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This article deals with application of turbulent jet ignition technique to heavy duty multi-cylinder natural gas engine for mobile application. Pre-chamber spark plugs are identified as a promising means of achieving turbulent jet ignition as they require minimal engine modification with respect to component packaging in cylinder head and the ignition system. Detailed experiments were performed with a 6 cylinder 9.4 liter turbo-charged engine equipped with multi-point gas injection system to compare performance and emissions characteristics of operation with pre-chamber and conventional spark plug. The results indicate that ignition capability is significantly enhanced as flame development angle and combustion duration are reduced by upto 30 % compared to those with conventional spark plugs at certain operating points.

This article deals with study of ionization current sensing technique's signal characteristics while operating with pre-chamber spark plug to achieve plasma jet ignition in a 6 cylinder 9 liter turbo-charged natural gas engine under EGR and excess air dilution. Unlike the signal with conventional spark plug which can be divided into distinct chemical and thermal ionization peaks, the signal with pre-chamber spark plug shows a much larger first peak and a negligible second peak thereafter. Many studies in past have found the time of second peak coinciding with the time of maximum cylinder pressure and this correlation has been used as an input to combustion control systems but the absence of second peak makes application of this concept difficult with pre-chamber spark plug.

It has previously been shown by the authors that the pre-chamber ignition technique operating with fuel-rich pre-chamber combustion strategy is a very effective means of extending the lean limit of combustion with excess air in heavy duty natural gas engines in order to improve indicated efficiency and reduce emissions. This article presents a study of the influence of pre-chamber volume and nozzle diameter on the resultant ignition characteristics. The two parameters varied are the ratio of pre-chamber volume to engine's clearance volume and the ratio of total area of connecting nozzle to the pre-chamber volume. Each parameter is varied in 3 steps hence forming a 3 by 3 test matrix. The experiments are performed on a single cylinder 2L engine fitted with a custom made pre-chamber capable of spark ignition, fuel injection and pressure measurement.

This study investigates the effect of exhaust rebreathe (RB) on the low-load regime of a Gasoline Compression Ignition (GCI) heavy-duty engine. For this engine, a custom-designed cam profile with a second exhaust event occurring during the intake stroke was tested under different experimental load and speed conditions. First, the study focuses on the of rebreathe on combustion and gas exchange processes in the low load range of 240-300 kPa BMEP at three key speeds: 820, 1200, and 1600 rpm. Then, a general analysis of the thermal management of this technology is assessed in the low-load map, evaluating the impact on turbine outlet temperature and after-treatment performance related to the conversion rates for NOx and total hydrocarbons (THC). The detailed analysis revealed an increase of around 9% in the trapped residuals for the RB operation, translating to an in-cylinder temperature increase and raising the exhaust temperature up to 50°C.

The global automotive industry is undergoing a significant transition as battery electric vehicles enter the market and diesel sales decline. It is widely recognized that internal combustion engines (ICE) are needed for transport for years to come, however, demands on fuel efficiency, emissions, cost, and performance are extremely challenging. Gasoline compression ignition (GCI) is one approach to achieving demanding future efficiency and emissions targets. A key technology enabler for GCI is partially premixed, compression ignition (PPCI) combustion, which involves two high-pressure, late, fuel injections during the compression stroke. Both NOx and smoke emissions are greatly reduced relative to diesel engines, and this reduces aftertreatment (AT) requirements significantly. Exhaust rebreathing (RB) is used for robust low-load and cold operation. This is enabled by use of 2-Step, mode switching rocker arms to allow switching between rebreathe and normal combustion modes.

Following global trends of increasingly stringent greenhouse gas (GHG) and criteria pollutant regulations, India will likely introduce within the next decade equivalent Bharat Stage (BS) regulations for Diesel engines requiring simultaneous reduction in CO2 emissions and up to 90% reduction in NOx emission from current BS-VI levels. Consequently, automakers are likely to face tremendous challenges in meeting such emission reduction requirements while maintaining performance and vehicle total cost of ownership (TCO), especially in the Indian market, which has experienced significant tightening of emission regulation during the past decade. Therefore, it is conceivable that cost effective approaches for improving existing diesel engines platforms for future regulations would be of high strategic importance for automakers.

It is widely recognized that internal combustion engines (ICE) are needed for transport worldwide for years to come, however, demands on ICE fuel efficiency, emissions, cost, and performance are extremely challenging. Gasoline compression ignition (GCI) is one approach to achieve demanding efficiency and emissions targets. At Aramco Research Center-Detroit, an advanced, multi-cylinder GCI engine was designed and built using the latest combustion system, engine controls, and lean aftertreatment. The combustion system uses Aramco’s PPCI-diffusion process for ultra-low NOx and smoke. A P2 48V mild hybrid system was integrated on the engine for braking energy recovery and improved cold starts. For robust low-load operation, a 2-step valvetrain system was used for exhaust rebreathing. Test data showed that part-load fuel consumption was reduced 7 to 10 percent relative to a competitive 2.0L European diesel engine.