How does an automobile engine work?

Have you ever opened your car bonnet and wondered what happened in its engine? You may not be curious and don't want to know it thoroughly. But when buying a new car, you definitely need to know 3.0 V6 or 2.4 G . what does it mean? What is ' dual overhead cams ' or ' tuned port fuel injection '? . In response to the above questions, let's learn about the engines of cars.

Learn the mechanism of operation of automobile engines

The purpose of an automobile engine (often using gasoline or diesel fuel - temporarily called an engine) is to convert the energy generated by the combustion of gasoline and oil into mechanical energy so that your vehicle can move. Because the combustion process takes place inside the cylinder, this engine is called an internal combustion engine.

Maybach engine 57

In fact, there are also types of external combustion engines. For example, the steam engine used on a classic train is an external combustion engine. Fuel such as coal, wood, oil, etc. is used on steam engines to generate heat to boil boiling water into steam and it is this steam that makes movement inside the engine. The efficiency of the internal combustion engine is higher than the external combustion engine (ie the same distance, the internal combustion engine consumes less fuel than the external combustion engine), plus the internal combustion engine is much smaller in size. with equivalent external combustion engine. That's why cars use internal combustion engines.

Principle of operation of 4-stroke engine

Most cars today use combustion engines in reciprocating piston type because of the advantages:

1. High performance (compared to external combustion engine)
2. Moderate use costs (compared to gas turbine engines)
3. Easy refueling to maintain the journey (compared to electric motors)
4. These advantages make the internal combustion engine a technology that is almost unique for over 100 years.

To better understand the principle of operation, let's learn the most basic things about internal combustion engines.

Principle of operation of internal combustion engine

Simulate the firing process of the cannon

First of all, the simplest example of an internal combustion engine is a cannon . The gun is a cylindrical tube that is sealed one end. People put gunpowder into the barrel of the gun then for a bullet (sharp cylindrical shape) to completely block the gunpowder. When shot, people set fire to the fire gun block. The huge amount of instantaneous gas produced greatly increased the pressure in the barrel, sending the bullet out of the barrel. The motor of a car is a mechanical mechanism that takes advantage of that energy and converts it into rotary motion for the engine's crankshaft.

Most cars currently use 4-stroke engines (invented by Nicolaus Otto in 1867). The 4 periods of the internal combustion engine are illustrated in Figure 1. These include:

1. Suction period (charging - open intake valve, closed exhaust valve).
2. Compression period (two valves are closed).
3. States burn (explode - the valves continue to be closed.
4. Discharge period (closed intake valve, open exhaust valve).

We can see details moving up and down in the engine, which is the piston . The piston is connected to the crankshaft by the rod. The whole process of 4 periods can be described as follows:

Figure 1: Principle of operation of 4-stroke engine

Note: A: Loader, stork, spring-spring trigger; B: Cylinder cover; C: Throat aspiration; D: Cylinder lid; E: Body of the cylinder; G: Oil crackers; H: Lubricating oil; I: Camshaft; Exhaust valve, stork, spring-pin spring; K: Spark plugs; L: Drainage; M: Piston; N: Thanh thanh; O: Gaskets; P: Crankshaft.

1. The first starting position of the piston is at the top, at which point the valve (xuppap) loads open and the piston moves downwards so that the amount of air mixture and small gasoline particles (referred to as gas mixture) loaded fill in the cylinder (part 1-yellow).

2. When the piston moves upward to compress the air mass, mix tiny gas particles. Compaction of air will increase the efficiency of air combustion (the 2-purple part).

3. When the piston hits the top (top dead point) of the journey, the electric flame-burning candle burns gasoline mixing in the air. At this moment, the gas burns immediately, causing an explosion in the cylinder to push down the piston (part 3-red).

4. When the piston is at the bottom point (bottom dead point), the valve (xuppap) discharges open and when the piston goes up, it pushes all the gas in the cylinder out through the exhaust pipe (the 4-blue part).

