XXIst
Century Steam
The Day of Modern Steam Traction
Ing. Livio D. Porta, Consulting Engineer
Note: This paper contains matter subject to intellectual property and patent rights. All rights reserved.
Buenos Aires, Dec. 15 1997.
Contents:
Abstract
1 Introduction
2 The background
3 General considerations
4 Thermodynamics
5 The GPCS (Gas Producer Combustion System)
6 Biomass as a railway fuel
7 Mechanical and operational aspects
8 Third Generation Steam
9 Examples
10 Additional considerations and recommendations
11 Main conclusions on steam locomotives as railway motive power
References
The proposed technology will be the most recent to be developed in the First World. Yet it must fit Third World requirements because diminishing natural resources (esp. oil) and pollution will be global problems in the XXIst century1.
1 Introduction
All over the world there is a steam renaissance. Whilst this is at present limited to tourist trains, new generations are beginning to realise that steam can be used to run trains in a manner far different from the one often portrayed by the media. There are a number of reasons for this new attitude, as will be discussed in this paper. The present is an era of admirable "super-technologies" (which also include "super-expectancies"). There are however problems which these super-technologies cannot meet, and these may be decisive. Steam enthusiasts will be delighted to hear what follows in this paper. However, they must realize from the very beginning that the advent of XXIst Century Steam is not a comeback of the steam locomotives which they once loved. Instead it incorporates the most advanced level of modern engineering, even if the wheels are still round, the boiler is still used to evaporate water and a bunker is still used to carry the fuel.
The title of this paper could be misleading: it should have read "the author's steam". It is not the intention here to discuss future steam traction in general, with all its possible variants, but simply to present his approach to the problem. This may be a pedantic attitude but, so far, he believes that there is merit in doing so. One day, if what follows in this paper is converted into a sound business, that attitude will be considered irrelevant: what will count is the essence of the proposal. The steam locomotive proposals presented here do not refer to "super" transportation duties, super speeds, super tonnages, super traffic intensities etc but rather to the more humble duties which make up everyday life for the majority of people. This does not mean that high speeds or heavy tonnages lie beyond the range of services: remember that 5000 t coal trains were at one time considered for the Rio Turbio Railway, Argentina, 750 mm gauge, 30 kg/m rail. Millions of passengers will be happy if they can travel in a decent manner rather than on the roofs of the coaches!
2 The Background
The First World is saturated: everybody has a house, medicine, transport, motor cars, education, theatres, holidays, spare time etc. Production costs are constantly decreasing. Money (i.e. effort) which was at one time allocated to the arms race is now available for any use, but this use is no longer to be found in the First World. Therefore, if the process is to continue at the same momentum, a new market (in the broadest sense) is to be found: this is the Third World. An immense market! That World wants to become a consumer society, yet it must be taught how to consume, and its immense richness needs to be developed for useful purposes. Thus, the First World will take its tremendous potential of know-how and capital to the Third World, as is already happening. This will in turn lead to a huge industrial and trade explosion, in turn necessitating a transport explosion. This explosion cannot, by force, be a road transport explosion. A railway one is what is required. The question does however remain: which form of motive power is to be used?
Parallel to the above, pollution will develop exponentially. Whilst noxious gases resulting from the imperfect combustion of hydrocarbons are already creating a great deal of anxiety, the greenhouse effect, caused by CO2 emissions, is perhaps overwhelming. What can be done to prevent this problem?
Advanced, XXIst Century Steam can, as will be demonstrated, provide the answer by running trains on biomass fuels, i.e. on solar energy. This answer must however be developed by the First World, as the Third World will not use locomotives if they are not considered to be of the latest technology. The engines proposed in this paper will certainly reflect the latest technology, as they do not harm the environment, do not use oil and are cheap to build and maintain. Furthermore, the First World should also start to use them, otherwise it will be suffocated by contaminants produced by road traffic and the other forms of motive power.
