Variable Volume Gear Pump for Urea Freezing Protection
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Solution Overview
Problem
Gear pumps used to feed urea solutions in diesel engines face issues with freezing media at low temperatures, leading to increased volume and potential damage, as they struggle to accommodate the expansion without compromising performance or efficiency.
Innovation Solution
A gear pump design featuring a displaceable cover that increases chamber volume when temperatures drop, allowing the liquid to expand without exceeding critical pressure, combined with a spring element for adjustable preload and pressure management, creating a bypass to equalize pressure and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a gear pump is used to feed liquid urea solution, then higher performance and pumping efficiency are achieved, but the pump cannot withstand the volume increase when the liquid freezes at low temperatures
Solution Approach 1:
The cover is made displaceable rather than fixed, allowing the chamber volume to dynamically adjust in response to freezing conditions. When the liquid freezes and expands, the cover moves to increase chamber volume, accommodating the expansion without damaging the pump structure.
Solution Approach 2:
The chamber volume parameter is made variable through the displaceable cover design. This allows the system to change its volume parameter in response to temperature changes and freezing conditions, enabling the pump to handle both liquid and frozen states of the urea solution.
2Reliability
If the chamber volume is increased to accommodate frozen medium expansion, then ice pressure protection is provided, but the maximum delivery volume of the pump decreases
Solution Approach 1:
The cover displacement is not fixed but responds dynamically to pressure conditions. During normal operation, the cover maintains a position that maximizes delivery volume. Only when freezing occurs and pressure exceeds the spring force does the cover displace to increase volume for ice protection.
Solution Approach 2:
The spring element applies a preliminary force to keep the cover in its normal position, maximizing delivery volume under normal operating conditions. This preliminary action ensures that the cover only moves when necessary, i.e., when freezing pressure overcomes the spring force.
3Reliability
If a displaceable cover is used to increase chamber volume for frozen medium, then volume expansion is accommodated, but the liquid pressure may not be maintained during normal operation
Solution Approach 1:
The spring element acts as a counterforce mechanism, applying a preliminary force to the cover that opposes the pressure from the liquid medium. This spring force is calibrated to maintain the cover in its normal position during typical operating pressures, ensuring pressure maintenance while still allowing displacement when freezing occurs.
Solution Approach 2:
The system uses parameter changes in the spring force to balance between maintaining pressure during normal operation and allowing volume expansion during freezing. The spring constant and preload are selected to create different operational regimes based on the medium state.
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 gear pump effectively manages ice pressure and maintains performance by allowing volume expansion of the liquid medium at low temperatures, ensuring the pump operates without damage and maintaining efficient pressure control, thus replacing diaphragm pumps in such scenarios.
Implementation Method 1
By setting a corresponding prestressing force, with which the cover is pushed in the direction of the gears, in order to reduce the chamber volume or keep it small
Implementation Method 2
these freeze at low temperatures, for example approximately −12° C. in the case of the urea solution, which leads to an increase in volume of the medium
Implementation Method 3
the displacement connects the pressure side to the suction side of the gear pump or the chamber, thus creating a bypass that serves to reduce pressure or limit delivery pressure
Data Source
Figure 1
Figure 2
AI summary
The gear pump (1) has a housing (2), which has a chamber (20), in which two intermeshing gears (9,10) are pivoted. The housing has an inlet guiding into the chamber and an outlet passing out from the chamber. A cover (19) is provided for bordering the chamber from a front side. The cover is displaced for increasing the chamber volume in an area wise manner. The cover is axially displaceable. A spring element (23) is assigned to the cover, where the spring element impinges the cover with the spring force in the direction of the intermeshing gears.