Compression Release Brake Control via VTG and EGR
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Solution Overview
Problem
Existing engine brake control systems struggle to maintain maximum braking torque at high motor speeds and high altitudes due to hardware limitations, limiting the utilization of braking capacity.
Innovation Solution
A method for controlling a compression release brake mechanism in a combustion engine with a variable turbine geometry turbocharger, involving continuous monitoring and control of exhaust manifold gas pressure, turbine speed, and turbine expansion ratio, using an exhaust gas recirculation channel and back pressure valve to optimize braking torque while adhering to hardware constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a compression release brake mechanism with VTG turbocharger is used to maximize braking torque, then braking capability is improved, but hardware limitations at high motor speeds and high altitudes prevent maintaining maximum braking torque
Solution Approach 1:
The patent implements a closed-loop control system that continuously monitors exhaust manifold pressure and adjusts the EGR valve position accordingly. The control method determines a desired exhaust manifold gas pressure level based on measured engine speed and desired braking torque, then continuously monitors control parameters including cylinder pressure, exhaust manifold pressure, turbine speed and turbine expansion ratio. This feedback mechanism allows the system to maintain optimal braking torque despite varying operating conditions such as high motor speeds and high altitudes.
Solution Approach 2:
The patent utilizes variable turbine geometry (VTG) to dynamically change the flow area of the turbine, and employs an exhaust gas recirculation (EGR) valve to control the recirculation rate of exhaust gas. By adjusting these parameters - the VTG vane position and EGR valve opening - the system can optimize exhaust manifold pressure and maintain maximum braking torque across different operating conditions including high speeds and altitudes where hardware limitations would otherwise prevent sustained performance.
2Power
If exhaust manifold pressure is increased to improve braking capability, then braking torque is enhanced, but load on the turbocharger increases
Solution Approach 1:
The patent introduces the EGR valve as an intermediary component that recirculates exhaust gas back into the intake system. This intermediary mechanism allows the system to increase effective exhaust manifold pressure and improve braking capability without proportionally increasing the load on the turbocharger. The recirculated exhaust gas provides additional mass flow and pressure in a controlled manner, reducing the energy penalty compared to simply increasing turbocharger output.
Solution Approach 2:
The patent recovers and reuses exhaust gas by routing it through the EGR channel back to the air inlet system. Instead of discarding the exhaust gas energy, the system recovers it and utilizes it to enhance exhaust manifold pressure for improved braking performance. This recovery approach allows increased braking capability while minimizing additional load on the turbocharger, as the recirculated gas provides pressure without requiring additional turbocharger work.
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 optimizes engine brake performance by increasing inlet pressure, enhancing braking capability, and improving altitude performance while reducing the load on the turbocharger, thereby overcoming the limitations of existing systems.
Implementation Method 1
an exhaust gas recirculation (EGR) channel for recirculation of exhaust gas towards the air inlet system
Implementation Method 2
a back pressure valve (BPV) provided in an exhaust channel
Implementation Method 3
adjustment of the flow area of the intake of the turbine... Adjustment of the VTG has a direct effect on the pressure in the inlet and exhaust manifolds
Implementation Method 4
At the beginning of the compression stroke the exhaust valves are opened and high pressurized air from the exhaust manifold flows back into the cylinder which increases the initial pressure during compression
Data Source
AI summary
A method is disclosed for controlling a compression release brake mechanism in a combustion engine. The method comprises: determining a desired exhaust manifold gas pressure level; continuously monitoring a set of control parameters, including at least two of cylinder pressure, exhaust manifold pressure, turbine speed and turbine expansion ratio; controlling a brake pressure valve and a variable turbine geometry by said control parameters, to drive one of the control parameters to a set first maximum level; and, while maintaining the first of the set of control parameters at the set first maximum level, controlling an exhaust gas recirculation valve by said control parameters in a closed loop to allow exhaust gas to recirculate towards an air inlet system while driving a second of the set of control parameters to a set second maximum level.