Compressed Air Engine part1


        Hydraulic & Pneumatic defined as a fluid pressure force. It is a science which depends on the properties of incompressible trapped liquid and compressible trapped Gas. They influence fluid by pressing that lead to distribute its pressure inside it by a regular basis. Those result in the transformation of a small force from the surface of a small piston and turn it into greater force on the surface of a large piston, or vice versa.

Features of the hydraulic/pneumatic systems:

  • Convert small force to a larger amount of force, or vice versa.
  • High precision control systems.
  • The Torque and power developed in the hydraulic system is constant.
  • The Security systems and protection in systems are high.
  • Get high power capacity compared with the system’s weight.
  • Hydraulic oil runs on lubrication and greasing machines prevent from erosion and corrosion.

• Pneumatic Air runs on coolant machines increase prevention from high temperature

The working principle of the air compressor

        Is a mechanical device that has a piston and valves, which works on air pressurized inside the collection tank to a certain extent, the mechanism of the air pressurized is by reducing its size. It‘s work is similar to the principle of the pumps in the sense that both of them is able to increase the fluid pressure and transported through the pipeline, but in the compressors the compressed gases decreases in its volume. While in pumps, the liquid material is non-compressible constant on its volume. Resulting from the pressure a force working on transfer of liquid from one place to other, and this is the working principle of fluid pumps.

     Air compressors in vehicles are compressors combustion engine, based on the regular movement of the piston up and down through which air enters and compressed inside the cylinder, and some types depends on membranes to pull and pressurized air, and prevented it from returning back and exit out of the cylinder during the combination process.

      Compressors industry has developed in the present era and today’s gas compressor capable of storing enormous pressure to be ready for industrial use. Air compressor capacity is determined by determining the amount of air that can enter into the tank with the ability to compress it to a certain limit, usually a pressure of 690 kPa at a temperature of 20 degrees Celsius and humidity of 38%, Compressor capacity unit is m3 / h, and is usually name of the compressor include its capacity.

      The number of devices that can be operated using the compressor depends on the volume of gas needed by each device, we cannot run a number of devices together while it need largest gas volume from the compressor capacity, and if we starting a large number of devices beyond the small capacity of the compressor may cause the damage of it.

The use of hydraulic systems and Pneumatic:

Practically hydraulic systems are used in some applications and Pneumatic in other applications for the following considerations:

– If the application requires a medium speed, accuracy and relative pressure control can be used Pneumatic systems.

– If the application requires a medium pressure, and accuracy greater control can be used both Pneumatic systems and hydraulic systems.

– However, if the application requires a lot of pressure, and high precision control should be used hydraulic systems.


A widespread application of pneumatic motors is in hand-held tools, impact wrenches, pulse tools, screwdrivers, nut runners, drills, grinders, sanders and so on. Pneumatic motors are also used stationary in a wide range of industrial applications. Though overall energy efficiency of pneumatics tools is low and they require access to a compressed-air source, there are several advantages over electric tools. They offer greater power density (a smaller pneumatic motor can provide the same amount of power as a larger electric motor), do not require an auxiliary speed controller (adding to its compactness), generate less heat, and can be used in more volatile atmospheres as they do not require electric power  and do not create sparks. They can be loaded to stop with full torque without damages.

Historically, many individuals have tried to apply pneumatic motors to the transportation industry. Guy Negre, CEO and founder of Zero Pollution Motors, has pioneered this field since the late 1980s. Recently Engineair has also developed a rotary motor for use in automobiles. Engineair places the motor immediately beside the wheel of the vehicle and uses no intermediate parts to transmit motion which means almost all of the motor’s energy is used to rotate the wheel.

A pneumatic motor (Air motor) is a type of motor which does mechanical work by expanding compressed air. Pneumatic motors generally convert the compressed air energy to mechanical work through either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor, piston air motor, air turbine or gear type motor.

Pneumatic motors have existed in many forms over the past two centuries, ranging in size from hand-held motors to engines of up to several hundred horsepower. Some types rely on pistons and cylinders; others on slotted rotors with vanes (vane motors) and others use turbines. Many compressed air engines improve their performance by heating the incoming air or the engine itself. Pneumatic motors have found widespread success in the hand-held tool industry, but are also used stationary in a wide range of industrial applications. Continual attempts are being made to expand their use to the transportation industry.


Compressed air engines were used in trams and shunters, and eventually found a successful niche in mining locomotives, although in the end they were replaced by electric trains, underground.  Over the years designs increased in complexity, resulting in a triple expansion engine with air-to-air reheaters between each stage. For more information see Fireless locomotive and Mekarski system.

A compressed air locomotive by H.K. Porter, Inc., in use at the Homestake Mine, South Dakota, between 1928 and 1961


Transport category airplanes, such as commercial airliners, use compressed air starters to start the main engines. The air is supplied by the load compressor of the aircraft’s auxiliary power unit, or by ground equipment.

Water rockets use compressed air to power their water jet and generate thrust, they are used as toys.

Air Hogs, a toy brand, also uses compressed air to power piston engines in toy airplanes (and some other toy vehicles).


There is currently some interest in developing air cars. Several engines have been proposed for these, although none have demonstrated the performance and long life needed for personal transport.

Examples of pneumatic systems and components

  • Air brakes on buses and trucks
  • Air brakes on trains
  • Air compressors
  • Air engines for pneumatically powered vehicles
  • Barostat systems used in Neurogastroenterology and for researching electricity
  • Cable jetting, a way to install cables in ducts
  • Dental drill
  • Compressed-air engine and compressed-air vehicles
  • Gas-operated reloading
  • Holman Projector, a pneumatic anti-aircraft weapon
  • HVAC control systems
  • Inflatable structures
  • Lego pneumatics can be used to build pneumatic models

Gases used in pneumatic systems

            Pneumatic systems in fixed installations, such as factories, use compressed air because a sustainable supply can be made by compressing atmospheric air. The air usually has moisture removed, and a small quantity of oil is added at the compressor to prevent corrosion and lubricate mechanical components.

Factory-plumbed pneumatic-power users need not worry about poisonous leakage, as the gas is usually just air. Smaller or stand-alone systems can use other compressed gases that present an asphyxiation hazard, such as nitrogen—often referred to as OFN (oxygen-free nitrogen) when supplied in cylinders.

Any compressed gas other than air is an asphyxiation hazard—including nitrogen, which makes up 78% of air. Compressed oxygen (approx. 21% of air) would not asphyxiate, but is not used in pneumatically-powered devices because it is a fire hazard, more expensive, and offers no performance advantage over air.

Portable pneumatic tools and small vehicles, such as Robot Wars machines and other hobbyist applications are often powered by compressed carbon dioxide, because containers designed to hold it such as soda stream canisters and fire extinguishers are readily available, and the phase change between liquid and gas makes it possible to obtain a larger volume of compressed gas from a lighter container than compressed air requires. Carbon dioxide is an asphyxiant and can be a freezing hazard if vented improperly.

Advantages of pneumatics

  • Simplicity of design and control—Machines are easily designed using standard cylinders and other components, and operate via simple on-off control.
  • Reliability—Pneumatic systems generally have long operating lives and require little maintenance. Because gas is compressible, equipment is less subject to shock damage. Gas absorbs excessive force, whereas fluid in hydraulics directly transfers force. Compressed gas can be stored, so machines still run for a while if electrical power is lost.
  • Safety—There is a very low chance of fire compared to hydraulic oil. Newer machines are usually overload safe.