Whirlpool is relatively new to the vacuum cleaner market and is leveraging the Hotpoint brand in the EMEA region. Despite the OEM/ODM approach for this product, Whirlpool wanted to conduct a comprehensive performance analysis of the product’s key parts. The vacuum head is probably the most important part for assuring the best balance between Energy Related Product (ErP) Regulation-compliance, performance in all use cases, and a pleasant user experience.
In recent years, the ErP regulation has introduced the concept of real performance: moving the customer’s attention away from misleading figures like electric motor power (Watts) and suction power (Air-Watts), to performance figures that are closer to the cleaning performance, such as dust pick-up on hard floors and carpets.

EnginSoft created a 3D numerical model of the vacuum cleaner head based on the CAD geometry provided by Whirlpool. The parts were imported into the ANSYS CAD/MESHING system and merged together to achieve an acceptable connectivity. Missing parts, connections and boundary conditions were also generated. The ANSYS CFX solver was used to evaluate the system’s fluid dynamics. The CFD model replicated the test conditions based on the aforementioned ErP regulations: the vacuum head was rested on the floor and centered on a guide inclined at 45 degrees that contained the dust. A semi-spherical air plenum surrounding the volume completed the computational domain. In this approach, the air entered the vacuum head from the semi-spherical space (representing the environment) and was guided along a flexible duct toward the vacuum cleaner’s body (not modeled here).
The resulting CFD model is shown in figures 1 and 2.
Every part of the vacuum head was modeled, including:

• the fully-shaped bottom part that makes contact with the floor. This is an important geometrical detail, since these are the areas in which air can be sucked in by the vacuum cleaner during under the operation of the blower
• the elbowed hood that guides the incoming air into the flexible hose
• the rubber flap in the rear bottom part of the vacuum head
• the flexible connections to rigid pipe

The air’s motion is generated by a centrifugal blower; in order to account for this effect, the engineers implemented a 3D region with a momentum source to reproduce the blower’s working curve in the solver. Also, to properly set up the numerical model, a 3D porous loss was considered: given the mass flow-rate during the free-suction state whenthe vacuum head is not constrained (rested) on the floor, the resistance coefficient was tuned to honor the mass flow-rate supplied. In other words, the corresponding resistance simulates the rest of the vacuum cleaner which was not explicitly modeled. For this reason, this resistance coefficient was used for all the simulations studied.
Based on the air depressurization, the resistance coefficient and the blower curve imposed, the solver generated the mass flow-rate and the fluid dynamics of the entire computational domain.
The mass flow-rate (or the blower’s working point), the level of depressurization and the air-flow direction in the bottom region of the vacuum head (interaction between the floor and the vacuum head) were the main conditions to consider in comparing the different designs.

Figure - New shape of the hood’s entrance area

Figure - Curved shape of the rubber flap

Figure - New shape of the hood’s elbow

Using the baseline results, three kinds of configurations were studied, corresponding to three geometrical modifications. This was done mainly to investigate the sensitivity of the system’s performance to geometric variations.

Modification 1 – new shape of the hood’s intake zone
Using the same depressurization, this modification slightly increased the mass flow-rate. This effect, although not as strong as expected, still represented useful information about how the system reacted to such modification.

Modification 2 – curved shape of the rubber flap
This configuration had the greatest potential to improve the system’s efficiency in the scenario studied. To best compare the performance of the baseline configuration with modification 2’s configuration, they were simulated using the real working curve of the blower (head flow-rate). The result showed that, although the increase of the mass flow-rate through the hoods was similar, the percentage of air captured from the fissure was much higher. This would result in better performance of the vacuum cleaner in the test conditions.

Modification 3 – new shape of the hood’s elbow
Using the same depressurization, this modification did not create any appreciable increase in the mass flow-rate. However, there was a benefit to the smoothness of the flow when air sucked from the outside was guided from the vertical to the horizontal direction. Therefore, the elbow suffered less back-flow.