Abstract: A process and system are provided for automatically controlling the fraction of the exhaust gas quantity returned to an internal-combustion engine with respect to the mixture quantity fed on the whole to the internal-combustion engine, which mixture quantity is formed by the returned exhaust gas quantity and a fresh air quantity. The actual fraction of the returned exhaust gas quantity with respect to the mixture quantity fed on the whole to the internal-combustion engine is determined by sensors from measurements of the temperature of the fed fresh air quantity, the temperature of the returned exhaust gas quantity and the temperature of the mixture quantity fed as a whole. This actual fraction of the returned exhaust gas quantity is adapted to a predetermined desired fraction.

Abstract: In a method and apparatus for operating an internal combustion engine having an air intake duct for supplying combustion air to the engine, an exhaust pipe for discharging exhaust gases from the engine, and an exhaust gas recirculation pipe extending between the exhaust pipe and the air intake duct and including an exhaust gas recirculation valve, oxygen sensors are provided in the air intake pipe and in the exhaust duct and are connected to a control unit which determines from the signals generated by the oxygen sensors the actual exhaust gas recirculation rate and dependent thereon controls the exhaust gas recirculation valve so as to generate a desired exhaust gas recirculation flow for the momentary engine operating point.

Abstract: In an internal combustion engine with a turbocharger including a turbine and a charge air compressor an exhaust gas recirculation line branches off the exhaust pipe downstream of the turbine and leads to a three way mixing valve which is also in communication with a fresh air supply line through which fresh air is supplied to the charge air compressor and then, under increased pressure to the engine, and from which a supply line extends to the fresh air supply line downstream of the charge air compressor, and means are disposed in the supply line for increasing the pressure of the gas in the supply line to the pressure of the fresh air downstream of the charge air compressor for admixing the gas mixture prepared by the mixing valve to the fresh air supplied to the engine.

Abstract: In a method for reducing harmful emissions of a multi-cylinder internal combustion engine including for each cylinder intake and exhaust passages with intake and exhaust valves and an exhaust gas recirculation passage extending between an exhaust passage and the interior of a cylinder and including an exhaust gas recirculation valve, the exhaust gas recirculation valve of a first cylinder is opened during the intake cycle of the first cylinder at the beginning of the exhaust cycle of a second cylinder associated with the first cylinder and the exhaust gas recirculation valve is closed when the exhaust gas pressure in the exhaust gas recirculation passage from the second cylinder to the first cylinder falls below the combustion chamber pressure in the first cylinder or the charge air pressure in its intake passage or when a predetermined amount of exhaust gas has been recirculated.

Abstract: In an internal combustion engine with an exhaust gas recirculation system and an exhaust gas turbocharger having a turbine arranged in an exhaust gas duct and a compressor operated by the turbine and being disposed in an air supply duct for supplying charge air to the engine, an exhaust gas recirculation line extends between the exhaust gas duct upstream of the turbine and the air supply duct and downstream of the compressor. Cooling means are arranged in the exhaust gas duct and heating means are arranged in the air supply duct upstream of the compressor to permit the generation of a pressure differential between the exhaust gas duct and the air supply duct which provides for an exhaust gas recirculation flow through the exhaust gas recirculation line over a large engine operating range.

Abstract: In an internal combustion engine with exhaust gas recirculation wherein the engine has a charge air intake pipe for supplying combustion air to the engine, an exhaust pipe for discharging exhaust gas from the engine and an exhaust gas recirculation line extending between an exhaust gas recirculation valve arranged in the exhaust pipe and the charge air intake pipe for the controllable return of exhaust gas to the charge air intake pipe, a heat exchanger is disposed in the exhaust gas recirculation line and means are provided for supplying air under pressure to the heat exchanger for cleaning the heat exchanger.

Abstract: An exhaust gas aftertreatment device for internal combustion engines having a catalyzer for the selective catalytic reduction of oxides of nitrogen from exhaust gases of motor vehicle diesel engines, provides overstoichiometric supply of NH.sub.3 or materials releasing NH.sub.3. A first sensor records the NH.sub.3 concentration contained in the exhaust gas and interrupts the supply of the NH.sub.3 quantity when a specified upper threshold value is reached. A second sensor records the NH.sub.3 adsorbed in the catalyzer, by way of which the NH.sub.3 supply is resumed on reaching a specified lower threshold value. Alternatively, only one NH.sub.3 sensor is provided in the exhaust gas aftertreatment device. The NH.sub.3 concentration determined by this single sensor is compared, as the actual value, with a required value corresponding to a specified NH.sub.3 concentration in order to form a correction signal which is used for triggering the metering appliance continuously connected into the gas phase.

Abstract: An amplitude ratio and phase-difference analysis can be carried out with a measured object provided with a measured branch which is divided from a reference branch from a supply oscillator. The measured branch has 2.sup.n switching combinations of phase shifters which are decoupled from one another and operated by a controller. The branches then feed a mixer and through a band-pass filter calculating circuit for determining the relative amplitude and phase which can be displayed on a register.