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What is a Torque Impulse Engine (TIE)? What is a clean burning 2-stroke?(TIE) Technical Analysis by John Heimbecker
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THE TORQUE IMPULSE
ENGINE (TIE) USING A STROKE
CONTROL ASSEMBLY vs THE CRANKSHAFT ENGINE A TECHNICAL ANALYSIS By: John Heimbecker INTRODUCTION: Engineers and innovators have been interested in realizing
a practical rack and pinion internal combustion engine. That is, an engine that doesn’t require a crankshaft.
This is evident by searching the patent office.
It appears that the motivation for doing this may be based primarily on
the expectation that, in comparison to a crankshaft engine, the rack and pinion
system may produce more power at better efficiency.
The torque impulse engine (TIE) is a rack and pinion engine. It may be a given that, during a power stroke in a
crankshaft engine, the piston is forced against the cylinder wall.
This fact implies that some energy (frictional heat) is being robbed from
the system. In a rack and pinion engine, the piston is not forced against
the cylinder wall, during the power stroke.
Therefore, this energy may be saved.
This implies that the longevity of the piston and cylinder in a rack and
pinion engine is likely to be better. What may not be a given is that the TIE will likely produce
more power, at a better compression ratio, than a crankshaft engine with an
equivalent piston, cylinder, and maximum torque moment.
That is, the stroke length of the TIE may be a practical 20 % longer.
Furthermore, due to this longer stroke, the piston and cylinder in the
TIE may have a smaller diameter than a crankshaft engine with an equivalent
maximum torque moment, while producing the same amount of power. This implies that the piston and cylinder in a TIE will
likely require less material. That
is, they may cost less to manufacture. Finally, while these things may be significant, there may be other significantly important reasons for using a rack and pinion system: For example, a clean-burning 2-stroke engine may be
realizable. This is of major
importance at this time, because manufacturers of motorcycles, jet skies, weed
eaters, chain saws, and many other applications have historically relied upon
the simplicity of the 2-stroke engine. In
general, the 2-stroke engine is simpler because it doesn’t rely upon a cam
shaft, lifters, poppet valves, timing belt, chain, or special gearing. These manufacturers are now being forced to choose the more
complex 4-stroke engines over the 2-stroke engines. That is, 2-stroke engines are inherently dirty, because they
burn substantial amounts of oil when they run.
This means they exhaust oil into lakes etc. Therefore, the EPA has placed restrictions on their use.
A clean-burning TIE will likely offer another choice to manufacturers. However, the adaptation of the TIE for this purpose is not the subject of this analysis. Rather, the emphasis of this analysis will focus on similarities and differences between the TIE and the crankshaft engine. I begin with the nature and theory of operation of the TIE. NATURE
OF THE TIE: The nature of the TIE is that, much like the crankshaft
engine, the TIE may also run smoothly at high rpm. That is, the piston is accelerated and decelerated at the
beginning and ending of its stroke, respectively.
However, unlike the crankshaft engine, the piston and its connecting rod
(rack) move at substantially constant velocity during the majority of the
stroke. It is during this time, (a
pulse) that work may be done on the output shaft or flywheel of the TIE. As will be seen, this is very different than the crankshaft
engine where work is done throughout the entire stroke.
In the case of the crankshaft engine, the piston is always accelerating
or decelerating. That is, a
substantially constant piston velocity does not exist, in a crankshaft engine.
