Final report for WP4.3: Enhancement of design methods ... - Upwind

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For DLC 7.2 it has to be considered that the turbine is not yawing. Thus, the wind direction equals the yaw misalignment. Proposal for further misalignment studies For a study in between both approaches (exact and wind independent approach), the assumption that misalignment is independent of the wind bin but not the wind direction or that the misalignment is independent of the wind direction but not the wind bin would be conceivable. The advantage of such in between studies would be that the directional distributions for the wind and sea state setup would be at hand as already derived (in between) for the wind independent method. Thus, the study would mainly be a matter of computation and evaluation. 5.3.2 Extreme Load Analysis The extreme load analysis considers a reduced set of load cases for preliminary jacket design. Nevertheless, DLCs 6.1 and 6.2 are of high computational effort. Unfortunately, the effort is mandatory as DLC’s 6.1 and 6.2 are assumed to be the main design drivers for the jacket sub-structure. For all other DLCs proposed for preliminary jacket design (DLC 2.2; DLC 1.6; DLC 2.3) the IEC standard [69] states wind aligned with waves if both approach from the worst case direction regarding loads. Thus, no wind wave misalignment but two support structure orientations shall be analysed for those load cases. Statistical load extrapolation according to [30] is not considered in this section as it mainly affects RNA loads so is not considered necessary within the scope of preliminary jacket design. DLC 6.1a: Idling in storm - V = Vref - Turbulent 50-year-wind - 50 year sea state with embedded Hmax,50 wave - Wind misalignment +8 deg or -8 deg - 6 to 10 seeds per wind speed - Wind-wave misalignment - Two support structure orientations (0°; 45°) DLC 6.1a considers a turbine idling in 50-year storm conditions. Turbulent wind with a minimum longitudinal turbulence intensity of 11 % shall be considered in combination with at least 6 seeds for wind and sea states, according to the IEC standard. Wind-wave misalignment shall include site-specific values derived during fatigue analysis. During load case computation the influence of the aerodynamic wake model shall be investigated. Practically, using GH Bladed, this includes variation of the wake model in Bladed’s ‘Aerodynamic Control’ Panel between ‘Frozen Wake’ and ‘Dynamic Inflow’ and checks of the time series for occurrence of resonance generated by numerical uncertainties. DLC 6.2a: Idling in storm during grid loss - V = Vref - Grid loss (yaw inactive -> yaw misalignment) - Turbulent 50-year-wind - 50-year sea state with embedded Hmax,50 wave - Wind misalignment +8 deg or -8 deg - 6 to 10 seeds per wind speed - Wind-wave misalignment with maximum loads from DLC 6.1a - Support structure orientation with maximum loads from DLC 6.1a 56
DLC 6.2a considers a turbine idling in 50-year storm conditions during grid loss, meaning the yaw system is inactive, resulting in significant yaw misalignments. Thus, wind direction shall be considered misaligned to the rotor axis between 30 deg and 180 deg (in 30 deg steps). The remaining load case setup equals DLC 6.1a despite for the support structure orientation and the wind-wave misalignment. The support orientation shall be determined by the support orientation for DLC 6.1a that resulted in maximum loads. Accordingly, wind-wave misalignment shall account for those site-specific values that resulted in maximum loads for DLC 6.1a. Again, during load case computation, the influence of the aerodynamic wake model should be taken care of. DLC 2.2: Safety system fault - Vin < V < Vout ; Hs(V) ; Tp(V) - NTM model for turbulent wind - Wind bin width 2m/s - One Hs, Tp-combination per wind bin - Wind misalignment +8 deg or -8 deg - 6 to 10 seeds per wind bin - Wind and waves in line - Two support structure orientations (0°; 45°) The setup is comparable to DLC 1.2 in the step one fatigue analysis. For reason of preliminary jacket design, safety system fault computations may be limited to one significant pitch fault at high wind speeds (near cut-out). It is conservatively proposed to assume all blades turn to fine (with a reasonable average pitch rate such as 5 deg/s) until the safety system is activated again by reaching the safety system overspeed limit. DLC 1.6: Power production in 50-year sea state - 0.8 Vr; Vr; 1.2 Vr; Vout - NTM model for turbulent wind - 50 year sea state with embedded Hmax,50 wave - Wind misalignment +8 deg or -8 deg - 6 to 10 seeds per wind speed - Wind and waves in line - Two support structure orientations (0°; 45°) DLC 1.6 represents power production in turbulent wind conditions and a 50-year sea state. For conservative reason of preliminary jacket design, an embedded wave with a maximum 1-year wave height (Hmax,1) may be assumed. Furthermore, a minimum of 6 wind seeds shall be computed in combination with wind misalignment and seeds for sea states as described for DLC 1.2. DLC 2.3 (DLC 1.5 in GL standard [31]): Generator cut-out - Vr ± 2m/s and Vout ; Hs(V) ; Tp(V) - EOG1 - Rotor start position 0 – 90 deg (30 deg steps) - Generator cut-out at 3 time instants - Wind misalignment +8 deg or -8 deg - Wind and waves in line - Two support structure orientations (0°; 45°) DLC 2.3 represents a load situation of a turbine in power production during a one-year gust (EOG1) that looses the generator torque due to a generator cut-out from the grid. The grid loss shall be considered at the three time instants, lowest wind speed, highest gust acceleration, maximum wind speed (see GL 2005 57
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Project UpWind Contract No.: 019945
Page 3 and 4:
Acknowledgement The presented work
Page 5 and 6: Summary The overall aim of the UpWi
Page 7: Table of Contents Acknowledgement..
Page 10 and 11: Task 4.1 Integration of support str
Page 12 and 13: Sequential coupling The sequential
Page 14 and 15: analysis. In the new multibody code
Page 16 and 17: Figure 2.4: 2nd global bending mode
Page 18 and 19: 3.2 Comparison of deterministic loa
Page 20 and 21: Figure 3.5: Time series of axial fo
Page 22 and 23: • Time domain simulation in ADCoS
Page 24 and 25: • A supplementary load vector for
Page 26 and 27: The following results are found: Fi
Page 28 and 29: Figure 4.5: Output positions in the
Page 30 and 31: It is directly visible that there i
Page 32 and 33: ated eigenfrequency is shifted into
Page 34 and 35: Water levels For the calculation of
Page 36 and 37: guidelines for the inclusion of cli
Page 38 and 39: damaging if the frequency of the ex
Page 40 and 41: uncertain parameters carefully. Thr
Page 42 and 43: Table 5.3 shows annual reliability
Page 44 and 45: Steel substructure for offshore win
Page 46 and 47: Table 5.16 shows the required FDF v
Page 48 and 49: A Fracture Mechanical (FM) modellin
Page 50 and 51: Figure 5.4: Annual reliability indi
Page 52 and 53: Further, the effect of possible ins
Page 54 and 55: Rainflow evaluation The load cases
Page 58 and 59: Guideline, DLC 1.5). Furthermore, t
Page 60 and 61: Table 5.28: Output locations for da
Page 62 and 63: From these results it can be clearl
Page 64 and 65: Figure 5.11: Normalised DELs with v
Page 66 and 67: Figure 5.14 presents normalized DEL
Page 68 and 69: Figure 5.16: Output locations for e
Page 70 and 71: UPWIND WP4: Offshore Support Struct
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UPWIND WP4: Offshore Support Struct
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Final report for WP4.3: Enhancement of design methods ... - Upwind

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