Abstract
Ammonia (NH 3) is recognized as a carbon-free hydrogen-carrier fuel with a high content of hydrogen atoms per unit volume. Recently, ammonia has received increasing attention as a promising alternative fuel for internal combustion engine and gas turbine applications. However, the viability of ammonia fueling fu-ture combustion devices has several barriers to overcome. To overcome the challenge of its low reactivity, it is proposed to blend it with a high-reactivity fuel. In this work, we have investigated the combustion characteristics of ammonia/diethyl ether (NH 3/DEE) blends using a rapid compression machine (RCM) and a constant volume spherical reactor (CVSR). Ignition delay times (IDTs) of NH 3/DEE blends were measured using the RCM over a temperature range of 620 to 942 K, pressures near 20 and 40 bar, equivalence ratios ( phi) of 1 and 0.5, and a range of mole fractions of DEE,.DEE, from 0.05 to 0.2 (DEE/NH 3 = 5 - 20%). Laminar burning velocities of NH 3/DEE premixed flames were measured using the CVSR at 298 K, 1 bar, phi of 0.9 to 1.3, and.DEE from 0.1 to 0.4. Our results indicate that DEE promotes the reactivity of fuel blends resulting in significant shortening of the ignition delay times of ammonia under RCM conditions. IDTs expectedly exhibited strong dependence on pressure and equivalence ratio for a given blend. Laminar burning velocity was found to increase with increasing fraction of DEE. The burnt gas Markstein length increased with equivalence ratio for.DEE = 0.1 as seen in NH 3 -air flames, while the opposite evolution of Markstein length was observed with for 0.1 <.DEE = 0.4, as observed in isooctane-air flames. A detailed chemical kinetics model was assembled to analyze and understand the combustion characteristics of NH 3 /DEE blends. (c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.