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HCCI Engine as chemical reactor to produce fuel/chemicals: An exploring study of n-alkanes low-temperature chemistry in an HCCI Engine

Author: Dr. Ahmad Saylam

Document type: Published research article

Journal: Asian Journal of Engineering and Technology Innovation

Publication details: Volume 8, Issue 2, pages 1–12, 2020

Publication date:

Scientific status: Single-zone modelling study and exploratory reactor concept. The reported operating windows and product yields are model-based results that require experimental validation before engineering implementation.

Archival DOI: 10.5281/zenodo.19438638

Abstract

This study explores the formation of useful products from the low- and intermediate-temperature chemistry of methane, ethane, propane, n-butane, n-pentane, n-hexane and n-heptane in a homogeneous charge compression ignition engine using single-zone modelling.

Target products include oxygenated hydrocarbons, hydrogen peroxide, formaldehyde and alkenes. Simulations were performed at a fixed intake temperature of 400 K and intake pressure of 1 bar while varying the compression ratio from 3 to 19, engine speed from 100 to 2000 rpm and equivalence ratio from 0.05 to 1.

The principal formation of target species occurs within portions of the low- and intermediate-temperature regime, beginning near 680 K and extending to approximately 1000 K depending on the n-alkane. Maximum production occurs during the period of highest mixture reactivity near top dead centre and may survive the remainder of the cycle when high-temperature autoignition is avoided.

An engine speed of 400 rpm was identified as favourable for the investigated C1–C7 n-alkanes. A compression ratio near 5 was reported as favourable for conversion of the C4–C7 n-alkanes, whereas higher compression ratios were required for the less reactive C1–C3 alkanes.

The intermediate reactivity of n-butane produced a broader productive equivalence-ratio range, including conditions approaching stoichiometry. The other investigated n-alkanes generally required leaner conditions. Model-defined yields of up to 85% were reported for an n-heptane case, supporting further investigation of an HCCI-based route to reactive-fuel blends or chemical intermediates.

Technical contribution

The study extends the HCCI-reactor concept from the lighter C1–C3 alkanes to a broader C1–C7 n-alkane series. It compares how fuel reactivity influences the compression ratio, engine speed and equivalence-ratio windows associated with partial oxidation and intermediate-species survival.

The work treats the engine cycle as a controllable transient chemical reactor rather than solely as a combustion device. The central design objective is to exploit low- and intermediate-temperature chemistry while preventing complete high-temperature oxidation of the desired intermediates.

Scope and application boundary

The model is a single-zone representation. It does not resolve spatial temperature and concentration gradients, wall heat transfer, crevice volumes, boundary layers, detailed fluid mechanics, non-uniform mixing, cycle-to-cycle variability or product extraction.

The reported operating windows and yields should therefore be treated as modelling evidence and development hypotheses rather than validated reactor performance. Results are dependent on the selected chemical mechanism, thermodynamic assumptions, numerical treatment and definition of conversion and yield.

Experimental development would require controlled engine or compression-reactor testing with time-resolved pressure, temperature and species measurements, together with product quenching and recovery, carbon and hydrogen balance closure, separation assessment, material compatibility, operability and process-safety evaluation.

Industrial usefulness would additionally depend on net energy demand, product concentration and purity, downstream separation, by-product formation, cycle stability, equipment durability and comparison with conventional chemical-production routes.

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Citation

Saylam, A. (2020). HCCI Engine as chemical reactor to produce fuel/chemicals: An exploring study of n-alkanes low-temperature chemistry in an HCCI Engine. Asian Journal of Engineering and Technology Innovation, 8(2), 1–12. Archival DOI: https://doi.org/10.5281/zenodo.19438638