자동차 시트 쿨링용 고성능·저소음 컴팩트 원심팬 개발

Development of high performance and low noise compact centrifugal fan for cooling automotive seats

Abstract

본 논문에서는 쾌적한 운전 환경을 제공하기 위해 자동차 시트를 냉각시키기 위한 고성능 및 저소음 원심팬을 개발하였다. 먼저 팬 성능 테스터 및 전산유체역학(Computational Fluid Dynamics, CFD) 시뮬레이션을 이용하여 기존 팬 장치의 유동 특성을 분석하였다. 예측한 유동장 분석을 통하여 팬 허브 팁 근처의 와류 및 팬 허브 상단의 정체된 유동 현상이 관측되었다. 이러한 와류 및 정체 유동을 줄이기 위해 두 가지 설계 요소를 고안하였다. 첫째, 팬 날개와 팬 하우징 최소 간극(cut-off)를 증가시켜 난류강도를 줄이고 그 결과로 전체적인 음압 레벨을 줄이고자 하였다. 둘째, 허브 형상은 정체 유동을 줄이기 위해 형상을 변경하였다. 제안된 설계의 타당성을 수치해석을 통해 확인하였다. 수치해석결과를 바탕으로 프로토타입을 제작하고 팬 테스터에서 측정한 성능 곡선(P-Q curve)과 반무향실에서 측정한 음압 레벨의 분석을 통해서 유동과 소음 성능의 향상을 확인하였다.

In this paper, a high-performance and low-noise centrifugal fan is developed for cooling automotive seats which provide a driver with pleasant driving environment. First, the flow characteristics of the existing fan unit was analyzed using a fan performance tester and CFD (Computational Fluid Dynamics) simulations. The analysis of the predicted flow field indicated vortex flow near the tip of fan hub and stagnation flow on the top of fan hub. Two design points are devised to reduce the vortex flow and the stagnation flow observed in the existing fan unit. First, the cut-off clearance which is the minimum distance between the fan blade and the fan housing is increased to reduce the vortex strength and, as a result, to reduce the overall sound pressure level. Second, the hub shape is more modified to eliminate the stagnation flow. The validity of proposed design is confirmed through the numerical analysis. Finally, a prototype is manufactured with a basis on the numerical analysis result and its improved flow and noise performances are confirmed through the P-Q curves measured by using the Fan Tester and the SPL (Sound Pressure Level) levels measured in the anechoic chamber.

Fig. 1. Geometry of original centrifugal fan.

Fig. 2. Schematics of centrifugal fan system.

Fig. 3. Geometry of 95D centrifugal fan.

Fig. 4. Y+ distribution of the rotating part.

Fig. 5. Computational domain.

Fig. 6. Validation of VFR for numerical scheme.

Fig. 7. Distribution of flow velocity vectors on crosssectional plane normal to x-axis for 95D model.

Fig. 8. Distribution of flow velocity vectors on crosssectional plane normal to y-axis for 95D model.

Fig. 10. Modified hub shape.

Fig. 11. Distribution of flow velocity vectors on crosssectional plane normal to y-axis.

Fig. 12. Comparison of (a)95D model & (b)modified model.

Fig. 14. Comparison of the scroll housing.

Fig. 15. Distribution of velocity on the cross-sectional plane normal to z-axis.

Fig. 16. Effect of enlarging cut-off clearance.^[8]

Fig. 17. Fan performance tester.

Fig. 18. Comparison of measured P-Q curve & predicted VFR.

Fig. 19. Experiment setup for noise measurement.

Fig. 20. Comparison of original model & modified model.

Fig. 9. Distribution of velocity on cross-sectional plane normal to z-axis for 95D model.

Fig. 13. Distribution of velocity vectors on the crosssectional plane normal to x-axis.

Table 1. Design constraint of target centrifugal fan unit.

Table 2. Result of numerical analysis.

Table 3. Comparison of projected area ratio.

Table 4. Comparison of the normalized cut-off clearance.

Table 5. Result of numerical analysis.

Table 6. Measurement equipment.