1. It's the order in which the furnaces in a coal power plant are started after maintenance.
   It's a complex formula that enables you to determine whether or not a car engine will misfire.
2. It's the order in which a spark plug ignites each cylinder in an engine block.
   It's the order the wheels on a train start moving.

The firing order of an internal combustion engine gives the correct order each cylinder is sparked to ignite the fuel. It is used to reduce power lost through vibration and other engine shifting.

1. Powering a train with steam
   Powering a submarine with heated air
2. Creating electricity in a coal power plant
   Using diesel to power a car

A diesel engine ignites the fluid inside the engine (the "internal" element of the "internal combustion engine." Coal power plants, trains and submarines are all heating air or water outside of the engine to drive the pistons.

1. To reduce pollution
   To increase thrust
2. To decrease drag
   To increase lift

Afterburners are generally equipped on military aircraft to increase thrust during combat situations, takeoff and supersonic flight. They work by introducing additional fuel into the pipe after the turbines. Afterburners are only meant to be operated for short periods of time because they consume large amounts of fuel.

1. A windmill
   A jet engine
2. An oil jack
   A generator

A jet engine is also known as a gas turbine engine. As gas is burned, it creates an air flow that spins turbines to create thrust.

1. The compressed gas is ignited, pushing the piston downward.
   The piston moves upward and pushes the gas into the exhaust system.
2. The piston moves upward and compacts the gas.
   The piston moves downward and pushes the gas into the exhaust system.

During the power phase in a four-stroke internal combustion engine, the piston moves downward after the gas in the chamber has been ignited. The explosion creates the power that drives the piston through the rest of the cycle.

1. A machine that changes mechanical energy into chemical energy
   A machine that uses fuel to facilitate vibration
2. A machine that changes heat energy into mechanical motion
   A machine that turns a crankshaft

An engine can be defined as a machine that converts energy, such as heat energy, into mechanical motion. The concept of an engine was first proposed in the 17th century.

1. They create more pollution.
   They are extremely complex.
2. They are thermally inefficient.
   They are much heavier than four-stroke engines.

The main disadvantage that two-stroke engines have is that they burn the oil mixed in with their fuel, which increases pollution. On the plus side, they are simpler, lighter and more efficient than four-stroke engines, making them the right choice for tools such as garden equipment.

1. The Stirling engine
   The Naptha engine
2. The Organic Rankine engine
   The high-pressure steam engine

Robert Stirling invented the Stirling engine in 1816. It was an external combustion engine that used air instead of steam to move its pistons. The Stirling engine was safer (although prone to higher failure rates) and more efficient than steam engines of that era.

1. A steamroller
   An airplane
2. A paddle boat
   A passenger van

The first successful rotary engine was designed in 1908, and its use in airplane design was apparent. The design of the rotary engine aids in spinning propeller blades.

1. Steam
   Fire or explosions
2. Electricity
   Turbines

External combustion engines use a working fluid, such as steam, to move the piston. The heat source is outside of the engine (thus, external combustion).

1. Rankine
   Diesel
2. Wankel
   Radial

The center of the Wankel engine (or rotor) rotates around a stationary gear inside the housing. The rotor is continuously moving in the same direction and driving the stationary gear forward. Mazda has made use of the Wankel engine in some of its cars.

1. Jet engine
   Marine engine
2. Rocket engine
   Two-stroke engine

Rocket engines are internal combustion engines that work by expelling a gas that is the result of high-pressure combustion of propellants. The propellants must contain a fuel and the oxidizer (or grain) for that fuel.

1. To power an average car
   To power a dirt bike
2. To power a chainsaw
   To power a lawnmower

Although highly efficient, two-stroke engines burn a lot of oil. In addition to paying for gas, you would need to purchase about a half-gallon of two-stroke oil for every tank of fuel. Because of the oil being burned, they are no friend to the environment. Two-stroke engines HAVE been used to power small cars, however.

1. Richard Trevithick
   Robert Fulton
2. Caleb Willow
   Thomas Newcomen

Robert Fulton, best known for his work on steamboat technology, was fascinated with steam engines and used one to power the first successful submarine, called the Nautilus, in the late 18th century. He went on to develop steam-powered torpedoes for Britain.

1. An automobile
   A train
2. A vacuum
   A boat

The Stanley Motor Carriage Company produced steam vehicles in the early 20th century. It was founded by twins Francis E. and Freelan O. Stanley. Francis died in 1918 in an automobile accident while trying to avoid two farm wagons and the company was then sold.

1. The engine on a miter saw
   The engine on a kitchen blender
2. The engine on a locomotive
   The motor on a computer disk drive

The steam engine operates on combustion using a fuel source located externally from the engine, not electricity. All the others use small electric motors to convert electricity into mechanical power.

1. Solid rocket
   Cold gas thruster
2. Turborocket
   Hybrid rocket

Cold gas thrusters operate like a balloon with the air being released. They provide low performance but these cheap, simple engines can be useful for making minor adjustments to a spacecraft's course.

1. Electro-magnets
   Hybrids
2. Motors
   Pumps

By definition, "engine" and "motor" both are used as machines that power other devices. However, "motor" is generally used when the power comes from electricity instead of combustion.

1. A radial engine
   A rotary engine
2. A chemical rocket engine
   A turbojet

Although all internal combustion engines contain combustion chambers, turbines are unique to the turbojet. Jet engines pass air or water in the opposite direction of the desired motion using Newton's third law of motion ("For every action, there is an equal and opposite reaction").

