Reciprocating Engine

A **reciprocating engine**, also often known as a **piston engine**, is typically a heat engine (although there are also pneumatic and hydraulic reciprocating engines) that uses one or more reciprocating pistons to convert pressure into a rotating motion. The most common types of this classification are the **internal combustion engine** and the **steam engine.**

## Description

In just about all types, there may be one or more pistons. Each piston is inside a cylinder, into which a gas is introduced, either already under pressure (e.g. steam engine), or heated inside the cylinder either by ignition of a fuel air mixture (internal combustion engine) or by contact with a hot heat exchanger in the cylinder (Stirling engine). The hot gases expand, pushing the piston to the bottom of the cylinder. This position is also known as the Bottom Dead Center (BDC), or where the piston forms the largest volume in the cylinder. The piston is returned to the cylinder top (Top Dead Centre) (TDC) by a flywheel, the power from other pistons connected to the same shaft or (in a double acting cylinder) by the same process acting on the other side of the piston. This is where the piston forms the smallest volume in the cylinder. In most types the expanded or "exhausted" gases are removed from the cylinder by this stroke. The exception is the Stirling engine, which repeatedly heats and cools the same sealed quantity of gas. The stroke is simply the distance between the TDC and the BDC, or the greatest distance that the piston can travel in one direction.

## Advantages

* Unlike steam turbine no heat exchanger required in reciprocating internal combustion engines, which results in mechanical simplicity and improved power plant efficiency.
* As compared to steam or gas turbines, the average working temperatures of reciprocating internal combustion engines is very low. The reason is that the peak temperature exists for a very less time (in a cycle). This results in the application of high temperatures resulting in high thermal efficiency of reciprocating internal combustion engines.
* In reciprocating internal combustion engines high thermal efficiency can be obtained by the application of moderate maximum working pressure of the fluid. This results in less weight to power ratio in reciprocating internal combustion engines. Hence for the same power reciprocating internal combustion engines have less weight compared a steam power plant.
* It is also possible with reciprocating internal combustion engines to generate very small power output (even a fraction of kilowatt) with reasonable thermal efficiency and cost.

## Disadvantages

* Due to reciprocating parts more vibrations are produced in reciprocating internal combustion engines. This results in decreased lifespan.
* It is also not possible to use variety of fuels with reciprocating internal combustion engines (like coal, wood etc.).
* Fuels used in reciprocating internal combustion engines are relatively more expensive than fuels used in steam or gas power plant.
* Due to reciprocating parts consumption of lubricants is also high in reciprocating internal combustion engines as compared to steam power plant.
* Reciprocating internal combustion engines are only suitable, when we need low power output. for high power output generally steam power plants are used (like generation of electricity etc.).

## Reciprocating Engines in the New World

### Third Civilization Area and Outside the Civilized Areas

Due to the medieval level of technology and the dependence on magic, reciprocating engines are basically unknown. Some methods of transportation and production still rely on animal power and manual labor. Machine technology is more or less at a crawl in terms of advancement. However, nations that have established ties with Japan, have reaped the benefits of reciprocating engine technology, such as Rail Transport and power generators.

### Second Civilization Area and the Gra Valkas Empire

Mechanized nations such as Mu and the Gra Valkas Empire, were able to develop the reciprocating engine and internal combustion engine on their own, without the influence of Japan. For Mu, they had come up with the technology at a much later date than the nations on Earth, since they had not experienced the Renaissance, nor the Industrial Revolutions of the 19th and 20th centuries. For the Gra Valkas Empire, they had already developed these types of engines on their home world of Yugudo before being transferred to the New World. As a result, both nations have access to cars, aircraft, steam engines, locomotives, and other applications. Mu is considered to be 20-30 years behind the Gra Valkas Empire.

### First Civilization Area

Due to their dependence on magic and reverse-engineering the relics of the Ravernal Empire, the Holy Milishial Empire's engineers do not completely grasp the concepts behind the reciprocating engine. Though their technology allows them to create magical engines that can do the same tasks as mechanical ones, they are lacking in power and performance to the original models from the Ravernal Empire. In many cases, they fall short of even their technological counterparts.

### Japan

Hailing from 21st Century Earth, Japan is able to lean on more than a century of research and development on the reciprocating engine. Their internal combustion engines are considered the highest quality in the New World and Japanese automobiles are always hot sellers. Coupling reciprocating engines with computer controls have given them a tremendous boost in efficiency, power and performance.