3 General Considerations
The development of steam traction may be divided into four generations of locomotives:
What follows in this paper refers to the Second Generation locomotives as an immediate answer to the challenges faced today. The author adheres to the classical, STEPHENSONIAN scheme. It does not hold true that, as many people (including steam engineers) believed, it reached the pinnacle of its potential development. This is a point first put forward by CHAPELON in 1926. CHAPELON had discovered that the way to progress was not through the fancy schemes then being proposed as a means of facing the challenge of electrification, but rather through the correction of a number of engineering imperfections which were accepted as natural at the time. Of these imperfections, the lack of sufficient internal streamlining was perhaps the most important. This of course was not (and is not) the sole step to improvement; the author has advanced along the same line of thought according to the following incomplete summary:
The above list should be completed by a myriad of details which together enable the harmonious operation of the various thermodynamic and mechanical components, each of which is integrated into that admirable conception which is the STEPHENSONIAN locomotive. One should at this point remember its fundamental characteristics as currently understood:
XXIst Century Steam continues to keep to these fundamentals, albeit altered and improved. So, what makes the difference? The answer: thermodynamics. In reference to which BULLEID, the last of the English giants, said2: "Thermodynamics never sold a single locomotive."
Most importantly of all, it requires an investment per hp which is about a third of that necessary for an equivalent diesel fleet, not to mention its ability to work on a wide range of fuels.
4 Thermodynamics
A locomotive operates on the basis of extremely complex thermodynamic phenomena. This is true of most machines: an aeroplane also uses extremely complex aerodynamic phenomena. The point remains however that the following principle applies:
Nobody knows what he does not know until he knows it.
The English-speaking world behaved as if thermodynamics did not exist: this explains why BULLEID made the remark quoted above. Yet his post-WWII Pacifics ran daily at 130 km/h (80 mph), and a maximum of 200 km/h (124 mph) was reached by DRG's 05 and 202 km/h (126 mph) by GRESLEY's A4. The steam locomotive was already an admirable machine before scientific thermodynamics reached the engineering community. Its development progressed mainly by trial and error on an empirical basis. Long before any quantitative analysis was possible, the British were, as early as 1895, able to run the 869 km between London and Aberdeen in 8 h 29 min with three stops made during the night. The empirical genius of those engineers was however insufficient to produce, after WWII, engines which performed significantly better than the pre-war KINGS for example, whilst at the same time their fellow engineers working on aeroplanes had invented the jet. Mention should be made of the unhappy efforts of GOSS and YOUNG in America: the former took the "loss of tractive effort at speed" as inherent to the very nature of the steam locomotive, whilst the latter, after considerable theoretical and experimental work, achieved those worst ever ejectors characteristic of most American locomotives: a thundering exhaust and a 3m column of solid black smoke were far from correlating with power and efficiency!
Although the names of GARBE and STRAHL must be cited for the Continent, it was not until the work of CHAPELON appeared in 19383 that a clear understanding of what a steam locomotive is became reality. Unfortunately, he wrote in French, not in English. His tremendous step forward was therefore a cry in the dark. It was not until after WWII that the British showed a blast of genius in understanding what a steam locomotive is, namely a machine to convert chemical energy into mechanical work: ELL was the new hero4.
Thermodynamics does not however simply mean the description of the locomotive in terms of the theoretical heat engine affected by suitable coefficients as required to adjust it to practical experience. It is much more: it is to describe each of the particular phenomena as related to engineering fundamentals. This should make it possible to predict the work of each one of the parts.
Prediction based on such fundamentals is the key to progress because the designer can manipulate all the involved factors so as to achieve the most convenient result.
An example of such a prediction of performance is the formula for the pressure drop between the steam chest and the cylinder in piston valves at a given cut-off:
where:
[bar] pressure drop at cut-off 
;
[bar] steamchest pressure;
[-] cut off; 
[m3/kg] steam specific volume; 
[-] coefficient to account for steamchest pressure oscillations; 
[-] clearance volume/cylinder volume; 
[cm] lead; 
[cm] lap; 
[cm] port length (circumferential); 
[-] contraction coefficient of the stream at port opening; 
[dm3]
cylinder volume;
[1/s] revolutions per second; 
[-] coefficient to account for wall effects.A
design aim should be to have
as small as possible. The above formula was developed by STRAHL in 19245,
later modified by the author. The influence of the various parameters is quite
apparent so that the designer can play with them to the best advantage. Thus
a large lead ,
a large valve diameter (i.e. a large ),
a large contraction coefficient ,
a low (condensations!),
small oscillations ()
etc. can be quantitatively treated. How far is all this from the vagaries of
the "long valve travel" of the GRESLEY era! All this was not even
suspected in the English-speaking world. SCHÜLE treated these phenomena
as early as 19066.
