Turbine NOx Sensor Sampling Chamber for Harsh Exhaust Flows
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Solution Overview
Problem
Exhaust gas sensors in internal combustion engines are susceptible to damage from high temperatures, pressures, and velocities, particularly when exposed to pulsatile exhaust gases, leading to inaccurate readings and reduced lifespan, and the injection of reducing agents like DEF can further compromise sensor performance.
Innovation Solution
An exhaust gas conduit with a separate chamber that modifies the velocity and pressure of an aliquot of exhaust gases, allowing sensors to be positioned further upstream and protected from harsh conditions, while preventing reducing agents from affecting readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If exhaust gas sensors are positioned in the main exhaust flow to enable early measurement, then measurement timing is improved, but sensor reliability deteriorates due to exposure to high temperatures, pressures, and velocities
Solution Approach 1:
The exhaust gas flow is segmented into a main flow path and a separate sampling chamber. The sensor is positioned in the sampling chamber which receives exhaust gas through a sampling port, isolating the sensor from the harsh main exhaust flow conditions while enabling early measurement of exhaust gas composition
Solution Approach 2:
A sampling chamber acts as an intermediary between the main exhaust flow and the sensor. This intermediate structure modifies the exhaust gas parameters (temperature, pressure, velocity) before they reach the sensor, protecting the sensor while still allowing it to measure exhaust gas composition accurately
2Measurement precision
If sensors are positioned further upstream to prevent interference from reducing agents, then measurement accuracy is improved, but sensor exposure to harsh conditions increases
Solution Approach 1:
The exhaust system is segmented into zones: the upstream region where reducing agents are injected into the main flow, and the separate sampling chamber that draws exhaust gas from a position upstream of the reducing agent injection point. This segmentation allows accurate measurement without exposure to reducing agents
Solution Approach 2:
The sampling chamber serves as an intermediary structure that enables the sensor to measure exhaust gas composition upstream of the reducing agent injection point without being directly exposed to harsh conditions. The chamber geometry and sampling port design control the exhaust gas parameters reaching the sensor
3Reliability
If a separate sampling chamber is introduced to protect sensors, then sensor reliability is improved, but device complexity increases
Solution Approach 1:
The sampling chamber is merged with the exhaust gas conduit structure, integrating the sensor housing and sampling function into the existing exhaust system architecture. This reduces overall device complexity compared to adding a completely separate sampling system
Solution Approach 2:
The sampling chamber serves multiple functions: it houses the sensor, controls exhaust gas flow parameters, prevents exposure to reducing agents, and enables early measurement. This multi-functionality reduces the need for additional separate components, managing device complexity
Data Source
AI summary
There is a provided an exhaust gas conduit for an exhaust system of an internal combustion engine. The exhaust gas conduit includes a main passage for a main flow of exhaust gases passing through the exhaust gas conduit, a chamber configured to receive an aliquot of exhaust gases separated from the main flow of exhaust gases. A mounting point is provided in the chamber for mounting an exhaust gas sensor. The chamber being configured to modify the velocity and/or the pressure of exhaust gases passing therethrough.