INTRODUCTION AND DESIGN OF CONICAL TYPE DRAFT TUBE

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 06 Issue: 01 | Jan 2019 www.irjet.net p-ISSN: 2395-0072

SHELKE KRUSHNA

, PATIL MIT

, WARKE NILESH

, AVINASH JEJURKAR

1,2,3

BE Scholar, Department of mechanical engineering, PRE’S, S.V.I.T. Nasik, MH, INDIA

ME Scholar, Department of mechanical engineering (Design), PRE’S, S.V.I.T. Nasik, MH, INDIA

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Abstract - Day by day hydraulic power plants are goes on

increasing. So it is necessary that we should be focus or

concentrate on design of turbine parameters. Basically there

are so many types of water turbines are present in everywhere.

For example pelton wheel water turbine, Francis water

turbine, tidal, Kaplan water turbine. In the reaction turbine

draft tube is necessary part of turbine. Because of it permits

the negative head to establish at outlet of runner, hence it

increases the net head available to turbine. Also it converts

kinetic energy of water at exit of runner into pressure energy

so that useful head at runner exit is increased .utilization of

kinetic energy at exit of runner increase the power output and

efficiency of the turbine. Apart from this, the location of

turbine level close to tail race level could cause the flooding of

turbine during rainy season. That’s why it is necessary to

design and analyze draft tube. In this paper we are going to

focus on importance and design of draft tube.

Key Words- Hydraulic power, Kaplan turbine, draft tube,

tail race, runner.

1. INTRODUCTION

The water is passing through runner to tail race

through the draft tube. Draft tube is pipe type or passage of

gradually increasing cross sectional area which connects

runner exit to tail race. The material of draft tube cast or

plain steel or may be concrete. Draft tube has two purposes

i) It permits suction head at a runner exit. ii) It converts

velocity energy into pressure energy at the exit.

1.1 Types of draft tube:

a) Conical type draft tube

b) Moody spreading tube

c) Simple elbow tube

d) Elbow tube have circular c/s at inlet & rectangular

atoutlet

Fig no.(1) Different types of draft tube

1.1.1 Conical type draft tube:

Taper angle of divergent portion of tube is great

importance. If taper angle, 2Ɵ is large it will be cause

separation of flow from wall of draft tube. In case taper angle

is small, length of draft tube needed long. Angle Ɵ is always

less than or equal to 10. This type of draft has more

efficiency, which is 90%.

1.1.2 Moody spreading tube:

It is similar to conical draft tube which is shown in

above fig(b). It is provided with a solid central core which

reduces the whirling action of water. It has efficiency up to

85% and it is used for vertical shaft turbine having large

whirl component at exit of their runner.

1.1.3 Simple elbow tube:

It is circular cross section throughout from inlet to

outlet shown in above fig(c). Which is turned through 90

degree? This draft tube is used in Kaplan turbine. These

tubes reduce depth and cost of system. It is made of concrete

and having efficiency up to 60%.

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 06 Issue: 01 | Jan 2019 www.irjet.net p-ISSN: 2395-0072

1.1.4 Elbow tube has circular c/s at inlet & rectangular

at outlet:

it is circular in cross section at inlet ant rectangular

at exit of draft tube. Horizontal portion of tube is gradually

inclined upwards so that water leaves the tube almost at tail

race level. In this case cost and depth is also reduced. The

efficiency of these draft tube in the range of 60 % to 80 %. It

is also made with concrete.

2. DESIGN OF CONICAL DRAFT TUBE:-

In this paper we are focusing on conical draft tube,

as name suggest shape of conical is conical that is increasing

cross section from top to bottom. Taper angle of divergent

portion of tube is great importance. If taper angle, 2Ɵ is large

it will be cause separation of flow from wall of draft tube. In

case taper angle is small, length of draft tube needed long.

Angle Ɵ is always less than or equal to 10[1]. This type of

draft has more efficiency, that is 90%[1]

Conical draft tube Fig no. (2)

Height of draft tube is normally,

H= 4*d

From fig points 1, 2 & 3 have been consider at runner entry,

exit and at outlet end of draft tube respectively. By applying

Bernoulli’s equation between point 1 and 2 .

/W) + (V

/2*g) + Z

= (P

/W)+(V

/2*g) + Z

But as we know,

/W) = (P

/W) + h

- Z

- h = H

/W) = (P

/W) - [H

+ (V

-V

)/2*g] + h

Efficiency of draft tube,

= [(V

-V

)/2*g] - h

3. CONCLUSION

Draft tube is necessary part of Kaplan turbine.so

there are so many type of draft tube. But conical type of draft

is the best. Because, it gives higher efficiency about 90 % and

also construction % design is very simple.

REFERENCES

1. Shubham M. Harde, Shubham Thakare, Shubham A.

Shende, Swapnil Pardhikar, Prof. Shailendra Daf,

‘‘Effect of Draft tube on Hydraulic turbine’’, volume

1, ISSUE 4, ISSN : 2455-2631, April 2016.

2. Lekha Mourya, Rahul Mishra, Swapnil Jain,

‘‘Analysis on hydraulics performance of Kaplan

turbine based on elbow draft tube geometry’’,

volume 05, ISSUE 6, ISSN: - 2321-9653, JUNE 2017.

3. Sumeet J. Wadibhasme, Shubham Peshne, Pravin

Barapatre, Santosh Barade, Saurabh Dangore,

Shubham Harde, Prof. Shailendra Daf., ‘‘Hydraulic

turbine draft tube : literature review’’, volume 5,

ISSUE 5, ISSN :- 2278-7798, March 2016.

4. Vikas Rai, Nishant Vibhav saxena, ‘‘A Review on

advance in the design and analysis of draft tube for

reaction turbines’’, volume 5, issue 5, e-ISSN : 2395-

0056, p-ISSN : 2395-0072, May 2018.

5. D.S. Kumar, ‘ Fluid mechanics and fluid power

engineering’.

6. P.N. Modi and S.M. Seth, ‘Hydraulic and fluid

mechanics including Hydraulic machines’.

BIOGRAPHIES

SHELKE KRUSHNA VISHWAS, BE,

MECHANICAL ENGINEERING,

PRE’S,SVIT,NASIK,MH,INDIA

“PATIL MIT PRAKASH, BE,

MECHANICAL ENGINEERING,

PRE’S,SVIT,NASIK,MH,INDIA ‘’

“WARKE NILESH LATESH, BE,

MECHANICAL ENGINEERING,

PRE’S,SVIT,NASIK,MH,INDIA “