Mixing and Fuel Atomisation Effects on Premixed Combustion Performance

Abstract

The main objective was to compare a flame stabiliser at constant pressure loss and identical isothermal aerodynamics with three modes of fuel injection: premixed, direct propane injection and direct kerosene injection. A Jet Mixing type of flame stabiliser was used at simulated gas turbine primary conditions. The influence of gaseous mixing effects was to deteriorate the combustion efficiency solely by increasing the CO emissions and to increase the NOx emissions. The flame stability was increased and low CO emissions were achieved at weaker mixtures. Liquid fuel atomisation effects resulted in a further deterioration in combustion efficiency due solely to un-burnt hydrocarbons. However, the NOx emissions were reduced indicating that local stoichiometric burning around single droplets does not occur.

Gas and Liquid Fuel Injection Into an Enclosed Swirling Flow

“…This situation is similar to that argued for the poor flame stability of the Jet Mix type of flame stabiliser using liquid fuels in Ref. 21.…”

“…The poor flame stability with kerosene prevents low NO x emissions from being achieved by operating with a weaker primary zone. This situation is different for that found with the Jet Mix flame stabiliser with kerosene (21). The Jet Mix system showed lower NO x emissions with kerosene than with propane.…”

Air Blast Atomization as a Function of Pressure Loss for Large Air Flow Rates

“…This has been shown to have extremely low NOx emissions for gaseous fuels at simulated gas turbine primary zone conditions (Andrews et al, 1983;Al Dabagh et al, 1985;Abdul-Aziz and Andrews, 1985). Tests with liquid fuels (Andrews et al, 1983;Abdul-Aziz et al, 1987a,b) have shown that the system has low smoke characteristics and has only a small increase in the gaseous fuel NOx emissions. The influence of pressure loss on the performance of gaseous and liquid fuels showed that liquid fuels were more sensitive to pressure loss influences ( Abdul-Aziz et al, 1987a,b).…”

Low NOx Primary Zones Using Jet Mixing Shear Layer Combustion

“…Although these have some advantages, Ahmad et al (5)(6)(7)(8)(9) have shown that the NOx emissions and combustion efficiency of weak mixtures is not as good as in the present jet shear layer designs. The authors have extensively investigated various designs of jet shear layer fuelled systems for low emissions wide stability combustor primary zones (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). This work has concentrated on investigating factors that influence mixing, especially the number of air and fuel injection points (13) and the influence of pressure loss (12,14,15,19).…”

“…In the present work the -Jet Mix" design of interacting radial and axial jets was used (10,11,(16)(17)(18)(19)(20). This has been shown to have a good premixed performance (10) with a capability for direct fuel injection with the radial air that extends the stability whilst retaining low NOx emissions (11,(18)(19)(20). Direct gaseous fuel injection was used to enable the influence of mixing on the combustor performance to be evaluated for the same basic aerodynamics as with premixed combustion.…”