Rotary Valve Pulse-Jets

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SR71Fan
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Re: Rotary Valve Pulse-Jets

Post by SR71Fan » Sat Oct 24, 2009 7:42 pm

Could you find a web link to the paper?
Or scan it and upload it?

If they had no success with the rotary valve, I need to find
out why. Of course, if this is true, then my engine concept is
also a failure. But with the information I have so far, there
is not explanation of **why** the rotary valve failed.

I would say that if the test was on a Dynajet, then the operating
frequency would be very high, and the error in motor RPM would have
to be **very** small in order for the engine to work.

SR71

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Re: Rotary Valve Pulse-Jets

Post by ace_fedde » Sat Oct 24, 2009 7:51 pm

Rocketman, and BB (blackbird :lol: )

It is just impossible to make something that, independently from the PJ, is timed to match every blast of the PJ. The problem is that a PJ is not a clock.
Check out my thread again, you'll find the way to match a system with the PJ's pulses. Or better said: to match the PJ's pulses with a system!
The only thing is that it's not yet proven to work :lol:

Fedde
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Re: Rotary Valve Pulse-Jets

Post by ace_fedde » Sat Oct 24, 2009 8:03 pm

Also check out this one:
viewtopic.php?f=10&t=3034&st=0&sk=t&sd=a&hilit=xjet

No rotating valves, but something is explained about the non-symetry of the cycles

Fedde
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Re: Rotary Valve Pulse-Jets

Post by SR71Fan » Sun Oct 25, 2009 5:09 am

Note to Rocket Man:

The attempt to convert a Dynajet from a reed valve to a rotary valve
probably failed because the pulse rate with a reed valve will be different
than the pulse rate with a rotary valve. The inlet flow restriction, and
probably the flow areas will be different, and they will shift the resonant
point.

It is **not** just a function of the pulse-jet's tube length.

As a side note, I would **never** attempt to apply a rotary valve to
a pulse-jet as small as a Dynajet, because the high pulse rate means
that the valve timing and fuel injection are on short time intervals,
and whatever "control loop" is needed to control the speed of the rotary
valve drive motor needs to be able to respond quickly.

Note to ace-fedde:

You should be careful about what you say is "impossible".
A lot of inventions have been made after the "experts" said it was impossible!

I think is **is** possible to (a) match the valve and fuel control to the natural
timing of a specific pulse-jet design. I also think it is possible to (b) adjust
fuel flow and inlet conditions to "pull" the natural timing of a specific pulse-jet.

But, in my opinion, I think it is likely that (a) would be more successful than (b).
This opinion is based partly on my confidence in microprocessor control, and
also because I think is will be easier to predict the pulse-jets natural timing
by analyzing the previous couple of pulse cycles than it would be to force a
deviation from the pulse-jet's natural timing.

But, as you have said, none of this has yet been proven to work.

SR71

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Re: Rotary Valve Pulse-Jets

Post by Mark » Sun Oct 25, 2009 3:21 pm

I recall some mention of the Schmidt tube where the inner reeds weren't opening as much as the outer ones and the V-1 observed to have adjacent reeds not opening on some cycles, the vagaries of inflow. I wonder if the Dynajet also plays this game with its reeds?

Something I wrote last year. I hope I have the story straight. ha
"One of the problems with the Schmidt tube was that the outer valves did a lot of lifting and the inner ones very little and this affected the endurance of the reeds and the inflow did not afford a homogenous distribution of velocity over the entire valve cross-section."
Last edited by Mark on Sun Oct 25, 2009 10:40 pm, edited 1 time in total.
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Re: Rotary Valve Pulse-Jets

Post by SR71Fan » Sun Oct 25, 2009 6:52 pm

Hello All:

The forum discussion on the Rotary Valve Pulse-Jet has been very
informative for me, and I want to thank all the participants for
their input.

