Infrared Borescopic Evaluation of High-Energy and Long-Duration Ignition Systems for Lean/Dilute Combustion in Heavy-Duty Natural-Gas Engines University of Michigan

Format:

Conference/Event

Author/Creator:

Mazacioglu, Mazacioglu, author.

Contributor:

Gross, Michael

Kern, Justin

Sick, Volker

Conference Name:

WCX World Congress Experience (2018-04-10 : Detroit, Michigan, United States)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2018

Summary:

AbstractNatural gas (NG) is attractive for heavy-duty (HD) engines for reasons of cost stability, emissions, and fuel security. NG cannot be reliably compression-ignited, but conventional gasoline ignition systems are not optimized for NG and are challenged to ignite mixtures that are lean or diluted with exhaust-gas recirculation (EGR). NG ignition is particularly challenging in large-bore engines, where completing combustion in the available time is more difficult. Using two high-speed infrared (IR) cameras with borescopic access to one cylinder of an HD NG engine, the effect of ignition system on the early flame-kernel development and cycle-to-cycle variability (CCV) was investigated. Imaging in the IR yielded strong signals from water emission lines, which located the flame front and burned-gas regions and obviated image intensifiers. A 9.7-liter, six-cylinder engine was modified to enable exhaust-gas recirculation and to provide optical access. Three ignition technologies were studied: a conventional system delivering 65mJ of energy to each spark, a high-energy conventional system delivering 140mJ, and a Bosch Controlled Electronic Ignition (CEI) system. CEI uses electronics to extend the ignition event, yielding sparks up to 5ms in duration with up to 300mJ of energy. Air/fuel equivalence ratios, λ, as high as 1.6 (with minimum EGR) and EGR fractions as high as 23% (stoichiometric) were tested; ignition delay, engine-out emissions, fuel consumption and image-derived parameters were compared. In most lean or dilute cases, the 140-mJ system yielded the lowest CCV. The imagery provided information about the early stages of ignition and combustion, where pressure measurements are not reliable. Image-based metrics also revealed that early flame kernels located further from the head yielded better combustion, showing that borescopic IR imaging can provide guidance for future engine design

Notes:

Vendor supplied data

Publisher Number:

2018-01-1149

Access Restriction:

Restricted for use by site license