Allan T. Kirkpatrick - Internal Combustion Engines

The above equations are solved in the MATLAB® program CIHeatRelease.mwhich is listed in the Appendix. The inlet conditions , engine geometry, diesel fuel properties, and fuel injector timing are inputs to the program. The program first calculates the ignition delay and the and parameters using Equations ( 2.110) – ( 2.112), then calculates the energy release (J/deg) during the compression and expansion strokes using Equation ( 2.107), starting at bottom dead center = –180 ). The use of the program is detailed in the following example.

A direct injection (DI) diesel engine has a bore and stroke of 165 mm, compression ratio of 18, and operates at 1500 rpm. Its equivalence ratio is 0.7, and residual fraction is 0.05. The inlet manifold temperature and pressure 283 K and 101.3 kPa. The start of injection is −12 , with an injection duration of 15 , and ignition delay of . Plot the apparent energy release, and determine the maximum energy release rate and associated crank angle.

The input parameters to the MATLAB® program CIHeatRelease.mare listed in the printout below.

Compression Ignition heat release Ti = 283; inlet temperature (K) Pi = 1.00; inlet pressure (bar) MWair = 28.97; air molecular mass (kg/kmol air) rc = 15; compression ratio S = 0.165; stroke (m) B = 0.165; bore (m) N = 1500; engine speed (rpm) PHI = 0.7; equivalence ratio F = 0.05; residual fraction FS = 0.06993; stoichiometric fuel‐‐air ratio ao = 45730; fuel available energy (kJ/kg) CN = 40; Cetane number THETAI = -12; start of injection (deg) THETAD = 15; injection duration (deg) ...

The and parameters for this example are as follows: The cylinder volume at bdc is

The mass of air in the cylinder at bdc is

The molar mass of air in the cylinder at bdc is

The injected fuel total energy is

For an ignition delay of 4.14 ,

The energy release during the premixed phase is

and the energy release during the diffusion burn phase is

The diffusion energy release per kmol of air (MJ/ ) is therefore

and the diffusion burn duration is

The energy release profile produced by CIHeatRelease.mfor the above engine parameters is plotted in Figure 2.24. The maximum energy release rate is during the premixed burn with a rate of about 750 J/deg at −5 . Note that most of the energy release for the combustion parameters of this example occurs during the diffusion burn phase, which lasts about 74 .