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Toulson E.,Michigan State University | Schock H.J.,Michigan State University | Attard W.P.,Mahle Powertrain
SAE Technical Papers | Year: 2010

This paper reviews progress on turbulent jet ignition systems for otherwise standard spark ignition engines, with focus on small pre-chamber systems (<3% of clearance volume) with auxiliary pre-chamber fueling. The review covers a range of systems including early designs such as those by Gussak and Oppenheim and more recent designs proposed by GM, FEV, Bosch and MAHLE Powertrain. A major advantage of jet ignition systems is that they enable very fast burn rates due to the ignition system producing multiple, distributed ignition sites, which consume the main charge rapidly and with minimal combustion variability. The locally distributed ignition sites allow for increased levels of dilution (lean burn/EGR) when compared to conventional spark ignition combustion. Dilution levels are comparable to those reported in recent homogeneous charge compression ignition (HCCI) systems. In addition, jet ignition systems have the potential for combustion phasing control and hence speed/load range benefits when compared to HCCI, without the need for SI-HCCI combustion mode switching. The faster burn rates also allow for a base compression ratio increase (1-2 points) when compared to spark ignition and when combined with diluted mixture combustion, provide increased engine efficiency. Copyright © 2010 SAE International. Source


Attard W.P.,Mahle Powertrain | Parsons P.,Mahle Powertrain
SAE International Journal of Engines | Year: 2010

Turbulent Jet Ignition is an advanced spark initiated prechamber combustion system for an otherwise standard spark ignition engine found in current on-road vehicles. This next generation pre-chamber design simply replaces the spark plug in a conventional spark ignition engine. Turbulent Jet Ignition enables very fast burn rates due to the ignition system producing multiple, widely distributed ignition sites, which consume the main charge rapidly. This high energy ignition system results from the partially combusted (reacting) pre-chamber products initiating main chamber combustion. The fast burn rates allow for increased levels of dilution (lean burn and/or EGR) when compared to conventional spark ignition combustion, with dilution levels being comparable to other low temperature combustion technologies (HCCI) without the complex control drawbacks. Previous Turbulent Jet Ignition light load results at the world wide mapping point (1500 rev/min, 3.3 bar IMEPn) have demonstrated an 18% improvement in fuel economy, with single digit ppm engine out NOx emissions. This paper focuses on performance, efficiency, emissions and combustion effects of a Turbulent Jet Ignition system operated at unthrottled conditions with load variation achieved by altering the dilution level (excess air and/or EGR). Turbulent Jet Ignition single cylinder experimental results at 1500 rev/min highlight a matched load operating range when compared to conventional spark ignition combustion, with identical peak BMEP and the ability to operate in an unthrottled mode down to 3.9 bar IMEPn with increasing dilution levels. © 2010 SAE International. Source


Attard W.P.,Mahle Powertrain | Parsons P.,Mahle Powertrain
SAE International Journal of Engines | Year: 2010

Turbulent Jet Ignition is an advanced spark initiated prechamber combustion system for an otherwise standard spark ignition engine found in current on-road vehicles. This next generation pre-chamber design simply replaces the spark plug in a conventional spark ignition engine. Turbulent Jet Ignition enables very fast burn rates due to the ignition system producing multiple, widely distributed ignition sites, which consume the main charge rapidly. This high energy ignition system results from the partially combusted (reacting) prechamber products initiating main chamber combustion. The fast burn rates allow for increased levels of dilution (lean burn and/or EGR) when compared to conventional spark ignition combustion, with dilution levels being comparable to other low temperature combustion technologies (HCCI) without the complex control drawbacks. Previous Turbulent Jet Ignition experimental results have highlighted peak net indicated thermal efficiency values of 42% in a standard modern engine platform. Additionally, the pre-chamber combustion system is capable of tolerating up to 54% mass fraction diluent (excess air and EGR) at the world wide mapping point of 1500 rev/min, 3.3 bar IMEPn (~2.62 bar BMEP), resulting in an 18% improvement in fuel economy and near zero engine out NOx emissions. This paper focuses on single cylinder experiments at the world wide mapping point, which attempted to extend the dilution level further by altering the flame kernel development inside the very small but rich pre-chamber environment. Turbulent Jet Ignition experiments incorporated previous techniques found to affect the dilution limits in conventional spark ignition combustions systems. This included variations in spark plug type, orientation, location and electrode gap for the spark plug initiated pre-chamber combustion system. Experimental results highlighted that the pre-chamber combustion system is quite robust and largely unaffected by these changes, unlike conventional spark ignition combustion, as long as combustion inside the prechamber can be initiated. This occurs as combustion in the heavily diluted main chamber is driven by the chemical, thermal and turbulence effects of the propagating jet exiting the pre-chamber and not the flame front itself. Nevertheless, experiments found the eliminating the dead volume near the spark plug inside the pre-chamber, was beneficial in reducing the trapped residuals and thus enabled the dilution level to be slightly improved from an exhaust lambda of 2.08 to 2.14 (54 to 56% mass fraction diluent). © 2010 SAE International. Source


