Draughting arrangements for Bulleid Pacifics including the Giesl ejector

It would take some serious digging to confirm one way or the other, but the Giesl on the the 9F's were fitted to give similar 'Power' (draught) as the newly introduced Ell double chimney and iirc the trial was intended to demonstrate the Efficiency of the ejector (which it did but not spectacularly so) and the ability to utilize crap coal ( which it didn't, because the grates weren't adapted and the coal was really crap). The Giesl fitted to City of wells was sized with that particular locomotive in mind and configured (one would expect) to give a stronger draught and a lower back pressure. For it to be same size as the 9f Giesl would surely be co incidence guided by the similar boiler/ grate sizes on the respective locomotives.

Because there are several Bulleid light pacifics in either form they do offer an opportunity for comparison that would only be available with a few other classes of Locomotives doing mainline work (A4's, Black 5',s Jubilees, Castles)
To tamper With an A4 would lead to some kind of excommunication, or lynching ( and by accident or design the draughting is good)
Everyone knows castles are perfect (ahem.) and in any case the change to the appearance of the classic English 4-6-0 is very noticeable.
The original Condition Bulleid Pacific is one of the few where the appearance of the chimney is discreetly hidden, and the rebuilt is one of the few designs where a lempor could be fitted with no visible external change...

A hot debating topic at the Clan Project is how far to go with a draughting Mod. Clearly the original, and even modified BR dimensions we're not quite there but intuition suggests that a Britannia + sized single or a double about the same dims as a rebuilt Scot would be required to get anything like an optimum... quite different from the distinctive Fowler esque tin pot they started with.

 

The Clan Project is the next in the series and is not a reproduction of all that went before so all manner of things are open to development. The exhaust system can be optimised - how you dress up,the exit areas is a minor detail.
You can throw in multi-ring valve heads the Porta/Wardale low leakage style, GPCS, just about any improvement and it would have a validity.

The Bulleid Pacifics in their original form could hide no end of exhaust improvements.

The A4s are double chimney anyway, if someone as prepared to dabble who would notice? Interestingly the GW inspectors were hugely impressed with these engines - they would easily steam against both injectors regardless of the demands made on them. It does make you wonder what they might achieve fitted with a truly scientific installation.

 

Just a quick reminder, the 5AT Group are currently working with The Clan Project, looking into the feasibility of a range of improvements including those mentioned above. We would also be happy to talk to any Bulleid owners regarding modifications to the exhaust system, following the successful application of our Lempor to the KWVR S160, should they so wish. Please PM me in the first instance. Iain

 

As far as I know both the 9F and the CofW Giesl were just standard German Baureihe 52 versions. The 52 has 1914 sq.ft of
evaporation area, the 9F 2015 and the CoW 2122, so there were possibly only adaptations for the mounting below and the size of the oblong chimney. I can't remember whether mounting details were in the archive box at NRM and the KWVR people should know the details of their Giesl.
kind regards
Jos Koopmans

 

Maybe that would be a good idea to finally evaluate the Lempor against other solutions and modifications. Something
Giesl-Gieslingen already suggested in his book of 1986!
Kind regards
Jos Koopmans

 

Regarding Giesel's, one of the oft-quoted advantages is the ease of 'tuning' using a sliding shutter across the in-line nozzles. I don't know if this was used in the case of CoW at all? However, the Giesl nozzle does not compare favourably with other 'modern' exhaust systems when it comes to back-pressure at the cylinders, and any throttling using the 'shutter' would only exacerbate this.

 

It probably was. Regarding the Giesl, in an earlier post I explained why there is a rather fixed relation between the diameter of the chimney throat and that of the orifice. In the fluid dynamics manual on ejector design ESDU 84029 and 85032 that is
translated in "fluid dynamics language" as designing for the same Reynolds number for the orifice and the chimney throat
and is regarded as a must. Giesl does not comply with this, his throat area is smaller than required since he used a concept
called "shock loss" which cannot even be found in fluid dynamics textbooks of our days, so I cannot properly explain it to you.
Basically he more or less "flogs" the combustion products into his chimney.
Kind regards
Jos Koopmans

 

By coincidence, the new chimney and petticoat for 34072 257 Squadron were being fabricated today.

https://picasaweb.google.com/116839141471298057728/25Restoration2014#6081671804346503554

 

Historically accurate!
Kind regards
Jos Koopmans

 

One of the readers drew my attention to the test report of the MN class by BR. Thanks! If you are interested
it can be downloaded from here:
http://www.fini.net/~bersano/english-anglais/BR-tests/
Reading it I was struck by the third paragraph from the bottom on page 9: it was found that the MN coal
consumption was 15-20% larger than the average found on BR. So of the 5 tons of coal on the tender close
to a ton appears to be wasted, is it that affordable?
Kind regards
Jos Koopmans

 

I assume that was a typo for Bulletin 10, and you can't be reading it correctly. Graphs 6 and 8 show the lowest rate as about 3 lb per dbhp hour. For 1000 HP (moderate for a pacific) 16 lb per hp hr would mean 16000 lb or about 7 tons per hour.

