A method for driving a two phase turbine characterized by an output shaft having at least one stage including a bladed rotor connected in driving relation with the shaft is described. A two phase fluid is introduced into one stage at a known flow velocity and caused to pass through the rotor for imparing angular velocity thereto. The angular velocity of the rotor is maintained at a value such that the angular velocity of the tips of the blades of the rotor is a velocity equal to at least 50% of the velocity of the flow of the two phase fluid

Elliott, D. G.

English

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United States Patent [I91 [ I  I J Patent Number: 4,514,137 
Elliott [45] Date of Patent: Apr. 30, 1985 
[54] METHOD FOR DRIVING TWO-PHASE 
TURBINES WITH ENHANCED EFFICIENCY 
[75] Inventor: David G. Elliott, La Canada, Calif. 
[73] Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 431,420 
[22] Filed: Sep. 30, 1982 
Related US.  Application Data 
[63] Continuation of Ser. No. 161,257, Jun. 20, 1980, aban- 
doned. 
[51] Int. C1.3 ................................................ FOlD 1/04 
[52] U.S. C1. ........................................... 415/1; 415/68 
[58] Field of Search ................... 415/1, 30, 60, 66, 67, 
. 415/68, 50 
[561 References Cited 
U.S. PATENT DOCUMENTS 
2,438,357 3/1948 Bloomberg ........................... 415/68 
3,305,214 2/1967 Kennedy ........................... 415/68 X 
3,635,576 1/1972 Wieckmann ...................... 415/68 X 
FOREIGN PATENT DOCUMENTS 
560584 10/1932 Fed. Rep. of Germany ........ 415/68 
Primary Examiner-Everette A. Powell, Jr. 
Attorney, Agent, or Firm-Paul F. McCaul; John R. 
Manning; Thomas H. Jones 
t571 ABSTRACT 
A method for driving a two-phase turbine 10 character- 
ized by an output shaft 20 having at least one stage 
including a bladed rotor connected in driving relation 
with the shaft, and wherein a two-phase fluid is intro- 
duced into said one stage at a known flow velocity and 
caused to pass through the rotor for imparting angular 
velocity thereto, the speed of the rotor being controlled 
so that the angular velocity of the tips of the blades 
thereof is a velocity equal to at least 50% of the velocity 
of the flow of the two-phase fluid. 
3 Claims, 4 Drawing Figures 
28 
RE L 
OUT 
25 
OUT 
51 
RELATIVE 
STAGE 1 
STAGE 2 
https://ntrs.nasa.gov/search.jsp?R=19850020970 2020-03-22T19:42:40+00:00Z
U.S. Patent Apr. 30,1985 Sheet 1 of2 4,514,137 
2a 
RE L 
OUT 
25 
OUT 
FIG. 3 
R EL AT IVE 
28 
OUT 
4 4  
150 
JET 

