In physics, mechanical energy is the sum of potential energy and kinetic energy. This energy is associated with the movement and position of an object. The principle of mechanical energy says that in an isolated system where there is only a conservative force, then the magnitude of the mechanical energy is constant.
If an object moves in the opposite direction to the conservative force, then the potential energy increases. It would be the case of a rocket, the conservative force, in this case, it would be the force of gravity. If the velocity of the object changes, then its kinetic energy…
Thermal energy is the form of energy possessed by any body that has a temperature above absolute zero. Macroscopically, thermal energy is an extensive amount and the amount of this energy that a body possesses is proportional to the temperature.
According to the second principle of thermodynamics, it is considered a degraded form of energy because not all thermal energy can be converted into mechanical energy. By contrast, any other form of energy has the potential to become more or less spontaneously thermal energy (such as mechanical energy by friction, electromagnetic energy by absorption…
The first law of thermodynamics, also called by extension, the law of conservation of energy, is a fundamental assumption of the theory of thermodynamics.
The first law of thermodynamics is a formulation of the principle of conservation of energy and states that:
"The internal energy of an isolated thermodynamic system is constant."
A thermodynamic universe, which consists of the system and its environment, is an isolated system. Energy is not created or destroyed, but is transformed from one form to another: energy can be transferred through the exchange of heat (heat…
The Joule effect, also called Joule's law, is the thermal manifestation of electrical resistance. If electricity circulates in an electric conductor, a part of the kinetic energy of the electrons is transformed into heat due to the shock that the electrons experience with the molecules of the conductor through which they circulate, which increases the temperature of the conductor. It is named in honor of the English physicist James Prescott Joule.
Definition of the Joule effect:
The amount of heat energy produced by an electric current is directly proportional to the square of…
In classical thermodynamics, the first field in which entropy was introduced, S is a state function of a system in thermodynamic equilibrium, which, by quantifying the lack of availability of a system to produce work, is introduced together with the second principle of thermodynamics. On the basis of this definition, we can say, in an explanatory but not strict way, that when a system moves from a state of equilibrium it ordered a disordered one to increase its entropy; this fact provides indications about the direction in which a system evolves spontaneously. Entropy and disorder…
Steam engines are mechanical devices capable of transforming heat energy into mechanical energy in a rotating axis. This heat energy takes advantage of the energy contained in water vapor at high pressure and temperature.
We consider steam engines all those machines that transform the thermal energy of a fluid into mechanical energy. In general, the fluid must be pre-heated and at the outlet of the steam machine it must be cooled to repeat the process.
Steam machines can be classified into these two types:
- Plunger steam engine
- Turbine steam engine
The endothermic engine, also known as internal combustion engine. The main characteristic of this type of alternative engines is that through the laws of thermodynamics it is able to take advantage of the energy contained in the fuel to obtain a mechanical work.
The endothermic engine is a type of alternative engine by the way of converting chemical energy into mechanical energy. The most popular endothermic engines are the Otto engine or gasoline engine that operates according to the Otto cycle and the diesel engine, which operates according to the diesel cycle. Meaning of the…
The Stirling engine applications can be divided into three main categories:
- Mechanical propulsion
- Heating and cooling
- Power generation systems
A Stirling engine is a thermal engine that works by cyclic compression and expansion of air or other gas, the working fluid. During the Stirling cycle there is a net conversion of heat to mechanical work. The Stirling cycle engine also operates in reverse, using a mechanical energy input to drive the heat transfer in a reverse direction (ie, a heat pump or refrigerator). Generation of electrical energy…
Chemical thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the limits of the laws of thermodynamics. Chemical thermodynamics involves not only laboratory measurements of various thermodynamic properties, but also the application of mathematical methods to the study of chemical issues and the spontaneity of processes.
The structure of chemical thermodynamics is based on the first two laws of thermodynamics. From the first and second laws of thermodynamics, four equations called "fundamental Gibbs equations"…
Traditionally, when we talk about motors, we usually refer to internal combustion engines or electric motors. However, there are other types of motor. Among these types of motor there are the physical power motors.
The so-called physical power motors are motors that take advantage of the kinetic energy or the potential energy of some element.
An example of power motors is found in hydro power plants. In this type of installation the potential energy of the water is used, which, when it falls, becomes kinetic energy and activates a turbine. In this way, a motor,…
A motor or motor is a machine designed to convert a form of energy into mechanical energy . An engine can be classified into a category according to two criteria: the form of energy it accepts to create movement and the type of movement it produces.
As a general rule, engines have an axle, which in rotary offset and through mechanical devices such as drive gears. The exceptions are rocket motors and linear motors . Nowadays, combustion engines…
The Stirling cycle is a thermodynamic cycle that describes the operation of a class of equipment (generating or operating machines). The cycle describes the original Stirling engine that was invented and patented in 1816 by the Reverend Robert Stirling, helped substantially by his brother engineer.
