Spark Heat Transfer Measurements in Flowing Gases

Abstract

RƒSUMƒ DES TRANSFERTS DE CHALEUR ENTRE UNE ƒTINCELLE DÕALLUMAGE ET DES ƒCOULEMENTS GAZEUXË partir de techniques basŽes sur lÕinterfŽromŽtrie holographique, lÕŽnergie totale transfŽrŽe par une Žtincelle aux gaz environnants a ŽtŽ mesurŽe en faisant varier la gŽomŽtrie des Žlectrodes de la bougie dÕallumage, la vitesse des gaz, la pression et le temps de charge de la bobine, cette derni•re Žtant un mod•le standard pour automobile. Pour les diffŽrentes combinaisons et valeurs des param•tres ŽtudiŽs, il a ŽtŽ observŽ une variation du "rendement dÕŽtincelle" (rapport entre lÕŽnergie transmise aux gaz par lÕŽtincelle ˆ lÕŽnergie Žlectrique fournie ˆ la bougie) allant de 20 ˆ 60 %. Pour des conditions rŽelles de fonctionnement dans un moteur, on peut estimer que lÕŽnergie transmise aux gaz par le syst•me dÕallumage est voisine de 30 mJ. Il est aussi montrŽ comment ces mesures de lÕŽnergie totale transfŽrŽe aux gaz, peuvent •tre exploitŽes pour caractŽriser en fonction du temps, la puissance transmise dans lÕŽtincelle gŽnŽrŽe par un syst•me standard dÕallumage inductif. SPARK HEAT TRANSFER MEASUREMENTS IN FLOWING GASESUsing a technique based on holographic interferometry, the total energy transferred from a spark to the surrounding gases was measured for a number of spark plug electrode geometries, flow velocities, gas pressures and coil charge times. A standard automotive ignition coil was used. For the combinations of parameter values studied, we observed "spark efficiencies" (ratio of the energy in the gas heated by the spark to the electrical energy supplied to the spark plug) of from 20 to 60 percent. For realistic engine conditions we estimate the quantity of energy transferred to the gas by our ignition system to be roughly 30 mJ. We show how these measurements of total energy transferred to the gas can be used to estimate the spark power vs. time characteristic of a standard inductive ignition system. MEDICIîN DE LAS TRANSFERENCIAS DE CALOR ENTRE UNA CHISPA DE ENCENDIDO Y LOS FLUJOS GASEOSOSTomando como punto de partida las tŽcnicas fundadas en la interferometr'a hologr ‡fica, se ha procedido a la medici-n de la energ'a total transferida por una chispa a los gases circundantes, haciendo variar la geometr'a de los electrodos de la buj'a de encendido, la velocidad de los gases, la presi-n y el tiempo de carga de la bobina, correspondiendo est ‡ oeltima a un modelo est ‡ndar para autom-vil. Se ha observado, para las distintas combinaciones y valores de los par ‡metros estudiados, una variaci-n del "rendimiento de la chispa" (relaci-n entre la energ'a transmitida a los gases por la chispa a la energ'a elŽctrica suministrada a la buj'a) que oscila entre un 20 y un 60 %. Operando en condiciones reales de funcionamiento de un motor, se puede considerar que la energ'a transmitida a los gases por el sistema de encendido, se aproxima de los 30 mJ. TambiŽn se indica c-mo estas mediciones de la energ'a total transferida a los gases pueden ser aprovechadas para caracterizar, en funci-n del tiempo, la potencia transmitida en ...

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