Assignment

Assignment-(Pascals principle, Boyles Law, Charles Law)One page 300-500 words per subject, this must be in TUESDAY 3rd MAY

PASCAL'S PRINCIPLE

Blaise Pascal (1623 1662), France - the famous mathematician and physicist, philosopher and essayist. Main contribution is in physics, discovered PASCAL's law, and his name to be used as pressure units.

Pascal's law (the Principle of transmission of fluid-pressure)

Since the liquidity of liquids, when the pressure of a certain part of static fluid changes in a closed container,will pass this pressure to all directions constantly. 

According to the Pascal's law, when a pressure went on one of the piston in hydraulic system will produce the same pressure on another piston in the system. If the second piston area is the first ten times of piston area, then the forces on the second pistons will increase to first pistons ten times, but the two pressure of the piston still equal.

P1 = P2, F1 ÷ S1 = F2 ÷ S2

P - Pressure  F - Force  S - Area

This law in production technology is very important in the application of the principle. It has many uses, such as hydraulic brake etc.

BOYLE'S LAW

Robert Boyle (1627 ~ 1691) physicist and chemist, was born in January 25 1627.

Boyle's law

Certain quality of gas at constant temperature, the pressure in inverse proportion to the volume.

Certain quality of gas, with constant temperature, The average kinetic energy of gas molecules will not change. If gas reduce volume, the number of gas molecules in unit volume will increase, the number of gas molecules hit the container in unit time will increase, so the pressure will increase; if volume increase, the pressure will decrease. 

When temperature constant: 

P1 x V1 = P2 x V2

P - pressure   V - Volume

LARGER PRESSURE - LESS VOLUME

LESS PRESSURE - LARGER VOLUME

CHARLE'S LAW

Jacques Alexandre Cesar Charles (1746～1823）French physicists and mathematicians and inventor.

Charle's law 

Describe the pressure of quality gas at constant temperature for linear with its volume change rules: V=V0(1+βt)，V0 is the volume at 0℃, t in Celsius temperature, β is gas coefficient of expansion. For the ideal gas, β=1/273.15, V=V0(1+t/273.15), The quality that shall set the volume of ideal gas pressure with thermodynamics is proportional to the temperature.

Certain quality of gas, when its volume is certain, it is proportional to the pressure and temperature.

When volume constant: 

P1 ÷ P2 ＝ T1 ÷ T2 　　

P - pressure   T - temperature

HIGHER TEMPREATURE - HIGER PRESSURE

LOWER TEMPREATURE - LESS PRESSURE

Reference:

http://www.mintye.com/h_brake_system.asp 

http://baike.baidu.com/view/84928.html#sub84928 

http://en.wikipedia.org/wiki/Pascal's_law 

http://www.google.com/imgres 

http://en.wikipedia.org/wiki/Boyle's_law 

http://www.baidu.com/s?wd=%B2%E9%C0%ED+%B6%A8%C2%C9 

http://baike.baidu.com/view/414465.htm#sub414465 

1.What is the firing order of a four stroke engine?
3 cylinders: 1-2-3
4 cylinders: 1-3-4-2 / 1-2-4-3 / 1-3-2-4

5 cylinders: 1-2-4-5-3

6 cylinders: 1-5-3-6-2-4 / 1-6-5-4-3-2 / 1-2-3-4-5-6 / 1-4-2-5-3-6

7 cylinders: 1-3-5-7-2-4-6
8 cylinders: 1-8-4-3-6-5-7-2 / 1-8-7-2-6-5-4-3 / 1-3-7-2-6-5-4-8 / 1-5-4-8-7-2-6-3 / 1-6-2-5-8-3-7-4

10 cylinders: 1-10-9-4-3-6-5-8-7-2 / 1-6-5-10-2-7-3-8-4-9

12 cylinders: 1-7-5-11-3-9-6-12-2-8-4-10

16 cylinders: 1-12-8-11-7-14-5-16-4-15-3-10-6-9-2-13

2.What is the difference between a S.I and C.I engine?
1. Type of cycle: 
 S.I - Otto cycle
 C.I - Diesel cycle
2. Type of fuel:   
 S.I - Petrol
 C.I - Diesel
3. Type of ignition:
 S.I - Ignite by spark plug
 C.I - Self-ignite by high pressure
4. Compression ratio:
 S.I - 6~10
 C.I - 16~20
5. Weight:
 C.I engines are heavier than S.I engines because higher pressure inside the engine.
6. Speed:
 S.I engines run at higher speeds than C.I engines
7. Thermal efficiency:
 C.I engines have higher thermal efficiency than S.I engines due to the higher pressure.


3.Is there any difference between a S.I and C.I piston if so what?
In most C.I engines, the combustion chamber is in the top of the piston,  rather than the S.I engines in the cylinder head. C.I pistons also longer and heavier than S.I pistons.

   C.I piston                        S.I piston


4.What year was the diesel engine invented and by whom?

Diesel engine was invented at 1892 by German inventor Rudolf Diesel.


5.What is the purpose of the oil jet on the connecting rod, and where does it spray?
The oil jet lines up with the oil hole in the crankpin once on each revolution of the crankshaft. When this occurs, a squirt of oil is directed onto the cylinder walls, also lubricates the piston pin.

6.On the connecting rod where is the big end and little end?
 Big end - The crankpin end. Little end - The piston end.

7.What is the purpose of the thrush washers on the crankshaft?
Thrust washers are long-wearing flat bearings to keep crankshaft rotates in position.

