General Motors has just been granted a patent by the United States Patent and Trademark office for a two stage turbo setup with variable geometry in an internal combustion engine.
A Common Language Overview
The patent details a two-stage turbocharger system that includes a High Pressure (HP) turbocharger and a Low Pressure (LP) turbocharger. The two turbo systems can be “configured to operate at low/medium engine speeds and to operated the LP turbocharger only at high engine speed”, in which case the HP turbocharger is bypassed.
The filing goes on to state that engine turbochargers “allow higher internal combustion engine performances” but that “they are not free from drawbacks, in particular when the internal combustion engine is operated at low speed and/or low load.” The two-stage turbo system would overcome the turbochargers’ downsides by providing high performance charging at low engine speeds, while at the same time contributing to high efficiency and lower fuel consumption.
As the patent brief puts it, the invention provides “an internal combustion engine with high performance charging systems, ensuring high efficiency even at low operational speed.”
The filing also provides a flowchart for the logic of the variable geometry’s system. The setup monitors at least one operating parameter of the internal combustion engine, and solicits whether at least one monitored value equal to or below at least one threshold value.
If the answer is yes, then the variable geometry low pressure turbine is bypassed by the bypass system. If no, then the variable geometry low pressure turbine is not bypassed by the bypass system.
GM’s research and development arm, officially known as GM Global Technology Operations, LLC, initially filed the patent application with the USPTO on December 14th, 2015. The application was granted three days ago, on August 21st, 2018.
The Very Geeky Details
We broke down the patent for those who truly would like to geek out on the details.
As it stands, the crux of the patent (what it claims) are the following nine elements:
1. An internal combustion engine having a two stage turbocharger, with the two stage turbocharger comprising:
- A first stage as having:
- A high pressure turbine fluidly connected to an exhaust manifold of the engine through a first stage turbine inlet duct and
- A high pressure compressor rotatably coupled to the high pressure turbine
- A second stage having:
- A variable geometry low pressure turbine fluidly connected to the high pressure turbine through a second stage turbine inlet duct
- A low pressure compressor rotatably coupled to the low pressure turbine
- A second stage turbine bypass system including a second stage turbine bypass duct for allowing exhaust gas to bypass the variable geometry low pressure turbine
- A second stage turbine bypass valve arranged in the second stage turbine bypass duct
- A second stage compressor bypass system including a second stage compressor bypass duct bypassing the low pressure compressor
- A second stage compressor bypass valve arranged in the second stage compressor bypass duct
- An electronic control unit configured to:
- Monitor a value of at least one operating parameter of the internal combustion engine from a sensor during an engine operation, wherein the at least one operating parameter is selected from the group consisting of an engine speed correlated parameter, an engine torque correlated parameter or a combination thereof
- Compare a value of the at least one operating parameter with a threshold value for the at least one operating parameter
- Control the second stage turbine bypass valve and the variable geometry low pressure turbine for allowing the exhaust gas to flow through the second stage turbine bypass duct when the value of the at least one operating parameter is less than or equal to the threshold value
- Control the second stage compressor bypass valve for allowing the intake fluid to flow through the second stage compressor bypass duct and to bypass the low pressure compressor when the exhaust as bypasses the variable geometry low pressure turbine.
2. The internal combustion engine according to claim 1, wherein the second stage turbine bypass duct branches from the second stage turbine inlet duct upstream of the variable geometry low pressure turbine.
3. The internal combustion engine according to claim 1, wherein the variable geometry low pressure turbine comprises a housing, and the variable geometry low pressure turbine bypass valve is a housing-integrated bypass valve.
4. The internal combustion engine according to claim 3, wherein the variable geometry low pressure turbine is provided with a rotor within the housing, and the housing comprises a first chamber upstream of the rotor and a second chamber downstream of the rotor, the first chamber being fluidly connectable to the second chamber by the housing-integrated bypass valve.
