Draughting arrangements for Bulleid Pacifics including the Giesl ejector

Hello Mr Koopmans,

Welcome to this forum. I, for one, am honoured to be rubbing shoulders with you - metaphorically speaking.

Regarding the Bulleid-Lemaitre exhaust system, have you actually produced any calculations/drawings for the redesign that you refer to? I'm sure that there would be a great deal of interest here in any input that you may be able to provide. Most certainly the Light Pacifics could benefit from a "re-tune" at the front-end, the performance of 34092 demonstrates what can be achieved.

Cheers

Alan

 

Yes, I actually have! In 2006 I published a book (2nd printing available from Camden) which
has the calculation showing that a decreased diameter chimney and orifice to chimney distance
decreased resulted in an increase in the 5 orifices from 66 to 88 mm with half the backpressure.
Please note that there is a very proper rationale for these modifications which is why I regard
the present front-end as improperly dimensioned.
Kind regards
Jos Koopmans

 

Indeed Martin, steam production for any Bulleid can certainly be described as more than adequate. As for fuel consumption, any savings there would, I'm sure, be seen as a bonus. However, savings in water consumption may be seen as just as important, particularly on the main line; a case in point is the run with 46115 on Sunday last, apparently, diesel assistance was called upon to save water, I wonder if diesel assisted water saving is a regular occurrence.

Cheers

Alan

 

Many thanks for that Mr Koopmans. On a personal basis, I am certainly very interested in the development of steam technology, I will be looking up for a copy of your book from Camden in due course.

The modifications that you outline for the ejector/chimney certainly - from my point of view - fall within the realm of very do-able, I wonder if any of the various Bulleid owners are willing to take up such mods and test the loco accordingly, it would make for a very interesting exercise.

Cheers

Alan

 

Well, it is certainly do-able and well within the reach of volunteers. Since it is already available
as a suggestion since 2006, I am wondering why it has not been tried. It would have a huge
payback in coal and water savings.
As for the reasoning, anyone that is familiar with the works of S.O. Ell knows that for each lb
of steam about 2 lbs of combustion product (incl. excess air) should be exhausted. Looking
at the momentum of the exhaust jet, its mass times its velocity, it should be clear that the velocity
of the mixture should drop to 1/3 of that of the steam. As a consequence we have to move
3 times the steam at 1/3 of the velocity, as a consequence the "hole" through which it is pushed
should have 9 times the area of that of the orifice(s). Looking at the Bulleid chimney it is larger,
meaning useless excess air! As for the distance between the orifice(s) and the chimney, fluid
dynamics has a formula these days for the entrainment ratio, as a consequence 6 to 7 orifice
diameters from the orifice half the combustion products are already entrained. However
at over 9 distances all of the combustion products are entrained so there remains very little
for the chimney to do. The Bulleids fail on both counts, so an improvement is really easy.
As for the steaming capabilities, these boilers are reputed to be excellent steamers, of course that
feature should be retained, however with far less effort!
Kind regards
Jos Koopmans

 

Many thanks for your explanation Mr Koopmans, it certainly clarifies - for me at any rate - how a potentially large improvement can be achieved for a relatively small outlay in money/time/materials. However, convincing the various loco owners could be a bit of a mission. 34092 and it's Giesl notwithstanding, British railway enthusiasts/preservationists can be an insular and parochial bunch at the best of times, however, I for one one, would be delighted to be proved wrong and look forward to at least one other of the fleet of Bulleids benefiting from a front-end tune-up.

Cheers

Alan

 

Thanks for Joining our little discussion Mr Koopmans, I havent read your book/ papers but it has been mentioned in several articles from the '2nd generation steam' community ( so maybe i should).
Look forward to your insights.
Have you ever ran your slide rule over the Kyllchaps on the LNER pacifics ? these were also 'a one size fits all' but since the cylinder sizes and Boiler pressures were all fairly similar the results suggest the size is a reasonably good match ...