The Stirling engine is an external combustion engine. This characteristic differentiates it from other types of engines such as the otto engine or the diesel engine which are internal combustion engines. Both engines operate according to the otto cycle and the diesel cycle respectively.…
The Stirling engine is an external combustion thermal engine. Originally it was conceived as an industrial main engine to compete with the steam engine, but in practice, for more than a century it was only used for domestic applications and for low power engines.
The Stirling engine was invented in 1816 by Robert Stirling, a Scottish priest. One of the concerns of the time was the safety of steam engines. Stirling's goal was to get a less dangerous engine than the steam engine.
The operation of the Stirling engine is based on the expansion and contraction of a gas that can be…
The engine is a machine capable of transforming a source of energy, which can be in chemical form (in the presence of a fuel), electrical or thermal, into a mechanical energy or mechanically continuous work, typically used in the field application purposes. with the propulsion of various types of vehicles.
In a philosophical sense, an engine is the organism that causes movement or change in other affiliated institutions: Aristotle spoke of motionless motor, a term also picked up by other philosophers, to indicate the cause of the universe, that is, the object or subject which (according…
An electric generator is a machine that transforms rotational mechanical energy into electrical energy. In this sense, it works in the opposite sense of how an electric motor works.
An electric generator is any device capable of maintaining an electrical potential difference (voltage) between two points, called poles or terminals. Electric generators are electrical machines designed to transform mechanical energy into electrical. This transformation is achieved by the action of a magnetic field on the electric conductors arranged in coils on a sheet metal frame. If a relative movement…
The uses of the steam engine have been changing with the passage of time.
Initially, since the early eighteenth century, steam engines have been used to power a multitude of uses. At first, the steam engine was used as a piston pump. A piston pump is a hydraulic pump that generates movement in it by the movement of a piston.
Subsequently, from the years 1780 began to appear alternative engines. With the alternative motors a new use of the steam engine appears: to give power to the factories and to the industrial one. At the beginning of the 19th century, steam…
Heat engines are a type of alternative engines. Actually, they are the most popular alternative engines.
This type of engine uses the thermal energy caused by the combustion of a fuel (usually gasoil or gasoline) to convert it into mechanical energy. Heat Machines
The concept of a thermal engine is often confused with that of a thermal engine. These terms are related but not exactly the same. A thermal machine is a device or system that works by establishing exchanges of heat and work with its environment. To achieve this, the machine transforms a substance through a cyclic…
A direct current motor (DC motor), or simply a continuous motor or direct current motor, is a rotating electric malternating currenthine that transforms electrical energy in the form of direct current into mechanical energy through electromagnetic interalternating currenttions.
Virtually all electric motors are reversible, that is, they can transform mechanical energy into electrical energy functioning as dynamos. direct current motors base their operation on the Lorentz law, also called Laplalternating currente's law when it is applied to a conductor, as is the case of motors. Applications…
An oil refinery is an industrial plant, of the oil raw material by purification and distillation under normal pressure and under vacuum in fractions with a defined boiling range transferred. The additional refinement of the boiling cuts is done by methods such as extraction or chemical cleaning methods. To increase the quality of products, such as their octane number, conversion processes such as isomerization or catalytic reforming are used. In addition, additives are added to products that improve or suppress certain properties.
Higher value products are obtained, such as gasoline,…
In this website we try to explain the operation of the main types of engines from a theoretical point of view. We present schematically the parts, operating cycles and characteristics of the following types of engines:
- The thermal engine or internal combustion engine. Inside the thermal engines we explain the gasoline engine (or otto engine) and the diesel engine).
- The electric motor. This engine has undergone a great evolution throughout history and right now is one of the most used types of engines and with more projection of the future. We will analyze direct current…
The third law of thermodynamics, also called Nernst's theorem, is a theorem of thermodynamics.
This principle states that the entropy of a system at the absolute zero temperature is a well-defined constant. This is because, at the absolute zero temperature, a system is in a basic state, and entropy increases are achieved by degeneration from this basic state. Formulations of the third principle of thermodynamics
Like the second principle of thermodynamics, to which it is closely linked, this establishes the impossibility of realizing a certain class of phenomena. There…
In some applications, doubts arise as to whether it is better to use an electric motor or to use a thermal motor. One of the important elements in making this decision will be to know the differences in energy efficiency.
Main problems of thermal motors:
- Rising prices of fossil fuels combustibe (oil, coal, etc.)
- Scarce projections of evolution in an immediate future.
- Emission of greenhouse gases.
- Not reversible, when braking, can not generate power.
Main advantages of electric motors:
- You are a clean alternative if we…
The electric motor is an electrotechnical machine that converts electrical energy into mechanical energy. That is, when the electric motor is connected to the proper power source, it begins to rotate, which also begins to rotate the machine or the machine associated with it. That is, it works inversely to the electric generator, which produces electrical energy with mechanical energy.
