Abstract:
A portable aeroacoustic wind tunnel includes a modular building structure. The wind tunnel is assembled together on-site at an assembly plant outdoors and on the ground and disassembled into sub-assemblies for transportation. A separate control building includes fan controls, acoustic measurement controls and windows for visual observation. A portable generator provides power to the wind tunnel that is equipped with acoustic dampening features. The modular building structure and control building can be shipped in a cost-effective manner.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application Ser. No. 62/319,437 filed Apr. 7, 2016, the disclosure of which is hereby incorporated in its entirety by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates to a portable apparatus for studying noise generation via aerodynamic forces interacting with surfaces of a vehicle. 
       BACKGROUND 
       [0003]    Vehicles are tested for wind noise issues that are important to providing a quality driving experience. Identifying wind noise issues early in a vehicle launch reduces the need to correct issues after vehicles are assembled and reduces the cost of corrective measures. 
         [0004]    At an assembly plant when a new vehicle is launched one or more vehicles are shipped to an offsite aeroacoustic wind tunnel to test the vehicles and identify the root cause of any wind noise issues. Shipping vehicles to an offsite wind tunnel is time consuming and expensive. Vehicles produced during the time that the vehicles are shipped and tested may require expensive remedial measures to eliminate the wind noise issues. 
         [0005]    Another approach to identifying wind noise issues is to drive the vehicles on the road. Evaluating wind noise performance on the road is difficult because of variable environmental factors and it may be difficult to locate a public road with little traffic near the assembly plant that is suitable for testing at highway driving speeds. 
         [0006]    This disclosure is directed to solving the above problems and other problems as summarized below. 
       SUMMARY 
       [0007]    The problem of identifying wind noise issues during a vehicle launch at an assembly plant is addressed by providing a portable aeroacoustic wind tunnel. The portable wind tunnel is designed to be assembled at the assembly plant in one or two days to conduct tests and disassembled after the wind noise issues are identified and corrected. The portable aeroacoustic wind tunnel may then be shipped to the next assembly plant undergoing a new vehicle launch. The portable aeroacoustic wind tunnel reduces the response time for testing for a wind noise issue from 3 to 14 days to a few hours. The time and cost savings make it feasible to increase the vehicle sample size for a series of tests from 3 to 5 vehicles to more than 10 vehicles. 
         [0008]    The structure of the portable aeroacoustic wind tunnel includes a two part modular building structure that is disassembled into sub-assemblies. In addition, a separate control building is provided that includes fan controls, acoustic measurement controls and windows for visual observation. If a convenient source of power from the electrical power grid is not available, a portable generator may be used that is provided with acoustic dampening. The modular building structure and control building can be shipped in a cost-effective manner on three flatbed trucks. 
         [0009]    The modules are assembled together onsite to create an acoustically conditioned single pass wind tunnel. The single pass wind tunnel creates a large volume of air flow that is directed toward a vehicle parked behind a nozzle. The air flow from the wind tunnel aggravates potential wind noise issues when directed at the front of a vehicle. Air flow speed measured at 125 feet behind the nozzle must be reduced to less than 65 kph. 
         [0010]    The portable aeroacoustic wind tunnel includes one or more fans that are powered by either a 500 kw portable generator or by connection to a power grid circuit that is capable of providing 800 Amps. 
         [0011]    The portable aeroacoustic wind tunnel includes a visual and audible warning system to warn persons in the area around the portable aeroacoustic wind tunnel of the high speed air flow. 
         [0012]    According to one aspect of this disclosure, a portable aeroacoustic wind tunnel system is provided that includes a first wind tunnel module, a second wind tunnel module that is configured to be assembled to the first wind tunnel module, and a control building. The wind tunnel modules and the control building are independently transportable to be temporarily installed outdoors on the premises of a vehicle assembly plant. 
         [0013]    Other features of the wind tunnel include a nozzle defining a discharge opening of at least 50 square feet that provides air flow through the nozzle at speeds of up to 130 kph. The wind tunnel modules may be installed on an asphalt or gravel surface having less than a 1% grade. The vehicle may be positioned on the ground behind a discharge opening defined by the nozzle. The vehicle may be angularly oriented to simulate yaw angles of ±10°. 
         [0014]    The background noise from the wind tunnel and power sources as measured in the vehicle disposed behind the nozzle is more than 6 decibels less than the wind noise to be measured in the vehicle while the wind tunnel is creating a 130 kph stream of air from the nozzle. The wind tunnel background noise generated while producing a 130 kph stream of air as measured 2 meters downstream of the exit nozzle with no vehicle in the air stream is less than 82 dB at 125 Hz, 75 dB at 250 HZ, 71 dB at 500 Hz, 61 dB at 2000 Hz, and 66 dB at 4000 Hz. 
