Piston bowl geometry GUDRUN (M. Korkmaz)

Test bench setup GUDRUN (M. Korkmaz)

EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF THE IRREGULAR COMBUSTION PHENOMENON "MEGA-KNOCK" (GUDRUN)

The internal combustion engine (ICE) is still crucial in the field of mobility due to its high efficiency, durability, high power density, and reliability. Nevertheless, the ICE is currently facing considerable challenges. For sustainable long-term operation of ICE, it is mandatory to further reduce engine-out emissions and increase engine efficiency.

One viable option for gasoline engines is the usage of a combination of solutions like downsizing (re-duction of the engine size), direct fuel injection technology and turbocharging. Unfortunately, this approach has a drawback in the high load operation due to an abnormal combustion event (“Mega-Knock”). The objective of this study is to investigate the influence of charge motion and cooled EGR on the Mega-Knock.

A modified single-cylinder research engine (SCE) that is based on a production engine is employed. For the investigations, the cylinder head was modified for optical access. In this configuration up to three endoscopes can be used simultaneously. The relevant engine and injector parameters are listed in Table 1 and a schematic test bench layout is illustrated in Figure 1.

Table 1: Engine and injector specifications.

Figure 1:Schematic test bench layout.

For maintaining well-defined boundary conditions, the test bench is equipped with oil, water, and fuel conditioning systems. The air supply is ensured by an external charger unit and the desired intake air temperature is provided by the external heater. The load is represented by a DC motor (speed-controlled) equipped with a torque meter. For controlling the engine (i.e., intake pressure, exhaust pressure, injection timing, duration, cylinder pressure, etc.), a customized engine control unit (ECU) is used. The gas pressures are metered with piezoresistive sensors and the gas temperatures are measured with thermocouples, which are placed within the manifolds. The exhaust gas is collected using a heated probe and emissions data including NOx, THC, CO, CO2, O2, and PM were metered in the appropriate analyzers. Measurements of the air-fuel-ratio (AFR) were performed by the EGR 5230 module. The SCE is equipped with a piezoelectric pressure transducer (mounted via a glow plug adapter) in conjunction with the charge amplifier. Hereby, reliable thermodynamic data determination is ensured. The analysis of in-cylinder parameters, e.g., indicated mean effective pressure of the high-pressure process (IMEPHP), combustion phasing (CA50), and heat release rate (HRR) are evaluated in a thermodynamic real-time analysis module (TRA) for 100 consecutive cycles.

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