Adjusting means of rotary regenerative sector plate heat exchangers

Adjusting means for the sector plate sealing members of rotary regenerative heat exchangers, wherein at least one sensing means is attached to each sealing member, adjacent a circumferential metal flange supported by the regenerator body. The sensing means is connected to a control circuit for actuating a servo device for controlling the position of the sealing member in response to the capacity fluctuations in an electrical circuit comprising the space between the sensing means and the metal flange.

BACKGROUND OF THE INVENTION 
This invention relates to an adjusting means for the sector plate sealing 
members of rotary regenerative heat exchangers, and more particularly to 
an adjusting means which, in response to a thermal deformation of the 
regenerator body to a dish-like shape of the end surfaces of the 
regenerator body and the corresponding variation of the sealing spaces, 
actuates adjusting linkages of the sealing members by means of a servo 
device so as to maintain a predetermined sealing space, wherein at least 
one sensing means is attached to each sealing member adjacent a 
circumferential or annular metal flange or disc supported by the 
regenerator body. 
Adjusting means of this type are known for instance from U.S. Pat. No. 
3,232,335 (Canadian Pat. No. 704,958, GB Pat. No. 1,002,235) in which the 
sensing means are pneumatic, mechanical or magnetic. 
One known pneumatic sensing means comprises a nozzle carried by the sealing 
member, an impingement plate (a circumferential flange) carried by the 
regenerator body and means for supplying pressure air to the nozzle, the 
pressure of the air being dependent on the position of said nozzle 
relative to said impingement plate and the servo device being operable to 
adjust the position of the sealing member according to that pressure. 
Another known mechanical sensing means comprises a sensing lever carried by 
the sealing member, and a link connecting the lever to a control means for 
the servo device which is operable to adjust the position of the sealing 
member in response to displacement of the lever which is adapted to slide 
on a circumferential flange carried by the regenerator body. 
Still another known magnetic sensing means comprises an electro-magnet 
located to produce a magnetic field between the circumferential flange and 
a sealing member, the servo device being operable to adjust the position 
of the sealing member according to current variations due to changes in 
the strength of the magnetic field, which is dependent on the position of 
the sealing member relative to the flange. 
In all these known arrangements, the inclusion of a servo device brings 
about the advantage that very large adjustment forces can be produced so 
that even in very large size heat exchangers readjustment of the sealing 
members may be effected without difficulties. The smaller forces of the 
mechanical sensing lever are accompanied only by light wear and for that 
reason sensing levers of this type have a long working life. 
These known arrangements have the disadvantages, however, of being 
subjected to physical and chemical attacks by the impurities contained in 
the waste flue gases and to the high temperatures of the gases resulting 
in a considerable reduction in the life of especially the magnetic sensing 
means in which the electrical windings or coils and their insulating 
materials are non-resistant to heat. 
The object of this invention is to eliminate or at least reduce the 
above-mentioned disadvantages. 
SUMMARY OF THE INVENTION 
The above object has been achieved, according to the invention, in that the 
adjusting means of the kind defined hereinabove is characterized in that 
the sensing means is provided with an electrically conducting sensing 
element which is insulated from the sealing member and which is positioned 
close to the metal flange. The sensing element and the metal flange are 
electrically connected to a control circuit which is arranged to generate 
control signals indicating variations of capacity appearing in response to 
variations of the distance between the metal flange and said sensing 
element, which control signals are supplied to a servo device for 
adjusting the position of the sealing members. 
In this manner there is provided an adjusting means comprising a sensing 
means that is subject to no wear. Since the sensing means is subjected to 
only light corrosion and erosion, its life can be considerably prolonged 
by the selection of appropriate heat resistant material. 
The sensing means preferably comprises a cylindrical housing having two 
ends closed by insulating discs. One of the insulating discs, viz. the one 
facing the regenerator body, supports an electrically conducting sensing 
disc to which an electric conductor is connected extending through the two 
insulating discs to a pin plug device at the end of the sensing means 
facing away from the regenerator body. 
A further pin plug device may be located adjacent the first mentioned pin 
plug device, said further pin plug device being connected to an electrical 
temperature sensing device attached to the cylindrical housing of the 
sensing means. 
The conductor connected to the sensing disc preferably extends with a 
clearance through the insulating disc closing the end of the cylindrical 
housing facing away from the regenerator body, said conductor being 
longitudinally stretched by means of a compression spring and connected to 
its pin plug device via a further conductor forming an expansion curve. 
Moreover, according to a preferred embodiment of the invention time delay 
means are interconnected in the electrical connection between the high 
frequency amplifier and the servo device controlling the adjusting of the 
sealing members, which suppress the influences of short-lived fluctuations 
of capacity, and, hence, prevent the sealing means from being subjected to 
oscillatory motion.

