science

Wankel engine

Wankel engine is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Wankel engine rather than just read about it. In short: The Wankel engine (, VAHN-kəl) is a type of internal combustion engine using an eccentric rotary design to convert pressure into rotating motion. The concept was proven by German engineer Felix Wankel, followed by a commercially feasible engine designed by German engineer Hanns-Dieter Paschke.

Key takeaways

Wankel engine belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Wankel engine to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Wankel engine from memory before moving on to harder problems.

Reference excerpt

The Wankel engine (, VAHN-kəl) is a type of internal combustion engine using an eccentric rotary design to convert pressure into rotating motion. The concept was proven by German engineer Felix Wankel, followed by a commercially feasible engine designed by German engineer Hanns-Dieter Paschke. The Wankel engine's rotor is similar in shape to a Reuleaux triangle, with the sides having less curvature. The rotor spins inside a figure-eight-like epitrochoidal housing around a fixed gear. The midpoint of the rotor moves in a circle around the output shaft, rotating the shaft via a cam. In its basic gasoline-fuelled form, the Wankel engine has lower thermal efficiency and higher exhaust emissions relative to the four-stroke reciprocating engine. This thermal inefficiency has restricted the Wankel engine to limited use since its introduction in the 1960s. However, many disadvantages have mainly been overcome over the succeeding decades following the development and production of road-going vehicles. The advantages of compact design, smoothness, lower weight, and fewer parts over reciprocating internal combustion engines make Wankel engines suited for applications such as chainsaws, auxiliary power units (APUs), loitering munitions, aircraft, personal watercraft, snowmobiles, motorcycles, racing cars, and automotive range extenders.

Concept

The Wankel engine is a type of rotary piston engine and exists in two primary forms, the Drehkolbenmotor (DKM, "rotary piston engine"), designed by Felix Wankel, and the Kreiskolbenmotor (KKM, "circuitous piston engine"), designed by Hanns-Dieter Paschke, of which only the latter has left the prototype stage. Thus, all production Wankel engines are of the KKM type.

In a DKM engine, there are two rotors: the inner triangular rotor, and the outer rotor, which has a circular outer shape, and a figure-eight inner shape. The center shaft is stationary, and torque is taken from the outer rotor, which is geared to the inner rotor. In a KKM engine, the outer rotor is part of the stationary housing, and is thus not a moving part. The inner shaft is a moving part with an eccentric lobe for the inner rotor to spin around. The rotor spins around the center of the lobe and around the axis of the eccentric shaft in a hula hoop-like fashion, resulting in the rotor making one complete revolution for every three revolutions of the eccentric shaft. Torque is taken from the eccentric shaft, making it a much simpler design to adapt to conventional powertrains.

… excerpt ends here. Continue reading the full article.

Illustrations

Wankel engine: KKM Wankel combustion cycle. A is the apex of the rotor, and B is the eccentric shaft. The distance between A and B remains constant. Three power pulses are produced for each revolution of the rotor, and one power pulse is produced for each revolution of the output shaft. — KKM Wankel combustion cycle. A is the apex of the rotor, and B is the eccentric shaft. The distance between A and B remains constant. Three power pulses are produced for each revolution of the rotor, and one power pulse is produced for each revolution of the output shaft.

Worked examples

Example 1 — a first encounter with Wankel engine

Start with the simplest possible case. Write down what Wankel engine claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Wankel engine before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Wankel engine ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Wankel engine

In research: Wankel engine appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Wankel engine in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Wankel engine is common in secondary-school and first-year university syllabi. It links to neighbouring topics 20th-century inventions, German inventions, Motorcycle engines, so understanding it makes those chapters shorter.
In everyday life: Look for Wankel engine outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Wankel engine in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Wankel engine means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Wankel engine out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Wankel engine in simple terms?

Why does Wankel engine matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Wankel engine?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Wankel engine.