MECHANICAL ENGINEERING PROJECTS

Seminar Topic on Four wheel steering system

Four-wheel steering, 4WS, also called rear-wheel steering or all-wheel steering, provides a means to actively steer the rear wheels during turning maneuvers. It should not be confused with four-wheel drive in which all four wheels of a vehicle are powered. It improves handling and helps the vehicle make tighter turns. Production-built cars tend to understeer or, in few instances, oversteer. If a car could automatically compensate for an understeer /oversteer problem, the driver would enjoy nearly neutral steering under varying conditions. 4WS is a serious effort on the part of automotive design engineers to provide near-neutral steering.  The front wheels do most of the steering. Rear wheel turning is generally limited to half during an opposite direction turn. When both the front and rear wheels steer toward the same direction, they are said to be in-phase and this produces a kind of sideways movement of the car at low speeds. When the front and rear wheels are steered in opposite direction, this is called anti-phase, counter-phase or opposite-phase and it produces a sharper, tighter turn.

ADVANTAGES OF 4WS

1. The vehicle’s cornering behavior becomes more sta­ble and controllable at high speeds as well as on wet or slippery road surfaces.
2. The vehicle’s response to steering input becomes quicker and more precise throughout the vehicle’s entire speed range.
3. The vehicle’s straight-line stability at high speeds is improved. Negative effects of road irregularities and crosswinds on the vehicle’s stability are minimized.
4. Stability in lane changing at high speeds is improved. The vehicle is less likely to go into a spin even in situ­ations in which the driver must make a sudden and relatively large change of direction.
5. By steering the rear wheels in the direction opposite the front wheels at low speeds, the vehicle’s turning circle is greatly reduced. Therefore, vehicle maneu­vering on narrow roads and during parking becomes easier.

 

Catalytic converter for cars

Millions of cars or the road means only one thing, an excellent source for air pollution. The amount of pollution that all cars produce together can create big problems. The amount of pollution that all cars produce together can cause big problems. Government created laws that restrict the amount of pollution that cars produce to solve it. Auto makers have made many improvements to car engines and fuel systems to keep up with these laws. In 1975, an interesting device called catalytic converter was created. The device, converts harmful pollutants into less harmful emissions before they ever leave the car’s exhaust system.

The exhaust from the combustion in a car engine is comprised of six main ingredients:

1. Nitrogen gas, Carbon dioxide and water vapor are the three of the main emissions. These gases do not cause damage to the atmosphere.
2. Carbon Monoxide, other hydrocarbons and Nitrogen Oxides result in a majority of the pollution caused by cars.

• Carbon monoxide is a colorless and odorless gas that can kill you if too much is inhaled
• Hydrocarbons are produced during incomplete combustion and these hydrocarbons can be broken down by the sun, creating ground level Ozone, also known as smog.
• Nitrogen Oxides can cause acid rains.

Catalytic convertors are designed to reduce these last three emissions.

Construction:

The core is often a ceramic/stainless steel foil honeycomb.

-          Increases the amount of surface area

-          Support the catalyst.  Also called “catalyst support”.

A wash coat is used to make converters more efficient because a mixture of silica and alumina will form a rough and irregular surface which leads to more surface area. Therefore, more places for active precious metal sites. The catalyst is added to the wash coat before applied to the core.

Platinum is the most active catalyst and is widely used. Other materials such as palladium and rhodium have also been used.

 

 

 

Hybrid vehicles

 

The dictionary defines hybrid as something of mixed origin. A hybrid vehicle is one that combines a smaller than normal internal combustion gasoline engine with an electric motor. An engine that combines two or more sources of power is called a hybrid engine.

Typical features in a hybrid include the following:
• Produces much less power than an average
• Produces much less pollution than standard gasoline cars
• Usually constructed of ultra light weight materials like carbon fiber or aluminum to overcome the power gap.
• Generally designed to be more aerodynamic than most cars, allowing them to “slice” through the air instead of pushing it out of the way
• A process called regenerative braking is employed to store the kinetic energy generated by brake use in the batteries, which in turn will power the electric motor.
Power usage:
• Electric power is used at starts and stops, low speeds (generally below 25 km/hr)
• Gasoline engine comes to play at cruising or highway speeds

There are two types of gasoline-electric hybrids:
• Parallel hybrid:
Gasoline engine and electric motor work together to move the car forward
• Series hybrid
Gasoline engine either directly powers an electric motor that powers the vehicle, or changes batteries.

Hybrids achieve improved efficiencies using several approaches:
• Employ regenerative braking to recover energy and downsize or right size the engine or primary power source.
• Control the engine or primary power source to operate more efficiently and/or work more often in a more efficient range.

Air Cars

 

We do it every day without thinking. Start the engine, drive around, fill up with fuel, pay a lot of money and pollute the atmosphere some more! But, it doesn’t have to be that way, many alternative sources of fuel are being developed.

Science fiction novelist Jules Verne had predicted that cars would one day run on air.  Guess what the future of fuel is? You guessed it right, its air!  Think about a car that runs on air. The air we breathe, the air that is for free. Imagine, it costs nothing to fill up your car with gas, and that gas also happens to be the same gas that fills our lungs with every breath!

The future of transportation will soon be whooshing down the road in the form of an unparalleled “green” earth- friendly technology that everyone will want to get their hands on as soon as they can: The Air Car. It is hard to believe that compressed air can be used to drive vehicles. However that is true and the “air car”, as it is popularly known, has caught the attention of researchers worldwide.