Front End situation

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Re: Front End situation

Post by JJG Koopmans on Sun May 26, 2013 10:14 am

Hi,
I can show my way of thinking. My experience with oil is nil, we don't have any in the Netherlands and I want to stay as far as possible from waste oil. So this is coal based. The above drawing says heating surface 646.75 sq.ft. From the British Railways tests Ell derived his formula for the orifice diameter d=1.128 square root(9.5+0.0059) inch which works out at 4.12 in. This compares nicely with drawing 57.2394 above. The narrowest throat possible would the be 2.85 this number or 11.75 in. It is 15.125 which I regard as too wide, but we are discussing 1926 standards. The orifice appears too have had a bridge, so it had already the earliest attempt at a multiple arrangement.
Refining this into a four-orifice arrangement, the "fence" around the area for improvement appears to be approached by the easy formula "area increase is third root of number of orifices" which is 1.587 for 4 orifices. Diameter wise it would be the square root of that number which is 1.26 meaning that the orifices could have the equivalent diameter of 1.26 times 4.12 or 5.19 in. which is four orifices of about 2.5 in. Remainder standard: distance x from orifice to chimney throat 6 orifices distances, 15 inches. Width of throat 2.85 x equivalent diameter 5.19 or 14.79 in., so now the chimney entrance is wide enough. If it were a proper diffuser the chimney should be widened by length 42 times the tangent of 5 degrees, about 3.67 in. of its top radius.
That is what I can make of it, please note that this is under the strict condition of equal power for single and multiple arrangement! No more cars, no increased speed!
Food for critisism isn't it?
Kind regards
Jos

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Re: Front End situation

Post by Overmod on Sun May 26, 2013 11:06 pm

At this point Hugh might start modifying the side elevation drawing to show the effect of some of these suggestions. For example, widening the chimney at the top by Jos' 7.33" diameter, and showing the exhaust-steam piping to heaters and so forth...

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Re: Front End situation

Post by Low_Water_Odom on Mon May 27, 2013 10:02 pm

Overmod wrote:At this point Hugh might start modifying the side elevation drawing to show the effect of some of these suggestions. For example, widening the chimney at the top by Jos' 7.33" diameter, and showing the exhaust-steam piping to heaters and so forth...

I'll try to get some drawings up this week. We have Jos' post above and Nigel has sent a sketch for both a "compromised" Lempor (to fit within the existing stack) as well as an "uncompromised" Lempor (which would require a new stack). That'll give us something to see.

In case you didn't find it, Dave started a separate thread about the NHVRR's other locomotive, Vulcan #17, an 0-4-0T. The thread can be found here: http://cliffside110.forumotion.com/t21-let-s-look-at-17-a-bit

This locomotive is currently in operation and is having some trouble making steam at full load. This locomotive is the perfect pilot project for exhaust system work since it's already in service and urgently needs some improvement.

Hugh

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Re: Front End situation

Post by Michael Guy on Thu Jun 13, 2013 10:53 pm

Hi guys. Sorry for my tardy arrival to this. I have been trying to catch up and read all the correspondence. I completely agree that the existing stack is a dismally inefficient diffuser if one is trying to make a proper Lempor.

Anyway taking the stack as a given and plugging the numbers into the Lempor calculator sheet for a 15mph top speed at 35% cut-off I get a mass flow of 1.632 kg/sec (216 lb/min) which results in 4 nozzles of 2-1/16" diameter, the throat is 15" dia and a smokebox vacuum of about 10.4 inches of water should result. Maybe.

I have no experience of oil firing on standard gauge but on 42" gauge with the little 0-4-0 at Huntsville and on a big 7-1/4" gauge 2-6-0 we run in Toronto, both engines don't want a lot of draft. Just enough pull to move hot gasses through the boiler without dragging in too much cold air does it. It may be that trying for fancy draft is the wrong approach here perhaps just shooting for lowest backpressure will be the right answer in the end.

My 2 cents, fire away.

Michael.