Furthermore, the connecting rod (pitman arm) in a crankshaft engine does
not move rectilinearly. It has an
alternating translational and rotational movement to it. In some ways, the TIE is an equivalent replacement for the
crankshaft engine. In other ways,
it may be a much better replacement. From the standpoint of equivalence: If the same amount of fuel-mixture is taken in by each
engine during the intake stroke, intuition tells us that substantially the same
amount of energy must be released. That
is, even though the duty-cycle in the TIE is smaller, I will show that the TIE
does substantially the same amount of mechanical work on the output shaft or
flywheel. [The key here is that,
for a true and fair comparison, I will rightfully assume that the same stroke
length and maximum torque moment exist in both engines.] Some of the reasons the TIE may be a better replacement are
results from the following analysis and some of the reasons simply follow from
the fact that, in the TIE, the piston and its connecting rod (rack) follow a
rectilinear path. For example, the
clean-burning 2-stroke engine (alluded to above) is made possible, for this
reason. TIE
THEORY: The underlying theory behind the torque impulse engine (TIE) is based on the fact that the total work done by a piston in a TIE may be substantially equal to the total work done by the piston in a crankshaft engine. As the name implies, the torque impulse engine may do substantially all of its work as a medium width impulse during the piston stroke. That is, it has an on/off nature to it. Unlike its crankshaft counterpart, the work from a TIE may begin several degrees after the piston passes top dead center; (TDC) and the work may conclude several degrees before the piston reaches bottom dead center (BDC). With reference to figure 1, a basic torque impulse engine (105) is shown. Figure
1 From figure 1, the piston (140) and its connecting rod, or piston rack, (145) may be viewed as a monolithic assembly. The piston rack (145) may move along a rectilinear path. The rack teeth (127) mesh with the teeth on the forward pinion-gear, (175) at all times. This rack and pinion system is a maximum mechanical advantage system. That means, unlike its crankshaft counterpart, the distance from the center of rotation of the forward pinion-gear (175) to the rack (145) is constant. It is for this reason that an equivalent amount of work may be done by the TIE over a smaller angle of rotation. In other words, the work done by the TIE is work done at maximum mechanical advantage. At this point, it should be noted that the rack (145) is interfaced at two points. It is connected to the forward pinion-gear (175) as well as the swivel mechanism (130). However, the TIE is designed such that the rack (145) does
substantially all of its work via the pinion-gear (175).
That is, substantially none of its work is done via the swivel mechanism,
(130) because the swivel mechanism (130) is a rack (145) control mechanism. For the time being, assume the swivel mechanism (130) and
control plate (110) are not in place. Their
function will be explained in more detail, in the stroke control theory section
that follows. The relevant mechanism to the TIE theory section is now
explained: During a down stroke, the rack (145) drives the forward
pinion-gear (175) in the direction indicated.
The forward pinion-gear (175) drives the rearward pinion-gear, (176) via
a power transfer shaft, (PTS) in the direction indicated.
The PTS is not shown. However,
its positioning is indicated by the dashed line from forward pinion-gear (175)
to rearward pinion-gear (176). At
times, it transfers power from the forward pinion-gear (175) to the rearward
pinion-gear (176). The mechanical
rectifier (173) is a device that allows the forward pinion-gear (175) to grip
the power transfer shaft during the down stroke. However, during an upstroke, the mechanical rectifier (173)
allows the forward pinion-gear (175) to release the PTS.
The rearward pinion-gear (176) drives the intermediate gear (180) in the
direction indicated. Finally, the intermediate gear (180) drives the output
gear, (152) output shaft, (150) and flywheel, (160) in the direction indicated.
As is the case with a crankshaft engine, it may be assumed that the
flywheel (160) will tend to maintain a constant angular velocity. At this point, some comparisons will be made between the
TIE and the crankshaft engine. These
comparisons will be based on the ideal Otto-Cycle: With reference to figure 2, the ideal Otto-Cycle is presented. Figure
2
