Automotive acceleration, power and torque

Relationship between acceleration and power torque

Many people think that acceleration is mainly determined by torque. I always felt that this idea was not correct. For more information, see the vertical dynamics chapter of vehicle dynamics. A little troublesome. The Spring Festival Gala of ccav is boring. I have nothing to worry about.

New Year's weather. For example. Try to explain.

Two people, A and B, each with the same bicycle (the wheels are the same ). In the flat area, when 5 KM/h was moving forward at a constant speed, their respective acceleration began. One lap per second. Use the best effort to crash the car. In the process of rolling around, make sure to use the same maximum effort. In a circle, the Team continues to work even. (People who ride bicycles know that the left and right sides of the foot are divided into half a ring ). This is simplified to a uniform circle that gives the vehicle a great deal of power.

A's maximum strength is 100. B is a GF, the maximum strength of 50 cattle. However, a unfortunately finds a fat girlfriend. B's weight is the same as that of... Assuming the length of the ankle is 0.5 meters, it is directly applied to the drive axle. A gives the vehicle a torque of 100x0.5 = 50 nm. B is 50x0.5 = 25 Nm. We can see that the bicycle engine is human. The camshaft height is the length of the ankle. Ignore transmission and other things.

Who is accelerating? High torque.

After a period of Full acceleration, a far exceeds B. We will also find that A is much more physical than B. Assume that the initial values of AB are the same.

Now I want to transform B's bicycle into a small one. Enables B to drive 2 laps per second at a speed of 5 km/h. Now, AB is working hard to accelerate with the maximum strength. Note: During Full acceleration, A can only ring one second, and B can ring two times in one second. Who is accelerating?

AB acceleration is as fast! And after a while, both A and B are tired. It consumes almost the same amount of physical strength.

Is torque related to acceleration? From this example, not necessarily. Intuitively, acceleration and power increase are related. But after analysis, what is really related to acceleration is the physical strength consumed by a and B During the acceleration period. Rather than the strength of every cycle. If the speed of the bicycle is slow at the start of acceleration, the same strength and length of the ankle are the same for each rickshaw, the fast pedal wheel will have a higher acceleration. We can see that the physical strength consumed per unit of time is actually power. That is to say, power is the most critical factor in the acceleration performance!

Of course, this is a simple conservation of energy. In the final analysis, object acceleration requires energy. The power is not important. The key is that there is not much energy. Therefore, in the same time, no matter how powerful a single force is, as long as more force and more work are done, more energy is used to accelerate. Naturally fast.

Actual vehicles are more complex. At the maximum power, each gear has its own maximum acceleration curve for different running speeds. The concept of reserve power needs to be introduced here. Of course, this is also related to the current speed of the vehicle when we start to accelerate. So in terms of vehicle dynamics, there are several 2D charts discussing the performance of vehicle acceleration (I have not studied it carefully ). A power balance diagram shows the relationship between speed, power, and the maximum acceleration (p94, "automotive system dynamics" Yu Fan, et al., Machinery Industry Press 2005 ). I don't know much about it.

Let's talk about the engine working condition diagram.

The engine condition icon shows the relationship between the speed, power, and torque. First, the power comes from the torque. Because the piston is pushed directly to the torque by an explosion. However, the power is also related to the speed. Torque x speed
=
Power.
The acceleration depends largely on the power. Therefore, to obtain the maximum acceleration, we must first obtain the maximum power. But at ordinary times, no one will be able to drive at maximum power and maximum acceleration. That's a joke. So how to get a good sense of acceleration and control at a speed of 20-80 kilometers and under different gears is related to the three elements in the working condition diagram.
The three elements together constitute the dynamic feeling of the car.

What is the torque.
This problem is explained by bicycles. Your maximum strength is 100. When the bicycle crawls 50 degrees slope, or carries 3 fat men of 200 catties, it cannot be carried again.
Assume that the maximum strength of a Hercules is 1000. Then he can ride three fat men. Or climb a slope of 50 degrees.
The quality of things that can be pulled depends on the torque. However, if Hynix itself is very fat, the car cannot beat it. When there is no belt on the ground, a car of different wheel sizes starts to accelerate at the same speed. If you ring for 10 times, he can only ring for one, you may beat him at acceleration.

When you can trigger a bullet car, the acceleration of the car depends on how much physical strength (that is, power) you consumed per unit time. Of course, two vehicles start to run at the same speed and engine speed (with the same Friction consumption), and the acceleration of vehicles with high torque is high. In this case, a vehicle with a high torque must have a high running power.

The power represents the highest speed. Let's not talk about it. Easy to understand.

As a civil science department, it's still fun.