Improved Process of and Apparatus for Production of High Vacua
A Word From Charlie Solis: Owner of TesTur Energy
This is not a new revelation, but it should be pointed out that Tesla said in the high vacua patent:
“The modifications in details of construction, to which reference has been made, consist in the employment of smaller spaces between the discs than has hitherto been the case, and of close side-clearances. To give a practical example, I may state that spaces of 3/64 (.04687in) of an inch will be effective in the production of very high vacua with discs of, say, 24 inches in diameter.”
- Nikola Tesla
Now that being mentioned, in relation to the United States turbine patent, PN: 1,061,206, Tesla states that the larger the diameter, the larger the intervening spacing should be, but he also adds a lot more to that same statement. He said the following:
“The dimensions of the device as a whole, and the spacing of the disks in any given machine will be determined by the conditions and requirements of special cases. It may be stated that the intervening distance should be the greater, the larger the diameter of the disks, the longer the spiral path of the fluid and the greater its viscosity. In general, the spacing should be such that the entire mass of the fluid, before leaving the runner, is accelerated to a nearly uniform velocity, not much below that of the periphery of the disks under normal working conditions, and almost equal to it when the outlet is closed and the particles move in concentric circles.”
- Nikola Tesla
He specifically states that there’s a relation to this thickness - as the viscosity increases, so should the spacing. So I would like to link a steam viscosity chart for everyone to look at:
As both the temperature and the pressure of steam decreases so does the viscosity - in fact by a great deal. The numbers at the bottom of the chart are not a magical increase in steam viscosity. That’s when it changes to the state of being liquid water. What this means is that for a cold steam, low pressure, low temperature Tesla turbine, we need to further decrease the disc spacing because of the decrease in viscosity of steam at those lower temperatures and pressures. This is why having tight disc spacing is very important for cold steam turbines. Furthermore there needs to be A LOT of volumetric flow of the cold steam through the turbine at such low pressures because the drastically decreased pressures means the density is far lower.
Why this is important is because all heat engines/pumps (and all thermodynamic cycles) have their power outputs strictly defined by the mass flow rates of the motive fluid. Because the very low pressure steam has very low density to get the large mass flow rates the turbine has to have MANY disc spaces to be able to allow for the full volumetric flow rates to get the proper mass flow rates to achieve adequate power outputs. Thus, along with the increased surface area by having more discs, it also allows for having that many more spaces for the low pressure, low density, cold steam to flow through. This applies to both the drive turbine and the pump. Furthermore, if we look at these hyper physics charts for the viscosity of different gasses, we can actually see that steam has a lower viscosity than air:
This further signals that for low pressure, cold steam turbines, the discs spacing, even for larger turbines, need to be far smaller than heretofore used before. The 0.0092in spacing is almost exactly 1/5 the thickness for the 24in diameter suggested spacing of 3/64ths (0.04687in). From this information I assert that for low pressure cold steam turbines my usage of disc spacing of .0092in disc width and spacings (using 75 of them to get over 10,000in^2 of active plate surface area) is very adequate for the 10in turbine being built - this is not only more than half the diameter of the 24in diameter discs Tesla suggested, but the viscosity of cold steam is almost half that of air, even compressed air or low pressure air being evacuated. If 3/64ths spacing is proper for high vacua with 24in diameters discs, then the spacing for a high vacua pump half the diameter is far less than 1/2 as the spiraling path length decrease or increase is not linear. Tesla explicitly states that the length of the spiral pathway traveled plays a huge role in the spacing. So while yes, the larger diameter discs need wider spacing, Tesla is referring to turbines of diameter 24 inches and larger as a matter of fact. Something 100% planed to do in the near future as soon as the 1.5m x 1m CNC router is up and running.
