Experimental and computational analysis of the combustion evolution in direct-injection spark-controlled jet ignition engines fuelled with gaseous fuels

Abstract

Jet ignition and direct fuel injection are potential enablers of higher-efficiency, cleaner internal combustion engines (ICEs), where very lean mixtures of gaseous fuels could be burned with pollutants formation below Euro 6 levels, efficiencies approaching 50 per cent full load, and small efficiency penalties operating part load. The lean-burn direct-injection (DI) jet ignition ICE uses a fuel injection and mixture ignition system consisting of one main-chamber DI fuel injector and one small jet ignition pre-chamber per engine cylinder. The jet ignition pre-chamber is connected to the main chamber through calibrated orifices and accommodates a second DI fuel injector. In the spark plug version, the jet ignition pre-chamber includes a spark plug which ignites the slightly rich pre-chamber mixture which then, in turn, bulk ignites the ultra-lean stratified main-chamber mixture through the multiple jets of hot reacting gases entering the in-cylinder volume. The paper uses coupled computer-aided engineering and computational fluid dynamics (CFD) simulations to provide better details of the operation of the jet ignition pre-chamber (analysed so far with downstream experiments or stand-alone CFD simulations), thus resulting in a better understanding of the complex interactions between chemistry and turbulence that govern the pre-chamber flow and combustion.

Design of Direct Injection Jet Ignition High Performance Naturally Aspirated Motorcycle Engines

“…With jet ignition, the combustion duration is drastically reduced, the completeness of combustion is improved, and the cyclic variability is reduced. The assumptions here made for the increments of compression ratio and the reduction of the combustion angle follow best practices based on experimental and numerical evidence [8,[17][18][19][20][21]. The stoichiometric PFI SI engine has a compression ratio of 13.5:1, completeness of combustion 98%, angle of 50% combustion, 9 degrees of crank angle after top dead center, and combustion angle 10-90% 28 degrees of crank angle.…”

“…About the same power and fuel efficiency may also be delivered with stoichiometric engines direct injection jet ignition two-stroke of 750 cm 3 .Application to premixed mixtures has been fostered by ex-students of Prof. H.C. Watson, then working in Mahle and the University of Michigan since 2009. Developments by Mahle are reported in the use of jet ignition with premixed more than stratified mixtures [10][11][12][13][14][15][16].Application to lean stratified mixtures by jet ignition has been mostly nurtured by the author, who was a collaborator of Prof. H.C. Watson from 2006 to 2009, working largely unsupported as independent scientist.Jet ignition was proposed as a coupling to direct injection to work lean stratified, [17][18][19][20][21]. The advantage of the coupling was the opportunity to produce a central cloud of nearly stoichiometric mixture at the center of the combustion chamber with a surrounding cushion of air then bulk, high energy, ignited by multiple jets of hot reacting gases and rapidly and completely burned with reduced heat losses.…”

“…This also translates into a better fuel conversion efficiency, even if it is mostly at low loads. The concept is better detailed in [17][18][19][20][21]. It is proven by the achievements of F1 teams.Even if JI may also be used with PFI and homogeneous mixtures, JI and DI translate in much faster combustion rates, especially running lean stratified.…”

“…Jet ignition was proposed as a coupling to direct injection to work lean stratified, [17][18][19][20][21]. The advantage of the coupling was the opportunity to produce a central cloud of nearly stoichiometric mixture at the center of the combustion chamber with a surrounding cushion of air then bulk, high energy, ignited by multiple jets of hot reacting gases and rapidly and completely burned with reduced heat losses.…”

A computational study on the effect of the orifice size on the performance of a turbulent jet ignition system

“…These include strategies such as directinjection stratified-charge combustion, [5][6][7][8][9] homogeneous charge compression ignition, [10][11][12][13][14][15] and prechamberinitiated combustion. 4,[16][17][18] The subject of the computational simulations presented below is the turbulent jet ignition (TJI) system, which is a prechamber combustion device.…”