The Otto-Cycle shows the processes involved in an internal combustion engine, as a function of the pressure and volume. It is based on the ideal Carnot-Cycle. For example, from 1 to 2, volume is increasing, during the intake stroke, while pressure remains minimal. From 2 to 3, volume is decreasing, during the compression stroke, while pressure is increasing. (Work is being done on the gas.) Of particular interest to this analysis are the processes from 3 to 4, 4 to 5, and 5 to 6. From 3 to 4, combustion is taking place. This is ideally a constant volume process, where pressure increases rapidly. In reality, ignition occurs before top dead center (TDC). It will be assumed that this is true for both engines. Therefore, the volume in each engine is first decreasing then increasing a small amount. For this analysis, I will assume a relatively constant volume, from TDC to 32.705-degrees after TDC. From 4 to 5, the power stroke process is an adiabatic process, where pressure (piston force) decays exponentially, as volume increases. For this analysis, I will assume that the force on the piston, in each engine, will decay similarly. However, it may be a little better model for the TIE, because the piston movement is more linear, during the time work is being done. That is, in the TIE, the piston moves at a substantially constant velocity, when work is being done. So, for this analysis, assume the power stroke process occurs, from 32.705-degrees after TDC to 147.295-degrees after TDC. Finally, from 5 to 6, heat rejection may take place. This is also a constant volume process, where pressure drops rapidly. For this analysis, assume a relatively constant volume, from 147.295-degrees after TDC to 180-degrees after TDC. With this in mind, figure 3 shows an ideal piston force model. This model is based on the above ideal Otto-Cycle. I will use this ideal force model to analyze and compare both a crankshaft engine and a TIE. Figure
3
Notice that the force is constant and equal to the maximum pressure, from 0 to 32.705-degrees. Then, the force decays exponentially, from 32.705-degrees to 147.295-degrees. Finally, the force is constant, from 147.295-degrees to 180-degrees. With the model force well defined, both engines are now analyzed and compared with respect to the work they do: With reference to figure 4, two torque scenarios are shown. Figure
4
The figure on the right shows a torque model for the TIE. The figure on the left shows a torque model for the crankshaft engine. Notice first, that the stroke length of the crankshaft engine is twice its radius, and a rotation of 180-degrees is implied. However, with the TIE, a stroke length of twice its radius implies a rotation of only 2-radians. (114.59-degrees) Therefore, since both engines must have the same stroke length, the TIE may only force a rotation of 2-radians. This is consistent with the impulse beginning well past TDC and concluding well before BDC. Furthermore, in the crankshaft engine, there is an angle dependent distance associated with its torque. This is not the case with the TIE. To see how the torque in a TIE may look, refer to figure 5. Figure
5
Notice here that, with the radius and maximum pressure normalized to unity, the TIE torque curve is the same as the ideal force curve assumed earlier. Therefore, the total work done may be calculated as the area under this curve. That is, as a comparative number, the work is 0.865. Furthermore, figure 5 reveals that the total work is done over a span of 2-radians. Figure 5 also implies the nature of the TIE stroke control assembly (SCA). For example, substantially all of the work is done, from 32.705-degrees to 147.295-degrees. This assumption is based on the fact that substantial force may be held against the control plate (110) in figure 1, throughout the indicated “dead-zone.” However, in this “dead-zone,” the control plate (110) may not generate torque; and consequently, it may not do substantial work. That is, energy is being stored in the “dead-zone!” This concept will be discussed in detail, later. For now, a comparative measure of work is the important thing. To see how the torque may compare, in the crankshaft engine, refer to figure 6. Figure
6
Again, the radius and maximum pressure have been normalized to unity, and the same force model is used. The first thing to notice here is that the torque curve does not follow the force curve. Each region of torque behaves differently. Region 1 shows that the torque is substantially the maximum force times an angle dependent distance from the center of rotation. The torque in region 2 is substantially a decaying force times an angle dependent distance. The torque in region 3 is again a constant times an angle dependent distance. As was the case with the TIE, the work done in each of these regions may be thought of as the area under each torque curve. Therefore, the total work done in a crankshaft engine is the sum of the work done in region 1, 2, and 3. This total work, (0.890) as a comparative number, is within 2.5 one-hundredths of the amount of work the TIE does over the same 180-degrees. That is, the work done by each engine is substantially the same. The difference is that, due to the maximum mechanical advantage nature of the TIE, it is able to do substantially all of its work in a smaller window (impulse). STOKE
