Draughting arrangements for Bulleid Pacifics including the Giesl ejector

Do you mind me commenting ?
As far as the Lempor is concerned, the whole approach is imho very unscientific, it has not gone through a process of public verification/falsification of its claims. It is now a thirty year old design with strictly maintained rules and challenge is not really accepted. As for the calculation, have you ever seen one?
Please note that the Lempor diffuser plus its mixing chamber is a very proper design and supported by fluid dynamics research. I am not so sure about the orifices shape, position and inclination and the length of the mixing chamber in a locomotive since no proof has been submitted.

As for the need to change, don't you take your car to the garage if its fuel consumption is high?
A poor front-end stresses the boiler unduly, so it is bad for the boiler, your wallet and the environment.
As an argument I would like to point at the 1933 research of Everett Young, it is online these days.
https://www.ideals.illinois.edu/handle/2142/4435
If you care to look at fig 16-a and -h you can conclude for yourself how much better his "pepperbox" blastcap result is
compared to the standard single. This is now 80 years old research and it is time it found some application.
Kind regards
Jos Koopmans

 

You are welcome! I have enough up my sleeve for a long time!
Kind regards
Jos Koopmans

 

I see a lot of theory and "would it be nice if" in this thread regarding draughting of locos in general and Bulleids in particular but what I don't see is the offer of someone (individual or group) to sponsor these "improvements" on a loco. Why should a loco owner or railway dig deep into their pockets and take the loco out of traffic for modification and road trials when there is no guarantee as to what the return on investment will be?

 

Another point is that in many cases locos are restored by their owners for enjoyment and we love 'em warts and all. I suspect the same goes for owners of other vintage hardware. I'm sure all sorts of planes, trains and automobiles could be "improved" but at the risk of taking away their character and thus the reason they were saved in the first place. I'm sure many of us would be interested in the outcome of any of the modifications suggested in this thread but I suspect it will need the talkers to become the doers.

 

Good points, however, if I were a locomotive owner I would bend backwards to do anything I could to prolong the
life of my boiler. After all, it is the most expensive piece of equipment on the frame.
"Theory" and "improvements", sorry, I don't buy that, hard facts within the UK steam locomotive fleet!
Kind regards
Jos Koopmans

 

Hi Jos,

Please can you enlarge on how the exhaust design relates to boiler life please? Iain

 

Consider an indicator diagram. If the bottom is lowered due to a lower blast pressure, the righthand side (expansion curve)
of the diagram can be shifted to the axis to keep the total area identical. This means that steam (and fuel) is diminished.
Since the life of a boiler is (among other variables) determined by the amounts of BTU's/Joules that are passing
lighter loads on the boiler prolong its life.
Kind regards
Jos Koopmans

 

I would add that in the Narrow Gauge community, where locomotives are expected to work at least as hard as they did in pre-preservation days, have different requirements to the standard gauge heritage lines.

A number of lines have undertaken re-draughting modifications over the last few decades - Ffestiniog, Kirklees, Welshpool and Talyllyn to name just a few, although some have involved a compromise for heritage appearance and spark arrestors. It is good that Jos Koopmans is commenting on this thread as his book has often been mentioned in reference to this work.

Kind regards,
Gareth

 

Okay, agreed on like-for-like duties although I'm not sure how significant the reduction in boiler wear would be, compared to the other factors at play there . I suspect the gains wouldn't justify the cost of the modifications alone, but could be added to fuel savings, if they could be quantified of course. It also assumes the owner doesn't want to utilise the extra performance the exhaust provides of course (that probably only applies to main line loco's).

 

I suspect that the cost of water treatment is somewhat mess than a redesign of the front end. And the important words are "tried and tested." AFAIK the only exhaust mods on the Bulleid fleet in BR days were the Giesl on 34064 and a single chimney trialed on an MN. We have had the Giesl on 34092 since of course. AFAIK pursuing the Giesl option is pretty much a non starter now so any exhaust mods would have to be of a different type. IIRC Mr. Koomans has suggested the reduction in diameter of a Light Pacific's chimney and modification to the nozzles in the blast pipe cap. My argument is that a guinea pig loco would need to be modified to test all the theories and projections. Someone would have to fund that. Also he remarked on making boilers last longer. We all want that bit given the nature of heritage steam, locos spend more time cold than in BR days and go through many more thermal cycles. With this in mind, I wonder therefore if having less hot gasses through the boiler would have a significant impact in the heritage sphere.

 

Im in agreement that this Fascinating subject ( creating vacuum by jetting gas up a tube) could perhaps have its own thread...
Regardless of 'Insubstantiated' or ' Non scientific' application there is little doubt that Lempor produces results which are evidently as good as / better than Kylchap/ Geisl / Le maitre... but perhaps this is because the people fitting them have given some thought to the Locos they were fited to and better judged the dimensions accordingly, as 242 a1 says has any serious thought been given to the precise dimensions of these systems in the UK( LNER Kylchaps/ SR le Maitre) since the 1930's ? I know that 71000's was resized at least once in preservation...

My wierd brain often comes up with odd questions and here is one

Pulses of higher pressure (gas) from a single nozzle = Circular mixing chamber / Chimney
if Passed instead through several Nozzles arranged in series (Geisl) = Series of overlapping circles = approx Rectangular Mixing chamber /chimney sorry, diffuser...
if Passed through 4 nozzles with one in the middle ( lemaitre) or 4 nozzles more closely spaced = ???? shouldnt it be a round cornered square ? at least at the mouth of the mixing chamber ?

Chuff.

