U.S. patent application number 10/106093 was filed with the patent office on 2003-10-02 for engine turbocompressor controllable bypass system and method.
Invention is credited to Corba, David, Gottemoller, Paul, Poola, Ramesh B., Zagone, John R..
Application Number | 20030183212 10/106093 |
Document ID | / |
Family ID | 27804343 |
Filed Date | 2003-10-02 |
United States Patent
Application |
20030183212 |
Kind Code |
A1 |
Gottemoller, Paul ; et
al. |
October 2, 2003 |
Engine turbocompressor controllable bypass system and method
Abstract
A system for a turbocharged internal combustion engine includes
an engine having a charge inlet connected to the compressor outlet
and an exhaust outlet connected to the turbine inlet for driving
the turbocharger with hot exhaust gas and supplying compressed air
to the engine for combustion. A bypass duct connects the compressor
outlet to the turbine inlet for diverting a portion of the
compressed air around the engine to the turbine inlet. A control
member selectively controls the diversion of air. An operating
method for the system involves controlling surge in an engine
turbocharger compressor by diverting a portion of compressed air to
the turbine inlet to limit compressor air pressure and insure
sufficient air flow to avoid compressor surge. Preferably, the
diverted air enters a distal part of an engine exhaust header for
mixing with the exhaust gases prior to passing into the turbine
inlet. Other benefits are disclosed.
Inventors: |
Gottemoller, Paul; (Palos
Park, IL) ; Poola, Ramesh B.; (Naperville, IL)
; Corba, David; (Des Plaines, IL) ; Zagone, John
R.; (Westmont, IL) |
Correspondence
Address: |
CARY W. BROOKS
General Motors Corporation
Legal Staff, Mail Code 482-C23-B21
P.O. Box 300
Detroit
MI
48265-3000
US
|
Family ID: |
27804343 |
Appl. No.: |
10/106093 |
Filed: |
March 26, 2002 |
Current U.S.
Class: |
123/563 |
Current CPC
Class: |
F02B 37/16 20130101;
F02B 37/20 20130101; Y02T 10/12 20130101; Y02T 10/144 20130101 |
Class at
Publication: |
123/563 |
International
Class: |
F02B 033/00 |
Claims
1. A controllable bypass system for a turbocharged internal
combustion engine, the system comprising: an engine having a charge
inlet and an exhaust outlet; a turbocharger including a turbine
driving a compressor, a turbine inlet connected to the engine
exhaust outlet for driving the turbine with hot exhaust gas and a
compressor outlet connected to the engine charge inlet for
supplying compressed air to the engine for combustion; a bypass
duct connecting the compressor outlet to the turbine inlet for
diverting a portion of the compressed air around the engine from
the compressor outlet to the turbine inlet; and a control member
for selectively controlling the diversion of air through the bypass
duct.
2. A system as in claim 1 wherein the control member is a control
valve in the duct and is externally operable for controlling bypass
air flow.
3. A system as in claim 2 wherein the control valve is operated by
a controller responsive to air flow and pressure differential
across the compressor to provide bypass air flow as required to
avoid surge in the compressor air flow.
4. A system as in claim 1 including a charge air cooler in the
engine charge inlet for cooling the compressed air prior to
combustion in the engine.
5. A system as in claim 1 wherein the engine includes an exhaust
manifold forming part of the engine exhaust outlet and the bypass
duct is connected to the exhaust manifold at an end distal from the
turbine inlet
6. A method of controlling surge in an engine turbocharger
compressor, the method comprising: diverting a sufficient portion
of the compressed air from the compressor outlet around the engine
to the turbine inlet to limit compressor air pressure and insure
sufficient air flow to avoid compressor surge conditions while
utilizing the energy in the diverted air to maintain compressor
speed.
7. A method as in claim 6 including passing the diverted air
through an engine exhaust header for mixing with the exhaust gases
prior to passing into the turbine inlet.
8. A method of controlling NOx production in an engine having a
turbocharger, the method comprising: diverting a controlled portion
of compressed air from the compressor outlet around the engine to
the turbine inlet to limit oxygen content in the cylinders and
thereby reduce NOx production in the cylinders while utilizing the
energy in the diverted air to maintain compressor speed.
