What is the working principle of a hot machine in junior high school physics?

You've got too many questions, so I'll rearrange your questions.

1. The crankshaft moves in a circle, and the piston moves back and forth, that is, in a straight line, and there is a connecting rod between them, and the connecting rod converts the circular motion of the crankshaft into the linear motion of the piston.

2. Regarding the issue of energy, it should be said that the four processes have the transformation of energy, and you are right. The teacher is also good, he only focuses on the transformation of internal energy and mechanical energy, that is, the energy change of the middle two strokes, the second stroke is the compression stroke, the mechanical energy is converted into internal energy, and the third stroke is the main stroke, which realizes the conversion of internal energy into mechanical energy.

3. The stroke at the beginning is the suction stroke, the crankshaft rotates, and the piston is pulled downward by the connecting rod, which is the work done by the piston by an external force, in addition to the power stroke, the other three strokes (including the first stroke suction stroke) need to consume other forms of energy, such as manpower, electricity, etc.

If you still have doubts, I will send you a courseware about heat engines, and you will understand it at a glance.

At the beginning, when it was said that the shaft rotates and the piston goes down during the suction stroke, doesn't that mean that there is something to work on the piston.

- This is: inertia does work, kinetic energy decreases; compressed gas, gas does negative work; You see that there is inertia in the rotation of the game;

After compression to the end, the gas ignites, explodes, and does positive work;

The positive work is much greater than the negative work, so there is a power output.

The heat engine is divided into single-cylinder, double-cylinder and multi-cylinder. When the piston is down, there is something to do work on the piston, but this work is very small, isn't it just to inhale it? The work is done by another cylinder (in the state of work), and if it is a single cylinder, it is based on the inertia of the flywheel.

As for how the piston moves as soon as the shaft rotates, you need to understand the structure of the crankshaft (let's take a look), which, together with the connecting rod, converts the linear reciprocating motion of the piston into the rotary motion of the flywheel.

When starting the machine, there will be a starter motor or a person to do the work (such as the electric start motor of a motorcycle; Or when starting the tractor, the person should shake the starting handle vigorously). After normal operation, it continues to move by the inertia of the rotating parts, so as to complete the suction process.

The Law of Heat Engine. 1) Definitions or Interpretations.

The ratio of the heat released during the combustion of the fuel is called the efficiency of the heat engine, which is also called the effective efficiency of the heat engine. It is usually expressed as a percentage.

2) Description: Any machine that can use the energy released when fuel is burned to do mechanical work is called a heat engine.

The Law of Heat Engine. 1) Definitions or Absolute Interpretations.

The ratio of the heat converted into useful work to the heat of the macrolimb released during fuel combustion is called the efficiency of the heat engine, also known as the effective efficiency of the heat engine. It is usually expressed as a percentage.

2) Explanation Any machine that can use the energy released when fuel is burned to do mechanical work is called a heat engine.

Internal energy is the energy that the object itself has, for example, gasoline combustion and heat release, it will be converted from its internal energy into heat energy, kinetic energy is the energy of the object in motion, such as a car in motion, regardless of uniform or uneven speed. It will have kinetic energy, as long as it is moving.

Mechanical energy is potential energy plus kinetic energy, for example, if an item falls from the air, its kinetic energy will increase due to the downward acceleration of the earth's attraction, and the potential energy will decrease because it is close to the ground, so that his mechanical energy will not change.

Heat refers to the amount of change in the internal energy of an object during heat transfer. There can be no talk of "heat" without heat transfer.

The principle of heat engine is a type of machine power machinery that converts the chemical energy of fuel into internal energy and then into mechanical energy, such as steam engines, steam turbines, gas turbines, internal combustion engines, jet engines, etc. The heat engine usually uses gas as the working fluid (the medium substance for transferring energy is called the working fluid), and uses the gas to expand by heating to do external work. The main thermal energy is thermal silver grinding energy, atomic energy, solar energy and geothermal energy generated by fuel combustion.

