Piston Engine-Based Power Plants

Paul Breeze

• Publisher: Academic Press
• Year: 2017
• Print ISBN: 9780128129043
• eBook ISBN: 9780128129050
• Topic: Physical Sciences
• Subtopic: Energy

Piston Engine-Based Power Plants presents Breeze's most up-to-date discussion and clear and concise analysis of this resource, aimed at those working and researching in the area. Various engine types including Diesel and Stirling are discussed, with consideration of economic factors and important planning considerations, such as the size and speed of the plant. Breeze also evaluates the emissions which piston engines can create and considers ways of planning for and controlling those.- Explores various types of engines used to power automotive power plants such as internal combustion, spark-ignition and dual-fuel- Discusses the engine cycles, size and speed- Evaluates emissions and considers the various economic factors involved

Chapter 1

An Introduction to Piston Engine Power Plants

Abstract

Piston engines are the largest group of thermodynamic heat engines in use across the globe. Sizes vary from a few watts to 80 MW and the engines can burn a wide range of fuels, from coal through liquid fuels to natural gas. Most engines used for power generation are derived from engines developed for transportation applications. The earliest piston engines were steam-driven engines which evolved during the 18th century but modern internal combustion engines are based on developments at the end of the 19th century. The two main types are the spark ignition engine and the compression ignition engine. The average annual capacity of piston engines for power generation installed each year is between 50 MW and 60 MW.

Keywords

Piston engine; reciprocating engine; spark ignition engine; compression ignition engine; diesel; Otto; Stirling engine

Piston engines or reciprocating engines (the two terms are often used interchangeably to describe these engines) are by a wide margin the largest group of thermodynamic heat engines in use around the world. Their applications range from model aeroplanes to lawn mowers: they include all the automotive power plants found in motor cycles, cars, trucks and many other sorts of heavy machinery; they power locomotives, ships and many small aircraft and they provide stationary electrical power and combined heat and power to numerous sites across the globe.

The number in use is enormous; the United States alone produces more than 35 million each year. Engines vary in size from less than 1 kW (model engines can be a few watts) to 80,000 kW. They can be driven using a wide range of fuels including natural gas, biogas, liquefied petroleum gas, gasoline, diesel, bio-diesel, heavy fuel oil and even coal. They are manufactured all over the globe and there is a large global base of expertise in their maintenance and repair. While modern engines are often extremely advanced and digitally controlled, older engines can often be kept in service by small, local workshops.

In line with the wide range of engines available, the power generation applications of piston engines are enormously varied. Small units can be used for standby power or for combined heat and power in homes and offices. Larger standby units are often used in situations where a continuous supply of power is critical such as in hospitals or to support highly sensitive computer installations like an air traffic control system or one of the many computer server farms around the world. Commercial and industrial facilities use medium-sized piston engine-based combined heat and power units for base-load, distributed power generation. Large engines, meanwhile, can be used for base-load, grid-connected power generation while smaller units form one of the main sources of base-load power to isolated communities with no access to an electricity grid.

The piston engines used for power generation are almost exclusively derived from similar engines designed for motive applications. Smaller units are normally based on car or truck engines while the larger engines are based on locomotive or marine engines. Performance of these engines vary. The small engines are usually cheap because they are mass produced but they have relatively low efficiencies and short lives. Larger engines tend to be more expensive but they will operate for much longer. Large, megawatt-scale engines are among the most efficient prime movers available,¹ with simple cycle efficiencies approaching 50%.

The piston engine takes its name for the characteristic feature of the engine design, a piston. This piston moves backwards and forwards (or up and down) within a cylinder, that is sealed at one end, in response to the expansion and contraction of a gas within the sealed chamber as the gas is heated and cooled. The heating and cooling of the gas sealed in the piston cylinder can be carried out by applying alternate heating and cooling externally, in which case the engine is called an external combustion engine. However in most engines of this type the heating takes place via the combustion of a fuel in air inside the cylinder itself. This type of engine is called an internal combustion engine.

There are two principle types of internal combustion reciprocating engines, the spark ignition engine and the compression or diesel engine. The latter was traditionally the most popular for power generation applications because of its higher efficiency. However it also produces high levels of atmospheric pollution, particularly nitrogen oxides. As a consequence spark ignition engines burning natural gas have become increasingly popular units for power generation, at least within industrialised nations. A third type of piston engine, called the Stirling engine, is also being developed for some specialised power generation applications. This engine is novel because it is an external combustion engine.

The enduring popularity of the piston engine derives from it portability and flexibility. With a small reservoir of fuel the engine is self-contained and can produce energy or work for extended periods. This is particularly important for transportation applications such as road vehicles but also makes them useful for the wide range of power generation applications noted above.

