Engine Exhaust Gas Temperature Control with Variable Geometry Turbocharging
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Solution Overview
Problem
Current systems fail to effectively control exhaust gas temperature at the catalyst inlet in internal combustion engines, which affects catalyst performance and durability.
Innovation Solution
A vehicle engine system that includes an EGT sensor to measure exhaust gas temperature, a system controller to compare it with a target temperature, and adjusts gas exchange and turbine efficiency through variable geometry turbocharger boost to manage exhaust gas temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If gas exchange within the cylinder is limited during the intake stroke, then exhaust gas temperature is reduced, but engine power output decreases
Solution Approach 1:
The system dynamically adjusts the intake valve closure timing based on real-time exhaust gas temperature measurements. When EGT exceeds the threshold, the intake valve closes earlier than conventional timing, reducing the intake charge mass and thereby reducing exhaust gas temperature. This dynamic adjustment resolves the contradiction by adapting the gas exchange strategy to temperature conditions while maintaining power output within acceptable ranges.
Solution Approach 2:
The system changes the timing parameter of the intake valve closure event in response to high exhaust gas temperature conditions. By advancing the intake valve closure timing, the system reduces the volume of the air-fuel mixture entering the cylinder, which directly reduces the mass of exhaust gases produced and lowers exhaust gas temperature. This parameter change allows temperature control while managing the impact on engine power.
2Temperature
If turbine efficiency is increased by increasing boost from the turbocharger, then exhaust gas temperature is reduced, but system complexity increases
Solution Approach 1:
The system employs a variable geometry turbocharger with movable vanes that can dynamically adjust the turbine inlet angle based on operating conditions. When exhaust gas temperature is high, the vanes adjust to increase turbine efficiency and boost pressure, which cools the exhaust gases through increased enthalpy extraction. This dynamic geometry adjustment provides temperature control capability while integrating into the existing turbocharger system.
Solution Approach 2:
The system changes the geometric parameter of the turbine inlet by adjusting the angle of the movable vanes. This parameter change optimizes the exhaust gas flow through the turbine, increasing turbine efficiency and the amount of work extracted from the exhaust gases. The increased boost pressure resulting from this parameter change helps reduce exhaust gas temperature while utilizing an established turbocharger component.
3Temperature
If intake valve closure is advanced to limit gas exchange, then exhaust gas temperature is controlled, but volumetric efficiency decreases
Solution Approach 1:
The system dynamically adjusts the intake valve closure timing based on real-time exhaust gas temperature measurements and operating conditions. Under high EGT conditions, the intake valve closes earlier than conventional timing, which limits the intake charge mass and reduces exhaust gas temperature. The system controller continuously monitors EGT and adjusts valve timing accordingly, resolving the contradiction by adapting gas exchange strategy to temperature requirements while minimizing impact on volumetric efficiency during normal operation.
Solution Approach 2:
The system changes the timing parameter of the intake valve closure event in response to high exhaust gas temperature conditions. By advancing the intake valve closure timing, the system reduces the duration of the intake stroke and the volume of the air-fuel mixture entering the cylinder, which directly reduces the mass of exhaust gases produced. This parameter change enables temperature control while managing the trade-off with volumetric 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
Effectively controls exhaust gas temperature, maintaining catalyst performance and durability by limiting gas exchange and enhancing turbocharger efficiency.
Implementation Method 1
increasing turbine efficiency of a variable geometry turbocharger of the engine by increasing boost from the turbocharger
Implementation Method 2
adjusting, with the system controller, an angle of each one of a plurality of movable vanes around the turbine that are in communication with the system controller and are adapted to control the exhaust gas flow through the turbine of the variable geometry turbocharger
Implementation Method 3
adjusting, with a cam phaser in communication with the system controller, timing of an intake camshaft associated with the intake valve
Implementation Method 4
advancing, with the system controller, a closing of an intake valve for the cylinder during the intake stroke
Data Source
AI summary
A vehicle engine adapted to control exhaust gas temperature (EGT) at a catalyst inlet includes an EGT sensor in communication with a system controller and adapted to measure a temperature of exhaust gas at the catalyst inlet, the system controller adapted to compare the measured EGT to a target EGT, and, when the measured EGT is greater than the target EGT, limit gas exchange within a cylinder within the engine during an intake stroke, and increase turbine efficiency of a variable geometry turbocharger of the engine by increasing boost from the variable geometry turbocharger.