function ignite3(gas)
%  IGNITE3   Solves the same ignition problem as 'ignite', except
%  that the volume is held fixed, and function conuv is used
%  instead of reactor.
%

help ignite3

if nargin == 0 | ~isa(gas,'GasMix')
   gas = idealgasmix('gri30.xml');
end

mw = molecularWeights(gas);
nsp = nSpecies(gas);
set(gas,'T',1001.0,'P',oneatm,'X','H2:2,O2:1,N2:4');

y0 = [temperature(gas)
      massFractions(gas)];
tel = [0 0.001];
options = odeset('RelTol',1.e-5,'AbsTol',1.e-12,'Stats','on');
t0 = cputime;
out = ode15s(@conuv,tel,y0,options,gas,mw);
disp(['CPU time = ' num2str(cputime - t0)]);

if nargout == 0
   % plot the temperature and OH mass fractions.
   figure(1);
   plot(out.x,out.y(1,:));
   xlabel('time');
   ylabel('Temperature');
   title(['Final T = ' num2str(out.y(1,end)) ' K']);

   figure(2);
   ioh = speciesIndex(gas,'OH');
   plot(out.x,out.y(1+ioh,:));
   xlabel('time');
   ylabel('Mass Fraction');
   title('OH Mass Fraction');   
   
end