Galgotias College of Engineering and Technology

Department of Mechanical Engineering

Project report on

To design, fabrication & testing of gear pump test rig

By

1. SUNIL KUMAR YADAV (0809740092)2. SHRI BALLABH GOSWAMI (0809740087)3. VIVEK CHANDRA PANDEY ( 0809740099)4. SAURABH SINGH ( 0809740082 )

in partial fulfillment of

Degree Requirements as per UPTU Syllabus for the award of

Bachelor of Technology (Mechanical Engineering)

Batch of 2008-12

Galgotias College of Engineering and Technology

Department of Mechanical Engineering

CERTIFICATE

This is to certify that the project entitled “To design, fabrication & testing of gear pump test rig” submitted by Sunil Kumar Yadav (0809740092), Shri Ballabh Goswami (0809740087), Vivek Chandra Pandey (0809740099), Saurabh Singh ( 0809740082 ) to the Department of Mechanical Engineering, Galgotias College of Engineering and Technology, Gr. Noida, in partial fulfillment of Degree Requirements as per GBTU Syllabus for the award of Bachelor of Technology (Mechanical Engineering), is a record of bonafide work carried out by them. They have worked under my guidance and supervision.

Prof. Dr. M. N. Desmukh Prof. Sudip Ghatak

Deptt. of Mechanical Engineering Deptt. of Mechanical Engineering

Galgotia College of Engg. & Tech. Galgotia College of Engg. & Tech

Table of content

1. Project overview2. Literature review of project3. Technical detail4. Calculation for gear pump dimension5. Reference

1- The overview of project

A gear pump uses the meshing of gears to pump fluid by displacement.They are one of the most common types of pumps for hydraulic fluid power applications. Gear pumps are also widely used in chemical installations to pump fluid with a certain viscosity. There are two main variations; external gear pumps which use two external spur gears, and internal gear pumps which use an external and an internal spur gear. Gear pumps are positive displacement (or fixed displacement), meaning they pump a constant amount of fluid for each revolution. Some gear pumps are designed to function as either a motor or a pump.

Theory of operation

As the gears rotate they separate on the intake side of the pump, creating a void and suction which is filled by fluid. The fluid is carried by the gears to the discharge side of the pump, where the meshing of the gears displaces the fluid. The mechanical clearances are small— in the order of 10 μm. The tight clearances, along with the speed of rotation, effectively prevent the fluid from leaking backwards.

The rigid design of the gears and houses allow for very high pressures and the ability to pump highly viscous fluids.

Many variations exist, including; helical and herringbone gear sets (instead of spur gears), lobe shaped rotors similar to Roots Blowers (commonly used as superchargers), and mechanical designs that allow the stacking of pumps.

External gear pump design for hydraulic power applications.

Internal gear (Gerotor) pump design for automotive oil pumps

2- Literature Review of Project

External gear pumps are a popular pumping principle and are often used as lubrication pumps in machine tools, in fluid power transfer units, and as oil pumps in engines.

External gear pumps can come in single or double (two sets of gears)

pump configurations with spur (shown), helical, and herringbone gears.  Helical and herringbone gears typically offer a smoother flow than spur gears, although all gear types are relatively smooth.  Large-capacity external gear pumps typically use helical or herringbone gears. Small external gear pumps usually operate at 1750 or 3450 rpm and larger models operate at speeds up to 640 rpm. External gear pumps have close tolerances and shaft support on both sides of the gears.  This allows them to run to pressures beyond 3,000 PSI / 200 BAR, making them well suited for use in hydraulics.  With four bearings in the liquid

and tight tolerances, they are not well suited to handling abrasive or extreme high temperature applications.

Tighter internal clearances provide for a more reliable measure of liquid passing through a pump and for greater flow control. Because of this, external gear pumps are popular for precise transfer and metering applications involving polymers, fuels, and chemical additives.

 

How External Gear Pumps WorkExternal gear pumps are similar in pumping action to internal gear pumps in that two gears come into and out of mesh to produce flow.  However, the external gear pump uses two identical gears rotating against each other -- one gear is driven by a motor and it in turn drives the other gear.  Each gear is supported by a shaft with bearings on both sides of the gear.

1.  As the gears come out of mesh, they create expanding volume on the inlet side of the pump. Liquid flows into the cavity and is trapped by the gear teeth as they rotate.

2.  Liquid travels around the interior of the casing in the pockets between the teeth and the casing -- it does not pass between the gears. 

