Vibration DIC Test of Outdoor Air Conditioner Unit

During startup, operation and shutdown of an air conditioning system, various parts generate corresponding stress and vibration. Without testing and control, severe vibration not only produces greater noise, but also accelerates fatigue damage to the compressor, pipelines and other related parts, reducing user comfort and the service life of the air conditioner during operation.

To meet this application requirement, a well-known domestic home appliance brand used the monocular 3D standardized high-speed visual strain gauge from Haytham Technology (model: Blue Box 500W) to test the pipeline vibration, fan blade out-of-plane displacement and casing vibration of an operating outdoor air conditioning unit. During testing, the outdoor unit ran in variable-frequency mode, and the high-speed visual strain gauge acquired data at a frame rate of 6600Hz.

1. Pipeline vibration test of the outdoor unit 

The casing of the outdoor unit was removed, a black base coat was applied to the pipelines, and white marker points were attached.

After the pipeline vibration data was collected with the high-speed visual strain gauge, the pipeline vibration displacement was calculated through the Haytham single-point tracking function, obtaining displacement results of the outdoor unit pipeline vibration in three directions (X, Y and Z directions). The test results were basically consistent with those measured by the customer using traditional acceleration sensors.

 2. Out-of-plane displacement test of the outdoor unit fan

The fan blades of the outdoor unit were sprayed with white matte primer, and then a speckle pattern was sprayed with black matte paint.

After the fan of the outdoor unit ran stably (600rpm), the out-of-plane displacement (Z direction) data during fan operation was collected.

After selecting 3 points in the displacement field, the Z-direction displacement curves of these 3 points can be quickly viewed, and the Z-direction displacement curves of all 3 points show a periodic distribution.

Using the same single-point tracking function as in the pipeline vibration test, the Z-direction displacement curve of each selected single point was calculated.

The above calculation results show that the maximum vibration amplitude differs with the location of the selected calculation point, that is, the non-uniformity of the blade out-of-plane displacement field results from a certain deformation of the blades during high-speed fan operation.

For a long time, due to the high-speed rotation of fan blades, the customer had no good measurement means for studying blade deformation and thus could not compare results. The Haytham monocular 3D standardized high-speed visual strain gauge features high acquisition frequency and non-contact operation, providing the customer with a method and approach for deformation testing of rotating blades.

 3. Casing vibration test of the outdoor unit

After the speckle pattern was applied to the fan blades, four marker points were arranged on the outer frame of the fan compartment, so that while collecting fan data, the casing vibration of the outdoor unit during operation could also be captured.

Haytham's single-point tracking can track multiple points simultaneously. The casing vibration results of the outdoor unit were calculated with the single-point tracking function, and the curves can be quickly viewed.

The curves show that the Z-direction vibration amplitude of the casing is within 2.5mm, and the results are consistent with those measured by the customer using traditional measurement methods.

Compared with the method of directly measuring the studied object with traditional contact sensors, the "non-contact" measurement characteristic of digital image correlation (DIC) avoids problems of sensor technology such as added weight and the inability to measure data in multiple directions simultaneously. Moreover, DIC technology can provide richer discrete data points than sensor technology and is easy to integrate with other technologies.