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…
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 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…
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…
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 operating system of the thermal engines is based on a cycle that is constantly repeated. In the case of internal combustion engines this cycle consists of the fuel input (admission), combustion of the fuel, expansion of the cylinder and expulsion of the gases produced. This cycle generates a mechanical movement, if the cycle repeats we will have a constant mechanical movement.
A thermal engine can work through many different cycles. In this section we will explain the different operating cycles that an internal combustion engine can have, the real cycles and the theoretical cycles.…
In this section we describe the different parts of a thermal engine. Of thermal engines have many types, however we will focus on the diesel engine and the gasoline engine (otto cycle).
Despite being different engines share many parts in common, so the scheme presented will serve to indicate the nomenclature of each element.
The most important elements of internal combustion engines, common to diesel and explosion engines, we classify them in two large groups:
- Fixed elements of a heat engine: block, cylinder head, crankcase.
- Moving parts of a heat engine:…
The theoretical diesel cycle is the theoretical cycle of a diesel engine, also known as a compression ignition engine.
The theoretical cycle of a thermal engine is a theoretical approximation of its operation to calculate its performance.
The cycle of an internal combustion engine is constituted by the physical and chemical transformations suffered by the fuel during its passage inside the engine.
The study of a real cycle taking into account all the numerous variables, represents a very complex problem. For this reason, it is usually simplified by resorting to theoretical…
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,…
The second law of thermodynamics is a principle of classical thermodynamics that establishes the irreversibility of many thermodynamic events, such as the passage of heat from a hot body to a cold one. Unlike other laws of physics such as the law of universal gravitation or Maxwell's equations, the second principle is fundamentally linked to the arrow of time.
The second principle of thermodynamics has several equivalent formulations, one of which is based on the introduction of a state function, entropy: in this case the second principle states that the 'entropy of a system isolated…
The zeroth law of thermodynamics states that "if two bodies A and B are separately in thermal equilibrium with a third body C, then A and B are in thermal equilibrium with each other.
This law allows the definition of a temperature range, such as temperature scales Celsius, Fahrenheit, Kelvin, Réaumur, Rankine, Newton and Leiden. Statement of the zeroth law of thermodynamics
The enunciation of the zeroth law of thermodynamics is defined as: Two systems in thermal equilibrium with a third are in equilibrium with each other.
The zeroth law of thermodynamics…
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 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…
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.…
To compare cycle just discussed, it is necessary to refer some of the factors whose value depends on the shape and surface, such as: the compression ratio, the maximum pressure, the amount of heat supplied and the heat subtracted useful work.
The following figure are plotted the curves of the ideal thermal performance variations by varying the ratio of co
RINTING for three cycles: Otto, Diesel and Sabathé. For Diesel cycles and Sabathé has chosen a constant pressure…
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…
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…
Since the first developments of the alternative engine with the steam engine, its use has been growing exponentially. The appearance of internal combustion thermal engines has helped to accelerate its popularity.
However, the characteristics of the alternative engine entails a series of advantages and disadvantages that we intend to study.
From the first alternative engines such as the steam engine or the stirling engine to the current thermal engines the characteristics of this engine have varied a lot. Although the operating principle for the generation of mechanical energy is…
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…
Second law of thermodynamics
No real or ideal engine can turn all the heat introduced into mechanical work.
Therefore, only a fraction of the heat supplied by the combustion will be converted into work; This fraction represents the thermal performance of the engine. Then we define,
Ideal thermal performance
Relation between the amount of heat transformed into useful work and the amount of heat supplied to the fluid.
As useful work equals the difference between the supplied…
The actual operating conditions of diesel engines differ markedly from those that are represented in the ideal Otto and Diesel cycles. For diesel engines, the combustion process transformational approaches a constant pressure only in case of unusually large motors and slow.
The actual plot shows that, under normal conditions, the combustion takes place, in Diesel engines, according to a process that approximates a transformational combustion and a constant volume at pressures n…
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…
The cylinder of an engine is the enclosure by which a piston moves. The cylinder name comes from its practically cylindrical form.
The materials used to make the cylinders are specific to each type of engine. The way of building and the chosen materials of the cylinder makes vary the performance of the engine. A cylinder made of a gray cast matrix with laminar graphite provides good sliding properties. A motor cylinder made of high quality alloys such as molybdenum, chromium, nickel and manganese, improves hardness and resistance to wear and corrosion.
Engine cylinders are characterized…
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 diesel engine was invented by Rudolf Diesel, in the year 1893. Rudolf Diese was a German engineer, employed by the firm MAN.
Rudolf Diesel studied high thermal efficiency engines, with the use of alternative fuels in internal combustion engines. Diese's goal was to replace the old steam engines that were inefficient, very heavy and expensive. First steps before reaching the diesel engine
In 1806, brothers Claude and Nicéphore Niépce developed the first known internal combustion engine and the first fuel injection system. The two brothers tested systems…
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
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…
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…
What is the indicated diagram?
The indicated diagram is the diagram that represents the real cycle of a heat engine (a diesel engine or an Otto engine).
The actual cycle of a thermal engine reflects the effective operating conditions. These conditions are identified with the diagram of average pressures in the cylinder in correspondence to the different positions of the piston. The pressure shown in a mean pressure diagram is the so-called average pressure indicated. Study of the indicated diagram
The actual cycle of a thermal engine is the one that reflects the effective conditions of its operation. These conditions are identified with the diagram of average pressures in the cylinder in correspondence to the different positions of the piston. The pressure shown in a mean pressure diagram is the so-called average pressure indicated.
The indicated diagram is the graph that represents this cycle. Simplified operation of the indicator
The indicator is a device used to obtain the indicated diagram of a thermal engine cycle.
In the indicator of the indicated diagram,…
Diesel engines are also known as compression ignition engines. The diesel engine is a type of internal combustion engine that uses gas oil as fuel for the diesel thermodynamic cycle.
The actual performance of diesel cylinder thermal engines is between 35% and 40% and is widely used to propel vehicles.
Diesel engines can operate with 4-cycle and 2-cycle cycles. 2-stroke engines do not consume more fuel than engines with 4-stroke cycles, because the cylinder is swept with pure air and not with the fuel mixture. This is the reason why there is no loss of fuel through the exhaust.…
The Otto engine is a type of alternative thermal engine that works through the Otto cycle. It is an alternative engine capable of converting the chemical energy of fuel into mechanical energy through a thermodynamic reaction.
Due to the characteristics of this type of thermal engine it can receive several names.
- Gasoline engine. Due to the fuel used.
- Otto Engine. Because it works through the otto cycle.
- Spark ignition engine. Due to the way to start the ignition of the fuel. The ignition starts through a guspira generated by a spark plug.