Steam is a substance in the gas phase that is at a temperature lower than the critical point. Due to this characteristic, the vapor can be condensed in a liquid or a solid increasing its pressure without reducing the temperature.
That is, the vapor is a gas that can be condensed at a constant temperature, increasing the pressure. On the other hand, to convert a non-vaporous gas to liquid, it is not enough to increase the pressure, but the temperature must be lowered.
For example, water has a critical temperature of 374 ° C (647 kelvin), which is the highest temperature at…
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 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 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…
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,…
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 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…
Diesel fuel is a mixture of liquid hydrocarbons, obtained by fractional distillation of crude oil and used as fuel for diesel engines, for heating or for the production of electricity.
It is often inappropriately called naphtha, which is distinguished by a process of better refining and for different uses.
Diesel fuel finds its first applications in the mechanical field between 1893 and 1897, when in the workshops MAN (Maschinenfabrik Augsburg Nuremberg) of Augusta, Rudolf Diesel made the first investigations that led to the invention of the diesel engine. Its name derives from…
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…
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…
Cycles theoretical endothermic engines
For theoretical cycles, commonly used approaches aproximacióna by the real conditions are three:
- real cycle
- air cycle
- air-fuel cycle.
A theoretical these cycles are compared in practice the actual cycles, which are obtained experimentally by means of the indicators, for this reason, the actual cycle also indicated cycle is called.
Although the theoretical cycles do not correspond to actual cycles, provide a useful reference for the thermodynamic study of internal combustion engines,…
The development of the Stirling engine started with the aim of being an alternative to the machine of value due to certain advantages that it had with respect to the then popular steam engine.
Over time, certain disadvantages compared to internal combustion engines have left the Stirling engine in the background. Advantages of the Stirling engine compared to internal combustion engines
The main advantages of a Stirling engine compared to an otto engine, a diesel engine or a steam engine are:
- The maintenance facility
- They are quieter engines
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: …
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 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 compression ignition engine is the diesel or diesel cycle engine. This qualification refers to the way fuel combustion starts inside the piston.
In this type of motor, what enters the chamber initially is only air; the diesel is injected more or less near top dead center. The fuel enters the liquid state, but it is dense. The dense fuel must be vaporized, mixed with the air and reach the conditions of pressure and temperature appropriate to ignite. The time that this process takes is the self-ignition delay and limits the speed at which the engine can turn and, therefore, its maximum…
Thermodynamic transformation is a process by which a thermodynamic system passes from a state of thermodynamic equilibrium to another.
A thermodynamic system is in principle in a state of thermodynamic equilibrium when the main variables of the system (ie pressure, volume and temperature) do not experience any additional variation over time.
In the event that two or all of the above variables change (the variation of only one of them is impossible because they are all interconnected by an inverse or direct proportion ratio) we are in the presence of a thermodynamic transformation,…
The current carrying excitation winding in the stator generates a magnetic field, which is amplified by the iron sheet package and grouped into defined poles. The same happens in the winding of the armature coil downstream. Depending on how the poles are established, this magnetic field created by the stator of the universal motor causes the rotor to drag behind or push it in front of it. In this case, the coils must be inverted in each half revolution (for machines with a pair of poles), for which a switch is necessary.
Considering a "single pole" version, both magnetic fields are perpendicular…
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…
Safety in steam engines is an important issue that needs to be studied and prevented due to the characteristics of this type of machine.
The composition of the steam machines formed by boilers and other components under pressure causes fluids with a very high potential energy to be stored. Due to the high pressure and temperature with which you work any steam or explosion leaks can be very harmful for the safety of people.
Throughout the history of steam engines there have been very serious accidents that have involved considerable material damage and even the loss of human lives.…
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.…
A four-stroke engine is a type internal combustion engine, an alternative engine. It can work both in diesel cycle and Otto cycle ( gasoline engine). It is therefore a thermodynamic and combustion motorcycle.
The most important feature is that you need to perform four strokes of the piston or plunger to complete the cycle. During these 4 races the crankshaft makes two full turns. These four times are: admission, compression, combustion or explosion and escape.
In 1861, the German Otto experimented with his first 4-stroke gas engine. Otto had to abandon the project due to technical…