Parallel Electric Compressor and Turbocharger Boost System
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Solution Overview
Problem
Turbocharger boosted engines face performance compromises due to 'turbo lag' at low engine speeds and increased electrical demand from continuous use of electric compressors, which can lead to fuel consumption and storage capacity issues.
Innovation Solution
A boosted engine system with a small capacity variable geometry turbocharger and an electrically powered compressor in parallel, using a recirculation circuit to build up pressure before connecting the electric compressor to the engine, thereby avoiding sudden drops in boost pressure and reducing continuous electrical demand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large capacity turbocharger is used to prevent high backpressure and overspeeding at very high exhaust gas flow rates, then engine performance at high speeds is improved, but turbo lag occurs at low engine speeds due to insufficient exhaust gas flow rate to provide sudden increase in boost pressure
Solution Approach 1:
The boosting system is segmented into two independent components: a turbocharger for high-speed operation and an electrically powered compressor for low-to-moderate speed operation. This segmentation allows each component to be optimized for its specific operating range, with the turbocharger providing power at high speeds without causing turbo lag at low speeds
Solution Approach 2:
The system dynamically switches between the turbocharger and electrically powered compressor based on engine operating conditions. The variable geometry turbocharger adjusts its geometry to optimize performance across different operating points, while the electrically powered compressor is activated when exhaust gas flow rate is insufficient to provide required boost pressure
2Speed
If an electrically powered compressor is used continuously to fill in for the turbocharger at low to moderate engine speeds, then turbo lag is overcome, but a large drain on the electrical generation circuit occurs, increasing fuel consumption
Solution Approach 1:
The electrically powered compressor operates periodically rather than continuously, being activated only when the exhaust gas flow rate is insufficient to provide the required boost pressure. This periodic operation significantly reduces the drain on the electrical generation circuit and associated fuel consumption compared to continuous operation
Solution Approach 2:
The system changes operational parameters by switching between natural aspiration (turbocharger only), electrically assisted boosting (electrically powered compressor only or in combination), and full turbocharging based on exhaust gas flow rate and boost pressure requirements, optimizing energy efficiency across different operating conditions
3Power
If an electrically powered compressor is used at very low engine speeds to meet boost pressure demands, then torque demand is met, but additional electrical storage capacity is required to cope with the electrical demands that exceed the output from the electrical generation system
Solution Approach 1:
The system builds up pressure in the recirculation circuit before connecting the electrically powered compressor to the engine. This preliminary action ensures that the compressor is ready to provide immediate boost pressure support when needed, meeting torque demands at very low engine speeds without requiring excessive electrical storage capacity
4Power
If the electrically powered compressor is connected directly to the engine without building up pressure first, then torque demand is met quickly, but a sudden drop in boost pressure occurs upon connecting the compressor to the engine
Solution Approach 1:
The system performs preliminary pressure buildup in the recirculation circuit before connecting the electrically powered compressor to the engine. This ensures that the compressor discharge pressure matches or exceeds the engine intake pressure, preventing sudden pressure drops and ensuring smooth, stable boost pressure when the compressor is connected
Solution Approach 2:
The recirculation circuit acts as an intermediary between the electrically powered compressor and the engine. It allows the compressor to build up pressure independently before connecting to the engine, and provides a buffer that smooths out pressure transitions during connection and disconnection operations
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 provides efficient and quick increase in boost pressure to meet torque demands, enhancing engine performance and reducing electrical drain on the vehicle's system.
Implementation Method 1
operating an electric compressor arranged in parallel with the turbocharger compressor and fluidly disconnected from the engine to increase a second pressure in a recirculation circuit around the electric compressor
Implementation Method 2
a recirculation circuit to build up pressure when the electrically powered compressor is started before the electrically powered compressor is connected to the engine, the recirculation circuit comprising an electrically controlled recirculation valve to control the flow of air through a conduit linking an outlet from the electrically powered compressor to an inlet to the electrically powered compressor
Implementation Method 3
The turbocharger may include a turbine disposed in an exhaust passage of the engine and a compressor disposed in an intake passage of the engine, the compressor driven by rotation of the turbine
Data Source
AI summary
Methods and systems are provided for a boosted engine system having an engine arranged to receive boosted air from a variable geometry turbocharger and an electrically powered compressor arranged in parallel with the turbocharger. During temporary high torque demands above a predefined level, the electrically powered compressor may be used to supplement the flow of boosted air from the turbocharger. Additionally, a recirculation circuit around the electrically powered compressor may be provided to build up pressure in the electrically powered compressor before it is connected to the engine so as to minimize fluctuations in engine boost pressure upon start-up of the electrically powered compressor.