EGR Turbocharger Segmentation for Low-Speed Torque
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Solution Overview
Problem
Existing supercharged internal combustion engines face challenges in maintaining torque characteristics at low engine speeds and small exhaust-gas flow rates, particularly due to the inefficiency of exhaust-gas turbochargers in generating high charge pressures, and the need for large coolers to achieve high exhaust-gas recirculation rates, which complicates packaging.
Innovation Solution
The implementation of an exhaust-gas recirculation system with a second turbocharger and cooler, where exhaust gas is compressed before cooling, allowing for high recirculation rates and efficient energy utilization, and the use of an electric auxiliary drive to support the compressor power, enabling dense packaging and improved engine performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional exhaust-gas turbocharger is used to supercharge the engine, then the engine power is increased, but the torque characteristic at low engine speeds deteriorates due to insufficient charge pressure generation
Solution Approach 1:
The exhaust-gas recirculation system is segmented into two functional parts: a first turbocharger for supercharging the engine, and a second turbocharger specifically for compressing exhaust gas for recirculation. This segmentation allows each turbocharger to be optimized for its specific function, with the second turbocharger ensuring adequate charge pressure even at low engine speeds to maintain torque characteristics.
Solution Approach 2:
The second turbocharger serves a dual purpose: it compresses exhaust gas for recirculation to reduce nitrogen oxide emissions, and simultaneously provides the necessary charge pressure to maintain torque characteristics at low engine speeds. This multi-functionality addresses both environmental and performance requirements.
2Object-generated harmful factors
If a large cooler is used to achieve high exhaust-gas recirculation rates, then nitrogen oxide emissions are reduced, but the packaging space requirement increases
Solution Approach 1:
The exhaust gas is compressed by the second turbocharger before entering the cooler. This preliminary compression increases the density of the exhaust gas, allowing for more effective cooling and higher recirculation rates in a compact cooler design, thereby reducing the required packaging space.
Solution Approach 2:
The system changes the pressure parameter of the exhaust gas by using the second turbocharger to compress it before cooling. This parameter change allows the cooler to achieve higher recirculation rates in a smaller volume, as the compressed gas has higher density and can be cooled more efficiently.
3Object-generated harmful factors
If the exhaust-gas recirculation system is designed for high recirculation rates, then emissions are reduced, but the system complexity increases due to additional components
Solution Approach 1:
The second turbocharger and cooler are integrated into a compact assembly that functions as a unified exhaust-gas recirculation unit. This merging of components achieves high recirculation rates while minimizing the space required and reducing overall system complexity compared to separate, distributed components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables high exhaust-gas recirculation rates, reduces nitrogen oxide emissions, and improves torque characteristics at low engine speeds by providing a compact and efficient exhaust-gas recirculation system that maintains engine efficiency and reduces packaging constraints.
Implementation Method 1
An EGR cooler is provided between the EGR turbine and the EGR compressor
Implementation Method 2
exhaust gas is compressed before cooling
Implementation Method 3
downstream of the cooler, there is arranged a turbine in which the cooled exhaust gas can expand
Implementation Method 4
The hot exhaust-gas flow is supplied to the turbine and expands in the turbine with a release of energy, as a result of which the shaft is set in rotation. The energy supplied by the exhaust-gas flow to the turbine and ultimately to the shaft is used for driving the compressor
Data Source
AI summary
Embodiments of an internal combustion engine are provided. In one example, an engine includes at least one cylinder, an intake system for supplying charge air to the at least one cylinder, an exhaust-gas discharge system for discharging exhaust gas from the at least one cylinder, a first exhaust-gas turbocharger including a first turbine arranged in the exhaust-gas discharge system and a first compressor arranged in the intake system; and an exhaust-gas recirculation (EGR) system. The EGR system includes a line which branches off from the exhaust-gas discharge system and opens into the intake system, a second exhaust-gas turbocharger comprising an EGR turbine arranged in the line on a shaft and an EGR compressor arranged in the line on the shaft upstream of said EGR turbine, and an EGR cooler positioned between the EGR turbine and the EGR compressor.