         [0015]    The system may further comprise one or more fans and the control building is electrically connected to the wind tunnel modules to control the fan or fans. The control building may further comprise at least one window and is positioned for visually observing a vehicle through the window during testing. The system may also further comprise a portable generator that is electrically connected to the control building and the fan to provide power for the fan and the control building. 
         [0016]    According to another aspect of this disclosure, a method is disclosed for testing a vehicle for wind noise with an open circuit aeroacoustic wind tunnel formed in at least two modules and a control building. The method comprises the steps of assembling the two modules together and positioning the control building adjacent the wind tunnel outdoors on the premises of a vehicle assembly plant. The vehicle to be tested is positioned behind a discharge nozzle of the wind tunnel that blows air on a vehicle equipped with a microphone. 
         [0017]    According to other aspects of this disclosure, the method may further include the step of disassembling the two modules for transportation to a second vehicle assembly plant. The method may further comprise the step of separately transporting the two modules and the control building on separate transport vehicles to the vehicle assembly plant. The method may be used with a wind tunnel that includes at least one fan and may further comprise the steps of providing a portable generator, and connecting the portable generator electrically to the fans. 
         [0018]    The above aspects of this disclosure and other aspects are described below with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a side elevation view of a portable wind tunnel module in a control building on a flatbed truck. 
           [0020]      FIG. 2  is a front perspective view of a portable areoacoustic wind tunnel and control building set up on the ground at a vehicle assembly plant. 
           [0021]      FIG. 3  is a rear perspective view of the portable aeroacoustic wind tunnel and control building. 
           [0022]      FIG. 4  is a side elevation view of the portable aeroacoustic wind tunnel with a test vehicle in position. 
           [0023]      FIG. 5  is a top plan view of the portable aeroacoustic wind tunnel with the test vehicle in position. 
           [0024]      FIG. 6  is a side elevation view of a power generator disposed on a transport vehicle. 
           [0025]      FIG. 7  is a wiring diagram for powering the fans of the portable aeroacoustic wind tunnel from a power generator. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The illustrated embodiments are disclosed with reference to the drawings. However, it is to be understood that the disclosed embodiments are intended to be merely examples that may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed are not to be interpreted as limiting, but as a representative basis for teaching one skilled in the art how to practice the disclosed concepts. 
         [0027]    Referring to  FIGS. 1-3 , a portable aeroacoustic wind tunnel  10  is illustrated in  FIGS. 2 and 3 . The portable aeroacoustic wind tunnel  10  includes a first wind tunnel module  12  and a second wind tunnel module  14  that are assembled together on opposite sides of a longitudinal plane. A crane  11  is illustrated in  FIG. 1  in position to lift a first portable wind tunnel module  12  onto or off of the flatbed truck  15 . A control building  16  is shown on a separate flatbed trailer attached to the flatbed truck  15 . 
         [0028]    The portable aeroacoustic wind tunnel  10  is an open circuit airline wind tunnel that provides a flow of air from within the wind tunnel  10  to the outside without any recirculation of the air as is generally the practice with stationary wind tunnels used to test automotive vehicles. 
         [0029]    Referring to  FIG. 3 , the control building  16  is preferably oriented with an observation area overlooking a test vehicle  20  through one or more windows  28 . The control building  16  includes a controller that monitors inputs from one or more microphones  29  in the vehicle  20 . The control building  16  also includes the controls for the fans  36  in the wind tunnel  10 . The test vehicle  20  may be set up to directly face the discharge opening  26  at a yaw angle of 0°. Alternatively, the test vehicle  20  may be set up at an angle relative to the discharge opening  26  to simulate yaw angles of up to 10° and thereby simulate the vehicle traveling through a curve. The control building  16  is preferably connected to the test vehicle  20  and microphones  29  by a digital cable. A test technician may also be seated in the test vehicle  20  to listen for wind noises. 
         [0030]    With continued reference to  FIG. 3 , the portable aeroacoustic wind tunnel  10  is again shown, but from the back end, with the test vehicle  20  in position for testing. The first and second wind tunnel modules  12  and  14  are disposed on an asphalt or gravel surface  22 . It should be understood that, due to the weight of the modules, there is no need to provide a footer or foundation for the portable acoustic wind tunnel  10 . Setting up the wind tunnel directly on an asphalt or gravel surface having a slope of less than 1° saves considerable cost. For convenience, the portable aeroacoustic wind tunnel  10  is intended to be set up on the grounds of a vehicle assembly plant  24  so that the vehicles may be taken directly from the vehicle assembly plant  24  and positioned behind the discharge opening  26  of the wind tunnel  10  for wind noise testing. 
