Variable Geometry Turbocharger Boost Lag Reduction
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Solution Overview
Problem
Turbochargers in vehicles experience boost lag during transient engine conditions, leading to increased emissions and inefficient fuel injection, particularly due to the lag between load changes and the provision of pressurized boost air.
Innovation Solution
A variable geometry turbocharger system with a controller that adjusts the position of vanes in response to the accelerator pedal position, conserving boost pressure during tip-out conditions to minimize lag and emissions during subsequent tip-in events by partially closing the vanes and using a wastegate to manage compressor surge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the turbocharger operates under conventional control during transient conditions, then the boost pressure responds to load changes, but there is a lag time between load change and provision of pressurized boost air
Solution Approach 1:
The controller predicts future boost pressure requirements based on current accelerator pedal position and recent transient conditions. By preparing the turbocharger system in advance (pre-heating exhaust gases, positioning vanes appropriately), the system reduces the lag time when the driver demands acceleration, as the turbocharger is already partially primed to deliver boost pressure quickly.
Solution Approach 2:
The system dynamically adjusts turbocharger vanes and wastegate positioning based on real-time monitoring of accelerator pedal movements and engine load conditions. This dynamic control allows the system to optimize boost pressure delivery continuously, responding faster to transient conditions by adapting vane angles and exhaust flow paths according to the predicted acceleration demand.
2Loss of time
If boost pressure is increased during transient conditions to reduce lag, then response time improves, but emissions increase due to deviation from steady-state optimized set-point
Solution Approach 1:
The controller continuously monitors boost pressure, exhaust gas temperature, and accelerator pedal position to predict when transient conditions will occur. This feedback mechanism allows the system to adjust turbocharger vanes and wastegate positioning proactively, maintaining optimal air-fuel ratios and boost pressure trajectories that minimize emissions while still reducing lag time during transient acceleration events.
Solution Approach 2:
The system changes operating parameters (vane angles, wastegate opening, exhaust flow rates) dynamically based on predicted transient conditions. By optimizing these parameters in advance and during the transient event, the system maintains combustion efficiency and minimizes emissions spikes that would otherwise occur during rapid acceleration, while still achieving faster boost pressure response.
3Use of energy by moving object
If the accelerator pedal is released (tip-out) following acceleration (tip-in), then fuel injection rate decreases, but boost pressure should be reduced which increases lag for subsequent acceleration
Solution Approach 1:
When the controller detects a tip-out condition following acceleration, it predicts that the driver may demand acceleration again soon. The system maintains higher boost pressure and keeps exhaust gases hot by adjusting vanes and wastegate positioning, rather than allowing boost pressure to drop completely. This preliminary maintenance of system readiness reduces the lag time when the next acceleration demand occurs, while still allowing fuel injection to decrease during the coasting period.
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 reduces emissions and turbo lag by maintaining optimal boost pressure during transient conditions, ensuring efficient fuel injection and improved engine performance.
Implementation Method 1
a variable geometry turbocharger comprising a plurality of vanes adjacent a turbine inlet
Implementation Method 2
provide pressurized air boosts (boost pressure) to an engine
Implementation Method 3
variable geometry turbocharger comprising a plurality of vanes adjacent a turbine inlet
Data Source
AI summary
Methods and systems are provided for a turbocharger. A system comprises a variable geometry turbocharger comprising a plurality of vanes, wherein the plurality of vanes is operated during a low-load transient event to conserve boost pressure from a previous high-load transient event to reduce lag during a proceeding high-load transient event.