Hello every body. Its long time since the last post.
I heard the a F1 engine works with its full power is equal to the power of boeing 747 Engine is that true or not. and if it was true how this could happend while its wery small 4 strok engine. I know its very powerfull engine but to this level !!!!!!!!!!!!!!!!!!!!!!.
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most definately not true. Turbofan engines as used on the 747 are rated in lbs of thrust (a typical 747 puts out about 50,000 at takeoff power settings). It is difficult to make a direct horsepower comparison therefore. But to put things in perspective, in the early 1950's the start of the art commerical transport aircraft were powered by radial piston engines (DC-7, Lockheed Constelaltion) these put out about 4,000 horsepower each. But they were also about 4500 cubic inches in displacement, and turbosupercharged with water injection. These airplanes weighed about 1/8th that of a laden 747 today and flew at less than 1/2 the speed. Roughly one 747 engine would put out about 40,000 hp. A huge difference between a F1 cars 900bhp.
where F is the thrust and V the velocity. The conversion to HP will depend on the units you choose. Use takeoff values for both F and V and you will see however, that the 747 wins by a big margin.
The GE CF6 turbofan engine on the 747 produces about 60,000 lbs thrust and weighs about 10,000 lbs. That equates to about 4 hp/lb from a commercial engine that lasts several thousand hours between rebuilds.
Current F1 engines produce about 900 hp from about 220 lbs. That's a little over 4 lbs/hp. Unfortunately, the F1 engine only lasts about 2 hours between rebuilds.
On a hp/lb basis they appear competitive, but the F1 engine does not have to meet the reliability standards of the CF6.
No comparison. Like comparing a mouse to a whale.
I have had experience in the aviation industry,and one engine I worked on over thirty years ago was the General Electric T-58, which weighed 300+ pounds, put out over 1,200 hp continuous, and generated a flat torque curve of around 1,000 ft/lbs of torque. And that is now very old technology.
BrentK7 wrote:i'm pretty sure that 1 pound of thrust = 1 horse power.
Not even close. The CF6-50 turbofan engine produces about 55,000 lbf of thrust and has a bypass ratio of about 4.5. That means that only about 20% of the air mass passing thru the engine is used for combustion. So in terms of shaft horsepower (the power absorbed by the turbine section in order to spin the fan, compressor section and auxilliaries) the CF6-50 likely produces about 30,000 shp. According to GE, the CF6-50 weighs about 9,000 lbs, so that works out to about 3.3 hp/lb.
BrentK7 wrote:i'm pretty sure that 1 pound of thrust = 1 horse power.
Not even close. The CF6-50 turbofan engine produces about 55,000 lbf of thrust and has a bypass ratio of about 4.5. That means that only about 20% of the air mass passing thru the engine is used for combustion. So in terms of shaft horsepower (the power absorbed by the turbine section in order to spin the fan, compressor section and auxilliaries) the CF6-50 likely produces about 30,000 shp. According to GE, the CF6-50 weighs about 9,000 lbs, so that works out to about 3.3 hp/lb.
Just my SWAG, of course.
I don't think you understand what I am saying. I am saying that 1 hp = 1 lb o thrust. I'm not saying anything about comparing a turbofan to an F1 engine in terms of power.
"I don't think you understand what I am saying. I am saying that 1 hp = 1 lb of thrust."
I understand what you're saying, but what you're saying is only true for certain (unlikely) conditions. A horsepower is a defined unit of work equivalent to:
-745 watts
-2544 Btu/hr
-33,000 ft-lb/min
A lbf of thrust is a measure of force without regard to time.
To compare power outputs, you must also consider the following:
A pound of jet fuel contains about 19,800 Btu/lb LHV. A modern, 1000 lb thrust (approx. 800 hp), high bypass turbofan, will achieve a brake thermal efficiency of about 25%. So it will burn about 411 lbs of fuel per hour.
A good diesel piston engine will achieve a brake thermal efficiency of about 35%. So for 800 hp, it will burn about 294 lbs of fuel per hour.
Converting the horsepower to thrust, in the turbine engine, is dependent upon the efficiency of the airfoils, which can vary widely. So to say that 1 hp=1 lb thrust is likely untrue.
Quoting from "Aircraft Gas Turbine Powerplants" by Jeppesen
'since a jet engine is rated in pounds of thrust, and a conventional reciprocating engine is rated in brake horse power, no direct comparison can be made between the two. It should be noted, however, that the brake horse power of a reciprocating engine is actually converted into thrust by the propeller. This being the case, a true comparison can be made of the two types of engines only by comparing the thrust fro the jet engine with the thrust from the propeller of the reciprocating engine.'
I would also disagree with Jeppesen on this particular issue. In my opinion, the only legitimate comparison is to give the turbine engined vehicle 1 lb. of fuel and measure how far it travels within a given time period, and then give that same 1 lb. of fuel to the same vehicle, but powered by a piston engine, and see how far it travels in the same time period.
In physics terms, this is called work. And the measure of how effectively a combustion engine, whether operated on the Otto (piston engine) or Brayton (turbine engine) cycle, converts chemical energy into useful work is defined by its Brake Thermal Efficiency (BTE). And it's long been known that piston engines, with their higher internal compression/expansion ratios, always achieve higher BTE's than turbine engines. It's simple physics.
Of course, when considering power-to-weight ratios, the turbine engine wins hands down.
riff_raff using your logic the F1 car does not fare very well.
I think in the race the TV telecast mentioned a 3.5kg per lap fuel useage. Given a fastest lap of 1:33 for KR, that would be a fuel flow of around 325 kg/hr driving a car + driver of no more than 600kg.
The B744 has a fuel flow 11,500 kg/hr at around 330,000kg (from four engines) carring 380+ passengers and cargo at 900+km/h. Think the the turbine many win the efficency test there.
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