CONTROL THEORY: In the TIE theory section, the theory showed that a torque impulse engine may do substantially the same amount of work as its crankshaft counterpart. Furthermore, it was shown that the work output from a Tie may occur over a shorter interval than a typical crankshaft engine. The theoretical value for this interval was shown to be 2-radians, assuming equivalent stroke length and maximum torque moment (r-value) for each engine. The reason for this shorter interval was shown to be due to the fact that the TIE functions primarily as a maximum mechanical advantage engine. With backward reference to figure 4, the same r-value implies that each engine has the same maximum torque moment associated with it. The remainder of this section will explain how the interaction between the flywheel, (160) control plate, (110) and swivel mechanism, (130) shown in figure 1, work together to produce the output function shown in figure 5. This figure reveals three main components of the output function: {1} A first “dead-zone,” from 0 to 32.705-degrees, is implied. This is a region where substantially no work on the output shaft (150) or flywheel (160) may occur. That is, energy is being stored. {2} A region where substantially all the work may be done, on the output shaft (150) or flywheel, (160) from 32.707-degrees to 147.295-degrees, is implied. This will be referred to as the “active” region. That is, energy is being released. {3} A second “dead-zone,” from 147.295-degrees to 180-degrees, is implied. This is also a region where substantially no work on the output shaft (150) or flywheel (160) may occur. Again, energy may be stored here. To see how these three things may be enabled by the stroke control assembly, (SCA) I begin with the mechanical interaction between the flywheel, (160) control plate, (110) swivel mechanism, (130) and piston rack (145). From figure 1, the control plate (110) may rotate relative to the flywheel (160). That is, it may overrun the flywheel. To accomplish this, the control plate orifice (155) may slip over the flywheel hub (154). For the remainder of this analysis, it may be assumed that the mass of the control plate (110) is negligible. That is, it may be manufactured with strong and light weight material. The guide track (101) is part of the control plate (110). As shown, the swivel bearings (133) may straddle and follow the guide track (101). Finally, the swivel pin (135) may fit into a rack bearing (125) in the piston rack (145). It should be noted that the moment arm of the swivel pin (135) is virtually non-existent. This is important, because, rather than snapping off, bending, or breaking; it may withstand substantially large piston (140) forces during combustion and storage of energy. That is, shearing forces may be the primary design consideration for the pin. From figure 1, it may be seen that a rotating flywheel (160) may drive the control plate, (110) causing stroking of the piston, (140) as the swivel bearings (133) follow the guide track (101). However, a fired piston (140) may not cause a rotation of the flywheel, (160) via the control plate, (110) because the design allows the control plate (110) to overrun the flywheel (160). Therefore, torque on the flywheel, (160) via the swivel mechanism (130) acting on the control plate, (110) may not occur. All this is consistent with figure 5; and it is consistent with the fact that substantially all work on the flywheel (160) may be done exclusively via the forward pinion-gear, (175) mechanical rectifier, (173) power transfer shaft, (PTS) rearward pinion-gear, (176) intermediate gear, (180) output gear, (152) and output shaft (150). That is, from the standpoint of a fired piston (140) doing work on the output shaft (150) or flywheel, (160) via the control plate, (110) a “dead-zone” may exist throughout the entire stroke from 0 to 180-degrees. Therefore, from the same standpoint, a “dead-zone” also exists in the active region, because the control plate (110) may never do any substantial work on the output shaft (150) or flywheel (160). This implies that, for an active region to exist, the work must be done exclusively by the rack (145) on the forward pinion-gear (175). From this, the nature of the shape for the guide track (101) may be derived. From figure 5, the shape of the guide track (101) must, at times, allow the forward pinion-gear (175) to engage the rearward pinion-gear. This figure also implies that the shape of the guide track (101) must, at times, force the forward pinion-gear (175) to disengage the rearward pinion-gear. Furthermore, since the piston (140) may be fired in the first “dead-zone,” figure 5 implies that, during the time the forward pinion-gear (175) is forced to disengage the rearward pinion-gear, (176) the guide track (101) and control plate (110) may be holding back substantial force from the piston, (140) against the swivel pin (135). (Energy is being stored.) This is not likely to be obvious. However, it is all consistent with figure 5. To see why all of the above may be true, the derivation of the shape of the guide track (101) is now considered. First, an ancestral shape will be considered. Then, two possible descendent (derivative) shapes will be analyzed. With reference to figures 1 and 7, I begin: Figure
7
The red circle represents a possible control plate (110). The green heart-shape represents an ancestral shape for the guide track (101). To see why this may work, assume the swivel pin (135) is at the top (vertex) of the heart-shape. Furthermore, assume the pin is in the rack (145) and the rack is confined to move vertically, along a rectilinear path. With reference to figures 1, 7 and 8, assume a rotation of 180-degrees, in the direction indicated, is imminent. Figure
