EFFECTS OF ROTOR-NACELLE ASSEMBLY MODELS ON THE STRUCTURAL NATURAL FREQUENCIES AND SEISMIC RESPONSE OF OFFSHORE WIND TURBINE
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摘要: 转子-机舱组合体(Rotor-Nacelle Assembly, RNA)又称风机机头，常用的简化模型包括点质量(RNA_M)、偏心点质量(RNA_ME)、偏心点质量-转动惯量(RNA_MEJ)和刚性机舱-刚性叶片(RNA_RB)。该文基于NREL 5MW单桩式海上风机原型，使用Abaqus软件分别建立包含这四种RNA简化模型的风机模型，以刚性机舱-可变形叶片(RNA_FB)风机模型为基准，分析不同的RNA简化模型对风机结构特征频率和地震响应的影响。研究结果表明：对于只涉及支撑结构1阶模态的问题，四种简化RNA模型计算的频率均是准确可靠的；当涉及支撑结构的2阶模态或/和扭转模态时，应采用RNA_MEJ、RNA_RB或RNA_FB模型；当涉及支撑结构的更高阶模态时，应采用RNA_FB模型。对于风机结构地震响应分析，RNA_MEJ与RNA_RB模型计算的结构响应更准确，但它们的大多数结构响应峰值的最大相对偏差均超过了10%，在实际工程应用时应慎重使用这些RNA简化模型。
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关键词:
- 海上风机 /
- 单桩基础 /
- 转子-机舱组合体模型 /
- 特征频率 /
- 地震响应
Abstract: For the Rotor-nacelle assembly (RNA), which is also known as the head of wind turbine (WT), the frequently used simplified models mainly include point mass (RNA_M), point mass with eccentricity (RNA_ME), point mass with eccentricity and rotational inertia (RNA_MEJ) and rigid nacelle with rigid blades (RNA_RB). Based on the prototype of the NREL 5MW offshore wind turbine (OWT) with monopile foundation, Abaqus is adopted to establish WT models with these four simplified RNA models. Taking the elaborated RNA_FB WT model as the baseline, this paper analyzes the influences of these different simplified RNA models on the natural frequency and seismic response of the WT structure. The results show that for the problems involving only the 1st order mode of the supporting structure, the calculated frequency values of the four simplified RNA models are all accurate and reliable; The RNA_MEJ, RNA_RB or RNA_FB model should be used when the 2nd order mode or/and torsion mode of the supporting structure is involved; The RNA_FB model should be used when higher-order modes of the supporting structure are involved. For the seismic response analysis of WT structure, the structural responses calculated by the RNA_MEJ and RNA_RB models are more accurate, but the maximum relative deviation (RD) of the majority of their structural response peaks still exceeds 10%. Therefore, the simplified RNA models should be used cautiously in engineering application. -
图 1 NREL 5 MW单桩式海上风机原型和分析模型
Figure 1. Prototype and analysis model of NREL 5 MW OWT with monopile foundation
图 4 阻尼比1.5%的加速度反应谱Sa
Figure 4. Acceleration response spectrum Sa with damping ratio of 1.5%
图 5 不同机头模型的支撑结构特征频率的相对偏差
Figure 5. Relative deviation of natural frequencies of supporting structure with different RNA models
图 6 在FA方向输入地震动记录1时的风机结构响应
Figure 6. Wind turbine structure responses with ground motion record 1 input in FA direction
图 7 在SS方向输入地震动记录1时风机结构响应
