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ABSTRACT
Self-inflating tyres are designed to constantly maintain tyre pressure at the proper level.
Self-inflating systems are designed more for the slow leaks and for optimizing performance and safety than for keeping a vehicle moving on a tyre that will no longer hold air.
Driven by studies that show that a drop in tyre pressure by just a few PSI can result in the reduction of gas mileage, tyre life, safety, and vehicle performance, we have developed an automatic, self-inflating tyre system that ensures that tyres are properly inflated at all times. Our design proposes and successfully implements the use of a centralized compressor that will supply air to all four tyres via hoses and a rotary joint fixed between the wheel spindle and wheel hub at each wheel. The rotary joints effectively allow air to be channeled to the tyres without the tangling of hoses. With the recent oil price hikes and growing concern of environmental issues, this system addresses a potential improvement in gas mileage; tyre wear reduction; and an increase in handling and tyre performance in diverse conditions.
INTRODUCTION
About 80 percent of the cars on the road are driving with one or more tyres under inflated . Tires lose air through normal driving (especially after hitting pot holes or curbs), permeation and seasonal changes in temperature. Tyres lose one or two psi (pounds per square inch) each month in the winter and even more in the summer. It cannot be told that tyres are properly inflated or not by looking at them. Tyre pressure gauge is used for this. Not only is under inflation bad for tyres, but it's also bad for gas mileage, also affects the way car handles and is generally unsafe.
When tyres are under inflated, the tread wears more quickly. This equates to 15 percent fewer miles which can be drived on them for every 20 percent that they're under inflated. Under inflated tires also overheat more quickly than properly inflated tires, which cause more tire damage.
2.1. GOALS OF SITS:
Tire-inflation systems have three general goals:
• Detect when the air pressure in a particular tire has dropped - This means they have to constantly (or intermittently) monitor the air pressure in each tire.
• Notify the driver of the problem
• Inflate that tire back to the proper level - This means there has to be an air supply as well as a check valve that opens only when needed.
2.2. UNIQUENESS OF THE PROJECT:
The dynamically-self-inflating tyre system would be capable of succeeding as a new product in the automotive supplier industry. It specifically addresses the needs of the consumers by maintaining appropriate tyre pressure conditions for:
• Reduced tyre wear
• Increased fuel economy
• Increased overall vehicle safety
Because such a product does not currently exist for the majority of passenger vehicles, the market conditions would be favorable for the introduction of a self- inflating tyre system.
For further development of this product, we recommend increasing the capability of the system by adding the following features:
• Pressure adjustment based on increasing vehicle speed
• Pressure adjustment based on increasing vehicle load
• Adaptability for recreational use (inflating rafts, sports balls, etc.)
• Implementation of interactive display
• Creation of universal design for aftermarket use
. HOW TYRES SUPPORT A CAR
You may have wondered how a car tyre with 30 pounds per square inch ( psi ) of pressure can support a car. This is an interesting question, and it is related to several other issues, such as how much force it takes to push a tyre down the road and why tyres get hot when you drive (and how this can lead to problems).
The next time you get in your car, take a close look at the tyres. You will notice that they are not really round. There is a flat spot on the bottom where the tyre meets the road. This flat spot is called the contact patch.
If you were looking up at a car through a glass road, you could measure the size of the contact patch. You could also make a pretty good estimate of the weight of your car, if you measured the area of the contact patches of each tyre, added them together and then multiplied the sum by the tyre pressure. Since there is a certain amount of pressure per square inch in the tyre, say 30 psi, then you need quite a few square inches of contact patch to carry the weight of the car. If you add more weight or decrease the pressure, then you need even more square inches of contact patch, so the flat spot gets bigger.
