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Lempor Exhaust Nozzles
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Author:  Dennis [ Mon Jul 11, 2011 4:25 am ]
Post subject:  Lempor Exhaust Nozzles
Having read much about L.D. Porta's Lempor theory, David Wardale's book the Red Devil where Porta's Theories were put into practice vastly improving the performance of 2 locomotives converted.
My question is in regards to the nozzles themselves.
David Wardale suggests that the nozzle area have a ratio of 1.10 :1.
Am I correct in saying the area of the inlet diameter (at the base) is 1.10 and the area of the exit diameter is 1?
Author:  Dave [ Mon Jul 11, 2011 9:09 am ]
Post subject:  Re: Lempor Exhaust Nozzles
I'd suggest you explore the articles on Martyn Bane's web site (which includes a Lempor calculator) and read jos koopmans' excellent thesis "THE FIRE BURNS MUCH BETTER. "

Both have a wealth of information about exhaust designs and ratios, and expand on the Lempor.

dave
Author:  Nigel Anthony Hewer Day [ Mon Jul 11, 2011 3:13 pm ]
Post subject:  Re: Lempor Exhaust Nozzles
Porta says that the area at the nozzle base should be the same as the area off the four nozzles at the the throat. The 1.1 then gives you the area at the exit of the diverging section. (devide by four for nozzle area) This is all to do with super soinc conditions.

The nozzles I have made are slightly difrent and have only the chokes at 1.0, not the base area where the gas flows are designed to difrent principles related to exhaust pipes.

Note we are talking about areas of !.0 and 1,1, not diameters
Author:  Planeman [ Tue Jul 12, 2011 12:01 am ]
Post subject:  Re: Lempor Exhaust Nozzles
Dennis,

The most knowledgable person on Lempor exhaust systems is John Rimmasch of Wasatch Railroad Contractors. He has offered to make his expertise available. He frequently posts on this board.

Quote:
Many of you want to learn more about Lempor and other types of front ends. I am proud to say that my team has compiled the most extensive research on these matters. In fact, we even have un-published documents on the subject. Our study of this matter has been extensive.

We established last year a program on our web page where technical questions could be asked. Rather than having you go to our page, I am willing to bring the discussion home. I am hereby willing to have any question about front ends presented to us on RYPN. My staff members or myself will answer the questions. Further, when questions require some documentation, we will post that documentation on our web page for free downloading by anybody.

http://www.wasatch-rr-contractors.com

Quote:
Author:  whodom [ Tue Jul 12, 2011 8:50 am ]
Post subject:  Re: Lempor Exhaust Nozzles
Planeman wrote:
Dennis,

The most knowledgable person on Lempor exhaust systems is John Rimmasch of Wasatch Railroad Contractors. He has offered to make his expertise available. He frequently posts on this board.


I think it would be fair to caveat that statement regarding John with "in the U.S.". Nigel has probably built and installed more Lempor exhaust systems than anyone else alive.
Author:  Dennis [ Wed Jul 13, 2011 4:01 am ]
Post subject:  Re: Lempor Exhaust Nozzles
Thank you all for your replies.
I have used this exel spreadsheet calculator available from this website home.ca.inter.net/.../Lempor%20ejector%20calculator%20beta%201.1.xls to calculate an individual nozzle diameter of 37.826 mm (1.489 inch) assuming a 4 nozzle system for a locomotive that has a new boiler, but is a very poor steamer and possesses low smoke box vacuum even though we can find no smokebox leaks when tested.
My question about the nozzle ratios quoted by David Wardale of 1,10:1 relates to my excel nozzle calculation of 37.826 mm (1.489 inch). I pressume this diameter to be the exit diameter or 1 of the ratio and the entry to be 1,10.
Am I tracking in the right direction?
Author:  Nigel Anthony Hewer Day [ Wed Jul 13, 2011 1:48 pm ]
Post subject:  Re: Lempor Exhaust Nozzles
No, its the other way round. Its converging down to 1 ( throat )then diverging out to 1.1 (exit)