8
With reference to the solid green line in figures 7 and 8, as the rotation progresses, the swivel pin (135) may follow the solid green line. That is, the rack (145) moves down, as the rotation occurs. At the end of a 180-degree rotation, the swivel pin (135) will theoretically be in the center of the control plate (110). With reference to figures 1 and 9, assuming the rotation occurred at a constant angular velocity, the vertical translation of the swivel pin (135) may be viewed as a function of time. However, for clarity, the translation will be viewed as a function of the angle of rotation. (Ө) That is, the vertical position (green line) of the piston, (140) rack, (145) and swivel pin, (135) from the top of a stroke to the bottom of a stroke, is depicted as a function of theta. Figure
9
Notice that this is a linear function. Also, with r normalized to unity, the theoretical stroke length is π. That is, with backward reference to figure 4, the figure on the right shows that, for a rotation of 180-degrees, the rack (145) or swivel pin (135) should travel a distance π. At this point, it may be seen that there are two problems with a guide track (101) shaped as depicted in figure 7. First, the stroke length is too long. That is, for a comparison to a crankshaft engine, the stroke length should (theoretically) be limited to twice the radius. That means that, in this case, the theoretical stroke length is 2-radians, because the r-value is chosen to be 1, for both engines. (Refer to figure 4.) Second, at high rpm, the tortuous regions at the top and bottom of the heart-shape would require the rack (145) to change direction instantaneously. This is not mechanically practical. In order to address the first problem, a modification designed to set the stroke length at the theoretical 2-radian length is proposed: With reference to figures 1, 10 and 11, a first descendent shape for the guide track (101) is shown. Figure
10
As in figure 9, the green portion in figure 10 is a portion where the swivel pin (135) and rack (145) may move linearly. However, the red arcs represent portions where the swivel pin (135) and rack do not move. That is, these arcs are struck about the center of rotation of the control plate (110). Furthermore, a deviation distance (d) is shown at the top and bottom. With the deviation distance chosen, as indicated in figure 10, [d = (π – 2)/2 and r = 1] and with reference to figure 11, the implied stroke length may now be seen to be 2-radians. Figure 11
Again, the vertical translation of the swivel pin (135) may
be viewed as a function of time. However,
for clarity, the translation will be viewed as a function of the angle of
rotation. (Ө) That is, the
vertical position (green line) of the piston, (140) rack, (145) and swivel pin,
(135) from the top of a stroke to the bottom of a stroke, is depicted as a
function of theta. Notice that, although the proposed deviation (d) may have
set the stroke length to 2-radians, there are now 4 tortuous points.
These points are marked by arrows in both figures 10 and 11. With reference to figure 12, a solution is proposed: Figure
12
In order to remove the tortuous points shown in figures 10
and 11, the deviation distance (d) may be chosen such that a non-linearity
exists, near the top and bottom of the stroke.
That is, the swivel pin, (135) rack, (145) and piston (140) may all
accelerate and decelerate near TDC and BDC.
This implies a different modification. With reference to figures 1, 12 and 13, a second descendent shape for the guide track (101) is proposed: Figure
13
The black line in figure 13 may now be seen to bare more of
a resemblance to the shape of the guide track (101) depicted in figure 1.
It may now be seen that the swivel mechanism (130) may more easily follow
this shape at high rpm. Furthermore, there is a smaller deviation distance (d)
implied. With backward reference to
figure 12, the effect of this smaller deviation distance (d) may be seen more
clearly. That is, when the heart-shape is modified, (smoothed) in
this way, the result is to make the vertical position of the swivel mechanism,
(130) with respect to the angle theta, non-linear near the top and bottom.
That is, the swivel pin, (135) piston, (140) and rack (145) may now
accelerate and decelerate in the first and second dead-zone, respectively.
So, the proposed new shape (second descendant) may do three things: First, the piston, (140) rack, (145) and swivel mechanism,
(130) may reciprocate smoothly and naturally at high rpm. Second, an effective disengagement of the forward
pinion-gear (175) is forced by the control plate, (110) at the right time and
angle. That is, physics dictates
that the rack (145) will move at substantially constant linear velocity, when it
is doing work on the output shaft (150) or flywheel (160).
This is due to the fact that, by their nature, the output shaft (150) and
flywheel (160) tend to rotate at substantially constant angular velocity.
