Crankcase Ventilation Jet Pump Backflow Prevention
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Solution Overview
Problem
Crankcase ventilation systems for internal combustion engines face backflow issues due to pressure differentials between the crankcase and the oil outlet of air/oil separators, which traditional solutions like gravity-fed connections attempt to overcome but are not always effective.
Innovation Solution
Incorporating a jet pump that uses a pressurized motive fluid to create a pumping effect, overcoming the pressure differential and preventing backflow by actively suctioning and pumping scavenged oil from the separator back to the crankcase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a gravity-fed vertical connection tube with check valve is used to drain oil from the separator, then the structure is simple, but the backflow of oil from the crankcase to the oil outlet cannot be effectively overcome
Solution Approach 1:
The patent applies pneumatic principles by using a jet pump that utilizes fluid flow (motive fluid) to create a suction effect. The jet pump receives pressurized motive fluid that creates a low-pressure zone at the suction port, enabling it to draw scavenged oil against the pressure differential from the separator back to the crankcase, thereby overcoming the backflow problem without relying solely on gravity.
Solution Approach 2:
The patent replaces the purely mechanical gravity-fed system with a fluid-dynamic jet pump system. Instead of relying on gravitational force and a check valve, the system uses the momentum exchange between the high-velocity motive jet and surrounding fluid to create a pumping action that actively prevents backflow and ensures reliable oil return.
2Reliability
If the oil outlet is located at a higher elevation to use gravity head, then backflow is reduced, but the system requires additional vertical space and complex routing
Solution Approach 1:
The jet pump system eliminates the need for elevated oil outlet positioning by using fluid dynamic principles. The pressurized motive fluid creates a suction effect that draws oil from the separator at any convenient location back to the crankcase, removing the constraint of vertical elevation differences and simplifying the routing requirements.
Solution Approach 2:
Instead of solving the backflow problem by working in the vertical dimension (using gravity head through elevation differences), the jet pump approach works in the fluid dynamic dimension, using pressure differential and momentum exchange to achieve the same objective without vertical routing constraints.
3Reliability
If a jet pump is used to actively pump scavenged oil back to the crankcase, then backflow is effectively prevented, but the device complexity increases
Solution Approach 1:
The jet pump is designed to be self-regulating through the inherent fluid dynamic principles. The motive fluid flow automatically creates the necessary suction pressure at the suction port, and the system self-adjusts to maintain proper flow rates without requiring external control mechanisms, reducing operational complexity despite the added pumping function.
Solution Approach 2:
The jet pump utilizes the natural properties of fluid flow and momentum exchange to create the pumping action. By directing pressurized motive fluid through a nozzle, the system harnesses the resulting low-pressure zone and suction effect to draw oil, eliminating the need for complex mechanical pumping mechanisms while achieving reliable backflow prevention.
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
The jet pump effectively prevents backflow and ensures efficient return of scavenged oil to the crankcase, enhancing the crankcase ventilation system's performance by utilizing the momentum exchange between the high-velocity motive jet and surrounding fluid to create a sufficient pumping pressure.
Implementation Method 1
The momentum exchange between the high velocity motive jet flow from motive jet nozzle 40 and the lower velocity surrounding fluid in mixing bore 42 creates the pumping effect which suctions and pumps fluid from chamber 44
Implementation Method 2
The pressure differential between the crankcase and the oil outlet of the separator normally tends to cause backflow of oil from the higher pressure crankcase to the lower pressure oil outlet
Data Source
AI summary
A crankcase ventilation system for an internal combustion engine has a jet pump suctioning scavenged separated oil from the oil outlet of an air/oil separator and pumping same to the crankcase.