Diesel Oil

admin — Thu, 14 Feb 2008 17:18:05 +0000

Diesel is one of the fractional distillate obtained during distillation of crude oil or petroleum. It is generally called petrodiesel, as it is obtained from petroleum, to differentiate it from other forms of diesel which are obtained from sources like biomass. It is obtained between temperature range of 200 °C and 350 °C during fractional distillation at atmospheric pressure. It has a density of around 850 grams per liter which is 15% less than that of petrol or gasoline with a calorific value of around 41 mega joules per liter which is also around 15% less when compared to the calorific value of petrol. Diesel is primarily used as a fuel in specially designed diesel engines which were invented by Rudolf Christian Karl Diesel, a German engineer and patented in 1892. Initially Coal Dust was used as fuel in Diesel engine and after that vegetable oils were experimented as fuel.
First diesel engine was commercially built by Adolphus Busch in the United States. After the end of World War I diesel engines which were used in submarines were made to adapt for peacetime economy by soldiers who operated these engines. ”Semi-Diesel’ engines were manufactured by modifying these diesel engines which were used in trucks in 1930s. Fuel injection systems were started to develop in 1922 by Robert Bosch and by 1927 an acceptable and efficient injection pump was produced. The demand for this pump was very large and manufacturing was outsourced to France and England to meet the demand.Diesel regulations were introduced in the late 1960s which further strengthen the development of better diesel engines with less emission and improved fuel economy.
The composition of diesel basically has major portion of saturated hydrocarbons such as paraffins and cycloparaffins and some portions of aromatic hydrocarbons such as alkylbenezenes and naphthalenes. It is also believed that diesel oil also contains some microbes which are capable of survival in closed tank and can feed on diesel fuel.
Diesel contains a high level of pollutants as compared to petrol which require it to undergo additional filtration. Since it can also be used as heating oil its demand in cold countries is quite high as compared to petrol and as result diesel is priced higher than gasoline in UK and many parts of US. Higher energy content of diesel and the internal efficiency of diesel engine make diesel a better fuel for cars which provides better economy and causes about 31% less polluted emissions as compared to gasoline.
Due to strict emission standards being imposed world over, the world is looking for cleaner fuels. Synthetic diesel has also proved to be cleaner fuel as compared to petrodiesel as it emits 30% less pollutants. Synthetic diesel is produced by drying and gasifying garbage, sewage sludge, straw, wood and corn which results in synthetic gas. This gas after purification goes through Fischer-Tropsch process which results in synthetic diesel by converting carbon monoxide and hydrogen into liquid hydrocarbons. Natural gas can also be used to produce synthetic diesel. Bio-diesel has also come up as an alternative fuel to conventional diesel which is produced from vegetable oils.
Over the last two decades the diesel technology has shown substantial improvements. Dynamics of innovations in diesel technology has been quite high in recent years. Evolution of direct injection technology has bought breakthrough in diesel technology which has resulted in improved efficiency of energy usage by 15-20% by improving injectors and increasing pressure of injection. Many additives are being used with diesel to improve its energy content and provide better fuel efficiencies. Presently Research and Developments in the fields of diesel technology are focusing on reductions of emissions which can be achieved only on the cost of reduced energy efficiency. Most of the current Research and Development work in field of diesel technology is focused mainly at marine transport and automotive transport and railways is also expected to follow.

CLUTCHES

admin — Wed, 11 Jul 2007 11:56:36 +0000

The clutch is a tool for transmitting rotation. It can be either engaged or disengaged. It has two rotating shafts. One is pulley operated and the other uses another technique. The clutch connects two shafts in a pulley so that locked together it can spin at the same speed or when the coupling is disengaged they can spin at different speeds.

The underlying principle of various types of clutches is based on friction discs (one or more) pressed close together or against a flywheel with the use of springs. In heavy duty vehicles ceramic clutches are in use because it is more resistant to friction.

One wet variety of clutch is kept soaked in a cooling lubricant that keeps the surface clean and longevity. A dry clutch is the reverse and some energy is thus lost.