9. A method as in claim 8 including passing the diverted air
through an engine exhaust header for mixing with the exhaust gases
prior to passing into the turbine inlet.
10. A method of controlling peak cylinder pressure in an engine
having a turbocharger, the method comprising: diverting a portion
of the compressed air from the compressor outlet around the engine
to the turbine inlet to limit oxygen content in the cylinders and
reduce the combustion rate, thereby limiting peak pressures in the
engine cylinders while utilizing the energy in the diverted air to
maintain compressor speed.
11. A method as in claim 10 including passing the diverted air
through an engine exhaust header for mixing with the exhaust gases
prior to passing into the turbine inlet.
Description
TECHNICAL FIELD
[0001] This invention relates to turbocharged internal combustion
engines, such as diesel engines, and more particularly to a system
and method for controlling compressor surge in the turbocharger and
providing certain operational and performance advantages.
BACKGROUND OF THE INVENTION
[0002] It is known in the art to utilize a wastegate in connection
with a turbocharger compressor to bypass some of the compressor
outlet air directly to the exhaust outlet of the turbocharger. The
wastegate is opened when necessary to avoid compressor surge by
increasing air flow through the compressor while reducing the
pressure differential across the compressor. The bypass action of
the wastegate also reduces air flow through the engine and
therefore the cylinder charge. This has the effect of reducing peak
combustion pressures and temperature resulting in reduced emissions
of nitrogen oxides (NOx). The thermal load on the charge air
cooler, or aftercooler, is also reduced by reducing the engine air
flow by means of the wastegate. However, the bypassed air is not
utilized and thus creates an energy loss in the system.
[0003] There are turbocharged diesel engine operating conditions
which produce a higher cylinder trapped oxygen content than is
required for efficient combustion. Typically, this results in
higher NOx production because of the resulting higher peak pressure
in the cylinders and increased oxygen available to combine with
free nitrogen. A system and method for controlling compressor surge
and further lowering controlled engine exhaust emissions is
desired.
SUMMARY OF THE INVENTION
[0004] The present invention involves taking a portion of the
compressor discharge air and bypassing the charge air cooler and
engine cylinders and re-injecting the compressed air prior to the
turbine inlet. The bypassed air is preferably directed through the
engine exhaust header or manifold, if provided. The bypass duct
around the charge cooler and engine is provided with a control
valve to limit air flow through the bypass to a desired value. The
valve may be operated by suitable controls responsive, for example,
to turbocharger compressor air flow and/or differential pressure
and rotor speed to determine the proper setting of the bypass
control valve.
[0005] The novel bypass system may be utilized under various engine
operating conditions to prevent surge of the turbocharger
compressor by increasing air flow and/or reducing differential
pressure. Where the engine air charge pressure is greater than
needed, the opening of the surge control bypass will result in
reduced cylinder pressure as well as reduced cylinder oxygen
content, both of which will result in the production of lower NOx
emissions. The bypass of compressor air directly into the engine
exhaust manifold will reduce manifold exhaust temperature and lower
the NOx produced in the exhaust. It will also improve turbine life
by reducing maximum turbine temperatures. The system additionally
recovers a large percentage of the compressor discharge energy by
passing the compressed air through the turbine. Further, the
bypassed air provides additional oxygen to the exhaust which helps
burn up any excess hydrocarbons. Additionally, the reduced air flow
through the engine also reduces the cooling load on the
aftercooler, providing for more efficient system operation.
[0006] These and other features and advantages of the invention
will be more fully understood from the following description of
certain specific embodiments of the invention taken together with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The single FIGURE of the drawing is a schematic side view of
an engine including a turbocharger and a system for controlling
compressor surge in accordance with the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0008] Referring now to the drawing in detail, numeral 10 generally
indicates an internal combustion engine assembly, such as a diesel
engine for railroad locomotives, marine applications and other
uses. Assembly 10 includes an engine 12 having a charge air inlet
14 and an exhaust outlet including an engine exhaust manifold 16. A
turbocharger 18 is mounted on or adjacent to the engine and
includes internally a turbine 20 driving a compressor 22.