See books on terbines and jet engines. De lavel section
Author:  John E. Rimmasch [ Wed Jul 13, 2011 11:22 pm ]
Post subject:  Re: Lempor Exhaust Nozzles
Thank you all for the very kind comments and links to our web page. (by the way, we have a new web page format coming out in the next few days created by our great staff at Wasatch Railroad Contractors). I am by far NOT the Lempor exhaust expert in the nation. I actually credit Matt Janssen and Dave Griner for their expertise in matters all things Porta. Mr. Janssen was once an employee fo WRC and has moved on to his own ventures, Mr. Griner retired almost three years ago and is enjoying life in AZ.

The two have agreed to work with WRC in the future if Lempor projects become of interest to the industry. I value both Matt and Dave as trusted friends and mentors.

Now, as for the true expert in this matter, it is Sir N. Day who is already active in this discussion. It is of value to this discussion to note that the Lempor work that WRC has performed was done under the partial direction of Mr. Day, whom I have met while he was in Cheyenne a number of years ago. I have a deep and profound respect for Mr. Day and the work that he has done. In our steam industry I feel that there are a few people who have never been given the ample credit that they deserve for the work they have done. Mr. Day ranks high on my list of those who have not been credited as they should have. I can assure you that if the steam "who's-who" were sitting at the table right now and the question were asked "Who do we talk to about Porta and Lempor exhaust systems?" The answer overwhelmingly would have to be Day.

I am happy to add where I can, however, this discussion is in the best hands possible unless the other well know Porta fans and historians wish to join the discussion.

Kindly yours always,
Author:  Dennis [ Thu Jul 14, 2011 6:20 am ]
Post subject:  Re: Lempor Exhaust Nozzles
Thank you John and Nigel
I have read many articles on Nigels work the world over and in particular on Martyn Banes website. His fantastic success in improving the draughting on many and varied locomotives along with other associated benefits to the locomotives and to the steam fraternity in general.
I previously asked advice on this forum about crossed rod Stephensons valve gear on this loco to which I received a lot of valuable advice and from that advice action has been taken.
The next step is to try and improve its steaming.
The locomotive is a UK Built 0-6-0 Fowler Tank Builders No. 5265.
Cylinders 11inch x 18 inch stroke.
Boiler pressure of 165 PSI currently the safety valves are set at 150 PSI.
Grate area of 5.939 sq ft
Firebox heating surface of 39.269 sq. ft
115 x 1.5inch tubes.
Single blast pipe orofice of 72mm (2.8 inch)
2 size 119 Penberthy Autopositive Injectors
At half a glass the boiler holds 308 imperial gallons of water and up to water wedge another 354 imperial gallons, not a lot of steam space and not a lot of water over the crown either.
My Steam Experience goes back to 1967 when I joined the Royal Australian Navy in the Marine Engineering Department, steam era. I have been involved with steam ever since.
The Fowler loco only makes steam when standing still.
It pulls itself up when steam is shut off and when running down hill. Hopefully the Valve gear mods will eliminate this.
It only pulls 34-35 mm of water in a U tube manometer at full regulator and full cutoff
Put on an injector and the boiler pressure drops rapidly, I have overhauled a size 117 injector and intend to put this one on the loco because I believe the 119 to be too large.
The smokebox vacuum is of concern, I understand that 5 inches of vacuum at 75% cutoff should be a good starting point, so that is what I am aiming for, I think I should get 6.250 inches at 100% cutoff.
The blast pipe was set centrally to the chimney.
The chimney is 40 inches long and 11 inches in diameter.
Before testing the vacuum the smoke box was tested for air leaks, none were found.
From the excel calculator the best outcome I could get to give 6.250 inches of vacuum is a 16 inch x 8 inch mixing chamber.
A 37 inch long diffuser with a 10.750" Exit I.D.
Unfortunately the diffuser angle is less than the optimum 10 degrees because of the need to maintain the 1886 chimney.
I intend making a new blast pipe, of 4.5625 I.D. and 4 nozzles.
I intend to try and fit a Kordina.
However no matter how many options I tried in the excel calculator I cannot obtain the convex graph curve the document recommends so I think the solution it came up with is the best compromise
Author:  Dave [ Thu Jul 14, 2011 10:29 am ]
Post subject:  Re: Lempor Exhaust Nozzles
Compromise is the best you can hope for when trying to "fine tune" historic designs with minimal reversable changes. You will have no opportunity to alter the steam flow through the choke points and passages, redesign the combustion spaces by altering the firebox and boiler, etc. If you can turn this track-weight into a machine that can earn its keep however inefficiently given the needs of the railroad, you will have done a great service.