         [0031]    Referring to  FIGS. 4 and 5 , the portable aeroacoustic wind tunnel  10  is shown to include the first wind tunnel module  12  and second wind tunnel module  14  that are secured together with a test vehicle  20  disposed behind a discharge opening  26  in the assembled portable wind tunnel  10 . The wind tunnel  10  includes an inlet  30  through which air is drawn into the wind tunnel  10 . Air flowing through the wind tunnel  10  is represented by air flow arrow “A”. 
         [0032]    The inlet  30  is located at the front end  32  of the portable aeroacoustic wind tunnel  10 . A plurality of inlet baffles  34  are provided at the front end  32  inside the inlet  30  for the purpose of reducing noise emitted from the front end  32 . Two 250 horsepower fans  36  are arranged downstream from the inlet  30  and are secured within the wind tunnel  10 . One of the fans  36  is provided in each of the first and second wind tunnel modules  12  and  14 . A fan shroud  38  prevents the circulation of air flow around the fans  36 . A plurality of downstream baffles  40  are disposed between the fans  36  and a plurality of exit baffles  42 . The baffles  34 ,  40  and  42  may be formed from perforated aluminum sheets and filled with fiberglass. The perforated aluminum sheets filled with fiberglass reduce noise emitted through the discharge opening  26  from the fans  36 . 
         [0033]    Air flowing through the exit baffles  42  enters a nozzle  44  that has tapered walls leading to the 50 square foot discharge opening  26 . Air flowing from the nozzle  44  into the discharge opening  26  is directed toward the test vehicle  20 . The test vehicle  20  is preferably provided with a microphone  29  or an acoustic head of a test mannequin that may include several microphones. The output from several microphones  29  facilitates determining the location of wind noise in the test vehicle  20 . 
         [0034]    Referring to  FIG. 6 , a portable generator  50  is illustrated that is disposed on a flatbed truck  15 . The portable generator  50  is preferably a 500 kw generator that is housed in an enclosed trailer. The trailer housing the generator is preferably provided with acoustic noise dampening features. The generator  50  is rated to provide about 800 amps of current. 
         [0035]    Referring to  FIG. 7 , a wiring diagram  52  is provided showing that electricity from the portable generator is fed from a 480 volt pad mounted 750 kva transformer. Alternatively, the power for the wind tunnel  10  may be provided from a 480 volt feed from the power grid. Power is provided through a fused disconnect  54  to provide power to the power receptacle  56  in the control building  16  (shown in  FIGS. 1-3 ). Power from the power receptacle  56  is provided to a power panel  58  and to a transformer  60  that converts the 480 volt, 30 kva to 208 Y/120 volt output. A circuit breaker  62  is also provided in the control building  16 . Power is provided from the control building to the variable fan drive (VFD)  64 . Power from the VFD  64  is provided to fan A and fan B through disconnect  66  and a thermal overload (O/L) relay  68 . Power is then provided to fan A and fan B  70  that correspond to the fans  36  shown in  FIGS. 4 and 5 . 
         [0036]    The portable aeroacoustic wind tunnel  10  is capable of providing air speeds at the discharge opening  26  of up to 130 kph. The portable aeroacoustic wind tunnel  10  is an open circuit air line wind tunnel that also may be referred to as a transportable aeroacoustic wind noise audit apparatus. The wind tunnel  10  is configured to be set up in two days or less and may be transported on three standard width flatbed trailers  15 . The portable aeroacoustic wind tunnel  10  is configured to be torn down in less than two days so that it may be shipped to different assembly plants to support vehicle launch operations. 
         [0037]    The portable aeroacoustic wind tunnel  10  is designed to meet specific background noise specifications stated in terms of noise generated while producing a 130 kph stream of air as measured 2 meters downstream of the exit nozzle with no vehicle in the air stream is in the vehicle disposed behind the nozzle is less than 82 dB at 125 Hz, 75 dB at 250 Hz, 71 dB at 500 Hz, 66 dB at 1000 Hz, 61 dB at 2000 Hz, and 66 dB at 4000 Hz. 
         [0038]    The background noise inside the vehicle must be 10 decibels less than the wind noise to be tested or measured in the car. Background noise is attenuated in the wind tunnel  10  and the power generator  50  to be reduced. 
         [0039]    The wind tunnel  10  may also be provided with a warning system including warning lights and audible alarms. The warning lights and audible alarms may be provided on the control room or on the wind tunnel  10  as appropriate. Barriers are preferably set up around the discharge opening  26  of the wind tunnel  10  as an added safety precaution due to the high speed wind created by the wind tunnel  10 . 
         [0040]    The embodiments described above are specific examples that do not describe all possible forms of the disclosure. The features of the illustrated embodiments may be combined to form further embodiments of the disclosed concepts. The words used in the specification are words of description rather than limitation. The scope of the following claims is broader than the specifically disclosed embodiments and also includes modifications of the illustrated embodiments.