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Technical Paper

Spark Mechanism in High Speed Flow

2019-04-02
2019-01-0729
An experimental study was performed to investigate spark ignition and subsequent spark stretch evolution of inert nitrogen charge gas under high-velocity flow conditions across the electrode gap in a constant-volume optical combustion vessel. The vessel is capable of generating various in-cylinder thermodynamic conditions representative of light-duty spark ignition engines. It realizes a high flow velocity of 32 m/s created by a new high cross flow design. The characteristic behavior of the spark stretch was captured through a high-speed imaging of flow under elevated pressure conditions starting from atmosphere to 45 bar. Results show that the spark flowing downstream the spark plug is subject to restrike after electrical breakdown in high speed flows. Spark plug orientations and gap sizes as well as the charge gas pressure are determined to have significant influence on spark stretch development and electrical discharge time prediction.
Technical Paper

Influence of Elevated Injector Temperature on the Spray Characteristics of GDI Sprays

2019-04-02
2019-01-0268
When fuel at elevated temperatures is injected into an ambient environment at a pressure lower than the saturation pressure of the fuel, the fuel vaporizes in the nozzle and/or immediately upon exiting the nozzle; that is, it undergoes flash boiling. It is characterized by a two-phase flow regime co-located with primary breakup, which significantly affects the spray characteristics. Under flash boiling conditions, the near nozzle spray angle increases, which can lead to shorter penetration because of increased entrainment. In a multi-hole injector this can cause other impacts downstream resulting from the increased plume to plume interactions. To study the effect of injector temperature and injection pressure with real fuels, an experimental investigation of the spray characteristics of a summer grade gasoline fuel with 10% ethanol (E10) was conducted in an optically accessible constant volume spray vessel.
Technical Paper

Process for Study of Micro-pilot Diesel-NG Dual Fuel Combustion in a Constant Volume Combustion Vessel Utilizing the Premixed Pre-burn Procedure

2019-04-02
2019-01-1160
A constant volume spray and combustion vessel utilizing the pre-burn mixture procedure to generate pressure, temperature, and composition characteristic of near TDC conditions in compression ignition engines was modified with post pre-burn gas induction to incorporate a premixed methane gas prior to diesel injection to simulate processes in dual fuel engines. Two variants of the methane induction system were developed and studied. The first used a high-flow modified direct injection injector and the second utilized auxiliary ports in the vessel that are used for normal intake and exhaust events. Flow, mixing and limitations of the induction systems were studied. As a result of this study the high-flow modified direct injection injector was selected because of its controlled actuation and rapid closure. Further studies of the induction system limits post pre-burn were conducted to determine the pressure and temperature limits of the methane autoignition.
Technical Paper

Investigation of Multi-Hole Impinging Jet High Pressure Spray Characteristics under Gasoline Engine-Like Conditions

2016-04-05
2016-01-0847
Impingement of jet-to-jet has been found to give improved spray penetration characteristics and higher vaporization rates when compared to multi-hole outwardly injecting fuel injectors which are commonly used in the gasoline engine. The current work studies a non-reacting spray by using a 5-hole impinging-jet style direct-injection injector. The jet-to-jet collision induced by the inwardly opening nozzles of the multi-hole injector produces rapid and short jet breakup which is fundamentally different from how conventional fuel injectors operate. A non-reacting spray study is performed using a 5-hole impinging jet injector and a traditional 6-hole Bosch Hochdruck-Einspritzventil (HDEV)-5 gasoline direct-injection (GDI) injector with gasoline as a fuel injected at 172 bar pressure with ambient temperature of 653 K and 490 K and ambient pressure of 37.4 bar and 12.4 bar.
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