Heat engines play an important role in human life. Modern means of transport are powered by it. The application and development of heat engines have promoted the rapid development of society, but also inevitably lost part of the energy and caused a certain degree of pollution to the environment.

A heat engine is a machine that uses internal energy to do work.

The working principle of the heat engine: the internal energy is converted into mechanical energy by doing work (for example: alcohol combustion, chemical energy is converted into internal energy, heat is transferred to water, water boiling pushes the cork out, and part of the internal energy of water vapor is converted into the mechanical energy of the cork. ）。

The four strokes of the heat engine: suction stroke, compression stroke, power stroke, exhaust stroke.

A four-stroke is two turnovers, that is, one work is suction, and one time is to consume 1 cylinder of oil.

History of the development of heat engines:

Frontal steam engine, steam turbine, internal combustion lee digger, jet engine, rocket engine.

r min=40r s, each working cycle turns 2 revolutions, so the diesel engine does work 20 times per second.

2. =W has q=fs mq=(4 10 n*10*1000m) (3kg*.)

3. =w has q=pt q=

1. The flywheel rotates twice and the diesel engine does work once externally (the research textbook can be known about this), so do 1200 times of work per minute, and then find the number of times you do work per second.

2. Use the force multiplied by the distance to find the useful work, and then multiply the calorific value by the fuel consumption to find the total work, and the efficiency can be calculated.

3. The energy of the seventh power j belongs to the total work and the like, and then multiply the engine output power by 60 seconds, that is, the useful work done when the energy of the seventh power j is consumed, and then divide the useful work by the total work.

How many times per second is the work?

Answer: Do work 20 times per second.

The efficiency of the car is (4000 10000) (46000000 3) 100% = 30%.

The efficiency of the engine is: (85000 1s) (12000000 60) = percent.

The working principle of the internal combustion engine – the working principle of the four-stroke gasoline engine.

Explanation: Stroke - the distance that the piston travels from one end of the cylinder to the other.

1. Suction stroke - the piston is driven by the external force of the crankshaft, moves downward, the intake valve opens, and the mixture of inhaled air and gasoline mist can be.

Flammable gases. - There is no energy conversion in this process, and the crankshaft rotates half a turn.

2. Compression stroke - the intake valve is closed, the piston moves upward, the mixture is compressed, the mixture pressure increases, the temperature rises, and the internal energy increases.

Increase - In this process, the external force does the work, converts the mechanical energy into internal energy, and the crankshaft rotates half a turn.

3. Power stroke - when the mixture obtains the maximum internal energy, the spark plug above the cylinder emits a spark, which makes the mixture burn sharply (explode.

The internal energy of the gas in the cylinder increases sharply, and the high-temperature and high-pressure gas pushes the piston to move downward-this process gas does external work.

This process converts the internal energy of the gas into mechanical energy, and the piston drives the crankshaft to rotate half a turn.

4. Exhaust stroke - after the work is completed, the exhaust valve is opened, and the piston moves upwards under the inertia of the crankshaft, and burns the cylinder.

The exhaust gas is discharged from the cylinder - this process has no energy conversion, and the crankshaft rotates half a turn.

Then close the exhaust valve, open the intake valve and repeat the suction stroke ......And so on and so forth......

In the whole four strokes (one working cycle), the crankshaft drives the wheels to rotate twice to complete two energy conversion processes, and gas does one.

You send me the specific picture, and I'll show you. At least one thing you're wrong. You're talking about gasoline, so gasoline engines generally don't come with flywheels.

Instead, ignite the fire with a spark plug. It is gasoline that ignites when it is compressed in the cylinder. Usually the diesel engine is driven by a flywheel to compress the gasoline, and then ignite the diesel.

Gasoline or diesel is burned in the cylinder to generate high-temperature and high-pressure gas, which pushes the piston to do work.

There is a loss of energy!

Proportional! It is the loss that is getting smaller and smaller, which is what has been pursued!