Cam actuated rotary pump

International Journal For Research & Development in Technology

Volume: 2, Issue: 1, JULY-2014 ISSN (Online):- 2349-3585

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Copyright 2014- IJRDT www.ijrdt.org

CAM ACTUATED ROTARY PUMPAravind S1,Aswin Raj. M.2, C R Rahul3,

Dileep S4, Nandu S5

12345 Department Of Mechanical Engineering,

Saintgits College of Engineering, Kottayam,Kerala.

Abstract- The aim of this project is to design a positive

displacement rotary pump for small scale applications. The

design is in such a way that it combines the advantages of

both rotodynamic and positive displacement pumps.

Currently available centrifugal pumps cannot attain high

heads, and reciprocating pumps are less efficient and

requires much space. When centrifugal pump is used as a jet

pump, it delivers fluids at a high head, but in the expense of

efficiency.

To overcome these negatives of currently available pumps, a

new design of a rotary type positive displacement pump is

developed. This design imitates the working of a normal

reciprocating pump, but in a rotary action. This consumes

less space compared to a reciprocating pump of same

capacity. The main part of the pump is a cam which is

mounted on a rotating shaft that rotates in a cylindrical

casing. The cam is designed in such a way that it always

maintains contact with the walls of the casing as it rotates. A

spring loaded blade acts as the cam follower and moves in

an accurately machined slot in the casing. The blade and the

slot are of rectangular cross section. This blade separates

suction and delivery sides of the pump. Inlet and outlet ports

are placed on either sides of this blade. This pump does not

require inlet and outlet valves. The discharge from the pump

is continuous. It also eliminates the crank and connecting-

rod mechanisms and delivers a smooth operation.

Keyword:- Rotary Pump, Rotating Shaft, Cam, Follower

blade.

I.INTRODUCTION

Pumps are hydraulic machines which convert

mechanical energy into hydraulic energy. Pumps operate by

some mechanism (typically reciprocating or rotary), and

consume energy to perform mechanical work by moving the

fluid. Pumps operate via many energy sources, including

manual operation, electricity, engines, or wind power, come in

many sizes, from microscopic for use in medical

applications to large industrial applications.

Mechanical pumps serve in a wide range of applications such

as pumping water from wells, aquarium filtering, pond

filtering and aeration, in the automobile industry for water

cooling and fuel injection, in the energy sector for pumping

oil and natural gas or for operating cooling towers. Centrifugal

pumps are widely being used in house hold applications where

low heads are required. These pumps deliver fluids at a

constant rate. These are very compact and require less

maintenance. But for applications where high heads are

required centrifugal pumps are inadequate. Modifying a

centrifugal pump as a jet pump enables pumping at high head,

but at the cost of efficiency.

Reciprocating pumps are well known for their ability to

achieve very high head. But the discharge from such pumps is

pulsating. Reciprocating pumps occupy large floor space as

the number of components is more. The initial cost is high and

requires high maintenance. So their application is mainly

confined to industrial fields.

The prime objective of this project is to develop a rotary type

positive displacement pump which can be used to pump fluids

at relatively higher heads. The design is focussed in reducing

the number of parts and in turn the overall size. It also aims at

smooth running and constant delivery of fluid. For use in

household applications, the pump should operate with

minimum noise and vibration levels. There should be

minimum maintenance requirements also. A positive

displacement pump can attain high heads while the rotary

operation leads to smooth noiseless operation.

II. DESIGN APPROACH

A. Power requirements

For starting the design process, it is necessary to set some

required output parameters. An ordinary household centrifugal

pump used to pump water from well was used for comparison.

The specifications of the pump were obtained from the name

plate. The driving motor was of rated power 373 W, and the

flow rate indicated was 0.0007 m3 per second. The maximum

head attainable was 12 meters of water. So the desired head

was set as 12 meters and flow rate as 0.0007 m3/s of water.

These values are used in calculating the power required to

pump water.

Required head = 12 m.

Required discharge = 0.7 x 10-3

m3 / s

Power required for pumping (theoretical)

Ppumping = ρgHQ

= 1000 x 9.81 x 12 x 0.7 x 10-3

= 82.404 W

This is the theoretical power required in pumping water for

above mentioned head and discharge. But a machine cannot be

100% efficient. So the actual value of input power required

will always be greater than theoretically calculated value.

