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  • internal combustion engine

    My buddy and I are having a friendly argument. One of use referred to his wood stove as a internal combustion engine and the other took exception. Any thoughts on the subject?
    Richard

  • #2
    First off its not any kind of an engine to speak of because it lacks any kind of power transmission and only combusts fuel for heat, second -- if it were its not any kind of a contained environment where the combustion takes place, I.E. the stiove has to breath and is open to the atmosphere by a vent door for intake and a stove pipe for exhaust, there is no compression of any kind and no direct confinement -- so therefore its not internal combustion and its not an engine of any sorts...

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    • #3
      I've seen out-of-control stoves behave like jet engines.
      Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
      ~Practitioner of the Electromechanical Arts~

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      • #4
        And infact an external combustion engine operates on compression also but there not a closed system by a series of valves and such, they have the intake open and the exhaust open to the atmosphere, perhaps a pulse detonation engine is a little more difficult to catagorize depending on its particular design...


        But to clairify -- a jet engine is an external combustion engine...
        I know im going to catch hell for this statement but it is the way i was learned about thirty years ago in power mechanics 1,2 and 3, some will argue different and in fact have a good arguement because the fuel is in a chamber and is directly linked to the propullsion, i will not argue and can see this side of it --- but our shop teacher (who was somewhat of a purist)always stated that because they are still an open system and have no positive locks to the atmosphere that technically they cannot be considered a true I.C. engine and I can see his point as well and it is also the way iv always viewed them --- potato/potato,,, You wont get a real arguement out of me either way, in fact there are other engines that fall into the "gray" area even further...
        Last edited by A.K. Boomer; 11-28-2006, 11:27 AM.

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        • #5
          A jet engine would be a CC (continuous combustion) engine. And that combustion takes place internally.

          A wood stove is a CC engine.
          Gene

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          • #6
            It isn't an engine to begin with. As the air/fuel ratio is somewhat controlled it can't be considered an external combustion device. External combustion has an unlimited air supply.

            To be considered a heat engine it must convert heat to mechanical work.
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            • #7
              Engine, a machine that converts energy into mechanical motion.

              Motor, a device, as a machine or engine, that imparts or generates motion.

              Jet engine, an engine that develops thrust by ejecting a jet, esp. a jet of gaseous combustion products.

              Webster's 2nd New College Dictonary

              Ask yourself, did the stove produce any mechanical motion or thrust. It could have if it had blown up. So, if had exploded and slamed into a wall could it have been considered to be a jet engine????????
              Last edited by Carld; 11-28-2006, 12:49 PM.
              It's only ink and paper

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              • #8
                Exploding wood stove, interesting concept. Not gonna happen unless you fuel it with old dynamite or similar.
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  "Engine, a machine that converts energy into mechanical motion.

                  Motor, a device, as a machine or engine, that imparts or generates motion."

                  There you go. Hot wood stove=warm rising air. Thus motion

                  And it's seems to be a motor too. And a machine.

                  Whatever, it's about 14 below here when the wind is blowing, and whatever you want to call it, my wood stove is a genuine blessing.
                  Gene

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                  • #10
                    The internal combustion engine uses the fuel, oxidizer and combustion products as its working fluid.

                    The external combustion engine uses a separate working fluid which is heated etc by combustion of the fuel.

                    http://en.wikipedia.org/wiki/Internal_combustion_engine

                    Therefore, a jet engine is an internal combustion engine of the continuous combustion type (a type that includes external combustion engines as well, i.e. steam engines).

                    There is no need for compression in an internal combustion engine definition-wise. But it does increase efficiency.

                    The jet uses the fuel to increase the volume of its working fluid through heating, which fluid is then expelled at increased velocity. That jet may be used for direct propulsion, or the energy may be extracted by a turbine etc.

                    I am unable to identify a basic conceptual or topological difference between a stove and a jet engine..... Of course details such as compression, efficiency at various tasks, etc do vary.

                    The jet produces a higher velocity stream of gases through heating of its working fluid. So does the stove, although the stove is generally used merely for heat.

                    The jet may have a turbine in the exhaust stream to extract energy from teh higher velocity gases. The same can be done with a stove, although it is considerably less efficient for that..

                    The jet produces local heating, as does the stove, although the jet is considerably less efficient than a stove at that task.
                    1601

                    Keep eye on ball.
                    Hashim Khan

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                    • #11
                      The air and combustion gases in a stove are not a "working fluid" as they do no work. The stove need not have any parts that move in operation and in particular parts that are moved by the moving gases, which is why it isn't a working fluid. It isn't an engine as it does not impart motion to anything. Also, gases that rise because of density difference produce zero thrust. They are rising because they are bouyant, not because of a reaction to an action.
                      Free software for calculating bolt circles and similar: Click Here

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                      • #12
                        Originally posted by Evan
                        The air and combustion gases in a stove are not a "working fluid" as they do no work. The stove need not have any parts that move in operation and in particular parts that are moved by the moving gases, which is why it isn't a working fluid.
                        A ram-jet has almost exactly the same limits that you have just described....... think about it

                        It isn't an engine as it does not impart motion to anything. Also, gases that rise because of density difference produce zero thrust. They are rising because they are bouyant, not because of a reaction to an action.
                        The gases in a jet engine are moving due to a difference in density/pressure within the engine vs outside the engine. Same for a stove, although the relative densities are generally reversed.

