Question regarding your work

Hello!

I would like to begin by thanking you for your very interesting work in regenerative methane cooling!

In your thesis, you explore the parameters of regenerative cooling of an aluminium combustion chamber. In your analysis, you determine the resulting pressure drop across the cooling passages to be 44 bar (if I remember the figure correctly). Naturally, it would be preferred if this figure was lowered.

A somewhat controversial method of lowering the pressure drop would to use a coolant with better thermodynamic properties instead, namely the engine's supercritical oxygen. As I cannot see that you have discussed this in any of your works, what made you reject this possibility? There are several NASA papers discussing the feasability of supercritical oxygen regenerative cooling of hydrocarbon engines.

Thank you for your work!

Sincerely, Vilhelm Jutvik

P.S. I am trying to reach you through GitHub as I couldn't find your e-mail adress anywhere.

Dear Vilhelm,

The main reason why I investigated methane was that it was by far the most mentioned in literature.

As far as I know, this is related to flammability risks:

Pure oxygen is a serious flammability risk; aluminium in combination with pure oxygen is an even bigger flammability risk - this may easily result in a metal fire
The higher the temperature of oxygen, the bigger the flammability risk. This is an obvious concern inside the cooling channels

I agree that it sounds interesting to cool with oxygen, not only because of the thermodynamic properties (I didn't really look into that, so I can't comment on it) but also because of the higher mass flow available (since the engine is running with O/F around 3 or so.

Best regards, Luka Denies

On Mon, May 15, 2017 at 11:47 AM, vjutvik notifications@github.com wrote:

Hello!

I would like to begin by thanking you for your very interesting work in regenerative methane cooling!

In your thesis, you explore the parameters of regenerative cooling of an aluminium combustion chamber. In your analysis, you determine the resulting pressure drop across the cooling passages to be 44 bar (if I remember the figure correctly). Naturally, it would be preferred if this figure was lowered.

A somewhat controversial method of lowering the pressure drop would to use a coolant with better thermodynamic properties instead, namely the engine's supercritical oxygen. As I cannot see that you have discussed this in any of your works, what made you reject this possibility? There are several NASA papers discussing the feasability of supercritical oxygen regenerative cooling of hydrocarbon engines.

Thank you for your work!

Sincerely, Vilhelm Jutvik

P.S. I am trying to reach you through GitHub as I couldn't find your e-mail adress anywhere.

— You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub https://github.com/ldenies/OMECA/issues/1, or mute the thread https://github.com/notifications/unsubscribe-auth/AMQ3V-vSWTxo3El5_LJCP9_9wUYiEkXuks5r6B86gaJpZM4Na5yr .

Dear Luka,

thank you for your swift reply!

In regard to oxygen: I was of the same understanding as you, but then I found a number of NASA papers which adressed the issues you stated. It seems like the combustion dangers associated with supercritical oxygen cooling are few, as long as you maintain a wall temperature below that of autoignition. I have not yet found any reliable data for oxygen autoignition temperature for the environments concerned, but from what I found, it's probably above that of the aluminium's melting point. I have several NASA reports on the subject, and if you are interested and give me your e-mail adress, I can send them to you (my adress is ville -at- imorgon -dot- se.

There are also some interesting discussions on the aRocket mailing list regarding the issue in question.

Did you, or someone else for that matter, proceed with constructing any hardware using the Cu or Al regenerative chamber?

Sincerely, Vilhelm Jutvik

Dear Vilhelm,

I would not be as confident that keeping the oxygen below auto-ignition temperature is sufficient. In cooling channels, especially impact of foreign material (e.g. a metal particle) would be a substantial hazard because of the high flow velocities. Such a high velocity particle may generate a spark and destroy your engine. You can reduce the risk by using filter, but because of the big surface area in the manifold and the high number of channels, the risk remains present. In any case, I would be interested in the reports if you have them.

We didn't construct any hardware in the end, I think the project group finally even decided to use another fuel (together with LOX), because liquid methane was hard to come by.

Best regards, Luka

On Mon, May 15, 2017 at 2:00 PM, vjutvik notifications@github.com wrote:

Dear Luka,

thank you for your swift reply!

In regard to oxygen: I was of the same understanding as you, but then I found a number of NASA papers which adressed the issues you stated. It seems like the combustion dangers associated with supercritical oxygen cooling are few, as long as you maintain a wall temperature below that of autoignition. I have not yet found any reliable data for oxygen autoignition temperature for the environments concerned, but from what I found, it's probably above that of the aluminium's melting point. I have several NASA reports on the subject, and if you are interested and give me your e-mail adress, I can send them to you (my adress is ville -at- imorgon -dot- se.

There are also some interesting discussions on the aRocket mailing list regarding the issue in question.

Did you, or someone else for that matter, proceed with constructing any hardware using the Cu or Al regenerative chamber?

Sincerely, Vilhelm Jutvik

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/ldenies/OMECA/issues/1#issuecomment-301454779, or mute the thread https://github.com/notifications/unsubscribe-auth/AMQ3V_Zyi_pIw6DgwW92tNIc3tBM7_Kdks5r6D56gaJpZM4Na5yr .

You are certainly right about the risk of FOD generating a spark! The risks associated with that would be an interesting subject to explore...

I just realized that I might be able to forward the reports through GitHub's mail system. They are included below and are an interesting read. I suggest you begin with lox_regen_cooling.pdf and oxygen_regen_cooling_tm-88805.pdf as they describe complete engine systems and devote much time to discussing the risks associated with leaks into the combustion chamber.