Thus efficiency factor comes into play.

Assuming pump efficiency as 25%

Power, P = Ppumping

ηpump

http://en.wikipedia.org/wiki/Reciprocating_motion

http://en.wikipedia.org/wiki/Rotation

http://en.wikipedia.org/wiki/Energy

http://en.wikipedia.org/wiki/Mechanical_work

http://en.wikipedia.org/wiki/Engines

http://en.wikipedia.org/wiki/Wind_power

http://en.wikipedia.org/wiki/Water_well_pump

http://en.wikipedia.org/wiki/Aquarium_filter

http://en.wikipedia.org/wiki/Pond



http://en.wikipedia.org/wiki/Aeration

http://en.wikipedia.org/wiki/Car_industry

http://en.wikipedia.org/wiki/Water_cooling



http://en.wikipedia.org/wiki/Fuel_injection

http://en.wikipedia.org/wiki/Pumping_(oil_well)



http://en.wikipedia.org/wiki/Natural_gas

http://en.wikipedia.org/wiki/Cooling_tower


Paper Title:- Cam Actuated Rotary Pump (Vol.2,Issue-1) ISSN(O):- 2349-3585

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= 82.404

0.25

= 329.616 W

So, a commercially available motor of (0.5 hp) 373 W was

selected to drive the pump shaft. The motor works on AC

supply. A single phase motor was selected because a three

phase supply is not available everywhere.

B. Speed calculations

Calculating the power required is not sufficient in selecting

the driving motor. Speed of the pump shaft is necessary in

determining the type of motor required. Since this is a positive

displacement pump, required speed of the shaft can be directly

obtained from required flow rate. But it is necessary to set

some dimensions arbitrarily to start with. Some of the

dimensions were set and used in the following calculation.

Those dimensions are described in the following chapters. The

swept volume in one revolution of shaft was calculated using

software.

Swept volume for 1 revolution of shaft,

V = 0.000044178 m3

Discharge, Q = V x N

60

Speed, N = Q x 60

V

= 0.0007 x 60

0.000044178

= 950 rpm

≈ 960 rpm

C. Design of belt drive

Shaft speed required was calculated in the previous section.

But the problem was that, a low cost motor running on AC

supply at 960 rpm was difficult to find in market. So, an easily

available, 0.5 hp (373 W) motor running at 1440 rpm was

selected and bought. To reduce this speed from 1440 rpm to

960 rpm, the use of a suitable reduction mechanism became

necessary. Considering low cost and other factors, v-belt and

pulley mechanism was adopted. The design of belt drive

(figure 3.1) is carried out below.

Driver shaft speed, N1 = 1440 rpm

Driven shaft speed requirement, N2 = 960 rpm

Driver pulley diameter, d = 0.0508 m

Driver ratio = d

D =

N2

N1

= 960

1440

= 0.6666

Driven pulley diameter, D = d

0.666

= 0.0508

0.666 = 0.0762 m

Radius of driver pulley, r = d

2

= 0.0508

2 = 0.0254 m

Radius of driven pulley, R = D

2

= 0.0762

2 = 0.0381 m

Thus the dimensions of the driven and driver pulleys

were calculated. Now the dimensions of the belt have to be

found out. Calculations are as follows:

Angle α = sin

-1 (R-r)

C

= sin

-1 (0.0381-0.0254)

0.15

C is the center distance = 0.15 m

α = 4.85 deg = 0.084 rad

Length of the belt,

L = π (R+r) + 2 α (R-r) + 2 C cos α

= π(0.0381+0.0254) +2 x 0.084(0.0381-

0.0254)+2 x 0.15x cos (4.85)

= 0.4986 m

≈ 0.50 m

For designing shaft of the pump, the loads acting on the shaft

needs to be calculated. On mounting pulleys on the shaft, it is

subjected to a torque and bending moment due to belt

tensions. Calculations are as follows:

Ratio of belt forces, T1

T2

= eµ’θ

Smallest wrap angle θ = 180 - 2α

= 180 - (2 x 4.85)