Now, the engine is ready for the next cycle and it continues to load the gas and gas mixture. Note that the movement of the engine is the rotation of the crankshaft, while the piston movement is a translational motion. To convert the reciprocating motion of piston into rotary motion, the crankshaft is required. Let us now look at how the coupling and working coordination of parts in the engine?

The core part of the engine is the cylinder and piston that moves up and down in it. The engine described above is a single cylinder engine. But the majority of today's cars are not only one cylinder, but 4, 6 or 8 cylinders, 12 or 16. For multi-cylinder engines, cylinders are arranged in one of the following ways: into a single row vertical (cylinder aligned), into V-shaped (V-shaped cylinders), two horizontal cylinders arranged (horizontal cylinder top) or star shape (airplane engine) as shown below.

Simulate the operation of 4-cylinder engine, in line


Simulating the operation of a 6-cylinder, V-shaped engine (V6)


Simulate the operation of 4-cylinder, top-notch engines

Each arrangement has its own advantages and disadvantages for smoothness when operating, production costs, structural shapes. The advantages and disadvantages of each type will make them suitable for each type of transport. For example, a V-engine or a vertical row and a few cylinders are often used for cars, 1 vertical and multi-cylinder engines commonly used for ships and star motors are often used on airplanes, .

Common terms used in engines

The first is 'cylinder capacity' . A combustion chamber is the space in which compression and discharge periods occur. When the piston moves up and down, you can see the size of the combustion chamber changes. It may be the largest or smallest volume. The difference between the maximum volume and the smallest volume is called the cylinder capacity and is measured in liters or cc (cubic Centimeter - 1000 cc by 1 liter).

Here are some examples:

1. A chainsaw needs a motor of about 40 cc
2. A motorbike needs about 500 cc or 750 cc
3. A sports car needs a bigger engine, about 5 liters.
4. Most normal cars need engines from 1.5 liters (1500 cc) to 4.0 liters (4000 cc)

If you have a 4-cylinder engine and each cylinder is about half a liter, your engine has a 2.0 liter capacity. If each cylinder is half a liter, but the engine has 6 cylinders arranged in a V shape, your engine is 3.0 liter in size and is often denoted as a 3.0 V6 engine. Usually the cylinder capacity tells you about the engine's capacity. A 0.5 liter cylinder can hold twice as much gas as a 0.25 liter cylinder. So a 2.0-liter engine can only produce half the power of a 4.0-liter engine. The cylinder capacity can be increased by increasing the number of engine cylinders or increasing the combustion chamber volume of each cylinder.

You've probably seen your car engine has a lot of extra systems to make it work. Most auxiliary systems are designed with different technologies. The more modern the subsystem is, the higher the engine's performance and vice versa. Here we look at some of the subsystems installed on modern engines.

Spark plug

Electric candles used to provide a spark to ignite the gas mixture create a fire in the engine. Electric candles need to ignite at the right time so that the efficiency of the explosion is highest. (See the automotive ignition system article).

Sudan (exhaust valve, suction)

Simulate the operation of the air distribution mechanism

The suction and discharge plugs need to be opened at the right time so that the maximum amount of air is loaded into the cylinder and the exhaust air in the cylinder is discharged to the discharge road. Note that the charging and discharging coins are closed in compression and explosion periods so that the combustion chamber is sealed.

Piston

Piston has a cylindrical form made of metal and moves up and down in the cylinder.

Cement

The shovel is responsible for sealing the gap between piston and cylinder. Cement meets two purposes:

1. Resistance to air leakage during compression and explosive processes (this type of cylinder is also called a pneumatic cylinder).
2. Prevent lubrication oil from getting into the combustion chamber because if oil enters the combustion chamber, it will be burned and therefore the consumption of lubricating oil will be very large while reducing combustion efficiency (this type is called a cement ring). oil).
3. For most old cars, lubricant consumption increases because the oil tank is worn out so the lubricant gets into the combustion chamber and burns in harmony with the air.