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Re: Front End situation

Post by JJG Koopmans on Fri Jun 14, 2013 6:53 am

Hi Michael,
I have some doubts about your steam mass-flow. The above drawing says that the heating surface is 646.75 sq.ft>60 m2. Your 1.632 kg/sec amounts to 5875 kg/hr or 98 kg of steam per m2. That is very high, the Germans used 57kg/m2 and here in the Netherlands 65 kg/m2 was used. That 98 number is present in Chapelon and Porta publications on high performance engines.
Kind regards
Jos

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Re: Front End situation

Post by Michael Guy on Fri Jun 14, 2013 9:46 am

Jos, the spreadsheet calculates from engine geometry and speed with inputs for pressure at cylinders etc. It assumes the boiler can generate the required steam quantity. That sheet at last count has been downloaded several thousand times and I can't help but think that if there was a significant math error in it somebody would have pointed it out by now.

Leaving that aside, my inputs were as follows:

Cylinder dia 16" (406mm)
Stroke 24" (610mm)
Wheel dia 44" (1118mm)
Cut off 35%
Road speed 15 mph (24 Km/Hr)
Boiler pressure 200psi (1.3789 MPa)
Admission pressure 85% BP
Admission temperature  375F (190.7C)
clearance volume 10%
Volume from point of compression to end of stroke 15% of swept volume
Specific volume of steam at admission 2.40751 ft^3/lb (.154229 m^3/kg)
Initial pressure of compression 19.6psi (.135MPa)
Specific volume of steam at initial pressure of compression 12.14 ft^3/lb (.757 M^3/Kg)

This all comes out at 12,313lb/hr (1.5514 Kg/Sec) at the bottom of the steam rate sheet. (This is a different number because I changed that last value to .757 from 1.28 to agree with the steam tables).

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Re: Front End situation

Post by Overmod on Fri Jun 14, 2013 10:33 am

Just as a check:  110 is saturated and will probably remain saturated.  How much does the mass flow have to increase to overcome the effects of "excessive" condensation (wall and nucleate) under these conditions?

Also: the mass flow may be 'artificially' high because the cyclic rpm is relatively high with the small drivers.  That is what I suspect Michael's calculator is showing, although I have not made any calculations to check.  It is possible that with more precision in valve drive and valve events the engine could be made to run reliably at shorter cutoff, and reduce the mass flow per unit time, without introducing increased slip propensity or torque 'peakiness' -- but this may be an issue better taken up in the valve-gear/running-gear thread (with reference back here as needed).

Is anyone approximating a recursive set of FDCs on this design?

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Re: Front End situation

Post by DaveLathrop57 on Fri Jun 14, 2013 10:35 am

Michael, please link back to your spreadsheets for the people who are not familiar with your work.

Dave

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Re: Front End situation

Post by JJG Koopmans on Fri Jun 14, 2013 11:10 am

Hi,
I did a quick check on the numbers, my probably incorrect steam consumption calculations shows something in the order of 5000 kg/hr. However I threw the numbers into Prof. Hall 's Perform program and it came out as 12000 lbs/hr so Michael must be correct.
My conclusion would be that the boiler is not capable of supplying steam for 35%C.O. and 15 mph.
Btw Hall says that indicated T.E. would be 14100 lbs, what is needed for the train at  15 mph? If it is less the cut-off could indeed be diminished.
Jos

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Re: Front End situation

Post by Michael Guy on Fri Jun 14, 2013 11:54 am

Dave,
The complete Lempor Ejector Calculator can be found here: http://home.ca.inter.net/~mguy/lempor_ejector_calculator_page.htm

Also here: http://www.trevorheath.com/livesteaming/Lempor.htm

Martyn references it here: http://www.martynbane.co.uk/modernsteam/modernsteamlocos.htm but one of the links is out of date.

Michael.

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Re: Front End situation

Post by DaveLathrop57 on Fri Jun 14, 2013 12:03 pm

Gentlemen, based on the performance of 17 I think we can run the majority of the line with a low cutoff, and drop her down to make the climb out of the creek bed into the yard. 110 is larger and has slightly more TE than 17......and vastly increased boiler capacity.

Current thinking (subject to change as we evolve this process) is to sleeve the cylinders for adhesion purposes to about 15.75" and set the operating pressure at 180 PSI, which Vulcan used originally, although the boiler the built was to a design for 200 PSI at a factor of safety of 5. Once we're further along we can combine a lot of parts together and work out the optimum arrangements as a whole.

