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What is the difference between shaft power and brake power?

The short answer is these terms are defined by standards organizations based on specific test methods. These methods specify the engine condition, environmental factors, fuel chemistry, inlet and ...
Phil Sweet's user avatar
  • 4,765
6 votes
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Why don't propeller designers use multiple profiles?

There are propellers with different aerofoil sections. For example, the propeller attached to the Rolls Royce engine kept in my graduate college had symmetric aerofoil sections roughly about 25 % and ...
mustang's user avatar
  • 486
5 votes
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Why do trains use the same wheels for staying on track and propulsion?

Trains do sometimes use different means for propulsion: Rack railways use cogs, and Funiculars use ropes I think the reason these are uncommon is that the available traction of smooth tracks is more ...
Alex I's user avatar
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5 votes
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Will this water jet propulsion system design produce any forward thrust?

No, it would just create a torque couple and rotate the boat anticlockwise. Let's say the small propeller has an output volume, q grams/s, and the distance between inlet pipe and outlet is 5cm. The ...
kamran's user avatar
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4 votes
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Propane rocket nozzle material

The answer is that in order to survive and function, the rocket nozzles need to be cooled. How that's done varies with the application, but includes: Liquid Cooling Jacket: The liquid propergols and/...
DLS3141's user avatar
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3 votes

Multiple vs single rocket engine nozzles

In strictly practical terms, the quickest solution is to derive a good design for the small engine and then simply add more of them. Scaling up a rocket nozzle is a difficult process (lots of ...
niels nielsen's user avatar
3 votes

Why is high stagnation pressure important for propulsion?

The amount of useful work you can extract out of gas in an engine is proportional to its stagnation pressure. Energy and be stored as thermal, kinetic, or as pressure. The stagnation pressure is the ...
Rick's user avatar
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3 votes

What is the difference between shaft power and brake power?

You mean BRAKE horsepower. It is the same as shaft horsepower. It is called brake horsepower (abbreviated BHP) because it is measured at the output shaft of the engine while it is running on a test ...
niels nielsen's user avatar
3 votes

How to calculate the moment of inertia of a propeller

Assuming you already know basic moment of inertia calculations (and if you do not then you really should not be asking your question here prior to research): You can't develop an equation without ...
DKNguyen's user avatar
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3 votes
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How to calculate the moment of inertia of a propeller

In order to calculate the mass moment of inertia accurately your best bet is using the functions of a CAD system (solidworks, inventor, onshape etc). If all you want is an an approximation and you can ...
NMech's user avatar
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2 votes
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Compressing the air thrusted by an aircraft's propeller through a cone like tube

It would be slower. Compressing the air takes energy - that will slow the propeller, and the plane as a whole. Imagine a water pump, which is pumping water out of a pipe. Now, if you put your finger ...
Jonathan R Swift's user avatar
2 votes
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Heating the air inside a turbojet instead of combusting it

As a reference, consider the Meredith effect, which applies (applied) in the construction of the P-51 Mustang radiator. From the linked Wiki site: The Meredith effect occurs when air flowing ...
fred_dot_u's user avatar
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2 votes
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RC drone rotor air access

In the 50's the DARPA designed such a craft but due to aerodynamic instability it was a complete failure and abandoned. The problem you have is maintaining 4 separate intakes which have a greater ...
Rhodie's user avatar
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2 votes
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Amount of thrust needed to Hover on the moon?

Look up the surface gravity of the moon. It'll be in units of meters per second squared. Look at the definition of the Newton. Use those two things to determine the thrust needed to keep 1kg of mass ...
TimWescott's user avatar
  • 2,682
2 votes

Time-rate of change of P and T in a pressurized rigid volume with a hole in it

Thanks for a nicely presented first question. First you need a model for the equation of state for the tank. Given the initial conditions, develop formulas that yield static pressure, temperature, ...
Phil Sweet's user avatar
  • 4,765
2 votes

Propane rocket nozzle material

To answer the other part of your question, the temperature is that in the chamber, but note that that figure assumes perfect combustion, which may not be the optimum point for specific impulse in your ...
Dan Mills's user avatar
  • 251
2 votes

Benefits of twin-in/single-out propulsion

Four into two arrangement can help with mid speed fuel economy, but that often isn't enough by itself to justify the complexity. Sometimes, the the general arrangement of things is better. The two ...
Phil Sweet's user avatar
  • 4,765
2 votes
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Would a conical-shaped solenoid be propelled by its interaction with the Earth's magnetic field?

I think you'll be very disappointed. Figure 1. Image source: Science Class. Your coil will form a very weak magnet since it has an air core. (A good solenoid will use an iron core as it has a ...
Transistor's user avatar
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1 vote

How does Kia charge the high-voltage battery in EV mode?

Yes but it's not likely to be fully representative. If I were doing it, ? would be an integrated charging circuit around the 12V that includes the HSG and the inverter converter since it also charges ...
Abel's user avatar
  • 1,352
1 vote
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Sizing electric motor

At 1.6[m/s] the Air resistance is negligible so I would dismiss that term. However, a word of caution: Rolling resistance Force is not the same as friction force if you are using wheels. I would point ...
NMech's user avatar
  • 24.4k
1 vote

Will this water jet propulsion system design produce any forward thrust?

The water starts out stationary. It ends up being jetted out the stern. Yep, that makes thrust. There will be some pressure interaction over the entire hull of the ship. That is geometry dependent. It ...
Phil Sweet's user avatar
  • 4,765
1 vote
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Why there are no jets (missile or aircraft) faster than Mach 3.3?

At those speeds, several effects become important. We consider air-breathing engines in what follows. First of all, aerodynamic heating of the airframe becomes important. In broad terms, to prevent ...
niels nielsen's user avatar
1 vote

Is there an ideal propeller shape?

Propeller Diameter It is observed that the speed of the shaft and the propeller diameter are very closely related. A low shaft speed (given diameter) is very beneficial from efficiency point of view....
Labhesh Thakur's user avatar
1 vote

Thrust distribution of engine

In your force/momentum balance equations you always can include the pressure of the gas. The only time you can ignore it, is if the difference in $PA$ is small compared to other forces. For example ...
Rick's user avatar
  • 1,335
1 vote

Heating the air inside a turbojet instead of combusting it

the amount of energy per second you would have to dump into the air passing through the "heating chamber" in order to make the turboprop engine work would have to be at least as great as that produced ...
niels nielsen's user avatar
1 vote

Compressing the air thrusted by an aircraft's propeller through a cone like tube

This is done in a jet engine, and partly, by the cowl around the front fan on a jet airliner engine, but on a large propeller, you could only do it slightly without slowing the airflow through the ...
Peter R. McMahon's user avatar
1 vote

Is it possible to extract mechanical energy using Turbines behind PulseJet engine?

Two challenges (not necessarily "problems" so long as the device is designed to deal with them) are: Vibration. If the pulse frequency matches a resonant frequency of the turbine, the vibrations may ...
alephzero's user avatar
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1 vote

What is the fraction of power transmitted to the generator in full-hybrid cars?

It will vary between 0 and maximum depending on the demands of the drive system - ie the engine output is shared whatever the wheels need and the remainder to the generator to charge the batteries.
Solar Mike's user avatar
  • 15.9k
1 vote

Increase thrust of ion thruster?

Only by increasing the area of the emitter. For a given species, you can't increase the density of the mass flow beyond a certain limit. And that limit decreases if you lower the emitting velocity. ...
Phil Sweet's user avatar
  • 4,765

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