Method and arrangement for reducing an nox content in the exhaust gas of an internal combustion engine in a vehicle

The method according to one of the preceding claims, characterized by keeping the rotational speed of the combustion engine (10) in a range between 800 rpm and 1500 rpm, preferably between 850 rpm and 1300 rpm.

The method according to one of the preceding claims, characterized by keeping a variation of the rotational speed of the combustion engine (10) below 200 rpm.

The method according to one of the preceding claims, characterized in that the temperature of the exhaust gas downstream of the two energy absorbers (54, 60) is established in a temperature range which is within an optimum range for reducing NOx in a NOx reducing catalyst (46) in the exhaust after treatment system (40).

The method according to one of the preceding claims, characterized by establishing a lambda-ratio (λ) of the fuel/air mixture supplied to the combustion engine (10) of not more than 1.4.

An arrangement for reducing the NOx emissions of a combustion engine (10) for performing the method according to anyone of the preceding claims, comprising an internal combustion engine (10) with at least one cylinder (11), an intake (12) for the supply of air, an exhaust outlet (14) for discharging exhaust gases into an exhaust after treatment system (40) for reducing emissions of the internal combustion engine (10), an exhaust gas recirculation (80) supplying exhaust gas from the exhaust outlet (14) to the intake (14) of the internal combustion engine (10), and at least two energy absorbers (54, 60) in series in the exhaust flow downstream of the exhaust outlet (14), characterized by

• (a) a transmission unit (30) coupled between the internal combustion engine (10) and a drive shaft (16) of the vehicle which allows for a predetermined rotational speed of the internal combustion engine (10) for overheating the exhaust gas;
• and
• (b) exhaust gas energy is absorbable in the at least two energy absorbers (54, 60) to establish a temperature of the exhaust gas in a desired temperature range for NOx conversion in the after treatment system (40) depending on the rotational speed of the combustion engine (10).

A method for reducing an NOx-content in the exhaust gas of an internal combustion engine in a vehicle, the combustion engine comprising at least one cylinder, an intake for the supply of air, an exhaust outlet for discharging exhaust gases into an exhaust after treatment system for reducing emissions of the internal combustion engine, wherein an exhaust gas recirculation supplies exhaust gas from the exhaust outlet to the intake of the internal combustion engine, and at least two energy absorbers in series in the exhaust flow downstream of the exhaust outlet absorb energy of the exhaust gas, wherein the exhaust gas is overheated to a first temperature by driving the combustion engine in a range of rotational speed producing hot exhaust gas at the exhaust outlet, wherein the first temperature is sufficient to drive the at least two energy absorbers, wherein a temperature of the exhaust gas is established downstream of the at least two energy absorbers sufficient to remove NOx from the exhaust gas in the exhaust after treatment system with an efficiency of more than 80%.

An arrangement for reducing the NOx emissions of a combustion engine (10) for performing the method according to anyone of the preceding claims, comprising an internal combustion engine with at least one cylinder, an intake for the supply of air, an exhaust outlet for discharging exhaust gases into an exhaust after treatment system for reducing emissions of the internal combustion engine, an exhaust gas recirculation supplying exhaust gas from the exhaust outlet to the intake of the internal combustion engine, and at least two energy absorbers in series in the exhaust flow downstream of the exhaust outlet (14), wherein

• (a) a transmission unit is provided coupled between the internal combustion engine and a drive shaft of the vehicle which allows for a predetermined rotational speed of the internal combustion engine for overheating the exhaust gas;
• and
• (b) exhaust gas energy is absorbable in the at least two energy absorbers to establish a temperature of the exhaust gas in a desired temperature range for NOx conversion in the after treatment system depending on the rotational speed of the combustion engine.