How Is Economical Speed Calculated for Fuel Efficiency?

In summary, the conversation discusses the relationship between resistance force, base power, time, and fuel efficiency for a car. The expression for fuel efficiency is e = vt/(kv3t+Pt) = v/(P+kv3), where e is the maximum and v is the economical speed. The speakers also consider other methods for determining economical speed and conclude that it cannot be determined from the given information. They also mention that fuel efficiency is dependent on the engine and not just the expression for resistance force.
  • #1
A-Kim
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This is my first writing in forum. And I'm not good at English... Please understand my poor writing.

Resistance force : F=kv2 (N)
Base puissance : P (W)
Time : t

Fuel-efficiency : e (m/J)
Economical Speed is fuel-efficient speed for a car. (e is maximum)

Energy for resistance force must be kv3t
Energy for base puissance mush be Pt
Fuel-efficiency e must be vt/(kv3t+Pt) = v/(P+kv3)

Is there something I have to consider more??
Or please suggest some other method to get economical speed.
 
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  • #2
I don't think you can get fuel efficiency from this setting of the problem.
The force from the engine (the one associated with power) should be equal to the resistance force, for motion with constant speed. You don't use energy for both of them so there is no reason to add them in calculating the work done.

Fuel efficiency depends on the details of engine, not just on the expression for resistance force.
 
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1. What is the formula for economical speed?

The formula for economical speed is (2 x P x S)/C, where P is the power required to overcome drag, S is the aircraft's speed, and C is the cost of fuel per unit distance.

2. How is economical speed different from maximum speed?

Economical speed is the speed at which an aircraft can travel while minimizing fuel consumption. Maximum speed, on the other hand, is the fastest speed an aircraft can achieve.

3. What factors affect the economical speed of an aircraft?

The factors that affect economical speed include the aircraft's weight, aerodynamic design, engine efficiency, altitude, and atmospheric conditions.

4. Why is it important to calculate economical speed?

Calculating economical speed allows for efficient use of fuel and helps reduce operating costs for airlines. It also helps in planning flight routes and determining the optimal speed for different phases of a flight.

5. Can the formula for economical speed be applied to all types of aircraft?

The formula for economical speed can be applied to most aircraft, but it may vary slightly depending on the specific design and capabilities of the aircraft. It is important to use accurate data and make adjustments for any unique characteristics of the aircraft being analyzed.

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