inclined disc spherical case: butterfly valve · fig. 5: section generated for flow area...

Inclined Disc Spherical Case: Butterfly Valve

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Inclined Disc Spherical Case: Butterfly Valve | Mar 2013

© 2013, HCL Technologies, Ltd. Reproduction prohibited. This document is protected under copyright by the author. All rights reserved.

TABLE OF CONTENTS

Abstract ............................................................................................. 3

Abbreviations .................................................................................... 4

Market Trends/Challenges ................................................................ 6

Solution ............................................................................................. 7

Best Practices ................................................................................... 7

Common Issues .............................................................................. 12

Conclusion....................................................................................... 14

References ...................................................................................... 14

Author Info ....................................................................................... 14



3

Abstract

The environment for aircraft passengers has to be controlled

precisely at the required temperature by cooling or heating the air by

mixing air streams of different temperatures. While mixing the air

streams, the mass flow of air has to be very precisely controlled.

This flow control is achieved by valves of specialized flow

characteristics to ensure that with a wider movement of the valve

disc, a small and precise increase in flow is achieved. Also, the

valve has to operate for both directions of flow and sustain extreme

low to high temperatures. The valve should also be leak tight when

closed. It should not get stuck while closing or opening. The

mechanical design should be robust and the disc should not come

out into the flow stream.



4

Abbreviations

Sl. No. Acronyms Full Form

1 Amps Ampere, a unit for current

2 bar Unit of pressure

3 CAD Computer Aided Design

4 CV Flow coefficient of valve, i.e. flow delivered per unit

PSI pressure drop

5 °C Temperature in degrees centigrade scale

6 dP Pressure drop

7 DU Delivery unit

8 gram Unit of measuring weight

9 HVAC Heating ventilation and air conditioning

10 I Symbol for for electrical current

11 IIT Indian Institute of Technology

12 Kg Kilograms

13 Kg.M or Kg.m Unit for torque

14 min Minute, a unit of time

15 Max Maximum

16 N Rotational speed in revolutions per minute

17 N-m Newton meter, a unit to measure torque

18 OEM Original Equipment Manufacturer

19 P Power

20 Pd Pipe diameter

21 Pi A constant with value 22/7

22 PSI Pressure measured in pounds per square inch

23 Q Discharge

24 Rev Revolution

25 RPM Revolutions per minute

26 RPS Revolutions per second

27 Sd Diameter of the spherical surface of the valve

28 Sec Second, a unit of time



5

29 Spec Specification

30 V An electrical unit for Voltage

31 VDC Voltage in Direct Current

32 W Watt, a unit of Power

33 w.r.t. With respect to

34 * Sign for multiplication

35 Ф Angle of inclination of the valve stem



6

Market Trends/Challenges

The valve in this HCL internal project was conceptualised for cabin shut-off applications for the aerospace industry. This can also be used for other air handling applications such as HVAC. This concept was further checked for the variation of area of opening of the valve with its angle of opening. The gradual variation of flow area is required to achieve good flow control. It was also necessary to ensure that the disc/gate could be inserted from one end and should not come out from other end in case of shaft breakage so as to ensure safety concerns. The valve has to work for an air temperature range from -50° up to 180° C. and a pressure range up to 11.5 bar. It should withstand acceleration of up to 10 times gravity. It should deliver mass flow of 9.0 kg/min. Its weight should be less than 1.2 kg (max.) The allowable internal leakage should be less than 25 g/min at 6.0 bar and 180° C., and the external leakage should be less than 5 g/min at 6.0 bar and 180° C.

This valve was developed as

an internal project by HCL

Technologies.

This valve can be used in

Aerospace applications,

HVAC, and other applications

as well.



7

Solution

The solution is provided by the design of the valve as shown in the solid models developed at HCL.

Fig. 1: Section of the model of the valve with its parts concept model by HCL As seen in the Fig.1 above, the valve modelled by HCL has several thin discs stacked up to form a disc which is rotated to control the flow rate. The disc remains inclined even at the fully closed condition. The advantage of the inclined disc is that it is more resistant to bending of the shaft, and thus is leak-proof at the fully closed condition. In the model above, we can see the slots provided for the bearings, seals, spacers and circlips. On the top flange, a motor assembly will be seated and screwed to the holes provided on the top flange. For the insertion of the stripes into the body, circular cuts are provided. Initially the cut was given throughout the body, but this method was not up to requirements because it did not provide proper sealing between the surface and the disc. Hence, this method was rejected and the cut was provided at only the inlet side. The concept is to drive the disc stripes by an electrical motor.

Best Practices:

It was a challenge to find the opening area for the flow between the valve body and the disc. The best practice for design of valves is to create a solid model and find the opening flow area at various angular openings. The disc edges are extracted using an option convert entities onto a plane, as shown below in Fig. 2.



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Fig 2: The disc edges extracted using an option Convert Entities After finishing the sketch, a new part is created inside an assembly with the extracted edges of the disc, as shown in Fig. 3.

Fig 3: Assembly with the extracted edges of the disc Now the sketch is modified with respect to the inner diameter of the pipe, and the sketch is modelled as shown in Fig. 4.



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Fig. 4. Sketch is modified w.r.t. the inner diameter of the pipe After finishing the model, the flow area is calculated from the section generated as shown below in Fig. 5.