8.On a diesel engine whats the difference between direct injection and a indirect injection type?
Direct injection: Fuel is injected directly into the combustion chamber in the piston head.
Indirect injection: Fuel not inject into the main combustion space, instead, the fuel is injected into a small separate chamber.

9.Explan the term valve timing?
Lead - intake valve opens before TDC and exhaust valve opens before BDC.
Lag - intake valve closes after BDC and exhaust valve closes after TDC.

Overlap - intake and exhaust valves are both open for a few degrees around TDC of the exhaust stoke.

10.Why do we have valve clearance?
Because the valve train gets hot when engine is running, needs some clearance to expand, otherwise the valve will not shut properly. May cause a gas leak, or a valve burn.

What is taper and ovality in the bore, how is it caused how do you check it?

Taper - difference between the measurements of A1 B1 C1 and difference between the measurements of A2 B2 C2. 
That caused by the piston rings rubbing on the cylinder walls. 
To measure it, place the cylinder-bore gauge across the cylinder, just below the unworn ring ridge, move the gauge slowly up and down to measure taper at top middle and bottom of the ring travel in cylinder.

Ovality(out-of-roundness) - difference between A1 and A2.
May caused by unequal pressure on the piston.
To measure it, place the cylinder-bore gauge across the cylinder, just below the unworn ring ridge, move the gauge slowly up and down to measure A1, turn the gauge 90° in the cylinder to measure A2. 

What is side clearance on a piston and how is it checked? 
Side clearance  about 0.02mm to 0.05mm.
Using a micrometer, measure the diameter of piston at a point about one-third of the skirt height, and compare to the diameter reading measured from cylinder bore.


How can you tell the difference between a inlet and exhaust valve and why?
Inlet valve always lager or more than the exhaust valve.
Because  lager or more inlet valves reduce intake resistance, allow lager intake passages and freer flow into cylinder.

What sort of tempatures do the inlet and exhaust valves get upto?
Inlet - 150~250°F / 66~121°C
Exhaust - 1000~1500°F / 538~816°C


What temperatures and speeds must the piston be able to cope with?
Temperatures - Around 230°C at the top, and around 100°C at the skirt.
Speeds - Around 16m/s for automobile engines, and around 20–25 m/s for sport automobile engines or motorcycles


Why do we have piston ring end gap clearance ?
Because when engine is running, the piston ring get hot, needs room to expand.

What could the result be if the piston ring end gap is too small?
If the gap is too small, the ring will have no room to expand when it gets hot.



Why do aluminum cylinder heads usually have a steel shim (washer) between the valve spring and the 
cylinder head surface ?
Because the valve spring needs to move up and down lots of times, could damage the aluminum cylinder head, steel has better intensity than aluminum, also shim can adjust the valve length to control the valve seat pressure.


What is meant by the terms S.I and C.I in a four stroke engine?
S.I - Spark ignition 
C.I - Compression ignition 


What is the purpose of the margin on the valve?
If there is not margin or thickness at the edge of valve, will cause the valve head to overheat then the edge will burn.

What is the purpose of a core plug?
It is used to remove sand from the casting when the engine block is cast.

What is end float and run out on a crankshaft, hows is measured?
End float - alignment at the end of crankshaft.
Run out - alignment at the journal of the center bearing.
How to measure refer to the pictures:

                             End Float

                             Run out

Four stroke engine

How does a four stroke engine work? Name the cycles ,I want to know what the piston is doing and the valves on each stroke. 


1. Intake - The piston is moving down, intake valve open to drawn the air-fuel mixture into the cylinder.
2. Compression - The piston is moving up to compress the air-fuel mixture in the cylinder, both valves closed, 
3. Power - The piston is moving down by the force of combusted air-fuel mixture, both valves closed.
4. Exhaust - The piston is moving up to force the burnt gases out through the open exhaust valve.

Who and what year was the  four stroke engine invented.

Nikolaus August Otto (1832～1891)

German engineer, invented the first four-stroke engine in 1876.


What is the purpose of the crankshaft,camshaft,vavles collects(keepers),valve sterm seals,head gasket,pistons,piston rings name them all, cambelt,flywheel?


1. Crankshaft - With a crank for each cylinder, connects the piston through connecting rod, turns the piston up and down(straight-line) motion into rotary motion.

2. Camshaft - Controls the timing of intake and exhaust valves open and close. 

3. Valves keepers - The keeper has two opposite fixed ends pressed against a valve seat by the cylinder head, each one of them has an elastically deformable portion to be elastically deformed by a pressing force of the cylinder head.

4. Valve stem seals - avoid any oil enter into intake, exhaust pipes or the cylinder, also stops leakage of air-fuel mixture from the intake pipe or  the burnt gases from exhaust pipe.

5. Head gasket - Seals coolant and oil, also seals the gas pressure in the cylinders.

6. Pistons - withstands the pressure from combustion, transfer the power onto crankshaft through connecting rod, piston top also a part of the combustion chamber.

7. Piston rings - 
                        Compression rings: Seals the air inside the combustion chamber.

                          Oil rings: Scrapes off excess oil from the cylinder walls.

8. Cam-belt - Connects camshaft and crankshaft to ensure the accuracy of the intake and exhaust timing.

9. Flywheel - Store rotational inertia when engine speed up,and release the rotational inertia when engine, can be used to reduce the speed fluctuation during mechanical operation.

What is the bore and stroke.


Bore - The diameter of the piston and the inside diameter of the cylinder.


Stroke - The distance traveled by the piston from T.D.C(Top Dead Center) to B.D.C(Bottom Dead Center)