Dave

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Re: Front End situation

Post by Michael Guy on Fri Jun 14, 2013 12:09 pm

Jos, yes that is the inescapable conclusion, this loco was built to slog along at slow speed with lots of starting tractive effort but no ability to run particularly fast.

If I reduce the cut off to 25% the consumption drops to 1.162 Kg/s and keeping everything else the same the throat diameter comes down to 12.8" and nozzles go to 1-3/4". This begins to look like something that might fit inside the existing stack and might have a somewhat improved diffuser shape.

Michael.

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Re: Front End situation

Post by DaveLathrop57 on Fri Jun 14, 2013 12:15 pm

Logging locomotives hauled heavy trains on light temporary tracks from large stands of timber being cleared to a permanent mill. The speeds were slow, beacuse of a very roughly laid track - when the timber was cut, the track would be removed and relocated, so a lot of care wasn't taken. Michael's understanding is historically correct. remember that geared locomotives did a lot of logging.

Dave

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Re: Front End situation

Post by JJG Koopmans on Fri Jun 14, 2013 2:30 pm

Looking at another spreadsheet it appeared that a 300 ton train moving at 15 mph needed only some 2000 kg(f) TE. It is my understanding that in such a condition train crews do leave the Johnson bar in forward position and drive on regulator only.
This is in its own right almost identical to low cut-offs, however the higher cut-off gives less losses at the ports and at the same time throttling on the regulator valve gives some superheat!
Jos

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Re: Front End situation

Post by Low_Water_Odom on Fri Jun 14, 2013 10:40 pm

Gentlemen- I haven't checked in for the last several days.  I've been working on drawings for the 110 which I'll post tonight.  (These aren't the absolute best quality- I did them with an old free CAD program which is somewhat limited in its capabilities.  I can update these drawings on a proper copy of Autocad if needed.)  

Nigel gave us his design for a "compromised" Lempor with a "liner" to fit within the original stack and a "proper" Lempor which would replace the original stack with a new one.  I wanted to show how those compare with the original design.  I'd also like to draw Jos's idea for an exhaust design for comparison.

First up is the "as-built" exhaust configuration.  I understand all the parts inside the smokebox are actually missing from this engine, but it shows us how the locomotive was originally equipped (and the condition in which it worked for ~45 years).



The drawing is approximately to scale.  Note that the petticoat is adjustable both for length and vertical position in the smokebox.  More details are shown in the original construction drawings if you're interested.

Hugh

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Re: Front End situation

Post by Low_Water_Odom on Fri Jun 14, 2013 10:46 pm

Next up is the "compromised" Lempor- the outlet diameter and taper of the diffuser section are limited to fit within the confines of the original stack.  A few of the dimensions shown don't exactly agree with the ones supplied by Nigel.  For instance, the CAD program measures a slightly wider diffuser angle than Nigel gave and the height of the diffuser section is about 2 inches less than Nigel's measurement.  This was necessary to maintain his other dimensions.  Nigel supplied us a "back of the envelope" design done on the fly while he was traveling so that likely explains the very minor discrepancies.  (Either that, or my CAD program has gone wonky!).

The Lempor nozzles themselves have been "eyeballed" and are not necessarily correct.


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Re: Front End situation

Post by Low_Water_Odom on Fri Jun 14, 2013 10:52 pm

Finally, the "true" Lempor to Nigel's drawing.  Again, I made some minor changes to his dimensions to make it fit.  The stack base is intended to be similar to those used on other full Lempor systems.  Same caveat applies as above regarding the exhaust nozzles.


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Re: Front End situation

Post by Low_Water_Odom on Sun Jun 16, 2013 7:22 pm

OK, I'm working on a drawing based on Jos' description of his ideas for an improved exhaust system.  

Based on Jos' post, the exhaust would have a diffuser section which is 42 inches high (to match the original), 14.79 inches inlet diameter and 22.13 inches outlet diameter [14.79 + 2(3.67) = 22.13 inches].  It would have four nozzles each 2.5 inches in diameter, and the distance from the nozzle outlets to the chimney throat would be 15 inches.

Jos- I assume there would there be a parallel section prior to the diffuser; how long should it be?

