Vocabulary Practice

1. What are petrochemical products?

2. Describe the difference between nuclear fission and nuclear fusion.

3. What is a hot-air engine? What else is it called?

4. What is a rotary engine? What is the best known type called?

5. Describe a rotor.

Engines That do not Use Petroleum as Fuel

A word about the energy crisis: the world's supply of petroleum was created millions of years ago and it cannot be replaced or renewed in our time. Estimates vary on how long the supply will last but according to some experts it may not be much more than thirty years at the present rate of consumption. Automobiles, diesels, and jets use enormous amounts of fuel derived from petroleum as do households and power plants that produce electricity. Petroleum is also the basis for petrochemical products including many of today's plastics, fertilizers, and insecticides.

Therefore there is a mounting interest in engines that do not use petroleum as fuel. Some power plants are already converting from oil to coal, but while coal is in much greater supply than petroleum it is another nonrenewable energy source which will eventually be exhausted. Experiments are under way to harness such energy sources as the wind, the tides, and the sun. Nuclear fusion—the release of energy when atoms join together—is being explored as a safer alternative to nuclear fission with its hazardous by­products of radioactive wastes that pose a serious threat to the environment and to human life. The difficulty with fusion is that it requires an enormously high degree of heat to start the reaction; to date it has not been possible to generate that much heat even under laboratory conditions.

There is much interest today in hot-air and rotary engines. The hot-air engine has a long history: a Scotsman, Robert Stirling, built one in 1827 so the hot-air engine is often called the Stirling engine. Then John Ericsson, a Swede who became a citizen of the United States (he is best remembered as the designer of the ironclad ship Monitor during the Civil War), built and marketed thousands of hot-air engines. The Stirling engine has two cylinders, one of which compresses air; when the air is heated it expands and pushes down a piston in the other cylinder. Engineers today are working to improve the basic Stirling engine and this offers a promise of greater fuel efficiency.

A rotary engine should more properly be called a rotating internal combustion engine. Instead of the reciprocating motion of pistons, a rotary motion is produced directly. The best-known rotary engine is the Wankel engine, named for its German inventor, Felix Wankel. The combustion in the Wankel engine turns a rotor that is triangular, though the outer edges are curved outward or convex. It produces almost no vibration because it has fewer parts; for this reason it is cheaper to manufacture but its fuel efficiency is still in question. Automobiles with Wankel engines use gasoline as fuel since that is what is available; if other fuels become com­mercially feasible the Wankel engine may be more economical than it is at present. Other inventors have produced other types of rotating combustion engines which offer interesting possibilities in experimental models.

Discussion

1. Why is there an energy crisis in the world today? Name some of the largest fuel users.

2. Why won't converting to coal solve the basic energy crisis?

3. What other energy sources are experimental?

4. What is the major difficulty in the development of nuclear fusion as an energy source?

5. What kind of engine did Robert Stirling build? When did lie build it?

6. Who was John Ericsson and what was his connection with hot-air engines?

7. What is the principle on which the Stirling engine works?

8. What kind of motion is produced by a rotary engine? How does this differ from the usual type of internal combustion engine?

9. Name the best-known type of rotary engine. How does it work?

10. Describe some advantages of the rotary engine.

11. What would increase the fuel efficiency of the Wankel engine?

12. Are there other rotating combustion engines? Discuss your answer.

Review of Unit Eight

A. Complete the following sentences with the appropriate word or phrase.

1. In a gas turbine engine the combustion drives the blades of a turbine instead of ___________.

2. Some airplanes have engines in which a shaft driven by a turbine turns a ___________.

3. In a ___________ engine gases expelled from the rear of the engine provide forward propulsion.

4. Newton's Third Law of Motion states that for every action there is an ___________ and ___________ reaction.

5. Air is taken in and compressed by a ___________ in a turbojet engine.

6. A ___________ is the type of jet engine in common use for commercial aircraft.

7. A ___________ has lateral intake valves that vibrate.

8. In a ___________ air is forced into the engine under extremely high pressure.

9. Most plastics are ___________ products.

10. Nuclear ___________ refers to splitting the nucleus of an atom; nuclear ___________ indicates that the nuclei of atoms are joining together.

11. The Stirling engine is a ___________ engine.

12. The Wankel engine produces ___________ motion rather than ___________ motion.

UNIT NINE