Low emission combustion chamber

A combustion chamber concentric about an axis and having outer wall means and inner wall means supported in spaced relation to define an annular combustion chamber cavity therebetween and wherein said outer wall means and inner wall means are shaped so as to define:

• A. an annular pilot combustion zone positioned at the combustion chamber forward end,
• B. trigger means in the form of a corrugated ring having corrugations canted with respect to the axis and increasing an amplitude in a downstream direction and positioned at the downstream end of the pilot combustion zone to impart swirl about the axis to the pilot zone products of combustion,
• C. an annular primary combustion zone located downstream of said pilot trigger and shaped to increase in cross-sectional area in a downstream direction so as to be in the form of a diffuser,
• D. a primary combustion zone trigger mechanism in the form of a corrugated ring mounted concentrically about the axis and having corrugations canted with respect to the axis and increasing in amplitude in a downstream direction and supported to be located at the entrance of the primary combustion zone and spaced axially downstream from the pilot trigger so that the pilot zone products of combustion will pass over the convolutions of both triggers,
• E. means to pass selected quantities of combustion air over the opposite corrugation surfaces of both triggers to produce accelerated mixing between the fluids passed over opposite surfaces of the triggers,
• F. means to introduce fuel droplets into the combustion chamber and circumferentially thereabout at an axial station between said triggers, and
• G. means to provide dilution air to the interior of the combustion chamber downstream of the primary combustion zone.

The method of producing low NOx combustion in a combustion chamber comprising the steps of:

• A. producing hot, fully combusted, pilot exhaust gases of reduced oxygen content,
• B. mixing a selected quantity of cool, swirling air with the pilot exhaust gases to produce a first swirling mixture having selected temperature lower than the pilot exhaust gases but above the vaporization temperature of the fuel to be utilized in the combustion chamber, and of reduced oxygen content so that the first swirling mixture has an ER less than one,
• C. injecting atomized fuel into the first swirling mixture in selected quantity to produce a second swirling mixture of fuel and air of reduced oxygen content so that the second swirling mixture has a first ignition delay time to prevent autoignition of the atomized fuel droplets, said second swirling mixture also having a selected temperature to vaporize the fuel so that said second swirling mixture is a vaporized, swirling fuel-air mixture having a reduced oxygen content to produce autoignition at the culmination of the first time delay, and
• D. mixing a selected quantity of swirling combustion air with the second swirling mixture to effect molecular mixing between the fuel and air since both the second mixture and combustion air are swirling, and in selected quantity to produce a third swirling, vaporized fuel-air mixture of oxygen level greater than that of said second mixture to effect a new and reduced ignition delay time so as to autoignite the third mixture at an ER less than one and at a time sooner than the expiration of the first ignition delay time to thereby reduce the dwell time of the engine air at NOx creating temperature.

The method of producing combustion in a combustion chamber with low NOx emission comprising the steps of:

• A. producing hot, vitiated products of combustion in a pilot burner,
• B. cooling the pilot products of combustion to a temperature where they will vaporize selected fuel but retain their vitiated condition and causing them to swirl about an axis,
• C. introducing fuel in droplet form into the swirling, vitiated, cooled pilot products of combustion to produce flash vaporization of the fuel due to the high relative velocity between the fuel droplets and the swirling, vitiated products of combustion and due to the centrifugal force existing between the vitiated products of combustion and the fuel droplets so injected so as to produce a swirling, fully vaporized, fuel-air mixture having an oxygen content to establish a selected time delay to autoignition,
• D. introducing swirling combustion air to said vaporized, swirling fuel-air mixture to establish molecular premixing of the fuel and air and increase the oxygen content thereof to reduce the time lag and cause autoignition at an ER less than unity to thereby produce high-rate, lean burning of said premixed mixture so as to effect low NOx emission due to a combination of minimum dwell time of air above the NOx forming temperature and the high-rate, lean burning due to molecular premixing.