One of my goals for introducing the topic of a rotary valve
pulse-jet was to demonstrate the many benefits of this particular
valving method, and then, at a later time, address many of the
potential control problems associated with it. I have many years
of experience designing microcontroller hardware and writing the
real-time sofware for them, and it isn't surprising that many of
you who don't share that experience have expressed doubts about
the ability of building a workable rotary valve pulse-jet control.
So now I want to go into more detail on how I would design such a
control system.

I believe that the key requirement to control the rotating valve
is to synchronize the rotating valve to the natural combustion
pulse frequency of the engine. I am of the opinion that trying to
"force" the engine to operate at a "non-natural" pulse frequency
would result in a "unhappy" engine that would often be fighting
against the controller.

The valve to pulse frequency synchronization must be such that the
valve is always fully closed at the exact start of the next
combustion pulse. Thus, there are two events in time that must
continue to occur at nearly the same instant. In electrical terms,
these two events must remain "in phase".

The microcontroller, or "engine control unit (ECU for brevity) must
continuously examines the phase relationship between the combustion
pulses and the valve closure point, and trims the speed of the
motor driving the rotary valve as necessary to keep these two
events in phase. In the radio communications world, this mechanism
is called a "phase locked loop" (PLL for brevity). Anyone who is
interested can research the subject of P.L.L. circuits and their
applications.

An analog circuit for performing this same function can also be
built, but it is somewhat inflexible except under constant engine
operating conditions. It would also not be able to deal with the
numerous other engine control issues, such as engine start,
fuel control, and flame-out recovery. Nonetheless, it might be
desirable to build an analog PLL control circuit for the initial
feasibility testing. I would probably **not** start with an analog
control system, because of my experience with microcontrollers, and
because I want to take advantage of the ECU method to ease the
difficulties with engine start-up.

One of the key constraints on the viability of the PLL rotary
valve control concept is the short-term stability of the pulse-jet
operating frequency, or conversely, the instantaneous variations
in the time between individual combustion events. Long-term
variations caused by speed changes, angle of attack, etc., can be
tracked by the PLL, and are actually of little concern.

For example, if the time period between individual combustion events
varies by 10% (or -5% to +5%), then even if the average valve motor
speed tracked the averate combustion event rate, there would be an
error in valve position at each combustion event of between -9 and
+9 degrees. The shape of the rotary valve port may have to be
designed so that the valve was closed over a range of -9 degrees to
+9 degrees from the ideal closed position.

The design of the fuel injection system may be the largest single
contributor to combustion pulse timing variation, so it must be
optimized for consistency in timing the fuel delivery in order to
reduce any variation in the combustion pulse period. Fuel delivery
will most likely be pulsed (discontinuous) instead of continuous
for the sake of fuel economy. Since an ECU is the controlling
element for the rotary valve drive motor, having the ECU also
control the fuel injection is a logical choice. Based on the study
on unsteady fuel injection by Miller / Dawson / Heffer, it may also
be desirable to make adjustments in the fuel injection timing on a
pulse-by-pulse basis in order to preactively "pull" the next
combustion pulse in a desired direction in the timing. But this
could also introduce further instabilities in the short-term
pulse-to-pulse timing. The beauty of "software" is that one can
experiment.

So, what would be the component parts of the ECU? First, of
course, would be the microprocessor. I would use a single-chip
microcontroller, containing FLASH memory for the program and any
data constants or look-up tables, RAM memory for working storage,
and verious peripherals for performing engine timing. These
microcontrollers often also include one or more serial
communications (COMM) ports, and a number of analog-digital (A/D)
conversion channels. We will need both of those. The COMM port is
used to communicate with a personal computer (PC), where all the
ECU programming and pulse-jet performance analysis take place.
The A/D channels have several possible uses, the most important
being the measurement of pressure versus time inside the pulse-jet.

