Abstract:
A starting method is provided for a rotating machine which includes a main shaft, a main bearing rotatably supporting the main shaft and a main bearing lubricant pump circulating lubricant through the main bearing. The starting method includes steps of: rotating the main shaft to raise a temperature of the main bearing in a state in which the main bearing lubricant pump is not operated; and operating the main bearing lubricant pump to start supplying the lubricant to the main bearing after the step of raising the temperature of the main bearing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This is a continuation application of International Application No. PCT/JP2010/052534, filed on Feb. 19, 2010. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method of starting a rotating machine, and more particularly, to a method of starting a rotating machine, such as a wind turbine generator, disposed in a cold environment. 
         [0004]    2. Description of the Related Art 
         [0005]    Wind turbine generators are increasingly constructed across the globe in favor of promotion of use of renewable energy. It is therefore demanded to construct wind turbine generators even in a cold environment. 
         [0006]    One of issues necessary to be considered in constructing a wind turbine generator in a cold environment is that lubricant of a lubrication system is cooled when the wind turbine generator stops operating. When the lubricant is cooled after the wind turbine generator stops operating, the viscosity of the lubricant is increased, causing deterioration of the circularity of the lubricant. When the viscosity of the lubricant is excessively increased, load is imposed on equipment (such as a lubricant pump) constituting the lubrication system and pipes, potentially causing equipment malfunction or leakage of the lubricant. This problem is serious particularly when the wind turbine generator in an extremely cold environment is to be started. 
         [0007]    To solve such a problem, a heater that heats lubricant is generally provided in a wind turbine generator disposed in a cold environment. At the starting of the wind turbine generator is started, a lubricant pump is actuated to start the lubrication system, after the lubricant is heated by the heater. For example, US Patent Application Publication No. US2009/0191060A1 discloses a technique for providing a heater in a drain pipe discharging lubricant from a speed-up gear to a lubricant pump, thereby avoiding damages of the lubricant pump. 
         [0008]    According to study of the inventor of the present invention, however, the technique for supplying the heated lubricant is not always appropriate for a component, such as a main bearing, having a large heat capacity and a large contact area with the lubricant. The main bearing is cooled after the wind turbine generator stops operating. When the heated lubricant is supplied to the cooled main bearing, then the lubricant is instantly cooled to increase the viscosity of the lubricant, causing deterioration of the lubricant discharge efficiency. When lubricant of an amount exceeding the amount of lubricant dischargeable from the main bearing is supplied to the main bearing, leakage of the lubricant may occur. 
         [0009]    To provide a heater heating the main bearing may be an approach for avoiding the above-stated problem; however, the approach of providing the heater heating the main bearing suffers from problems of a larger heat capacity of the main bearing of the wind turbine generator, and inevitable heat transmission to the nacelle base, which has a large heat capacity. To heat the main bearing to a necessary temperature using the heater, it is necessary to provide a heater having a considerably large heating capacity and a considerably long heating time is required. In these circumstances, it may be impractical to heat the main bearing using a heater. The above-described problem also applies to other rotating machines including a bearing with a large heat capacity (for example, shield machines, printing machines and industrial machines such as power generator turbines). 
       SUMMARY OF INVENTION 
       [0010]    It is therefore an object of the present invention to provide a method of starting a rotating machine, such as a wind turbine generator, disposed in a cold environment, which method can deal with a problem of deterioration in lubricant discharge efficiency due to cooling of a main bearing. 
         [0011]    In an aspect of a present invention, a starting method is provided for a rotating machine which includes a main shaft, a main bearing rotatably supporting the main shaft and a main bearing lubricant pump circulating lubricant through the main bearing. The starting method includes steps of: rotating the main shaft to raise a temperature of the main bearing in a state in which the main bearing lubricant pump is not operated; and operating the main bearing lubricant pump to start supplying the lubricant to the main bearing after the step of raising the temperature of the main bearing. 