The electric motor was made possible thanks to the discoveries of Franz Ernst Neumann and James Clerk Maxwell. His discoveries were published in the years 1841 and 1873.
The electric motors can be…
Diesel engines have several advantages over other internal combustion engines: Advantages related to diesel engine fuel
The fuel of a diesel engine has a higher energy density and a smaller volume of fuel is required to perform a specific amount of work.
Diesel engines inject fuel directly into the combustion chamber, have no air intake restrictions other than air filters and intake pipes and have no vacuum in the intake manifold to add parasitic load and pump losses to push the pistons down against the vacuum of the intake system. Cylinder filling is aided by atmospheric…
Altern current motors are electric motors that are powered by alternating current. Electric motors convert electrical energy into mechanical rotation energy through the mutual action of magnetic fields.
There is a wide variety of altern current motors, among which the following basic types stand out:
- The universal motor that can also be direct current.
- The synchronous motor. In this type of electric motor the speed of rotation is constant and depends on the frequency.
- The asynchronous motor. It is a three-phase motor.
In some cases, such as…
In physics, electricity is a generic term that encompasses a whole set of phenomena that are the manifestation of the presence of a movement of electric charges. We can apply the term electricity to phenomena known as lightning or static electricity but also to other such as the electromagnetic field or electromagnetic induction. The word also serves to designate the branch of physics that studies electrical phenomena and their applications.
In the following sections we will study electricity from a physical point of view…
Foucault currents are the currents induced in masses of conducting metal that are immersed in a variable magnetic field or that, in motion, through a constant or variable magnetic field. In any case, it is the variation of the magnetic flux that generates these currents. The phenomenon was discovered by the French physicist Jean Bernard Léon Foucault in 1851.
In high frequency: using cores with magnetic materials that have low electrical conductivity (such as ferrite).
Foucault currents create energy losses through the Joule effect. More specifically, these currents transform…
The pascal (symbol: Pa) is a unit derived from the International System used to measure internal pressure, mechanical stress, Young's modulus and tensile strength. It is defined as one newton per square meter. It is called in honor of the French mathematician Blaise Pascal.
Some common multiples of the pascal are the hectopascal (1 hPa = 100 Pa), which is equivalent to one millibar, the quilopascal (1 kPa = 1000 Pa), the megapascal (1 MPa = 1,000,000 Pa) and the gigapascal (1 GPa = 1,000,000,000 Pa).
The unit of measure called standard atmosphere (atm) is defined as 101,325 Pa…
A steam engine is a device that produces mechanical energy through the use of water vapor. In particular, thermal energy is transformed into mechanical energy by means of steam. Heat is typically produced by burning fossil fuels, particularly coal, but it can also come from wood, hydrocarbons or nuclear reactions. Description of steam engines
An essential part of the system that includes the steam engine is the steam generator, or the boiler. In the boiler water vapor is obtained by the administration of heat to liquid water. The steam is then sent to the engine, which can be…
The Otto engine and the diesel engine are two types of thermal engines. These are two types of endothermic engines that, through thermodynamic reactions, convert the internal energy of the fuel into mechanical work. However, there are certain differences between them.
The most important difference is found in its theoretical cycle. The Otto engine operates according to the Otto cycle by spark ignition while the diesel engine is controlled according to the diesel cycle by compression ignition.
The other important difference is in the ignition of the fuel. In the Otto engine the ignition…
The theoretical Otto cycle is the ideal cycle of the Otto engine. The Otto engine is also known as a spark ignition engine because the ignition of the fuel is done through a spark caused by a spark plug. It is also known as a gasoline engine because of the type of fuel it uses.
One way to study the performance of this engine is by analyzing its theoretical cycle. The theoretical cycle is an approximation to the real cycle with many simplifications. In practice, there are so many variables that affect the performance of the engine that calculating the actual cycle is practically impossible.…
Between the Otto real cycle and the corresponding theoretical Otto there are substantial differences. Some of these differences can be observed when comparing the diagram of the real cycle with the theoretical cycle diagram. The other differences that we are going to analyze refer to the differences between the temperature and pressure values of the two Otto engine cycles. Differences in the form of the diagram
The difference in shape of the diagram between a real Otto cycle and a theoretical Otto cycle consists of a different profile in the expansion and compression curves, in…
The conversion of electrical energy into mechanical energy by means of electro-magnetism was first demonstrated by the British scientist Michael Faraday in 1821. In his pilot he made the end of a free-hanging contact conductor with a pool of mercury in the that a permanent magnet was placed. At the moment when a current flows through the conductor, the driver performs a rotary movement around the magnet. In this way we obtain kinetic energy.
This electric motor is the simplest version of a homopolar motor. An improved form of this is the Barlow wheel. Due to their primitive construction,…