Acceptance testing is basically done by the user or customer to establish confidence in the system. In case of automobiles, the vehicle is checked whether it meets certain standards in terms of safety and performance etc.

The types of acceptance testing applied to automobiles are:
The User Acceptance test: is done to test the functionality to validate the fitness-for-use of the system by the user. User acceptance test is done by the users and application managers.

The Operational Acceptance test: is also known as Production acceptance test. It validates whether the system meets the standards for operational reasons. In most of the organization the operational acceptance test is performed by the administrators before the vehicle is released for sale.

Compliance acceptance testing: is done because the governmental, legal or safety regulations must be adhered to.

Various other testing including safety and mobility may also be done as acceptance testing from time to time for automobiles.

For an automobile to get smooth acceleration, advancement in the timing and an increase in fuel flow are required. There is a vacuum distributor in automobile carburettor that senses when you open the throttle and then it provides the extra advance timing. The accelerator pump provides the extra fuel needed for acceleration.

The accelerator pump is usually connected by to the accelerator; when momentary acceleration is required, the pump squirts fuel directly into the carburettor for  increasing the amount of fuel-to-air concentration.

Most carburettors contain a small bent brass pipe pointing straight down it-- it is called the delivery tube. When the throttle arm is pulled firmly, a squirt of fuel flows into the carburettor right from the delivery tube.

This increased fuel increases the power of the engine and the automobile gets an instant acceleration. The accelerator pump must be adjusted suitably for optimum performance, and it is wrong to believe that the more fuel the pump injects, the better it is for the vehicle.

An automobile air conditioner has the following:

Compressor: This is the heart of your a/c system. The compressor intakes the refrigerant (the gas) and pressurizes it so that it cools the air. An engine belt runs it.

Condenser: The condenser is like a miniature. The condenser has its own electric cooling fan, too. The hot, compressed air passes through the condenser and gets cooler.

Evaporator: The evaporator does just the opposite task as the condenser. When the cooler liquid passes through its tubes, air is forced through and gets really cold. When it warms, the refrigerant starts turning back into a gas.

Thermal Expansion Valve: To save from excess cooling, the a/c system has a valve that controls the flow of super-cool refrigerant to the evaporator.

Drier or Accumulator:  The compressor compresses the gas form of your refrigerant. However, some liquid could make it back that far. The drier catches this liquid before it can damage the compressor.

A bumper is a kind of structure attached in the front and rear of an automobile to absorb impact in a minor collision, ideally minimizing repair costs. Bunpers are standard equipments that are commonly used in vehicles nowadays.

Bumpers also have two major safety functions: diminishing height mismatches between vehicles, and safeguarding pedestrians from major injury.

The bumper structure on modern automobiles usually have a plastic cover over a reinforcement bar made up of steel, aluminum, fiberglass composite, or plastic.

Bumpers save other vehicle components by dissipating the impact of kinetic energy generated in a collision. This energy is a function of vehicle mass and velocity squared. In formula form, it is given by  which suggests that a vehicle protecting the components at 5 km/ hr must be four times stronger than the bumper that protects at a 2.5 km/hr.

A shock absorber or shock damper is a mechanical or hydraulic device designed to absorb and decrease the impact of a shock impulses. Shock absorbers convert the kinetic energy of the shock to some other form of energy to dissipate it. A shock absorber is a type of dashpot.

Most used in vehicles, shock absorbers reduce the effect jerks, resulting in improved ride quality and vehicle handling.

There are two major types of shock absorbers: Twin tube and Mono tube.
Twin tube: Also called a "two-tube" shock absorber, this device has two nested cylindrical tubes, the inner, "working tube" and an outer "reserve tube". Twin tube shock absorbers can be basic, gas charged, position sensitive, acceleration sensitive or coilovers.

Mono tube: the mono-tube shock absorber is a gas-pressurized shock absorber that also comes in a coilover format. It is made up of only one tube, the pressure tube, however, it has two pistons.

Sandpaper or Glasspaper are a type of coated abrasive that consists of sheets of paper or cloth with abrasive material affixed to one face. Nowadays, sand or glass is not used.

Sandpaper is produced in different sizes and is used to remove unwanted material from surfaces, either to make them smoother (in painting and wood finishing), to remove a layer of material (e.g. old paint), or to make surface rougher (in gluing).

Backing:  Backing for sandpaper can have clothes (cotton, polyester, and rayon), PET film, and "fibre", or rubber apart from the paper.

