Turbocharger Variable Nozzle Control via Flow Rate
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Solution Overview
Problem
Internal-combustion engines with turbo superchargers face challenges in controlling the turbine impeller's pressure ratio effectively, leading to potential stress and reduced lifespan due to pressure differences and exhaust pulsation, especially during high load and high revolution states, and existing solutions require multiple sensors for accurate control.
Innovation Solution
A control method and apparatus that calculates the upstream side pressure and temperature based on intake air flow rate, fuel flow rate, and atmospheric pressure, eliminating the need for pressure sensors on both sides of the turbine and reducing sensor requirements, by adjusting the variable nozzle opening degree to maintain a predetermined pressure ratio using pre-stored turbine flow rate characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure sensors are installed on both upstream and downstream sides of the turbine to accurately measure the pressure ratio, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces a turbine flow rate as an intermediary parameter to indirectly determine the pressure ratio. Instead of directly measuring pressure on both sides of the turbine, the system measures the turbine flow rate (which correlates with pressure ratio) and uses pre-stored characteristic data to establish the relationship, thereby avoiding the need for multiple pressure sensors
Solution Approach 2:
The patent replaces direct mechanical pressure measurement systems with a flow rate-based measurement and calculation system. By measuring turbine flow rate and using computational methods with pre-stored characteristics, the system substitutes complex pressure sensing and measurement infrastructure with simpler flow measurement and data processing
2Reliability
If the variable nozzle opening degree is adjusted to maintain a predetermined pressure ratio to protect the turbine impeller, then reliability is improved, but the response speed of pressure ratio control deteriorates due to sensor response delay
Solution Approach 1:
The patent pre-stores the characteristic relationship between turbine flow rate and pressure ratio in advance. When control is needed, the system directly queries the pre-computed characteristics rather than performing real-time pressure measurements and calculations, enabling faster response to protect the turbine impeller
Solution Approach 2:
The patent creates a computational model (copy) of the turbine's pressure-flow characteristics that can be quickly referenced. Instead of relying on slow sensor responses, the system uses this pre-established characteristic curve to determine the appropriate variable nozzle opening degree, achieving rapid control response
Data Source
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AI summary
An internal-combustion engine (10) has a turbo supercharger (30). A control apparatus (50) calculates a fuel flow rate based on an injection quantity of fuel in the engine (10) and a number of revolutions of the engine (10). The control apparatus (50) calculates an upstream side pressure and temperature on an upstream side of a turbine impeller (36A) and a turbine flow rate. The control apparatus (50) calculates an upper limit threshold value of an opening degree level of a variable nozzle (33) of the turbo supercharger (30) such that a turbine pressure ratio is equal to or less than a predetermined ratio on a basis of the turbine flow rate and a pressure ratio-turbine flow rate characteristic. The pressure ratio-turbine flow rate characteristic is pre-stored information indicating a relationship between the turbine pressure ratio, the turbine flow rate, and the opening degree level of the variable nozzle (33). The control apparatus (50) controls an opening degree of the variable nozzle (33) so as to be an opening degree equal to or less than the upper limit threshold value.