A.D. PATEL INSTITUTEOF

TECHNOLOGY

DESIGN OF FLYWHEEL

Prepared by:-

Dhiren P. Patel(120013119002)

INTRODUCTION• FLYWHEEL:-

• A flywheel is an inertial energy-storage device.

• It absorbs mechanical energy and serves as a reservoir, storing energy

during the period when the supply of energy is more than the requirement

and releases it during the period when the requirement of energy is more

than the supply.

FLYWHEELS-FUNCTION NEED AND OPERATION

• The main function of a fly wheel is to smoothen out variations in the

speed of a shaft caused by torque fluctuations. If the source of the driving

torque or load torque is fluctuating in nature, then a flywheel is usually

called for. Many machines have load patterns that cause the torque time

function to vary over the cycle. Internal combustion engines with one or

two cylinders are a typical example. Piston compressors, punch presses,

rock crushers etc. are the other systems that have fly wheel.

• Flywheel absorbs mechanical energy by increasing its angular velocity

and delivers the stored energy by decreasing its velocity.

FLYWHEEL MATERIALS

Traditionally, flywheel are made of cast iron. From design consideration, cast iron flywheel offer the following advantages:-

• Cast iron flywheels are the cheapest.• Cast iron flywheel can be given any complex shape without involving

machining operations.• Cast iron flywheel has excellent ability to damp vibrations.

however, cast iron has poor tensile strength compare to steel. The failure of cast iron is sudden and total. The machinability of cast iron flywheel is poor compared to steel flywheel.

DESIGN APPROACH There are two stages to the design of a flywheel.

• First, the amount of energy required for the desired degree of smoothening

must be found and the (mass) moment of inertia needed to absorb that energy

determined.

• Then flywheel geometry must be defined that caters the required moment of

inertia in a reasonably sized package and is safe against failure at the designed

speeds of operation. Design Parameters:-• It depend upon acceptable changes in the speed.Speed fluctuation:-• The change in the shaft speed during a cycle is called the speed

fluctuation and it is given byFl =ωmax−ωmin

DESIGN OF FLYWHEEL

Design Equation:-IS

where “Cf”is the co-efficient of speed fluctuation and “Ek”is the kinetic energy and “avg” is the average rotational motion.Torque Variation and Energy:-The required change in kinetic energy Ek is obtained from the known torque time relation or curve by integrating it for one cycle and it is given by

d=Ek

GEOMETRY OF FLYWHEEL

• It can be a solid cylindrical disc.

• It can be like conventional wheel design.

But energy requirements and size of the flywheel increases the

geometry changes to disc of central hub and peripheral rim connected

by webs and to hollow wheels with multiple arms.

GEOMETRY OF FLYWHEEL

GEOMETRY OF FLYWHEEL• For a solid disc geometry with inside radius ri and out side radius ro, the

mass moment of inertia I is

• The mass of a hollow circular disc of constant thickness t is

• Combing the two equations we can write

• Where is material’s weight density

STRESSES IN FLYWHEEL• Flywheel being a rotating disc, centrifugal stresses acts upon its distributed

mass and attempts to pull it apart. Its effect is similar to those caused by an internally pressurized cylinder.

• = material weight density, ω= angular velocity in rad/sec. ν= Poisson’s ratio, is the radius to a point of interest, ri and ro are inside and outside radii of the solid disc flywheel.

ADVANCE AND MODERN FLYWHEEL

• Advanced flywheels are also now used for protecting against interruptions to the national electricity grid.

– The flywheel provides power during period between the loss of utility supplied power and either the return of utility power or the start of a sufficient back-up power system

• Flywheels have also been proposed as a power booster for electric vehicles. Speeds of 100,000 rpm have been used to achieve very high power densities.

• Modern high energy flywheels use composite rotors made with carbon-fibre materials. The rotors have a very high strength-to-density ratio, and rotate at speeds up to 100,000 rpm. in a vacuum chamber to minimize aerodynamic losses.

BENEFITS IN AEROSPACEFlywheels are preferred over conventional batteries in many aerospace applications because of the following benefits:

• 5 to 10+ times greater specific energy• Lower mass / kW output• Long life. Unaffected by number of charge / discharge cycles• 85-95% round trip efficiency• Fewer regulators / controls needed• Greater peak load capability• Reduced maintenance / life cycle costs

APPLICATIONS

APPLICATIONS

APPLICATIONS

REFERANCES

• http://en.wikipedia.org/wiki/Flywheel

• http://nptel.ac.in/courses/IIT-MADRAS/Machine_Design_II/pdf/3_7.pdf

• Design of machine elements by V. B. BHANDARI