IC Engine

 IC Engine 

"Internal combustion engines" (briefly written as I. C. engines) are those engines in which the combustion of fuel takes place inside the engine cylinder. 

The I.C. engines use either petrol or diesel as their fuel. In petrol engines (also called spark ignition engines or S.I engines), the correct proportion of air and petrol is mixed in the carburetor and fed to engine cylinder where it is ignited by means of a spark produced at the spark plug. In diesel engines (also called compression ignition engines or C.I engines), only air is supplied to the engine cylinder during suction stroke and it is compressed to a very high pressure, thereby raising its temperature from 600°C to 1000°C. The desired quantity of fuel (diesel) is now injected into the engine cylinder in the form of a very fine spray and gets ignited when comes in contact with the hot air.

CLASSIFICATION OF INTERNAL COMBUSTION ENGINES 

1. According to Application 

Automotive: 

(i) Car 

(ii) Truck/Bus          

(iii) Off-highway 

2. Locomotive 

3. Light Aircraft 

4. Marine:  (i)Outboard

(ii) Inboard

(iii) Ship 

5.  Power Generation:

(i) Portable (Domestic)

(ii) Fixed (Peak Power) 

6. Agricultural:

(i) Tractors

(ii) Pump sets 

7. Earthmoving: 

(i) Dumpers

(ii) Tippers

(iii) Mining Equipment 

8. Home Use:  

(i) Lawnmowers

(ii) Snow blowers

2. According to Basic Engine Design: 

1. Reciprocating  

(a)   Single Cylinder

(b)  Multi-cylinder 

(I) In-line                                  

(ii) V                                                                

(iii) Radial                                                               

(iv) Opposed Cylinder                                                 
(v) Opposed Piston 

2. Rotary:              

(a) Single Rotor             

(b) Multi-rotor 

3. According to Operating Cycle 

1. Otto  (For the Conventional SI Engine) 

2. Atkinson (For Complete Expansion SI Engine)

3. Miller (For Early or Late Inlet Valve Closing type SI Engine)

4. Diesel (For the Ideal Diesel Engine)

5. Dual (For the Actual Diesel Engine) 

4. According to Working Cycle (Strokes) 

1. Four Stroke Cycle:

(a) Naturally Aspirated

(b)Supercharged/Turbocharged 

2. Two Stroke Cycle: 

(a)  Crankcase Scavenged 

(b) Uniflow Scavenged

(i)   Inlet valve/Exhaust Port

(ii)  Inlet Port/Exhaust Valve

(iii) Inlet and Exhaust Valve 

5. According to valve/Port Design & Location

(a) Valve/Port  Design 

1. Poppet Valve 

2. Rotary Valve 

3. Reed  Valve 

4. Piston Controlled Porting  

5. (b) Valve Location 

1. The T-head 

2. The L-head 

3. The F-head 

4. The I-head: 

(i) Over head Valve (OHV)            

(ii) Over head Cam (OHC) 

6. According to Fuel 

1.Conventional: 

(a) Crude oil derived 

(i)  Petrol                     

(ii) Diesel               

(b) Other sources: 

(i) Coal          

(ii) Wood (includes biomass)          

(iii)Tar Sands          

(iv)Shale 

2. Alternate: 

(a) Petroleum derived   

(i)  CNG (Total Replacement)                           

(ii) LPG                

(b) Biomass Derived  

(i) Ethanol                      

(ii) Vegetable oils                      

(iii) Producer gas              

(iv) Biogas                      

(iv) Hydrogen 

Partial Replacement: 

1. Blending                                      

2. Dual fueling 

7. According to Mixture Preparation 

1. Carburetion – perhaps soon to be obsolete. 

2. Fuel Injection 

(i)  Diesel      

(ii) Gasoline       

(a) Manifold        

(b) Port        

(c) Cylinder 

8. According to Ignition 

1. Spark Ignition - homogeneous charge  

(a) Conventional    

(i) Battery    

(ii) Magneto  

(b) Other methods 

2. Compression Ignition - heterogeneous charge (conventional) 

3. Compression ignition - homogeneous charge (hcci) 

9. According to Charge Stratification 

 1. Homogeneous Charge (Also Premixed charge) 

 2.  Stratified Charge 

(i) With carburetion        

(ii) With fuel injection

10. Combustion Chamber Design 

1. Open Chamber: 

(i)     Disc type                               

(ii)   Wedge                               

(iii)  Hemispherical           

(iv)  Bowl-in-piston           

(v)   Other design 

2. Divided Chamber: (For CI): 

(i)  Swirl chamber         

(ii)  Pre-chamber (For SI) 

(i)  CVCC

11.  According to Method of Load Control 

1. Throttling: (To keep mixture strength constant) Also called Charge Control  Used in the Carbureted S.I. Engine 

2. Fuel Control (To vary the mixture strength according to load)  Used in the C.I. Engine 

3. Combination  Used in the Fuel-injected S.I. Engine.

12. According to Cooling 

 1. Direct Air-cooling 

 2. Indirect Air-cooling (Liquid Cooling) 

 3. Low Heat Rejection (Semi-adiabatic) engine.

Terminology Used in IC Engine

1. Top dead center (T.D.C.) In a reciprocating engine the piston moves to and fro motion in the cylinder. When the piston moves upper direction in the cylinder, a point at which the piston comes to rest or change its direction known as top dead center. It is situated at top end of cylinder.

2. Bottom dead center (B.D.C.) When the piston moves in downward direction, a point at which the piston come to rest or change its direction known as bottom dead center. It is situated in bottom side of cylinder.

3. Stroke (L) The maximum distance travel by the piston in single direction is known as stroke. It is the distance between top dead center and bottom dead center.

4. Bore (b) The inner diameter of cylinder known as bore of cylinder.

5. Maximum or total volume of cylinder (Vtotal) It is the volume of cylinder when the piston is at bottom dead center. Generally, it is measure in centimeter cube (c.c.).

6. Minimum or clearance volume of cylinder (Vclearance) It is the volume of cylinder when the piston is at top dead center.

7. Swept or displace volume (Vswept) It is the volume which swept by the piston. The difference between total volume and clearance volume is known as swept volume.

Swept volume = Total volume – Clearance volume

8. Compression ratio The ratio of maximum volume to minimum volume of cylinder is known as the compression ratio. It is 8 to 12 for spark ignition engine and 12 to 24 for compression ignition engine.

Compression ratio = Total volume / Clearance volume 

9. Ignition delay It is the time interval between the ignition start (spark plug start in S.I. engine and inject fuel in C.I. engine) and the actual combustion starts.

10. Stroke bore ratio Stroke bore ratio is the ratio of bore (diameter of cylinder) to length of stroke. It is generally equal to one for small engine and less than one for large engine. 

Stroke bore ratio = Inner diameter of cylinder / length of stroke

11. Mean effective pressure The average pressure acting upon the piston is known as mean effective pressure. It is given by the ratio of the work done by the engine to the total volume of engine. 

Mean effective pressure = Work done by engine / Total volume of cylinder

Principal Parts of an Engine

The principal parts of an I.C engine, are as follows : 

1. Cylinder and cylinder liner, 

2. Piston, piston rings and piston pin or gudgeon pin, 

3. Connecting rod with small and big end bearing, 

4. Crank, crankshaft and crank pin

5. Valve gear mechanism.