In addition, the engineer must combine all relevant factors so as to produce
a "commercially successful" machine – and nothing less! For
certain, this is not textbook thermodynamics. The above formula is an example.
What it represents should be extended to the myriad of phenomena occurring in
a locomotive. This is not that machine of such a dazzling simplicity that most
people (including most engineers) believe it to be. Fortunately for XXIst Century
Steam, the computer makes a manageable matter out of it.
5 The GPCS (Gas Producer Combustion System)
The GPCS is described in my paper: "Exemple d'une technique de progrès: la combustion gazogène", Conference de l'ICOHTEC, Paris, 1992. It essentially consists in transforming the firebed into a gas producer by making it very thick. Only 30% (20% in the case of biomass) of the combustion air passes as primary air through the grate, thus leading to an almost negligible particle entrainment. The secondary air makes up the lion's share of the air needed for combustion and creates an intense turbulence in the flame space so that the gas phase combustion can proceed to the degree of completeness required to meet pollution laws. While it appears to have that extreme simplicity characterizing great inventions, its thermodynamics are extremely complicated – after all just an intellectual problem!
The GPCS started to be developed in 1958 by the author in connection with the use of coal as fuel. But concerning XXIst Century Steam, its great merit is that it leads to a simple, most efficient use of biomass as locomotive and industrial fuel. Any kind of biomass may be used, as proven by tests in 19637. So far, the following fuels have been successfully fired: firewood in logs, sawmill rejects, bagasse (in stationary boilers), a wide variety of coals, bagasse-oil briquettes, charcoal fines mixed with oil etc. In the near future, rice husks, orange peels, bark, and dry peat will be tested. One of the blessings of the system is that smoke disappears. In 1963, tests were successfully carried out with charcoal fines (0-6 mm) under fluidized bed conditions. CO and HC emissions virtually disappear, and NOX emissions are very close to their theoretical minimum. The expectancy is that, by simply blending the fuel with a calcite-dolomite mixture, sulphur can also be controlled to a large extent.
6 Biomass as a railway fuel
During WWII, the author worked as a fireman on locomotives originally designed for coal, later converted to burn wood in log form. The sole modification was the suppression of the brick arch. No change in the performance was detectable provided that the firewood was seasoned so as to reduce the high initial moisture content, while for heavy services certain species were preferable because of the need to limit the physical effort of the fireman. As proven by the 1963 experiments, and later in Paraguay (in 1988), the GPCS gave complete satisfaction as a first class locomotive firing system. Developments in hand consist in mechanizing the feed by hogging the fuel, thus enabling it to be handled in bulk: any level of power can be developed.
Energetic plantations are not a novelty. The driving force behind them is that the CO2 produced by the combustion of firewood comes from the fixing of the atmospheric CO2. Thus no additional CO2 is liberated to increase the greenhouse effect, a matter of major concern. Transportation is one major offender, and the possibility of reducing CO2 emissions to a great extent thanks to the use of biomass must be considered as a great contribution to environmental protection. By no means is this limited to railways.
7 Mechanical and Operational Aspects
While advanced thermodynamics is a key element of XXIst Century Steam, other aspects of locomotive engineering are by no means less significant because they encompass all that must be done in order to convert theory into the actual economical pulling of trains. Perhaps the most important one is feedwater treatment. Since 1944, the French TIA system guarantees an indefinite life for the boiler to the point that it can be welded on to the frame. Pure steam (contamination < 1 ppm) also guarantees an indefinitely long life of the superheater and reduces the abrasive wear in the cylinders. The advances made by the author since 1970 are reflected in the fact that the treatment is cheap and heavy duty, a most important characteristic for the Third World8.