There’s definitely a point of diminishing returns if not accounted for by adding more disc space to continue to allow for more mass flow rate. It’s a weird calculation to make too because you can’t compare the increased number of spaces to something smaller in any way. This is why my rule of thumb, is that the spacing should be no more than 2 times the laminar boundary layer thickness. If the flow rate becomes diminishing to efficiency because the area is being minimized, the number of disc spaces needs to be increased. So for example, when they (the authors of the article below on disc thickness and spacing) tested really tight disc spaces they didn’t actually test a total number of open space and a different number of discs. They tested the same number of discs with smaller spaces - so the tests with the smaller spaces overall actually have less open area to allow for mass flow rates. In my opinion, it’s incorrect to compare 25 discs with .5mm vs 25 discs with .25mm spacing. I also think it would be incorrect to compare 25 discs with .5mm spacing (with a total of 12.5mm of open spacing) to 50 discs with .25mm spacing (so it has the same 12.5mm total open spacing too) because the surface area is so different.
We want these to be as inexpensive and as durable as possible so we can get these out to the most people the fastest! There’s no need to charge an exorbitant amount. Tesla specifically designed these to be the least expensive engines or turbines out there to make. I hope this was helpful for everyone!
- Charlie Solis
Recommended reading
Disc Thickness and Spacing Distance Impacts on Flow Characteristics of Multichannel Tesla Turbines
by Wenjiao Qi, Qinghua Deng * , Yu Jiang, Qi Yuan and Zhenping Feng
“Abstract: Tesla turbines are a kind of unconventional bladeless turbines, which utilize the viscosity of working fluid to rotate the rotor and realize energy conversion. They offer an attractive substitution for small and micro conventional bladed turbines due to two major advantages. In this study, the effects of two influential geometrical parameters, disc thickness and disc spacing distance, on the aerodynamic performance and flow characteristics for two kinds of multichannel Tesla turbines (one-to-one turbine and one-to-many turbine) were investigated and analyzed numerically. The results show that, with increasing disc thickness, the isentropic efficiency of the one-to-one turbine decreases a little and that of the one-to-many turbine reduces significantly. For example, for turbine cases with 0.5 mm disc spacing distance, the former drops less than 7% and the latter decreases by about 45% of their original values as disc thickness increases from 1 mm to 2 mm. With increasing disc spacing distance, the isentropic efficiency of both kinds of turbines increases first and then decreases, and an optimal value and a high efficiency range exist to make the isentropic efficiency reach its maximum and maintain at a high level, respectively. The optimal disc spacing distance for the one-to-one turbine is less than that for the one-to-many turbine (0.5 mm and 1 mm, respectively, for turbine cases with disc thickness of 1 mm). To sum up, for designing a multichannel Tesla turbine, the disc spacing distance should be among its high efficiency range, and the determination of disc thickness should be balanced between its impacts on the aerodynamic performance and mechanical stress.”
A summary from the patent
“What I claim is:
1) The improved process of rarefaction which consists in rotating a disc system communicating with a receptacle and continuously ejecting fluid adhering to said system, until a high vacuum is attained in the receptacle, as described.
2) The improved method of exhausting a vessel which consists in rotating a system of discs and continuously applying the frictional force, arising from the viscosity of the fluid and its adhesion to said system, to exhaust the vessel until a high vacuum is attained, substantially as described.
3) The improved process of rarefaction which consists in sucking out of a vessel attenuated fluids by the frictional force of a system of rotating discs, compressing them in the passage through the same, and discharging them into the intake duct of a positively acting pump, as described.
4) As a means for obtaining high vacua, the combination of apparatus, as illustrated and described.” Dated the 23rd day of August, 1921.”
