Validacija modela predviđanja detonantnog izgaranja uz povišene udjele povratnih ispušnih plinova (EGR)

Stipić, Marija (2018) Validacija modela predviđanja detonantnog izgaranja uz povišene udjele povratnih ispušnih plinova (EGR). = Validation of model for predicting knock in cases with increased levels of exhaust gas recirculation (EGR). Undergraduate thesis , Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje, UNSPECIFIED. Mentor: Kozarac, Darko.

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Abstract (Croatian)

Detonantno izgaranje predstavlja jedan od temeljnih problema Ottovog motora jer njegova pojava postavlja granicu povećanju termičkog stupnja djelovanja. Detonantno izgaranje je nekontrolirano izgaranje koje može uzrokovati značajna mehanička oštećenja vitalnih dijelova motora, a ovisi o mnogobrojnim parametrima poput opterećenja motora, brzine vrtnje, sastava smjese goriva i zraka, temperature i tlaka svježe smjese na usisu i dr. Zbog svog značaja za rad Ottovog motora, opisivanje i predviđanje pojave detonacije predstavlja veliki izazov za razvojne inženjere. Budući da eksperimentalna istraživanja zahtijevaju primjenu izrazito skupe opreme i velik utrošak vremena unazad nekoliko godina razvijani su računali alati za analizu procesa izgaranja koji znatno ubrzavaju proces razvoja motora. Na Katedri za motore i vozila razvijen je novi model detonantnog izgaranja koji uključuje proračun temperaturne nehomogenosti neizgorjele zone te proračun detaljne kemijske kinetike samozapaljenja primijenjenog goriva. Model je validiran pri standardnom radu Ottova motora, međutim, nije validiran i pri radu motora s povišenim udjelima ispušnih plinova koji su iz ispušne grane vraćeni ponovno u usis putem sustava za povrat ispušnih plinova (EGR). Kako je EGR sustav postao neizostavna komponenta vozila zajedno s drugim tehnologijama za pročišćavanje ispušnih plinova, potrebno je validirati model i u tom režimu rada motora. U tu svrhu na eksperimentalnom motoru u Laboratoriju za motore i vozila izmjereno je 11 radnih točaka koje se prvenstveno razlikuju po masenom udjelu EGR-a i intenzitetu detonacije. U eksperimentalnoj analizi kao mjera intenziteta detonantnog izgaranja koristio se indikator MAPO. Validacija modela provedena je uspoređivanjem vrijednosti indikatora MAPO iz eksperimenta i vrijednosti intenziteta detonantnog izgaranja dobivenog simulacijom. Analizom rezultata utvrđeno je da novi model dobro predviđa pojavu detonantnog izgaranja pri radu motora s povišenim udjelima EGR-a.

Abstract

Engine knock is one of SI engines fundamental problems since its appearance limits the increase of engine efficiency. Engine knock is an uncontrolled combustion that can cause a significant mechanical damage to vital engine parts and it depends on numerous parameters, such as engine load, engine speed, air-fuel ratio, temperature and pressure of the mixture, etc. Due to its importance for the operation of Otto’s engine, the description and the prediction of the knock is a major challenge for development engineers. Since experimental research requires the use of an extremely expensive equipment and is very time-consuming, over the past few years engineering tools for the process analysis have been developed that significantly accelerate the engine development process. A new model of predicting engine knock has been developed at the Chair of IS Engines and Motor Vehicles, which includes the calculation of the temperature inhomogeneity of the unburned zone and the calculation of the detailed chemical kinetics of the auto-ignition of the used fuel. The model was validated at the standard operation of Otto engine, however was not validated in engine operation with the engine with higher EGR ratio. Since the EGR system has become an indispensable vehicle component along with other exhaust gas aftertreatment technologies, it is necessary to validate the model for prediction of knock in that operating mode. For this purpose, on the experimental engine at the Laboratory of Engines and Vehicles, 11 operating points were measured, which primarily differed in mass fraction of EGR and the intensity of the knock. In the experimental analysis, the MAPO indicator was used as a measure of intensity of the knock combustion. Validation of the model was performed by comparing the MAPO indicator value from the experiment and the intensity of knock combustion obtained by the simulation. Analysis of the results showed that the new model predicts the occurrence of knock combustion very well in the operation of engines with higher EGR ratio.

Item Type: Thesis (Undergraduate thesis)
Uncontrolled Keywords: detonacija; simulacije; EGR
Keywords (Croatian): engine knock; simulation; EGR
Subjects: TECHNICAL SCIENCE > Mechanical Engineering > process energy engineering
Divisions: 400 Department of IC Engines and Mechanical Handling Equipment > 410 Chair of IC Engines and Motor Vehicles
Date Deposited: 23 Feb 2018 09:06
Last Modified: 06 Mar 2018 16:10
URI: http://repozitorij.fsb.hr/id/eprint/8396

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