Turbocharged Engine Crankcase Ventilation Pressure Management
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Solution Overview
Problem
Conventional crankcase ventilation systems for turbocharged engines face challenges in maintaining appropriate crankcase pressure under varying operating conditions, leading to potential seal failure and oil degradation due to insufficient fresh air dilution of blowby gases.
Innovation Solution
A PCV bypass system that allows controlled flow of pressurized air into the crankcase during boosted states, decoupling flow control components to enable independent sizing and maintain desirable crankcase pressure across all operating conditions, including an idle and boosted state, with a pressure relief valve to prevent over-pressurization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a restriction is placed in the breather vent line to maintain negative crankcase pressure at idle, then crankcase sealing integrity is improved during idle operation, but the crankcase becomes over-pressurized during full load operation
Solution Approach 1:
The system dynamically switches between two ventilation paths based on operating conditions. During idle, the breather provides restricted fresh air flow to maintain negative pressure. During boosted operation, the PCV bypass activates to provide unrestricted flow capacity, allowing the system to adapt to changing pressure conditions and prevent over-pressurization while maintaining sealing integrity
Solution Approach 2:
The invention changes the flow capacity parameter of the ventilation system based on operating state. The PCV bypass provides a second flow path with different flow characteristics that activates under specific pressure conditions, effectively changing the system's overall flow capacity to match the demands of boosted operation versus idle operation
2Reliability
If fresh air feed to the crankcase is restricted too much to maintain vacuum at idle, then idle operation is improved, but blowby gases are insufficiently diluted during boosted operation
Solution Approach 1:
The ventilation system is segmented into two separate flow paths: the breather path for idle operation with restricted flow, and the PCV bypass path for boosted operation with high flow capacity. This segmentation allows each path to be optimized for its specific operating condition, ensuring adequate blowby gas dilution during boosted operation while maintaining stable idle operation
Solution Approach 2:
The PCV bypass acts as an intermediary flow path that activates during boosted operation to provide additional fresh air to the crankcase. This intermediary path bypasses the restriction in the breather, ensuring that blowby gases are adequately diluted during high-load operation without compromising idle operation stability
3Object-generated harmful factors
If the PCV bypass allows unrestricted fresh air flow into the crankcase during boosted operation, then blowby gas dilution is improved, but the system complexity increases due to additional flow control components
Solution Approach 1:
The PCV bypass utilizes existing PCV valve components and integration points in the ventilation system, making the additional flow path compatible with the existing infrastructure. This multi-functional approach allows the system to handle both idle and boosted operation requirements using a unified design framework, reducing the incremental complexity of adding the bypass functionality
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
Ensures proper crankcase pressure management and prevents oil degradation by ensuring adequate fresh air dilution of blowby gases, enhancing engine performance and reducing emissions.
Implementation Method 1
A PCV bypass is configured to permit a one-way flow into the crankcase via the second vent line bypassing the PCV valve in the boosted state
Data Source
AI summary
A crankcase ventilation system for a turbocharged engine has full bi-directional flow for an idle state and a boosted state. A PCV valve provides air flow from the crankcase to the intake manifold in the idle state. A restriction in a first vent line limits fresh air into the crankcase in the idle state. A PCV bypass permits a one-way flow into the crankcase via a second vent line bypassing the PCV valve in the boosted state. A pressure relief valve in communication with the first vent line is configured to bypass the restriction in the boosted state when a pressure in the crankcase exceeds a threshold pressure. In a preferred embodiment, the PCV bypass is configured to bypass both the PCV valve and a pull separator (i.e., oil separator at the second vent line) in the boosted state.