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Device for controlling EGR flow

IP.com Disclosure Number: IPCOM000239220D
Publication Date: 2014-Oct-22
Document File: 7 page(s) / 410K

Publishing Venue

The IP.com Prior Art Database

Abstract

A flow control device for an EGR channel at an internal combustion engine comprises a mixing section with variable geometry. Thereby the desired amount of transferred EGR can be achieved at most load cases. The variable geometry is achieved by adjustable walls in the mixing section, which can typically be designed as a dual-flap valve, where each flap has a bend and is rotatably mounted in the outer wall of the mixing section.

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Device for controlling EGR flow

ABSTRACT

A flow control device for an EGR channel at an internal combustion engine comprises a mixing section with variable geometry. Thereby the desired amount of transferred EGR can be achieved at most load cases. The variable geometry is achieved by adjustable walls in the mixing section, which can typically be designed as a dual-flap valve, where each flap has a bend and is rotatably mounted in the outer wall of the mixing section.

BACKGROUND

In turbo-supercharged diesel engines it is previously known to recycle exhaust gases to the engine inlet in order to reduce contents of nitrous oxides in the exhaust gases. Hereby the recycled exhaust gases function so as to lower the combustion temperature resulting in that a smaller amount of the nitrogen in the inlet air can be converted into nitrogen oxides. This process, usually called EGR (exhaust gas recirculation) has often as a way of reducing the contents of harmful exhaust gas emissions.

One particular problem when using EGR in a Diesel engine is that the combustion normally occurs with excess air. This indirectly results in need of transferring relatively large amounts of exhaust gases during a relatively large operating range of the engine in order to achieve the desired function. This problem is accentuated in case of an engine of the super-charged type, where the pressure in the intake system of the engine is greater than the pressure in the exhaust gas system during a great part of the operating range.

Among known solutions to be used in supercharged engines, two main principle solutions can be distinguished, usually named “short route EGR” and “long route EGR”. In the first-mentioned case exhaust gases are taken from a position before an exhaust turbine in the exhaust system and is recycled to a position after an intake air compressor in the intake system. In the latter case exhaust gases are taken from a position after the exhaust turbine and are recycled to a position before the intake air compressor. Both of these principle solutions have advantages and disadvantages.

In supercharged diesel engines having double exhaust collectors, sometimes only exhaust gases from one of the exhaust collectors are used as an EGR source. This however results in an uneven EGR flow which in turn may affect the engine with a correspondingly uneven operation as result.

In devices where both exhaust collectors are being used as an EGR source, a more even EGR flow can be obtained. At the fusion of the gas streams, a cross flow easily occurs from the channel where, at the moment, a higher pressure prevails to the channel where a lower pressure prevails. This will result in a lower pressure of accessible EGR gases and thus increased power is needed in order to pump the EGR gases into the intake channel of the engine.

A solution to this problem is presented in EP1290328 B1 (EP’328). According to EP’328, a short route EGR channel leads exhausts from the exhaust si...