Attard W.P.,Mahle Powertrain | Blaxill H.,Mahle Powertrain
SAE Technical Papers | Year: 2012

Turbulent Jet Ignition is an advanced spark initiated pre-chamber combustion system for otherwise standard spark ignition engines. Combustion in the main chamber is initiated by jets of partially combusted (reacting) pre-chamber products which provide a high energy ignition source. The resultant widely distributed ignition sites allow relatively small flame travel distances enabling short combustion durations and high burn rates. Demonstrated benefits include ultra lean operation (λ>2) at part load and high load knock limit extension. Previous jet ignition experimental results have highlighted high thermal efficiencies, high load capability and near zero engine out NOx emissions in a standard contemporary engine platform. Although previous results of this system have been very promising, the main hurdle has been the need for a dual fuel system, with liquid gasoline used in the main combustion chamber and small fractions of gaseous propane in the pre-chamber. Initial attempts in replacing the pre-chamber gaseous propane with liquid gasoline were problematic, although engine operation was successful at some operating conditions. The poor mixture preparation with liquid gasoline inside the small pre-chamber cavity due to the limited production injector hardware somewhat compromised the thermal efficiency, resulting in slight elevations in NOx emissions. Since specialized pre-chamber injector hardware was not available for evaluation, the purpose of this paper is to demonstrate that this combustion system can operate robustly using gasoline, with vaporized gasoline found to be a successful pre-chamber fuel substitute. With this concept at part load, the test engine recorded a 41.4% peak thermal efficiency, ultra lean operation past lambda 2.1, single digit engine out NOx emissions and a 20% peak fuel economy improvement over the baseline spark ignition system. Copyright © 2012 SAE International. Source


Attard W.P.,Mahle Powertrain | Blaxill H.,Mahle Powertrain
SAE Technical Papers | Year: 2011

Turbulent Jet Ignition is an advanced spark initiated pre-chamber combustion system for otherwise standard spark ignition engines found in current passenger vehicles. This next generation pre-chamber design simply replaces the spark plug in a conventional spark ignition engine. Turbulent Jet Ignition enables very fast burn rates due to the ignition system producing multiple, widely distributed ignition sites, which consume the main charge rapidly. This high energy ignition results from the partially combusted (reacting) pre-chamber products initiating combustion in the main chamber. The distributed ignition sites enable relatively small flame travel distances enabling short combustion durations and high burn rates. Multiple benefits include extending the knock limit and initiating combustion in very dilute mixtures (excess air and/or EGR), with dilution levels being comparable to other low temperature combustion technologies (HCCI), without the complex control drawbacks. Previous Turbulent Jet Ignition experimental results have highlighted peak net indicated thermal efficiency values of 42% in a standard contemporary PFI engine platform. Additionally, the pre-chamber combustion system is capable of tolerating over 50% mass fraction diluent (combination of excess air and EGR) at part load, resulting in near zero engine out NOx emissions. This equates to a greater than 20% peak fuel economy improvement when compared to stoichiometric spark ignition in the same contemporary PFI engine platform. Although previous published results of this combustion system are very promising, the main hurdle of this system has been the dual fuel system, with liquid gasoline used in the main combustion chamber and small fractions of gaseous propane in the pre-chamber. The purpose of this paper is to demonstrate that this combustion system can operate on a single fuel, either gaseous propane or liquid gasoline, thus making the combustion system more practical for production applications. © Copyright 2011 Society of Automotive Engineers of Japan, Inc. and SAE International. Source

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