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Power Electronics Integration_ Packaging and Thermal

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									Analysis of the effects of different types of
  loads on a Thermo-Acoustic Engine

   Chitta Saha, Paul Riley and Mark Johnson
       Presentation Outline


- Construction of the tested Thermo-acoustic
Engine (TAE)

- Design issues of the low cost Alternator

- Different electrical loads with the TAE

- Power analysis for different load conditions

- Measured results

- Conclusions
            Propane Burner TAE

• TAE consists of                    Radiator

 - Stainless steel bulge (HHX)
 - 30 layers stainless steel wire   Hot buffer
mesh regenerator ( 95 µm, 250 µm)     tube
 - Car radiator (AHX)                                         Bulge
                                                 Insulation


• 5.5 kW propane burner, 4
inch pipe and B & C 6PS38
speaker.

•Each engine could be
connected in series/parallel
or independently.
    Requirements of LA for SCORE
              project

• Alternator design : low cost ( £4/unit )
high efficiency and resonant frequency
operation.

• Ultimate goals
   - Supply 12 V lead acid battery.
   - Generate 150 W dc power

• Small magnet constrains : (BL)2/Rc

• Meet the output power and cost :
frequency & displacement
    Limitations of Commercial low
          cost loudspeakers

• High suspension loss
and limited mechanical
stability.
                                        Front
                                        suspension

• Operate over a large                                         Cone
frequency range, LA
needs to operate a fixed   Rear                      Yoke pole pieces
frequency.                 suspension
                                                      Voice Coil



                                                          Magnet
• Lower efficiency and
larger weight.                                          Vent holes


                             Schematic of a loudspeaker type
                                       alternator
SCORE Alternator : Halbach array


• Alternator can be constructed
without back iron material, no
yoke piece is required.

• Smaller pumping loss due to
large hole.

• High Efficiency and high air-
gap reversal flux density.
    Performance of Alternator
          with Battery

• Battery with rectifier circuit :

• Electrical efficiency for dual coils : 80 % for 125 W when
Vbattery/Vp = 0.73, 76 % for 150 W when Vbattery/Vp=0.7

 • Max. power : Vbattery/Vp = 0.39
                                                 W
                                             L
                                             M
                                             N

                                              Double coil case   2 mm height 10 coils case
Tested prototype : Halbach array

• Measured and simulated voltages
agree well.

• Discrepancy between measured
and calculated efficiency appears
due to cracking in the suspension.
        Alternator power analysis

- Resistive load, source power and load power :




-Battery load can be considered as a RC load
when C becomes very large.
- Source power and load power for battery
rectifier circuit
           Measured results

• Pressure and temperature has been
measured using NI DAQ module.
• Voltage and power has been measured
using PPA2530.
• Electrical power is almost proportionally
varied with the square pressure.
  Loads effect on a Thermo-Acoustic
                Engine

• Bridge rectifier required a fixed load resistance to
generate the same amount of real power with battery.

• No effect on pressure and temperature when the real
power is constant.
   Load Condition               TAE parameters                                      Alternator
                     HHX (oC)    HHX- AHX        Pressure   Ac voltage   Ac power   Total      Idc (A)   Load power* (W)
                                   (oC)           (mBar)      (Vrms)       (W)      power    (Into 12V
                                                                                     (VA)    lead acid
                                                                                              battery)

    12 V battery +     413          347            38         13.12        8.96     11.35        0.43         5.59
     capacitor +
       rectifier
   Capacitor + 30      411          346            39         13.57        8.89     11.36        0.49         6.85
   Ω resistance +
       rectifier
   20 Ω resistance     403          343            37         13.2         8.65      8.65         -           8.65




• Load power is less than generated power due to losses in
the rectifier.
            Conclusions

• The construction of dual loop 30 layers stainless steel
regenerator SCORE TAE is introduced.

• Design issues of SCORE LA and advantages of double
Halbach array are discussed.

• Voltage/power measurement issues of the alternator
with linear and non-linear load with the full wave rectifier
circuit are discussed.

• Variations of the measured pressure and temperature of
the engine as well as electrical power are shown.

• Measured results show, no effect on the pressure and
temperature with the changing the load condition.
            Acknowledgment
The Score project www.score.uk.com is funded by
EPSRC, the UK Engineering and Physical Research
Council.
     Specification of the regenerator
Wire diameter                  95 um
Wire spacing                  250 um
Volumetric Porosity: σ         0.783
Solid fraction: (1-σ)          0.217
Hydraulic radius               86 um
Regenerator width             155 mm
Regenerator length            180 mm
Regenerator thickness          9 mm
         General power/losses summary of the system
                                                                    1807.39
Burner (net power)   4657.71 W   Rejected Heat
                                                                       W
Engine housing
                     519.24 W    Acoustic power (Heat)              460.65 W
losses
Heat to the Pans     1170.69 W   Electricity power                   15 W
Chimney losses        430.00 W   Stove efficiency                   25.13%
                                 TAE Efficiency (Heat to Acoustic
Heat to the TAE      2537.78 W                                      18.15%
                                 power(Heat))
                                 TAE and Generator Efficiency
TBT losses           269.74 W    (Acoustic power (Heat) to           3.2%
                                 Electrical power)

								
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