Material: Garnet, emery, aluminium oxide, silicon carbide, alumina-zirconia, Chromium(III) oxide, ceramic aluminium oxide can also be used in sandpapers.

Bonds: Different adhesives, such as Hide glue, are used to bond the abrasive to the paper. Waterproof sandpapers use resin bond and a waterproof backing.

Open coat sandpapers have particles that are separated from each other and it is more flexible.

Abrasive Disc is a disc of abrasive material that rotates in a tool such as a sander. Abrasive discs are used usually for use in stock removal, blending, finishing and polishing applications.

Abrasive discs use the combination of several minerals, resin systems and backings for better functionality. This combination results in a wide range of products to meet various requirements for use on most wood, metal, composite, gel coat, painted substrates or hard‑to‑grind materials.

The discs are generally manufactured using a composite material with coarse-particle aggregate pressed and attached together using a cementing matrix to give it a solid, circular shape. Depending on the intended usage of the disc, various forms and cross sections are available.

Abrasive Discs may also be built using a solid steel or aluminium disc with particles bonded to the surface. Most abrasive discs are artificial composites of artificial aggregates, but initially natural composite stones (millstones) were also used.

An Abrasive Cleaner is a type of mechanical cleaner that physically removes dirt, stains and tarnish the surface.  They are made up of particles or physical abraders and use friction to remove the dirt stains etc. Physical abraders include sandpaper, steel wool, scrubbing pads, etc.  Abrasiveness usually depends or coerciveness of the used material.

Depending on the harshness, there are three types of Abrasive Cleaners.

Mild Abrasives such as fine plastic mesh pads, soft brass wool, nylon coated sponges, rotten-stone and whiting are often used to clean pots and pans, interiors of ovens, and drip pans.

Examples of Moderate Abrasive Cleaners are fine pumice and fine steel wool. Steel wool has grades from 0000-super fine, 000-extra fine, 00-very fine, 0-fine, 1-medium, 2-medium coarse and 3-0 coarse.

Strong Abrasives are the strongest among abrasives. Examples include medium and coarse steel wool, metallic mesh cloths and balls, metallic brushes, coarse pumice, and sand/silica etc.

Newton's Law of Viscosity gives the relationship between the shear stress and the shear rate or the velocity gradient of a liquid that is subject to a mechanical force.

The law is not universal in its application.  It is applicable to some liquids while other liquids do not obey it.

Newton's Law of Viscosity can be mathematically described as

t =  m dv/dy

where t = shear stress
           dv/dy is the velocity gradient

Liquids which obey Newton's Law of Viscosity are called Newtonian liquids.  Liquids whose response cannot be described by this law are called Non-Newtonian Liquids.

A Newtonian liquid is one in which the viscosity of the liquid is constant regardless of the stress applied.  That is, the viscosity of the liquid is the same if it is left alone or agitated vigorously.

In other words, Newtonian liquids obey Newton's law of viscosity which states that the shear stress is proportional to the rate of strain.

Water is a common example of a Newtonian liquid.  The viscosity of water is same whether it is still or in an agitated state.  In contrast, a solution of water and corn starch will be liquid when still but will become highly viscous when agitated.

Liquids in which the viscosity changes in response to the application of stress are called non-Newtonian liquids.

Rheology is the science of the flow of matter, particularly in the liquid or the semisolid state.  It is a subject of interest when designing pumps.  Rheology can help describe the behaviour of materials such as slurries and pastes.

The term Rheology is formed from two Greek works, "Rheo" for flow and "logia" for study. It is based on the assumption that "everything flows" or "Panta Rei", a statement attributed to Heraclitus, a philosopher in ancient Greece.Rheology can also be described as the study of the behaviour of matter when subject to  a deforming load.

In Rheology, flow is considered to be an irreversible deformation of matter as the original state of the fluid or the semi-solid cannot be attained again.

Rheology has applications in the food industry, in pharmaceuticals and in chemical industries.

Metering pumps are special pumps which are used to deliver a liquid at a specific flow rate in a specific time.  Metering pumps are used for dosing chemicals in industrial processes at a specific quantity.

The quantity and duration is often controlled by a computer.

Metering pumps are positive displacement pumps which can deliver output at high pressures. The pump is usually driven by a piston.

For sensitive liquids which require sterility and for corrosive liquids, the pump is ideal as it does not come in contact with the liquid.  A diaphragm acts as the interface between the piston and the liquid.

Metering pumps can also be designed as gear pumps.

