Effect of Gasoline Fuel Additives on Combustion and Engine Performance

3.1.5
 
Spray Apparatus Overview 
The overall schematics of the experimental facility, used for droplet size 
analysis, can be seen in Figure 3.6. The equipment includes a constant volume 
combustion vessel (CVCV), Malvern Spraytec laser diffraction system, GDI high 
pressure swirl-type injector and a fuel pressure accumulator.
Figure 3.6: Schematics of experimental facility for spray analysis 
The injector was powered by a LifeRacing GDI driver and injections 
controlled through a LabView control program. The software was additionally used to 
send a signal to the Malvern system for triggered data acquisition. The same program 
was also used to monitor fuel pressure and ambient conditions. Shadowgraph images 
were taken with a Photron APX-RS high speed camera coupled with a Nikon 50 mm 
f/1.8 lens.
3.2
 
Combustion Experiments 
Combustion experiments were carried out in the UCL constant volume 
combustion vessel (or the bomb) and a single cylinder Ricardo E6 research engine. 
The following sections will describe the set-up used with each of the methods. 

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3.2 Combustion Experiments 
81 
3.2.1
 
Constant Volume Combustion Vessel 
The set-up for combustion experiments comprised of an ignition system and 
appropriate control methods for temperatures and pressures prior to a combustion 
event. Two types of gasoline combustion were carried out in the vessel: 

Gasoline spray combustion 

Gasoline vapour combustion 
Spray combustion involved using the gasoline direct injection system 
introduced in Section 3.1.1. Fuel was delivered in liquid jet form and sprayed into the 
combustion vessel at pre-determined gas conditions for stratified combustion. 
Alternatively, the gasoline was introduced into the vessel via a syringe pump and 
vaporised for homogeneous gas combustion.
Due to above atmospheric pressures used with both methods, vessel gas 
leakage characteristics were determined. This is displayed in Figure 3.7. Over a 4 hour 
period at ambient temperature, a projected 8 % drop in pressure occurred. The 
experimental duration in current study was estimated to be 25 minutes for spray 
combustion (combustion event every 30 seconds, 50 repeats in total) and less than 10 
minutes for gasoline vapour combustion (fuel pumped in at 0.5 ml/min, 2-8 ml of fuel 
– dependent upon pressure/air-fuel ratio conditions required prior to combustion, 
single combustion event) during which pressure losses of less than 1 % were expected.