DETAILED DESCRIPTION 
FIG. 1 is a partial sectional view of the right hand part of a rotating 
regenerative heat exchanger mounted for rotation about a vertical axis. 
A rotating regenerative body 1 is journalled in an upper bearing 3 and in a 
lower bearing 5 and is enclosed by a housing 7. 
The rotatable body 1 is in known manner subdivided into a plurality of 
sectorial comparatments and in order to prevent mingling of the two fluid 
flows there are provided an upper sector plate 9 and a lower sector plate 
11 as well as vertical sealing plates 13. The upper and lower sector 
plates are subdivided into a central section 9a, 11a and outer sections 
9b, 11b, the sections being pivotally connected to each other. The link 
between the central section 9a and the adjacent outer section 9b of the 
upper sector plate is adjustable by means of an adjusting rod 15 against 
the action of a spring member on the upper end wall of the housing. A 
central portion of the outer section 9b is according to the invention 
provided with a sensing means 17 just above a circumferential metal flange 
or disc 17' supported by said regenerator body 1, and a control circuit 19 
which includes a high frequency amplifier. The signals generated by the 
control circuit 19 control a solenoid valve 30 connected in a pressure 
fluid supply conduit 21 of a control cylinder 23. Control cylinder 23 
controls a control rod 23c via piston rod 23a and a knee lever 23b under 
the action of a counterweight, the control rod 23c being connected to the 
outer end portion of the outer section 9b of the upper sector plate 
sealing means. 
Similar control rod arrangements 25a to 25c with spring means are provided 
for supporting and adjusting the vertical sealing plate 13. 
The adjusting means of the upper sector plate sealing means, in this case 
positioned in the hot end of the heat exchanger, differs from the 
adjusting means of the lower sector plate sealing means in the cold end of 
the heat exchanger. Due to the fact that the rotor containing the 
regenerative mass when operated undergoes a thermal deformation and adopts 
a dish-like form, the end surfaces of the rotor will become convex and 
concave, respectively. Thus, close to the control rod supporting the link 
between sections 11a and 11b, there is provided, just underneath a 
circumferential metal flange or disc 31' attached to the regenerator body 
1, a first sensing means 31 connected to a control circuit 33 which 
includes a high frequency amplifier. The signal generated by the control 
circuit 33 controls a solenoid valve 40 in a pressure fluid supply conduit 
35 feeding a control cylinder 29 which in this case actuates the link 
between lower sector plate section 11a and the adjacent section 11b in 
response to the signals generated by the sensing means 31, 31', which link 
is moved by cylinder 29 over a linkage 27 perpendicular to the lower end 
surface of the regenerator body. The outer end of the lower sector plate 
section 11b, just underneath a circumferential flange or disc 37' attached 
to the regenerator body 1, is also provided with a sensing means 37, 
connected to a control circuit 39 which includes a high frequency 
amplified. The output signals of control circuit 39 actuate a solenoid 
valve 49 in a supply conduit 41 of a control cylinder 43 controlling via a 
linkage 45 the position of the outer end of section 11b. Thus, the 
position of the outer sections 9b of the upper section plate sealing means 
of the hot end of the heat exchanger, which end surface becomes convex, is 
each controlled by a sensing means only; but at the lower sector plates 
the links between control sections 11a and the adjacent outer sections 11b 
as well as the outer ends of the outer sections 11b are each adjusted by a 
sensing means 31, 31'; 37, 37' in response to concave deformation of the 
lower end surface of the regenerator body, i.e. the cold end of the 
regenerator body. 
FIG. 2 is a sectional view on a larger scale of a sensing means 17, 17' 
according to the invention. Sensing means 31, 31' and 37, 37' are 
substantially identical. The sensing means 17, 17' comprises a cylindrical 
housing 50 positioned in a suitable opening of the sector plate and 
fixedly attached to said sector plate. Both ends of the housing 50 are 
closed by respective insulating discs 52, 54. Disc 52 supports an 
electrically conducting sensing disc 56, suitably made of metal, to which 
an electric conductor 58 is attached, conductor 58 extending through 
control aperturesof the insulating discs 52 and 54. The outer end of 
conductor 58 (with respect ot the heat exchanger housing) is provided with 
a thrust washer 60 which together with a compression spring 64 and a 
washer 62 applies tension to conductor 58 under all thermal conditions. A 
further conductor section 66 having an expansion blow connects the outer 
end of conductor 58 to a pin plug device 68 attached to a base plate 70. 
