
New technology progresses a step at a
time.
Internal Combustion Quasiturbine
(Otto, Diesel or Detonation)
are not yet disclosed
No unit is for sale at this time
Many readers are impatient to know more
about the IC Quasiturbine.
For this reason, an engine comparison methodology is presented here,
which could be adapted to individual potential reference piston engine.
THEORETICAL METHODOLOGY OF COMPARISON:
DIESEL PISTON ENGINE
VERSUS
DIESEL QUASITURBINE
Comparison Generalities
In any comparison, the Quasiturbine will not likely
simultaneously match the torque, the rpm and the power at its optimum
regime, in part because of the two different engine geometries, and
because of constraints related to combustion consideration (the Wankel nor
the conventional
gas turbine can match all piston characteristics at once). At
design, for the same power, a high torque QT has large diameter and short
thickness, while a higher rpm QT design has a smaller diameter and a
greater thickness (this is the QT "diameter to thickness ratio" analogue
to the piston crankshaft diameter). At this time we keep with the QT600
convenient diameter to thickness ratio.
For a simultaneous optimum operation match, no piston
combustion similarity constraints must be imposed and an appropriate QT
ratio should be selected at design. Let detail below two basis of
comparison:
A  Matching The Power
B  Matching the Combustion Conditions
C  Comparison Summary
Reference Diesel Engine
There is a vast choice of engines on the market which
could be referred to in the context of this theoretical comparison (which
is in no way intended to discredit any fine piston technology  Could
rather be an honor?). Because the powerful diesel engines are the most
critical to the industrial world, let's
pickup arbitrary the:
Caterpillar Turbo charge C15 15.2L HeavyDuty Engine
as described by the manufacturer at
http://ohe.cat.com/cda/layout?m=85523&x=7
http://ohe.cat.com/cda/files/209038/7/C15.pdf
Specifications:
4 stroke turbo 6 Cylinders InLine
Bore/Stroke 5.4 x 6.75 (137mm x 171mm)
Displacement 15.2 L (928 cu in)
Weight 2890 lb (1311 kg)
Horsepower 435 to 625 @ 2100 rpm
Torque 15502050 lbft @ 1200 rpm
For comparison, let's consider a single operation point approximated from the graph as
follow:
Torque 1600 lbft;
Revolution 1600 rpm;
Power 500 HP.
A  Matching the Power
Because both piston and QT are displacement
engines, a way to make a first approximation comparison is by matching the
displacement volume flow (power) within both types of engine.
Turbo Cat Flow = 0,5 x 15 liters displacement engine x 1600 rpm = 12000
liters/min
(0,5 because the 4 strokes piston takes 2 revolutions to intake the displacement
volume, it does intake 7,5 liters per revolution). Turbo Cat internal average
net added piston pressure can be estimated from the torque Net Added pressure =
torque / (1 piston surface x (3/2 simultaneous piston) x crankshaft radius) (ignore sine form
factor, about the same as QTSC).
Turbo Cat Net Added Pressure = 165 psi effective
Turbo QT600SC
As a guess, an equivalent combustion QT600SC
would theoretically give 3,3 lbft / psi
(this is the peak torque during a combustion to match the sine form factor
ignored with the piston), so that 165 psi effective internal combustion pressure
increase (ignore sine form factor) would provide 550 lbft torque.
To produce 500 HP with this torque, QT revolution will have to be 5000 rpm
(Not necessarily the optimum regime of the QT?).
The displacement volume flow for this QT would be
Turbo QT600SC Flow = 0,6 liters per chamber x 4 chambers per revolution x
5000 rpm = 12000 liters/min
the same as the piston Cat engine running at 1600 rpm.
Present all steel QT600SC prototypes weight about 150 pounds, light material
could eventually get it down to 50 pounds (?), accessories excluded (the
difference partly results from the absence of QT crankshaft and smaller size).
