Field of the invention
[0001] The present disclosure relates to a turbocharger for an
internal combustion engine.
Background of the invention
[0002] A turbocharger is a turbine-driven forced induction device
that increases an internal combustion engine’s efficiency and power output by forcing extra air into the combustion chamber. A conventional turbocharger has two principle components a turbine and a compressor. The turbocharger’s compressor draws in ambient air and compresses it before it enters into the intake manifold at increased pressure. This results in a greater mass of air entering the cylinders on each intake stroke. The power needed to spin the centrifugal compressor of the turbocharger is derived from the kinetic energy of the engine’s exhaust gases.
[0003] Some turbochargers have waste gate which is basically a
valve that diverts exhaust gases away from the turbine wheel of the turbocharger towards the exhaust gas pipe. This diversion of exhaust gases regulates the turbine speed, which regulates the rotating speed of the compressor, which ultimately regulates the maximum boost pressure. However when the engine is cold and at lower part loads, the turbocharger will not be generating the boost pressure but instead acts as a heat sink reducing the temperature of exhaust gas and increasing the heating up time

for the main catalyst in exhaust gas pipe. There is a need to utilize the heat energy of the exhaust gases during cold phase by bypassing the exhaust gases from exhaust manifold via a bypass valve.
Patent application “US2010011764A1- Thermatically operated bypass valve for passive warmup control of after treatment device.” discloses a passive thermatically controlled bypass valve to enable the exhaust flow to bypass the enthalpy loss incurred by driving the turbine wheel of a turbocharger, and thus more rapidly deliver heat to the catalyst or after-treatment. In order for automobile exhaust catalysts to function they must be at operational temperatures. When an engine starts from cold the vehicle, including the exhaust system and any after-treatment device located therein, is at ambient temperature. Since 60 percent to 80 percent of the total emissions emitted occur at engine cold start and idle up to 120 seconds, it is imperative that the catalyst function as fast as possible. This invention provides
Brief description of the accompanying drawings
[0004] An embodiment of the invention is described with
reference to the following accompanying drawing:
[0005] Figure 1 depicts an engine (101) flow diagram for a vehicle
set-up.

Detailed description of the drawings
[0006] Figure 1 depicts an engine (101) flow diagram for a vehicle
set-up. The vehicle set-up comprises an internal combustion engine, a turbocharger (102), an intercooler (104) and at least an exhaust gas treatment pipe. The internal combustion engine (101) further comprises an intake manifold (1011) and at least an exhaust manifold (1012). The exhaust manifold (1012) is in fluid communication with the turbocharger (102). The intake manifold (1011) is in fluid communication with the intercooler. The intake manifold (1011) receives an extra mass of compressed air from the turbocharger (102) via the intercooler (104). The exhaust gas treatment pipe comprises at least a main catalyst (103) amongst the other components known to person skilled in art.
[0007] The turbocharger (102) comprises a turbine (1021), a
compressor (1022), a bypass conduit (1025), an electronically controlled bypass valve (1023) and at least a precatalyst (1024). The turbine (1021) is in fluid communication with the exhaust manifold (1012) of the engine (101) at a first end and with the exhaust gas pipe (1031) at a second end. The bypass conduit (1025) permits the flow of exhaust gases between the exhaust manifold (1012) of the engine (101) and the exhaust gas pipe (1031). The electronically controlled bypass valve (1023) is placed inside the bypass conduit (1025). The most important non-limiting feature of the presently claimed invention is the precatalyst (1024) which is placed in

