An Internally Heated Tip Injector to Reduce HC Emissions During Cold-Start 1999-01-0792
The majority of hydrocarbon (HC) emissions in the FTP cycles are generated during cold starts when the catalyst is cold, and a large percentage of the injected fuel does not vaporize well. D Dduring this portion of the test, a wall film builds on the intake ports, fuel drips into the cylinder, and manifold pressure changes cause excursions in the air/fuel ratio (AFR).
This paper presents the concept of heating fuel inside an injector to enhance vaporization in the intake manifold. Different injector parameters, such as heater temperature and injector tip geometry, were analyzed for different flow rates. The heat transfer inside the injector was investigated experimentally and numerically, using computational fluid dynamics (CFD) modeling. The Sauter Mean Diameter (SMD) of the fuel spray was measured and evaluated under different vacuum conditions using a Phase Doppler Particle Analyzer (PDPA). Injection and ignition timing sweeps, load steps, and start tests were assessed according to HC emissions.
The overall test results showed that within 5 seconds after turning on the heat, a fuel temperature of 65°C was reached. The SMD and largest particles were significantly reduced. The enhanced spray atomization led to reduced HC emissions and greatly improved transient A/F control.