DME is the simplest ether primarily produced directly from syn gas
or indirectly by dehydration of methanol. Due to the chemical structure
of DME, the possibility of forming carbonaceous PM and NOx emissions
during combustion is limited [15]. DME combustion does not produce
soot and is considered a clean fuel. Unlike methanol, DME is a gas at ambient
temperature and pressure, so it is stored under pressure as a liquid
similar to liquefied petroleum gas (LPG) and can use the same existing
infrastructure as LPG [16]. The most challenging aspects of a DME engine
relate to its physical properties and not its combustion characteristics.
A DME fuel storage tank must be twice the size of a conventional
diesel fuel tank due to the lower energy density of DME compared
with diesel fuel, in order to achieve an equivalent driving range to
CIDI (Compression-Ignition Direct-Injection) diesel. Modifications to
pumps and fuel injectors are needed due to the 20-fold lower viscosity
of DME compared with diesel [