Next, I'll describe the proposed input and output functions that
connect between the pulse-jet engine and the ECU.
First a list of proposed ECU inputs:

a) Rotary Valve Home (2 signals) - the valve is within 2% of
closed. This signal is generated twice per valve revolution,
one for each of two separate pulse transducers. The design of
of the pick-up units is such that if either of the transducers
fails, to remaining transducer can supply the "Home" signal
for both 180 degree segments of valve rotation.

b) Rotary Valve position - probable a 30 to 50 pulse per valve
revolution transducer; useful for finely resolving the
instantaneous valve rotation position, and used primarily by
the PLL. The PLL can, however, also use either of the Rotary
Valve Home signals for this purpose.

b) Combustion Pressure - this is an A/D input from an analog
pressure transducer. The ECU can obtain digital pressure
values at up to 10,000 digital values per second, with better
than 1% accuracy.

c) Pressure contact switch - usable as a backup to the combustion
pressure readings, and gives a electrical pulse when the
combustion pulse occurs.

d) Engine outlet temperture - useful for estimating combustion
efficiency and "red line" [dangerous temperature[ conditions.

Now I will describe the proposed ECU outputs:

a) Rotary Valve Speed Control - This is an analog voltage or
mA current output that is proportional to the desired rotary
valve drive motor RPM. An analog motor control feed-back loop
drives the motor to the required speed. Note that the motor
used to drive the rotating valve will have a voltage rating
that is one half of the actual supply votage. This allows
motor driver to "over drive" the motor for short periods of
time to reduce time delays on RPM changes. Electronic
"braking" is likewise used to slow the motor down quickly.

b) Spark Trigger - used to enable the spark plug used for engine
start-up

c) High Rate Fuel Flow (ON/OFF) - This is a coil drive output to
a fuel injector solenoid operating from a high-pressure
delivery source of about 100 psi (7 bars). The fuel delivery
rate is calculated to about 2/3 of the maximum required fuel
flow with maximum solenoid ON time.

d) Low Rate Fuel Flow (ON/OFF) - This is a coil drive output to
a fuel injector solenoid operating from a high-pressure
delivery source of about 100 psi (7 bars). The fuel delivery
rate is calculated to about 1/3 of the maximum required fuel
flow with maximum solenoid ON time.

Fuel flow is regulated as follows:

(d) alone = up to 33% of max. fuel flow, throttled lower by
reducing the solenoid ON time;

(c) alone = up to 67% of max. fuel flow, throttled lower by
reducing the solenoid ON time;

(c) & (d) together = up to 100% of max. fuel flow, throttled
lower by reducing the solenoid ON time of either
(c) or (d).

Either solenoid can "limp" the aircraft home if the other
solenoid fails.

Sad note: If the ECU dies, you're flying a brick!! I'll reserve
the subject of redundant ECU until **after** the concept is tested
and proven viable.

I suspect that this will many of you food for thought.

SR71

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Re: Rotary Valve Pulse-Jets

Post by tufty » Sun Oct 25, 2009 7:08 pm

Interesting thoughts, for sure.

There was a fair amount of discussion regarding "driven" valving on pulsejets on the "old" forum, although I believe that data has now been reabsorbed into the digital æther. Unless someone knows differently, of course, and some value might be had from driving the wayback machine over Kenneth's old site.

Talking about phase locked loops and the like is all very well, but you have to consider *which* phase you want to lock to, and how to measure that - remember, you're talking about a device in which combustion (hopefully) never truly ceases, where compression must be considered as a wave effect and not a single event, an effect that will be affected by the point at which you "shut the gate", as it were.

Personally, I think you will have a *very* hard time forcing an inherently analogue system to work under the constraints of a digital control system, but there's only one way to be sure. I guess if I was to try something like this, I'd take a "known good" combustor design for which there is hard data, probably something like the dynajet, and work from there. Getting something that will reliably sustain would be a considerable achievement.

