Engine Braking Control Throttle for Overboost Reduction
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Solution Overview
Problem
Existing engine braking systems, particularly those using compression release brakes, face challenges in controlling the quantity of compressed air delivered to the cylinder during engine braking events, leading to overboost and undue stress on engine components due to insufficient reduction in exhaust gas energy at high engine speeds.
Innovation Solution
A system with a control throttle positioned upstream of the cylinder or turbine, adjustable by an engine control unit, to restrict the quantity of compressed air or divert exhaust gas into an auxiliary line, bypassing the turbine, thereby controlling the air and exhaust gas flow during engine braking events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the turbine vane position is changed to reduce exhaust gas energy, then the compressor power is reduced, but at high engine speeds the turbine still generates sufficient power causing overboost
Solution Approach 1:
The exhaust flow path is segmented into two separate paths: one through the turbine for normal operation, and another through the auxiliary exhaust line for bypassing the turbine during engine braking. This segmentation allows independent control of turbine power generation versus exhaust gas disposal, enabling precise control of compressed air quantity without overboost.
Solution Approach 2:
The control throttle positioned upstream of the auxiliary exhaust line acts as an intermediary device to regulate the diversion of exhaust gas from the turbine path to the auxiliary exhaust path. By controlling the throttle position, the system mediates between the need for turbine power generation and the need to limit compressed air quantity during engine braking, preventing overboost conditions.
2Quantity of substance
If exhaust gas is diverted into an auxiliary line bypassing the turbine, then compressed air quantity is controlled, but the system complexity increases
Solution Approach 1:
The auxiliary exhaust line and control throttle assembly serve multiple functions: they control the quantity of compressed air during engine braking, provides a bypass path for exhaust gas, and work in conjunction with existing turbine and compressor systems. This multi-functionality reduces the need for separate dedicated control mechanisms, thereby limiting the increase in system complexity.
3Stress or pressure
If a control throttle is positioned upstream of the cylinder to restrict compressed air, then overboost is reduced, but the device complexity increases
Solution Approach 1:
The control throttle for restricting compressed air during engine braking is merged with the existing throttle assembly structure. The control throttle shares the same housing and mounting infrastructure as other throttle components in the system, and is integrated into the existing electronic control architecture. This merging approach minimizes the increase in device complexity while achieving overboost reduction.
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 solution effectively regulates the quantity of compressed air entering the cylinder, reducing overboost and stress on engine components, ensuring optimal engine braking performance and component longevity.
Implementation Method 1
The control throttle is configured to adjustably restrict a quantity of compressed air that may enter into the cylinder during the intake stroke of the piston
Implementation Method 2
The control throttle is configured to adjustably divert at least a portion of the exhaust gas from the engine braking event into at least a portion of the auxiliary exhaust line. The auxiliary exhaust line is configured to allow the diverted exhaust gas flowing through the auxiliary exhaust line to bypass the turbine
Implementation Method 3
compressor(s) to increase the pressure, and thus mass, of air that is supplied to the cylinder during an intake stroke
Implementation Method 4
a turbine(s) often uses exhaust gas to generate power that is used by compressor(s) to increase the pressure, and thus mass, of air that is supplied to the cylinder during an intake stroke
Implementation Method 5
as such displacement of the pistons includes the pistons undergoing a compression stroke, air within the cylinder continues to be is compressed as the pistons are displaced toward a top dead center position in the cylinder. With compression release braking, the pressure of such compressed air in the cylinder provides a force that generally opposes this displacement of the piston
Data Source
AI summary
A system and method for controlling the quantity of compressed air that may enter into an engine cylinder during the intake stroke of a piston during an engine braking event. A control throttle may be positioned to restrict the quantity of compressed air that may enter into the cylinder during the intake stroke. The control throttle may also be positioned downstream of the engine and configured to adjustably restrict the quantity of exhaust gas that may be delivered to a turbine. By restricting the exhaust gas delivered to the turbine, the power generated by the turbine that is used by the compressor to compress intake air may also be reduced. Moreover, by controlling the power available to the compressor, the quantity of compressed intake air may be controlled, which allows for control of the quantity of compressed air that enters into the cylinder during the compression stroke.