On Sun, 11 Dec 2011 12:07:23 -0500, Jerry Avins <jya@ieee.org> wrote:>On 12/10/2011 11:40 PM, Rune Allnor wrote: >> On 11 Des, 04:40, Jerry Avins<j...@ieee.org> wrote: >>> On 12/10/2011 4:56 PM, glen herrmannsfeldt wrote: >>> >>> >>> >>> >>> >>>> Jerry Avins<j...@ieee.org> wrote: >>> >>>> (snip) >>>>>> Well yes, but it was burning ~something~, in a firebox, sort of >>>>>> internally...did you think I meant petrol? :-) >>> >>>>> I knew you didn't mean that, but it is what you said. Otto and Diesel >>>>> engines are called "internal combustion" engines because the combustion >>>>> takes place in the working cylinder. I imagine jet engines are in the >>>>> same category, but I've not heard them so called. >>> >>>> I haven't thought about this for a while. I had thought that the >>>> distinction was that for internal combustion the oxygen supply is >>>> fixed before combustion starts. Maybe fuel, also. As combustion >>>> procedes, it does so at ever decreasing oxygen concentration. >>> >>>>> "External combustion" describes most steam engines including >>>>> turbines, and Stirling engines. >>> >>>> And also a continuous supply of fuel and oxidizer. That would seem >>>> to me to make them more similar to jet engines. (or the other >>>> way around.) >>> >>> Wouldn't "continuous combustion" be a more apt description then? >> >> For what? Both the biler in a steam engine and the >> combustion chamber of a jet engine would classify >> as 'continuous'. But the steam engine uses external >> combustion (the furnace (?) is external to the >> pressure chamber - pistons) while the jet engine >> combustion is internal - it generates the pressure >> that drives the rear fan. > >Internal or external combustion is one division, while continuous or >intermittent combustion is another. As far as I know, all external >combustion engines are continuous, while internal combustion can be >either. Typical jet engines -- Brayton cycle and ramjet -- are >internal-continuous, but pulse jets are internal-intermittent, like >Diesel and Otto engines. If we try, we could probably invent more >classifications, but I'm content to stop here. > >Jerry >-- >Engineering is the art of making what you want from things you can get.����������������������������������������������������������������������� Yeah, even among "internal intermittent" there's reciprocal and rotary. And within both of those there are a number of subsets, especially for reciprocal. There's no reason one couldn't use an intermittent external combustion as long as the energy flow still worked right. I'm imagining intermittent applications of something really hot like thermite to a heatsink that then keeps the water boiling for a steam engine. I don't know that anything like that has actually been built, but clearly it could be. Eric Jacobsen Anchor Hill Communications www.anchorhill.com
OT: What does 'rocket' mean?
Started by ●December 10, 2011
Reply by ●December 11, 20112011-12-11
Reply by ●December 11, 20112011-12-11
On 11 Des, 18:48, eric.jacob...@ieee.org (Eric Jacobsen) wrote:> There's no reason one couldn't use an intermittent external combustion > as long as the energy flow still worked right. � I'm imagining > intermittent applications of something really hot like thermite to a > heatsink that then keeps the water boiling for a steam engine. > > I don't know that anything like that has actually been built, but > clearly it could be.Isn't that how nuclear powerplants work? Radiacive fuel -> heat -> steam -> electrics? Rune
Reply by ●December 11, 20112011-12-11
On Sun, 11 Dec 2011 09:53:11 -0800 (PST), Rune Allnor <allnor@tele.ntnu.no> wrote:>On 11 Des, 18:48, eric.jacob...@ieee.org (Eric Jacobsen) wrote: > >> There's no reason one couldn't use an intermittent external combustion >> as long as the energy flow still worked right. =A0 I'm imagining >> intermittent applications of something really hot like thermite to a >> heatsink that then keeps the water boiling for a steam engine. >> >> I don't know that anything like that has actually been built, but >> clearly it could be. > >Isn't that how nuclear powerplants work? >Radiacive fuel -> heat -> steam -> electrics? > >RuneEven in a nuclear system the heat from the reaction is applied continuously, not intermittently, at least not intermittently enough to think of it as such when comparing the systems previously discussed. And one usually hopes that with a nuclear system "combustion" isn't involved. ;) Eric Jacobsen Anchor Hill Communications www.anchorhill.com