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Re: Rotary Valve Pulse-Jets

Post by ace_fedde » Sun Oct 25, 2009 7:45 pm

SR71Fan wrote: The forum discussion on the Rotary Valve Pulse-Jet has been very
informative for me, and I want to thank all the participants for
their input.
Hey, I’m not ready yet! :lol: :lol:
Looks we were writing posts at the same time:

SR,
SR71Fan wrote:You should be careful about what you say is "impossible".
I was careful. That’s why I said that : it is just impossible to make something that, independently from the PJ, is timed to match every blast of the PJ.
I also said: The problem is that a PJ is not a clock. That says, in very few words the same as Eric (very experienced) says here:
viewtopic.php?f=2&t=5534&p=66453#p66453

You will need, as you also state, some coupling or control loop either to steer and correct the valve steering (and perhaps the fueling) or to steer and correct the PJ’s pulses. Without that, I dare to state again, it is impossible.
SR71Fan wrote:I think is **is** possible to (a) match the valve and fuel control to the natural timing of a specific pulse-jet design. I also think it is possible to (b) adjust
fuel flow and inlet conditions to "pull" the natural timing of a specific pulse-jet.
But, in my opinion, I think it is likely that (a) would be more successful than (b).
SR71
I think that (a) is the more safe/sure way to go. But/And somehow I expect that the NCF will be the key to success for (a). Without it I expect the PJ to run with to much variation to be able to correct the valves in time. See my post below from the other valveless thread:
ace_fedde wrote:Eric,
A question, that we probably cannot answer without experimenting, that immediatly rises to me is: Is steady fueling an inaccurate form of fueling, causing more frequency jumps than non-continious fueling (NCF)?
Appearantly steady fueling causes a surplus of available fuel, which surplus might cause the jumping (sometimes the surplus instantly deflagrates, sometimes it is left for the next beat)
The next question is then:Does NCF force the engine to run in a way that it does not like to some extent? Or does it force the engine to run in a way that it most likes, and does steady fueling prevent the PJ from running in that way (running like a clock :D )?
Then there might not be a bouncing in fuel timing, as you suggest, since the motor runs much more accurate (hopefully).
I think only experiments can give the answers. Unfortunatly my workshop, due to a situation, isn't available to me for a long time already.
Fedde
I think you, like Eric, understood my proposed (b) procedure wrong. I don’t want to force a
deviation from the PJ’s natural timing. I want to force the PJ to keep it’s own natural timing accurate.
If that is possible that way (b) is more desirable for many forum members here because they don’t have the possibility to build microprocessor controlled management systems. This (b) might even force the PJ to run more accurate than (a).
But hey, why not build a possibility in your management to jump from mode (a) to mode (b), where (b) is: freeze frequency and continue.

Fedde
Your scepticism is fuel for my brain.

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Re: Rotary Valve Pulse-Jets

Post by PyroJoe » Sun Oct 25, 2009 10:59 pm

Sounds do-able with plenty of time and resources.
Some old biomimic vision systems used a mix of analog-digital with great success. One thing that may be useful to monitor is the exhaust flow, this may give correlation to how well the valve and combustor are creating the resultant flow. Possibly giving more feed back when cycles start to become unstable.

Another thing to keep an eye on is the low pressure swing, some engines have produced low enough pressure swing that thin walled sections of the tailpipe implode/collapse. Be good to keep that in mind when trying to pull the cycle by the low end.

Also it may be possible to run a deadman function for ECU or power failure event, that an intake opens and allows a "limp home mode" as a valveless. Would certainly be a lions share of work.

Joe

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Re: Rotary Valve Pulse-Jets

Post by ace_fedde » Mon Oct 26, 2009 8:34 am

SR,

I just realize that if an micro-processor controlled ignition function is added (in both cases (a) or (b) ) we don’t have to rely anymore on the (inaccurate?) auto ignition for the cycle timing. Bye bye frequency jumps! :D

This might be a perfect motor for the experiments:
viewtopic.php?f=2&t=5055&st=0&sk=t&sd=a&start=30#p60152
Especially because it has already proven not to be a critical motor, both running valveless and valved!
Hopefully GRIM would be willing to cooperate.

