A cross-flow water turbine has a casing, a runner, a horizontal inlet and a vertical outlet. The inlet is divided by a pivoted guide vane to form a pair of inlet passages. A horizontally extending admission passage is connected to the casing at the inlet side thereof, and a vertically extending discharge passage is formed as a draft tube and connected to the casing at the outlet thereof. The inlet and the guide vane are arranged such that the inlet flow to the runner is directed downward at an angle of about 40.degree. with respect to the horizontal, and the outlet flow from the runner is directed substantially vertically. At the outlet there are a pair of side spaces on either side of the runner resulting in an increased cross section conforming to the cross section of the draft tube. Both of these side spaces are vented to the atmosphere by a single venting valve so that the suction pressure in the draft tube does not exceed a predetermined value.

The present invention relates to a cross-flow turbine comprising a casing, 
a runner rotatably mounted in the casing and having a flow pattern such 
that the water flows substantially radially from the outside to the inside 
of the runner, past the center of the runner in spaced relationship 
thereto and then substantially radially from the inside to the outside of 
the runner, the flow entering the runner in an impact-free manner, a flow 
passage in the casing comprising an inlet area and an outlet area, with 
the runner being disposed in the casing flow passage, a guide vane 
pivotally mounted in the inlet area to close the inlet area by engaging 
opposite casing walls when in a closing position and dividing the inlet 
area in a pair of inlet passages when in its other positions, an admission 
tube connected to said inlet area, and a discharge tube connected to said 
outlet area, which discharge tube extends vertically and is formed to be a 
draft tube. 
Cross-flow turbines of this type are known, e.g. from applicants' German 
Pat. Nos. 707.839, 815.780, and 895.279. With these cross-flow turbines 
the admission tube extends substantially vertically. In order to obtain an 
impact-free flow entrance to the runner, the guide vane and the inlet area 
of the casing flow passage direct the flow such that the resultant of the 
flow entering the runner has a substantially vertical component. This 
results in the flow leaving the runner having a substantial horizontal 
velocity component resulting in flow turbulence and corresponding flow 
losses. 
Also with horizontal flow admission (see e.g. German Pat. No. 178.228) it 
has not been possible to avoid a flow pattern with the flow leaving the 
runner having a substantial horizontal velocity component. 
From German Pat. Nos. 347.271, 383.134, and 388.530, there have become 
known cross-flow turbines wherein the flow leaving the runner at least 
theoretically extends in a vertical direction. Since, however, these 
cross-flow turbines do not have a guide vane, it is believed that in 
practice it is not possible to have the flow leave the runner in a 
substantially vertical direction. 
Accordingly, it is an object of the present invention to provide a 
cross-flow turbine having reduced flow losses in the outlet area of the 
casing flow passage. 
According to the present invention, a cross-flow turbine of the type as 
identified above is characterized in that, with said admission tube 
extending horizontally, the casing flow passage and the guide vane 
arranged such that the resultant of the flow entering the runner is 
inclined downwardly under an angle a of substantially 30.degree. to 
50.degree., preferably 40.degree. with respect to the horizontal and the 
resultant of the flow leaving the runner is directed substantially 
vertically. 
With such a cross-flow turbine the flow leaves the runner in a 
substantially vertical direction even though a horizontally extending 
admission tube is used. The invention provides for a reduction of flow 
turbulence in the outlet area of the casing flow passage and accordingly 
results in an increase of flow efficiency. 
With cross-flow turbines of the above type the draft tube should be of a 
relatively large cross-section. In order to increase the cross-section of 
the casing flow passage to that of the draft tube, it has become known 
(e.g. from German Pat. No. 815.780) to provide the outlet area of the 
casing flow passage with an arcuate side space at the side of the runner 
remote from the admission tube. Such side space is vented from atmosphere 
via a resiliently biased venting valve such that suction pressure within 
the draft tube may not exceed a predetermined value so that the water 
level within the draft tube will not rise above the lowest point of the 
runner. 
Since with the cross-flow turbine of the present invention the flow leaves 
the runner in a substantially vertical direction, the outlet area of the 
casing flow passage may have a cross-section increase on both sides of the 
runner. In a preferred embodiment of the present invention, there is 
provided a second side space increasing the cross-section of the casing 
flow passage on the side of the runner opposite said first side space. 
Preferably, such second side space is also vented from atmosphere in order 
to avoid flow turbulences in this area.

The cross-flow turbine shown in the drawing includes a runner 2 having a 
plurality of circumferentially spaced blades 4 of circular arc profile. 
The runner 2 mounted on a horizontal shaft 6 rotates in a casing flow 
passage 10 confined by a casing 8. 
