An Arrangement for Producing Vacuum around Steam Turbines.
Year: 1891

page_text: Date of Application, 26th Nov., 1891--Accepted, 26th Nov., 1892
COMPLETE SPECIFICATION.
An Arrangement for Producing Vacuum around Steam Turbines.
1, CARL GUSTAF PATRIK DE LAVAL, Dr. Phil. of Stockholm Sweden to
hereby declare the nature of this invention and in what manner the same is to
be performed to be particularly described and ascertained in and by the following
statement—
This invention aims at using the waste-steam escaping from the buckets of a
steam-turbine so that by means of it a powerful vacuum is maintained round the
turbine-wheel, for the purpose partly of diminishing the friction of the quickly
revolving wheel against the surrounding medium, and partly by means of an
extended expansion of steam in the steam nozzle, to augment the effective power
of the steam, so that the greatest possible effect may be obtained from the steam,
which passes through the turbine.
The accompanying drawings show in Figs. 1 and 2 a contrivance for carrying
the present invention into effect.
Fig. is an end view of the apparatus and Fig. 2 a plan section through the
steam inlet and steam exhaust pipes of same. Through the pipe A. the high-
pressure steam is conducted to the expansion nozzle B, intended for the isoentropic
expansion of the steam to that pressure, which prevails in the chamber D, Fig. 2
surrounding the turbine wheel C. After the steam in B has been expanded and
has attained a great velocity in the last section of B, it is impelled on the buckets E
of the turbine wheel C. Here the velocity of the steam is reduced, partly by the
friction of the buckets, partly by being turned into work, whereby the direction of
the steam is considerably changed. The centre line of the exhaust-pipe F has the
same direction as the steam escaping from the buckets and that part of it,
section G H G H₁, which is nearest to the turbine wheel, is so large that it with
perfect certainty allows escape for the exhaust-steam, which has been somewhat
spread during its passage through the wheel.
The sides G and HK, Fig. 2 of the exhaust-pipe are made slightly convergent
from the section at GH to the section at IK, the sides G H and G H being
formed to correspond with two concentric circular segments, whose distance from
each other is somewhat greater than the height of the buckets. The section at 1 K
is not made larger than is necessary for the steam to escape without being
straitened, so that the steam is touching closely against the sides of the pipe. As
in this way the exhaust-steam is collected and made to pass out through the
exhaust-pipe with decreasing speed and a pressure, gradually approaching and at
length slightly exceeding the pressure of the outer atmosphere, it produces a
vacuum in the casing of the turbine, the amount of which depends upon the rate at
which the steam escapes from the turbine, and the steam is exhausted by itself at
the same time. Thus the arrangement is similar to that of a common ejector.
The inner space of the turbine casing D, or what I may call the vacuum
chamber, is of course well shut off from the outer atmosphere, partly through
packing between the flanges L and M, partly by means of a suitable packing
around the turbine-shaft at N and O.
Experiments, which have been made, have proved that this way of producing a
vacuum round the steam-turbines is as effective as it is economically advantageous,
compared with a vacuum obtained in the usual manner by means of condensation.
It has also been proved that it is not necessary to give the exhaust-pipe the
ejector-form shown in the drawing, although this must be considered as the most
effective.
In case it be desired and possible to do with a smaller degree of efficiency, the
collecting part of the exhaust-pipe as well as the funnel-shaped part of it on the

page_text: other side of section IK can be done away with. The remaining part will then
consist of a plate with a hole, like section IK, which is adjusted to suit the escaping
steam-jet.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what 1
claim iş.
An arrangement for producing a more or less powerful vacuum around steam
turbines, thus increasing their efficiency, consisting of an ejector-shaped exhaust-
pipe through which the exhaust-steam from the turbine is allowed to pass for
the purpose of producing a vacuum in the turbine-casing, while the steam at the
same time is exhausted by itself.
Dated this 26th day of November 1891.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.