Procjena turbulentne brzine širenja plamena iz izmjerenog toka tlaka u cilindru Ottovog motora

undergraduate thesis

• Title (english): Estimation of the turbulent flame speed from the analysis of measured in-cylinder pressure profile of spark ignition engine
• Author: Mateo Jakoubek
• Mentor: Momir Sjerić (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2017-09-28, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

U ovom završnom radu razrađen je model procjene turbulentne brzine širenja plamena u svrhu numeričkog modeliranja procesa izgaranja u Ottovim motorima. Opisan je proračun oslobađanja topline iz izmjerenog toka tlaka u cilindru motora te prikazan izračun turbulentne brzine širenja plamena i turbulentne kinetičke energije koja zadovoljava razmatranu brzinu oslobađanja topline. Na osnovu procijenjenih vrijednosti turbulentne kinetičke energije pri različitim brzinama vrtnje motora moguće je provesti kalibraciju konstanti modela turbulencije potrebnog za proračun izgaranja primjenom kvazidimenzijskih modela izgaranja u Ottovim motorima.

U analizi je razmatran bezdimenzijski (0-D) pristup u kombinaciji s kvazidimenzijskim modelom izgaranja. Bezdimenzijski model naziva se još i termodinamički model jer se baziraj na 1. glavnom stavku termodinamike i zakonu očuvanja mase. Kvazidimenzijski modeli upotrjebljuju se u sve većoj mjeri budući da koriste termodinamički (0-D) pristup, ali se u proračunu brzine izgaranja u obzir uzima geometrija prostora izgaranja. U Laboratoriju za motore i vozila provedena su eksperimentalna mjerenja na motoru Hatz 1D81 za nekoliko radnih točaka pri punom opterećenju i različitim brzinama vrtnje motora. Kemijska energija dobivena je iz benzina, a trenutak paljenja električnom iskrom na svakoj brzini vrtnje motora određen je tako da se ostvari povoljan tijek izgaranja bez pojave detonantnog izgaranja. Za svaku radnu točku snimljeni su uzastopni profili tlaka u cilindru motora za 300 radnih ciklusa te su rezultati tlaka osrednjeni kako bi se pomoću tih iznosa izračunala brzina oslobađanja topline. Prije izračuna brzine širenja plamena i turbulentne kinetičke energije napravljen je izračun laminarnih ploha plamena i izgorjelog volumena u kojem je korišten 3-D CAD model prostora izgaranja za razmatrani motor. Nakon toga, model procjene turbulentne brzine plamena razrađen je u programskom paketu MATLAB. Na kraju rada prikazani su rezultati simulacije provedene u programskom paketu AVL BOOST kako bi se usporedile procijenjene i izračunate vrijednosti turbulentne kinetičke energije.

Abstract (english)

In this thesis, turbulent flame speed was estimated from measured in-cylinder pressure profile with the aim to numerically model the combustion process in spark-ignition engines.

The rate of heat release was calculated from the measured pressure profile in the engine cylinder. Furthermore, the turbulent flame speed and the turbulent kinetic energy that satisfies the considered rate of heat release were presented. Based on the estimated values of turbulent kinetic energy at different engine speeds, it is possible to calibrate the turbulence model constants required for combustion calculation using quasi-dimensional combustion models in the SI engine.

In the analysis, a non-dimensional (0-D) approach was considered in combination with the quasidimensional combustion model. The non-dimensional models are also called thermodynamic models because they are based on the first law of thermodynamics and law of mass conservation. The quasi-dimensional models are increasingly used since they use a thermodynamic (0-D) approach, but combustion geometry is considered in the ROHR calculation.

Experimental measurements were carried out at the Laboratory for engines and vehicles on the Hatz 1D81 for several operating points at full load and different engine speeds. Chemical energy was obtained from gasoline while the ignition at each engine speed was determined so as to achieve combustion process without the detonation. For each working point, in-cylinder pressure profiles for 300 cycles have been recorded and the pressure results were averaged in order to calculate the rate of heat release. Before calculating the flame speed and the turbulent kinetic energy, a calculation of the free flame surface area and the burned volume had been made using the 3-D CAD model of combustion chamber of experimental engine. Thereafter, turbulent speed estimation model was elaborated in the MATLAB software package. Lastly, the results of the simulation carried out in the AVL BOOST program package were presented in order to compare the estimated and calculated values of turbulent kinetic energy.

• Keywords: Ottov motor; turbulentna brzina plamena; turbulentna pulzacija brzine
• Keywords (english): spark-ignition engine; turbulent flame speed; turbulent pulsation velocity
• Language: croatian
• URN:NBN: urn:nbn:hr:235:894224
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka strojarstva (sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-05-22 20:22:55