The full patent text
“I, Nikola Tesla, Electrical and Mechanical Engineer, citizen of United States of America, of No. 8, West 40th Street, New York, N.Y., U.S.A., do 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:-
In the development of power by thermo-dynamic primemovers, as steam engines and turbines, a low back pressure is essential to good economy, the performance of the machine being increased from fifty to one hundred per cent. by reducing the absolute pressure in the exhaust space from fifteen to about one pound per square inch. Turbines are particularly susceptible to such improvement and in their use for operation of power plants and manufacturing establishments the attainment and steady maintenance of high vacua has assumed great importance, every effort being made to better the conditions in this respect. The gain effected by this means is, in a large measure, dependent on the initial pressure, characteristics of the primemover, temperature of the cooling medium, cost of the condensing apparatus and many other things which are all well-known to experts. The theoretical saving of from five to six per cent. of fuel for each additional inch of vacuum is often closely approximated in modern installations, but the economic advantages are appreciably lessened when higher vacua are applied to existing machines purposely designed to operate with lower ones. More especially is this true of a turbine in which the reduction of back pressure merely increases the velocity of exit of the vapors without materially augmenting the speed of their impact against the vanes, buckets, or equivalent organs, when the loss of kinetic energy in the exhaust may offset a considerable portion of the useful work. In such cases some constructional changes in the turbine and auxiliaries may have to be made in order to secure the results here contemplated but the additional capital used for this purpose will be profitable invested. Summing up the situation it may be generally stated that a more or less substantial reduction of fuel cost can be made in most of the existing power plants by the adoption of proper pumping apparatus and establishment of working conditions nearly corresponding to those of an ideal condenser.
The chief difficulties which have thus far retarded advancement in this direction are encountered in the enormous volumes of the air and vapor at very low pressures as well as unavoidable leaks in the condenser, pipe joints, valves, glands and stuffing boxes. At present exhaustion is usually accomplished by reciprocating pumps and these, on account of the necessarily low speed of the pistons are large and, moreover, incapable of satisfactory performance in the presence of big leaks. As a direct result of this the condensing plant is both bulky and expensive and, worse still, its size and cost increase entirely in disproportion to the results attained. To illustrate - the outlay involved in the instalment of condensing apparatus for a twenty-eight inch vacuum is more than double that required for a vacuum of twenty-six inches and these draw-backs are still more emphasized with the further reduction of the back pressure. Rotary pumps and jets of water and steam are also used in the production of vacua, but without marked qualitative advantages.
I have achieved better success in departing from the customary method of removing the air and entrained steam from the condenser by bodily carriers as jets, reciprocating pistons or rotating vanes, and availing myself of the properties of adhesion and viscosity which, according to experimental evidence are retained by the gases and vapors even at very high degrees of attenuation. This new process is rendered practicable through a pump, the underlying principle of which is fully explained in my British Patent 24,001 of 1910, but which is modified as hereinafter described and when run at the very great peripheral speed of which an unloaded system is capable, exhibits two remarkable and valuable properties. One of these is to expel the rarefied fluids at such an immense rate that a hole of some size can be drilled in the condenser without much effect on the vacuum gauge. The other is to draw out the fluids until the exhaustion is almost complete. A machine of this kind, constructed in stages, is alone sufficient for the production of extremely high vacua and I believe this quality to be very valuable inasmuch as it is not possessed to such a degree by other types of commercial pumps which have come to my knowledge. I have also found that a very effective combination is produced by inserting my pump between the condenser and a “dry air” or other pump. This combination is especially advantageous from the practical point of view as good results can be secured with a single stage and the instalment of my device calls for but a slight change in the steam plant. The benefits derived are twofold; a higher vacuum is attained and, what is perhaps more important, the frequent and unavoidable impairments of the same, which seriously affect the economy, are virtually eliminated. My pump makes possible the maintenance of high vacua even when the percentage of air or other fluids carried with the steam is very great and on this account should prove particularly useful in the operation of mixed fluid turbines.
My invention will be more fully understood by reference to the accompanying drawings in which Fig. 1 shows a multistage pump of this kind in sectional views, and Fig. 2 illustrates its use in connection with a double-acting reciprocating pump.
