Governor characteristics

1.  COLLEGE OF ENGINEERING AND TECHNOLOGY
 DEPARTMENT OF MECHANICAL ENGINEERING
 COURSE NAME; MECHANISMS OF MACHINERY
 COURSE CODE;MEng3071
◦ GROUP ASSIGNMENT
 NAME ID NUMBER
 HUNDUMA CHALA RU0773/12
 FIROMSA WERKU RU1099/12
 GELETA BULCHA RU2443/12
 BIKILA SHUMETA RU2090/12
 GUTEMA GENALE RU1702/12
◦ SUBMITTED BY TESFAYE
◦ SUBMISSION DATE 27/5/2014

2.  INTRODUCTION
 reciprocating engines, the turning moment on the crankshaft
is subject to cyclic variation which result in periodic
fluctuation of engine speed. This fluctuation of speed
regulated by the use of governors among others.
 An engine governor is a conbination of interacting elements
which automatically maintain engine speed within assigned
limits.
 A governor comprises a sensitive element that reacts to
change in speed by shifting corresponding sleeve linked to a
control member thereby increasing the fuel when the load
increases and vice-versa.

3.  Governors are broadly classified into two categories
depending on the controlling force acting on the governor.
1. centrifugal governors(loaded governors) and
2. inertia goverors,
 Centrifugal governors, the controlling force is due to the
centrifugal force acting on the control element- are two
types:-
1. dead weight governors
2. spring loaded governors
 Inertia governors, the control is achieved by means of inertia
force acting on the control element.

4.  To regulate speed, a governor must posses certain qualities.
 A governor has to maintain the mean speed of the rotating
member by floating in the mean position between extreme
positions.
 At the same time, it must readily respond to changes of
speed.
 The characteristics that are related to the proper functioning
of a governor are stability and sensitivity. These
characteristics affect the controlling force of the governor.

5.  Controlling force
 is centrifugal governors is the equivalent inward redial force
that controls ball movement. Wich is due to sleeve weight ,
spring force etc…
 Depend on the horizontal radial position of the balls ,a
governor is said to be stable when there is one radius of
rotation of the balls for each speed which is within the speed
range of the governor.

6.  Stabity
 If the governor is stable and the balls are slightly
displaced from the equilibrium position. Sensitivity
 Sensitivity
 it is define as the extent of sleave movement for a
change in speed of the governor.
 as a governor is used to limit the change of speed of
the engine between a minimum to full load
conditions the sensitiveness is also defined as the
ratio of the range of speed to the mean equilibrium
speed.

7.  Isochronous Governors
 A governor is said to be isochronous when it is
infinitely sensitive.
 the controlling force curve becomes a straight
line coinciding with the centripetal force.

8.  Effort of Porter Governor
 The effort of the Porter governor is the force which
it is capable of exerting at the sleeve for a given
percentage or fractional change of speed.

9.  The Porter governor is a dead weight governor and is
illustrated .
 As the speed of the shaft increases, the balls move
outward raising the sleeve height, and viceversa.
 The controlling load is attached to the sleeve.
 in porter governor two balls are located at the top and
load is attached to the sleeves.

10.  the lower link is connected to central sleeve and two
stoppers are proided to control the movements of sleeves.
 a mechanism is attached to the sleeves to operates the
throttle value.
 the balls tend two moves up and down on the spidle due
to the speed of revolution of the spindle.as load at the
engine decreases speed of the engine as well as spindle
also tends to increases

11.  A Hartnell governor is a spring loaded governor
 consists two bell cranks situated the different
points of the frame.
 a frame is attached to the spindle each lever carries a ball to the
horizontal roller at the end of vertical arm.
 the helical ring is provided to maintain the equal level force on the
rollers and arrangement of the screw is there to adjust a force of
the spring.
 is a spring controlled centrifugal governor.

12.  Shaft governors are directly fitted on the main shaft of
the engine and the masses revolve at right angles to the
shaft axis which in general is horizontal.
 Shaft governors are classified into two as
a) centrifugal flywheel governors, and
b) inertia governors
 Both shaft governors operate by a combination of radial
and transverse accelerating forces.

13.  Inertia governors are operated by the rate of
change of speed in stead of the finite change
of speed.
 For some rate of change of speed, the link
carrying the two balls will start to move
causing the spring to deflect.