Diesel Engine Brake Control via Turbocharger Speed Feedback
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Solution Overview
Problem
The calibration of variable geometry turbine (VGT) and throttling valve control in engine brake systems for supercharged Diesel engines is complex, leading to delayed engine brake response due to the need to balance back pressure and turbocharger rotation speed, which affects braking power and efficiency.
Innovation Solution
Implementing a closed-loop control system that dynamically adjusts the VGT based on the difference between target and current back pressure, and controls the throttling valve inversely proportional to the turbocharger rotation speed error, allowing for quicker engine brake activation and eliminating the need for separate calibration of VGT and flap operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the VGT and throttling valve positions are predetermined in lookup tables based on braking torque request, then the engine brake function can be activated, but the response is delayed due to conservative calibration needed to prevent turbocharger over-speed
Solution Approach 1:
The patent implements a feedback control system where the actual turbocharger rotation speed is continuously monitored and compared against a maximum allowed speed. The throttling valve position is dynamically adjusted based on this feedback to prevent over-speeding while allowing more aggressive VGT positioning for faster brake response. This resolves the contradiction by replacing conservative predetermined tables with an adaptive system that responds to real-time conditions.
Solution Approach 2:
The system transitions from static predetermined lookup tables to dynamic control where the throttling valve position is continuously adjusted based on actual turbocharger speed feedback. This dynamic adaptation allows the system to operate at the boundary of safety limits rather than conservatively within them, achieving faster response while maintaining reliability.
2Reliability
If the throttling valve is used to limit the enthalpy of gas flow and prevent turbocharger over-speed, then component integrity is preserved, but the engine brake response is delayed due to complex calibration requirements
Solution Approach 1:
The patent uses feedback from actual turbocharger speed measurements to dynamically control the throttling valve position, replacing complex predetermined calibration tables. The control unit continuously adjusts the valve to maintain speed within limits, simplifying the control strategy while preserving component integrity through adaptive rather than conservative predetermined settings.
Solution Approach 2:
The control system automatically adjusts the throttling valve position based on real-time speed feedback without requiring external calibration input. The system self-regulates to prevent over-speeding, eliminating the need for complex manual calibration processes while maintaining component safety.
3Power
If the VGT position is optimized for required braking power, then braking torque is sufficient, but the turbocharger rotation speed may exceed limit values
Solution Approach 1:
The patent separates the control functions of the VGT and throttling valve. The VGT is positioned aggressively to maximize braking torque generation, while the throttling valve is independently controlled based on speed feedback to limit turbocharger rotation. This segmentation allows each component to be optimized for its primary function without compromising the other.
Solution Approach 2:
The throttling valve acts as an intermediary element that mediates between the power-generating VGT and the speed-limited turbocharger. By positioning the valve based on speed feedback, it allows the VGT to operate at optimal braking positions while preventing the turbocharger from exceeding safe rotation speeds.
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 results in faster engine brake response, improved stability, and reduced sensitivity to operating conditions, allowing for precise control of braking torque without risking turbocharger over-speed, thus enhancing braking power and efficiency.
Implementation Method 1
Supercharged engines can exploit the presence of the turbocharger to further increase the braking torque generated by the engine under engine brake conditions
Implementation Method 2
the braking power of the engine brake depends both on the back pressure at the exhaust manifold and on the boost pressure at the intake manifold
Implementation Method 3
The moving blades of the variable turbine geometry affect the mass of gas driving the turbine wheel, which, in turn, increases or decreases the boost pressure at the intake manifold
Implementation Method 4
The regulation of the back pressure at the exhaust manifold is carried out by means of a throttling valve located on the exhaust manifold, generally upstream of the turbine
Implementation Method 5
the profile of the cams that control the opening of the exhaust valves is varied to release the compressed air in the exhaust manifold before it can return the previously accumulated compression energy
Data Source
Figure 1
Figure 2a~2c
Figure 2d~2f
AI summary
Method of managing an engine brake procedure in a diesel cycle engine (E), comprising a first process (CTRL1) arranged to control the variable geometry of the turbocharger to achieve a predetermined value of back pressure at the exhaust manifold and a second process (CTRL2) to control the throttling valve according to a function inversely proportional to an error given by the difference between the current speed value and the limit speed value of the turbocharger, according to a closed loop control.