My idea would be to have it first running valveless and install the NCF-system managed by your proposed microprocessor system.
If that works it is time for the rotor valves!!

There is an idea for a rotor in the older thread:
viewtopic.php?f=2&t=3221#p39423
I would make 4 or more holes, so for a PJ that runs on 200hz the servo only has to spin at 50 hz or less.

Of course these are my ideas, you probably have your own. Man, I hope you go for it!! :D

Fedde
Your scepticism is fuel for my brain.

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Re: Rotary Valve Pulse-Jets

Post by Sebastian LFT » Mon Oct 26, 2009 1:02 pm

An electric motor controlled spinning valve at a target frequency---computer controlled advance and retard to quickly adjust for frequency change.

Sensors needed--valve position sender, audio pick up to listen in on all aspects of audible frequencies. I think the controller could tune it's self by listening to the sounds it's making(not just pressure variations) and adjust for it's targeted tone. , pressure sensor , temp sensor, oxygen sensor, map sensor, baro sensor and all the rest of those little goodies... :D

Pulsating fuel injection --advanced or retarded as needed for variations in timing.

Brain--laptop or for that matter a blackberry type device with your favorite spinning rotary valve controller app. :shock:


Sounds to me all one needs is a stand alone automotive eng management system from lets say Holley (1000.00 to 3000.00 American bucks) and modify as needed to work on a pulse jet rotary valve set up.

Drag racers swore up and down that a computer controled car would never do very well. Low and behold, look at what we have now a days. Some still go with a tried and true mech carb . In the end it's all good. 8)

Now, all that is needed is a penchant for tinkering and a good programmer friend. That said...just do it already. :roll:

P.S and a little extra cash to smooth the path of success. :wink:
You'll never know 'till you try it.

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Re: Rotary Valve Pulse-Jets

Post by SR71Fan » Tue Oct 27, 2009 1:01 am

Note to ace_fedde:

It's always fun when you can see the light in someone's mind
suddenly light up.

You probably noted in my post of a day ago that ECU-controlled
spark ignition is one of the ECU outputs. And I had considered
using spark ignition on every pulse. But there are problems with
that approach:

a) The spark ignition then become a piece of critical flight
hardware; the engine will not run without it;

b) The spark ignition must then be rated for **continuous**
operation. This requires an oversized coil to prevent excess
coil heating.

My goal is to use the spark ignition **only** for start-up if at
all possible. Incidently, I use the term "spark pre-ignition"
for the concept of continuous spark ignition. One of the
advantages of using pre-ignition is that you can get the engine
to pulse faster. If you can take advantage of that, it may give
your more thrust.

Regarding designing a pulse-jet engine that will operate in either
valveless of valved mode, I am not very confident that either mode
would be very efficient that way. You will notice that the engine
you referenced in your link did not seem to operate very well in
either mode. In my opinion, there are **way** too many compromises
that have to be made to accomodate both modes. I am focusing my
efforts on the valved engine because I am more comfortable with the
idea of guaranteed reverse air flow prevention. I believe that the
rotary valve can provide additional benefits as described in
earlier postings.

I consider the valveless pulse-jet to be an inherently low speed
engine, particularly when the inlet and exhaust are both pointing
rearward. As the speed increases, the rearward-facing aair inlet
will become air-starved in the virtual "vacuum". Furthermore, in
valveless engines designed with the air inlet facing forward,
little usable thrust is generated (the engine fights itself) until
it has built up some forward speed.

Regarding NCF, you will note from the description of my proposed
ECU that the fuel flow is indeed non-continuous. I am sorry if I
did make that clear in my writing. But NCF is vital to obtaining
the best fuel economy and the most efficient combustion pulses.
I also favor very high fuel pressure (100 psi, or 7 bar) to
provide better atomization.