You can see that the under inflated/overloaded tyre is less round than the properly inflated, properly loaded tyre. When the tyre is spinning, the contact patch must move around the tyre to stay in contact with the road. At the spot where the tyre meets the road, the rubber is bent out. It takes force to bend that tyre, and the more it has to bend, the more force it takes. The tyre is not perfectly elastic, so when it returns to its original shape, it does not return all of the force that it took to bend it. Some of that force is converted to heat in the tyre by the friction and work of bending all of the rubber and steel in the tyre. Since an under inflated or overloaded tyre needs to bend more, it takes more force to push it down the road, so it generates more heat.
Tyre manufacturers sometimes publish a coefficient of rolling friction (CRF) for their tyres. You can use this number to calculate how much force it takes to push a tyre down the road. The CRF has nothing to do with how much traction the tyre has; it is used to calculate the amount of drag or rolling resistance caused by the tyres. The CRF is just like any other coefficient of rolling friction: The force required to overcome the friction is equal to the CRF multiplied by the weight on the tyre. This table lists typical CRF for several different types of wheels.
TYRE-INFLATION BASICS
About 80 percent of the cars on the road are driving with one or more tyres underinflated. Tyres lose air through normal driving (especially after hitting pot holes or curbs), permeation and seasonal changes in temperature. They can lose one or two psi (pounds per square inch) each month in the winter and even more in the summer. And, you can't tell if they're properly inflated just by looking at them. You have to use a tyre-pressure guage. Not only is underinflation bad for your tyres, but it's also bad for your gas mileage, affects the way your car handles and is generally unsafe.
2.3.2PROBLEMS WITH TYRES
When tyres are under-inflated, the tread wears more quickly. According to Goodyear, this equates to 15 percent fewer miles you can drive on them for every 20 percent that they're underinflated. Underinflated tyres also overheat more quickly than properly inflated tyres, which cause more tyre damage. The faded areas below indicate areas of excessive tread wear.
Because tyres are flexible, they flatten at the bottom when they roll. This contact patch rebounds to its original shape once it is no longer in contact with the ground. This rebound creates a wave of motion along with some friction. When there is less air in the tyre, that wave is larger and the friction created is greater and friction creates heat. If enough heat is generated, the rubber that holds the tyre's cords together begin to melt and the tyre fails. Because of the extra resistance an underinflated tyre has when it rolls, your car's engine has to work harder. A statistics show that tyres that are underinflated by as little as 2 psi reduce fuel efficiency by 10 percent. Over a year of driving, that can amount to several hundred dollars in extra gas purchases.
2.4.CLASSIFICATION OF TYRE INFLATION SYSTEM
2.4.1 SELF INFLTING TYRE SYSTEM;
The SIT system is based on highly reliable and proven peristaltic pump principles. It uses the weight and motion of the vehicle to inflate the tire as needed, sourcing air from the outside atmosphere. The whole system consists of only two components – a tube chamber functioning as a peristaltic pump for the tire and a pressure management device to control the inflation. The peristaltic tubing is located longitudinally between the rim and the tire wall and copies almost the whole perimeter of the rim. Normal tire deformation caused by the weight of the vehicle creates a closure of the tubing at its lowest point. As the tire moves against the road this closure pushes the air contained inside the tubing into the tire and simultaneously it pulls outside air back into the tubing. As a result, the tire is inflated with the contents of the tubing with each wheel revolution until it reaches its desired pressure. Tests conducted on a regular passenger car wheel have proven that the forces between the deformed tire wall and the rim are sufficient to generate significantly higher pressure than what is needed for tire inflation.
2.4.2. CENTRAL TYRE INFLATION SYSTEM (CTIS)
The idea behind the CTIS is to provide control over the air pressure in each tyre as a way to improve performance on different surfaces. For example, lowering the air pressure in a tyre creates a larger area of contact between the tyre and the ground and makes driving on softer ground much easier. It also does less damage to the surface. This is important on work sites and in agricultural fields. By giving the driver direct control over the air pressure in each tyre, maneuverability is greatly improved.
