![Fig. 4. Smoke, THC and NOx emission for DME and diesel from a single cylinder of 638 cm3 DI compression-ignition engine [33].](/figures/fig-4-smoke-thc-and-nox-emission-for-dme-and-diesel-from-a-3d1mwkpr.webp)
![Fig. 3. Fuel consumption (BSFC), NOx and CO2 emissions for DME compared to diesel from a six-cylinder 7 l turbocharged/intercooled heavy-duty diesel engine operating in Japanese D13 mode [18].](/figures/fig-3-fuel-consumption-bsfc-nox-and-co2-emissions-for-dme-1nvlc9dy.webp)
![Table 4 Well-to-wheels energy efficiency and CO2 emissions of light-duty vehicles (LDV) and heavy-duty vehicles (HDV) [1,4]](/figures/table-4-well-to-wheels-energy-efficiency-and-co2-emissions-1ft2fbbh.webp)
![Fig. 2. DME sprays at various conditions compared to diesel sprays [18]; atmospheric (10.1 MPa) and high pressure (3 MPa) ambient conditions with fuel-injection pressures at 25 and 55 MPa.](/figures/fig-2-dme-sprays-at-various-conditions-compared-to-diesel-1azptt3d.webp)
Q2. What was the effect of the auto-ignition kernels on the flame propagation process?
The flame propagation process exhibited oscillatory characteristics where the auto-ignition kernels moved forwards and backwards, due to pressure waves and the cooling effect of the evaporating fuel.
Q3. What is the reason for the large pressure oscillations in the injection line?
A loss of pressure across the valve seat reduces the pressure drop across the nozzle holes which, in turn, reduces the velocity of the injected spray.(iii) Pressure oscillations and residual pressure in the injection line:
Q4. What was the effect of the propane on the DME injection system?
The propane pressurized the DME into a sub-cooled-liquid state and functioned as a driving fluid that pumped the liquid DME from the tank to the injection pump by means of its vapour pressure.
Q5. What is the main advantage of using DME as an alternative fuel?
With the objective of improving both engine thermal efficiency and exhaust emissions, several new engine-design concepts such as low compression ratio DI diesel engines and homogeneous charge compression ignition (HCCI) engines have been investigated using DME as an alternative fuel.
Q6. How many ppm of DME can be included in a spray can?
An odorant such as ethylmercaptane can be included up to 20 ppm.DME has been produced world wide in quantities of 100,000–150,000 tonnes per annum from 1996 or earlier [1,2], and is used as a propellant for spray cans for cosmetics instead of chloro-fluoro-carbons (CFC’s).
Q7. What is the reason why the DME engine has a short ignition delay period?
Teng et al. [11] explained that, because DME has a short ignition delay period, the overrich and over-lean mixture regions formed during the ignition delay period might be smaller, resulting in significantly reduced HC emissions.
Q8. What is the reason for the larger pressure oscillations in the injection line?
After injection, DME exhibits larger pressure oscillations and a higher residual pressure in the injection line between the fuel pump and the injector, compared to diesel fuel [10].
Q9. What is the way to minimize HC and CO emissions?
The interaction between fuel-injection system behaviour and the combustion chamber design should be optimized to minimize HC and CO emissions.
Q10. What is the way to produce DME from fossil sources?
Although it is possible to produce DME from both fossil and renewable sources, bio-DME is very attractive; however, producing DME from fossil sources is the only viable route at present from a cost perspective since bioDME is very expensive relative to diesel fuel.
Q11. What is the key to the development of a dedicated low emission vehicle?
the key to the development of a dedicated lowemissions, DME-fuelled engine is the performance and durability of its fuel-injection system [1,2].
Q12. Why is the adiabatic flame temperature for DME lower than that of diesel fuel?
It was suggested that because the gaseous specific heat capacity of DME is higher than that of diesel fuel, the adiabatic flame temperature for DME is slightly lower than for diesel fuel (represented in this analysis by dodecane).
Q13. How did they measure the injection rate of diesel?
Ikeda et al. [25] calibrated and assessed the accuracy of the injection rate meter with multiple injection rates and quantities, including five-stage injection, and showed that the common-rail injection system was able to realize the required programmed injection accurately.
Q14. Why is the nozzle opening earlier for DME than for diesel fuel?
Thus due to the higher feed pressure of DME in the fuel line, the start of nozzle opening should be earlier for DME than for diesel fuel.
Q15. Why is the nozzle opening earlier for DME than for diesel fuel?
Thus due to the higher feed pressure of DME in the fuel line, the start of nozzle opening should be earlier for DME than for diesel fuel.
Q16. What is the main advantage of using DME as fuel in a direct injection engine?
Kajitani et al. [33] investigated the concept of using DME as fuel in a direct-injection compression-ignition engine with a low compression ratio, in an effort to identify a combustion regime with the highest possible thermal efficiency.
Q17. How much area is required for circulation of a kg of carbon per year?
The carbon flow in the natural cycle can be expressed in terms of the area required for circulation of a kg of carbon per year; for bio-fuels, this area amounts to approximately 7 m2.
Q18. How much area is required for circulation of a kg of carbon per year?
The carbon flow in the natural cycle can be expressed in terms of the area required for circulation of a kg of carbon per year; for bio-fuels, this area amounts to approximately 7 m2.