         [0012]    It is preferable that the number of rotations of the main shaft is controlled in the step of raising the temperature of the main bearing. It is also preferable that the main bearing is lubricated in an oil bath in rotating the main shaft to raise the temperature of the main bearing. 
         [0013]    In one embodiment, the temperature of the main bearing is measured using a temperature sensor in the step of raising the temperature of the main bearing, and the main bearing lubricant pump is operated in response to the temperature of the main bearing measured by the temperature sensor. 
         [0014]    In another aspect of the present invention, a starting method is provided for a rotating machine which includes a main shaft, a main bearing rotatably supporting the main shaft and a main bearing lubricant pump circulating lubricant through the main bearing, the starting method including steps of: rotating a main shaft and raising a temperature of a main bearing in a state in which lubricant is supplied to the main bearing at a first flow rate by using a main bearing lubricant pump; and supplying lubricant to the main bearing by using the main bearing lubricant pump at a second flow rate higher than the first flow rate. 
         [0015]    In still another aspect of the present invention, a starting method is provided for a wind turbine generator which includes a main shaft connected to a wind turbine rotor, a main bearing rotatably supporting the main shaft and a main bearing lubricant pump circulating lubricant through the main bearing. The starting method includes: steps of: rotating the main shaft to raise a temperature of the main bearing in a state in which the main bearing lubricant pump is not operated; and operating the main bearing lubricant pump to start supplying the lubricant to the main bearing after the step of raising the temperature of the main bearing. 
         [0016]    It is preferable that the number of rotations of the main shaft is controlled in the step of raising the temperature of the main bearing. The control of the number of rotations of the main shaft may be achieved by controlling a pitch angle of wind turbine blades of the wind turbine rotor or by controlling a generator torque of a generator driven by the main shaft. 
         [0017]    It is preferable that the main bearing is lubricated in an oil bath in rotating the main shaft to raise the temperature of the main bearing. 
         [0018]    In one embodiment, the temperature of the main bearing is measured using a temperature sensor in the step of raising the temperature of the main bearing, and the main bearing lubricant pump is operated in response to the temperature of the main bearing measured by the temperature sensor. 
         [0019]    In the starting method of the wind turbine generator, generation of electric power is started after a supply of the lubricant to the main bearing is started. 
         [0020]    In still another aspect of the present invention, a starting method of a wind turbine generator includes steps of: rotating a main shaft to raise a temperature of a main bearing in a state in which lubricant is supplied to the main bearing at a first flow rate by using a main bearing lubricant pump; and supplying lubricant to the main bearing by using the main bearing lubricant pump at a second flow rate higher than the first flow rate, after the step of raising the temperature of the main shaft. 
         [0021]    The present invention provides a starting method for dealing with the problem of deterioration in lubricant discharge efficiency due to cooling of the main bearing for a rotating machine, especially, a wind turbine generator, disposed in the cold environment. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0022]      FIG. 1  is a side view showing the configuration of a wind turbine generator in one embodiment of the present invention of the present invention; 
           [0023]      FIG. 2  is a top view showing the internal structure of a nacelle in one embodiment of the present invention; 
           [0024]      FIG. 3  is a conceptual diagram showing an example of the configuration of a lubricant circulating system supplying lubricant to a main bearing in one embodiment of the present invention; 
           [0025]      FIG. 4  is a block diagram showing a configuration of a control system of the wind turbine generator in one embodiment of the present invention; and 
           [0026]      FIG. 5  is a table showing a procedure of starting the wind turbine generator in one embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]      FIG. 1  is a side view showing a configuration of a wind turbine generator  1  in one embodiment of the present invention. The wind turbine generator  1  includes a tower  2  provided upright to a base  6 , a nacelle  3  disposed on the top of the tower  2 , a rotor head  4  provided rotatably to the nacelle  3 , and wind turbine blades  5  attached to the rotor head  4 . The rotor head  4  and the wind turbine blades  5  constitute a wind turbine rotor. 
