13082013113202-mechanical-governer (1).pptx

8/10/2019 13082013113202-mechanical-governer (1).pptx

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SEMIN R ON

GOVERNOR

PRESENTED BY-

RAHUL KUMARME 7TH SEM


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Performance Objectives

Students will be able to list and describe thepurpose and types of governors found onsmall gasoline engines


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Enabling Objectives

Given the instruction in class the student willbe able to list, describe, and define thepurpose of the following small enginegovernors with 80% accuracy.PneumaticCentrifugalVacuum


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Interest Approach

What purpose does the governor serve on asmall engine?

Have any of you ever unhooked the governoron a small engine such as on you go-cart?

What affect did it have?


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Governors

Governors serve three basic purposes:Maintain a speed selected by the operator

which is within the range of the governor.Prevent over-speed which may cause enginedamage.

Limit both high and low speeds.


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Governors

Generally governors are used to maintain afixed speed not readily adjustable by theoperator or to maintain a speed selected bymeans of a throttle control lever.

In either case, the governor protects againstoverspeeding.


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How does it work?

If the load is removed on an operatingengine, the governor immediately closes thethrottle.If the engine load is increased, the throttlewill be opened to prevent engine speed formbeing reduced.


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Example

The governor on yourlawnmower maintainsthe selected engine

speed even when youmow through a clumpof high grass or whenyou mow over no grass

at all.


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Pneumatic Governors

Sometimes called air-vane governors, theyare operated by the

stream of air flowcreated by the coolingfins of the flywheel.


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Air-Vane Governor

When the engine experiences suddenincreases in load, the flywheel slows causingthe governor to open the throttle to maintainthe desired speed.The same is true when the engineexperiences a decrease in load. The governorcompensates and closes the throttle toprevent overspeeding.


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Centrifugal Governor

Sometimes referred toas a mechanicalgovernor, it uses

pivoted flyweights thatare attached to arevolving shaft or geardriven by the engine.


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Mechanical Governor

With this system, governor rpm is always directlyproportional to engine rpm.


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Mechanical Governor

If the engine is subjected to a sudden loadthat reduces rpm, the reduction in speedlessens centrifugal force on the flyweights.The weights move inward and lower thespool and governor lever, thus opening thethrottle to maintain engine speed.


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Vacuum Governors

Located between the carburetor and the intakemanifold.It senses changes in intake manifold pressure(vacuum).


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Vacuum Governors

As engine speed increases or decreases the governorcloses or opens the throttle respectively to controlengine speed.


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Hunting

Hunting is a condition whereby the enginespeed fluctuate or is erratic usually when firststarted.The engine speeds up and slows down overand over as the governor tries to regulate theengine speed.This is usually caused by an improperlyadjusted carburetor.


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Stability

Stability is the ability to maintain a desiredengine speed without fluctuating.

Instability results in hunting or oscillating dueto over correction.Excessive stability results in a dead-beatgovernor or one that does not correctsufficiently for load changes.


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Sensitivity

Sensitivity is the percent of speed changerequired to produce a corrective movementof the fuel control mechanism.

High governor sensitivity will help keep theengine operating at a constant speed.


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Summary

Small engine governors are used to:

Maintain selected engine speed.Prevent over-speeding.Limit high and low speeds.


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Summary

Governors are usually of the following types:Air-vane (pneumatic)Mechanical (centrifugal)Vacuum


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Summary

The governor must have stability andsensitivity in order to regulate speedsproperly. This will prevent hunting or erraticengine speed changes depending upon loadchanges.

13082013113202-mechanical-governer (1).pptx

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