Notice: No comparison is perfect  Here both engines have the same power. The
volume of the combustion chamber of the piston (2,53 liters) is 4.2 times larger
than the QT600SC chamber volume (0,600 liter). The piston stroke duration at
1600 rpm is 6 times longer than the QT stroke at 5000 rpm (too high rpm ?). This
is an important limitation to this comparison  See Matching Combustion
Conditions below.
Turbo QT5SC
If one doubles all the dimensions of a QT600SC,
he gets a Turbo QT5SC (5 liters chamber; Rotor 22 inches in diameter by 8 inches
thickness) in which the torque (26,4 lbsft / psi peak torque) would be 550 x 2
x 2 x 2 = 4400 lbft. To produce 500 HP with this torque, QT revolution will
have to be 600 rpm (most realistic, but not necessarily the optimum regime of
the QT?). The displacement volume flow for this QT5SC would be
Turbo QT5SC Flow = 5 liters par chamber x 4 chambers per revolution x 600
rpm = 12000 liters/min
the same as the piston Cat engine running at 1600 rpm.
All steel QT5SC weight would be about 1200 pounds, light material could
eventually get it down to 500 pounds (?), accessories excluded (the difference
partly results from the absence of QT crankshaft and smaller size).
Notice: No comparison is perfect  Here both engines have the same power. The
volume of the combustion chamber of the piston (2,53 liters) is half that of the
QT5SC chamber volume (5 liters). The piston stroke duration at 1600 rpm is 3/4
shorter than the QT stroke at 600 rpm. This is an important limitation to this
comparison  See Matching Combustion Conditions below.
B  Matching the Combustion Conditions
Turbo QT2,53litersSC
Because the conditions of combustion vary with rpm,
volume and torque, a significantly more realistic way to make a
Quasiturbine comparison is to match the combustion chamber volume,
pressure and power stroke duration.
The Piston chamber volume of 2,53 liters defines a new QT2,53litersSC.
Internal effective combustion pressure for both engine = 165 psi
Piston power stroke duration = 1/2 of one revolution at 1600 rpm
QT2,53litersSC power stroke duration = 1/4 of one revolution
QT2,53litersSC rpm must be 800 rpm for the same stroke duration, which implies:
The piston combustion frequency is 3 fires (half the cylinders) per
revolution
The QT2,53litersSC combustion frequency is 4 fires per revolution
In one minute, the piston fires 1600 x 3 = 4800 times. QT fires 800 x 4 =
3200 times
which explains the difference of power output in this comparison.
* Under such a condition, the power of both engines will not be the same.
Cat flow displacement is 12000 liters / min,
QT2,53litersSC flow is = 2.53 liters x 4 x 800 rpm = 8100 liters /
min
* Cat Torque is 1600 lbft
QT2,53litersSC torque can be extrapolate linearly from the QT600SC chamber
volume:
QT2,53litersSC torque (pressure = 165 psi) = (2,53 / 0,600) T(QT600SC) =
4.22 x 3,3 lbft/psi x 165 psi = 2300 lbft
Sizes would be 1,62 time the sizes of the QT600SC.
* Cat power is 500 HP
QT2,53litersSC power at 165 psi and 800 rpm is = 350 HP (lower power with
higher torque) (power is less due to a lower fires frequency: 350 HP x
4800 / 3200 = 500 HP)
All steel QT2,53litersSC prototypes would weight (never been built) about
650 pounds,
light material could eventually get it down to 200 pounds (?), accessories
excluded (the difference partly results from the absence of QT crankshaft
and smaller size).
Turbo QT2,53litersSCDynamic
Preservation of the "chamber volume and the stroke
duration (rpm)" fixes the flow
QT2,53litersSC flow = 2.53 liters x 4 x 800 rpm = 8100 liters / min
corresponding to 350 HP, independently of the QT "diameter to thickness
ratio". The pistonQT geometry differences do not allow a power match
while preserving those 2 values. Notice however that this reduced power
would match the one of a 4 cylinders similar piston engine. To match the 500 HP piston power (flow of
12000 liters / min), the QT chamber must be increased in size, or the
stroke duration shorten (rpm increased). This is simply a matter of
particular geometry engine sizes and regime as the parameters "chamber
volume, stroke duration (rpm) and power" are all linked together.
