|Title of Invention||
"A METHOD FOR MANUFACTURE OF CASCADE BLADES FOR AERODYNAMIC RESEARCH"
|Abstract||The invention relates to a method of manufacture of cascade blades for aerodynamic research comprising the following process steps : steel block (1) cut to rough size, machining of the said steel block (1) for the threaded stub (2), rough machining of the profile (3) and the fixing pins (6) in a milling machine, rough profile shape (4) is an electro discharge machine using the rough profile shape (4A) of the copper electrode, finish profile shape (5) in an electro discharge machine using the finish profile shape (5A) of the copper electrode, fixing pins (6) are finished in electro discharge machine using the fixing pin profile (6A) of the copper electrode, and finally electroplated with Nickel and Chromium.|
|Full Text||"AN IMPROVED CASCADE BLADE FOR AERODYNAMIC RESEARCH AND A METHOD OF MANUFACTURE THEREOF"
The invention relates to an improved cascade blade for aerodynamic research and a method of manufacture thereof.
Cascade blades are used in the Aerodynamic investigations to determine profile losses, secondary losses etc. For this purpose a limited number (normally 7) of 2 dimensional straight and accurately made blades are required to be fitted between two cascade box windows. Blades for low pressure steam turbine tip sections, are thin and so when they are further scaled down to suit the cascade tunnel size they are very thin under this circumstances it would be very difficult to have separate fixing pins, though small in size.
There are various types of cascade blades and method of manufacture of cascade blades like as described below :
WOODEN BLADES :
The cascade blades out of wood are made by an experienced pattern maker who would make it as per templates. MILD STEEL BLADES:
Another practice was to machine the blades in a shaper or copy milling machine and finish it by a fitter to an accurately machined template.
FIBER REINFORCED PLASTIC (FRP) BLADES:
Some of the laboratories are making their blades of FRP. It needs to make a split mould for the blades. The FRP blade is built by a skilled worker by laying the glass fibres and the resin and then allowing to set after boxing up. After setting, the blades are taken out and inspected with templates. There were practices of making solid and hollow blades in FRP depending on the aspect ratio of the blades and thickness.
There are disadvantages with the above three type of cascade blades.
The disadvantages associated with the wooden blades are that these were not accurate and fixing tubes on the cascade blades for surface pressure distribution was cumbersome. Making thin blades and facilitating to fix them in the windows was also difficult. Accuracy of fixture was suffering. Also was time consuming.
The disadvantages associated with the mild steel blades are that the methodology suffered difficulties when handling thin blades. The process took lot of time & was expensive.
The disadvantages associated with the Fiber reinforced plastic (FRP) blades are that (FRP blades give highly glossy finish but accuracy is below average.
Another type of cascade blades presently being extensively used which are manufactured in a computer numerical control (CNC) machine.With the advent of CMC machines the cascade blades are being made by providing the co-ordinates fairly acurately.
There are disadvantages associated with the CNC machined cascade blades.
One of the main disadvantages is that machining of cascade blades in an expensive CNC machine is time consuming and thus it was very expensive.
Another disadvantages with the CNC machined cascade blade is that with thin section blades, machinering of the fixing pins is difficult.
Still another disadvantage of CNC machined cascade blade is that CNC machines are available with few agencies and is difficult to get their time. Quick or timely delivery is not possible.
Therefore the main object of the present invention is to provide a method of manufacture of cascade blades very accurately on its profile.
Another object of the present invention is to perpose a method of manufacture of cascade blade with integral fixing pins which is very accurate and provides a very accurate cascade box making. As the fixing pins are made integral they are very strong.
Vet another object of the present invention is to propose a method of manufacture of cascade blade which has very good finish.
A further object of the present invention is to propose a cascade blade and a process which is economical and can be made in commonly available inexpensive machines which is quick and simple compared to earlier process.
