On the Formation of Nitrogen Oxides During the Combustion of ...

C.2 Construction and Manufacturing Details
coil is positioned correctly, a symmetric pair of raw pipettes can be generated
this way, both of which can be used as fuel supply tubes later on.
• Both raw pipettes are cut to identical lengths with a simple glass cutter.
• Each raw pipette is finished with a microforge 1 to provide a well-defined
and sharp orifice diameter. The “cutting” function of the microforge is
used for this purpose, as pictured in Figure C.5. The raw pipette is positioned
with an overlap of 0.5 to 1.0mm over the glass bead, whose heater
temperature is initially set to zero. After the pipette is brought into contact
with the glass bead, the heater temperature is turned up slowly and
thermal expansion shifts the glass bead to the left (cf. Fig. C.5). Pipette
and glass bead start fusing. As soon as this fusing is observed, heating is
interrupted. By the loss of temperature, the glass bead moves back to the
right, and the pipette is separated at the fusing location [310].
• The orifice area of the final micropipette is determined by a metallurgical
microscope, since it is the decisive parameter for the pressure drop over
the orifice and, thus, for the volume of the generated droplet. As not all
glass tubes have an absolutely circular orifice, the major and minor axes
of the orifice are measured assuming an elliptical shape. The final orifice
area is typically in the range of 800 to 1000µm 2 .
C
B
D
ON
Heating
OFF
A
Figure C.5: Cutting of Micropipette with Microforge. This microscope image illustrates the
cutting process with the MF-900 microforge of NARISHIGE [310]. A: heatable filament,
B: glass bead, C: fused/cut-off piece of raw pipette, D: final micropipette.
1 All instruments and tools are made by NARISHIGE [310]. These are glass tubes of type G-100, puller PC-10, and
microforge MF-900.
221