Note to Sebastian LFT:

You also have "seen the light", so to speak, having realized some
of the potential of the computer ECU control. But I think you may
be making the controller more complicated than it needs to be.

First of all, although the human brain can tell the minor sound
differences when an engine is operating correctly or not, the ECU
"brain" is not nearly so "smart". It is far easier for the ECU to
measure combustion pressure over 100 time during each pulse, and
the ECU can learn more from these pressure measurements than from
a microphone input would tell it. It can see how fast the air/fuel
mixture burned, what the peak pressure was, what the peak vacuum
was, and how long the entire cycle lasted.

I also think you suggested more sensors than are needed. Some of
the sensors (MAP, barometric) are usually reserved for automobile
applications. You will also notice from my previous posting on the
ECU that some sensor functions are replicated for redundancy sake.
My ECU design could have almost half of its sensors fail, and it
would still be able to keep the engine running. This is an
important issue if a person is riding in the aircraft,

Regarding the cost of the ECU, I'm pretty confident that I can
build a suitable ECU for about $200 American, plus the cost of
the sensors. Some of the sensors will be expensive. Remember
that I design microcontroller systems for my occupation. The
ECU is a simple device whsn a single-chip microcontroller is
used to build it.

SR71

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Re: Rotary Valve Pulse-Jets

Post by ace_fedde » Wed Oct 28, 2009 11:35 am

SR,
SR71Fan wrote: I consider the valveless pulse-jet to be an inherently low speed engine, particularly when the inlet and exhaust are both pointing rearward. As the speed increases, the rearward-facing air inlet will become air-starved in the virtual "vacuum".
One would expect so, but it is not reality. Thrust even increases at higher speeds. The why’s and how’s I leave to the pro’s (who already debated it in the valveless section). But I think this isn’t a topic in this thread.
SR71Fan wrote: Regarding NCF, you will note from the description of my proposed ECU that the fuel flow is indeed non-continuous. I am sorry if I did make that clear in my writing. But NCF is vital to obtaining the best fuel economy and the most efficient combustion pulses.
You did make it clear and I didn’t miss that. But I wanted to emphasis that to my expectation NCF is the way to obtain more accurate running (where fuel economy is a present that comes with it :D ) , which I consider a demand for making valve control possible:
ace_fedde wrote: But/And somehow I expect that the NCF will be the key to success for (a). Without it I expect the PJ to run with to much variation to be able to correct the valves in time.
SR71Fan wrote: Regarding designing a pulse-jet engine that will operate in either
valveless of valved mode, I am not very confident that either mode
would be very efficient that way.
Well efficiency wasn’t my goal (yet) when a proposed that/such motor. My goal was to propose a motor that can function like a stable base for experimentation (not a flying machine).
It is not so easy to build a successful PJ, even if you have plans. Also it is not so easy to start up a PJ, leaving some beginners in the believe that that build a non-runner, and they lose interest in their new hobby. Many times a slight adjustment would have been enough to make the PJ a runner, but for a beginner (I consider myself also still a beginner) it is almost impossible to recognize what should be done.
If you want to try build a new revolutionary motor from scratch, well, :( I fear the worse…

The way to success would be to add new features to a “last known working configuration”.

Here is how I would do it (and hopefully will do it some day!):
-Start with the proposed valveless PJ and make it a runner.
-Then add the reed valves and check if it still wants to run.
-NCF has never been tried on a valved PJ, so I would first try to add it in the valveless mode.
-Check if the NCF also works for the valved mode.
-Check if the NCF, in both valveless and valved mode, makes the PJ run more accurate.
-If not (enough), try add the ignition system (this should not be pre-ignition but exact on time ignition and exact in the right location). If it doesn’t help but also doesn’t get worse, keep the ignition as back-up. You might need it after rotary valves are installed.
- Now it is time to throw away the reed valves and start playing with rotary valves. :D :D
-If all works finally the moment is there to develop a flight motor.


