CN113738500A

CN113738500A - Turbocharger for an internal combustion engine

Info

Publication number: CN113738500A
Application number: CN202110583292.6A
Authority: CN
Inventors: S·赫
Original assignee: Robert Bosch GmbH; Bosch Ltd
Current assignee: Robert Bosch GmbH; Bosch Ltd
Priority date: 2020-05-28
Filing date: 2021-05-27
Publication date: 2021-12-03

Abstract

The present invention relates to turbochargers for internal combustion engines. The present disclosure presents a turbocharger (102) for an internal combustion engine. The turbocharger (102) includes a turbine (1021), a compressor (1022), a bypass conduit (1025), an electronically controlled bypass valve (1023), and at least one precatalyst (1024). The turbine (1021) is in fluid communication at a first end with an exhaust manifold (1012) of the engine (101) and at a second end with an exhaust gas duct (1031). The bypass conduit (1025) allows exhaust gas flow between an exhaust manifold (1012) of the engine (101) and the exhaust gas pipe (1031). An electronically controlled wastegate (1023) is disposed inside the bypass duct (1025). The most important non-limiting feature of the presently claimed invention is a pre-catalyst (1024) placed in bypass conduit (1025) downstream of electronically controlled bypass valve (1023).

Description

Turbocharger for an internal combustion engine

Technical Field

The present disclosure relates to turbochargers for internal combustion engines.

Background

Turbochargers are turbine-driven forced induction devices that increase the efficiency and power output of an internal combustion engine by forcing additional air into the combustion chamber. A conventional turbocharger has two main components, a turbine and a compressor. The compressor of the turbocharger takes in ambient air and compresses it, after which the air enters the intake manifold at an increased pressure. This results in a greater mass of air entering the cylinder on each intake stroke. The power required to rotate the centrifugal compressor of the turbocharger is derived from the kinetic energy of the exhaust gases of the engine.

Some turbochargers have a wastegate, which is essentially a valve that diverts exhaust gas from the turbine wheel of the turbocharger to the wastegate. This diversion of exhaust gas adjusts the turbine speed, which adjusts the rotational speed of the compressor, which ultimately adjusts the maximum boost pressure. However, when the engine is cold and at lower part load, the turbocharger will not generate boost pressure but instead act as a heat sink, reducing the exhaust gas temperature and increasing the warm-up time of the main catalyst in the exhaust pipe. It is necessary to utilize the thermal energy of the exhaust gases during the cold phase by bypassing the exhaust gases from the exhaust manifold through a bypass valve.

Patent application "US 2010011764a 1-thermally operated bypass valve for passive warm-up control of aftertreatment devices" discloses a passive thermally controlled bypass valve to enable exhaust gases to bypass the loss of enthalpy created by the turbine wheel driving the turbocharger and thus more quickly transfer heat to the catalyst or aftertreatment. In order for automotive exhaust catalysts to function, they must be at operating temperatures. When the engine is cold started, the vehicle (including the exhaust system and any aftertreatment devices located therein) is at ambient temperature. Because sixty to eighty percent of total emissions occur at engine cold starts and idle speeds of up to 120 seconds, the catalyst must function as quickly as possible.

Disclosure of Invention

The present invention provides a turbocharger for an internal combustion engine, the turbocharger comprising a turbine in fluid communication at a first end with an exhaust manifold of the engine and at a second end with an exhaust pipe, and at least one bypass conduit allowing exhaust gas flow between the exhaust manifold and the exhaust pipe of the engine, an electronically controlled bypass valve being disposed inside the bypass conduit, characterized by a pre-catalyst disposed in the bypass conduit downstream of the electronically controlled bypass valve.

Drawings

Embodiments of the invention are described with reference to the following drawings:

FIG. 1 depicts an engine (101) flow diagram for a vehicle arrangement.

Detailed Description

FIG. 1 depicts an engine (101) flow diagram for a vehicle arrangement. A vehicle arrangement includes an internal combustion engine, a turbocharger (102), an intercooler (104), and at least one exhaust treatment conduit. The internal combustion engine (101) further comprises an intake manifold (1011) and at least one exhaust manifold (1012). The exhaust manifold (1012) is in fluid communication with the turbocharger (102). The intake manifold (1011) is in fluid communication with an intercooler. The intake manifold (1011) receives additional mass of compressed air from the turbocharger (102) via the intercooler (104). The exhaust gas treatment pipe comprises, among other components known to the person skilled in the art, at least one main catalyst (103).

