Patent GB-1421821-A (GB)
Title: Afterburning of exhaust gases in internal combustion engines
IPC: F02M23/04
Filed: 1973-03-20
Abstract: 1421821 Treating exhaust gas; treating charge DEUTSCHE VERGASER GmbH & CO KG 20 March 1973 [10 Nov 1972] 13342/73 Heading B1W [Also in Division Fl]  A method of metering extra air to be burnt in an I.C. engine afterburner using a controller for optimising combustion of the exhaust gas in the afterburner in which signals corresponding to at least three parameters indicative of engine operating conditions and having non- linear functional relationships are applied at all times to the controller, the parameters being:- (1) the induction pipe pressure, (2) the engine speed, and (3) either the back pressure of the exhaust gas or a signal corresponding to the chemical composition of the exhaust gas upstream of the afterburner. An I.C. engine 11, draws fuel-air mixture from a carburettor 13, exhausts into a pipe 15 leading to an afterburner 16 and drives an air-pump which supplies air to the afterburner through a pipe 39 and a control valve 21. Intake pipe pressure is communicated to the valve through a pipe 36. The valve 21 comprises a body 23 divided by diaphragm 24 and 25 into pressure chambers 26 and 27 which are connected respectively to the intake pipe and the exhaust pipe. Rigid partitions 28 and 29 define a chamber 31 connected to the pump 17, a chamber 32 connected to the exhaust pipe and a chamber 30 connected by a pipe 22 to the inlet of the pump. Two valve cones 34 and 35 which co-operate with seatings in the rigid partitions are mounted on a common spindle 33 attached to both the diaphragms 24 and 25. A spring 42 biasses the spindle to a position in which the cone 34 is seated. Operation: The pump 17 delivers a volume of air dependent on the engine speed and if the intake pipe absolute pressure is high, the cone 34 is seated and secondary air flows past the cone 35 to the afterburner. As the intake pipe pressure falls the cone 34 is unseated and some of the air delivered by the pump 17 is recirculated to the pump inlet. High back pressure in the exhaust pipe is communicated by the pipe 37 to the chamber between the diaphragms and produces a net force tending to seat the cone 34. In a first modification, Fig 2 (not shown) the pipe 37 is replaced by a passage through the valve spindle 33. In a second modification, Fig. 3 (not shown) the cone 34 is movable axially on the spindle and is spring biassed against a shoulder on the spindle i.e. to a position corresponding to that shown in Fig. 1. The cone 34 can thus unseat to relieve excessive pump delivery pressure. The pipe 36 is also connected to the chamber 26 through a check valve allowing free inflow to the chamber but restricting outflow. In a third modification, Fig. 4, a platinum coated zirconia sensor 53 responsive to either the oxygen or carbon monoxide content of the exhaust gas is provided and is electrically connected to a signal convertor 55, connected to a d.c. source by a line 56. The convertor operates a three way electro-magnetic valve 52 which connects a pipe 51a alternately for different periods of time with the pipe 51 and the pipe 61, in accordance with the duration of pulses coming from the convertor 55. The pipe 61 includes a check valve 59 and a reservoir 60. In a fourth modification, the valve 52 is replaced by two valves, one in the pipe 51 and another in the pipe 61, both the valves being actuated by pulses from the convertor 55. In a fifth modification there is only one electro magnetically operated valve actuated by pulses from the convertor and it is in the delivery line from the chamber 32 to the exhaust pipe. In a sixth modification, the secondary air is fed into the intake pipe instead of into the exhaust pipe. The control devices, Fig. 7, comprise a valve 21, as in Fig. 1, a valve 64 in the delivery line from the chamber 32 and downstream of this valve a pressure regulator valve 65 includes a valve member which opens only when the pressure in the chamber exceeds a value determined by a spring 71, and this pressure acts through a pipe 37 in the chamber 27 between the diaphragms.