science

Hesselman engine

Hesselman 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 Hesselman engine rather than just read about it. In short: The Hesselman engine is a hybrid between a petrol engine and a diesel engine. It was designed and introduced in 1925 by Swedish engineer Jonas Hesselman.

Key takeaways

Hesselman 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 Hesselman engine to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hesselman engine from memory before moving on to harder problems.

Reference excerpt

The Hesselman engine is a hybrid between a petrol engine and a diesel engine. It was designed and introduced in 1925 by Swedish engineer Jonas Hesselman. In a Hesselman engine, fuel is not injected during the suction stroke along with the air, as would be the case in a conventional Otto cycle engine, but is instead injected during the compression stroke slightly ahead of the spark. Hesselman engines typically have lower efficiencies than diesel engines but can run on the same fuels without needing to sustain high compression ratios, and therefore could be made smaller, lighter and cheaper. Most Hesselman engines were built during the 1930s and 1940s by firms in Sweden and the United States for use in both heavy vehicles and stationary industrial applications.

Operation During the engine's operating cycle, air is first drawn into the cylinder through an intake valve and given a rotary motion as a result of its tangential direction of entry. Air is compressed on the "up" stroke of the piston without stopping its rotary motion. At about 50 degrees before top dead-center, fuel is injected toward the spark plug from the opposite side of the combustion chamber. The rotary movement of the air mixes the air and fuel while carrying the mixture past the spark plug. The spark occurs at about 15 degrees before top dead-center after which the engine completes its power and exhaust strokes and the cycle began again. Timing for the start of fuel injection and spark are fixed. Throttling of the engine is achieved by linked variation of air intake volume and duration of fuel injection. In practice Hesselman engines had efficiencies higher than contemporary carburetor spark ignition engines but lower than diesel engines. The combination of low-ratio, air-only compression and spark plug ignition allowed Hesselman engines to run on fuel oil, kerosene, petrol, coal derived tar-oils or alcohol although most ultimately ran on conventional diesel fuels. It was common to start Hesselman engines using petrol from a small auxiliary tank before switching over to cheaper diesel fuel from the main fuel tank.

History

The Hesselman engine was first described in 1925 by Jonas Hesselman, who was already a leading authority on diesel engine design and had created hundreds of patents. Hesselman engines were built in Sweden by Scania-Vabis, Tidaholms Bruk and Volvo. Some engines were also built in Germany by AEG. In the United States, Hesselman engines were built by the Waukesha Motor Company for both vehicular and industrial applications. Smaller numbers of Hesselman engines were also built by Allis-Chalmers for use in tracked vehicles. Waukesha-Hesselman engines remained in production until 1951. Marketing tactics emphasised the engine's ease of starting and low smoke emissions when compared to contemporary diesel engines, as well as its ability to run on low cost fuels. Hesselman engines were produced in relatively small numbers (around 500 by 1934) but were tried in wide variety of applications that typically used diesel engines. Transport applications included trucks, buses, powerboats and railcars. Stationary Hesselman engines were used to drive pumps, gas compressors and a variety of other industrial machinery.

See also Hulsebos-Hesselman axial oil engines Gasoline direct injection Diesel engine

References

Illustrations

Worked examples

Example 1 — a first encounter with Hesselman engine

Start with the simplest possible case. Write down what Hesselman 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 Hesselman 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 Hesselman 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 Hesselman engine

In research: Hesselman 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 Hesselman 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: Hesselman engine is common in secondary-school and first-year university syllabi. It links to neighbouring topics Internal combustion piston engines, Swedish inventions, so understanding it makes those chapters shorter.
In everyday life: Look for Hesselman 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 Hesselman engine in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hesselman 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 Hesselman engine out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hesselman engine in simple terms?

The Hesselman engine is a hybrid between a petrol engine and a diesel engine. It was designed and introduced in 1925 by Swedish engineer Jonas Hesselman.

Why does Hesselman 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 Hesselman 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 Hesselman engine.