= 170.3 deg

= 2.97 rad

µ’ = effective friction coefficient = 𝜇

sin β

2

β = pulley groove angle = 40 deg

µ = coefficient of friction = 0.3

µ’ = 0.3

sin 40

2

= 0.877 T1

T2

= eµ’θ

= e0.877*2.89

= 12.61

Torque transmitted to driven shaft

= Torque transmitted by the driver x D

d

Torque, T = P x 60

2π N1

x 3

2

= 373 x 60

2 π x 1440 x

3

2

= 3.71 Nm

T1 - T2 = 3.71

R

= 3.71

3.81 x 10-2

= 97.37 N

Therefore, T1 = 105.75 N

T2 = 8.38 N

Shaft load, F = T1 cos(α) + T2 cos(α)

= 105.75 cos (4.85) + 8.38 cos (4.85)

= 113.72 N

D. Design of shaft



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It is already seen that the pump shaft is subjected to a turning

moment as well as a bending moment. The magnitudes of the

same have been found out in the previous section. Using those

values the design of the shaft is carried out.

Using maximum shear stress theory:

Π

16 x Гmax x ds

3 = (M

2 + T

2)

ds= Diameter of the shaft

T = Torque transmitted = 3.71 Nm

M = Bending moment acting on shaft.

= F x (Overhanging length) = 113.72 x 40 x 10-3

= 4.54 Nm

Assume Гmax = 56 MPa

On solving for ds:

ds = 0.00810 m

≈ 0.010 m

Thus the designing of all required components has

been carried out. The loads acting were calculated and applied

in finding out the safe dimensions of all key parts.

III. COMPONENT DESCRIPTION

A. Cam

The main component of the pump is a cam (Fig. 5.1). The

design aspects of the cam were calculated. The design of the

cam is in such a way that it always maintains the contact with

the walls of the cylindrical casing as it rotates. There is a

provision provided on the cam to insert the shaft onto it. The

cam is mounted on the rotating shaft which rotates inside the

casing.

Fig. 1. Cam

The rotation of the cam inside the casing creates the vacuum

which leads to the suction of fluid into the pump casing. The

cam was casted in aluminium. The material selection for the

cam was made aluminium in order to reduce the weight.

B. Cylindrical casing

The engine sleeve is selected as the casing for the cam inside

which it provides a smooth rotation. In order to provide

adequate strength to the engine sleeve a Galvanized Iron pipe

is used as the outer casing. The GI pipe was made tight fit

with the engine sleeve.

The assembly of the engine sleeve and the GI pipe was turned

in lathe to required dimensions (Fig. 2). The casing has an

inner diameter of casing 70 mm and length of the casing is 36

mm. The inlet and outlet ports were drilled on the periphery of

the casing.

Fig. 2. Cylindrical casing

A rectangular slot was also made on the periphery of casing in

order to enable the movement of the follower blade. This slot

should keep tight tolerances for the sliding movement of the

rectangular blade otherwise there will be excessive leakage.

C. Blade

Fig. 3 Follower blade

The blade (Fig. 3) is a component that separates the suction

and delivery side of the pump. The blade too was made from

aluminium, in order to reduce the wear as it is always in

contact with the rotating cam. The blade has a rectangular

cross section of length 80 mm, width 30 mm and thickness 6

mm as its dimensions. The blade reciprocates in the slot

provided on the casing.

D. Side walls

It is made of mild steel plate. It was turned in the stepped form

and made tight fit with the casing (Fig. 4). It has a step

thickness of 3mm and stepped portion has a diameter of

70mm, with outer diameter 76mm. The two side walls provide

air tight chamber in the casing. It also houses the seat for the

two bearings.



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Fig. 4. Side walls

E. Motor

A single phase AC induction motor (Fig. 5) is used to impart

power to the motor shaft. Power rating of the motor is 5 HP

(0.37kW) at 1440 rpm.