In a motorcar the clutch is operated by pressing on the pedal at the extreme left using hydraulics or cable connections from the pedal to the clutch. Although the clutch itself is quite close to the pedal this remote system is necessary to neutralize slight engine vibrations – engine mountings being always flexible by intention. If it had been rigid it would have been impossible to have smooth engagement. If there is no pressure on the pedal it means that the clutch plates are driving or engaged. Depressing the pedal means disengaging the clutch plates. The driver can now shift gears.

In a manual transmission there are cogs for gear selection. These have matching teeth so that the rotational speeds of the two are in harmony for the engagement. This matching is achieved by another clutch known as a synchronizer. This technique uses contact by friction to bring the two sections to similar speed. There is a locking device to disallow engagement of the teeth until all the speeds are matched with each other.

The radiator fan often has a clutch that is activated by heat. The driving and driven devices are separated by fluid. At low temperatures the consistency is thin allowing the clutch to slip. At higher temperatures the density of the fluid thickens allowing the fan to rotate freely. Also are available electronic clutches to lock the pulley with the compressor.

Clutches in most of the motorcycles are operated with the help of a clutch lever that is placed on the left side of the handlebar. If there is no pressure on the bar it means that the plates are engaged. By pulling the lever backwards towards the driver the clutch plates get disengaged allowing for shifting of gears. Some of the latest models of cars and mopeds have a centrifugal clutch devises. Racing models of motorcycles use slipper-clutches to negate engine-braking effects.

There are also dog clutches and cone clutches. Safety clutches are usually fixed on to garden mowers. If a rock or stump is hit then the clutch will slip. Other types of clutches are overrunning clutches, single plate and multi plate friction clutches, centrifugal clutches, semi centrifugal clutches, hydraulic clutches and electromagnetic clutches.

A manual transmission car has more than one clutch. Even automatic transmission cars have clutches. It is not just cars – many everyday tools have clutches. Cordless drills, chainsaws and yo yo’s too have clutches. Clutches are indispensable in tools that have two rotating shafts. It is the clutch that does the connecting work so that either these are locked together and spin at the same speed or they are disengaged and go round at different speeds. In a car the engine spins all the time but the wheels do not. So in order to stop the car without harming the engine the wheels have to be disengaged from the engine. The clutch does the trick.

The technique of clutch is connected to the principles of friction. Friction is used to measure how hard it is to slide a thing over another object. Every article has peaks and depressions. These cause the friction. Even the most apparently smooth surfaces have microscopic hills and valleys. The larger the difference the greater is the friction. The workings of a clutch are based on the friction between the clutch plate and the flywheel. When there is no pressure on the pedal the springs push the plate against the disc of the clutch. This in turn presses against the flywheel locking the engine to the transmission input shaft that causes these to spin at the same speed. The amount of force, which the clutch can stand, depends on the friction between the flywheel and the clutch plate and also the force the spring places on the pressure plate.

The friction material on the disc wears out causing problems for the clutch. The clutch then starts to slip. Power will not be transferred from the engine to the wheels. The wear and tear takes place when the clutch disc and the flywheel spin at different speed. When they are locked there is synchronization and no friction. Thus the life of the clutch depends a lot on the expertise of the driver. Another headache is worn out bearings. The symptom of this disease is a rumbling noise whenever the clutch is engaged.

In the case of automatic transmission several clutches are in the fray. These connect or disconnect many sets of planetary gears. The compressor of air conditioning in the car has a magnetic clutch. This enables the compressor to switch off even while the engine is running. With the current flowing through a magnetic coil fixed in the coil, the clutch engages. But when the current stops as when the air conditioning is switched off, the clutch gets disengaged.
To clutch on means to hold on to. Man gets his engineering ideas from Nature, the ultimate teacher. The clutch in our lives is our conscience linking us to Nature, telling us to cling on and tune in to the dancing steps of life around us – our environment, if we do not want our car to grind to a pathetic halt.

Diesel Oil

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Diesel Oil

CLUTCHES