22-05-2012, 02:17 PM
Effects of ethanol content on gasohol pfi engine wide-open throttle operation
Effects of ethanol content on gasohol .pptx (Size: 1.08 MB / Downloads: 56)
Introduction
Ethanol has been increasingly introduced as a supplement to the petroleum based gasoline with the renewable fuel mandate required in US and the world.
A significant attribute of ethanol is its high heat of vaporization compared to gasoline
More ethanol is required for forming stoichiometric mixture compared to gasoline thus there could be substantial evaporative cooling
The case of PFI engines is important because the configuration still dominates over the US and world markets and is expected to be so for the immediate future.
This paper investigates the effects of gasohol on knock and NOx emission for a PFI engine at WOT operation.
Experimental Set up and Procedure
A 1.8L I-4 DOHC spark-ignition engine was modified for single cylinder operation on a motoring dynamometer. The engine featured a centrally located spark plug, a shallow bowl-in-piston, and it is representative of modern spark-ignition engines. The intake and exhaust systems were modified to separate the flow through one cylinder from the other three.
A Kistler 6051A piezoelectric pressure transducer coupled to a Kistler 5010 charge amplifier was used for in-cylinder pressure measurements.
The experiments were performed at WOT with λ = 1. The Horiba Mexa-720 Lambda-NOx sensor was used for exhaust gas measurements. Engine coolant temperature was at 80o C.
Results at Fixed Spark Timing
To assess the effect of ethanol content on the engine behavior, operation at fixed spark timing was studied.
At 1500 rpm, spark timing was chosen to be at -2º BTDC, a value sufficiently retard so that the engine would not knock for the range of gasohol fuel considered.