Emissions Reductions in Diesel and Kerosene Flames Using a Novel Fuel Injector

A SPRAY serves as the heart of almost every type of liquidfueled combustion system. Ideally, to promote combustion withmaximumefficiency andminimumharmful emissions, an injector should deliver a fuel spray that rapidly disperses and evaporates to yield a homogeneousmixture of gaseous fuel and air. Characteristics of an ideal injector include good atomization over a wide range of either steady or transient fuel flow rates, unaffected by flow instabilities, low power requirements, scalability, resistant to blockages, and delivery of a fine spray [1,2]. Reviews by McDonell and Samuelsen [3], Razdan [4],Mansour [5], andNakamura et al. [6] deal with fuel sprays optimized for lean combustion. Pressure atomization, air-assist and air-blast atomization, and effervescent atomization [7] are commonly used techniques for a variety of injector applications. In the current study, we are exploring the so-called flow-blurring injector of Ganan-Calvo [8] in a combustion system. As illustrated in Fig. 1, the flow-blurring (FB) concept consists of a liquid nozzle and an orifice plate situated downstream of the nozzle. The nozzle’s wall is tapered at the outlet, and the sharpened edge of the orifice plate is the same diameter as the inner diameter of the nozzle (d). When the axial distance between the nozzle exit and orifice plate (H) is small (i.e., H=d < 0:25), some of the gas flowing into the lateral cylindrical passageway between the nozzle exit and orifice plane is forced upstream a short distance into the nozzle carrying the liquid. The backflow of gas causes vigorous combination of turbulent mixing and effervescing, or the so-called flow-blurring, which results in a spray with very fine droplets. Simmons et al. [9] conducted cold-flow visualization experiments for a range of geometric and flow conditions to demonstrate the high efficiency of the FB injector concept. To the best of our knowledge, the FB injector concept has never been applied to combustion systems. The objective of this study is to experimentally characterize emissions performance of the FB injector in a liquid-fueled combustor operated at atmospheric pressure. Experiments using diesel and kerosene fuels are performed for fixed fuel and total airflow rates, and the atomizing airflow rate is varied. The FB injector performance (NOx and CO emissions) is compared with that of a commercial air-blast (AB) injector. II. Experimental Setup