Rotating Coalescer Dynamic Seal for Crankcase Ventilation
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Solution Overview
Problem
Crankcase ventilation systems employing rotating coalescers face inefficiencies due to unfiltered aerosols bypassing the filter media through gaps between rotating and stationary components, leading to reduced filtration efficiency, especially for larger aerosol sizes.
Innovation Solution
The implementation of a CV system with a rotating coalescer that creates a pumping pressure differential between the clean and dirty sides of the filter media, utilizing porous media and internal radial ribs or spiral vanes to maintain positive recirculation of filtered gases through potential leak gaps, preventing unfiltered gases from bypassing the filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a gap is maintained between the rotating coalescer and the static housing for mechanical clearance, then ease of operation and device assembly are improved, but unfiltered aerosols can bypass the filter media through the gap, reducing filtration efficiency
Solution Approach 1:
A dynamic seal is introduced as an intermediary component between the rotating coalescer and static housing. The seal maintains the necessary mechanical clearance while preventing unfiltered aerosols from bypassing the filter media through the gap, thus resolving the contradiction between ease of operation and filtration efficiency
Solution Approach 2:
The dynamic seal utilizes a flexible membrane or thin film structure that can accommodate rotational movement while maintaining sealing effectiveness. This flexible barrier prevents aerosol bypass through the gap without compromising the mechanical clearance needed for operation
2Productivity
If the downstream pressure on the clean side is lower than the upstream pressure on the dirty side, then gas flow through the filter media is maintained, but unfiltered aerosols bypass the rotating coalescer through the gap
Solution Approach 1:
The dynamic seal acts as an intermediary that prevents bypass flow through the gap while allowing the pressure differential necessary for gas flow through the filter media to be maintained, thus preserving both productivity and filtration efficiency
Solution Approach 2:
The system utilizes pneumatic pressure differential to drive gas flow through the filter media while the dynamic seal prevents pneumatic bypass through the gap, maintaining the pressure relationship needed for efficient filtration without sacrificing flow rate
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 enhances filtration efficiency by ensuring all blowby gases are filtered, maintaining high pressure on the clean side and low pressure on the dirty side, thereby preventing bypass and improving drainage and pressure drop across the filter.
Implementation Method 1
By rotating the media, inertial impaction is enhanced by the additional centrifugal force. In addition to this aspect, after the oil droplets coalesce to form larger drops, the centrifugal force removes the larger drops by overcoming the surface drag force of the media fibers.
Implementation Method 2
The central shaft is rotatable such that when the central shaft rotates, the rotating coalescer rotates and creates a pumping pressure that causes a high pressure within the housing on the clean side of the filter media and a low pressure on the dirty side of the filter media.
Implementation Method 3
In rotating coalescers, the oil droplets (e.g., aerosol) suspended and transported by the blowby gases are separated inside the coalescer media through the particle capture mechanisms of inertial impaction, interception, and diffusion onto the fibers.
Implementation Method 4
In rotating coalescers, the oil droplets (e.g., aerosol) suspended and transported by the blowby gases are separated inside the coalescer media through the particle capture mechanisms of inertial impaction, interception, and diffusion onto the fibers.
Implementation Method 5
In rotating coalescers, the oil droplets (e.g., aerosol) suspended and transported by the blowby gases are separated inside the coalescer media through the particle capture mechanisms of inertial impaction, interception, and diffusion onto the fibers.
Implementation Method 6
after the oil droplets coalesce to form larger drops, the centrifugal force removes the larger drops by overcoming the surface drag force of the media fibers. This aspect increases the collection of and the discharge of oil from the coalescer by providing improved drainage
Data Source
AI summary
Rotating coalescer crankcase ventilation (CV) systems are described. The described CV systems utilize a pumping pressure created by the porous media of the rotating coalescer to maintain positive recirculation of filtered blowby gases through a potential leak gap between a static housing inlet and a spinning component of the rotating coalescer. In some arrangements, the porous media is fibrous media. The filter media may be pleated or non-pleated. The positive recirculation caused by the pressure balance prevents unfiltered blowby gases from bypassing the media of the rotating coalescer from the upstream side to the downstream side of the filter media through the gap. During operation, the pressure balance between the upstream side and downstream side of the filter media maintains the positive recirculation, which in turn maintains a high filtration efficiency.