Figure 7. Wind turbine structure responses with ground motion record 1 input in SS direction
图 8 风机结构地震响应峰值和不同机头模型的相对偏差
Figure 8. Seismic response peak of WT structure and relative deviation with different RNA models
图 9 风机结构地震响应最大相对偏差
注：下标t为塔顶；下标m为支撑结构泥面处
Figure 9. Maximum relative deviation of seismic responses of WT structure
表 1 NREL 5 MW海上风机模型基本参数
Table 1. Basic specifications of NREL 5 MW offshore wind turbine model
风力发电机组基本参数 额定功率 5 MW 叶轮直径、轮毂直径 126 m, 3 m 轮毂中心高程 90 m 切入、额定和切出风速 3 m/s, 11.4 m/s, 25 m/s 切入、额定转速 6.9 RPM, 12.1 RPM 轮毂中心水平外挑长度、主轴倾角、叶轮预锥角 5 m, 5°, 2.5° 叶轮质量 110 000 kg 机舱质量 240 000 kg 塔筒参数(海上) 塔底和塔顶标高 10 m, 87.6 m 塔底直径和壁厚；塔顶直径和壁厚 6 m, 0.027 m; 3.87 m, 0.019 m 等效密度ρ、弹性模量E、泊松比μ 8500 kg/m3, 210 GPa, 0.3 
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表 2 NREL 5 MW风机机头的质量特性
Table 2. Mass properties of RNA for NREL 5 MW WT
软件 RNA质量MRNA/t RNA质心CM/m RNA塔顶转动惯量JTT (Jxx, Jyy, Jzz,Jzx)/(×107 kg·m2) RNA质心转动惯量JCM (Jxx, Jyy, Jzz,Jzx)/(×107 kg·m2) NREL(ADAMS) 350.0 (−0.417, 0.000, 1.967) (4.505, 2.494, 2.548, −0.146) (4.370, 2.353, 2542, −0.174*) Abaqus 350.0 (−0.414, 0.000, 1.967) (4.503, 2.498, 2.551, −0.145) (4.367, 2.358, 2.547, −0.173) 注：表中质心位置坐标和转动惯量都是相对于塔顶坐标系；在Abaqus中，Jzx的正负号规定与ASAMS的相反，“*”表示推算得到。
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表 3 NREL 5 MW单桩式海上风机支撑结构的特征频率(固定)
Table 3. Natural frequencies of supporting structure of NREL 5 MW OWT with monopile foundation (Fixed)
序号 模态 FAST[21]/Hz Abaqus/Hz 相对偏差/(%) 1 FA1 0.279 0.271 −3.10 2 SS1 0.278 0.269 −2.57 3 FA2 2.422 2.305 −3.85 4 SS2 2.377 2.218 −5.90
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表 4 输入地震动
Table 4. Input ground motion
序号 编号 地震 记录分量 加速度反应谱最大值Sa,max/g 1 RSN962 Northridge-01 WAT180 1.644 2 RSN1768 Hector Mine BRS360 2.071 3 RSN4872 Chuetsu-oki, Japan 65053NS 1.730
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表 5 风机支撑结构的特征模态与频率
Table 5. Natural modes and frequencies of WT supporting structure
序号 模态 RNA_FB/Hz RNA_M/Hz RNA_ME/Hz RNA_MEJ/Hz RNA_RB/Hz 1 FA1 0.2383 0.2479 0.2411 0.2394 0.2392 2 SS1 0.2375 0.2479 0.2411 0.2379 0.2378 3 FA2 1.5737 1.7393 1.6872 1.4905 1.4761 4 SS2 1.3444a 1.7393 1.6875 1.3147 1.3285 5 FA3 4.1412a 4.6420 4.4831 4.4445a 4.5107a 6 SS3 4.2244a 4.6420 4.4881 4.2481a 4.2479a 7 FA4 9.1045a 9.3524 9.0696 10.7150 10.6990 8 SS4 9.3720a 9.3524 9.0449 10.6110 10.6110 9 FA5 13.7223a 14.9390 14.5460 16.2710 16.2620 10 SS5 14.6667a 14.9390 14.5380 16.2120 16.2120 11 ATR1 1.6745 11.4890 11.4820 1.3547 1.3880 12 ATC1 6.8059a 6.7181 6.7010 6.7296 6.7282 注：FA为风机前后向；SS为风机侧向；ATR为轴向扭转；ATC为轴向受拉或受压；MSIn为模态标识符，例如FA1，n为振动模态的阶数；“a”表示是多个衍生模态的平均特征频率。
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