The exhaust energy utilization of a turbocompound engine combined with divided exhaust period

Aghaali, Habib; Ångström, Hans-Erik

doi:10.1533/978081000342.179

Cited by 5 publications

(1 citation statement)

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“…Lower residual gas fraction also enables ignition timing to be advanced hence reducing the cylinder pressure and temperature. Reducing 15% of residual gas fraction when knock intensity is constant at 30kPa allows the ignition timing to be advanced up to 5 CAD, which improves the efficiency of combustion.Exhaust valve modulation concepts such as Divided Exhaust Period (DEP) [14][15][16][17] and Valve-Event Modulated Boost (VEMB) [18,19] direct the highest energy exhaust flow from the cylinder into a blow down manifold, which is connected to the turbocharger turbine, and the lower energy exhaust flow into a scavenging manifold, which bypasses the turbine. This arrangement helps to reduce the back pressure experienced by the piston during scavenging, with the pumping work reduced as a consequence.…”

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confidence: 99%

Turbocharger Matching Method for Reducing Residual Concentration in a Turbocharged Gasoline Engine

Ismail¹,

Costall²,

Martinez-Botas³

et al. 2015

SAE Technical Paper Series

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In a turbocharged engine, preserving the maximum amount of exhaust pulse energy for turbine operation will result in improved low end torque and engine transient response. However, the exhaust flow entering the turbine is highly unsteady, and the presence of the turbine as a restriction in the exhaust flow results in a higher pressure at the cylinder exhaust ports and consequently poor scavenging. This leads to an increase in the amount of residual gas in the combustion chamber, compared to the naturally-aspirated equivalent, thereby increasing the tendency for engine knock. If the level of residual gas can be reduced and controlled, it should enable the engine to operate at a higher compression ratio, improving its thermal efficiency. This paper presents a method of turbocharger matching for reducing residual gas content in a turbocharged engine. The turbine is first scaled to a larger size as a preliminary step towards reducing back pressure and thus the residual gas concentration in-cylinder. However a larger turbine causes a torque deficit at low engine speeds. So in a following step, pulse separation is used. In optimal pulse separation, the gas exchange process in one cylinder is completely unimpeded by pressure pulses emanating from other cylinders, thereby preserving the exhaust pulse energy entering the turbine. A pulse-divided exhaust manifold enables this by isolating the manifold runners emanating from certain cylinder groups, even as far as the junction with the turbine housing.This combination of appropriate turbine sizing and pulse-divided exhaust manifold design is applied to a Proton 1.6-litre CamPro CFE turbocharged gasoline engine model. The use of a pulse-divided exhaust manifold allows the turbine to be increased in size by 2.5 times (on a mass flow rate basis) while maintaining the same torque and power performance. As a consequence, lower back pressure and improved scavenging reduces the residual concentration by up to 43%, while the brake specific fuel consumption improves by approx. 1%, before any modification to the compression ratio is made. IntroductionMany efforts have been made globally to reduce greenhouse gasses, particularly the CO 2 emissions produced by motor vehicles. Based on a study of global atmospheric trace gases by the Carbon Dioxide Information Analysis Center (CDIAC), CO 2 has increased from 280ppm pre-1750 to 386ppm in 2009, an increase of 106ppm. Modern road vehicles are required to meet stringent emission and fuel economy requirements, and several emission standards for passenger cars are already established or are currently being proposed to tackle climate change, and some are in the process of revision. For example, the European Commission aims to reduce CO 2 emissions from light-duty vehicles to a level of 95g/km by 2020 [1]. As a consequence, researchers and manufacturers have been investigating advanced technologies to meet these demands. One method that can be viewed as a viable short-to-medium term solution [2] is to use a smaller capacity engine that...

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confidence: 99%