Another function of the CTIS is to maintain pressure in the tyres if there is a slow leak or puncture. In this case, the system controls inflation automatically based on the selected pressure the driver has set.
There are two main manufacturers of the CTIS: U.S.-based Dana Corporation and France-based Syegon (a division of GIAT). Dana Corporation has two versions, the CTIS for military use (developed by PSI) and the Tyre Pressure Control System (TPCS) for commercial, heavy machinery use. In the next section, we'll take a look at the inner workings of a basic CTIS setup.
2.5. PARTS OF SELF INFLATING TYRE SYSTEM:
1. Portable compressor
2. Pressure sensor
3. Rotary joint
4. Plumber block bearings
5. Tyre
6. Battery
7. Polished steel shaft
8. Hoses
9. Stand
2.6 APPLICATIONS OF THE PROJECT
The Dynamically Self-Inflating Tyre System can be used in almost all types of vehicles but would be most beneficial for the following categories:
1. Military Vehicles
2. Cargo Trailers
3. Trucks
4. Ambulances
5. Fire Trucks
6. Passenger Vehicles
METHODS OF REDUCING ROTOR SPEED:
The following methods are used to reduce the speed of an impulse turbine
1. Velocity compounding
2. Pressure compounding
3. Velocity-pressure compounding
(i). Velocity compounding
Steam is expanded through stationary nozzle from the boiler to condensor pressure.So the pressure in the nozzle
drops, the kinetic energy of steam increases due to increase in velocity.This energy is absorbed by row of moving
blades.The steam flows through fixed blades.The function of these blades is to redirect the steam flow without altering its
velocity to the following next row of moving blades where again work is done on them.This method has the advantage of less initial cost, but its efficiency is low.
(ii). Pressure compounding
Figure shows rings of fixed nozzles incorporated between the rings of moving blades.The steam at boiler pressure enters the first set of nozzles and expands partially.The kinetic energy is absorbed by moving blades.The steam then expands partially in second set of nozzles where pressure again falls and valocity increases,the KE is then absorbed by second ring of moving blades.This is repeated in stage 3 and stem finally leaves the turbine at low velocity and pressure.
Pressure-Velocity compounding:
This method of compoundin is the combination of two previously discussed methods.The total drop i steam pressure is divided into stages and velocity obtained in each stage is also compounded.The rings of nozzles are fixed at the beginning of each stage and pressure remains conststant during each stage.This method of compounding is used in curits and moore turbine.
2(6). OPERATING AND MAINTENENCE:
When warming up a steam turbine for use, the main stream stop
valves (after the boiler) have a bypass line to allow superheated steam to slowly bypass the valve and proceed to heat up the lines in the system along with the steam turbine. Also, a turning gear is engaged when there is no steam to the turbine to slowly rotate the turbine to ensure even heating to prevent uneven expansion.
After first rotating the turbine by the turning gear, allowing time for the rotor to assume a straight plane (no bowing), then the turning gear is disengaged and steam is admitted to the turbine, first to the astern blades then to the ahead blades slowly rotating the turbine at 10 to 15 RPM to slowly warm the turbine.
Problems with turbines are now rare and maintenance requirements are relatively small. Any imbalance of the rotor can lead to vibration, which in extreme cases can lead to a blade letting go and punching straight through the casing. It is, however, essential that the turbine be turned with dry steam - that is, superheated steam with minimal liquid water content. If water gets into the steam and is blasted onto the blades (moisture carryover), rapid impingement and erosion of the blades can occur leading to imbalance and catastrophic failure.
Also, water entering the blades will result in the destruction of the thrust bearing for the turbine shaft. To prevent this, along with controls and baffles in the boilers to ensure high quality steam, condensate drains are installed in the steam piping leading to the turbine.
2(8). SUPPLY AND EXHAUST CONDITIONS:
These types include condensing, no condensing, reheat, extraction and induction. No condensing or back pressure turbines are most widely used for process steam applications. The exhaust pressure is controlled by a regulating valve to suit the needs of the process steam pressure. These are commonly found at refineries,pulp and paper plants, and desalination facilities where large amounts of low pressure process steam are available.