According to the present invention there is provided a method of manufacture of cascade blades for aerodynamic research comprising the following process steps:
a) Steel block cut to rough size,
b) machining of the said steel block for the threaded stub,
c) Rough machining of the profile and the fixing pins
in a milling machine,
d) Rough profile shape is an electro discharge machine
using the rough profile shape of the copper electrode,
e) Finish profile shape in an electro discharge
machine using the finished profile shape of the
f) Fixing pins are finished in electro discharge
machine using the fixing pin profile of the copper
g) and finally electro plated with Nickel or chromium.
The nature of the invention, its objectives and further advantages residing in the same will be apparaaent from the following description made with reference to non limiting exemplary embodiments of the invention represented in the accompanying drawings.
Fig. 1. Shows a cascade blade evolution from rough block-to finished shape.
Fig. 2. Copper electrode with profiles cut by wire cut EDM.
Figure 1. Clearly indicates the machining of cascade blade from rough steel block (1) to finshed blade.
The steel block cut to rough size (1) is shown by chain dotted line in fig.l machining of the threaded stub (2) end of steel block is then undertaken by conventional machining process. Rough machining in a milling machine for profile (3) and the integral fixing pins is then done. The cascade blade with the rough finished fixing pin and profile is now ready for rough (4) and finish profile and finish of fixing pin (6) by electro discharge copper electrode as in fig. 2. The electrode is provided with rough machining profile (4A) and finished profile and correspond to rough (4) and finish (5) profile of the blade. The electrode profile rough (4A> and finish (5A) is used
one after the other. The copper electrode is also provided with a pin of profile 6A corresponding to the fixing pin profile and is used as a last process step. In the copper electrode the rough (4A), finish and fixing pin profiles (6A) are at distance
of '>;' ? machine.
PROCESS INVOLVES THE FOLLOWING STEPS:
a) Making of rough machined cascade blade with a threaded end
(2) by conventional machines from steel block (1) cut to rough
b) Rough integral fixing pins are made in the blade stock (1)
along with profile (3) of the blade by conventional machines.
c) Making of electrode plate with requisite profiles using wire
cut machine for rough and smooth (5A) machining of the blade
profiles and machining of fixing pins (6A).
d) Sinking the rough (4) machined blades through the rough (4A)
and smooth (5A) machining profile cut—outs on the electrode
sequentially, with appropriate current discharge set, in a
relatively inexpensive Electro Discharge machine, which is
e) The rough machined pin part (3) is sunk through two holes
drilled in the electrode plate to form integral pins (6) for the
f) The blades are buffed to the requisite finish.
g) Electro plating with Ni or Chromium is made on blade to make
the cascade blades rustless.
The invention described hereinabove is in relation to a non-limiting embodiment and as defined by the accompanying
1. A method of manufacture of cascade blades for
aerodynamic research comprising the following steps :
a) Steel block (1) cut to rough size,
b) machining of the said steel block (1) for the threaded
c:) Rough machining of the profile (3) and the fixing pins (6) in a milling machine,
d) Rough profile shape (4) in an electro discharge machine
using the rough profile shape (4A) of the copper electrode,
e) Finish profile shape (5) is an electro discharge
machine using the finish profile shape (5A) of the copper
f) Fixing pins (6) are finished in electro discharge
machine using the fixing pin profile (6A) of the copper
g) and finally electroplated with Nickel or Chromium.
2. A copper electrode for electrode discharge machine for use with the method of manufacture of cascade blades as claimed in claim 1 comprising of rough machining profile shape (4A) and a finish machining profile shape (5A) and profile for obtaining finished fixing pins (6A).
3. A cascade blade with integral fixi rig pins manufactured by using the method of manufacture as claimed in claim 1 wherein the said cascade blade is manufactured from a steel block cut to rough size (1) to a finished profile shape with threaded stub (2), blade profile (5) and integral fixing pins (6) which is buffed and electroplated with Nickel or Chromium.
|Indian Patent Application Number||819/DEL/1998|
|PG Journal Number||10/2008|
|Date of Filing||30-Mar-1998|
|Name of Patentee||BHARAT HEAVY ELECTRICALS LTD.|
|Applicant Address||BHEL HOUSE, SIRI FORT, NEW DELHI-110049, INDIA.|
|PCT International Classification Number||F01D 5/34|
|PCT International Application Number||N/A|
|PCT International Filing date|