Talk Turbines: Converting Newtons Thrust to Watts

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The discussion centers on converting thrust measured in Newtons to power output in watts for Wren turbines, highlighting the complexities of relating thrust to horsepower. It is noted that while 1 lbf of thrust equals 1 hp at 375 mph, this relationship varies significantly with speed and resistance, leading to different power outputs at different velocities. Participants express skepticism about the direct correlation between horsepower and thrust, suggesting that factors like static thrust and efficiency must be considered. The conversation also touches on the impact of altitude and air resistance on the hp:thrust ratio. Ultimately, the intricacies of calculating power from thrust in turbine engines remain a topic of exploration.
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Jet engines have a thrust horsepower calculation, but I don't think it could be held applicable in this case. The rule is at 375 mph, 1 Lbf of thrust is equal to 1 HP.
 
These Wren turbines are just under three inches in diameter..
very cool stuff..
 
Hey Fred, that works out, because if you say an aircraft is flying at 375 mph and that aircraft requires 1 lbf of thrust to keep it going at that speed, the power (force times distance per unit time) works out to 1 hp. But that's an arbitrary velocity. If the aircraft has more resistance, and can only fly at 100 mph with the same engine, then the equation results in a power output of 0.2667 hp. And if it's zipping along at 1000 mph, the power output becomes 2.667 hp.

So there doesn't seem to be a correlation between hp and thrust. But there should be since the power actually equates to energy in (ie: energy burned in the engine).

I always wondered about this one, how can you equate thrust to hp? Perhaps because it's "static thrust" one must be able to get a "thrust curve" which is analogous to a pressure curve on a centrifugal pump, along with an efficiency.

There has to be more to it than simply thrust at 375 mph equates to a given hp.
 
Q_Goest said:
Hey Fred, that works out, because if you say an aircraft is flying at 375 mph and that aircraft requires 1 lbf of thrust to keep it going at that speed, the power (force times distance per unit time) works out to 1 hp. But that's an arbitrary velocity. If the aircraft has more resistance, and can only fly at 100 mph with the same engine, then the equation results in a power output of 0.2667 hp. And if it's zipping along at 1000 mph, the power output becomes 2.667 hp.

So there doesn't seem to be a correlation between hp and thrust. But there should be since the power actually equates to energy in (ie: energy burned in the engine).

I always wondered about this one, how can you equate thrust to hp? Perhaps because it's "static thrust" one must be able to get a "thrust curve" which is analogous to a pressure curve on a centrifugal pump, along with an efficiency.

There has to be more to it than simply thrust at 375 mph equates to a given hp.

You do bring up good points. Personally I have NEVER expressed a thrust producing engine in terms of horsepower. It is always in thrust. For some (unknown to me) reason there is a small need to express HP in this fashion. The relationship THP = \frac{F_n * MPH}{375} is actually from a Pratt and Whitney reference I have. It is the only reference I have that even states it. What it's method of derivation is I really do not know.
 
Oops my mistake..
please disregard..
 
FredGarvin said:
The relationship THP = \frac{F_n * MPH}{375} is actually from a Pratt and Whitney reference I have. It is the only reference I have that even states it. What it's method of derivation is I really do not know.
As I understand it, hp:thrust ratio depends on not only speed, but also altitude. I assume that it has something to do with factoring in air resistance.
It always bugs me that a full-throttle jet bolted to a test stand produces zero horesepower.
 
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