Reply by ●December 12, 20112011-12-12
Eric Jacobsen <eric.jacobsen@ieee.org> wrote: (snip)> Even in a nuclear system the heat from the reaction is applied > continuously, not intermittently, at least not intermittently enough > to think of it as such when comparing the systems previously > discussed.There have been suggestions for fusion power that really are intermittent, generating heat from a reaction every so many minutes or even hours.> And one usually hopes that with a nuclear system "combustion" isn't > involved. ;)-- glen
Reply by ●December 12, 20112011-12-12
On Dec 11, 12:48�pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote:> On Sun, 11 Dec 2011 12:07:23 -0500, Jerry Avins <j...@ieee.org> wrote: > >On 12/10/2011 11:40 PM, Rune Allnor wrote: > >> On 11 Des, 04:40, Jerry Avins<j...@ieee.org> �wrote: > >>> On 12/10/2011 4:56 PM, glen herrmannsfeldt wrote: > > >>>> Jerry Avins<j...@ieee.org> � �wrote: > > >>>> (snip) > >>>>>> Well yes, but it was burning ~something~, in a firebox, sort of > >>>>>> internally...did you think I meant petrol? :-) > > >>>>> I knew you didn't mean that, but it is what you said. Otto and Diesel > >>>>> engines are called "internal combustion" engines because the combustion > >>>>> takes place in the working cylinder. I imagine jet engines are in the > >>>>> same category, but I've not heard them so called. > > >>>> I haven't thought about this for a while. �I had thought that the > >>>> distinction was that for internal combustion the oxygen supply is > >>>> fixed before combustion starts. �Maybe fuel, also. �As combustion > >>>> procedes, it does so at ever decreasing oxygen concentration. > > >>>>> "External combustion" �describes most steam engines including > >>>>> turbines, and Stirling engines. > > >>>> And also a continuous supply of fuel and oxidizer. �That would seem > >>>> to me to make them more similar to jet engines. (or the other > >>>> way around.) > > >>> Wouldn't "continuous combustion" be a more apt description then? > > >> For what? Both the biler in a steam engine and the > >> combustion chamber of a jet engine would classify > >> as 'continuous'. But the steam engine uses external > >> combustion (the furnace (?) is external to the > >> pressure chamber - pistons) while the jet engine > >> combustion is internal - it generates the pressure > >> that drives the rear fan. > > >Internal or external combustion is one division, while continuous or > >intermittent combustion is another. As far as I know, all external > >combustion engines are continuous, while internal combustion can be > >either. Typical jet engines -- Brayton cycle and ramjet -- are > >internal-continuous, but pulse jets are internal-intermittent, like > >Diesel and Otto engines. If we try, we could probably invent more > >classifications, but I'm content to stop here. > > >Jerry > >-- > >Engineering is the art of making what you want from things you can get. > > ����������������������������������������������������������������������� > Yeah, even among "internal intermittent" there's reciprocal and > rotary. �And within both of those there are a number of subsets, > especially for reciprocal. > > There's no reason one couldn't use an intermittent external combustion > as long as the energy flow still worked right. � I'm imagining > intermittent applications of something really hot like thermite to a > heatsink that then keeps the water boiling for a steam engine. > > I don't know that anything like that has actually been built, but > clearly it could be. > > Eric Jacobsen > Anchor Hill Communicationswww.anchorhill.com- Hide quoted text - > > - Show quoted text -
Reply by ●December 12, 20112011-12-12
