Air Cleaner Flow Straightening Grid for Mass Flowmeter Accuracy
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Solution Overview
Problem
In large-sized diesel engines, existing air cleaners with concentric inner and outer cylindrical filters face challenges in accurately measuring air flow rates due to variations in filter papers and positional relationships, leading to potential turbulence and uneven air flow, which affects the accuracy of mass flowmeter measurements and subsequently the engine's EGR control.
Innovation Solution
An air cleaner design incorporating a flow straightening grid with a metal mesh or perforated metal, positioned between the bottom and inner cylindrical filter, to straighten the air flow before measurement by a mass flowmeter, ensuring accurate flow rate detection and improved air cleanliness, while maintaining a space ratio between 30% to 50% and wire diameter of 0.2 mm or larger to prevent pressure loss and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a double-layered filter structure (inner cylindrical filter and outer cylindrical filter) is used to improve air cleanliness, then air filtration effectiveness is improved, but air flow uniformity deteriorates due to variations in filter papers and positional relationships
Solution Approach 1:
A flow straightening grid is introduced as an intermediary component between the double-layered filter structure and the mass flowmeter. This grid mediates the turbulent flow generated by the filters, straightening it before the air reaches the measurement device, thereby resolving the contradiction between maintaining filter effectiveness and achieving flow uniformity for accurate measurement.
2Measurement precision
If the flow straightening grid is made with finer mesh to improve flow straightening effectiveness, then measurement accuracy is improved, but pressure loss increases
Solution Approach 1:
The patent optimizes the physical parameters of the flow straightening grid, specifically the wire diameter (0.2 mm or larger) and space ratio (30%-50%), to achieve the best balance between flow straightening effectiveness and pressure loss. This parameter optimization resolves the contradiction between measurement accuracy and energy loss.
3Loss of energy
If the flow straightening grid is made with thinner wires to reduce pressure loss, then energy loss is reduced, but durability deteriorates due to potential damage from dust particles
Solution Approach 1:
The patent specifies a minimum wire diameter of 0.2 mm for the flow straightening grid, establishing an optimal parameter range that balances pressure loss and durability. This parameter setting ensures the grid is robust enough to withstand dust particle impact while maintaining acceptable pressure loss characteristics.
4Volume of moving object
If the mass flowmeter is positioned closer to the filters to reduce space, then device compactness is improved, but measurement accuracy deteriorates due to turbulent flow
Solution Approach 1:
The flow straightening grid serves as an intermediary component that enables the mass flowmeter to be positioned closer to the filters while maintaining measurement accuracy. By straightening the flow in the limited space available, the grid allows compact arrangement without sacrificing measurement precision.
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 solution enables highly accurate measurement of air flow rates, enhances air cleanliness by preventing turbulence, and allows for precise EGR control, reducing pressure loss and ensuring long-term durability of the flow straightening grid.
Implementation Method 1
a flow straightening grid is provided at an upstream side of the mass flowmeter to straighten the flow of the air in the downstream-side pipe
Implementation Method 2
a mass flowmeter is provided in the downstream-side pipe to measure a flow rate of the air in the downstream-side pipe
Implementation Method 3
the supplied outside air is filtered through a double-layered structure of the inner cylindrical filter and the outer cylindrical filter
Data Source
AI summary
An air cleaner includes a case in which an inner cylindrical filter and an outer cylindrical filter are housed, the case having a case body that defines an opening end surface closed by a cover member. The case includes an air inlet provided to an outer circumference of the case body for supplying outside air and an exhaust outlet provided to a bottom of the case body at a downstream side in an air-flowing direction for discharging the air supplied through the air inlet and filtered through the inner cylindrical filter and the outer cylindrical filter. A mass flow rate sensor is provided in the exhaust outlet to measure the flow rate of the air. A flow straightening grid is provided at the upstream side of the mass flow rate sensor to straighten the flow of the air.