Transmission bar (hand)

The connecting rod is used to connect the piston to the crankshaft of the engine. They move while rotating and translating to convert the translational motion of the piston into the rotation of the crankshaft

Crankshaft (mechanical shaft)

Mechanical shaft

The crankshaft is used to transform the reciprocating motion of the piston into a rotary motion like the shaft in the screw - screw set.

Crankshaft box (te)

Crankshaft box surrounds crankshaft and is used for lubricating oil.

Gas distribution system (charging and discharging system)

Gas distribution systems include pennies and a mechanical system that controls them opening and closing at the right time. Closed and open system is called camshaft. The camshaft has orange lugs that push the pannies up and down.

Details (camshaft, nozzle .) in the air distribution mechanism

Most modern engines use camshafts placed on the lid, ie the camshafts are placed on the pins, as you can see in Figure 5. The cams on the camshafts directly impact on the coins - Wax or through a short link. Classic engines use a camshaft that sits underneath near the crankshaft. The connecting rods (also known as the push-up chopsticks) will transmit the lifting force of the orange tab to the puffs through the levers (also known as the 'trigger').

Camshafts, pennies, springs, squads .

The driving of the camshaft rotates thanks to the belt, the chain or the transmission gear of the crankshaft coming in so that the opening and closing of the coin is in sync with the piston movement. For four-stroke engines, when the crankshaft rotates for two rounds, the camshaft will rotate one round.

Drive chain camshaft and orange gear

Most high-performance engines now use 4-pints per cylinder (two recharges, two discharges) and therefore need two camshafts for one cylinder. This leads to the term 'dual overhead cams (DOHC) ' ie two camshafts placed on the cylinder cover.

Ignition system

The ignition system works to produce high-voltage power and lead to electric candles that produce sparks that burn fuel. You can easily find out the ignition system thanks to the power distributor (power split). The power divider has a high-voltage line connected to the center (also called the main high-voltage wire) and has 4, 6 or 8 high-voltage wires connected to the spark plugs (called the high-voltage wire, the number of high-voltage high-voltage wires belongs to the number of engine cylinders). The power divider will distribute each cylinder to receive a high-voltage power source once in a cycle at the right time of the compression period so that the combustion process is perfect, the engine will operate most efficiently and smoothly.

Cooling system

Car cooling system includes radiator (cooling water tank) and water pump with conduits and temperature sensors. Water is circulated in the engine and goes out to the cooler for cooling. Some cars, including the Volswagen Beetles and motorbikes or lawn mowers, are air-cooled (these engines are easily recognizable by the fins outside each cylinder). The air radiator has the advantage that the weight of the engine is lighter but the level of heat dissipation is less than water-cooled, so the engine temperature is hotter, the efficiency and life span decrease.

Loading system and system start up

Most cars use a normal intake system (ie naturally aspirate due to the difference in pressure between the outside air pressure and the vacuum in the cylinder). For modern cars, to increase engine efficiency one uses a Turbocharged or Supercharged air intake system to increase the amount of air intake to the engine while increasing the level of air and fuel mixing to help compress the pressure. increased, more perfect combustion and higher performance. The Turbocharged set uses a small turbine thanks to the energy of the exhaust gas stream to spin the compressor and the Supercharged unit directly uses the engine's power source to spin the compressor.

Turbine wing details in Turbocharged turbocharger

The starter system consists of an electric motor and a magnetic starter coil. When you turn on the ignition key, the electric motor rotates the crankshaft of the motor several times to create compression and explosion. The starter motor must win the following resistance:

1. Complete friction of the engine
2. Compression force of engine cylinder (for certain cylinders in compression)
3. The energy section lets the camshaft close and open the coin
4. All other subsystems such as cooling water pumps, oil pumps, generators, .

Because the car's battery power is only 12 V, in which the power of the electric motor must be very large to overcome the above resistance, the current used for electric motor is quite high. In order to increase the durability of the start-up system, it is necessary to reduce the load for the electric lock by using the starting from the electric current on and off to the electric motor. So when you turn on the ignition key to the engine, you have powered the starter from work to turn on the power on the starter.

