Combustion properties of Dimethyl Ether
Please refer me to some paper or book if you know any. A graph showing the adiabatic flame temperature vs equivalence ratio would be ideal.


In 2014 it appears that Glaude, Sirjean, Fournet et al. published a paper that gives exactly the data you are looking for.  See Figure 4 from their paper, which I have also included below.



Possibly relevant text from the paper:


  the
  maximum flame temperature is obtained for slightly rich
  mixtures, at an equivalence ratio around 1.05-1.1, because of
  the lower impact of dilution by nitrogen when the amount of
  air decreases. At the strict stoichiometric conditions, the rate
  of the endothermal molecular dissociations is also at its
  maximum which tends to depress the temperature.


Also this next bit:


  The results show that alcohols have flame temperatures
  comparable to those of conventional fuels, contrary to DME
  that develops significantly higher temperatures. This is
  consistent with the respective values of the heating values of
  these fuels and thermochemical equilibrium data. 
  
  I couldn't find anything on google.


I found the paper by Googling dme adiabatic flame temperature.