Base plate 70 is attached to housing 50 by three supporting arms 72. A 
temperature sensing device 73 is connected via a conductor 74 to a further 
pin plug device 76 attached to the base plate 70. The temperature sensing 
device 73 is designed to compensate for changes of the dielectric value of 
the gases in dependence of the temperature. Sensing disc 17' is coupled to 
the corresponding control circuit 19 via a common ground connection. The 
pin plug device 68, 76 are connected via a cable to the input of a 
corresponding control circuit which develops control signals which are a 
function of the capacitance between sensing discs 56 and 17'. The control 
circuit generates amplified control signals which are selectively supplied 
via conductors to the associated solenoid valves (30, 40, 49) positioned 
in the pressure fluid supply conduits of the corresponding control or 
power cylinders. The valves are actuated and controlled by the 
corresponding control circuit for adjusting the position of the sealing 
members during thermal distortion of the regenerator body so as to 
maintain the sealing members in a predetermined position relative to said 
regenerator body. 
The operating mode of the ajusting device according to the invention is 
explained in more detail below. 
Each sensing means is coupled to a respective control circuit for 
generating an output control voltage responsive mainly to the capacitance 
between two parallel discs (the sensing disc 56 and the circumferential 
disc such as 17', 31', 37' attached to the regenerator body), and the 
temperature of the gas present between said two discs which acts as a 
dielectric medium. 
FIG. 3 illustrates a basic diagram of a control circuit according to the 
present invention. Only control circuit 19 is illustrated, the control 
circuits 33 and 39 being identical thereto. As shown in FIG. 3, the 
sensing discs 56, 17' are connected to a control circuit 19 which 
generates a control voltage, such as a stepwise varying DC control 
voltage, as illustrated. The sensing disc 56 is adapted to have its 
position varied in the direction of the arrow A shown in FIG. 3 relative 
to the annular disc 17'. Due to the variations in position of disc 56 
relative to disc 17'. Due to the variations in position of disc 56 
relative to disc 17', the electrical capacitance therebetween varies and 
these variations in electrical capacitance are sensed by the control 
circuit which generates a corresponding control output voltage. In other 
words, the control output voltage of control circuit 19 is dependent upon 
the distance or spacing between the sensing metallic discs 17' and 56 of 
the sensing means. The annular sensing discs or electrodes 17', 31' and 
37' are supported by the various portions of the regenerator body as shown 
in FIG. 1. The control circuit can also be thought of as 
electro-mechanical converters which generate an electrical control signal 
responsive to a sensed mechanical relative movement. 
Referring to FIG. 4, the control circuit comprises a crystal controlled 
oscillator 80 which generates an A.C. voltage having a constant frequency. 
The output of the oscillator 80 is coupled to an amplifier 81 which also 
receives modulation inputs from a resonance circuit 82, the resonance 
circuit being controlled by the capacitance between sensing discs or 
electrodes 56, 17'. The capacitance between sensing discs 56, 17', which 
is result of the relative displacement therebetween, changes the resonance 
frequency of the resonance circuit 82 as a function of said displacement 
or variation of capacitance. The capacitance is also dependent on the 
temperature of the gas between the sensing discs 56, 17', and in order to 
compensate for variations of said temperature the temperature sensing 
device 73 is connected via conductor 74 and pin plug device 76 to a 
further input terminal of said resonance circuit 82. The amplifier 81 
generates a modulated A.C. voltage having a constant frequency and an 
amplitude which is modulated as a function of the varying resonance 
frequency of the resonance circuit 82. The modulated A.C. voltage is 
rectified in a rectifier circuit 83 and the rectified voltage is coupled 
to a low pass filter 84 and then to a discriminator 85. The output of the 
discriminator 85 is the control voltage for controlling the associated 
control cylinder 23, 29, 43 via the respective valves 30, 40 and 49. 
The control signals actuate the solenoid-type valves such that the 
corresponding control or power cylinders are connected to the pressure 
fluid supply or to the pressure fluid outlet (not pressurized) in order to 
maintain said predetermined clearance between the sealing means 9, 13 and 
regenerator body during all types of thermal deformation of the 
regenerator body (called rotor "turn-down"). 
The solenoid-type valves may be termed generally as "servo-operated" 
valves. They may be replaced by motor operated valves which are generally 
known as servo-type valves. 
The cylindrical housing 50 preferably is made of metal and the insulating 
discs 52, 54 of alumina (alumina oxide). In order to minimize the 
self-capacity of the sensing means the inner diameter of the housing 50 
preferably is 80 to 120 mm and the diameter of the conductor 58 is 
preferably 3 to 5 mm. 
Although the invention has been described with reference to heat exchangers 
having a rotatable regenerator body 1 and stationary ducts, it is evident 
that it is applicable also to such regenerative heat exchangers having a 
stationary regenerator body and rotatable ducts.