         [0028]    As shown in  FIG. 2 , the rotor head  4  is connected to one end of a main shaft  11  which transmits power from the wind turbine rotor to a speed-up gear  13 , and the main shaft  11  is rotatably supported by a main shaft bearing  12  which is a rolling bearing. The other end of the main shaft  11  is connected to the input shaft of the speed-up gear  13 . The output shaft of the speed-up gear  13  is connected to the rotor of a generator  14 . When the rotor head  4  rotates by wind force, the rotation is transmitted to the rotor of the generator  14  to drive the generator  14  with the rotation speed increased by the speed-up gear  13 . As a result, electric power is obtained from the generator  14 . 
         [0029]      FIG. 3  is a block diagram showing the configuration of a lubricant circulating system which supplies the lubricant to the main bearing  12 . The lubricant circulating system in this embodiment includes a lubricant tank  21 , a main bearing lubricant pump  22 , a cooler  23 , and a bypass pipe  24 . The lubricant tank  21  is provided with a main bearing lubricant tank heater  25 . As described later, the main bearing lubricant tank heater  25  is used to heat the lubricant in the lubricant tank  21 . The main bearing lubricant pump  22  draws out the lubricant in the lubricant tank  21 , and supplies the lubricant to the main bearing  12  via the cooler  23  or the bypass pipe  24 . The cooler  23  cools the lubricant when the temperature of the lubricant is high. The outlet of the cooler  23  is connected to a lubricant inlet  12   a  of the main bearing  12 . The bypass pipe  24  bypasses the lubricant when the temperature of the lubricant is not high. Provided for the bypass pipe  24  is a temperature actuation valve  26  which is opened when the temperature of the lubricant is lower than a predetermined temperature. The bypass pipe  24  bypasses the lubricant by the operation of the temperature actuation valve  26 . Connected to a lubricant outlet  12   b  of the main bearing  12  is a drain pipe  27  which discharges the lubricant to the lubricant tank  21 . When the main bearing lubricant pump  22  operates, then the lubricant is drawn out from the lubricant tank  21 , supplied to the lubricant inlet  12   a  of the main bearing  12  via the cooler  23  or the bypass pipe  24 , and returned to the lubricant tank  21  from the lubricant outlet  12   b  through the discharge pipe  27 . It should be noted that the lubricant tank  21  and the main bearing lubricant tank heater  25  may be shared by a lubricant circulation system which circulates lubricant through an instrument other than the main bearing (for example, the speed-up gear  13 ). 
         [0030]    In this embodiment, as shown in  FIG. 3 , the lubricant outlet  12   b  of the main bearing  12  is provided at a position away from the lowermost portion of the main bearing  12 , and the main bearing  12  is configured to provide a lubricant reservoir  12   c  which accumulates the lubricant in the lower portion of the main bearing  12 . That is, the main bearing  12  is configured to be lubricated by oil bath lubrication to some extent even when the main bearing lubricant pump  22  is not operated. As described later, such a structure of the main bearing  12  contributes to improvement in the procedure of starting the wind turbine generator  1 . 
         [0031]      FIG. 4  is a block diagram showing an example of the configuration of a control system of the wind turbine generator  1 . Although  FIG. 4  shows only portions related to the present invention among those within the control system of the wind turbine generator  1 , the person skilled in the art would appreciate that various instruments are actually mounted in the wind turbine generator  1 . In this embodiment, a control device  30  controls the main bearing lubricant pump  22 , the main bearing lubricant tank heater  25 , a pitch control mechanism  31 , a hydraulic pump  32 , a speed-up gear lubricant pump  33 , and a speed-up gear heater  34 . The pitch control mechanism  31  adjusts the pitch angle of the wind turbine blades  5  of the wind turbine rotor. The hydraulic pump  32  supplies hydraulic pressure to the pitch control mechanism  31 . The control device  30  controls the pitch angle of the window turbine blades  5  using the pitch control mechanism  31 . The speed-up gear lubricant pump  33  circulates the lubricant to the speed-up gear  13 , and the speed-up gear heater  34  is provided in a lower portion of the speed-up gear  13  to heat the lubricant in the speed-up gear  13 . The lubricant lubricating the speed-up gear  13  is heated by the speed-up gear heater  34 . 
