Cryogenic Pump Lubrication via LNG Entrainment
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Solution Overview
Problem
Cryogenic pumps used in engine systems face a short operating life due to the lack of lubrication for seals, as lubricants freeze at low temperatures, making it difficult to introduce lubrication into the system.
Innovation Solution
A lubricant system that introduces a lubricant into the LNG flow path, allowing it to be entrained in the LNG and carried into the tank, where it can sublimate and lubricate the pumping element and seals, extending the operating life of the pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lubricant is introduced into the cryogenic pump system, then the seal lubrication is improved and operating life is extended, but the lubricant freezes at low temperatures making it difficult to introduce into the system
Solution Approach 1:
The lubricant is introduced into the LNG during the filling operation before the pump begins operation. The lubricant injection system is activated when LNG is being pumped into the storage tank, allowing the lubricant to be mixed with the LNG at a temperature above the lubricant's freezing point, then carried into the pump where it provides lubrication.
Solution Approach 2:
The LNG serves as an intermediary carrier for the lubricant. Instead of introducing lubricant directly into the pump where it would freeze, the lubricant is injected into the LNG stream, which carries the lubricant into the pump assembly. The LNG acts as a medium that transports the lubricant to the seal interface without the lubricant freezing during transport.
2Duration of action of stationary object
If traditional lubrication methods are used, then the system structure remains simple, but the seal wear increases and operating life decreases
Solution Approach 1:
The LNG filling system serves multiple functions: it not only fills the storage tank with LNG but also acts as the delivery mechanism for introducing lubricant into the pump system. The existing pump infrastructure is utilized to both pump LNG and to deliver the lubricant, eliminating the need for separate lubricant delivery equipment.
Solution Approach 2:
The pump system lubricates itself through the LNG flow. During normal pump operation and LNG filling, the lubricant is automatically introduced and distributed to the seal interfaces through the existing LNG flow paths, without requiring external lubrication systems or manual intervention.
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 lubricant system effectively lubricates the pumping element and seals, thereby extending the operating life of the cryogenic pump by ensuring continuous lubrication even at cryogenic temperatures.
Implementation Method 1
introduce the lubricant via the lubricant inlet passage into the flow of LNG in the LNG inlet passage such that at least a portion of the lubricant is entrained in the LNG in the LNG inlet passage
Implementation Method 2
wherein the lubricant lubricates the pumping element and the seal
Data Source
AI summary
A cryogenic LNG fuel system is provided that includes a tank for storing LNG and a LNG fill system including a LNG inlet passage for directing a flow of LNG into the tank. A cryogenic pump is in fluid communication with the tank and includes a pumping element at least partially immersed in the LNG for directing the LNG out of the tank and a seal. A lubricant system is provided that includes a lubricant reservoir and a lubricant inlet passage in communication with the lubricant reservoir and the LNG inlet passage. The lubricant system is adapted to introduce the lubricant into the flow of LNG in the LNG inlet passage such that at least a portion of the lubricant is entrained in the LNG in the LNG inlet passage and carried into the tank.