Sad to hear that methane was rejected in the end, but fuel / material availability is a major, and often underestimated hurdle, that have crushed many individuals' and organizations' plans... I liked your ideas regarding the anodized aluminium chamber, and maybe a change of coolant might bring it closer to hardware!

Thank you for answering my questions!

Sincrely, Vilhelm

P.S. GitHub rejected the attachments! Please give me your e-mail so that I can send the files directly to you!

2017-05-15 15:21 GMT+02:00 ldenies notifications@github.com:

Dear Vilhelm,

I would not be as confident that keeping the oxygen below auto-ignition temperature is sufficient. In cooling channels, especially impact of foreign material (e.g. a metal particle) would be a substantial hazard because of the high flow velocities. Such a high velocity particle may generate a spark and destroy your engine. You can reduce the risk by using filter, but because of the big surface area in the manifold and the high number of channels, the risk remains present. In any case, I would be interested in the reports if you have them.

We didn't construct any hardware in the end, I think the project group finally even decided to use another fuel (together with LOX), because liquid methane was hard to come by.

Best regards, Luka

On Mon, May 15, 2017 at 2:00 PM, vjutvik notifications@github.com wrote:

Dear Luka,

thank you for your swift reply!

In regard to oxygen: I was of the same understanding as you, but then I found a number of NASA papers which adressed the issues you stated. It seems like the combustion dangers associated with supercritical oxygen cooling are few, as long as you maintain a wall temperature below that of autoignition. I have not yet found any reliable data for oxygen autoignition temperature for the environments concerned, but from what I found, it's probably above that of the aluminium's melting point. I have several NASA reports on the subject, and if you are interested and give me your e-mail adress, I can send them to you (my adress is ville -at- imorgon -dot- se.

There are also some interesting discussions on the aRocket mailing list regarding the issue in question.

Did you, or someone else for that matter, proceed with constructing any hardware using the Cu or Al regenerative chamber?

Sincerely, Vilhelm Jutvik

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/ldenies/OMECA/issues/1#issuecomment-301454779, or mute the thread https://github.com/notifications/unsubscribe-auth/AMQ3V_Zyi_ pIw6DgwW92tNIc3tBM7_Kdks5r6D56gaJpZM4Na5yr

.

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Hi Vilhelm,

No problem! If you need help, don't hesitate to contact me at lukadenies@gmail.com

Best regards, Luka

On Mon, May 15, 2017 at 4:30 PM, vjutvik notifications@github.com wrote:

You are certainly right about the risk of FOD generating a spark! The risks associated with that would be an interesting subject to explore...

I just realized that I might be able to forward the reports through GitHub's mail system. They are included below and are an interesting read. I suggest you begin with lox_regen_cooling.pdf and oxygen_regen_cooling_tm-88805.pdf as they describe complete engine systems and devote much time to discussing the risks associated with leaks into the combustion chamber.

Sad to hear that methane was rejected in the end, but fuel / material availability is a major, and often underestimated hurdle, that have crushed many individuals' and organizations' plans... I liked your ideas regarding the anodized aluminium chamber, and maybe a change of coolant might bring it closer to hardware!

Thank you for answering my questions!

Sincrely, Vilhelm

P.S. GitHub rejected the attachments! Please give me your e-mail so that I can send the files directly to you!

2017-05-15 15:21 GMT+02:00 ldenies notifications@github.com:

Dear Vilhelm,

I would not be as confident that keeping the oxygen below auto-ignition temperature is sufficient. In cooling channels, especially impact of foreign material (e.g. a metal particle) would be a substantial hazard because of the high flow velocities. Such a high velocity particle may generate a spark and destroy your engine. You can reduce the risk by using filter, but because of the big surface area in the manifold and the high number of channels, the risk remains present. In any case, I would be interested in the reports if you have them.

We didn't construct any hardware in the end, I think the project group finally even decided to use another fuel (together with LOX), because liquid methane was hard to come by.

Best regards, Luka

On Mon, May 15, 2017 at 2:00 PM, vjutvik notifications@github.com wrote:

Dear Luka,

thank you for your swift reply!

In regard to oxygen: I was of the same understanding as you, but then I found a number of NASA papers which adressed the issues you stated. It seems like the combustion dangers associated with supercritical oxygen cooling are few, as long as you maintain a wall temperature below that of autoignition. I have not yet found any reliable data for oxygen autoignition temperature for the environments concerned, but from what I found, it's probably above that of the aluminium's melting point. I have several NASA reports on the subject, and if you are interested and give me your e-mail adress, I can send them to you (my adress is ville -at- imorgon -dot- se.

There are also some interesting discussions on the aRocket mailing list regarding the issue in question.

Did you, or someone else for that matter, proceed with constructing any hardware using the Cu or Al regenerative chamber?

Sincerely, Vilhelm Jutvik

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/ldenies/OMECA/issues/1#issuecomment-301454779, or mute the thread https://github.com/notifications/unsubscribe-auth/AMQ3V_Zyi_ pIw6DgwW92tNIc3tBM7_Kdks5r6D56gaJpZM4Na5yr

.

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Dear Luka, I've had a good read of your Thesis and been delighted to look through your code. It has helped me to better understand the nature of the engineering challenges with regenerative cooling and given me the confidence to perform some of my own analysis.

Regards

Joseph

ldenies / OMECA

Question regarding your work #1