COMBUSTION CHAMBERS - National Institute of Technology

INTERNAL COMBUSTION ENGINES (ELECTIVE) (ME667)SIXTH SEMESTERAdvantages:(i) Due to short or practically no delay period for the fuel entering the main combustionspace, tendency to knock is minimum, and as such running is smooth.(ii) The combustion in the third stage is rapid.(iii) The fuel injection system design need not be critical. Because the mixing of fuel l andair takes place in pre-chamber,Disadvantages:(i) The velocity of burning mixture is too high during the passage from pre-chambers, sothe heat loss is very high. This causes reduction in the thermal efficiency, which can beoffset by increasing the compression ratio.(ii) Cold starting will be difficult as the air loses heat to chamber walls duringcompression.Energy cell :The ‘energy cell’ is more complex than the pre-combustion chamber. As the piston moves up on thecompression stroke, some of the air is forced into themajor and minor chambers of the energy cell. Whenthe fuel is injected through the pintle type nozzle, partof the fuel passes across the main combustionchamber and enters the minor cell, where it is mixedwith the entering air. aCombustion first commences inthe main combustion chamber where the temperatureis higher, but the rate of burning is slower in thislocation, due to insufficient icient mixing of the fuel and air. The burning in the minor cell isslower at the start, but due to better mixing, progresses at a more rapid rate. Thepressure built up in the minor cell , therefore , force the burning gases out into the mainchamber, thereby creating added turbulence and producing better combustion in thethis chamber. In mean time, pressure is built up in the major cell which then prolongsthe action of the jet stream entering the main chamber, thus continuing to induceturbulence in the main chamber.Jagadeesha T, Assistant Professor, Department of Mechanical Engineering, Adichunchanagiri Institute of Technology, Chikmagalur