There are two types of engines: internal combustion engines and heat engines. A heat engine converts mechanical energy into thermal energy through the expansion of a working fluid. Both engines are similar in how they operate. Both engines use a heat source to heat water, which turns into steam and drives pistons and a turbine.
External combustion engine
An external combustion engine is a heat engine that runs on fuel. This type of engine is commonly called a Stirling engine. It has been developed for various applications, including solar dish/engine installations, biomass systems, onboard power systems for deep-space missions, and air-independent submarine propulsion systems. However, its current focus is on micro and small-scale CHP.
This heat engine is most commonly used in power plants. They function by combining a working fluid and fuel in an external chamber, which heats and cools the engine. An external combustion engine is an efficient heat engine because the heat produced by fuel combustion is external to the structure. Other examples of external heat engines include steam engines and Stirling engines.
In addition to its heat engine property, the external combustion engine uses air as an oxidizer. However, this heat engine’s efficiency is less than the ideal Carnot cycle efficiency because air is not pre-heated. The differences between the two result from the amount of heat lost in the exhaust gas.
Another type of heat engine is the internal combustion heat engine. These engines use the same principle as the Internal combustion engine, except that their heat source is hotter. This is important for the efficiency of heat engines since heat engines need a very high temperature to work efficiently. An internal combustion engine’s temperature is too high to convert all heat energy into mechanical energy.
A heat engine uses thermal energy to convert it into mechanical work. It shuttles between low and high temperatures using a rotating piston. A typical heat engine is powered by burning fuel, with a piston that expands and contracts to carry energy from the fuel to a spinning wheel.
Carnot cycle
The Carnot cycle of an internal combustion engine is a process that involves a hot, pressurized reservoir being exchanged for a cooler, pressurized one. This process not only transfers heat but also produces work. The Carnot cycle has four phases. The first two are smaller than the others. The last two are equal.
This ideal thermodynamic cycle occurs between two reservoirs at different temperatures: a hot reservoir (TH) and a cold reservoir (TC). On a thermodynamic cycle diagram, the vertical axis represents the system’s temperature, while the horizontal axis represents the system’s entropy. The Carnot cycle can take place in several ways. It can occur from A to B (isothermal expansion), B to C (isentropic compression), or D to A (isentropic reduction).
The Carnot cycle is essential to understanding an internal combustion engine. It’s a basic thermodynamic cycle that forms the basis for understanding engines. A simple p-V diagram illustrates how this process occurs. In the first stage, a yellow gas is contained in a blue cylinder; due to piston movement, the cylinder’s volume and pressure change generating heat and energy.
The second phase of the Carnot cycle relates to the temperature of the gas and the heat it absorbs. For a car to reach its maximum power, the gas must reach the top of the piston and get the maximum pressure. This means that the mixture will have to expand at a high temperature. As it rises, the heat generated by the piston is transferred to the surrounding air, increasing its temperature and internal energy. In the process, entropy remains unchanged.
The Carnot cycle is the most efficient engine of all the processes. Its efficiency is proportional to the energy input. Despite the numerous advantages of the Carnot cycle, it isn’t easy to replicate this efficiency in practice. The best results are achieved when the heat produced is distributed evenly. In the early 19th century, the idea that energy is conserved was put to practical use.
The Carnot cycle is theoretically the most efficient, but it’s impossible to implement in a real-world internal combustion engine. In practice, the Carnot cycle is non-cyclic. A mix of fuel and air enters the system, a flame forms, and combustion products are produced.
The life cycle of a heat engine
The life cycle of an internal combustion engine includes all the processes involved in producing energy from fuel. The combustion process is the fundamental chemical that releases energy from the fuel and air mixture. An internal combustion engine uses a piston to ignite the power within the cylinder, converting this energy into work. The machine works by restoring the energy into mechanical motion, which drives the wheels.
The cost of an internal combustion engine can be calculated with the life cycle cost model (LCC). The life cycle cost model includes all costs of acquiring, operating, and disposing the engine. Alternative propulsion technologies are also included in the comparison, and their life cycle costs are expected to decrease as technology and mass production improve.
The study authors include Wang, Dawei, Zamel, Nada, Jiao, Kui, Zhou, Yibo, Yu, Shuhai, Du, Qing, and Yin, Yan. The study covers all aspects of the life cycle of an internal combustion engine, from raw material to the vehicle.
Throughout the past decade, changes in the passenger transport sector have been occurring. The global push to reduce the environmental burden has prompted a corresponding shift in vehicle propulsion. However, these trends haven’t significantly impacted the economic aspects of vehicle operations. This article compares alternative propulsion’s life cycle costs with conventional drives.
A study conducted by Ricardo Strategic Consulting shows that internal combustion engines produce greenhouse gas emissions. The study also estimates the total cost of ownership for consumers. The authors also looked at the total energy and greenhouse gas emissions of electric vehicles. The researchers used a life cycle analysis model to make this comparison.
Basic principles of a heat engine
A heat engine works by using heat to move energy. It transfers power from gas to its surroundings, which exerts a force on a piston. The process is cyclic and returns the system to its original state. This process is used in all heat engines. It is called the Carnot cycle.
The amount of energy needed for the process depends on the efficiency of the heat engine. An inefficient heat engine rejects heat to a cold reservoir. An efficient heat engine will produce more work than it consumes. The efficiency of a heat engine will depend on how much energy is required to move a heat source.
A heat engine’s efficiency can be measured by the work it performs divided by the energy it consumes. In 1824, Sadi Carnot published a monograph titled “Reflexions on the Motive Power of Fire,” which reasoned the principles of heat engines. Carnot was a follower of René Descartes and derived implications for all machines. One of the most critical implications of his monograph was his assumption that heat cannot be converted to work without changing its surroundings.
Heat engines can be classified into open and closed heat engines. Fast heat engines maintain the working fluid, while available heat engines exchange the working fluid with the environment. The open cycle releases the products of combustion and enthalpy gas. The two different types of heat engines have their advantages and disadvantages. Heat engines can be used to generate energy in large-scale applications. However, their limitations are their large-scale size and thermodynamically limited operation. Further, they require a large amount of space and moving parts, which increases their loading and risk of failure.
The Carnot cycle is an essential reference for heat engine researchers and engineers. Understanding how the Carnot cycle operates can help engineers improve performance. It also allows researchers and engineers to understand their limits and what they can achieve.