the bypass conduit (1025) downstream from the electronically controlled bypass valve (1023). The precatalyst (1024) is Diesel oxidation catalyst [DOC] or a Lean NOx Trap [LNT].
[0001] The electronically controlled bypass valve (1023) is a valve
that diverts exhaust gases away from the turbine (1021) of the turbocharger (102) towards the pre-catalyst (1024) and further into the exhaust gas pipe (1031) via the bypass conduit (1025). The opening and closing of the valve is controlled by the ECU. The bypass valve (1023) can be a specially designed ECU controlled valve in case of a Variable Geometry Turbocharger without an active waste gate. An active waste gate can also be used as the bypass valve (1023) for the said purpose if already present. However specially designed bypass valve (1023) is preferred as active waste gate is designed for bleeding the exhaust gases at high exhaust masses at high temperatures. This will expose the pre-catalyst (1024) to high exhaust temperature leading to thermal shock.
[0002] The main catalyst (103) in diesel engine is the Diesel
Oxidation catalyst [DOC] or a lean NOx Trap [LNT] and additionally vehicle may or may not have a Selective Catalytic Reduction (SCR) based DeNOx system. The pre-catalyst of the turbocharger (102) is independent of main catalyst and can be either Diesel oxidation catalyst [DOC] or a Lean NOx Trap (LNT) with suitable measures for the regeneration of

LNT. However in terms of volume the pre-catalyst has a much lesser volume than the main-catalyst.
[0003] The catalysts need to be at certain temperature called light
off temperature [generally 180° C and above] before they work effectively. Until this temperature is reached the DeNOx system will not function effectively. Hence the main catalyst (103) needs a minimum activation energy, which is supplied by exhaust gas heat. However, when the engine (101) is cold and at lower part loads, the turbocharger (102) doesn’t generate the boost pressure but instead acts as a heat sink reducing the temperature of exhaust gas and increasing the heating up time of main catalyst (103).
[0004] This heat energy of the exhaust gases during cold phase of
engine (101) is utilized by the present invention. During the cold phase the electronically controlled bypass valve (1023) is opened. This allows exhaust gases from exhaust manifold (1012) to bypass the turbocharger (102) and flow through small low exhaust temperature optimized precatalyst (1024) in the bypass conduit (1025). Pre-catalyst having lesser volume as compared to the main catalyst (103) heats up much faster and thus can be used to increase the exhaust temperature further by means of exothermic reactions. This in turn heats up the main catalyst (103) faster and allow for more effective conversion of emissions from cold engine.

[0005] During high load operations and warmed up condition the
electronically controlled bypass valve (1023) is closed. Therefore now the exhaust gases from the exhaust manifold (1012) flow towards the turbine (1021) of the turbocharger (102). The turbocharger (102) now performs its normal operation i.e. the exhaust gases drive the turbine (1021) of the turbocharger (102) which regulates the rotating speed of the compressor (1022), which ultimately gives the boost pressure back to the intake manifold (1011) of the engine. Since the pre-catalyst(1024) will be exposed to exhaust gas for a very lesser in duration and low temperature exhaust gas, it will be subjected to less thermal shock and have a better life and efficiency throughout the engine life.
[0006] This idea to develop a turbocharger (102) for an internal
combustion engine (101) allows a faster release of heat up measures and reduce the cold emission effectively. It efficiently utilizes the energy of the exhaust gases in the cold phase of the engine (101) for heating up the main catalyst, and reducing emissions in the cold phase.
[0007] It must be understood that the embodiments explained in the
above detailed description are only illustrative and do not limit the scope of this invention. Any modification to the turbocharger (102) for an internal combustion engine (101) are envisaged and form a part of this invention. The scope of this invention is limited only by the claims.

We Claim:
1. A turbocharger (102) for an internal combustion engine, the turbocharger (102) comprising a turbine (1021), and at least a bypass conduit (1025), the turbine (1021) in fluid communication with an exhaust manifold (1012) of the engine (101) at a first end and with an exhaust gas pipe (1031) at a second end, the bypass conduit (1025) permits flow of exhaust gases between the exhaust manifold (1012) of the engine (101) and the exhaust gas pipe (1031), an electronically controlled bypass valve (1023) is placed inside the bypass conduit (1025), characterized in that turbocharger (102) a precatalyst (1024) placed in the bypass conduit (1025) downstream from the electronically controlled bypass valve (1023).
2. The turbocharger (102) for an internal combustion engine (101) as claimed in claim 1, where the pre-catalyst is Diesel oxidation catalyst [DOC] or a Lean NOx Trap [LNT].