# Flywheel design. Inertia dyno for 745 KW engine.

• berko1
In summary, the individual is designing a flywheel for a 745 KW engine inertia dyno with a maximum RPM of 530 and a diameter of 1.7 meters. The goal is to determine the mass of the flywheel and after calculations, it is found to be 80 tons. The individual is seeking assistance as the result seems off. The conversation also mentions considering adjusting requirements to meet the desired outcome.
berko1
Hello again,

I am currently designing a flywheel for a 745 KW engine inertia dyno.

Basically my design requirements are so:

Max RPM: 530 RPM (=55.5 rad/s)
Flywheel Diameter: 1.7 meters
Time needed to accelerate: 60 second (to max rpm)

I need help determining the mass of the flywheel.

My calculations and way:

Power=745 KW

ΔE=P*t=745*60=44700 KJ

Inertia for a solid disc (flywheel) = 0.5*m*r^2

Energy in flywheel = 0.5* (0.5*m*r^2)*ω^2

Isolate the mass:

m= (4*Energy) / (r^2* ω^2)= (4*44700) / (0.85^2*55.5^2) = 80 tons.

80 tons seems way off, I've gone over my calcs a few times and haven't found my problem.

I appreciate any assistance!

45MJ is a lot, and 530 RPM is slow.

Cross-check: 1/4*m*v^2 = E where v is the velocity at 1.7m/2 radius:
1/4*80000kg*(1.7m*55.5/s)^2=44.5MJ

Do you want 745kW over one minute, or maybe a lower charging power and 745kW over less than a minute to discharge?

mfb:

Thank you for your reply, i guess that these are the facts and i'll have to face them and consider "bending" some requirements.

## 1. How does flywheel design affect engine performance?

Flywheel design plays a crucial role in engine performance as it helps to store and release energy during the engine's rotational cycles. The design of the flywheel determines the amount of inertia, or resistance to change in motion, that the engine experiences. A well-designed flywheel can help to smooth out fluctuations in engine speed and improve overall performance.

## 2. What factors should be considered when designing a flywheel for a 745 KW engine?

When designing a flywheel for a 745 KW engine, several factors should be taken into consideration. These include the engine's power output, rotational speed, and torque, as well as the material and size of the flywheel. The flywheel must also be designed to handle the specific vibrations and stresses of the engine.

## 3. How does an inertia dyno work and why is it used for testing engines?

An inertia dyno is a type of dyno (short for dynamometer) that measures the torque and rotational speed of an engine. It works by using the principle of inertia, where the flywheel's resistance to change in motion is measured and used to calculate the engine's power output. This type of dyno is often used for testing engines because it can accurately measure power and torque without the need for external sensors or equipment.

## 4. What is the role of inertia in engine performance?

Inertia is a key factor in engine performance as it affects the engine's ability to maintain a steady rotational speed. A flywheel with a higher inertia will have more stored energy, allowing the engine to maintain a consistent speed even when external forces, such as load changes, are applied. A well-designed flywheel can also help to reduce wear and tear on engine components by absorbing vibrations and shocks.

## 5. How can the design of a flywheel impact engine durability?

The design of a flywheel can have a significant impact on engine durability. A poorly designed flywheel can lead to excessive vibrations, which can cause damage to engine components over time. On the other hand, a well-designed flywheel can help to reduce wear and tear on the engine, resulting in improved durability and longevity.

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