5. The internal combustion engine according to claim 4, wherein the first chamber houses a plurality of movable vanes.
6. A method of operating a two stage turbocharger of an internal combustion engine having:
- A first stage including a high pressure turbine fluidly connected to an exhaust manifold of the engine through a first stage inlet duct and
- A second stage including a variable geometry low pressure turbine fluidly connected to the high pressure turbine through:
- A second stage turbine inlet duct
- A low pressure compressor rotatably coupled to the low pressure turbine
- A second stale turbine bypass system including a second stale turbine bypass duct bypassing the variable geometry low pressure turbine, and
- A second stage turbine bypass valve located in the turbine bypass duct
- A second stage compressor bypass system including a second stage compressor bypass duct bypassing the low pressure compressor
- A second stage compressor bypass valve located in the second stage compressor bypass duct, the method comprising:
- Monitoring a value of at least one operating parameter of the internal combustion engine with a sensor during an engine operation, wherein the at least one operating parameter is selected from the group consisting of:
- An engine speed correlated parameter
- An engine torque correlated parameter
- Or a combination thereof
- Comparing a value of the at least one operating parameter with a threshold value for the at least one operating parameter in an electronic control unit
- Controlling the second stage turbine bypass valve and the variable geometry low pressure turbine with the electronic control unit for allowing the exhaust gas to flow through the second stage turbine bypass duct when the value of the at least one operating parameter is less than or equal to the threshold value, and
- Controlling the second stage compressor bypass valve with the electronic control unit for allowing the intake fluid to flow through the second stage compressor bypass duct and to bypass the low pressure compressor when the exhaust gas bypasses the variable geometry low pressure turbine.
- Monitoring a value of at least one operating parameter of the internal combustion engine with a sensor during an engine operation, wherein the at least one operating parameter is selected from the group consisting of:
7. The method according to claim 6, wherein said engine torque correlated parameter comprises a brake mean effective pressure.
8. The method according to claim 6, wherein said threshold value for the at least one operating parameter defines at least one of a low speed operating condition or a low load operating condition of the internal combustion engine in correspondence to, or below, said threshold value.
9. A computer program stored in a non-transitory computer-readable medium and executable an electronic control unit for operating a two stage turbocharger of an internal combustion engine having a first stage including a high pressure turbine fluidly connected to an exhaust manifold of the engine through:
- A first stage inlet duct and
- A second stage including a variable geometry low pressure turbine fluidly connected to the high pressure turbine through:
- A second stage turbine inlet duct
- A low pressure compressor rotatably coupled to the low pressure turbine
- AÂ second stage turbine bypass system including a second stage turbine bypass duct bypassing the variable geometry low pressure turbine
- AÂ second stage turbine bypass valve located in the turbine bypass duct
- A second stage compressor bypass system including a second stage compressor bypass duct bypassing the low pressure compressor
- A second stage compressor bypass valve located in the second stage compressor bypass duct
- A computer program comprising instructions which, when executed on the electronic control unit, are configured to:
- Monitor a value of at least one operating parameter of the internal combustion engine with a sensor during an engine operation, wherein the at least one operating parameter is selected from the group consisting of:
- An engine speed correlated parameter
- An engine torque correlated parameter
- Or a combination thereof
- Compare a value of the at least one operating parameter with a threshold value for the at least one operating parameter
- Control the second stage turbine bypass valve and the variable geometry low pressure turbine for allowing the exhaust gas to flow through the second stage turbine bypass duct when the value of the at least one operating parameter is less than or equal to the threshold value
- Control the second stage compressor bypass valve for allowing the intake fluid to flow through the second stage compressor bypass duct when the exhaust gas bypasses the variable geometry low pressure turbine.
- Monitor a value of at least one operating parameter of the internal combustion engine with a sensor during an engine operation, wherein the at least one operating parameter is selected from the group consisting of:
Peruse the entire 14-page-long patent brief in its entirety right here (in PDF format).
Comments
I wonder how this significantly differs from Borgwarner’s VGT
To add. I believe the Porsche 917 twins use the BW VGT.
I think in utmost layman’s terms, it’s like the CVT of turbos.
Looks like it’s not as compact as a VGT. wonder if it will fit in the valley of the 4.2.
Guess I should have said not as compact as other VGT’s.