3.  Finally, the meshing of the gears forces liquid through the outlet port under pressure.

Because the gears are supported on both sides,

external gear pumps are quiet-running and are

routinely used for high-pressure applications such as

hydraulic applications. With no overhung bearing loads,

the rotor shaft can't deflect and cause premature wear

3- Technical detail

Gear Dimensions

Emprical formula for discharge calculation :-

Ideal discharge

Q= 2aln.N/60

Where a= the area enclosed b/w two adjacent teeth & casing

l = axial length of teeth

n = number of teeth in each pinion

N = speed in rpm

Parametric curve

Equations of an involute curve for a parametrically defined

function ( x(t) , y(t) ) are:

In Cartesian coordinates the involute of a circle has the

parametric equation:

where a is the radius of the circle and t is a parameter

In polar coordinates the involute of a circle has the parametric

equation:

where a is the radius of the circle and is a parameter

2nd emperical formula :-

Q = 0.95πC(D – C )lN

where C = the centre to centre distance b/w axis of gears

D = outside diameter of gears

l = axial length of teeth

N = speed in rpm

Outside Diameter ( D):-

D = d + 2/Pd

where d = pitch diameter

Pd = Diameterical pitch

Diameterical pitch ( Pd ):-

Pd = n/d

where n = no of teeth

d = pitch diameter

Minimum no of teeth to avoid interence :-

where n = number of teeth

x = pressure angle

4-Calculation for gear pump dimension :-

for x = 14.5

n = 23

for x = 20

n = 13

for x = 25

n = 9

For x = 30

n = 7

Table for D/C & n

D/C 1.28 1.21 1.13 1.12

n 7 10 13 18

For x= 20• , n=13, d=20 mm,

l=30, D= 23.0769 mm, C= 20.422 mm

N = 1500 rpm

Q = 7.278 lpm

for n=13, d= 25 mm

l= 37.5 mm, D= 28.84 mm, C= 25.527mm

N = 1500 rpm

Q = 14.22 lpm

For n =14 , d= 20 mm ,

l= 30 mm, D= 22.85 mm, C= 20.26 mm

N= 1500 rpm

Q = 7.056 lpm

for n= 15, d =20 mm

l= 30 mm, D = 22.666 mm, C= 20.13 mm

N = 1500 rpm

Q = 6.85 lpm

For x=30•, n= 7, d=31.11 mm,

l= 31 mm, D= 40.00 mm, C= 31.25 mm

N = 1500 rpm

Q = 38.08 lpm

For x= 30•, n= 7, d= 35 mm

l= 35 mm, D= 45 mm, C= 35.15 mm,

N = 1500 rpm

Q = 54.24 lpm

Calculation for gear dimension:-

X= 30•, n= 7, d= 35

l= d

l= 35 mm,

Pd = n/d

Pd = 7/35

Pd = 0.2,

Outside dia D = d + 2/Pd

D = 35 + 2/0.2 = 45 mm

For n=7, D/C = 1.28,

Then C = 35.15 mm,

N= 1500 rpm

Then discharge Q = 0.95*π*C(D-C)lN

Then Q = 54.24 lpm

Design of casing :-

Casing is like cylinder . Since in gear pump pressure is relatively

high nearly 200 bar . So we design a thick casing for gear pump

thickness of casing ( t ):-

Take factor of safety = 3

for grey cast iron ( FG 200) Sut= 200 MPa

Di= 40 mm

Pi = 20 Mpa

permissible tensile strength = 66.666 Mpa

then thickness t = 7.25 mm

if fos is = 4

then t = 10.55 mm

For malleable cast iron

Sut= 400 Mpa

Di = 40 mm

Pi = 20 Mpa

if f.o.s. = 3,

t = 3.26 mm

if f.o.s. = 4,

t = 4.49 mm

Gear pump parameter

Parameter Value variable How to get it

No. of teeth 7 n We choose

Pitch

(diameterial)

0.2 p n/ PD

Pressure angle 30 x Usually standard

(14.5, 20,25, 30)

Addendum dia 45 AD PD + 2*a

Dedendum dia 22.5 DD PD – 2*d

Pitch dia 35 PD WE CHOOSE

Addendum 5 a 1/p

Dedendum 6.25 d 1.25/p

Design of shaft

Pout = (ps – pd )*Q = Pin - Ploss

Take ps – pd = 25 bar

Q = 54.24 lpm = 9.04 * 10-4 m3/s

Then Pout = 2.251 kw

Generally efficiency of gear pump is 85%

So Pin = 2.251/0.85 =2.648 kw

N = 1440 rpm

T = 60*106*Pin/( 2*π*N )

Then T = 17560.095 N-mm

The permissible shear stress :-

For alloy steel , 50C4

Syt = 460 MPa , Sut = 660 MPa

Permissible shear strength = minimum of ( 0.3*460 = 138 MPa

& 0.18*660 = 118.8 MPa )

So permissible shear strength = 118.8 MPa

Then d3 = 1003.725 mm

d= 10.012 mm

d= 10 mm

References :- Hydraulic machines by Dr. Jagdish Lal published by

Metropolitan Book Co. Private Ltd. www.wikipedia.com Theory of machine by S.S. Rattan published by T.M.H Design of Machine Element by Dr. V.B. Bhandari published

by McGraw Hill.