The main drawback of these engines is that they generally require the combustion of a fossil fuel to provide the energy needed to drive them. In consequence they represent a major source of atmospheric carbon dioxide emissions across the globe and contribute significantly to the quantity of this gas that is released into the atmosphere each year. In addition both types of internal combustion engine, but particularly diesel engines, are sources of a range of other pollutants. Where these engines are used for stationary applications such as power generation it is feasible to apply advanced techniques to clean the exhaust gases and reduce their atmospheric emissions of carbon dioxide. However this is not cost effective for smaller, mobile-scale applications such as for cars. In consequence there is a major industrial effort taking place to find a cleaner replacement for transportation applications. Candidates include fuel cell-powered vehicles and battery-powered vehicles.

The History of the Piston Engine

The earliest references to the concept of a piston engine can be found in the 17th century when the French inventor Jean de Hautefeuille proposed a device that would use gunpowder as the fuel to drive a piston in a cylinder as a means of generating mechanical energy. This device operated using single charges of gunpowder and would have had to be recharged before each cycle so would have been of limited use as an engine for providing useful work. There is no evidence that Hautefeuille actually built his device but the Netherlands’ scientist Christiaan Huygens may have attempted to do so. Material limitations would, anyway, have made it difficult to develop an engine using this principle at that time. Nevertheless, Hautefeuille’s proposal appears to have been the first mention of both a piston engine and the idea of an internal combustion engine.

While the materials were not available to build successful engines of this type, another proposal from the 17th century did gain traction, an external combustion engine using steam as the working fluid. One of the earliest contributors to this line of development was another French scientist, Denis Papin. He put forward the idea of using steam as a working fluid to generate a pressure or force to drive a piston through one stroke of a cycle, with cooling water used to condense the steam again during the second stroke of the cycle when atmospheric pressure would return the piston to its starting point. Again, Papin does not seem to have developed a practical engine based on this design but another inventor did, Englishman Thomas Newcomen, who in 1712 published his design for an atmospheric engine, so called because one side of the cylinder is open to the atmosphere, for use as a pump. This device is now commonly called the Newcomen engine (Fig. 1.1).

Figure 1.1 The Newcomen engine. Source: Wikipedia.

The Newcomen engine was designed as a pump to remove water from underground mine workings. The device consisted of a large cylinder into which a piston was inserted from above, sealing the cylinder from the top but with the top of the piston open to the atmosphere. The piston was connected via a rod to a beam that operated through a pivot to raise and lower a second rod which drove a pump in the mine, below. The bottom of the cylinder was closed but was connected through a valve to a boiler that produced very low-pressure steam. The boiler for the engine was typically a ‘haystack’ boiler, so called because of its shape, which could produce steam to a maximum of 0.2–0.3 bar above atmospheric pressure. During the first part of the engine cycle this steam was admitted into the cylinder, forcing the piston to rise against the pressure of the atmosphere on the top of the piston. The valve was then closed and a second valve opened briefly, allowing cold water to spray into the cylinder and cool this steam which then condensed, allowing atmospheric pressure to force the piston back down. This cycle was repeated around 12 times each minute.

Operation of the engine required the two valves to be alternately opened and closed, with this cycle of opening and closing repeated at regular intervals. The valves were originally operated manually but a mechanical means of carrying this out was soon devised, an early forerunner of the valve mechanisms in modern engines.

The development of steam piston engines continued through the 18th century and into the 19th century with designers such as James Watt, who developed a more efficient version of the Newcomen engine. All the early steam engines used low-pressure steam but gradually, as material technology improved, higher pressure was introduced.

The use of high-pressure steam allowed smaller engines to be built. Piston steam engine development continued until the late 19th century when the steam turbine first appeared. This was a much more advanced, high-speed engine and it quickly superseded steam reciprocating engines for most applications. However the use of reciprocating engines for steam locomotives on railway systems continued, in some regions, until the end of the 20th century.

While steam, external combustion, reciprocating engines played an important role in the development of piston engines it is the internal combustion engine that has proved to be the most enduring engine of this type. Although the concept was proposed in the 17th century, internal combustion was virtually abandoned when steam engine development began and it was not until the 19th century that practical engines of this type began to reappear.

One of the first was designed by Belgian engineer Jean Joseph Etienne Lenoir. His single cylinder engine was an adapted steam reciprocating engine that was fired with fuel gas that was ignited inside the cylinder using ‘jumping sparks’, an early electrical ignition system. Lenoir’s engine was derived from a double-acting steam engine in which steam is used to drive the piston in both direction...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Chapter 1. An Introduction to Piston Engine Power Plants
• Chapter 2. Fuels and Energy Resources for Reciprocating Engines
• Chapter 3. Types of Reciprocating Engine
• Chapter 4. Spark Ignition Engines
• Chapter 5. Diesel Engines
• Chapter 6. Stirling Engines and Free Piston Engines
• Chapter 7. Piston Engine Cogeneration and Combined Cycles
• Chapter 8. The Environmental Impact of Reciprocating Engine Power Plants
• Chapter 9. The Economics of Piston Engine Power Plants
• Index