 

Well, front-ends are over 200 years old and I am under the impression that almost anything has been tried or at least
specified in a patent application.
Imho let's stick to the proven changes. As far as the working of a jet is concerned, please note that the momentum of a jet is concentrated on its axis. In an ideal chimney, long enough, the momentum is transferred to the surrounding gases and the velocity profile at the chimney exit should be uniform, flat. In reality it is not, and when the loading gauge does not permit
chimneys long enough they have to be split up in doubles and further in units with 3,4 up to 8 orifices. In such a system each orifice can transfer its momentum properly since the relative length of the transfer path increases with the number of orifices as the chimney keeps its allowed height.
So, please do not start with fancy units, a four-orifice front -end is basically a combination of four half-scale models of a single orifice with a double(!!) length chimney, hence its improved characteristics.
Kind regards
Jos Koopmans

 

Slightly digressing; when I first visited the DDR in the mid '70's, the Deutsche Reichsbahn had a large proportion of its steam fleet fitted with Giesl Ejectors; including BR's 50, 50.35, 52, 52.8 & 65.10. By the time of my visit, the venerable Prussian locos, such as BR 38 & 78 had gone, but many of these had also been fitted. I am not aware of any of the more powerful locos, such as BR's 01, 03.10, 44 or 58.3 being fitted, although 01 504, 03.1010 & 18 201 (02 0201) were "one-off"'s. Was the Giesl only effective in the low-to-mid power range? On one of many subsequent visits, about 1979, I noticed that all the Giesls had been removed at a stroke (with the exception of 02 0201!). Was this merely an expiring licence issue, or was it concerned with performance?

 

Please note that the fastest steam locomotive in Germany, the 18201, has a Giesl and with 2221 sq.ft
evap. heating surface falls among the largest we are discussing here. Looking at the performance curve of
the 9F locomotive, it indeed falls off at the end (curves towards the horizontal). I concluded earlier that a Giesl
was choked at its throat, so that might be the reason.
As for the german decisions, no idea!
Kind regards
Jos Koopmans

 

It is interesting that the narrow gauge community is more receptive to the improvements that can be made to exhaust systems. The standard gauge community far less so. Remember the outcry when an owner of a GW 0-6-2t fitted it with a single Kylchap system. The majority are adamant that their precious charges do not need improving, worse they are convinced that there are no improvements that can be made, more justified is the view that as historic artefacts they should not be changed (apart from being in BR livery at all costs - just as they remember them).

Though the more efficient use of steam eases the load on the boiler and given the financial burden of boiler work you might think this alone might be sufficient leverage to drive the decision to include all the efficiency enhancements that could be invisibly incorporated in locomotives. Preservationists cannot fully agree on the advantages of correct water treatment.

The Lempor theory does give improvements. You can argue about public verification but those who make use of it find that it works and gives the best results available so far. It stands the test of physical application. Those who use it do not believe that it is the final word.

It would be a good use of time and resources to build another test rig so that the effectiveness of the ejector design could be re-examined and the impact of changes to those aspects of the design that cause a level of concern can be examined. Back to DW in China as it were, for those with unanswered questions.

The diffuser and mixing chamber are quite proper and well researched. The lack of height available for the installation of a single unit ejector of correct proportion on standard gauge locomotives is well recognised. Hence we have multiples.

The back pressure experienced in the cylinders should be the minimum that might be achieved. The current view on bast pipe nozzles is that they should be convergent/divergent but there is no measurable advantage to be gained from ovoidal section. The nozzle tips are set at the start of the mixing chamber - this was one of the results of the experiments carried out in Datong. In these experiments the ratio of chimney o.a.l. to mixing chamber diameter was 5.1:1 with the mixing chamber length: diameter being 2:1. This was the only chimney tested but it was felt to be representative of a well designed exhaust fitted to a large locomotive. From this chimney it was found that the optimum diffuser included angle was between 10 and 10.5 degrees. Other results examined swirl vanes, proper positioning of the Kordina wall, the superiority of multi jet nozzles. But it was only one experimental evaluation of the theory. You can understand if this is viewed as insufficient. But those who have wrestled with the calculations do reap a worth while reward in terms of improvements. And the steam movement is not exactly well endowed with research funds.

The theory is not defended blindly. Those who use it have the research prior to its creation to refer to and the advantage of more modern material (Kentfield and Barns). The theory might be criticised for making use of concepts that are no longer part of modern thermodynamics. However the steam locomotive is a most peculiar and not particularly modern creation.

 

242A1's posting shows why I have some difficulties with the Lempor approach, sorry! As for the Datong test results, nobody
in an academic environment would accept them, they cannot be verified independently as details about the test rig setup, testing procedures and results are lacking. I myself have great trouble accepting that forcing the gasflow from the tubes&flues downwards to the orifices and reversing them there by 180 degrees is effortless and the consequent inclusion of the estimated momentum of the now coflowing gases is a large questionmark for me.
Wrestling with the equations, I probably hold the world record in momentum calculations as I have recalculated all my available
Rugby data tests and several times at that. As Giesl included coflowing momentum in his approach, just like Porta does, I came
to the conclusion that his equation was flawed with the 9F data.
As for Kenfield and Barnes please note that this is about high velocity/pressure low volume ejectors and the text contains two applicable caveats. As we are discussing large volume low velocity ejectors here, the application of Kenfield and Barnes without proper justification and/or explanation is imho sloppy science and should be avoided.
I regard the Lempor highly, but its development and application is not served by loosily applying some theory and calculations. The horror example of the UP 3985 Challenger where the Lempor was a complete failure and quickly removed should serve a a fair warning, it will kill any development in the USA for the next 10-25 years.
Kind regards
Jos Koopmans