The turbocharger (102) includes a turbine (1021), a compressor (1022), a bypass conduit (1025), an electronically controlled bypass valve (1023), and at least one precatalyst (1024). The turbine (1021) is in fluid communication at a first end with an exhaust manifold (1012) of the engine (101) and at a second end with a waste gas duct (1031). The bypass conduit (1025) allows flow of exhaust gas between an exhaust manifold (1012) and an exhaust gas pipe (1031) of the engine (101). An electronically controlled bypass valve (1023) is disposed inside the bypass conduit (1025). The most important non-limiting feature of the presently claimed invention is a pre-catalyst (1024) placed in bypass conduit (1025) downstream of electronically controlled bypass valve (1023). The precatalyst (1024) is a diesel oxidation catalyst [ DOC ] or a Lean NOx Trap catalyst (Lean NOx Trap) [ LNT ].

An electronically controlled bypass valve (1023) is a valve that diverts exhaust gas from a turbine (1021) of the turbocharger (102) to a pre-catalyst (1024) and further into an exhaust pipe (1031) via a bypass conduit (1025). The opening and closing of the valve is controlled by the ECU. In the case of a variable geometry turbocharger without an active wastegate, the bypass valve (1023) can be a specially designed ECU controlled valve. If already present, the active wastegate can also be used as a bypass valve (1023) for this purpose. However, a specially designed bypass valve (1023) is preferred because the active wastegate is designed to exhaust the exhaust gas at high temperatures with large exhaust mass. This exposes the pre-catalyst (1024) to high exhaust temperatures that cause thermal shock.

The primary catalyst (103) in a diesel engine is a diesel oxidation catalyst [ DOC ] or a lean NOx trap catalyst [ LNT ], and additionally the vehicle may or may not have a Selective Catalytic Reduction (SCR) based DeNOx system. The pre-catalyst of the turbocharger (102) is independent of the main catalyst and can be a diesel oxidation catalyst [ DOC ] or a lean NOx trap catalyst (LNT) with appropriate measures for regeneration of the LNT. However, in terms of volume, the pre-catalyst has a much smaller volume than the main catalyst.

Before the catalyst can operate effectively, the catalyst needs to be at a specific temperature, the so-called light-off temperature [ typically 180 ℃ and above ]. Until this temperature is reached, the DeNOx system will not work efficiently. The main catalyst (103) therefore requires a minimum activation energy, which is supplied by exhaust heat. However, when the engine (101) is cold and at a lower part load, the turbocharger (102) does not generate boost pressure, but instead acts as a heat sink, reducing the temperature of the exhaust gas and increasing the warm-up time of the main catalyst (103).

This thermal energy of the exhaust gases is utilized by the present invention during the cold phase of the engine (101). An electronically controlled bypass valve (1023) is opened during the cold phase. This allows exhaust gas from the exhaust manifold (1012) to bypass the turbocharger (102) and flow through the small, low exhaust temperature optimized pre-catalyst (1024) in the bypass conduit (1025). The pre-catalyst, which has a smaller volume than the main catalyst (103), heats up faster and can therefore be used to further increase the exhaust gas temperature by means of an exothermic reaction. This in turn causes the primary catalyst (103) to warm up more quickly and allows for more efficient conversion of emissions from the cold engine.

During high load operation and warm-up conditions, the electronically controlled bypass valve (1023) is closed. Thus, exhaust gas from the exhaust manifold (1012) now flows to the turbine (1021) of the turbocharger (102). The turbocharger (102) now performs its normal operation, i.e. the exhaust gas drives the turbine (1021) of the turbocharger (102), which regulates the rotational speed of the compressor (1022), which ultimately returns the boost pressure to the intake manifold (1011) of the engine. Because the precatalyst (1024) will be exposed to the exhaust gas for a very short duration and at low temperature, it will experience less thermal shock and trailer engine life has better life and efficiency.

This idea of developing a turbocharger (102) for an internal combustion engine (101) allows for faster release of warming measures and effective reduction of cold emissions. Which efficiently uses the energy of exhaust gas to warm up a main catalyst in a cold stage of an engine (101) and reduces emissions in the cold stage.

It must be understood that the examples explained in the above detailed description are illustrative only and do not limit the scope of the invention. Any modification to a turbocharger (102) for an internal combustion engine (101) is contemplated and forms part of the present invention. The scope of the invention is limited only by the claims.

Claims

1. A turbocharger (102) for an internal combustion engine, the turbocharger (102) comprising a turbine (1021) and at least one bypass duct (1025), the turbine (1021) being in fluid communication at a first end with an exhaust manifold (1012) of the engine (101) and at a second end with a wastegate (1031), the bypass duct (1025) allowing exhaust gas flow between the exhaust manifold (1012) and the wastegate (1031) of the engine (101), an electronically controlled bypass valve (1023) being disposed inside the bypass duct (1025), characterized by a pre-catalyst (1024) disposed in the bypass duct (1025) downstream of the electronically controlled bypass valve (1023).

2. The turbocharger (102) for an internal combustion engine (101) of claim 1, wherein the pre-catalyst is a diesel oxidation catalyst [ DOC ] or a lean NOx trap catalyst [ LNT ].