3B Scientific Stirling Engine G User Manual

3B SCIENTIFIC

Instruction Sheet

02/11 ALF

1. Safety instructions

®

PHYSICS

Stirling Engine G U10050

1 Flywheel with marking for

speed determination

2 Motor-generator unit with

2-stage pulley
3 Switch
4 Bulb
5 4-mm safety plugs
6 Alcohol burner
7 Temperature measure-

ment connector 1
8 Displacement piston
9 Capped hose connection

for pressure measure-

ments
10 Temperature measure-

ment connector 2
11 Working piston
12 Threaded rod M3 (con-

nected with the working

piston)

2. Description

• Pour the fuel alcohol carefully into the alco-

holburner, making sure that none of it is spilt.

• Never fill the alcoholburner as long the wick is

still smoldering or another open flame is in close
proximity.

• Immediately close the fuel container after use.

• Keep away from the open flame.

• Caution! Only extinguish the flame by fitting the

cover provided for this purpose.

The Stirling engine becomes hot when it is operated
with an open flame.

• Do not touch the displacement cylinder during

or immediately after operation of the Stirling
motor.

• Allow the Stirling engine to cool before putting it

away.

The Stirling engine can be used for qualitative and
quantitative investigations of the Stirling cycle.and
can be operated in three different modes: heat en­gine, heat pump and refrigerator.

The displacement cylinder and piston are made of
heat-resistant glass; the working cylinder, flywheel
and transmission covers are made of acrylic glass.
This allows a very clear observation of the individual
motion sequences at all times. The crankshafts are
equipped with ball bearings and made of hardened
steel. The connecting rods consist of wear-resistant
plastic.

The integrated motor-generator unit with a 2-stage pul­ley allows the generated mechanical energy to be con­verted into electrical energy. A switchover mechanism
permits operation of an integrated lamp or external
loads, as well as a feeding of electrical energy in order to
simulate a heat pump or refrigerator.

By attaching the thin cord supplied with the appara­tus to the threaded rod on the work piston, the
stroke length can be measured.

1

3. Technical data

5. Operation

Motor-generator unit: max. 12 V DC

2-stage pulley: 30 mm dia., 19 mm dia.

Working piston: 25 mm dia.

Path of working piston: 24 mm

25 mm

Volumetric change: 24 mm

⎛⎞
⎜⎟

2

⎝⎠

⋅π=

12 cm

Minimum volume: 32 cm³

Maximum volume: 44 cm³

Power of the Stirling motor: 1 W approx.
Dimensions: 300x220x160 mm³ approx.

Weight: 1.65 kg approx.

4. Functioning principle

An ideal Stirling cycle has 4 phases (refer to Fig. 1):
Phase 1: Isothermal change of state, during which

the air expands at constant temperature.

Phase 2: Isochoric change of state, during which the

air cools at constant volume in the regene­rator.

Phase 3: Isothermal change of state, during which

the air is compressed at constant tempera­ture.

Phase 4: Isochoric change of state, during which the

air in the regenerator is heated back to its
initial temperature.

The process that takes place in the Stirling engine
only approximates to such an ideal cycle because in
fact the four phases overlap. Gas changes from hot to
cold while the expansion is still taking place and not
all the air will yet be in the colder part of the engine
while the compression phase is occurring.

5.1 The Stirling Engine as a heat engine

• Fill the methylated-spirit burner, place it in the

recess in the base-plate, twist out about 1-2 mm
of the wick, and ignite it.

• Move the displacer piston to its farthest-back

3

position, and after a short heating-up time
(about 1-2 minutes) push the flywheel gently in
the clockwise direction (as seen from the motor­generator unit) to set it turning (see Fig. 2).

• If necessary, adjust the tension of the drive belt

by moving the motor-generator unit.

• Turn on the filament lamp by moving the switch

to the “up” position.

• Alternatively, connect an external load through

the 4 mm sockets and drive it by moving the
switch to the “down” position.

Speed without a load: 1000 rpm approx.

Speed with a generator as the load: 650 rpm approx.

Generator voltage: 6 V DC approx.

Pressure difference: +250 hPa / -150 hPa

5.2 The Stirling motor as a heat pump or refrig­erator

Additional instruments needed:

DC Power supply 15 V, 1.5 A U8521121-230
or
DC Power supply 15 V, 1.5 A U8521121-115

Digital thermometer U11818

• Insert temperature sensors into the thermome-

ter sockets and connect them to a measuring in­strument (see fig. 3).

• Connect a DC voltage source through the 4 mm

sockets.

• Adjust the voltage (maximum 12 V) and operate

the Stirling engine with the switch in the “down”
position.

• Observe the increase or reduction in tempera-

ture.

In the refrigerator mode of operation, the flywheeI
rotates in the clockwise direction (as seen from the
motor-generator unit), whereas in the heat pump
mode it rotates in the anticlockwise direction.

Fig. 1 Functioning principle

(A: Displacement piston, B: Working piston)

• To switch between the two modes of operation,

reverse the polarity of the connections.

Pressure difference: +250 hPa / -150 hPa

Motor voltage: 9 V

Speed: 600 rpm

Temperature difference (with respect to 21° C):

Refrigerator: -4 K (reservoir: +6 K)
Heat pump: +13 K (reservoir: -1 K)

2