If a perfect match between those 2 technologies is not generally possible, the
dynamic conditions can be optimized by further adjusting at design the QT
"diameter to thickness ratio". While assuming a constant internal pressure
of 165 psi effective, same rpm, and while keeping the power at 350 HP, the
QT2,53litersSCDynamic could have a different diameter (larger or
smaller); to preserve the chamber volume of 2,53 liters, its thickness
needs to be inversely modified by the square of the diameter reduced /
enlarged ratio. This will preserve the same torque, but will provide a
different dynamic of the QT. Similar dynamic consideration is given to the
piston engine when selecting the crankshaft diameter.
If the optimum piston power coincides or not with the Quasiturbine optimum
running conditions, it is an other matter... Weight (never been built) would
be about the same as the QT2,53litersSC, but the sizes will take a
different shape.
C  Comparison Summary
The piston reference engine is the
Caterpillar turbo change C15 15.2L HeavyDuty Engine
http://ohe.cat.com/cda/layout?m=85523&x=7
http://ohe.cat.com/cda/files/209038/7/C15.pdf

Piston Ref.
(Cat C15 15.2L) 
QT600SC 
QT5SC 
QT2,53litersSC
(Matches
chamber
and stroke) 
Type 
Turbo
4 stroke 
Turbo
4 stroke 
Turbo
4 stroke 
Turbo
4 stroke 
Chamber
volume
(liters) 
2,5
(3 x / rev.) 
0,6 (4 x /rev.) 
5,0 (4 x /rev.) 
2,5
(4 x / rev.) 
Stroke
duration
(sec) 
60/(1600 x 2) =
0,0188 
60/(5000 x 4) =
0,003 
60/(600 x 4) =
0,025 
60/(800 x 4) =
0,0188 
Engine
combustion
frequency
(/min) 
4800 
20000 
2400 
3200 
Internal
effective added
pressure
(psi) 
165 
165
(questionable?) 
165 
165 
Revolution
(rpm) 
1600 
5000
(off limit?) 
600 
800 
Torque
(lbft) 
1600 
550 
4400 
2300 
Power
(HP) 
500 
500 
500 
350 
Outside sizes
(inches) 
 
diam. 16
thickness 5 
diam. 32
thickness 10 
diam. 26
thickness 8,1 
Weight
/ optimized
(pounds) 
2900
with
accessories 
150
/ 50
+accessories 
1200
/ 500
+accessories 
650
/ 200
+accessories 
Comment 
6 cylinders
piston versus
4 chambers QT 
Small QT
requiring
too
high rpm 
Large QT
with
lower rpm 
Would match
power of
the 4 cylinders
(not the 6 cyl.) 
If the "chamber volume and stroke duration" constraints are removed, it is
likely possible to design a QT making a perfect match in power, torque and
rpm with most piston engines within a reasonable QT operating range.
However, this match will not necessarily be at the optimum QT operating
conditions...
Of course, 2 or 3 QT could be stacked side by side (like pistons are) to
produce more torque and power. Charging compressor and Stirling exhaust
heat recovery could one day also be of Quasiturbine type!
For the same pressure, steam and pneumatic QT provide more torque and
power density because they use simultaneously 2 chambers circuits, and
keep peak power all along the stroke. QTAC provides still more power
density due to the plateau shape of its pressure pulse.
Comparison Limitations
This is an approximated theoretical comparison. There
is no actual experimental data to confirming all of the above, so please
allow reasonable safety factor in all interpretations...
More Technical
Quasiturbine  Piston Differences

