Calculation of Heat Release in Direct Injection Diesel Engines

1999 ◽  
Author(s):  
Michael F. J. Brunt ◽  
Kieron C. Platts
Keyword(s):  
Heat Release ◽  
Diesel Engines ◽  
Direct Injection

Analysis of the effect of variations in fuel line pressure in high-speed direct injection diesel engines, with high-pressure common rail fuel injection systems on heat release, cylinder pressure, performance, and NOx emissions

2005 ◽  
Vol 219 (3) ◽  
pp. 413-422 ◽  
Author(s):  
F J Wallace ◽  
J G Hawley
Keyword(s):  
High Pressure ◽  
Heat Release ◽  
Diesel Engines ◽  
High Speed ◽  
Fuel Injection ◽  
Direct Injection ◽  
Common Rail ◽  
Injection Velocity ◽  
Engine Simulation ◽  
High Pressure Common Rail

This paper is a further development of work previously reported on a wholly analytical approach to heat release modelling and is applicable to high-speed direct injection (HSDI) diesel engines operating with high-pressure common rail fuel injection systems under conditions of predominantly mixing-controlled combustion. The key variable in this treatment is the fuel preparation or combustion rate factor WH which, in conjunction with the primary injection variables, i.e. rail pressure, injection velocity and duration, defines the shape and amplitude of the heat release curve. It was shown in a previous paper that by expressing the fuel preparation rate factor WH as a function of time rather than crank angle, i.e. WHt instead of WHθ, the former can be presented as a nearly linear function of the square of injection velocity, i.e. WHt is directly proportional to the kinetic energy of the injected fuel spray, the latter evidently being the primary influence on the rate of the fuel-air mixing process. The analytical treatment developed in the authors' previous paper then allows heat release rates in the engine, dQ/dθ, to be calculated over a wide range of engine speeds and loads, with the aid of the existing engine simulation code ODES (Otto diesel engine simulation) to predict the associated engine performance and emissions, without resorting to further engine testing.

Computational optimization of a hydrogen direct-injection compression-ignition engine for jet mixing dominated nonpremixed combustion

2021 ◽  
pp. 146808742110535
Author(s):  
Rafig Babayev ◽  
Arne Andersson ◽  
Albert Serra Dalmau ◽  
Hong G Im ◽  
Bengt Johansson
Keyword(s):  
Heat Transfer ◽  
Heat Release ◽  
Diesel Engines ◽  
Direct Injection ◽  
Orifice Diameter ◽  
Compression Ignition ◽  
Optimization Strategy ◽  
Compression Ignition Engine ◽  
Jet Mixing ◽  
Nonpremixed Combustion

Hydrogen (H2) nonpremixed combustion has been showcased as a potentially viable and preferable strategy for direct-injection compression-ignition (DICI) engines for its ability to deliver high heat release rates and low heat transfer losses, in addition to potentially zero CO2 emissions. However, this concept requires a different optimization strategy compared to conventional diesel engines, prioritizing a combustion mode dominated by free turbulent jet mixing. In the present work, this optimization strategy is realized and studied computationally using the CONVERGE CFD solver. It involves adopting wide piston bowl designs with shapes adapted to the H2 jets, altered injector umbrella angle, and an increased number of nozzle orifices with either smaller orifice diameter or reduced injection pressure to maintain constant injector flow rate capacity. This work shows that these modifications are effective at maximizing free-jet mixing, thus enabling more favorable heat release profiles, reducing wall heat transfer by 35%, and improving indicated efficiency by 2.2 percentage points. However, they also caused elevated incomplete combustion losses at low excess air ratios, which may be eliminated by implementing a moderate swirl, small post-injections, and further optimized jet momentum and piston design. Noise emissions with the optimized DICI H2 combustion are shown to be comparable to those from conventional diesel engines. Finally, it is demonstrated that modern engine concepts, such as the double compression-expansion engine, may achieve around 56% brake thermal efficiency with the DICI H2 combustion, which is 1.1 percentage point higher than with diesel fuel. Thus, this work contributes to the knowledge base required for future improvements in H2 engine efficiency.

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