Edit: or was "coal" another typo when you meant "steam"?

 

Let me quote verbatim from the report:
"..The specific consumptions of steam and Blidworth coal per I.H.P. hour are shewn in graphs 37 and 38. The former of these shews that the lowest specific steam consumption of the "Merchant Navy" is just under 15.9 lb/I.H.P.hr. against figures between 13.2 and 13.8 for a variety of comparable locomotives, i.e. from 15 to 20% higher..."
(con'd).. The specific coal consumption is increased in a rather greater degree since the minimum specific steam consumption of the "Merchant Navy" occurs at a relatively high steaming rate at which the boiler efficiency is lower"...

This should make it clear
Kind regards
Jos Koopmans

 

We are discussing the pro's and con's of different system here. I do not know whether any of you are familiar with the publication "Improving the Draughting of Steam Locomotives" in The Railway Gazette of March 20, 1959
In there Giesl (or his ghost writer) compared the performance of a Jubilee at a steaming rate of 20.000 lbs/hr with different front ends. There is a graph but let me just give the numbers:
conventional front end|| improved single chimney|| improved double||Bulleid||Giesl
Pumping hp 238 || 196 || 143 || 165 || 78
vacuum in. H2O 3.66 || 4.2 || 4.64 || 4.4 || 4.95
Back pressure 6.35 || 5.16 || 3.56 || 4.2 || 1.8 (lb./in2)
The first three columns are from the Jubilee reports, the Bulleid is a Giesl calculation based on
the BR reports and the Giesl shows the performance as given by Giesl.
What makes this interesting is that according to Giesl the Bulleid has a poorer performance than
the double, theoretically a 5 orifice system should perform between a double and a sevenfold like the Giesl.
What makes it more interesting is when the data is added that Powell gives in his book "Stanier 4-6-0s at work". Apparently a double Kylchap was tested on 5684 and his fig. 7 shows that for the vacuum data given under the improved single, the Kylchap only needed 1 lb/in2 as backpressure.
The conclusion in the publication ( and in his later book Anatomie der Dampflokomotive) was of course that the Giesl was superior which is very easy if conflicting information is disregarded.
Maybe it is also a lesson for us to realise that we should base our conclusions on numbers and not on opinions.
Regarding the test with the 9F, Giesl wrote a (german) article in Technikgeschichte of 1972. Apparently BR had rejected an offer from Bleckmann Schoeller for 4 free Giesl ejectors and Parliament intervened! Hence the 9F test.
Kind regards
Jos Koopmans

 

Misunderstanding! I wasn't suggesting typos in the report (though for all I know there might be some). I was suggesting that YOU made a typo in post #71 when you referred to COAL consumption of "about 16 lb per hp hr". Steam/water consumption is of that order, not coal.

 

Is the Giesl used on 78022 suitable for other locos?

 

Giesl being selective in his use of available data was just one of the reasons that I directed my attention elsewhere. Also the Giesl/Giesl family attitude to the ejector compares well with that of W. M. Smith's executors and is in marked contrast to that of LDP.

The Lempor is not perfect but the people involved in applying it have made their calculations, have run their applications through tests and have even produced a test rig in order refine and confirm details of the ejector's performance.

But the system is not an end in itself but rather another step along the way. The Lemprex may be the next.

Ideally each locomotive design should have an specific exhaust system designed for it. But this is not always the case. Take the LNE Pacifics and the V2 Class. But these were far more similar than the MN and WC classes. The one size exhaust system is not the best system on offer by current standards but is better suited to the larger design.

The question is do we really need to change anything? These designs appear to perform well enough and we are still at the stage where, with very few exceptions, locomotive owners see no reason to improve their charges. On preserved lines the pressure for improved performance does not exist. More traffic and either a larger engine is used or more trains are run, or maybe double heading is resorted to. How many preserved lines are concerned about the annual fuel bill? Concerned enough to do something about it?

How many are concerned about the cost of keeping on top of locomotive repairs but choose not to improve the design of valves and lubrication systems to name two.

Only the demands of access to the National Network might focus more minds and money on the creation of machines that will not be pushed to the fringes, the distant outposts because of their lack of performance. Those few that have a serious interest in continuing to develop the steam locomotive are sadly lacking in numbers at present.

 

It would have been pretty sad if that had not been the case. Not many excuses about at that date.