Dual-Stage Cryogenic Pump Flash Boiling Prevention
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Solution Overview
Problem
Cryogenic pump systems face challenges with flash boiling due to low pressures during retracting strokes, leading to distortion of cylinder blocks and increased costs and complexity in accommodating pressure spikes, especially in applications involving liquefied natural gas.
Innovation Solution
A dual-stage axial piston pump design with a boost enclosure and main plunger, featuring inlet passages with a combined cross-sectional area of 0.4-0.7 times the boost plunger's area, and check valves to manage pressure and prevent flash boiling, along with a free-floating main plunger to enhance pressure increase and reduce leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If large-diameter slow-moving pistons are used to minimize pressure during retracting strokes, then flash boiling is avoided, but the pump becomes large, heavy, and expensive with high-pressure spikes
Solution Approach 1:
The pump is divided into two stages: a boost stage with a boost plunger that pre-pressurizes the fluid, and a main stage with a main piston that performs the primary pumping function. This segmentation allows the main piston to operate with smaller diameter and higher speed while the boost stage maintains sufficient pressure to prevent flash boiling during retracting strokes.
Solution Approach 2:
A boost enclosure containing hydraulic oil acts as an intermediary medium between the boost plunger and the main piston. The hydraulic oil transmits pressure from the boost plunger to the main piston, enabling pressure amplification and allowing the main piston to operate at lower pressures during retraction, thus preventing flash boiling without requiring large diameter.
2Object-affected harmful factors
If an additional boost pump is incorporated to elevate pressure, then flash boiling is avoided, but system cost and complexity increase
Solution Approach 1:
The boost stage and main stage are merged into a single integrated pump unit sharing a common crankshaft, barrel, and fluid pathway. This combination eliminates the need for a separate boost pump while achieving the same pressure-elevation function, thereby reducing system complexity and component count.
Solution Approach 2:
The crankshaft serves multiple functions: it drives both the boost plunger and the main piston through shared connecting mechanisms, and it coordinates the timing of both stages to work together as an integrated system. This multi-functionality reduces the need for separate driving mechanisms.
3Stress or pressure
If high pressure is generated to meet cryogenic application requirements, then fluid delivery is sufficient, but cylinder blocks experience distortion
Solution Approach 1:
The pressure generation is segmented into two stages: the boost stage generates intermediate pressure, and the main stage generates final high pressure. This segmentation distributes the pressure-generation load, reducing peak stresses on any single component including the cylinder block, thereby minimizing distortion while still achieving the required high pressure output.
Solution Approach 2:
The pump utilizes dynamic reciprocating motion with carefully timed suction and discharge strokes. The suction strokes occur when pressure requirements are lower, allowing fluid intake without excessive force on the cylinder block. The discharge strokes deliver high pressure in controlled pulses rather than continuous load, reducing cumulative stress and distortion on the cylinder block.
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 design effectively prevents flash boiling and reduces distortion, enabling high-pressure generation with improved reliability and efficiency in cryogenic applications, while minimizing the occurrence of flash boiling and maintaining pump longevity.
Implementation Method 1
check valves to manage pressure and prevent flash boiling
Implementation Method 2
boost plunger disposed inside the barrel and configured to discharge fluid into the boost enclosure
Implementation Method 3
main plunger disposed inside the barrel and configured to receive fluid from the boost enclosure and to increase a pressure of the fluid
Data Source
AI summary
A pump for use in pressurizing a cryogenic fluid. The pump may have a barrel, and a boost enclosure disposed around the barrel. The pump may also have a boost plunger disposed inside the barrel and configured to discharge fluid into the boost enclosure. The pump may further have a main plunger disposed inside the barrel and configured to receive fluid from the boost enclosure and to increase a pressure of the fluid.