1. Magnetic
   Piezoelectric
2. HAWT
   Electrostatic

Magnetic motors are used the most. Electrostatic motors operate based on electrical charge attraction and repulsion, and piezoelectric motors are based on the principals of electric charge that accumulate in certain materials and vibration frequencies. HAWT (Horizontal Axis Wind Turbine) is a wind turbine, not an electric motor.

1. The Rankine cycle is used to describe a spark engine, and the Otto cycle is used to describe a fluid that changes phases.
   The Rankine cycle is the ideal for external combustion engines, and the Otto cycle is the ideal for spark-ignition engines.
2. The Rankine cycle is used to describe low mass fluids, and the Otto cycle is used to describe high mass fluids.
   The Rankine cycle is the ideal for spark-ignition engines, and the Otto cycle is the ideal for gas-turbine engines.

The Otto cycle is used to ideally describe a situation where the working gas remains a gas constantly, such as in spark-ignition systems. The Rankine cycle is the ideal in situations where the working fluid changes between gas and liquid states, such as in steam engines.

1. It is heavier than a piston engine.
   It is more expensive to mass produce.
2. It has poor fuel economy.
   It is three times as large as a piston engine with an equal output.

Although running the engine at a constant speed overcomes some of the fuel consumption issues, under normal operating conditions it consumes more fuel than what should be ideal. Linked to its poor fuel economy is also poor emission quality. This type of engine does have a superior power-to-weight ratio than a piston engine, however.

1. To recharge the batteries
   To power low, continuous speeds
2. To aid in fast acceleration
   A and C

The gas engine in a hybrid car not only recharges the batteries but also improves acceleration, kicks in for higher speeds and can propel the vehicle if the electric motor is discharged. The electric motor operates alone during lower speeds and in slow acceleration.

1. Radial engines have a rotating crankshaft; the crankshaft of rotary engines is fixed.
   Radial engines do not overheat as easily as rotary engines.
2. Radial engines were only useful until the 1920s, when drag limited power output.
   The radial engine has the pistons facing the central point; they point outward on a rotary engine.

A rotary engine rotates around a central fixed shaft. It is for this reason Wankel engines are also called rotary engines, even though this term traditionally was applied to engines that spin, or rotate, with an airplane propeller.

1. Turbo-electric
   Biomass-electric
2. Petroleum-electric
   Diesel-electric

Although biomass is used to generate electricity, as of yet there are no biomass-electric hybrids vehicles in mass production. Turbines, petroleum and diesel are all used in currently produced hybrid engine systems.

1. Reciprocating, uniflow, turbine and oscillating
   Reed inlet, rotary inlet, piston-controlled inlet and uniflow-scavenged
2. I, V, W and U engines
   Griffin, Dyer, Velozeta and Beare head

Although different oil delivery systems can cause variation between two-stroke engines, the main differences are based upon the gas inlet systems. Piston-controlled is the standard engine that uses the piston to control the intake.

1. Trains
   Bicycles
2. Commercial airplanes
   Personal watercraft

After several boiler accidents on steamboats, laws were enacted that required an engineer to be present on all steamboats. The naphtha engine, although equally dangerous, was developed so the owners of personal watercraft could get around this law.

1. A mix of water and alcohol
   A mix of oil and gasoline or diesel fuel
2. Avtur
   Coal

Because two-stroke engines are a simpler design, the oil must be mixed in with the fuel to lubricate the parts. The power-to-weight ratio in a two-stroke engine is often much higher, and these engines are usually easier to service. Two-stroke engines tend to be less efficient but lighter.

1. A jet engine
   A six-stroke engine
2. A radial engine
   A Wankel engine

The radial configuration is generally five pistons radiating out from a central point (the crankshaft). When viewed from the front, it resembles a star of sorts, and that is how it got its name.

1. A train steam engine
   A hybrid car
2. A jet airplane
   A modern farm tractor

External combustion engines use heat to power the piston, but the fire does not have direct contact with the piston. Steam engines are one example of this type of engine.

1. To prevent the exhaust from escaping with the propellant
   To direct the propellant into the combustion chamber
2. To direct the spark into the combustion chamber
   To accelerate the gas exhaust

Nozzles on rocket engines allow the hot gasses to escape but accelerate the speed of the exhaust. Half of a rocket's thrust comes from the pressure created by the nozzle.

1. The Oruktor Amphibolos
   The Model A
2. The Steam Velocipede
   The Puffing Devil

The Puffing Devil was invented by Richard Trevithick in 1801. The first one was left unattended and running by its operators, and it self-destructed. By 1803, Trevithick had improved his design, but the London Steam Carriage never became popular.

1. Cylindrical
   A perfect sphere
2. Similar to a Reuleaux triangle
   An ellipsoid

The Reuleaux triangle is based on an equilateral triangle with bulging sides that create a constant curve. The Wankel engine uses sides that are slightly flatter than an official Reuleaux triangle.

1. A weed eater
   An outboard motor
2. High-octane gasoline engine
   Diesel fuel engine

Outboard motors are used for propelling boats through water. They use the water pumped in from the water pump impeller, located beneath the water line, to cool them instead of air.

1. Diesel
   Radial
2. Stirling
   Rocket

All of these except the Stirling are types of internal combustion engines. Stirling engines use a cyclic expansion and compression of gas. Diesel engines do not use spark plugs. Rocket engines are specialized jet engines. Radial engines are used to rotate the propellers in airplanes.