On Dec 11, 12:48�pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote:> On Sun, 11 Dec 2011 12:07:23 -0500, Jerry Avins <j...@ieee.org> wrote: > >On 12/10/2011 11:40 PM, Rune Allnor wrote: > >> On 11 Des, 04:40, Jerry Avins<j...@ieee.org> �wrote: > >>> On 12/10/2011 4:56 PM, glen herrmannsfeldt wrote: > > >>>> Jerry Avins<j...@ieee.org> � �wrote: > > >>>> (snip) > >>>>>> Well yes, but it was burning ~something~, in a firebox, sort of > >>>>>> internally...did you think I meant petrol? :-) > > >>>>> I knew you didn't mean that, but it is what you said. Otto and Diesel > >>>>> engines are called "internal combustion" engines because the combustion > >>>>> takes place in the working cylinder. I imagine jet engines are in the > >>>>> same category, but I've not heard them so called. > > >>>> I haven't thought about this for a while. �I had thought that the > >>>> distinction was that for internal combustion the oxygen supply is > >>>> fixed before combustion starts. �Maybe fuel, also. �As combustion > >>>> procedes, it does so at ever decreasing oxygen concentration. > > >>>>> "External combustion" �describes most steam engines including > >>>>> turbines, and Stirling engines. > > >>>> And also a continuous supply of fuel and oxidizer. �That would seem > >>>> to me to make them more similar to jet engines. (or the other > >>>> way around.) > > >>> Wouldn't "continuous combustion" be a more apt description then? > > >> For what? Both the biler in a steam engine and the > >> combustion chamber of a jet engine would classify > >> as 'continuous'. But the steam engine uses external > >> combustion (the furnace (?) is external to the > >> pressure chamber - pistons) while the jet engine > >> combustion is internal - it generates the pressure > >> that drives the rear fan. > > >Internal or external combustion is one division, while continuous or > >intermittent combustion is another. As far as I know, all external > >combustion engines are continuous, while internal combustion can be > >either. Typical jet engines -- Brayton cycle and ramjet -- are > >internal-continuous, but pulse jets are internal-intermittent, like > >Diesel and Otto engines. If we try, we could probably invent more > >classifications, but I'm content to stop here. > > >Jerry > >-- > >Engineering is the art of making what you want from things you can get. > > ����������������������������������������������������������������������� > Yeah, even among "internal intermittent" there's reciprocal and > rotary. �And within both of those there are a number of subsets, > especially for reciprocal. > > There's no reason one couldn't use an intermittent external combustion > as long as the energy flow still worked right. � I'm imagining > intermittent applications of something really hot like thermite to a > heatsink that then keeps the water boiling for a steam engine. > > I don't know that anything like that has actually been built, but > clearly it could be. > > Eric Jacobsen > Anchor Hill Communicationswww.anchorhill.com- Hide quoted text - > > - Show quoted text -Well it is not combustion, but it is surely intermittant. Back in the 1960s two nukes were set off underground in a Missisippi salt dome mostly for seismic studies but also to hopefully store heat to be used over a period of time. Needless to say the thermal storage didn't work very well. Clay
Reply by ●December 12, 20112011-12-12
On Dec 12, 12:45�am, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:> Eric Jacobsen <eric.jacob...@ieee.org> wrote: > > (snip) > > > Even in a nuclear system the heat from the reaction is applied > > continuously, not intermittently, at least not intermittently enough > > to think of it as such when comparing the systems previously > > discussed. > > There have been suggestions for fusion power that really > are intermittent, generating heat from a reaction every so many > minutes or even hours. > > > And one usually hopes that with a nuclear system "combustion" isn't > > involved. � ;)Sadly the plutonium processing facility, Rocky Flats (now razed) caught fire (plutonium burns very easily!) and radioactive smoked was vented to the atmosphere! Clay> > -- glen
Reply by ●December 13, 20112011-12-13