Therefore, the entire region, where deceleration and acceleration occur,
may be viewed as a region where there exists (effectively) a complete and total
disengagement of the forward pinion-gear (175) with respect to the PTS, and
thus, the output shaft (150). These regions are shown in red and green in figure 13.
During this time, substantial force from the piston (140) may be held by
the control plate, (110) via the swivel pin (135).
However, this force may not be converted into torque or work, because the
control plate (110) is free to overrun the flywheel (160).
That is, energy is being stored here. Third, by reducing the deviation distance, [d = (π –
2.5)/2 and r = 1] the stroke length is increased by 20 %. That is, in order for the active region to be maintained in
the theoretical window implied in {2} above, the actual stroke length here (π
– 2d) is chosen to be 2.5-radians. This
is proposed as a practical matter. That
is, a smooth transition of the rack (145) from stop to engagement may now occur,
at the right time. In order to maintain a fair comparison between the two
engines, the issue of a longer stroke is now addressed: The issue is that, with a 20 % longer stroke, the TIE may
draw in more energy (fuel-mixture). Therefore,
it may be argued, the TIE may use more energy to do substantially the same
amount of work as a crankshaft engine. This
is not likely to be the case. For example, with a longer stroke, we may expect the ideal
force curve (figure 3) to be shifted up. That
is, the maximum pressure will likely be higher, for two reasons.
First, more fuel-mixture is draw in.
Second, a longer stroke implies a higher compression ratio.
Therefore, more fuel will likely yield more work (energy) than the
crankshaft engine. This may be as expected.
However, the unexpected result here may be that a longer stroke may exist
in the TIE, as compared to a crankshaft engine with the same r-value (maximum
torque moment). Two things follow
from this. First, the efficiency is likely to be enhanced, with a higher compression ratio. Second, with the same r-value, the TIE may draw in more energy (fuel-mixture). That is, it may produce more power than a crankshaft engine with the same maximum mechanical advantage. This is an important observation. From a slightly different perspective, notice the “false window” in figure 12. If the theoretical 2-radian stroke length was chosen, a false window for comparison would be implied. That is, even though the TIE may do its work within this false window, a work comparison here will likely be meaningless. This is because the ideal force model is based on the Otto-Cycle in figure 2. That is, the constant volume assumption doesn’t apply within the false window. From a final perspective, if the engine is an aspirated engine, the piston and cylinder diameter may be reduced, so that, even though the stroke is 20 % longer, the same amount of (energy) fuel-mixture may be drawn in on the intake stroke. If this were the case, the higher compression ratio will likely boost the maximum pressure. Thus, the ideal force curve may be shifted up again. This may be more than enough to compensate for the reduced pressure area of the piston. Therefore, it is likely that the comparison remains substantially valid. CONCLUSIONS: In conclusion, it has been shown that the torque impulse engine (TIE) is a viable and mechanically practical engine. That is, it may run smoothly at high rpm, because the piston and rack assembly are accelerated and decelerated near top and bottom dead center. Furthermore, because the moment arm of the swivel pin (135 in figure 1) is substantially non-existent, the control plate (110) may hold back substantial piston force (storing energy) until the time occurs where this force does work on the output shaft (150) or flywheel (160). A comparison between a crankshaft engine and the TIE revealed that the TIE may be a functionally superior engine. For example, it was a given (in the introduction) that substantial piston side forces would not exist in the TIE. Therefore, the associated heat (energy) may be saved in the TIE. As a consequence, the piston and cylinder in a TIE may have more longevity; and the efficiency will likely be enhanced. Furthermore, it was shown that, given the same amount of energy, (fuel-mixture) the TIE may produce the same amount of work as its crankshaft counterpart. It was also shown that, when compared to a crankshaft engine with the same maximum mechanical advantage, the TIE may take in more energy. That is, the stroke may be a practical 20 % longer, resulting in an engine that produces more power at better efficiency. Another perspective implied that, when the TIE produces substantially the same work and power as an equivalent crankshaft engine, its piston and cylinder may have smaller diameters. This likely means the cost of the piston and cylinder will be less, because less material may be needed. Finally, while these things are significant, one of the most important reasons for replacing the crankshaft engine with a TIE is that the TIE makes possible a clean-burning, highly efficient, 2-stroke engine. For more information, see “What is a clean-burning TIE?” or watch the animations.
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