Humidity Sensor Diagnostics via Exhaust Heat Recirculation
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Solution Overview
Problem
Existing methods for diagnosing the integrity of relative humidity sensors in engine systems, such as using an intake air heater, are inefficient and can adversely affect engine performance by warming charge air and consuming battery energy, leading to inaccurate humidity readings that can cause unstable engine operation and increased emissions.
Innovation Solution
A heat recirculation system that utilizes heat from the exhaust system, including a heat exchanger and a phase change material heat sink, to rapidly heat intake air and assess the status of the relative humidity sensor over a large temperature differential, thereby providing a robust and energy-efficient method for detecting sensor degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an electric heater is used to heat intake air for humidity sensor diagnostics, then the temperature differential for sensor assessment is improved, but energy consumption from the battery increases and charge air temperature may be adversely affected
Solution Approach 1:
The invention converts the harmful waste heat from the exhaust system into a beneficial heating source for intake air diagnostics. The exhaust heat, which would otherwise be discarded, is captured and used to heat the intake air for humidity sensor assessment, eliminating the need for battery-powered electric heaters and reducing energy consumption.
Solution Approach 2:
The exhaust system serves a dual function: its primary function for power generation and its secondary function as a heat source for diagnostics. The system uses itself (exhaust heat) to provide the heating capability needed for sensor diagnostics, making the system self-sufficient and eliminating external energy requirements.
2Temperature
If an electric heater is used to heat intake air for humidity sensor diagnostics, then the temperature differential for sensor assessment is improved, but charge air temperature may be adversely affected
Solution Approach 1:
The invention converts the harmful waste heat from the exhaust system into a beneficial heating source for intake air diagnostics. The exhaust heat, which would otherwise be discarded, is captured and used to heat the intake air for humidity sensor assessment, eliminating the need for battery-powered electric heaters and reducing energy consumption.
Solution Approach 2:
The invention introduces a heat exchanger as an intermediary device that transfers heat from the exhaust system to the intake air. This intermediary enables thermal energy transfer between two fluid streams without direct mixing, allowing diagnostics heating while maintaining separate thermal zones to prevent adverse effects on charge air temperature.
3Reliability
If the heater is operated for a prolonged period to cool down, then the humidity sensor assessment is robust, but the charge air temperature is adversely affected and engine performance is reduced
Solution Approach 1:
The invention uses periodic heating action through the exhaust heat recirculation system, activating heat transfer only during specific diagnostic phases rather than continuous operation. This periodic approach provides sufficient temperature differential for reliable sensor assessment while limiting total heating duration to prevent adverse effects on engine performance and charge air temperature.
4Loss of energy
If waste heat from the exhaust system is recirculated to heat intake air, then energy efficiency is improved and battery consumption is reduced, but the system complexity increases
Solution Approach 1:
The invention makes the exhaust system multi-functional by adding a heat recirculation capability that allows waste heat to be reused for intake air heating during diagnostics. This universal approach enables the same exhaust system to serve both its primary power generation function and a secondary diagnostic heating function, maximizing energy utilization without requiring entirely separate systems.
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 allows for rapid and accurate assessment of the relative humidity sensor's condition, reducing the impact of environmental noise and enabling timely adjustments to maintain stable engine operation while minimizing energy consumption and adverse effects on charge air temperature.
Implementation Method 1
the heat sink includes a phase change material configured to store large quantities of heat upon transition from a first state to a second state. The heat is released during a reverse transition from the second state to the first state
Implementation Method 2
Heat from the exhaust system may be absorbed by the heat sink and circulated to the heat exchanger by a coolant
Implementation Method 3
At the heat exchanger, the heat is transferred to the intake air via liquid-to-air heating
Data Source
AI summary
Methods and systems are provided for diagnosing a humidity sensor in an engine. In one example, a method may include heating intake air entering an intake passage of an engine using heat recirculated from an exhaust system of the engine. A response of the humidity sensor to the heating of the intake air may be used to assess an integrity of the humidity sensor.