Please seriously consider writing an article for this web site about the project, the conditions, decisions, and evolution of your work - it would be of great interest to many of us.

dave
Author:  Nigel Anthony Hewer Day [ Thu Jul 14, 2011 3:57 pm ]
Post subject:  Re: Lempor Exhaust Nozzles
First check the folowing.
Check piston rings for wear. ( Bad piston rings can result in 50% steam wastage.)
Make sure there is no scaling of any boiler serface. ( Scaling can reduce heat transfer up to 60 %)
From the cylinder to the blast pipe the exhuast pipe should be 'Hot Roded' for good gas flow, gental bends, large gas flow section, smoth serfaces and so on.
The joining of the two steam flows should be as gental as posible and idealy spread the steam over the entire base of the blast pipe nozzle. Do not worry about copying the Kordina as in the 26. This exhaust pipe work is vital and must be done to make the relationship between the cylinder and blast pipe reactive. If there is a limiting point between the cylinder and the blast pipe then it must be identified and measured as it will afect the preformance and the blast pipe size.

Given some of the figures suplied the following is relivent.
The converging taper of the nozzle from exhaust pipe down to blast pipe throat should be no more than 10 degrees inclusive.
The total area at the throat should be 4.75 sq inches and divide by 4 for each nozzle,
If there is a parallel section at the throat area then it aids stability in the energy changes which ocurr at this critical point.
The diverging section should have an angle of 6 degrees inclusive and lead to a total exit area of 5.22 sq inches diveded by 4. At the exit of the nozzle the thikness of the wall should be as thin as practical around or less than 1/8 inch
The overal hight of the nozzles should be around 5 to 6 inches for this sized loco but will be defined later.

Please supply the following aditional info.
a) the internal diameter of the boiler tubes.
b) the length of the tubes.
c) the internal diameter of the blower pipe.
d) the altitude at which the locomotive will operate.

I will supply more detail later.

Please note I do not use the calculator mentioned to work out my Lempors. The latest build of Lempors can be seen on Martyn 's web page for the West Coast Wildeness Railway. Thank you for the nice coments but to me it's the locomotives which are more imoprtant and thier survival as working machines,
Author:  Dennis [ Fri Jul 15, 2011 4:58 am ]
Post subject:  Re: Lempor Exhaust Nozzles
Nigel, thank you for your interest.

Please supply the following additional info.
a) the internal diameter of the boiler tubes.
From Looking at the drawing the tubes are actually 38mm O.D with a wall thickness of 3.3mm so the tube I.D. is 31.4mm.

b) the length of the tubes.
The tubes are steel 2.4 metres long (94.5 inches).

c) the internal diameter of the blower pipe. Do you mean Blast Pipe?
The dimension at the base of the blast pipe is 4.5625” The dimension at the top of the blast pipe is 3.620”
The height of the blast pipe measured from the mounting flange to the exhaust nozzle is 25”, the flange thickness is ¾”. The nozzle height is 2.362”.

d) the altitude at which the locomotive will operate.
Pretty well sea level.

Some other smoke box details.
Diameter of smoke box is 44⅝” O.D. Plate is ⅜”thick.
Distance between the top of the top row of tubes and the inside of the top of the smoke box is 16½”.
The distance from the top of the blast pipe to the inside top of smoke box is approximately 11¼”.
The smoke box is 24” long.

