Patent GB-1377942-A (GB)
Title: Afterburning of exhaust gases from internal combustion engines
IPC: F01N13/02
Filed: 1973-03-09
Abstract: 1377942 Treating I C engine exhaust gas P AUGUST 9 March 1973 [10 March 1972 10 Aug 1972] 11654/73 Heading F1B Exhaust gas afterburner has a main passage 2 divided into two parts by a control element 3, the part upstream of the control element having openings 6 which communicate with an annular catalyst containing chamber 8 disposed around the main passage, and is characterized in that the part 2 of the passage downstream of the control element constitutes an afterburner and is in heat conducting relationship with the catalyst chamber. Chamber 8 contains a catalyst for reducing nitrogen oxides, treated gases leave this chamber through perforations in plate 14 and enter chamber 10, where they mix with additional air which enters through inlet 21. Mixing is promoted by vanes 11 and the air/gas mixture then passes through perforated plate 15 into a third chamber 12 which contains an oxidizing catalyst. The gases then pass through perforated plate 13 into a frusto-conical portion of the casing and hence into exhaust pipe 17. An outwardly turned lip 20 at the downstream end of the main passage provides for continued mixing of the gases as they enter pipe 17. The control element 3 is biased by a spring 4 to the closed position but when the engine load exceeds that corresponding to a vehicle speed of 60 to 80 kw/hr the control element opens progressively and allows an increasing proportion of the exhaust gases to flow through the part 2 of the main passage. Control element 3 reaches the fully open position when the engine throttle valve is about ¥ open. The diameter of the outlet end of the main passage is slightly reduced so that even when the control element is fully open, some gas flows through the catalyst chambers. Spaced along the main passage bore are apertured rings which promote mixing of the gases. In order to heat the catalysts rapidly to their operating temperature, when starting a cold engine, secondary air is admitted upstream of the inlet to the first catalyst chamber 8. Movement of control element 3 away from the closed position is prevented, until the engine coolant or the catalysts reach a predetermined temperature, by an electromagnetically actuated sear which engages the free end of a lever arm secured to the control element spindle. The electromagnet is energized to withdraw the sear by the closing of a temperature responsive switch. The catalysts are protected against overheating by a second electromagnet, energized through another temperature responsive switch and which pulls the control element to the open position. In a modification, Fig. 4, the exhaust gases always flow through the first catalyst chamber 42, secondary air is injected through a pipe 57 and a control element 48, when closed, diverts the air gas mixture through holes 46 to a chamber 44 containing an oxidizing catalyst. Secondary air is provided by a pump, having a throttle valve in its outlet, the throttle valve being mechanically linked to the engine throttle valve so that the secondary air supply is proportional to the engine operating conditions.