4,5 14,137 
1 2 
ciency thereof being enhanced through a 
friction drag. METHOD FOR DRIVING TWO-PHASE TURBINES 
WITH ENHANCED EFFICIENCY 
OBJECTS AND SUMMARY 0 
ORIGIN OF THE INVENTION 5 INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA Contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics & Space Act of 1958. Public Law 85-568 
(72 STAT 435; 42 U.S.C. 2457). 
This is a continuation of application Ser. No. 161,257, 
filed June 20, 1980, now abandoned. 
It is an object of the instant inventi 
method through which the efficiency of two-phase 
turbines is enhanced. 
Another object is to provide in a method for driving 
10 a two-phase turbine the step of maintaining the angular 
velocity of the rotor thereof in a value such that the 
angular velocity of the tips of the rotor blades is a veloc- 
ity equal to at least 50% of the velocity of a flow of 
two-phase fluid as the fluid is introduced into the tur- 
These and other objects and advantages are achieved 
through a method wherein the angular velocity of the 
rotor is maintained at a value such that the angular 
velocity of the tips of the blades of the rotor is a veloc- 
2o ity equal to at least 50% of the velocity of the flow of a 
two-phase fluid as the flow is introduced into the tur- 
bine, the velocity of the rotor being controlled through 
the output shaft of the turbine. 
DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a schematic view of a two-stage, two-phase 
turbine adapted to be driven employing the method 
embodying the principles of the instant invention. 
BACKGROUND OF THE INVENTION 
ing two-phase turbines and more particularly to a 
method for reducing friction loss and low efficiency for 
multi-stage turbines adapted to be driven by a flow of a 
liquid-gas mixture, herein referred to as a two-phase 
fluid. 
DESCRIPTION OF THE PRIOR ART 
Heretofore, it has been common practice to drive 
turbines employing a liquid, such as water, or a gas, 
such as steam, herein simply referred to as a single- 2s 
phase fluid. In systems designed to utilize steam and the 
like, multi-staging of turbines is relied upon to permit 
the angular velocity or tip speed of the turbine blades to 
The invention generally relates to a method for driv- l 5  bine. 
be low, when ‘Ompared to the incoming flow ’peed Or FIGS. 2a and 2b comprise diagrammatic views de- 
fluid‘ Such staging fie- 30 picting computation of efficiency for two-phase tur- Of the quently is referred to as “Curtis” staging. In these sys- bines where the relative velocity of the fluid and the tems, increased fluid friction acting on the blades is blades of the turbine is zero. considered to be an acceptable price to pay, particularly FIG. 3 is a diagrammatic view depicting computation since fluid friction generally is not considered to consti- tute a serious impairment to efficiency. Furthermore, 3s of efficiency for a two-stage, two-phase turbine wherein 
the velocity ofthe tips ofthe turbine blades, when corn- the Of the exiting fluid flow to the 
pared to the linear velocity of the flow of the fluid, must 
be low in order to maintain the mechanical integrity of DESCRIPTION OF THE PREFERRED 
EMBODIMENT the turbine. 
fluid friction generally is not considered to constitute a Referring now to the drawings, with more particular- 
serious impairment to efficiency because of the laminar ity, there is shown in FIG. 1 a two-stage, two-phase 
flow characteristics of the boundary layer established turbine system generally designated 10. Since the Strut- 
by the liquid as it is caused to flow over the surfaces of turd details of the turbine system 10 forms no part of 
the blades of the turbines. 45 the claimed invention, a detailed description thereof is 
AS is well known by those familiar with two-phase On-~itted in the interest of brevity. 
fluids, however, where the quantity of the liquid in a The system 10, as illustrated, however, includes a 
flow of two-phase fluids is relatively low, when com- two-stage, two-phase turbine generally designated 12 
pared to the total for the two-phase flow, the liquid connected with a suitable source of two-phase fluid, not 
tends to attach itself to the surfaces of the blades so that so shown, via a two-phase nozzle 14. A typical two-phase 
the relative velocity thus established between the two- fluid comprises a waterlair mixture ratio of 10:1 by 
phase liquid and the turbine blades is reduced due to the mass. 
dissipating effects of the friction. Of course, as the quan- The turbine 12 includes a first stage, not designated, 
tity of the flow of liquid is increased, the relative veloci- having a turbine rotor 16, as well as a second stage 
ties of the flow increases, relative to the velocity of the 55 having a turbine rotor 18. The rotors 16 and 18 are of a 
turbine blades, due to the laminar flow established as the bladed design and are connected with a turbine output 
liquid passes over the surfaces of the blades. shaft 20, via a suitable gear box 22. In practice, the gear 
Heretofore, even though the angular velocity of the box 22 serves to connect the rotors 16 and 18 to the 
tips of the turbine blade in a two-phase system has been output shaft 20 in a manner such that the ratio of the 
deemed to be acceptably low, due to the effect of fric- 60 angular velocities of the rotors 16 and 18 is maintained 
tion of the liquid passing over the blades, widespread at a constant ratio of 2:l. As is also illustrated in FIG. 1, 
use of such systems has not been experienced because, the turbine system 10 includes a suitable gas-liquid dis- 
at least in part, it commonly has been accepted that charge manifold, the function of which should be appar- 
suitably high efficiency for turbines designed to be ent. It is believed sufficient to note that the rotors 16 and 
driven by two-phase fluids simply was not obtainable. 65 18 comprise bladed rotors through which is caused to 
It is therefore the general purpose of the instant in- flow a two-phase fluid, injected into the nozzle 14, and 
vention to provide a method through which a turbine that this fluid eventually exits the system via the mani- 
may be driven using a two-phase fluid with the effi- fold 24. 
velocity of the turbine blades is greater than zero. 
In systems designed to utilize a liquid, such as water, 40 
4,5 14,137 
3 4 
It is important to note, however, that the load applied CE= 150--88=62; POWER=(62)(112)=6944. The 
to the shaft 20 is calculated and applied in a manner output power for the second stage is computed as fol- 
such that the angular velocity or speed of the rotor 16 is lows: FORCE=88-25=63; POWER=63 x45=2835. 