In the first figure, 1,2,... are rotors each of which, as 1, comprises a number of relatively thin disks 3, 3... separated by star washers 4, 4... and held together by rigid end-plates 5 and 6 on a sleeve 7 which is fitted and keyed to a shaft 8, rotatably supported in bearings 9, 9. The rotors are contained in separate chambers of a common structure 10 which surrounds them and is made up of parts held together by flange connections. Beginning with the first stage at 1, the rotors diminish in width, each following being made narrower than the preceding, for obvious economic reasons. All the thin discs, as 3, 3... and left hand end-plates, as 5, are provided with the usual central openings, but the righthand end-plates, as 6, are blank. The individual chambers, containing the rotors, communicate with each other through channels, as 11, extending from the peripheral region of one to the central part of the next, so that the fluids aspired at the intakes 12, 12 are compelled to pass through the whole series of rotors and are finally ejected at the flanged opening 13 of the last chamber. In order to reduce leakage along the shaft, close-fitting joints or locks, as 14, are employed which may be of ordinary construction and need not be dwelled upon specifically. The number of stages will depend on the peripheral velocity and the degree of exhaustion which it is desired to secure, and in extreme cases a number of separate structures, with intermediate bearings for the shaft, may have to be provided. When found preferable the pump may be of the double-flow type, when there will be no appreciable side thrust, otherwise provision for taking it up should be made.
The modifications in details of construction, to which reference has been made, consist in the employment of smaller spaces between the discs than has hitherto been the case, and of close side-clearances. To give a practical example, I may state that spaces of 3/64 of an inch will be effective in the production of very high vacua with discs of, say, 24 inches in diameter. I also make all discs tapering, when necessary, in order to operate safely at an extremely high peripheral velocity which is very desirable since it reflects both on the size of the machine and its effectiveness.
The arrangement represented diagrammatically in Fig. 2 is especially suitable and advantageous in connection with existing steam plants operating with high vacuum and permits the carrying out of my improvements in a simple manner and at comparatively small cost. In this case my pump, which may have but one rotor of the above description, is connected with its intake 12, through a pipe 15, to the top of a condenser 16, and with its discharge opening 13, by pipe 17, to the suction duct, of a reciprocating dry air pump 18. It goes without saying that in actual practice connections 15 and 17 will be short mains of very large section as the volume of fluids to be pumped may be enormous.
The operation will be readily understood from the foregoing. The intakes 12 (Fig. 1) being joined by an air-tight connection to the vessel to be exhausted and the system of discs run at very high peripheral velocity the fluids, by reason of their properties of viscosity and adhesion, are drawn out of the vessel until the degree of rarefaction is attained for which the apparatus has been designed. In their passage through the series of rotors the fluids are compressed by stages and ejected through the opening 13 at a volume greatly reduced. The vacuum produced by this means may be extremely high because of the apparently unique properties of the device pointed out before, and as the fluids, irrespective of their density, are sucked out at an excessive speed, leaks through the glands, stuffing boxes and connections are of but slight effect.
In the arrangement shown in Fig. 2 my pump serves to evacuate the condenser much more effectively and by compressing the fluids at the intake of the reciprocating pump improves the performance of the same. The instalment of the device in existing plants does not call for extensive alterations in the same and will result in a notable saving of fuel. My pump may also be advantageously employed in place of a steam jet in conjunction with a small condenser in which case it will be of insignificant dimensions and economical in steam consumption.
Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:-
The improved process of rarefaction which consists in rotating a disc system communicating with a receptacle and continuously ejecting fluid adhering to said system, until a high vacuum is attained in the receptacle, as described.
The improved method of exhausting a vessel which consists in rotating a system of discs and continuously applying the frictional force, arising from the viscosity of the fluid and its adhesion to said system, to exhaust the vessel until a high vacuum is attained, substantially as described.
The improved process of rarefaction which consists in sucking out of a vessel attenuated fluids by the frictional force of a system of rotating discs, compressing them in the passage through the same, and discharging them into the intake duct of a positively acting pump, as described.
As a means for obtaining high vacua, the combination of apparatus, as illustrated and described.
Dated the 23rd day of August, 1921.
Nikola Tesla.”
