Variable Geometry Turbocharger Intake Valve Timing for Otto Engine Efficiency
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Solution Overview
Problem
Otto engines are limited in thermodynamic efficiency due to necessary throttling and reduced compression ratio to avoid engine knocking, leading to a significant loss of performance when using the Miller or Atkinson methods.
Innovation Solution
A method for operating a high-compression Otto engine with an exhaust gas turbocharger featuring variable turbine geometry, where the intake valve is closed early to increase compression ratio without knocking, and an electrically driven compressor is used to compensate for charge losses, allowing for a broader compressor map and reduced process temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the Miller or Atkinson method is used to increase compression ratio and improve thermodynamic efficiency, then fuel efficiency is improved, but engine power is significantly reduced
Solution Approach 1:
The patent applies variable valve timing to dynamically adjust the intake valve closing point. By controlling when the intake valve closes during the intake stroke, the system can achieve Miller/Atkinson cycle benefits (reduced compression work, improved efficiency) while maintaining adequate air charging through dynamic adjustment, thereby preserving engine power across different operating conditions
Solution Approach 2:
The patent changes the timing parameter of intake valve closing to occur before bottom dead center during the intake stroke. This parameter change reduces the effective compression ratio and compression work, improving thermodynamic efficiency while the variable valve timing system compensates to maintain power output
2Use of energy by moving object
If the intake valve is closed early in the Miller method to increase compression ratio, then thermodynamic efficiency is improved, but charge losses increase
Solution Approach 1:
The patent uses variable valve timing to dynamically control the intake valve closing event. By adjusting the closing timing based on operating conditions, the system optimizes the balance between reducing compression work (for efficiency) and maintaining adequate charge air delivery, thereby minimizing charge losses while achieving efficiency gains
3Use of energy by moving object
If a high geometric compression ratio is used to improve efficiency, then thermodynamic efficiency is improved, but engine knocking increases
Solution Approach 1:
The patent employs variable valve timing to dynamically adjust the intake valve closing point, effectively controlling the compression process. By closing the intake valve before bottom dead center, the system reduces the effective compression ratio and compression end temperature, preventing knocking while maintaining the geometric compression ratio for improved efficiency
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 achieves a performance-neutral increase in efficiency by reducing compression work, lowering exhaust gas temperatures, and minimizing material costs, while maintaining engine power, thus enhancing overall thermodynamic efficiency and reducing emissions.
Implementation Method 1
combustion air, which is supplied to a cylinder of the Otto engine through an intake valve, is compressed using an exhaust gas turbocharger with a turbine that has a variable turbine geometry
Implementation Method 2
the exhaust gases supplied to the turbine are cooled in a part of the exhaust gas line, in particular between an outlet valve of the Otto engine and the turbine of the exhaust gas turbocharger. The exhaust gases are preferably cooled in an exhaust manifold.
Implementation Method 3
The variable turbine geometry of the exhaust gas turbocharger is set as a function of a load on the Otto engine
Data Source
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AI summary
The present invention relates to a method for operating a drive assembly having a gasoline engine (1) and an exhaust gas cooling system. According to the method, combustion air fed through an inlet valve to a cylinder (3) of the gasoline engine (1) is compressed by an exhaust turbocharger (12) having a turbine (13) with variable turbine geometry. The inlet valve is closed before a piston in the cylinder (3) reaches bottom dead center. The exhaust gas fed to the turbine is cooled in a section of an exhaust gas line, in particular in the exhaust manifold.