I guess the whole emphasis of Champelon and later Porta and others mentioned is the desireability to make a series of incremental improvements to the basic Stephenson steam locomotive rather than to go with something radical -- high pressure water tube boiler, turbines, condensor, electric drive.
The impetus for keeping steam or perhaps for bringing back steam is to burn solid fuel -- coal -- rather than liquid or gaseous fuels -- oil or natural gas. In the case of SLM, however, the impetus is to simply have a "steam locomotive" as a kind of historical recreation for recreational passenger travel, so I imagine that they are oil burning for simplicity of the supporting infrastructure (not requiring coaling towers, dealing with ash, etc).
I believe the basic Champelon and Porta thinking is that a 200 PSI with superheat firetube boiler already gets you 20 percent theoretical efficiency, so between the 5 percent of common steam locomotives and the 20 percent theoretical limit, there is a lot to be gained through the incremental improvements -- compound expansion or higher-expansion valve gear with simple expansion, streamlined steam passages, more efficient steam ejector draft systems -- that is before you start going crazy with high boiler pressure, water tube boiler, and so on. In terms of the historical what-if's, whay if the Champelon improvements could have replaced the 5 percent efficient locomotives with 10 percent efficient locomotives, effectively cutting the coal and water consumption in half. Would that have made enough difference to hold off Dieselization?
One of the features of the Stephenson steam locomotive that has resisted replacement is the fire tube boiler -- railroad applications of water tube and high pressure water tube boilers have been few and far between. I had once heard that water tube boilers "were not rugged enough to take the shocks of the railroad environment", but I suspect that other factors may be more significant.
The idea there is that condensers on a steam locomotive have to be huge on account of the general low efficiency of the cycle used and on account of a lack of access to water cooling, as used in a power plant next to a lake or river or on a ship, so condensers are a non-starter. Once you are committed to a "once-through" cycle of sending the spent steam up the stack, you need to supply large amounts of water, and you are stuck with the mineral content of whatever water you put in the tender.
The problem with water tube boilers along with the use of higher pressures is one of scale formation in the boiler. The once-through steam cycle dictates the use of the local water, which in turn dicates the use of fire tube boilers at lower pressures on account of the maintenance and safety concerns from scale formation. There is also the "foaming" problem where you get bubbles of scale-scum that can get carried into the steam circuit with bad consequences.
The French had this TIA process for putting additives in the feed water, and Porta had his version of it. Porta thought that with the right additives, you could tolerate water with mineral content, go to higher boiler pressures, and do away with much of the boiler maintenance, even talking about "30-year boilers" welded to the frame.
An idea I have had for use in such "excursion service" steam is to fill the tender with distilled water. Yes, that is costly, but what if that could be even more effective than TIA in reducing maintenance? Don't we have less costly ways of making distilled water using reverse osmosis? Could an excursion steam fill a "canteen tender" with city water and then have its own reverse osmosis (RO) unit to supply the main tender with mineral-free water?
Also on the subject of fire-tube vs water tube boilers, the Jawn Henry was a "box of tricks" as the English might say, but of its many unorthodox features was a 600 PSI water tube Babcock and Wilcox boiler. My understanding is that Jawn Henry was not condensing -- the pictures show a water tender with a brakeman's doghouse on the back (coal was carried in a bunker in the front of the locomotive proper). Jawn Henry was said to have problems with the electric gear in the water and coal-dust environment, they damaged a turbine in a hard coupling incident, but I never heard about problems with the water tube boiler.
If Jawn Henry was just about the water tube boiler and conventional everything else (pistons, siderods, no electric drive), would that experiment of changing just that one variable (increasing the boiler pressure) been successful in a way the D&H water tube experimentals were not?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
Some background for the uninitiated on these rare videos.The contract for a fully modernized reciprocating steam locomotive that became an example of modern steam technology went to the Swiss Locomotive and Machine Works (SLM) in Winterthur, a factory which in over 125 years had built some of the world's finest and best engineered steam locomotives, In 1996/7 SLM won a contract to rebuild 52 8055 by applying the modern steam technologies that they had developed . Roger Waller, then chief steam engineer at SLM, worked with the assistance of Livio Dante Porta by combining their knowledge and experience into the upgrading of the locomotive with the goal of making it as efficient and powerful as possible. LD Porta is posed below next to engine. A very under reported continuation of the trial experiments of new steam technology applied on the SAR Red Devil.. I particularly enjoyed the clear view tender which allows reverse operation at speed. .
http://www.youtube.com/watch?v=gIyiMIxtLNM&feature=related
Nothing is more fairly distributed than common sense: no one thinks he needs more of it than he already has.
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