         [0032]    Furthermore, a main bearing temperature sensor  35  is provided for the main bearing  12 , and the control device  30  monitors the temperature of the main bearing  12  using the main bearing temperature sensor  35 . 
         [0033]    A description is next given of the outline of the procedures of starting the wind turbine generator  1  of this embodiment. 
         [0034]    One of important respects in the procedure of starting the wind turbine generator  1  in this embodiment is to heat the main bearing  12  by using heat generation caused by actuation of the main bearing  12  per se. Heat is generated in the main bearing  12  not only by rotation loss of the inner ring and rolling elements but also by sliding of an oil seal (not shown) sealing the lubricant of the main bearing  12  on the main shaft  12 . In this embodiment, the main shaft  11  is rotated at a low speed to generate heat in the main bearing  12  and to thereby heat the main bearing  12  in implementing a starting procedure of the wind turbine generator  1 . By actuating the main bearing lubricant pump  22  after sufficiently raising the temperature of the main bearing  12 , it is possible to solve the problem of the deterioration in lubricant discharge efficiency resulting from the cooling of the lubricant by the main bearing  12 , which causes an increase in the viscosity of the lubricant. 
         [0035]    In implementing the starting procedure described above, it is advantageous that the main bearing  12  is structured to accumulate the lubricant in the lower portion of the main bearing  12  to thereby allow oil bath lubrication to some extent, as described above. The oil bath lubrication avoids damaging the main bearing  12  due to the short of lubricant as long as the main shaft  12  rotates at a low speed. The inventor of the present invention has confirmed that an oil film can be formed by rotating the main shaft  11  at a low speed even at a low temperature of −40° C. 
         [0036]    In the following, the procedure of starting the wind turbine generator  1  in this embodiment will be described in detail.  FIG. 5  is a table showing an example of the procedure of starting the wind turbine generator  1 . It is assumed that the wind turbine generator  1  is completely stopped in an extremely cold environment (of, for example, −40° C.) in an initial state. That is, it is assumed that the main bearing lubricant pump  22 , the hydraulic pump  32 , and the speed-up gear lubricant pump  33  are stopped and that supply of power to the main bearing lubricant tank heater  25  and the speed-up gear heater  34  is stopped. In such a state, the lubricant in the lubricant tank  21  is completely cooled and the temperature of the main bearing  12  is very low. In this case, the wind turbine  5  is set in a feather state (the state in which the angle of attack is minimum) and the wind turbine rotor is set in a freely rotatable state (the state in which the brake of the wind turbine rotor is released). 
         [0037]    When the starting sequence is started by manually turning on an operation switch (not shown), for example, supply of power to the various heaters included in accessories starts. At the same time, supply of power to the main bearing lubricant tank heater  25  and the speed-up gear  34  also starts. The lubricants in the lubricant tank  21  and in the speed-up gear  13  thereby starts to be heated. 
         [0038]    After the lubricants in the speed-up gear  13  and the hydraulic pump  32  are sufficiently heated, the hydraulic pump  32  and the speed-up gear lubricant pump  33  start operating. By actuating the hydraulic pump  32 , the pitch control mechanism  31  is placed into a state in which the pitch control mechanism  31  can control the pitch of the wind turbine blades  5 . At this time, the temperature of the lubricant is kept to a desired temperature (10° C., for example) using the main bearing lubricant tank heater  25  and the speed-up gear heater  34 . 
