Crankcase Ventilation for Natural Gas Compression Engines
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Solution Overview
Problem
Natural gas compression systems using internal combustion engines face safety concerns due to combustible gas leakage into the engine crankcase, which existing ventilation systems fail to adequately purge, leading to potential combustible mixtures.
Innovation Solution
Enhanced crankcase ventilation systems that route outside air through the crankcase at a rate equal to or greater than the gas leakage rate, using a blower or ensuring all intake air passes through the crankcase before entering the intake manifold, to prevent the formation of combustible mixtures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard PCV system is used to vent crankcase gases, then the system structure remains simple, but the ventilation rate is insufficient to prevent combustible mixture formation
Solution Approach 1:
The system pre-flushes the crankcase with fresh air before compression gas can leak into it, and maintains continuous flushing during operation. This preliminary and ongoing action ensures that when gas leakage occurs, the crankcase is already filled with non-combustible air, preventing combustible mixture formation.
Solution Approach 2:
Fresh air acts as an intermediary substance that displaces and dilutes the compression gas in the crankcase. By introducing this intermediate fluid (fresh air) between the source of harmful gas (compression cylinder leakage) and the potential combustion zone, the system prevents combustible mixture formation without requiring complex detection or control mechanisms.
2Reliability
If air flow rate through the crankcase is increased to purge leaked gas effectively, then safety is improved, but energy consumption increases
Solution Approach 1:
The ventilation system serves multiple functions simultaneously: it flushes compression gas from the crankcase, provides forced induction air to the combustion cylinders, and creates negative pressure to prevent gas leakage. By making the air intake system multi-functional, the system achieves high safety standards without requiring dedicated energy-consuming ventilation equipment.
Solution Approach 2:
The system uses the engine's own intake air requirement to drive the crankcase flushing function. The air that would otherwise be wasted or require separate ventilation handling is instead utilized to purge the crankcase, making the system self-sufficient and eliminating additional energy consumption for dedicated ventilation.
3Reliability
If all intake air is routed through the crankcase, then gas purging is maximized, but the device complexity increases
Solution Approach 1:
The system merges the crankcase flushing function with the existing intake air routing. Instead of creating separate pathways for flushing air and intake air, both functions share the same air source and routing infrastructure, achieving maximum purging effectiveness while maintaining simple device architecture.
Solution Approach 2:
The intake air system is designed to serve dual purposes: providing combustion air to the cylinders and simultaneously flushing the crankcase. This multi-functionality allows all intake air to route through the crankcase without requiring additional valves, passages, or control mechanisms beyond what already exists in the engine design.
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
Effectively prevents the formation of combustible mixtures in the crankcase by ensuring the crankcase is flushed with air at a rate that dilutes and eliminates any leaked compressed gas, enhancing safety by preventing the concentration of combustible gases.
Implementation Method 1
a blower in fluid communication with the breather
Implementation Method 2
a check valve disposed between the crankcase and the intake manifold
Implementation Method 3
The flow through the crankcase 14 is driven by the pressure differential between an intake air filter 48 (close to ambient pressure) and the intake manifold 42 (typically at a vacuum with respect to ambient pressure.)
Data Source
AI summary
An internal combustion engine may be used to compress natural gas for vehicle fuel. The engine may contain a plurality of gas compression cylinders, at least one standard combustion cylinder to drive the compression cylinders, and a common crankshaft in a crankcase coupling the compression cylinders and the at least one standard combustion cylinder. Some combustible gas being compressed may leak past the piston rings of the compression cylinders into the engine crankcase posing a safety concern. This invention eliminates this concern by actively flushing the crankcase at a higher rate than normal.