Cumbustion Chamber Manish K.MISTRY [100150735008] Government college of engineering , Bhuj

Combustion chambers (C.I.) More difficult design than s.i. engine due to mixing of fuel ,evaporation ,burning inside c.c. High turbulence of air require in c.c. which is possible with swirling motion. Swirling air creates -high turbulence -better mixing -high rate of fuel evaporation

Types of swirl Induction swirl Compression swirl Combustion swirl

Induction swirl During suction stroke forcing air for rotational movement.(a) By masking one side of inlet valve (b) By lip over one side of inlet valve (c)

Compression swirl Air from periphery is forced to the centre cavity of the piston during c.s. The squishing of air is created and forced to enter tangentially in the piston cavity when the piston reach to TDC

Combustion swirl Created due to partial combustion so called as a COMBUSTION INDUCED SWIRL. Only for pre combustion chamber Combustion during delay period in p.c.c. so A:F mixture become rich and forced the gases with high velocity in main c.c. Creat high temp and provides better combustion

Types of combustion chamber for C.I. engine Open C.C. Pre –C.C. Turbulent C.C. Special C.C.

Open combustion chamber (DIC) All combustion air is compressed and at a time fuel injected, and all air contained in a single space. That’s why also called as DIC.

Various shapes of piston crown with flat cylinder head. Shallow depth c.c. for large capacity engine with law speed Hemispherical cavity better than a. Cylindrical cavity(leyland heavy vehicle ) better squish than a & b. Very powerfull squish , better combustion ,reduced delay period

Open combustion chamber (DIC) For better mixing and better burning condition shape of cylinder head provided a cavity.

Open cumbustion chamber (DIC) Advantage simple in construction less heat losses , higher thermal efficiency easy starting long delay period can be used (less cost fuel ) higher mechanical efficiency

Open combustion chamber (DIC) Disadvantage excess air required is large. higher injection pressure with multihole nozzel is required ,holes are too small that’s possibility of clogging of holes. higher maintenance cost.

Pre combustion chamber Chamber divided into two parts -bet piston and cylinder head -in cylinder head Upward movement of piston forces the air to flow in pre c.c. importing a directional movement to the air ( swirl) Swirl is maxi at about 15 degree before TDC. Fuel is injected into pre-c.c. Orifice passage connecting the pre- and main c.c. to distribute unburned and partially burned fuel . Pre- c.c. nearly 25-30% of total air charged. P.C.C. runs hot and helps for easy evaporation of fuel injected and reduces delay period

Shapes of Pre combustion chamber

Advantages of Pre- C.C. Low injection pressure can be used so single hole nozzle can be used. Can used wide range of fuels Smooth combustion. Knocking tendency is totally removed due to no delay Air and fuel spray patterns are not important Operated at high RPM

Disadvantages of Pre- C.C. Fuel consumption is high. Heat loss from p.c.c. is higher. Cylinder required special types of materials. Starting heat loss is higher Thermal efficiency is low for partial load

Turbulent combustion chamber. Also known as swirl chamber as very high swirl is created. Arrangement is same as p.c.c. except 90-95% of total air is pushed in the p.c.c. Injection pressure and pattern of injection are not very important. Engine can be operated at very high RPM without late burning.

Various Turbulent combustion chamber.

Advantages of Turbulent combustion chamber. Wide range of fuels can be used . Low A:F ratio can be used as air is heavily swirled . Engine can operated at high RPM. Injection pressure and pattern are not very important so design and selection of nozzle is easy. Low rate of pressure rise and smooth running of engine .

Disadvantages of Turbulent combustion chamber Starting of engine is difficult as heat losses are high. Mechanical efficiency is low . Because of high heat losses , bsfc is higher.

Special combustion chamber Lanova or Air cell c.c. - burning of fuel forms two vortices as shown in fig. which further improves the mixing and burning.

Air cell has two parts major and minor . First burning starts in the minor cell and pushes the burning air in the main chamber . Pressure in the minor cell falls because of discharging the gases, the major cell starts pushing burning gases into main c.c. This steps motion of gases creates high swirling motion in main c.c. and reduces delay period.

Advantages of Special combustion chamber Mixing of air and fuel is minimised after starting the combustion . Easy starting . High power o/p. Very good mixing of fuel and air takes place’ Engine run smoothly.

Disadvantages of Special combustion chamber Low thermal efficiency. High bsfc

M- combustion chamber Developed by Dr. Meurer . Open c.c. ,having a combustion cavity in piston as shown in fig. Cavity remain very hot , fuel evaporates quickly. Main advantage is the deposition ,which occurs in atomized fuel burning is prevented because , hot surface provides an excellent means of evaporation without affecting fuel moleculer structure .

Advantages of M- combustion chamber Low rate of pressure rise. Low peak pressure . Ability to operate on a wide range of liquid fuels . No combustion noise.

Disadvantages of M- combustion chamber Cold starting difficulty. Some white smoke , diesel odour and high H.C. emission during starting and idling condition of engine .