Fig. 5. Driving motor

IV. WORKING

This section explains the working principle of the pump. The

following figures show how the fluid is sucked into the cavity

and how it is pumped out to a higher level. As from the Fig. 6

(a) below, the water is sucked in during the counter clockwise

rotation of the cam. This is due to the fact that the volume of

the cavity keeps on increasing with the counter clockwise

rotation of the cam creating a vacuum pressure inside the

cavity. In the Fig. 6 (b) the apex of the cam is at top,

displacing the follower blade to maximum. At current

position, the whole cavity is filled completely by water. Now

suction process is complete.

In the last Fig.6 (c), further advancement of the cam anti

clockwise pushes the water out via the outlet port, which is

connected to the delivery pipe. Again, this cycle continues and

water gets pumped continuously. This is the basic working

principle behind the cam actuated rotary pump. The rate of

discharge depends upon the speed of rotation of the shaft.

(a)

(b)

(c)

Fig. 6. Working principle

V. RESULTS AND DISCUSSIONS

A cam actuated positive displacement pump is

designed and fabricated. The pump operates smoothly. It has

less noise and vibration. The delivery is at a constant rate. The

suction and discharge happens simultaneously. The absence of

unidirectional valves and other linkages like crank and

connecting rods reduce the complexity and floor space

required.



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The pump was tested for measuring actual discharge and head

developed. A pressure gauge of range 0-7 kg/cm2

was

mounted on the delivery pipe. A 0.3 m x 0.3 m measuring tank

was used to measure actual discharge. Pump was coupled to

electric motor through v-belts and pulleys. Motor was run at

rated speed and rise in water level was noted. Maximum

pressure developed was obtained from pressure gauge reading.

Observations were used for evaluation of performance.

Performance curves were plotted and explained below.

Fig. 7. Flow rate vs Head

The discharge was found to be decreasing with increase of

head (Fig. 7). This is mainly due to the increase of leakage

around the cam with increase in pressure. The tolerances are

not close enough to seal the leakages. There is excessive

leakage through the rectangular groove provided for the

movement of the follower blade, at high pressures.

Fig. 8. Output power vs Head

Output power Vs head developed shows that output power

first increases, and then decreases with increasing head (Fig.

8). This is because initially, drop in discharge with increasing

head is gradual. After that the discharge drops steeply.

Fig. 9. Volumetric efficiency vs Head

The volumetric efficiency vs head curve (Fig. 9) follows the

same pattern as that of flow rate vs head. The reasons behind

this nature are already explained earlier. Further increasing of

pressure was not carried out during testing because leakage

was much higher and discharge was very small.

Finally, from above findings it was observed that the

prototype of the pump could achieve a maximum head of 5.5

meters of water and delivery of water at a maximum rate of

0.27 litres of water. The peak volumetric efficiency obtained

was 38.5 %. The performance curves were plotted and were

discussed. The results are concluded, in the next section.

VI.CONCLUSIONS

A new type of positive displacement pump was developed,

which does not require inlet and outlet valves. The discharge

from the pump is continuous. It also eliminates the crank and

connecting-rod mechanisms. This has the advantages of

continuous delivery of fluid, smooth and noiseless operation

and compact size.

The expectations were that the new design can develop high

heads without much variation in flow rate. But it did not

develop head as expected and discharge was dropping rapidly

with increase of pressure. The main reason behind this is

excessive leakage past the seals. There was leakage through

sides of the cam and also through the rectangular slot provided

on the cylindrical casing for the sliding of the follower blade.

But if close tolerances are kept, this pump can work as

expected. It should be also noted that this type of pump will be

more suitable in pumping of viscous fluids, where effect of

sealing problems can be reduced to some extent.

From performance curves, the observed trends were similar to

the usual trends of most of the positive displacement pumps.

As expected, the discharge as well as volumetric efficiency

dropped with increase in head.

REFERENCES

[1] Burkhard Verhuelsdonk, 2005, “Increasing the

operational lifetime of rotary lobe pumps”, World

Pumps, September 2005.

[2] Hua Yang et al., 2011, “Study on leakage via the radial

clearance in a novel synchronal rotary

0

0.05

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Flo

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0-5

m3)

Head (m of water)

0

1

2

3

4

5

6

7

8

0 2 4 6

Outp

ut

po

wer

(W

)

Head (m of water)

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10

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c ef

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