COOLING FAN AND SYSTEM PERFORMANCE AND EFFICIENCY IMPROVEMENTS

Dupree, Ronald

Caterpillar Incorporated

关键词: Blowers;    Aluminium;    Testing;    Filtration;    Reynolds Number;   

DOI  :  10.2172/1028966
RP-ID  :  None
RP-ID  :  FC26-02AL68081
RP-ID  :  1028966

美国|英语

来源: UNT Digital Library

【 摘 要 】

Upcoming emissions regulations (Tiers 3, 4a and 4b) are imposing significantly higher heat loads on the cooling system than lesser regulated machines. This work was a suite of tasks aimed at reducing the parasitic losses of the cooling system, or improving the design process through six distinct tasks: 1. Develop an axial fan that will provide more airflow, with less input power and less noise. The initial plan was to use Genetic Algorithms to do an automated fan design, incorporating forward sweep for low noise. First and second generation concepts could not meet either performance or sound goals. An experienced turbomachinery designer, using a specialized CFD analysis program has taken over the design and has been able to demonstrate a 5% flow improvement (vs 10% goal) and 10% efficiency improvement (vs 10% goal) using blade twist only. 2. Fan shroud developments, using an 'aeroshroud' concept developed at Michigan State University. Performance testing at Michigan State University showed the design is capable of meeting the goal of a 10% increase in flow, but over a very narrow operating range of fan performance. The goal of 10% increase in fan efficiency was not met. Fan noise was reduced from 0 to 2dB, vs. a goal of 5dB at constant airflow. The narrow range of fan operating conditions affected by the aeroshroud makes this concept unattractive for further development at this time 3. Improved axial fan system modeling is needed to accommodate the numbers of cooling systems to be redesigned to meet lower emissions requirements. A CFD fan system modeling guide has been completed and transferred to design engineers. Current, uncontrolled modeling practices produce flow estimates in some cases within 5% of measured values, and in some cases within 25% of measured values. The techniques in the modeling guide reduced variability to the goal of + 5% for the case under study. 4. Demonstrate the performance and design versatility of a high performance fan. A 'swept blade mixed flow' fan was rapid prototyped from cast aluminum for a performance demonstration on a small construction machine. The fan was mounted directly in place of the conventional fan (relatively close to the engine). The goal was to provide equal airflow at constant fan speed, with 75% of the input power and 5 dB quieter than the conventional fan. The result was a significant loss in flow with the prototype due to its sensitivity to downstream blockage. This sensitivity to downstream blockage affects flow, efficiency, and noise all negatively, and further development was terminated. 5. Develop a high efficiency variable speed fan drive to replace existing slipping clutch style fan drives. The goal for this task was to provide a continuously variable speed fan drive with an efficiency of 95%+ at max speed, and losses no greater than at max speed as the fan speed would vary throughout its entire speed range. The process developed to quantify the fuel savings potential of a variable speed fan drive has produced a simple tool to predict the fuel savings of a variable speed drive, and has sparked significant interest in the use of variable speed fan drive for Tier 3 emissions compliant machines. The proposed dual ratio slipping clutch variable speed fan drive can provide a more efficient system than a conventional single ratio slipping clutch fan drive, but could not meet the established performance goals of this task, so this task was halted in a gate review prior to the start of detailed design. 6. Develop a cooling system air filtration device to allow the use of automotive style high performance heat exchangers currently in off road machines. The goal of this task was to provide a radiator air filtration system that could allow high fin density, louvered radiators to operate in a find dust application with the same resistance to fouling as a current production off-road radiator design. Initial sensitivity testing demonstrated that fan speed has a significant impact on the fouling of radiator cores due to fine dusts, so machines equipped with continuously variable speed fan drives would be expected to have more radiator debris fouling problems than a machine with a constant speed fan. Filtration concepts looked at a wide range of filtration technologies, but the combination of pressure drop constraints and the small size of the debris to be filtered made this a futile exercise. The most successful technologies evaluated all incorporate some way to increase the Reynolds number inside the heat exchanger air flow path. A form of an 'air knife' concept has emerged as the most promising technology to pursue.