In a two wheeler, how is a four stroke engine more eco-friendly than a two stroke engine?
The two stroke engine has no valves but uses ‘ports’, holes on the cylinder, which are opened or closed as the piston moves. On a power stroke, the piston compresses the petrol and air mixture which has entered the crank case. This is forced into the upper cylinder as the transfer port opens and helps to push out the exhaust gas through the open exhaust port. In a two stroke engine, compression and suction takes place in one stroke of the piston and expansion and exhaust strokes also takes place in one stroke. Thus in a two stroke of the piston all the four processes are completed which does not burn the gases completely and hence makes the scavenging less effective.
In a two stroke engine, oil is mixed with the fuel to provide lubrication for moving surfaces such as piston skirt and roller bearings. It is subsequently carried into the combustion chamber by the air stream, where it is partially burnt and pushed through the exhaust port along with the exhaust gases. This results in pollution.
In a four stroke engine, the suction, compression, expansion and exhaust strokes take place in four stroke of the piston or two revolution of the crank shaft. Thus the scavenging is more effective in four stroke engine and hence four stroke engine is more eco-friendly.
Why two wheelers are not normally fitted with Diesel engines?
The two wheelers are not normally fitted with Diesel engines because the power output from the Diesel engine is high and more over nose and vibrations are at high level. The problem also lies in power to weight ratio of the two wheelers. Two wheelers that use Diesel as fuel are heavy in size. Diesel can not be used with 50, 100 and 150 cc engines because of high power output.
What is the difference between internal and external combustion engines?
External combustion engines burn fuel outside the engine and produce a hot working fluid that powers the engine. The classic example of an external combustion engine is a steam engine.
Internal combustion engines burn fuel inside the engine and use the fuel and the gases resulting from its combustion as the working fluid that powers the engine. An automobile engine is a fine example of an internal combustion engine.
How does a steam engine work?
A steam engine is a type of heat engine that converts the heat flowing from a hotter object to a colder object into useful work. The fraction of heat that can be converted to work is governed by the laws of thermodynamics and increases with the temperature difference between the hotter and colder objects. In the case of the steam engine, the hotter the steam and the colder the outside air, the more efficient the engine is at converting heat into work.
1. A typical steam engine has a piston that moves back and forth inside a cylinder. Hot, high-pressure steam is produced in a boiler and this steam enters the cylinder through a valve. Once inside the cylinder, the steam pushes outward on every surface, including the piston.
2. The steam pushes the piston out of the cylinder, doing mechanical work on the piston and allowing the piston to do mechanical work on machinery attached to it. The expanding steam transfers some of its thermal energy to this machinery, so the steam becomes cooler as the machinery operates.
3. But before the piston actually leaves cylinder, the valve stops the flow of steam and opens the cylinder to the outside air.
4. The piston can then re-enter the cylinder easily. In many cases, steam is allowed to enter the other end of the cylinder so that the steam pushes the piston back to its original position. Once the piston is back at its starting point, the valve again admits high-pressure steam to the cylinder and the whole cycle repeats.
Overall, heat is flowing from the hot boiler to the cool outside air and some of that heat is being converted into mechanical work by the moving piston.
Why achieving absolute zero is impossible? What will happen to objects at this temperature (i.e., solid, liquid, and gas)?
Absolute zero can not be reached for the reason that any perfect order is impossible. For an object to reach absolute zero, every single bit of thermal energy and every aspect of disorder must leave the object. If the object is a crystalline material, then its crystal structure must become absolutely perfect. This sort of perfection is essentially impossible. Reducing the temperature of an object towards absolute zero requires great effort and ends up creating a great disorder elsewhere. The closer the approach to absolute zero, the more disorder is created elsewhere. Hence achieving absolute zero is impossible.
The two stroke engine has no valves but uses ‘ports’, holes on the cylinder, which are opened or closed as the piston moves. On a power stroke, the piston compresses the petrol and air mixture which has entered the crank case. This is forced into the upper cylinder as the transfer port opens and helps to push out the exhaust gas through the open exhaust port. In a two stroke engine, compression and suction takes place in one stroke of the piston and expansion and exhaust strokes also takes place in one stroke. Thus in a two stroke of the piston all the four processes are completed which does not burn the gases completely and hence makes the scavenging less effective.
In a two stroke engine, oil is mixed with the fuel to provide lubrication for moving surfaces such as piston skirt and roller bearings. It is subsequently carried into the combustion chamber by the air stream, where it is partially burnt and pushed through the exhaust port along with the exhaust gases. This results in pollution.
In a four stroke engine, the suction, compression, expansion and exhaust strokes take place in four stroke of the piston or two revolution of the crank shaft. Thus the scavenging is more effective in four stroke engine and hence four stroke engine is more eco-friendly.
Why two wheelers are not normally fitted with Diesel engines?
The two wheelers are not normally fitted with Diesel engines because the power output from the Diesel engine is high and more over nose and vibrations are at high level. The problem also lies in power to weight ratio of the two wheelers. Two wheelers that use Diesel as fuel are heavy in size. Diesel can not be used with 50, 100 and 150 cc engines because of high power output.
What is the difference between internal and external combustion engines?
External combustion engines burn fuel outside the engine and produce a hot working fluid that powers the engine. The classic example of an external combustion engine is a steam engine.
Internal combustion engines burn fuel inside the engine and use the fuel and the gases resulting from its combustion as the working fluid that powers the engine. An automobile engine is a fine example of an internal combustion engine.
How does a steam engine work?
A steam engine is a type of heat engine that converts the heat flowing from a hotter object to a colder object into useful work. The fraction of heat that can be converted to work is governed by the laws of thermodynamics and increases with the temperature difference between the hotter and colder objects. In the case of the steam engine, the hotter the steam and the colder the outside air, the more efficient the engine is at converting heat into work.
1. A typical steam engine has a piston that moves back and forth inside a cylinder. Hot, high-pressure steam is produced in a boiler and this steam enters the cylinder through a valve. Once inside the cylinder, the steam pushes outward on every surface, including the piston.
2. The steam pushes the piston out of the cylinder, doing mechanical work on the piston and allowing the piston to do mechanical work on machinery attached to it. The expanding steam transfers some of its thermal energy to this machinery, so the steam becomes cooler as the machinery operates.
3. But before the piston actually leaves cylinder, the valve stops the flow of steam and opens the cylinder to the outside air.
4. The piston can then re-enter the cylinder easily. In many cases, steam is allowed to enter the other end of the cylinder so that the steam pushes the piston back to its original position. Once the piston is back at its starting point, the valve again admits high-pressure steam to the cylinder and the whole cycle repeats.
Overall, heat is flowing from the hot boiler to the cool outside air and some of that heat is being converted into mechanical work by the moving piston.
Why achieving absolute zero is impossible? What will happen to objects at this temperature (i.e., solid, liquid, and gas)?
Absolute zero can not be reached for the reason that any perfect order is impossible. For an object to reach absolute zero, every single bit of thermal energy and every aspect of disorder must leave the object. If the object is a crystalline material, then its crystal structure must become absolutely perfect. This sort of perfection is essentially impossible. Reducing the temperature of an object towards absolute zero requires great effort and ends up creating a great disorder elsewhere. The closer the approach to absolute zero, the more disorder is created elsewhere. Hence achieving absolute zero is impossible.
1 comment:
this was 5 in one pack . Nice information about the working of steam engine
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