Fig. 5: Section generated for flow area calculation



10

Fig. 6: The solid model for the flow area

Fig. 7: Various valve designs The graph in Fig. 8 indicates the flow area of the valve at various angular openings. Here, the angular position is represented on the X-axis and the flow area is represented on the Y-axis.



11

Fig. 8: Flow area versus angular opening for various valves The opening areas, when plotted with reference to the angular opening of the valve, give an idea as to whether the valve is opening suddenly or gradually. From this curve as plotted, we learn about the valve characteristics. This saves several runs for the CFD. However, the final configuration of the valve selected may be used for the CFD analysis to benchmark the hand calculations with the CFD results. Fig. 9: Valve % flow area versus disc opening

0

20

40

60

80

100

120

0° 10° 20° 30° 40° 50° 60° 70° 80° 90°

% Area for Pd = 32

% Area for Pd = 34

X-Axis; %Openingv/s

Y-Axis; % Area

Ф=20º

Sd=38mm



12

The graph in Fig. 9 shows the variation of the %Area of opening with respect to the change in pipe radius values. Also, we can observe the results of the inclined disc valve with respect to the vertical valve. From Fig. 9 we can observe that, with the same spherical surface, we can achieve higher flow co-efficient values by varying the pipe diameter respectively

Angle of inclination, Ф = 20º

Sphere dia, (Sd) Pipe dia, (Pd) Sd / Pd

38mm 32mm 1.188

38mm 34mm 1.118

38mm 36mm 1.056

Common Issues

The simple calculation for finding the torque value of this valve is shown below.

Input

Volts in 'VDC' 28

Amphere 'Amps' 0.8

Power(P) 'W' V*I

23

Max./Min. Operating time

9secs/6 Secs

Max. RPS (1/4rev/6 Secs)= (1/24) rps

RPM =1/24*60 = 2.5

w(Rad/sec)= 2.Pi. N/60

= 0.2617

Torque in N-m = Power/ w = 87.88

From the calculations above, it is concluded that the motor required will be 28 Volts with 0.8 Amps current. Thus the power required will be 23 Watts. The opening time will be 6 to 9 seconds. The max RPM will be 2.5 and the torque will be T=Power/w = 88 N-m



13

Advantages:

• The major advantage of this valve is it is provided with a

spherical surface inside the pipe/body; this helps provide a

better sealing condition.

• The second advantage of this system is the stripes (discs)

assembled with inclination. They provide the opening area

at a very early stage, i.e. at a minimum degree of rotation.

• The cuts are provided only on one side of the pipe up to the

centre line of the shafts so the stripes will not slip on the

other side; the spherical shape prevents slippage of the

stripes.

• The system is comprised of single-piece body, hence there

is no leakage problem. This gives greater system stability.

• The discs are provided with a heat treatment process,

hence there is no problem of wear and tear, thus the life of

the system is improved.

• No special kind of seal is required for this system because

the disc itself will act as a tight seal.

• Full Cv can be varied by changing the sphere radius.

• The valve system is provided with position control sensors

which control the rotation of the shaft based on the signals

from the actuators.

Limitations:

• Temperature limited to seat/disc material used

• More wetted parts exposed to fluids. Exotic materials can

result in added expense

• Not generally used in dirty services without options to

eliminate introduction of particles into the pipe

• High maintenance costs

• More expensive than other valves.



14

Conclusion

Using the valve to control pump flow causes a loss in energy, hence

the concept of an engageable and dis-engageable impeller pump is

good for the purpose of energy saving and meeting the

requirements of varying flow and pressure.

Reference

1. The source for this white paper is the HCL internal project at

the Aero Delivery Unit. This is not related to work for any

customer.

Author Info

Chandrasekaran S R

HCL Technologies, Ltd., Bangalore.

Has earned his Master’s degree in Mechanical Engineering and has over 38 years of experience in a premier Research and Development Organization. His entire service was in the R&D Organization and India defense.

His trainings and additional qualifications are

MBA (HRD),SFI (West Germany-Welding Specialist Engineer from Welding Research Institute, Hamburg), AM Ae SI (Design and Production)

Dr. R. S. Madhusudan,

Head Solutions & Group Technical Specialist,

HCL Technologies, Ltd., Bangalore.

Dr. Madhusudan earned his Masters and

Doctorate degrees in Mechanical Engineering from

IIT Madras. He has 25 years of experience in

developing new products in hydraulics.

Karunakara Talawara,

Technical Lead, HCL Technologies, Ltd.,

Bangalore.

He earned his Masters degree in Mechanical

Engineering (Turbo machines) from IIT Madras,

and has 10 years of industrial experience with

OEMs in centrifugal pumps and positive

displacement pumps



15

Ashok Manohar Pujar,

Group Project Manager, HCL Technologies, Ltd.,

Bangalore

He earned his Masters in Technology from

Visveswaraiah Technological University, Belgaum.

He has 17+ years of experience in a variety of

fields. His specialization is in hydraulics, and he has

worked on industrial and defense related hydraulic

systems development, valves, and actuator design.

Sharan Babu K.,

Member Technical Staff, HCL Technologies, Ltd., Bangalore.

He earned his Bachelor’s degree in Mechanical

Engineering from Visveswaraiah Technological

University, Belgaum. He has 2+ years of industrial

experience in gears, shafts and pinions, valves

and rotating equipment for petrochemical

applications.

.

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inclined disc spherical case: butterfly valve · fig. 5: section generated for flow area...

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