On Dec 11, 9:07=A0am, Jerry Avins <j...@ieee.org> wrote:> On 12/10/2011 11:40 PM, Rune Allnor wrote: > > > > > On 11 Des, 04:40, Jerry Avins<j...@ieee.org> =A0wrote: > >> On 12/10/2011 4:56 PM, glen herrmannsfeldt wrote: > > >>> Jerry Avins<j...@ieee.org> =A0 =A0wrote: > > >>> (snip) > >>>>> Well yes, but it was burning ~something~, in a firebox, sort of > >>>>> internally...did you think I meant petrol? :-) > > >>>> I knew you didn't mean that, but it is what you said. Otto and Diese=l> >>>> engines are called "internal combustion" engines because the combust=ion> >>>> takes place in the working cylinder. I imagine jet engines are in th=e> >>>> same category, but I've not heard them so called. > > >>> I haven't thought about this for a while. =A0I had thought that the > >>> distinction was that for internal combustion the oxygen supply is > >>> fixed before combustion starts. =A0Maybe fuel, also. =A0As combustion > >>> procedes, it does so at ever decreasing oxygen concentration. > > >>>> "External combustion" =A0describes most steam engines including > >>>> turbines, and Stirling engines. > > >>> And also a continuous supply of fuel and oxidizer. =A0That would seem > >>> to me to make them more similar to jet engines. (or the other > >>> way around.) > > >> Wouldn't "continuous combustion" be a more apt description then? > > > For what? Both the biler in a steam engine and the > > combustion chamber of a jet engine would classify > > as 'continuous'. But the steam engine uses external > > combustion (the furnace (?) is external to the > > pressure chamber - pistons) while the jet engine > > combustion is internal - it generates the pressure > > that drives the rear fan. > > Internal or external combustion is one division, while continuous or > intermittent combustion is another. As far as I know, all external > combustion engines are continuous, while internal combustion can be > either. Typical jet engines -- Brayton cycle and ramjet -- are > internal-continuous, but pulse jets are internal-intermittent, like > Diesel and Otto engines. If we try, we could probably invent more > classifications, but I'm content to stop here. > > Jerry > -- > Engineering is the art of making what you want from things you can get. > =AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF==AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF= =AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF An important distinction is where the oxidizer comes from: jets typically require atmospheric oxygen to burn a stored fuel; rockets carry their own oxidizers, so may operate in a vacuum as well as in the atmosphere.
Reply by ●December 13, 20112011-12-13
>Eric Jacobsen <eric.jacobsen@ieee.org> wrote: > >(snip) >> Even in a nuclear system the heat from the reaction is applied >> continuously, not intermittently, at least not intermittently enough >> to think of it as such when comparing the systems previously >> discussed. > >There have been suggestions for fusion power that really >are intermittent, generating heat from a reaction every so many >minutes or even hours.Has there been a proposal for fusion power which is *not* intermittent? The containment rings, laser bombarders, and other strategies all seem to take a measure of fuel, make it pop, and then start again with another measure of fuel. The small scale continuous fusers, used for medical and research purposes, don't ever seem to have been seriously proposed as a power source.>> And one usually hopes that with a nuclear system "combustion" isn't >> involved. ;)Steve
Reply by ●December 13, 20112011-12-13
On 12/13/2011 11:19 AM, cassiope wrote: ...> An important distinction is where the oxidizer comes from: jets > typically require > atmospheric oxygen to burn a stored fuel; rockets carry their own > oxidizers, so > may operate in a vacuum as well as in the atmosphere.Back when I was a kid and Buck Rogers* was popular, some people argued that rockets couldn't operate outside the atmosphere because there would be nothing for the exhaust plume to push against. Not just some of my contemporaries, but adults also. It's very hard to explain anything to people like that. They're still around today, but the subjects are different. Jerry ______________________________ * http://en.wikipedia.org/wiki/Buck_Rogers -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
