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Technical Paper

Development of a Friction Optimized Engine

Evolving emissions legislation and concerns for diminishing fuel reserves continue to prompt the automotive industry to seek improvements in engine operation. The application of advanced combustion and system-based concepts is being studied in detail. However, it is believed prudent to first consider the optimization of the friction of the engine, to allow a more cost effective CO2 and fuel consumption reduction policy. MAHLE has developed an optimised friction engine to demonstrate the potential fuel consumption gains available to engine manufacturers and designers. The baseline 2.0 litre turbocharged, direct injection gasoline engine was modified to suit the application of new friction optimized components. This included piston, ring pack, connecting rod, crankshaft bearings, lubrication system, valvetrain and cooling system. A discussion of the design changes, including analysis results, is made. Motored rig and fired engine test results are presented to show the individual gains.
Technical Paper

A New Combustion System Achieving High Drive Cycle Fuel Economy Improvements in a Modern Vehicle Powertrain

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.
Technical Paper

Sub-200 g/kWh BSFC on a Light Duty Gasoline Engine

Increasingly stringent global fuel economy and carbon dioxide (CO2) legislation for light duty passenger cars has created an interest in unconventional operating modes. One such mode in spark ignition (SI) gasoline engines is lean combustion. While lean operation in SI engines has previously demonstrated the ability to reduce fuel consumption, the degree of enleanment capability of the system is limited by increasingly unstable combustion in the lean region, particularly for homogeneous lean approaches. MAHLE Jet Ignition® (MJI) is a pre-chamber-based combustion system that extends this lean limit beyond the capabilities of modern SI engines by increasing the ignition energy present in the system. This allows the engine to exploit the benefits of homogeneous ultra-lean (λ > ∼1.6) combustion, namely reduced fuel consumption and reduced emissions of nitrogen oxides (NOx). Pre-chamber combustors such as that utilized in MJI have been studied extensively for decades.
Technical Paper

Exhaust Gas Recirculation for Improved Part and Full Load Fuel Economy in a Turbocharged Gasoline Engine

The work was concerned with the use of exhaust gas recirculation to minimise CO2 and pollutant emissions over a wide operating range in a multi-cylinder research engine. Under part-load conditions a combination of internal and external EGR was used to invoke controlled auto ignition combustion and improve fuel consumption. Outside the CAI regime, small additional fuel savings could be made by employing reduced EGR rates in spark ignition combustion mode. At boosted high load conditions a comparison of excess fuel, excess air and cooled external EGR charge dilution was made. It was apparent that cooled EGR was a more effective suppressant of knock than excess air, with combustion phasing further advanced towards the optimum and improved combustion stability achieved over a wider operating range. The full load emissions reduction potential of EGR was also demonstrated, with emissions of CO2 reduced by up to 17% and engine-out HC and CO decreased by up to 80%.
Technical Paper

The Effects of Combined Internal and External Exhaust Gas Recirculation on Gasoline Controlled Auto-Ignition

A combination of internal and external exhaust gas recirculation has been used to increase the attainable load in a multi-cylinder engine operated in gasoline controlled auto-ignition. The amount of residual gas trapped in the cylinder was adjusted via the negative valve overlap method. The flow of externally re-circulated exhaust gas was varied using a typical production level valve. Under stoichiometric fuelling conditions, the highest output achieved using internal exhaust gas was limited by excessive pressure rise and unacceptable levels of knock. Introducing additional external exhaust gas was found to retard ignition, reduce the rate of heat release and limit the peak knocking pressure. In turn, an increase in engine load of 20-65% was achieved, with greatest benefit governed by combustion stability limits and realised at lower engine speeds.
Technical Paper

A New 3 Cylinder 1.2l Advanced Downsizing Technology Demonstrator Engine

This paper introduces the new 3 cylinder 1.2l downsizing technology demonstrator engine from MAHLE. The purpose of the paper is to describe the design approach and technologies applied. Emphasis is given to the low speed torque and transient response issues associated with advanced downsized engines. An overview of the design of all engine systems is provided, including the predictive analysis results used to validate, guide and optimize the design process. The design targets outstanding levels of performance, fuel consumption & drivability.
Technical Paper

The Impact of Engine Displacement on Efficiency Loss Pathways in a Highly Dilute Jet Ignition Engine

Increasingly strict efficiency regulations for automotive applications and emissions regulations for stationary power generation applications have motivated investigation of alternative combustion modes for spark ignition engines. Ultra-lean (λ > ~1.6) combustion via air dilution is one such mode that provides the benefits of reduced fuel consumption and reduced emissions of nitrogen oxides. Jet ignition is a pre-chamber-based combustion system that enables enleanment beyond what is achievable with traditional spark ignition engines. Previous studies of MAHLE’s Jet Ignition concept have primarily focused on light-duty gasoline engines. With increasing demand for fuel flexibility, particularly in power generation, and smaller engine displacement for range extender engines in automotive hybrid applications, it is important to characterize how the performance of this technology translates to other fuels and engine displacements.
Journal Article

Development of a Turbocharged Direct Injection Downsizing Demonstrator Engine

This paper describes the initial development of a 3 cylinder 1.2l technology demonstrator engine from MAHLE. The purpose of this highly turbocharged direct injection engine is to demonstrate production-ready technologies that enable low CO2 emissions via downsizing by 50%. Downsizing is one of the most proven paths to CO2 emission reduction. By using careful design, a 2.4 l engine can be replaced by a 1.2l engine that has superior torque at all speeds and on-road fuel consumption benefits of 25 - 30%. A two-stage turbocharging system has been developed for the engine to enable good transient response and the high torque levels at all engine speeds demanded by a downsizing approach. Several options were tested and the final system exceeds the 30bar peak BMEP target with stoichiometric fuelling. Indeed, lambda = 1.0 fuelling is maintained over the majority of the full-load line and the 144kW peak power requirement is fulfilled at only 6000 rpm.