Reheat turbines are also used almost exclusively in electrical power plants. In a reheat turbine, steam flow exits from a high pressure section of the turbine and is returned to the boiler where additional superheat is added. The steam then goes back into an intermediate pressure section of the turbine and continues its expansion.
Extracting type turbines are common in all applications. In an extracting type turbine, steam is released from various stages of the turbine, and used for industrial process needs or sent to boiler feed water heaters to improve overall cycle efficiency. Extraction flows may be controlled with a valve, or left uncontrolled. Induction turbines introduce low pressure steam at an intermediate stage to produce additional power.
2(9). APPLICATIONS:
To drive large centrifugal pumps, such as feed water pumps at a thermal power plant. A small industrial steam turbine directly linked to a generator. This turbine generator set of 1910 produced 250 kW of electrical power. Electrical power stations use large steam turbines driving electric generators to produce most (about 80%) of the world's electricity.
The advent of large steam turbines made central-station electricity generation practical, since reciprocating steam engines of large rating became very bulky, and operated at slow speeds. Most central stations are fossil fuel power plants and nuclear power plants; some installations use geothermal steam, or use concentrated solar power (CSP) to create the steam. Steam turbines can also be used directly.
The turbines used for electric power generation are most often
directly coupled to their generators. As the generators must rotate at constant synchronous speeds according to the frequency of the electric power system, the most common speeds are 3000 RPM for 50 Hz systems and 3600 RPM for 60 Hz systems.
Since nuclear reactors have lower temperature limits than fossil-fired plants, with lower steam quality, the turbine generator sets may be arranged to operate at half these speeds, but with four-pole generators, to reduce erosion of turbine blades.
Marine propulsion
In ships, compelling advantages of steam turbines over reciprocating engines are smaller size, lower maintenance, lighter weight, and lower vibration. A steam turbine is only efficient when operating in the thousands of RPM, while the most effective propeller designs are for speeds less than 100 RPM; consequently, precise (thus expensive) reduction gears are usually required, although several ships, such as Turbine , had direct drive from the steam turbine to the propeller shafts.
Another alternative is turbo-electric drive, where an electrical generator run by the high-speed turbine is used to run one or more slow-speed electric motors connected to the propeller shafts; precision gear cutting may be a production bottleneck during wartime.
Nuclear-powered ships and submarines use a nuclear reactor to create steam. Nuclear power is often chosen where diesel power would be impractical (as in submarine applications) or the logistics of refuelling pose significant problems (for example, icebreakers).
Locomotives
Steam turbine locomotive. A steam turbine locomotive engine is a
steam locomotive driven by a steam turbine. The main advantages of a steam turbine locomotive are better rotational balance and reduced hammer blow on the track. However, a disadvantage is less flexible power output power so that turbine locomotives were best suited for long- haul operations at a constant output power.
3. LITERATURE REVIEW:
The initially developed reciprocating steam engine has been used to produce mechanical power since the 18th Century, with notable improvements being made by James Watt .When the first commercially developed central electrical power stations were established in 1882 at Pearl Street Station in New York and Holborn Viaduct power station in London, reciprocating steam engines were used. The development of the steam turbine in 1884 provided larger and more efficient machine designs for central generating stations. By 1892 the turbine was considered a better alternative to reciprocating engines; turbines offered higher speeds, more compact machinery, and stable speed regulation allowing for parallel synchronous operation of generators on a common bus. After about 1905, turbines entirely replaced reciprocating engines in large central power stations.
The largest reciprocating engine-generator sets ever built were completed in 1901 for the Manhattan Elevated Railway. Each of seventeen units weighed about 500 tons and was rated 6000 kilowatts; a contemporary turbine set of similar rating would have weighed about 20% as much.