A diaphragm is a special type of pump which uses a diaphragm to create pressure.  The diaphragm pump consists of a container with an inlet and outlet valves.  The top of the container is covered with the diaphragm.

The diaphragm is operated by an external mechanism which moves the diaphragm up and down.  When the diaphragm is pulled up, low pressure is created and the liquid is drawn inside the pump.  When diaphragm is pushed down, the fluid inside is pressurized and released through the outlet valve.

A salient feature of the diaphragm pump is that the fluid does not come in contact with the pump components.  Diaphragm pumps are used in the field of medicine where they can be used to construct artificial hearts and in dialysis.

They are also used widely in the food processing industry.

Another common application is in aquariums.  Aquarium pumps which provide air to aerate aquariums are a type of diaphragm pumps.

Plunger Pumps and Piston pumps work on the same principle.  They both draw a fixed volume of liquid through the inlet and pressurize the liquid and then release the liquid.

The difference lies in the construction.  In Piston pumps, the seal which prevents leakage moves with the piston.  In plunger, the seal is stationary and the plunger alone moves.

This enables the generation of very high pressure.  Plunger pumps can build pressures of the order of MegaPascals.  Plunger Pumps are used in high pressure applications.

A plunger pump is a positive displacement pump.  In a plunger pump, the plunger moves up and down a cylinder.

When the plunger moves up the cylinder, a low pressure is created in the cylinder.  The fluids is drawn by the low pressure by means of non return valves in the inlet of the pump.

When the plunger moves down, the increased pressure closes in the non-return valves in the inlet.  The liquid is pressurized as the plunger moves downwards.  This high pressure opens the outlet valve and the liquid is ejected at high pressure.

Plunger Pumps can be used at high pressure because of their robust and simple design.  

Centrifugal pumps need to be primed separately.  The priming can be manual or through a separate priming arrangments

Positive displacement pumps are self priming as they develop a low pressure which can draw the fluid inside.

Flow Rate
Centrifugal Pumps have a flow rate which is dependent on the discharge pressure

Positive Displacement pumps have a constant flow rate regardless of the pressure

Viscous Fluids
Centrifugal pumps cannot handle viscous fluids due to increased friction between the impeller and the liquid.

Positive displacement pumps can handle viscous fluids.

Centrifugal pumps have lower efficiency as the viscosity increases

Positive displacement pumps have high efficiency as the viscosity increases

Method of operation
Centrifugal pumps build pressure by imparting velocity to the liquid and then converting it into pressure.

Positive displacement pumps develop pressure by drawing a fixed amount of liquid and pressurizing it.

A positive displacement pump is a pump which draws a fixed amount of the liquid from the inlet and discharges it in the outlet at high pressure.

Positive displacement pumps have an expanding cavity in the inlet and a decreasing cavity near the inlet.  Positive displacement pumps have constant volume.  The pumps deliver a constant flow regardless of the discharge pressure.  The pressure depends on the speed of the pump.

Positive displacement pumps can be further classified into reciprocating pumps, rotary pumps, etc.

Positive displacement pumps should never be operated with the outlet closed. Since the pump works on a fixed volume of liquid,  the pump can get seriously damaged if it is accidentally operated with the outlet closed.

A special pressure relief valve is provided for protection against excess pressure.

Cavitation refers to the erosive action on the pump impeller and casing by the explosion of bubbles which form in the medium.

When the liquid passes through the impeller, the pressure drops in certain areas, this causes the liquids to drop below the vapor pressure.  As a result, bubbles are formed.  When these bubbles break, the energy released can remove small amounts of materials from the impeller and the casing.

Cavitation can cause the housing of the pump to fail.  In some instances, it can cause damage to the impeller.  A damaged impeller can get unbalanced and cause high vibration.  The outflow of the pump will also be affected

Cavitation in Pumps is classified into two types

Suction Cavitation
In suction cavitation, inadequate flow into the pump from the suction side due to blocked filters can cause low pressure in the eye of the impeller, this causes bubbles to form.  These bubbles pass to the discharge side where they encounter high pressure.  This causes the bubbles to implode releasing energy which can damage the impeller.

Discharge Cavitation
This occurs due to reduced outflow from the pump.  If the output of the pump is reduced, the pressure increases.  The liquid is unable to exit the pump and recirculates within the pump.  This high speed flow causes a vacuum between the liquid and the wall of the pump housing.  This causes bubbles to form and damage the inner surface of the casing.

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