Petrol Engines And Diesel Engines.

Comparison of Petrol and Diesel Engines
Petrol vs Diesel engines: A comparison - Basic difference between a petrol engine and a diesel engine based on working, pressures, combustion, compression ratios, speed, efficiency, maintenance, and running costs. The following points are important for the comparison of petrol and diesel engines:

Petrol Engines:

Diesel Engines:

1.
Petrol Engines

A petrol engine draws a mixture of petrol and air during suction stroke.

Diesel Engines

A diesel engine draws only air during suction stroke.

2.
Petrol Engines

The carburetor is employed to mix air and petrol in the required proportion and to supply it to the engine during suction stroke.

Diesel Engines

The injector or atomiser is employed to inject the fuel at the end of compression stroke.

3.
Petrol Engines

The pressure at the end of compression is about 10 bar.

Diesel Engines

The pressure at the end of compression is about 35 bar.

4.
Petrol Engines

The charge (i.e. petrol and air mixture) is ignited with the help of a spark plug

Diesel Engines

The fuel is injected in the form of fine spray. The temperature of the compressed air (about 600° C at a pressure of about 35 bar) is sufficiently high to ignite the fuel.

5.
Petrol Engines

The combustion of fuel takes place approximately at constant volume. In other words, it works on Otto cycle.

Diesel Engines

The combustion of fuel takes place approximately at constant pressure. In other words, it works on Diesel cycle.

6.
Petrol Engines

A petrol engine has compression ratio approximately from 6 to 10.

Diesel Engines

A diesel engine has compression ratio approximately from 15 to 25.

7.
Petrol Engines

The starting is easy due to low compression ration.

Diesel Engines

The starting is little difficult due to high compression ratio.

8.
Petrol Engines

As the compression ratio is low, the petrol engines are lighter and cheaper.

Diesel Engines

As the compression ratio is high, the diesel engines are heavier and costlier.

9.
Petrol Engines

The running cost of petrol engines is high because of higher cost of petrol.

Diesel Engines

The running cost of diesel engines is low because of the lower cost of diesel.

10.
Petrol Engines

The maintenance cost is less.

Diesel Engines

The maintenance cost is more.

11.
Petrol Engines

The thermal efficiency is upto about 26%.

Diesel Engines

The thermal efficiency is upto about 40%.

12.
Petrol Engines

Overheating trouble is more due to low thermal efficiency.

Diesel Engines

Overheating trouble is less due to high thermal efficiency.

13.
Petrol Engines

These are high speed engines.

Diesel Engines

These are relatively low speed engines.

14.
Petrol Engines

The petrol engines are generally employed in light duty vehicles such as scooters, motorcycles, cars. These are also used in aeroplanes.

Diesel Engines

The diesel engines are generally employed in heavy duty vehicles such as buses, trucks and earth moving machines etc.

Vernier Caliper ( Science and Technology)

Vernier Caliper

A Vernier caliper is measuring scale it is used in Horizontal and Depth place measure.  If a two scale one main scale and second Vernier scale. 

Vernier caliper

One small division on main scale = 1 mm

No. of divisions on Vernier scale = 50

50 Vernier scale divisions = 49 divisions on main 

scale (or 49 mm)

Each division on Vernier scale = (49/50) mm

Difference between one main scale division and one 

Vernier scale division = 1 - (49/50) mm

= (50 - 49)/50

= (1/50) mm

= 0.02 mm

Least Count = 0.02 mm

Least count = 0.02

Advantages and Disadvantages Of CNC Machine.(Science and Technology)

 Advantages of CNC Machine:

 1. Greater accuracy of job is achieved.
2 . Higher repeatability and improved product quality.
3. Less operator skill is required to run CNC machine.
4. Better machine utilization hence reduced idle time.
 5. High production rate as speed, feed, depth of cut are optimum for highest quality
6. Lower tooling cost, per piece in production.
7. Jig 's and fixture's cost are often reduced. 8. Reduced cycle time.
 9. Better tool life and machineability.
 10. Less scrap thanks to consistent accuracy, less errors.
 11. Excellent reliability as dimensions are supported programes.
 12. Reduced in - process inventory of parts in process.
13. Design changes are possible. Any change in design is possible at lowest cost.
14. Use of programmable software like Ideas. Master - Cam, Pro - engineer, Edge Cam  etc. for sophisticated jobs.
 15. Productivity are often improved to great extent.
16. CNC machines could also be utilized altogether three shifts to scale back the value of machinery.
17. Tool setup time are often reduced.
 18. Two or more machines are often controlled with one monitor.
19. best suited for continuous and better production.
20. Program are often stored and used again when required.
21. Optimum speed and feed for best surface finish are often used.

Disadvantages of CNC Machine:

 1. CNC machines are more complex machines.
 2 . Cost is high.
3. Cost of control systems used is high.
4. Maintenance cost is high.

CNC MACHINE(Science and Technology)

                CNC MACHINE

 Automation and production are related to advancement in technology. production machine tools include automatic unit machine tools and automatic transfer-machines etc. These machine tools are highly specialized but inflexible. aside from these machine tools, quite about half the entire available machine tools are engaged in small lot and piece production. These include general purpose machine tools, hydraulic tracer controlled machine tools and programmed operation cycle machine tools." the overall purpose machine tools, albeit highly flexible (can easily change from one product to another), aren't suitable for production, due to longer found out times, machine and gear adjustments. due to the above factors an excellent need was for machine tools that would bridge the gap between highly flexible general purpose machine tools (which aren't economical for mass production) and highly specialized, but inflexible production machines.

DIAGRAM OF CNC (SCIENCE AND TECHNOLOGY)

DIAGRAM OF CNC MACHINE.

               1. CONTROL  CNC MACHINE

2. CNC MACHINE

                           

              3. BLOCK DIAGRAM OF CNC

Machine (Science and Technology).

                       Machine

A device which gains some energy and converts into desired useful work that's called machine.


                             Types

1.  A machine which generating mechanical energy.

 These sorts of machines some energy like heat, hydraulic, electrical, etc convert into mechanical work. it's also called prime movers.

 Example:- combustion engine, turbine, water turbine, steam engines, etc. Like combustion Engine during which energy is converted into the warmth energy which turn is converted into the mechanical add the rotation of the wheel to the vehicle.

2. Machines which transforming mechanical energy.

 These sorts of machines convert energy into other energy forms is understood as Transforming energy machines like Hydraulic energy, electricity, etc. it's also called converting machines.

 Example:- Electrical generator, hydraulic ram etc. Like Electric generator during which rotation of the shaft (Mechanical energy) is converted into electricity.

3. Machines which utilizing mechanical energy.

 This type of machine is receiving energy utilizing various applications.

 Example:- CNC machine, Milling machines, etc. Like Lathe machine that utilizes energy.

Surface Tension(Science and Technology)

                         SURFACE TENSION

It is defined as a tensile force working on the surface of a liquid in contact with air(gas) or between two immiscible liquid.

Surface Tension denote by ' Little sigma'.
Unit of surface tension 'N/m'.
 Newton/meter.

Pressure force relation for water droplet is Surface tension is

P=4 x sigma/ d.

P= Pressure force (Intensity of pressure).
Sigma= Surface tension.
d= diameter of water droplet.

Pressure force relation of Soap bubble is Surface tension is 

P=8 x sigma/ d.

P= pressure force
Sigma= Surface tension. 
d= diameter of Soap bubble.