I have photographs of the smoke box internals and of the exhaust passages taken from above the mounting flange if you want them.

The boilers internal surfaces are relatively clean, not perfect but certainly not as bad as some I have seen.
I have carried out a valve and piston test on the loco and both sides proved tight.

Nigel I think I was at Puffing Billy not long after the lempor modifications were made to loco 6A, unfortunately my footplate trip was not behind her, I have a good mate who is a driver there, he says 6A is certainly different.
I have seen the photos of the Mount Lyell ABT Loco smoke box internals and its lempor system, From what I am told less fuel, less water, a stronger free steaming engine.

I used the excel calculator because it took the mathmatical complex of Potras Theory and turned it into something I could understand, I not being mathmatical gifted, I was suprised to see something like this on net.

Between the Fowler Loco, the blacksmiths hammer and forge that I am installing I have very full working day when I visit the railway but if I didn't do what I am doing no one else wood. Most people believe the Fowler loco will never be useful but from what I have observed I don’t think they are correct.
Author:  Nigel Anthony Hewer Day [ Sat Jul 16, 2011 3:17 pm ]
Post subject:  Re: Lempor Exhaust Nozzles
Thank you for the info. I would like to continue this thread as long as posible on this site for genaral intrest and understanding. There will be a point where some drawrings and pictures will be of intrest but it will take the asistance of some one to get them on for me.

The info provided so far can now be evaluated to the boiler. The main conciderations of the boiler design are the heating serface and most importantly gas flow areas. A fundimental understanding of this can be got from a small book published by Lindsay in the late 1980's 'Getting More Steam'. It contains parts of the AAR reaserch and lists gas flow areas for a boiler. It uses the Gas free area (GFA) through the tube bundle as reference point for everything else. This for exsample then relates to the areas of screns and plates in the spark arrestors. There are many views on the relative grate size to the gas flow area of the tubes ushaly relating to the burning of difrent fuels. At this point we acsept that the standard coal combusion uses a grate to GFA of 14%.
The air gaps in the fire bars should not be less than 110 sq inches and around 138 is acseptable.

We find this boiler gives a higher figure of 16% so velocities through the tubes are not excessive.


The next concideration is the tubes and thier heat exhangingability. The best comparison is to check the A/S ratio ( The area through the tube agenst the heat transfer area.) The average sized loco has one between 1/250 and 1/300 For larger and smaller locos this can vary from 1/500 to 1/100.

We also find that this loco falls within limmits.

The actual determination of Lempor ejectors is more baised on heating serfaces, and evaporative rates. Beyond all conciderations the Lempor is about the concervation of energy and finding the best ways to eficently get the most out of the exhaust gasses and steam.

The calculations here give a mixing chamber of 7 inch Diameter and a hieght of between 14 and 16 3/8 inches. (I will work in metric if prefered?)

The next item will be to figure out the geometry of the nozzles and mixing chamber. This being best done on a dimentioned sketch (for next posting.)

Please can you confirm the blower or jet pipe bore. It is requred to be able to do the blower calculations which will give a defined 1.5 inches of vacuum. Thank you for the blast pipe stand dimentions which will be usefull also.

Dennis, I hope you can post a few of the pictures for every one to see and that you dont mind my desire to do this work publicly. We will get your engine going and make people eat thier words! I do prefer the locos which no one wants just to prove a point. Caladonia on the Isle of Man was such a loco and the result ment they actualy had a usable machine rather than just for show.
Author:  Dave [ Sat Jul 16, 2011 3:43 pm ]
Post subject:  Re: Lempor Exhaust Nozzles
[quote="Nigel Anthony Hewer DayDennis, I hope you can post a few of the pictures for every one to see and that you dont mind my desire to do this work publicly.[/quote]

Yes, Please........very helpful for many of us reading with interest.

dave
Author:  Nigel Anthony Hewer Day [ Sat Jul 16, 2011 3:53 pm ]
Post subject:  Re: Lempor Exhaust Nozzles
I hope there is some one in cyber space who can help convert and post my J peg files up please
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