Quasiturbine> Product> QT Combustion?

 


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 pick-up arbitrary the:
Caterpillar Turbo charge C15 15.2L Heavy-Duty 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 In-Line
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 1550-2050 lb-ft @ 1200 rpm


For comparison, let's consider a single operation point approximated from the graph as follow:
Torque 1600 lb-ft;
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 QT-SC). Turbo Cat Net Added Pressure = 165 psi effective

Turbo QT600SC

As a guess, an equivalent combustion QT600SC would theoretically give 3,3 lb-ft / 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 lb-ft 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 lbs-ft / psi peak torque) would be 550 x 2 x 2 x 2 = 4400 lb-ft. 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 lb-ft
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 lb-ft/psi x 165 psi = 2300 lb-ft
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 QT2,53litersSC-Dynamic

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 piston-QT 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 QT2,53litersSC-Dynamic 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 Heavy-Duty 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
 (lb-ft)
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. QT-AC 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