such that the tips of the blades achieve a tangential Hence, TOTAL POWER=6944+2835=9779. 
velocity of at least 50% of the linear velocity of the 5 By dividing the total power, or 9779 by the kinetic 
flow of the two-phase fluid as it exits the nozzle 14. It is energy, or jet power 11250, an efficiency of 87% is 
known in the prior art to control the velocity of rotor computed. 
blades through the application of a load applied to an In view of the foregoing, it is believed to be readily 
output shaft. A common example is a turbine connected apparent that the present invention provides a solution 
to an electric generator wherein the generator must be 10 to the problem of large friction loss and low efficiency, 
synchronized with the electrical power grid to which previously encountered, utilizing two-phase flow in 
its power lines are connected. Thus, the actual speed of turbines. 
the turbine blades will be dictated by the synchroniza- 
tion of the electric generator. Since the ratio of the 
What is claimed is: 
1. improved method of driving a two-phase fluid 
l6 and l8 is 2:1, it 15 turbine having at least a first and second stage of bladed 
extract kinetic energy for driving an output shaft 
the output shaft, comprising the steps of: 
for the 
should be apparent to those familiar with tip speeds of 
that the tip speed or for the tips Of the 
rotors sequentially receiving the two-phase fluid to 
through a gear box connecting the respective rotors and 
rotors of turbines designed for two-phase fluid systems 
rotors 16 and 18 is “high” relative to the linear velocity 
(a) introducing into the first stage bladed rotor, at a of the incoming flow of two-phase fluid. 
predetermined linear flow velocity, a flow of the Referring for a moment to FIG. 2 4  therein is illus- 
two-phase fluid; trated computation for a “worst-case” condition for the 
(b) causing the two-phase fluid to pass through the system shown in FIG. 1. In this condition, it is assumed 
first and second stages so that the stages rotate in that the relative velocity of the two-phase fluid as it passes over the turbine blades is zero. In other words, as 
illustrated, the two-phase fluid enters the first stage of (c) maintaining the tangential velocity of the first the system 10 at a velocity of three, any unit, designated stage bladed rotor tips at a velocity greater than 3 JET, while the velocity of the tips of the blades of the fifty percent of the predetermined linear flow ve- rotor 16 is 1.5, designated 1.5 BLADE. Thus the fluid locity entering the first stage; enters the turbine at a speed of 1.5, relative to the blade, 
designated (d) maintaining the tangential velocity of the second 
stage rotor blade tips at a fixed ratio of about fifty induced velocity losses, the fluid exits the rotor at an 
absolute exit velocity of 1.5, 1.5 OUT, so that the rela- percent of the tangential velocity of the first stage 
tive velocity of the fluid flow and the tips of the turbine bladed rotor; and 
blades is equal to zero, 0 REL. (d) exhausting the two-phase fluid from the second 
stage whereby a Power efficiency of at least two- 
the jet velocity squared, JET POWER=32/2=4.5. The thirds is extracted from the kinetic energy of the 
force of the flow exerted on the blade is equal to mo- two-phase fluid introduced into the first stage. 
mentum change, FORCE=3- I S =  1.5; the power out- 2. A method as defined in claim l wherein the tangen- 
put is equal to the force of the flow multiplied by the tial velocity of the first stage rotor is about two-thirds of 
velocity of the blade, POWER=(1.5)(1.5)=2.25; and 40 the predetermined linear flow velocity entering the first 
the efficiency of the turbine is equal to the output power stage. 
divided by the kinetic energy of the jet, EFFICIEN- 3. An improved method of driving a two-phase fluid 
CY=2.25/4.5=&, or 50%. turbine having at least a first and second stage, said 
Using known computational methods, it can be calcu- bladed rotors being generally parallel to each other, of 
lated that the efficiency of the system 10 is equal to the 45 bladed rotors sequentially receiving the two-phase fluid 
ratio of N/N+ 1, where N equals the number of stages to extract kinetic energy for driving an output shaft 
in the turbine. through a gear box connecting the respective rotors and 
In order to calculate the efficiency for the two-stage, the output shaft, the load applicable to the output shaft 
two-phase turbine, depicted in FIG. 1, it is noted that c o n t r o h g  the rotor velocity comprising the steps of: 
the power out for each stage, FIG. 26, is determined 50 (a) introducing into the first stage bhded rotor, at a 
with the output power for both stages being computed predetermined linear flow velocity, a flow of the 
and then totaled and divided by the kinetic energy of two-phase fluid; 
the velocity as it is introduced to the question. For (b) causing the two-phase fluid to pass through the 
example, note that for the first stage, FOR- first and second stages so that the stages rotate in 
CE=3-2= I ,  and POWER=(l)x(2)=2, while the 55 the same direction; 
FORCE (of the second stage)=2- 1 = 1 and PO- (c) maintaining the tangential velocity of the first 
WER=(I)X(I)=I. The TOTAL POWER (for the stage bladed rotor tips at a velocity greater than 
two-stage system)=2+ l =3, and EFFICIEN- fifty percent of the predetermined linear flow ve- 
CY=3/4.5=$ or 66.6%. locity entering the first stage; 
(d) maintaining the tangential velocity of the second 
loss is not as great as depicted in FIGS. 2a and 26, and stage rotor blade tips at a fixed ratio of about fifty 
higher efficiencies are in fact realized. As indicated in percent of the tangential velocity of the first stage 
FIG. 3, where the angles of the flow of two-phase fluids bladed rotor tips; and 
are ignored and it is assumed that the two-phase fluid (e) exhausting the two-phase fluid from the second 
possesses a velocity relative to the velocity of the tips of 65 stage whereby a power efficiency of greater than 
the blades of each stage, a higher efficiency can be two-thirds is extracted from the kinetic energy of 
expected. For example, for the first stage, as depicted in the two-phase fluid introduced into the first stage. 
20 
25 the same direction; 
REL. However, because of frictionally 30 
The kinetic energy of the jet, or jet power, is one-half 35 
At most practical flow conditions, the liquid velocity 60 
FIG. 3, JET POWER=(0.5)(1502)= 11,250; FOR- * * * * *  


Method for driving two-phase turbines with enhanced efficiency

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