 

A number of heritage locomotive owners are of the conviction that their locomotive is frozen in time!
However, almost nothing remains of the locomotive when new, so I regard it as an incorrect
argument. What amazes me most is that somebody is covering the huge cost of coal!
Kind regards
Jos Koopmans

 

Well, I am using a pc since 1987, so my slide rules lies unused in my drawer. I have looked at the LNER Kylchaps, but since they were not tested by Ell I have too little data on them. I noticed however that their orifice area doubled after the Kylchaps, so it was a nice end for my "improvement fence": area increase is third root (no. of orifices): 8 orifices from the double
Kylchaps would make a double orifice area possible.
Kind regards
Jos Koopmans

 

Welcome to the mad house - I mean forum, a sincere welcome.

The original front end is capable of improvement, but aiming higher than parity with the Giesl ejector should be the order of the day. Our preserved locomotives need all the help they can get since life for these engines does not get any easier particularly if access to the mainline is part of operating life

 

Well, I am tempted to accept the challenge! I have been in the lucky position to be able to study the BR9F Giesl tests in the
NRM archives. As far as I know the CofW unit is identical, but may use a different (to me unknown) area. The tests with the 9F used a total orifice area of 19484 mm2, while I, with the 5 orifices of 88.6 mm each, get a total orifice area of 30896 mm2. Just for the record, there were no calculations by Giesl in the archive box and I have been trying to get the test results to match the momentum equations as proposed by Giesl. It was a fruitless exercise and my conclusion is that Giesls theory is flawed, although his units worked. It may sound cheap, however, we are 70 years further in time and have learned a little extra!
Kind regards
Jos Koopmans

 

Reading David Wardale in his book - The Red Devil - he came to a similar conclusion regarding the Giesl Ejector after researching the fitment of one to a 25NC in South Africa.

An interesting side effect of the Giesl fitment to 34092 is the much sharper blast from the engine, a by product of a smaller cross-sectional area perhaps?

Cheers

Alan

 

Interesting remarks regarding Bulleids and possible modifications to the draughting to improve coal consumption but it's not the owners who pay the coal bill. No idea of what the costs would be but why would a loco owner spend money on what is as yet an unproven idea just to save someone else some money? The people to convince are the railways who may want to fund such modifications to save them money in the longer term. It would seem however that in the SVR's case at least, a Bulleid is not the most expensive loco to run.

 

Yes indeed, the piper and the tune. But, how is the fuel funded on main-line engines? is it an extra or is it a bundled cost with the loco? Also, as I mentioned earlier in the thread, water consumption may be an issue, particularly on the main-line. As for an unproven idea, the performance of 34092 since modification speaks for itself. An alternative to a Giesl Ejector? I do believe that the modified exhaust on 71000 transformed the loco and what is being discussed here is not too dissimilar, but optimising an existing arrangement . Coming back to 34092, I would be delighted to find out what motivated Richard Greenwood and his team to modify that particular locomotive back in the 80's, there must be an interesting tale to tell there.

Cheers

Alan

 

A good question that hopefully somebody will answer.
Wasn't suggesting a Giesl ejector was unproven but the suggestion of modifying a Bulleid chimney to reduce the free air.

 

For those unfamiliar with Meneer Koopmans, he has written a PhD on locomotive exhausts - a copy resides upstairs as a Christmas present for my Father:

http://www.camdenmin.co.uk/products...ter-second-edition-to-be-published-late-april

 

If "unproven ideas" were an issue we would not even have steam locomotives wouldn't we? The last 100 years of front-end research including that of Ell has shown that a proper front-end has a number of dimensional ratios that can only be changed at a price. If this would not be true, please explain the far larger orifice size of the BR71000 DoG which has an almost identical
boiler. Imho it is also a problem for the owner, the unnecessary heat flow through the boiler will certainly not prolong its life. It is interesting to read that there are more expensive loco's running, which ones? I am very curious.
Kind regards
Jos Koopmans

 

You will have to refer to the gentleman who posted what he said was a year long trial by the SVR.

Edit : Sorry, that was in another thread but he said that a year long survey of coal usage had shown 34053 to be more economical owing to the steel firebox retaining more heat than a copper one.