         [0039]    Next, the pitch angle of the wind turbine blades  5  is switched by the pitch control mechanism  31  from the feature state to the pitch angle at which the wind turbine blades  5  can slightly receive wind power energy, thereby starting rotation of the wind turbine rotor. The main shaft  11  rotates by rotation of the wind turbine rotor, and the temperature of the main bearing  12  rises by heat generation in the main bearing  12  per se. It should be noted that the main bearing lubricant pump  22  is not started when the wind turbine rotor starts rotating. As described above, the main bearing  12  is lubricated by the oil bath to some extent even when the main bearing lubricant pump  22  does not operate. 
         [0040]    At this time, the number of rotations of the main shaft  11  is controlled not to be increased excessively. This aims to avoid a local and rapid increase of temperature, to reduce the risk of loss of control, including over speed, and to avoid the risk of damage of the main bearing  12 . Specifically, the pitch control is implemented for the wind turbine blades  5 , thereby controlling the number of rotations of the wind turbine rotor, that is, the number of rotations of the main shaft  11 . 
         [0041]    In one embodiment, the generator  14  is placed into a no-load state (that is, in a state in which a generator torque of the generator  14  is zero) while the wind turbine rotor rotates. However, the generator torque is not necessarily set to zero. Rather, the number of rotations of the main shaft  11  may be controlled by actively controlling the generator torque. In this case, the main shaft  11  and the wind turbine rotor may be rotated by causing the generator  14  to function as a motor. Also, both of the generator torque control and pitch angle control may be performed. 
         [0042]    When the main bearing  12  is heated up to an appropriate temperature (10° C., for example), the main bearing lubricant pump  22  starts operating. The wind turbine generator  1  is thereby placed into a standby state in which the wind turbine generator  1  is ready to start generating power. In one embodiment, the timing of starting the main bearing lubricant pump  22  is decided in response to the temperature of the main bearing  22  measured by the main bearing temperature sensor  35 . When the temperature of the main bearing  22  measured by the main bearing temperature sensor  35  exceeds a predetermined reference temperature, for example, the main bearing lubricant pump  22  starts operating. Alternatively, the main bearing lubricant pump  22  may start operating at the timing when a predetermined standby time elapses after the rotation of the wind turbine rotor is started. Even in this case, the main bearing lubricant pump  22  can start operating after the main bearing  12  is heated up to an appropriate temperature by appropriately setting the standby time. 
         [0043]    Thereafter, the main bearing lubricant pump  22  starts operating and then the wind turbine generator  1  starts generating power. 
         [0044]    The starting procedures stated above allows the main bearing  12  to be heated without providing a heater of a large capacity, avoiding the problem of the deterioration in the lubricant discharge efficiency for discharging the lubricant from the main bearing  12  at the time of starting the wind turbine generator  1  at a low temperature. 
         [0045]    In the starting procedure stated above, the main bearing lubricant pump  22  may be operated at a small number of rotations to supply the lubricant of a small amount to the main bearing  12  instead of stopping the main bearing lubricant pump  22  until the main bearing  12  is heated. In this case, there is no need to use the main bearing  12  that is structured to accumulate the lubricant in the lower portion of the main bearing  12  to be lubricated by the oil bath (it should be noted that a main bearing  12  structured to accumulate lubricant at the lower portion may be used). The flow rate of the lubricant supplied to the main bearing  12  before the completion of the heating of the main bearing  12  is adjusted to be lower than the flow rate of the lubricant supplied to the main bearing  12  after the wind turbine generator  1  is placed into the standby state (that is, the flow rate of the lubricant after the wind turbine generator  1  starts power generation operation), and adjusted to be low to avoid a leakage of the lubricant and a damage of the main bearing lubricant pump  22 . 
         [0046]    Also, the present invention may be applied to other rotating machines in which a main bearing that rotatably supports a main shaft has a large heat capacitance, although embodiments are described in which the present invention is applied to a wind turbine generator. For example, it is preferable that the present invention is applied to shield machines, printing machines and industrial machines such as power generator turbines.