                        Motion is imparted to the working fluid by a stove..... after that it is up to YOU to harness that motion and extract the energy as work. But it is available and can do work.

                        And you CAN make the gases in question move a mechanical device... a turbine..... which would not move in the absence of the stove and the heating/density change created by the stove. Easily proved.

                        I can even make a stove produce measureable thrust with no added moving parts...... I'll leave it to you to figure out how, but I will guarantee it can be done, and that it is completely dependent on the moving working fluid.

                        May I suggest that you open your mind a little........ don't be quite as rigid and rule-driven.

                        Then you will see connections a little more clearly.

                        I am not suggesting that the two are practically useful in the same way. But I AM suggesting that they each can do the other's job, at least in a demonstrable, if not practical fashion.

                        They are directly related and similar.
                        1601

                        Keep eye on ball.
                        Hashim Khan

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                        • #13
                          I don't see any way to produce thrust from the gases produced by normal operation of a wood stove. It relies on the stove having a lower pressure within the stove to supply fresh combustion air by the higher atmospheric pressure outside forcing air into the stove. Any attempt to produce thrust will require a pressure rise within the stove that will prevent fresh air from entering. The fire will go out.

                          The singular difference between a ramjet and the stove is that pressure difference. The hot gases in a stove are not expelled from the stove. To the contrary, they leave because of bouyancy and create a negative pressure within the stove. That is why they don't work if any part of the chimney is sloping down away from the stove.

                          This is diametrically different than a ramjet or any other type of thrust producing device.

                          The gases from the stove cannot be considered to do work. They don't even "draw" air into the stove. They simply leave the stove and the outside pressure forces more air in.

                          If the rising gases were made to do work by turning an impeller then the gases could be considered a working fluid similar to the Christmas decorations that rely on the hot gases from a candle to spin a pinwheel. That is a heat engine.
                          Free software for calculating bolt circles and similar: Click Here

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                          • #14
                            I put a wood stove in my basement and ran it into two side by side chimineys with a tee. After the fire had been going for awhile I heard this low roar. Turned out that the cold air was falling down one chininey, picking up some hot air at the tee and roaring up the other chiminey. Shoulda stuck a turbine in it.

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                            • #15
                              Originally posted by Evan
                              I don't see any way to produce thrust from the gases produced by normal operation of a wood stove. It relies on the stove having a lower pressure within the stove to supply fresh combustion air by the higher atmospheric pressure outside forcing air into the stove. Any attempt to produce thrust will require a pressure rise within the stove that will prevent fresh air from entering. The fire will go out.
                              Well, it's another case of opening the mind and letting the reality soak in.....

                              If you change the direction of the gases once they have some velocity, then they will produce a theoretically measurable (but, naturally very minimal) reaction thrust due to the direction change..... i.e. if you let them rush up the chimney and have a stovepipe elbow on the top.

                              Two elbows in the proper setup would spin similarly to the famous aeolipile of Hero.

                              The energy to do that will have in strict truth come (very inefficiently) from the heating effect inside the stove

                              The singular difference between a ramjet and the stove is that pressure difference. The hot gases in a stove are not expelled from the stove. To the contrary, they leave because of bouyancy and create a negative pressure within the stove. That is why they don't work if any part of the chimney is sloping down away from the stove.
                              At least if it slopes down too far..............

                              However, regardless of the exact detailed means, internal pressures, etc, BOTH a stove and a ramjet produce a stream of gases at some velocity which is caused by heating. Both can produce a thrust effect. And neither one has a moving part in the sense you mentioned.

                              Naturally one is far more efficient than the other. But the similarities exist regardless.

                              This is diametrically different than a ramjet or any other type of thrust producing device.
                              See previous....... different, yet curiously the same..... A sort of "Altoid of physics" if you will.....


                              The gases from the stove cannot be considered to do work. They don't even "draw" air into the stove. They simply leave the stove and the outside pressure forces more air in.

                              If the rising gases were made to do work by turning an impeller then the gases could be considered a working fluid similar to the Christmas decorations that rely on the hot gases from a candle to spin a pinwheel. That is a heat engine.
                              In this case you answered your own question..... showing that the stove can indeed be a heat engine if some details are taken care of.

                              Incidentally, "work", in the classical physics sense, is performed whenever a force acts over a distance. Pushing against a fixed wall does no "work", since tehre is no movement. But pushing an exactly similar pile of bricks some distance does do "work".

                              Since the "exhaust" of the stove acquires some velocity, it does in fact do some "work" in pushing aside the air outside the top of the chimney, at which point the previously hot gases are probably cooler and move more due to their acquired velocity, and due to the differential pressure produced by hotter gases below them..... Again curiously similar to a jet.........

                              Yes, I an most assuredly being "technical" and "chopping logic" here..... but I have so far said nothing that is not "true"..........
                              1601

                              Keep eye on ball.
                              Hashim Khan

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