Experimental study on heat dissipation through circulation in the hollow shaft of MW-class flywheel motor rotor

doi:10.19799/j.cnki.2095-4239.2025.0518

Abstract

Abstract:

Cooling the motor rotors in large-capacity flywheel energy storage systems operating in vacuum environments is a significant challenge. Aiming to reduce the temperature rise of the rotor, a 1.25 MW flywheel energy storage unit is proposed herein to provide an axial internal flow cooling scheme for the hollow shaft of the flywheel motor rotor. A mathematical model of the temperature field in the rotor shaft was developed by integrating heat conduction and convection equations. The predictions of the model reveal that in the absence of any cooling measures, the surface temperature of the rotor rises linearly with the operating time. However, with the proposed hollow shaft internal flow cooling scheme, the rotor temperature can be effectively stabilized, demonstrating the potential for controlling the temperature rise. To validate the feasibility and effectiveness of the proposed cooling scheme, an experimental platform was carefully designed and constructed. The hollow shaft internal flow cooling scheme is highly effective in curbing the temperature rise of the rotor. Detailed analysis shows that increasing the flow rate of the cooling medium (heat-transfer oil) leads to a significant enhancement in the cooling effectiveness. Further research shows that increasing the flow rate of the heat-transfer oil can enhance the heat dissipation effect, raising the rotational speed can effectively control the temperature rise of the rotor, and by increasing the heating power, the rate of the temperature rise can be controlled in a linear manner. This study provides a practical and effective solution to the pressing issue of rotor cooling in such systems.

Key words: flywheel energy storage system, motor rotor, hollow shaft cooling, convection heat transfer

CLC Number:

TK 02

Bowen LI, Xiankui WEN, Qiang FAN, Tingyun GU, Zhengjun SHI, Xiaoyin ZHANG. Experimental study on heat dissipation through circulation in the hollow shaft of MW-class flywheel motor rotor[J]. Energy Storage Science and Technology, 2025, 14(8): 2925-2931.

Figures/Tables 12

Fig. 1

Fig. 2

Fig. 3

Table 1

Axial internal flow heat transfer parameters"

尺寸参数	变量名	值/ $m m$	工况参数	变量名
导管内径、外径	$2 r i, 2 r o$	44.845, 47.803	入口流速	$u i n$
导管与中空轴顶距	$S$	63	入口温度	$T i n$
中空轴内径	$2 r f i$	100	转子轴转速	$n$
流道出口内径	$2 r f o$	59	转子发热量	$Φ$
转子直径	$2 R$	472	环境压力	$p 0$
转子高度	$H$	575

Table 1

Table 2

Material property parameters at 25 ℃"

物性参数	钢	硅钢片	导热油
密度/(kg/m³)	7850	7650	823.8
导热系数/[W/(m·K)]	44	35	0.1284
比热容/[J/(kg·K)]	460	500	1906.8
动力黏度/[ $k g / m · s$ ]	—	—	0.02812

Table 2

Fig. 4

Table 3

Table 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

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序号	类型	型号	量程	精度	位置
1	温度	红外温度传感器	0~200 ℃	±1 ℃	转子轴顶端、底端
2	温度	PT100热电阻	0~300 ℃	±0.1 ℃	油箱出口、导管入口
3	流量	涡街流量计	0~50 L/min	1.5%	导管入口
4	压力	ZJ-52T真空规管	0.1~10⁵Pa	25%	真空泵
5	转速	霍尔传感器	0~20 kHz	5%	转子轴顶测速齿盘

序号	腔内压力/Pa	转子轴转速/(r/min)	磁加热功率/W	导热油流量/(L/min)
1	7000	0	500	21
2	7000	300	500	21
3	7000	600	500	21
4	7000	900	500	21
5	7000	300	1000	21
6	7000	300	1500	21
7	7000	300	500	13
8	7000	300	500	17