Thanks,
Hugh

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Re: Front End situation

Post by JJG Koopmans on Mon Jun 17, 2013 6:55 am

Hugh,
The parallel section could be 2 times its diameter and since I position nozzles below its entrance, it may be slightly shorter to make it fit. Please use a rounded entrance.
Kind regards
Jos

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Re: Front End situation

Post by Michael Guy on Tue Jun 18, 2013 6:46 pm

Gents, some doodling in spare time at work has produced the following numbers. I think I have this right but no guarantees, corrections welcome of course.

I am ignoring the original stack just to see what it all looks like done from scratch.

Version #1 below has the usual 1:4 (areas ratio) tapered diffuser stack typical of a Lempor but at 42" it didn't return a very good Cp number, only .6. Version #2 I changed the taper to get a (slightly) better Cp of .65. Still some way from Porta's ideal .8 to .85 but the best I think we can get in the allowed 42 inches of height above the smokebox. It may be that the whole thing could/should be dropped down to get more length but it would need to be eight feet long to get past a Cp of .75. This steam rate is still playing with the numbers from the mechanical end. If someone wants to estimate the boiler output capacity in lb/hr I can re-design for that and see how it compares.

MJG Lempor #1

10km/hr
60% cut off
Mass flow 1.051 Kg/s (8,300 Lb/hr)

Choke/mixing chamber = 10" dia (254mm) (area: 78.5 sq-in)
Length 20"
Diffuser top @ 4X choke area = 314 sq-in = 20" dia (508mm)
Diffuser length 42" (1067mm)
Diffuser angle 13.6 deg
NDL (42/5) 8.4
Diffuser Cp: ~ .60

Nozzles (4) = 1.6" dia (make them from 1.5" dia pipe)
Nozzles angle 6.8 deg
Total exhaust nozzle area: .00511 m^2 (8 inch^2)
Smokebox vacuum ~ 16" H2O

Note: Using Porta's ideal 1:4 diffuser in/out ratio does not return the best Cp at only 42 inches high.

MJG Lempor #2

(Same speed & cut-off & Mass flow)

Choke/mixing chamber = 10" dia (254mm) (area: 78.5 sq-in)
Length 20"
Diffuser top @ ~ 2.5X choke area = 198 sq-in = 15.87" dia (mm)
Diffuser length 42" (1067mm)
Diffuser angle 8 deg
NDL (42/5) 8.4
Diffuser Cp: ~ .65

Nozzles (4) = 1.58" dia (make them from 1.5" dia pipe)
Nozzles angle 4 deg
Total exhaust nozzle area: .00504 m^2 (7.8 inch^2)
Smokebox vacuum ~ 17" H2O

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Re: Front End situation

Post by DaveLathrop57 on Tue Jun 18, 2013 8:28 pm

I'm going to need to make a longer manometer.........

Just for fun, I'll see about getting some interest in trying the manometer we have out on 17 to see what kind of vacuum it draws. Given it hhas the same installation as Vulcan designed for it, we can probably figure it as being ballpark as good as the Vulcan design for 110 would be.

Dave

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Re: Front End situation

Post by Michael Guy on Tue Jun 18, 2013 8:49 pm

Dave, are the leading dimensions for #17 posted someplace convenient?

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Re: Front End situation

Post by DaveLathrop57 on Tue Jun 18, 2013 11:18 pm

Yes they are, Michael......you can find the link in the #17 exhaust system thread, or in the links images and drawings thread, forgot which.....norser.net. The 17 drawings aren't as clear as the 110 batch, but are fairly legible. Please ask if you need something that isn't clear.

Good news is there's some serious intent in the works for doing vacuum and back  pressure measurements on 17.....soonish.....which could lead into electronic digital indicator diagramming and recording down the line a bit further. One of our guys is an engineering student and has access to some equipment for the job.

So, we might be able to work up a front end for 17 that we can use to test proposed systems for 110 in slightly smaller scale.

Dave

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Re: Front End situation

Post by Michael Guy on Tue Jun 18, 2013 11:25 pm

Dave, I did look at the drawings but have limited ability to pore over them during a long week at work and I didn't see a cylinder drawing. I need bore, stroke, wheel dia, smokebox dia, BP. Thanks.

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Re: Front End situation

Post by Low_Water_Odom on Wed Jun 19, 2013 6:52 am

I have a drawing of the stock smokebox arrangement for #17 done; I just need to dimension it.  I'll try and post that this morning.

Hugh

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Re: Front End situation

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