Cross-Flow Fan Cutoff Wall for Uniform Airflow
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Solution Overview
Problem
Existing combine harvester cleaning systems face challenges in achieving uniform airflow distribution across the width of the outlet ducts, leading to uneven cleaning efficiency due to variations in grain properties and environmental conditions, exacerbated by the increasing width of modern harvesters and the nature of cross-flow fans.
Innovation Solution
A cross-flow fan system with specific structural and dimensional features, including a cutoff wall assembly with adjustable second cutoff wall and a rotor shroud, is designed to improve airflow distribution and stability, with parameters such as cutoff wall distance, fan rotation diameter, and radial vane distance optimized to enhance airflow uniformity across the width of the sieves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the harvester width is increased to accommodate greater volumes of incoming crop material, then the cleaning system capacity is improved, but the airflow distribution uniformity across the width of the outlet ducts deteriorates
Solution Approach 1:
The outlet duct system is divided into multiple separate outlet ducts (first outlet duct, second outlet duct, etc.) arranged across the width of the cleaning system. Each outlet duct receives airflow from the cross-flow fan and distributes it to corresponding sieves. This segmentation allows independent airflow control and distribution to different zones, maintaining uniform airflow even as the overall system width increases to handle greater crop material volumes.
Solution Approach 2:
The system employs adjustable deflectors or dampers in each outlet duct to locally modify airflow distribution. These adjustable components allow the airflow volume and direction to be tailored for each specific outlet duct and sieve combination, ensuring that each local region receives the appropriate amount of airflow regardless of the overall system width and fan characteristics.
2Productivity
If the number of sieves is increased to perform successively finer separation, then the cleaning efficiency is improved, but the airflow distribution requirements become more complex and difficult to satisfy
Solution Approach 1:
Each sieve is served by its own dedicated outlet duct, creating a one-to-one correspondence between outlet ducts and sieves. This segmentation simplifies the airflow distribution system by allowing each duct-sieve pair to be independently optimized. The cross-flow fan provides airflow that is then distributed through multiple separate pathways, each tailored to the specific requirements of its associated sieve, making it easier to satisfy diverse airflow requirements without increasing overall system complexity.
Solution Approach 2:
The outlet ducts incorporate adjustable deflectors or dampers that can be modified to change airflow distribution. This dynamic adjustment capability allows the system to adapt to varying grain properties and operating conditions, optimizing airflow to each sieve as needed. The adjustability compensates for the complexity introduced by having multiple sieves with different airflow requirements.
3Area of stationary object
If the outlet ducts are designed to distribute airflow to multiple locations, then the cleaning system coverage is improved, but the airflow uniformity across the width deteriorates due to fan characteristics
Solution Approach 1:
The outlet duct system is segmented into multiple independent ducts, each serving a specific zone or sieve. This segmentation breaks up the airflow distribution task into manageable sections, allowing each duct to maintain more uniform airflow over its specific coverage area. The modular duct structure, potentially with intermediate expansion sections, helps preserve airflow uniformity while extending coverage across the full width of the cleaning system.
Solution Approach 2:
Each outlet duct is equipped with local adjustment mechanisms (deflectors, dampers) that allow the airflow characteristics to be optimized for that specific duct's coverage area. This local control compensates for variations in fan airflow patterns and ensures uniform distribution across each local zone, even though the overall system covers a wide area with multiple ducts working in parallel.
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 improved fan system achieves more stable and even airflow distribution, resulting in more uniform and efficient grain separation across the width of the sieves, even under varying conditions, leading to enhanced cleaning performance and consistency.
Implementation Method 1
a cross flow fan rotor configured to rotate about a fan axis in a rotation direction, the cross flow fan rotor having a plurality of vanes... the distal vane edges defining a cylindrical rotation volume
Data Source
AI summary
A harvester cleaning fan system having a cross flow fan rotor, a fan inlet, a rotor shroud, a fan outlet and a cutoff wall assembly. The fan inlet extends in the fan rotation direction around a first portion of the cylindrical rotation volume. The rotor shroud is adjacent the fan inlet and extends in the rotation direction to enclose a second portion of the cylindrical rotation volume. The fan outlet is adjacent the rotor shroud. The cutoff wall assembly extends in the rotation direction by a cutoff wall distance to enclose a third portion of the cylindrical rotation volume. The cutoff wall assembly has a first cutoff wall and a second cutoff wall. The cutoff wall distance is about 40 mm to about 90 mm, and the fan has a rotation diameter of about 400 mm to about 500 mm. An agricultural vehicle having a cleaning fan is also provided.