Re: Steam Locomotives
brett.fitzpatrick@employment.gov.au
Thu, 23 Apr 1998 22:06:47 -0600
In article <6hmh0e$ckl$1@mirv.unsw.edu.au>,
G.Lambert@unsw.edu.au (Geoff Lambert) wrote:
>
> dbromage@metz.une.edu.au (David Bromage) wrote:
>
> >Wendy Diver (diver.wendy.wd@bhp.com.au) wrote:
> >>I am interested in the performance characterictics of steam locomotives,
> >>particularly in relation to diesel electrics both DC and AC traction. I
> >>would appreciate any information about generic speed/TE curves for steam
> >>locomotives and how these are affected by the number of driving wheels.
>
> >As speed increases for diesel and electroc locos, the tractive effort
> >decreases. For steam, it increases with speed.
>
> Such a thing bids fair to lead to perpetual motion, a wonderful
> concept, but one which does not hold. See my previous answer.
>
> >The class 26 in South Africa is vastly more efficient than conventional
> >steam locos, but lack of government enthusiasm prevented further work.
> >The Alfred Country Railway has done similar things to its NGG16 locos.
>
> Well people, like Dusty Durrant, reckon it was "vastly" more
> efficient. The major modifications were to the fire-bed, to increase
> combustion efficiency. But, there really was not much scope for
> increased combustion efficiency under good conditions: 84% fuel ----->
> boiler water was pretty easily achievable in any loco.. The 26-class
> also adopted the Chapelon principles as far as steam passages and
> valve events goes. This does tend to increase efficiency a little,
> but essentially it increases utilization (i.e. power, not necessary
> efficiency.... there was less restriction on the development of power
> at speed)
>
> >There are some highly efficient steam generation plants (e.g. power
> >stations), but these use water tube boilers which are unsuitable for
> >locomotive use.
>
> The principal reason for increased efficiency (which can be over 40%,
> compared with an average steam loco of 8%) is the increase in pressure
> (and hence boiling temperature), plus a high degree of superheat.
> Maximum possible efficiency is given by the famous Carnot equation
> (T2-T1)/T2. The higher T2 and the lower T1, the higher the
> efficiency. Steam temperatures can be over 1000 Centigrade and
> pressures above 200 atmospheres in a modern thermal power plant. A
> water-tube boiler is necessary to sustain these pressures, of course,
> but they can be less combustion efficient than a fire-tube boiler
> with a radiative-absorptive firebox. Another, and dominating, reason
> for a power plant's high efficiency is low exhaust pressure- less than
> 0.01 psi (practically a vacuum) can be acheived with turbines, but
> never with a reciprocating steam engine (about 20 psi). Low exhaust
> pressure means low T1.
>
> Geoff Lambert
>
>
I was under the impression that a Steam Locomotive's T.E. dropped and its
H.P. increased as speed increased until a maximum was reached (in modern
designs) at approx 40 - 50 m.p.h.
POTS (Power Other Than Steam) Units suffered a decease in H.P. as speed
increased, with their peak being available at approx 10-15 m.p.h.
Wndy, for some interesting information, try e-mailing Daniel an
dsdawdy@mcs.com and ask for his information on Baldwin #60000. It contains
test information etc that is probobly just what you want.
Brett
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