The following mechanical improvements are considered:
The fuel and water consumption is expected to be reduced to one fourth of what old steam locomotives (generation zero) show. This results in much longer runs between stops to take water and fuel. In shunting duties, the fuel consumption should equal the diesel one. Last but not least, a most elaborated ergonomy should be achieved for all concerned.
8 Third Generation Steam
The possibilities of XXIst Century Steam are not exhausted with the previously described listing. Should the thermal efficiency issue become even more pressing, Third Generation steam locomotives could reach 21% under test conditions, of course using biomass as fuel. The improvement is on the thermodynamic cycle:
All still keeping to the STEPHENSONIAN scheme.
Should it prove to be interesting, a further advance in thermal efficiency, a condensing scheme, could be envisaged. This condensation should occur in a "cooling-tower" tender like the SLM-ESCHER WISS machine (ca. 1926). The water treatment can be modified to accept raw water as boiler feed because the condenser is of the evaporative type. Optimistically, the overall thermal efficiency could reach 27% at the drawbar.
9 Examples
To avoid speaking about entelechies, Figs. 1a/b and 2 are two examples of XXIst Century Steam. Fig. 1a/b is a small 1000 hp engine for shunting and branch line services, whereas Fig. 2 is a 8000 hp fast freight engine for American or Russian conditions. The hp figures are to be interpreted in terms of equivalent-to diesel power. An infinite variety of designs could be imagined, although a spectrum of limited alternatives could probably cover 90% of the actual requirements. All of them are to be fired with biomass, hence environmentally clean.
Fig. 1a: Shunting
and branch line 3-cylinder compound locomotive.
|
1.
Fuel space (6m3); 2. Fuel space (6m3); 3. Feed water heater (6m2); 4. LEMPOR ejector; 5. Air pump; 6. LP cylinder (512mm x 550mm); 7. HP cylinder (440mm x 550mm); 8. LP cylinder (512mm x 550mm); 9. Cyclonic Gas Producer firebox; 10. Water tank (12m3); 11. Water tank (6m3); 12. Economizer; 13. Air pre-heater; 14. Sand box; 15. Sand box; 16. Sand box; 17. Ash box; 18. Fuel inlet. |
Fig 2: Third
Generation fast freight 8000hp locomotive. Click
for an enlargement.
The STEPHENSONIAN configuration is adhered to. The high thermal efficiency leads to a very small boiler for the high power output and a reasonably sized tender for 500 km non-stop runs. The locomotive shown in Fig. 2 is ballasted because of the very high power-to weight ratio.
Although the 8000 hp locomotive incorporates a special form of booster giving a very high tractive effort at low speeds, one should note that the generalization of roller bearings for the cars reduces the need for a high starting tractive effort. As seen, the familiar appearance of the STEPHENSONIAN locomotive continues to be the choice. Many people will be disappointed because they cannot perceive anything but bogies, individual axle drives, water tube boilers, electric drives etc. But the question is first one of thermodynamics, thereafter how this thermodynamics is transformed into a successful machine. They should point out what cannot be done within the proposed scheme as compared to the presumable advantages of the non-STEPHENSONIAN solutions. But, in the meantime, they should not forget the unconvincing or poor performance (in some cases to the point of utter failures) of the following engines:
A number of turbine locomotives are to be added to this list of failures, which should be studied to avoid the repetition of mistakes. Why, in spite of a predictable failure, were some engines built?
10 Additional considerations and recommendations
It is impossible to summarize, for the uninformed reader, what XXIst Century Steam is. When one considers that for most people even CHAPELON's work is unknown, never mind understood, the gap to be bridged is enormous: lack of information has been a plague in the past. This is certainly not the case for the automotive industry where everybody knows what everybody else is doing as a must for successful competition. Furthermore, such information is essential in order to make investment decisions; for nobody will invest in what they do not understand. Nobody likes the unknown!
A second difficulty is that no masterpiece can be produced according to a recipe, as is the case for a cookery course: talent is essential, and the lack of it may explain some of the listed failings.
A third difficulty is the lack of a driving force: who will convert the above technicalities into a large-scale business?
11 Main conclusions on steam locomotives as Railway Motive Power
References
