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<a href="../frame_links/index.html">CTM</a>
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<center>
<h1>Engine Research</h1>
</center>
Engine research is one essential tool to improve the performance of engines
without wasting a lot of time using the try & error method. Dr.Gordon
P. Blair f.e. (Lothar call him "Two Stroke Pope") is one who shows how to
do engine research in the best possible manner.<br>
<br>
A special situation for control line combat model engine builders was caused
in 1988 after the CIAM introduced the first rule into the international
control line combat reglement which should only reduce the power output
of the engines. The power of the current engines was considerably reduced,
but also the power difference between engines of the same and different
types were increased. This situation and Lothars bad experience with his
first homebuilt engine, which was built in 1989 according to the current
rules initiated the big wish to get the knowledge about what is really going
on inside our engines. He decided to make in-cylinder and crankcase pressure
measurements in his final work at the Fachhochschule München to get
the degree of a Diplom Ingenieur.<br>
The title of this work was:<br>
<br>
<div align="Center"><big><big>Pressure Measurements In Cylinder And Crankcase
Of</big></big><big><big> High Speed Small Capacity Two Stroke Engines</big></big><br>
</div>
<br>
The engine test bench on which this work was done is shown in the picture
below. It shows the arrangement of Lothars homebuilt HLM-V-1 engine, the
special torsional coupling shaft and the starter and brake-dynamometer brushless
motor.<br>
<br>
<br>
<center><img src="Pruefstand2-.jpg" border="0" alt="Prüfstand Lothars Diplomarbeit">
</center>
<br>
<u><big><br>
</big></u><br>
The engines shown on the pictures below were used to make the in-cylinder
and crankcase pressure measurements.<br>
Engines fitting the requirements of the reglement of the international
control line combat competition events are high speed internal combustion
two stroke engines with a swept volume of 2.5 cm<small><small>^3</small></small>
and an intake restrictor of 4 mm diameter. The methanol based fuel must
contain 20% castor oil and 10% nitromethane. No silencing devices were required
at this time.<br>
<br>
<table>
<tbody>
<tr>
<td width="220">
<center><img src="HLM-V1.jpg" width="200" border="0" alt="Motor HLM-V1">
</center>
</td>
<td width="220">
<center><img src="CTM-IIb-.jpg" width="200" border="0" alt="Motor CTM-IIb">
</center>
</td>
<td width="220">
<center><img src="Mockba-.jpg" width="200" border="0" alt="Motor Mockba">
</center>
</td>
</tr>
<tr>
<td>
<center>HLM-V1</center>
<center>Lothars homebuilt engine</center>
<center>for test purposes only</center>
</td>
<td>
<center>CTM-IIb</center>
<center>Jonny Dübells famous</center>
<center>selfmade combat engine</center>
</td>
<td>
<center>Mockba</center>
<center>russian combat engine</center>
<center>(no ring-screw head)</center>
</td>
</tr>
</tbody>
</table>
<br>
<br>
<br>
<u><big>A short overview about the results of this work is shown below:</big></u><br>
<br>
Fig. 1 shows the crankcase pressure versus crank angle over five revolutions
at an engine speed of 25200/min. Zero deg. crank angle indicates TDC. We
can see pressure fluctuations which are very repetitive with every revolution
and are therefore no error signals from the pressure transducer. After transfer
port opens at 118 deg. crank angle we can recognise a backflow of exhaust
gas into the transfer ports.<br>
<br>
<div align="Center">
<center><img src="Mockba-KD-04.jpg" alt="Kurbelgehäusedruckverläufe-Mockba" border="1">
</center>
Fig. 1: Crankcase pressure versus crank angle<br>
</div>
<br>
<br>
<br>
In Fig. 2 we can see the crankcase pressure (average of 10 revolutions)
in green, the motored, TDC-symmetric (blue) and three fired in-cylinder pressure
measurements (light blue, purpur and dark blue).<br>
<br>
<div align="Center">
<center><img src="Mockba-04alle.jpg" alt="Zweitaktprozess-Mockba" border="1">
</center>
Fig. 2: Crankcase and cylinder pressures versus crank angle<br>
</div>
<br>
<br>
<div align="Center">
<center><img src="Mockba-PV-10.jpg" alt="PV-Diagramm-Mockba" border="1">
</center>
Fig. 3: Cylinder pressure versus stroke<br>
</div>
<br>
<br>
<br>
The cylinder pressure measurement over six revolutions is shown in Fig.
4. The heat release rate calculated from this pressure reading is shown in
Fig.5. The calculation of the heat release rate is very sensitive at low pressure
differentials which results in high signal noises during compression and
expansion stroke. The colour of the curves between pressure measurement and
heat release rate refers to each other.<br>
<br>
<div align="Center">
<center><img src="HLM-BD-1-6-04.jpg" alt="HLM-Brennraumdruckverlauf1-6-04" border="1" width="640" height="350">
</center>
Fig. 4: Cylinder pressures versus crank angle ( fired condition)<br>
</div>
<br>
<br>
<div align="Center">
<center><img src="HLM-BV-04.jpg" alt="HLM-Brennverlauf1-6-04" width="640" height="350" border="1">
</center>
Fig. 5: heat release rate versus crank angle<br>
</div>
<br>
<br>
<br>
The Diagramm of Fig. 6 shows crankcase and cylinder pressure readings of
an Irvine .15 at different conditions:<br>
(This Irvine .15 had no intake restriction and the timing was optimised
for operation with a tuned pipe; all graphs show the average of several revolutions)<br>
Green graph: crankcase pressure, motored condition at 12763/min<br>
Red graph: cylinder pressure, motored condition at 12763/min<br>
Dark blue graph: crankcase pressure, fired condition at 23750/min without
tuned pipe<br>
Purpur graph: cylinder pressure, fired condition at 23750/min without tuned
pipe<br>
Blue graph: crankcase pressure, fired condition at 36154/min with tuned
pipe<br>
Light blue graph: cylinder pressure, fired condition at 33400/min with
tuned pipe<br>
<br>
<div align="Center">
<center><img src="Irvine-020308.jpg" alt="Zweitaktprozess-Irvine" border="1">
</center>
Fig. 6: Crankcase and cylinder pressure versus crank angle<br>
</div>
<br>
<br>
<br>
Fig. 7 shows the heat release rate calculated from the above pressure reading
(light blue graph) at 33400/min with tuned pipe.<br>
<br>
<div align="Center">
<center><img src="Irvine-BV-08.jpg" alt="Brennverlauf-Irvine" border="1">
</center>
Fig. 7: heat release rate versus crank angle<br>
</div>
<br>
<br>
engine research, motorentechnik, engine, engines, research, motor, motoren, technik, forschung, fesselflug,modellflug,f2d,combat,f2dcombat,control line, tuning,verbrennung, verbrennungs, verbrennungsmotoren, zweitakt
<hr><a href="mailto:lothar@control-line-team.de?subject=CTM%28Motorenpruefstand%29:">
(email lothar)</a>
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