Višezonski model izgaranja u hcci-motoru primjenom kemijske kinetike

Kozarac, Darko (2008) Višezonski model izgaranja u hcci-motoru primjenom kemijske kinetike. = Multi Zone Combustion Model of HCCI Engines with use of Chemical Kinetics. Doctoral thesis , Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje, UNSPECIFIED. Mentor: Mahalec, Ivan.

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Abstract (Croatian)

S obzirom na sve veće zahtjeve koji se postavljaju na motore s unutarnjim izgaranjem, posebno u pogledu smanjenja emisija štetnih produkata izgaranja i potrošnje goriva, pored usavršavanja postojećih procesa izgaranja intenzivno se radi na razvoju novih procesa. Jedan od tih procesa je i tzv. izgaranje homogene smjese s kompresijskim paljenjem (HCCI), koji je tema ovoga rada u kome je za njega razvijen višezonski simulacijski model. Model zbog pristupa rješavanja problema spada u tzv. bezdimenzionalne proračune, a prostorna raznolikost koja se javlja u cilindru simulira se većim brojem zona u kojima se izračunavaju različita stanja. Model se temelji na jednadžbama termodinamike i kemijske kinetike pa se stoga može reći da je termokinetički. Pored kemijske kinetike model uključuje međusobnu izmjenu topline između zona u dodiru, te izmjenu topline između rubnih zona i stijenki cilindra. Postavljeni sustav diferencijalnih jednadžbi uključuje sve zone istovremeno, pa se stoga rješavanjem takvog sustava dobiva rješenje koje nije potrebno korigirati. Osim toga simulacijski model uključuje i izmjenu mase između zona, koja se izračunava posebno razvijenim modelom, u bezvremenskom području. Ispitivanje modela pokazalo je da se on može koristiti na više načina. S jedne strane model se može koristiti za izračunavanje općih fizikalnih veličina kao što su promjene tlaka, temperature, brzine oslobađanja topline itd. Pri tome se ove veličine mogu s dosta velikom točnošću izračunati i bez posebnog podešavanja proračunskih konstanti modela, u cijelom području rada HCCI motora. Pored ovih značajki moguće je izračunavati i emisije štetnih produkata izgaranja, a pregledom promjena sastava u pojedinim zonama moguće je analizirati izvore emisija, te moguće načine njihova smanjenja. Iako je točnost izračunavanja emisija i bez posebnog podešavanja proračunskih konstanti bila dosta dobra, pokazalo se da se njihovim podešavanjem ta točnost može još povećati. Daljnjom analizom rezultata pokazano je da bi budući razvoj ovoga modela trebao ići u smjeru povećanja broja zona, uz razvoj modela za izmjenu topline i modeliranje proračunskih konstanti.

Abstract

In view of ever increasing demands imposed on internal combustion engines, particularly regarding the lowering of harmful emissions and fuel consumption, common combustion processes are being improved and new ones are being developed. One of newly developed processes, i.e. the Homogeneous Charge Compression Ignition combustion (HCCI), is the subject of this paper. In order to give a contribution to a further development of the process, a new, multi zone combustion model of the HCCI process has been developed. The model is classified as a so-called zero dimensional model due to its approach to the problem. The in-cylinder diversity is simulated by a larger number of zones in which different conditions are calculated. Since the model is based on thermodynamic and chemical kinetic equations, it can be considered as a thermo-kinetic model. In addition to chemical kinetics, the model also involves the heat transfer between zones in contact, as well as the heat transfer between boundary zones and the cylinder walls. Since the system of differential equations includes all the zones simultaneously, there is no need for the correction of the obtained results. The model also includes the mass transfer between the zones, which is modelled by a timeless model, developed for this particular purpose. The testing of the model has shown that it can be used in different ways. On the one hand, it can be used for the calculation of general physical properties of the cylinder, such as changes in pressure, temperature and the rate of heat release, etc. These properties can be very accurately calculated in the entire operating window of the HCCI engine without a special adjustment of the model constants. On the other hand, the model can calculate harmful emissions of the engine. By examining the changes in mass fractions of species in each zone, the sources of these emissions and the possibilities of emission reductions can be analyzed. Although the calculation accuracy of emissions is rather good even without the adjustment of the model constants, the accuracy of the calculation can be further improved by adjusting them. A further analysis of the results has shown that a future development of this calculation model should include an increased number of zones together with the development of a heat transfer model and the modelling of calculation constants.

Item Type: Thesis (Doctoral thesis)
Uncontrolled Keywords: HCCI; višezonski model; kemijska kinetika
Keywords (Croatian): HCCI; multi zone models; chemical kinetics
Divisions: 400 Department of IC Engines and Mechanical Handling Equipment > 410 Chair of IC Engines and Motor Vehicles
Date Deposited: 22 Sep 2014 18:00
Last Modified: 16 Oct 2015 13:16
URI: http://repozitorij.fsb.hr/id/eprint/434

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