Note that with the rotary valves that I proposed (same like in the old thread), you can choose to make more discs with different hole-sizes. From almost completely open (the PJ runs in a valveless mode anyway! Also this is a lost known working configuration), till almost completely closed.
That gives the possibility to slowly increase the valves-closed time, by changing discs, from valveless to squeezed, and find out the optimum.

Besides that I’m afraid that the rotary valves that you proposed might cause turbulence, while rotating at high speed, and increase the inlet resistance (impedance).

Fedde
Your scepticism is fuel for my brain.

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Re: Rotary Valve Pulse-Jets

Post by SR71Fan » Sat Oct 31, 2009 3:19 pm

Hello All:

This is just an update on my work on the rotary valve
pulse-jet. I am focusing my attention on the design of
the engine control unit (ECU).

Since I own a product evaluation kit for one of Freescale
Semiconductor's HC08 family parts, that is my choice for
the microcontroller. The specific part I will use is the
MC68HC908QB8, which is in a 16-pin DIP package and thus
makes it easy to hand-wire a prototype circuit.
Feel free to go to <www.frescale.com> and look up the
part and its spec's.

This microcontroller has all the required peripherals for
managing the rotary valve pulse-jet, but the 16-pin IC
(integrated circuit) package does limit the number of features
that can be included on the prototype. For example, there is
an insufficient number of Input/Output pins to accomodate all
the redundant measurements that I had proposed for the ECU.
But for a "proof-of-concept" control, this is perfectly fine.

Functions that are included are as follows:

a) 8192 bytes of FLASH program memory and 256 bytes of RAM.
These are internal to the IC.

c) COMM port for interfacing to a laptop PC
The laptop PC will be used to control all aspects of engine
operation. It can also send a command to take a series of
pressure readings from a single combustion pulse, then upload
them to the PC. The microcontroller uses its ESCI port to
communicate with the PC

d) on-chip analog to digital converter input for pressure
measurements. The design plan is to allow between 60 and
100 samples of engine pressure to be taken, the individual
samples being about 150 microseconds apart. The data will
be queued up, then sent up to the PC at a much slower rate.
The on-chip A/D converter has 10-bit resolution.

e) rotary valve position sensor input
This is an optical position detector pulse generated once
every 180 degrees of valve rotation, when the rotary valve
is closed.

f) combustion pulse (pressure switch) detector
Generates an electrical pulse whenever a combustion pulse
pressure spike occurs.

g) fuel injector driver output
The is a solenoid valve output whose ON time is controlled
by a timer in the microcontroller. The ECU can countrol
**when** and for **how long** the fuel injection event
occurs during each combustion cycle.

h) spark coil driver output
The is a ignition coil driver output whose ON time is
controlled by a timer in the microcontroller. It is
enabled *only** during the engine start cycle, then only
when the rotary valve is in the closed position and a
portion of fuel has already been injected into the engine.

i) interface to a voltage output device for valve drive motor
This used the so-called SPI interface to send motor speed
set-points to the digital-to-analog converter providing a
voltage output which is proportional to the desired RPM of
the valve drive motor

The timing of all critical events relating to PJ engine control
is to a time resolution of 814 nanoseconds (0.8 microseconds).
A set of hardware timers, not software delays, handles all of
the critical timing functions.

This particular microcontroller operates with an internal
clock of 2.4576 MHz. This really is spooky for people who are
used to a 1-2 GHz procesor on their desktop or laptop computer.
But trust me on this - I've built instruments that had more
work to do and ran with a slower internal clock. I expect
the 'HC908QB8 to be idle a lot of the time, simply waiting for
the next event in the engine control cycle.

Comments or questions are welcome.

SR71

Mark
Posts: 10723
Joined: Sat Oct 11, 2003 10:14 pm

Re: Rotary Valve Pulse-Jets

Post by Mark » Mon Nov 02, 2009 1:01 pm

Do you have a diagram or photograph of what the valves will look like?
Presentation is Everything

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