[0009] The compressor includes an ambient air inlet 24 and a
compressed air outlet 26. The turbine includes an exhaust gas inlet
28 and an exhaust discharge or outlet 30.
[0010] The compressor outlet 26 is conventionally connected through
a duct 32 with an inlet header 34 for a charge air cooler 36. The
air cooler 36 discharges to a manifold or header 38 which delivers
cooled compressed inlet air to the engine cylinders, not shown. The
engine cylinders discharge through one or more exhaust outlets 40
to the exhaust manifold 16, which carries the engine exhaust gas to
the inlet 28 of the turbine for driving the turbocharger. The spent
exhaust gas is discharged through the turbine exhaust 30.
[0011] In accordance with the invention, the engine assembly 10
includes and forms a part of a surge control system 42 for
controlling surge in the turbocharger compressor as well as for
providing other benefits. In addition to the elements described
above, the surge control system 42 includes a bypass duct 44 which
connects the charge air cooler inlet header 34 directly with the
engine exhaust manifold 16 at an end 46 distal from the turbine
exhaust gas inlet 28. The bypass duct 44 has mounted therein a
bypass control valve 48 which may be operated in any suitable
manner, such as by an electronic or electro-mechanical control 50.
Control 50 may be actuated through suitable sensors, not shown, in
response to operational data such as pressure differential, air
flow and/or compressor speed. Operating conditions can be
programmed to maintain the compressor in a surge-free operational
condition.
[0012] In operation of the engine, especially at higher load
conditions, the turbocharger speed may provide greater air pressure
and flow than is needed in order to properly burn the fuel supplied
to the engine. Under some conditions, the exhaust back pressure may
increase excessively, limiting air flow through the compressor and
approaching a condition of surge. Under such circumstances, sensed
conditions within the turbocharger will actuate the control 50 to
open the bypass valve 48 a controlled amount. This will allow some
of the compressor discharge air to be bypassed around the charge
cooler 36 and engine cylinders, not shown, directly to the engine
exhaust manifold 16 at the end 46 distal from the turbine inlet 28.
Bypassing of the charge cooler and engine immediately increases
turbocharger airflow and reduces the differential pressure, so as
to avoid compressor surge. Air flow through the charge air cooler
and engine cylinders is also reduced so that the thermal load on
the charge cooler is lowered. Also, air trapped in the engine
cylinders is reduced so that oxides of nitrogen production in the
cylinders is lowered because of the reduced temperatures and excess
air present. At the same time, the air bypassed through the bypass
duct 44 passes through the exhaust manifold 16 where it mixes with
the engine exhaust gases, and its oxygen content assists in burning
up excess hydrocarbons in the exhaust. Additionally, the energy of
the bypassed compressor air adds to the exhaust energy upon
entering the turbine 20 of the turbocharger so that the energy is
used in maintaining the turbocharger speed prior to discharging to
atmosphere with the other exhaust gases through the turbine exhaust
discharge 30. The reduction in cylinder pressure in the engine
because of the lower exhaust charges also helps reduce NOx formed
during combustion in the cylinders.
[0013] Considered as a method, the present invention involves
controlling surge in an engine turbocharger compressor by diverting
a sufficient portion of the compressed air from the compressor
outlet around the engine to the turbine inlet to limit compressor
air pressure and insure sufficient airflow to avoid compressor air
surge conditions. The method may also include passing the diverted
air through the engine exhaust header or manifold for mixing with
the exhaust gases prior to passing into the turbine inlet. Excess
oxygen in the diverted air is then available for burning
hydrocarbons present in the engine exhaust manifold. The method may
also include operating the control valve in the bypass duct to
reduce engine cylinder pressures and temperatures. It can also
control air flow thorough the charge air cooler to obtain
reductions in engine created NOx and to lower the cooling load in
the charge air cooler where such operation may prove of benefit in
conserving energy or controlling emissions.
[0014] While the invention has been described by reference to
certain preferred embodiments, it should be understood that
numerous changes could be made within the spirit and scope of the
inventive concepts described. Accordingly, it is intended that the
invention not be limited to the disclosed embodiments, but that it
have the full scope permitted by the language of the following
claims.
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