Influence of Ethanol Blends on Low Speed Pre-Ignition in Direct-Injected Turbo Charged Gasoline Engines

Paper #:
  • 2017-01-0687

Published:
  • 2017-03-28
Abstract:
Modern combustion engines must meet increasingly higher requirements concerning emission standards, fuel economy, performance characteristics and comfort. Especially fuel consumption and the related CO2 emissions have been moved into public focus within the last years. One possibility to meet those requirements is downsizing. Engine downsizing is intended to achieve a reduction of fuel consumption through measures that allow reducing displacement while simultaneously keeping or increasing power. However, to reach that goal, downsized engines need high brake mean effective pressure levels which are well in excess of 20bar. When targeting high output levels at low engine speeds, undesired combustion events with high cylinder peak pressures can occur that can severely damage the engine. These phenomena, typically called low speed pre-ignition (LSPI), set currently an undesired limit to downsizing. This study analyzes the influence of ethanol fuel content on low speed pre-ignition events in a direct-injection turbo charged gasoline engine with a homogeneous (λ = 1) common rail high pressure injection system, side mounted multi-hole injectors and dual variable valve timing. All experiments were conducted on a steady state engine test bench with intake air, coolant, oil and fuel conditioning to be able to separate fuel effects from boundary condition influences. In addition, the engine was equipped with a prototype engine controller allowing negating the influence of control algorithms on combustion. Five ethanol fuels containing different levels of ethanol were blended using the same base fuel and denatured ethanol. The investigated blends included E10, E20, E30, E50 and E85 fuels. Subsequently, test runs were performed to understand the impact of different ethanol blends on occurrence, number and pressure characteristics on LSPI.
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