The casing flow passage 10 comprises an inlet area 12 and an outlet area 
14. Connected to the inlet area 12 is a horizontally extending admission 
tube 16 of rectangular cross-section, while the outlet area 14 merges into 
a vertically extending discharge tube 18 being also of rectangular 
cross-section and serving as a draft tube. 
In the inlet area 12 there is disposed a guide vane 20 adapted to be 
pivoted about a horizontal axis by means of a shaft 22. The guide vane 20 
comprises a nose portion 24 and a trailing tail 26 inclined thereto at 
about 45.degree.. 
Guide vane 20 when in its fully open position (as shown in the drawing) 
divides inlet area 12 into a pair of inlet passages 12a and 12b. Inlet 
passage 12a is confined by the straight upper side 28 of the trailing edge 
26 and a straight casing wall 30 associated therewith. Upper side 28 of 
trailing edge 26 and housing wall 30 each include with the horizontal an 
angle b of about 12.degree. to 20.degree., preferably 16.degree.. However, 
it is to be noted that upper side 28 of trailing edge 26 and housing wall 
30 slightly converge with respect to each other so that inlet passage 12a 
is of slightly decreasing cross-section as seen in flow direction when 
guide vane 20 is in its fully open position. 
Inlet passage 12b is confined by the straight lower side 32 of nose portion 
24 and the opposed upper side 36 of a casing wall 34. The lower side 32 of 
nose portion 24 and the upper side 36 of casing wall 34 each include with 
the horizontal an angle c of about 40.degree. to 50.degree., preferably 
45.degree. when guide vane 20 is in its fully open position. However, it 
is to be noted also in this case that inlet passage 12b slightly 
converges as seen in flow direction to achieve a corresponding velocity 
increase of the flow. 
Guide vane 20 is adapted to be adjusted from its fully open position (as 
shown in the drawing) through intermediate positions to a closing position 
at which trailing edge 26 engages casing wall 30 and nose portion 24 
engages casing wall 34 to thereby close the inlet area 12. 
Outlet area 14 comprises at the right side (as seen in the drawing) a side 
space 40 increasing the cross-section of the casing flow passage and 
confined by an arcuate casing wall. On the left side (as seen in the 
drawing) there is a somewhat smaller side space 42 confined by the lower 
side 44 of casing wall 34 and a vertical wall of casing 8. The side spaces 
40, 42 increase the cross-section of casing flow passage 10 to the 
cross-section of discharge tube 18 which theoretically should be endless 
and in practice is twice the size of the entrance cross-section of inlet 
area 12. 
To prevent the water level within discharge tube 18 from rising above the 
lowest point of runner 2, side space 40 is vented from atmosphere by a 
resiliently biassed venting valve 46 so that suction pressure inside space 
40 may not exceed a predetermined value. 
While theoretically venting of side space 40 to maintain a predetermined 
water level in discharge tube 18 should be sufficient, practice has shown 
that turbulence losses in side space 42 caused by rotation of the runner 
may be reduced by also venting side space 42 from atmosphere. To this end 
side space 42 is connected to a conduit 48 which preferably is vented from 
atmosphere also via venting valve 46. 
In operation water flows from admission tube 16 in horizontal direction 
into inlet area 12 where the water flow is divided by guide vane 20 
extending across the whole width of the inlet area 12 into a pair of 
partial streams flowing through inlet passages 12a and 12b and being 
united downstream of trailing edge 26. The united stream enters the runner 
2 in the area between trailing edge 26 and the lower end of casing wall 
30. As shown by an arrow 50, the flow direction is such that the flow 
resultant includes with the horizontal an angle a of approximately 
30.degree. to 50.degree., preferably 40.degree.. The geometry of the flow 
passage and the vanes 4 of runner 2 and the speed of runner 2 are chosen 
such that the flow enters runner 2 in a substantially impact free manner. 
As indicated by a dotted line, the water stream flows through the interior 
of runner 2 in an off-center area and thereafter leaves the runner in the 
area of the lowest point of runner 2. At this point, the flow resultant is 
directed substantially downwards as indicated by an arrow 52. 
In the inlet passage 12a the flow resultant is downwardly inclined under an 
angle b of about 12.degree. to 20.degree., preferably 16.degree. with 
respect to the horizontal, while the flow resultant in inlet passage 12b 
is upwardly inclined under an angle c of about 40.degree. to 50.degree., 
preferably 45.degree. with respect to the horizontal. This geometry 
results in the desired flow pattern of the flow entering and leaving 
runner 2. 
When guide vane 20 is in its intermediate positions under partial load 
conditions, the flow pattern at least theoretically is the same. 
Due to this flow pattern, in particular due to the vertical outlet flow, 
and due to the double venting of the outlet area there is a reduction of 
turbulence losses in the outlet area 14 resulting in an increased flow 
efficiency.