science

Partially premixed combustion

Partially premixed combustion 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 Partially premixed combustion rather than just read about it. In short: Partially premixed combustion (PPC), also known as PPCI (partially-premixed compression ignition) or GDCI (gasoline direct-injection compression-ignition) is a modern combustion process intended to be used in internal combustion engines of automobiles and other motorized vehicles in the future. Its high specific power, high fuel efficiency and low exhaust pollution have made it a promising technology.

Key takeaways

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

Reference excerpt

Partially premixed combustion (PPC), also known as PPCI (partially-premixed compression ignition) or GDCI (gasoline direct-injection compression-ignition) is a modern combustion process intended to be used in internal combustion engines of automobiles and other motorized vehicles in the future. Its high specific power, high fuel efficiency and low exhaust pollution have made it a promising technology. As a compression-ignition engine, the fuel mixture ignites due to the increase in temperature that occurs with compression rather than a spark from a spark plug. A PPC engine injects and premixes a charge during the compression stroke. This premixed charge is too lean to ignite during the compression stroke – the charge will ignite after the last fuel injection ends near TDC. The fuel efficiency and working principle of a PPC engine resemble those of Diesel engine, but the PPC engine can be run with a variety of fuels. Also, the partially premixed charge burns clean. Challenges with using gasoline in a PPC engine arise due to the low lubricity of gasoline and the low cetane value of gasoline. Use of fuel additives or gasoline-diesel or gasoline-biodiesel blends can mitigate the various problems with gasoline.

See also Reactivity controlled compression ignition Diesel engine

References "Promising Delphi 1st-gen Gasoline Direct Injection Compression Ignition engine meeting ultra fuel efficient program targets". Green Car Congress. BioAge Group. 2014-04-17. Retrieved 2016-02-15. Johansson, Bengt (2010-04-29). "Partially Premixed Combustion, PPC, for high fuel efficiency engine operation" (PDF). Lund University. Archived from the original (PDF) on 2016-12-22. Retrieved 2016-02-15. Johansson, Bengt (2013-06-10). "Partially Premixed Combustion, PPC – Why all diesel engines should be run on gasoline" (PDF). Lund University. Archived from the original (PDF) on 2017-08-30. Retrieved 2016-02-15. Lindberg, Austin (2013-11-18). "Hyundai Developing Gasoline-Burning Compression-Ignition Engine". Car and Driver. Hearst Communications. Archived from the original on 2016-02-17. Retrieved 2016-02-15. Sellnau, Mark; Foster, Matthew; Hoyer, Kevin; Moore, Wayne; Sinnamon, James; Husted, Harry (2014-04-01). "Development of a Gasoline Direct Injection Compression Ignition (GDCI) Engine" (PDF). SAE International Journal of Engines. 7 (2). SAE International: 835–851. doi:10.4271/2014-01-1300. Retrieved 2016-02-15. Sellnau, Mark; Moore, Wayne; Sinnamon, James; Hoyer, Kevin; Foster, Matthew; Husted, Harry (2015-04-14). "GDCI Multi-Cylinder Engine for High Fuel Efficiency and Low Emissions" (PDF). SAE International Journal of Engines. 8 (2). SAE International: 775–790. doi:10.4271/2015-01-0834. Archived from the original (PDF) on 2017-05-17. Retrieved 2016-02-14. Tunér, Martin (2014-02-28). "State of the art of Partially Premixed Combustion (PPC)" (PDF). Lund University. Archived from the original (PDF) on 2016-02-16. Retrieved 2016-02-14. Tunér, Martin (2015-10-22). "Partially Premixed Combustion, PPC, for high efficiency and low emissions" (PDF). Lund University. Archived from the original (PDF) on 2016-01-28. Retrieved 2016-02-14.

Notes

Worked examples

Example 1 — a first encounter with Partially premixed combustion

Start with the simplest possible case. Write down what Partially premixed combustion 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 Partially premixed combustion 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 Partially premixed combustion 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 Partially premixed combustion

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

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

Frequently asked questions

What is Partially premixed combustion in simple terms?

Why does Partially premixed combustion 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 Partially premixed combustion?

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 Partially premixed combustion.