Lubrication systems

Body cylinder

The lubrication system has the effect of bringing lubricating oil to the surfaces of motor movement details so that they move more easily. There are two main components for lubrication: the piston and the ball bearings or the crankshaft or silver and the camshaft of the engine. For most engines, lubricating oil is sucked from the oil reservoir and then through the filter and compressed under high pressure to the silvery and cylinder surfaces. Then this oil flows back to the bottom of the te to continue a new cycle.

Fuel system

The fuel system pumps fuel from the tank and mixes them with air to facilitate the best combustion in the cylinder. Fuel system is divided into 3 categories: Carburetor, indirect fuel injection and direct fuel injection.

The carburetor system works to mix air with fuel as soon as the air is sucked into the cylinder.

In gasoline injection engine, the most suitable fuel is directly sprayed into direct fuel injection or port fuel injection.

Exhaust system

Exhaust system includes exhaust pipe and muffler. If there is no silencer, you will hear the sound of thousands of explosions escaping from the exhaust pipe. The muffler will reduce the engine sound volume. The exhaust system also has a catalytic filter to remove harmful substances from the exhaust gas before discharging them into the environment.

Waste control system

Waste control systems in modern cars include a catalytic filter , a sensor system and actuators , a computer to monitor and regulate the operation of parts. For example, catalytic filters use catalysts and oxygen to burn off all the fuel and other chemicals left on the exhaust pipe. An oxygen sensor placed in the flow of exhaust gas will inform the computer to adjust the amount of oxygen appropriately.

Power system

Electrical system includes power source (battery) and generator . Generator is driven by belt and generates electricity to charge the battery. The 12-volt power supply of the battery will supply the entire electrical system such as ignition system, radio, headlights, electric glass washers, electric closing systems, etc. thanks to the wiring of the car.

Modern technologies in automotive engines today

Pressure boosting technology

We often hear the term turbocharger or twin turbocharger , so what is the turbocharging technology in the engine? The engine needs 3 things to operate: fuel, air and ignition. Compressing more air into the cylinder will create more power for the engine, this process often uses a component or a turbocharger or supercharger. The task of these parts is to compress air into the combustion chamber at high pressure to create a higher compression ratio. Almost like overclocking on computers, turbocharging in the engine helps cars achieve greater power.

Camshaft placed above

DOHC (double cam system) refers to the cam number on each cylinder in the engine. The camshaft is responsible for controlling fuel flow and air entering the combustion chamber. The overhead camshaft allows for more intake and exhaust valves on the engine, meaning more fuel and more air is allowed into the combustion chamber. Besides, air discharge achieves high efficiency, adding engine power.

Control the time of valve opening and closing

The computer will calculate when it is necessary to add air and fuel in order to speed up or reduce the amount of charge when the engine operates at a lower speed. Toyota calls this technology VVT-I (variable valve timing with intelligence), Honda is VTEC and BMW has Valvetronic technology .

Computer control motor

Cars today often have a control unit of their operations with a unit called ECU (Engine Control Unit). This unit strictly controls the ignition time of spark plugs, gas volume and fuel load .

Besides, there is another computer controlling electrical system, airbag, temperature, anti-lock braking system (ABS).

New generation diesel engine

Modern diesel engines are stronger, cleaner and more fuel efficient than before. These machines use less sulfur diesel, reducing toxic substances in emissions. The diesel engines of Volkswagen, Mercedes, BMW . all use turbochargers or direct fuel injection to achieve high efficiency. This is also a factor to consider when customers choose to buy a car.

Hybrid motor (Hybrid)

Rising fuel prices and great environmental concerns lead to changes that are most notably hybrid. The engine combines a modern electric motor and a traditional internal combustion engine that aims to reduce fuel consumption and release less harmful substances.Toyota Prius is the most sold hybrid car in the US. 1.8L internal combustion engine comes with an electric motor that produces 134 horsepower. At low speeds, the electric motor will operate and the vehicle will not use any fuel at all. When running at high speed will be a combination of tradition and modernity. Fuel consumption is about 4.7 liters / 100 km for mixed roads.