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.

Jet-A Combustion in an Indirect Injection Compression Engine Versus a Direct Injection Compression Engine at Same Load and Speed

2015 ◽  
Author(s):  
Valentin Soloiu ◽  
Tyler Naes ◽  
Martin Muinos
Keyword(s):  
Heat Release ◽  
Combustion Chamber ◽  
Direct Injection ◽  
High Mobility ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Ultra Low Sulfur Diesel ◽  
Indicated Mean Effective Pressure ◽  
Wheeled Vehicles ◽  
And Diffusion

This study compares combustion of Jet-A in an indirect injection (IDI) compression ignition engine and a direct injection (DI) compression ignition engine at the same load and speed. The Jet-A was blended (75Jet-A): 75% Jet-A and 25% Ultra Low Sulfur Diesel # 2 (ULSD) by mass. Both engines had a load of 4.5 bars Indicated Mean Effective Pressure (IMEP) and were run at 2000 RPM. The IDI engine configuration was very similar to that used in High Mobility Multipurpose Wheeled Vehicles (HMMWV). The research showed that combustion pressure in the IDI engine separate combustion chamber was 81 bars versus 71 bars in the main combustion chamber showing high gas-dynamics losses at transfer passages while in the DI engine the peak pressure reached 65 bars. The Apparent Heat Release Rate (AHRR) in the IDI engine has both the premixed and diffusion stage combined while in the DI classical combustion there are visible both the premixed and diffusion burn stages. The results show that in both engines there is a Low Temperature Heat Release (LTHR) region before top dead center (BTDC). The mass averaged instantaneous temperature reached 1750 K in the direct injection engine being the same for both fuels and for the IDI engines reached 1700 K in main combustion chamber and 1950 K in the separate combustion chamber for both fuels. The study showed that there are significant differences in the shape of the AHRR between the engines, nevertheless, the Jet-A has very similar combustion characteristics with ULSD in both combustion systems making a viable option as a substitute fuel to use in High Mobility Multipurpose Wheeled Vehicles (HMMWV).

Thermodynamic Modeling of Single Cylinder Direct Injection Compression Ignition Engine in Simulink

2015 ◽  
Vol 813-814 ◽  
pp. 866-873
Author(s):  
Sindhu Ravichettu ◽  
G. Amba Prasad Rao ◽  
K. Madhu Murthy
Keyword(s):  
Heat Release ◽  
Direct Injection ◽  
Combustion Process ◽  
Combustion Model ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Close Match ◽  
Tuning Parameters ◽  
Crank Angle ◽  
Diesel Cycle

The aim of this research is to develop a mathematical model of a compression ignition engine using cylinder-by-cylinder model approach to predict the performances; indicated work, indicated torque, in-cylinder pressures and temperatures and heat release rates. The method used in the study is based on ideal diesel cycle and is modified by the numerical formulations which affect the performance of the engine. The model consists of a set of tuning parameters such as engine geometries, EGR fractions, boost pressures, injection timings, air/fuel ratio, etc. It is developed in Simulink environment to promote modularity. A single-zone combustion model is developed and implemented for the combustion process which accounts for ignition delay, heat release. Derivations from slider-crank mechanism are involved to compute the instantaneous volume, area and stroke at any given crank angle. The results of the simulation model have been validated with experimental results with a close match between them.

Combustion characteristics and heat release analysis of a direct injection compression ignition engine fuelled with diesel—dimethyl carbonate blends

2003 ◽  
Vol 217 (7) ◽  
pp. 595-605 ◽  
Author(s):  
Z H Huang ◽  
D M Jiang ◽  
K Zeng ◽  
B Liu ◽  
Z L Yang
Keyword(s):  
Heat Release ◽  
Maximum Rate ◽  
Dimethyl Carbonate ◽  
Direct Injection ◽  
Pressure Rise ◽  
Combustion Characteristics ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Increase With Increase ◽  
Combustion Duration

The combustion characteristics and heat release of a direct injection (DI) compression ignition engine fuelled with diesel-dimethyl carbonate blends were investigated on a compression ignition engine. The study showed that the premixed combustion is prolonged and the duration of the diffusive combustion is shortened with increase in the dimethyl carbonate (DMC) addition. For a specific brake mean effective pressure (b.m.e.p.), the maximum cylinder gas pressure, the maximum rate of pressure rise and the maximum rate of heat release increase with increase in the DMC addition at medium and high loads, while they exhibit less variation with the DMC addition at small load. Meanwhile, the maximum gas temperature decreases with increase in the DMC addition. The ignition delay increases while the rapid combustion duration and the total combustion duration show less variation with the DMC addition. The brake specific fuel consumption (b.s.f.c.) increases while the diesel equivalent b.s.f.c. decreases and the thermal efficiency increases with increase in the DMC addition. The CO and smoke decrease with increase in the DMC addition, and NOx does not increase with increase in DMC.

Mapping the combustion modes of a dual-fuel compression ignition engine

2021 ◽  
pp. 146808742110183
Author(s):  
Jonathan Martin ◽  
André Boehman
Keyword(s):  
Direct Injection ◽  
Fuel Combustion ◽  
Dual Fuel ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Combustion Modes ◽  
Si Engines ◽  
Dual Fuel Combustion ◽  
Soot Emissions ◽  
Ci Engines

Compression-ignition (CI) engines can produce higher thermal efficiency (TE) and thus lower carbon dioxide (CO2) emissions than spark-ignition (SI) engines. Unfortunately, the overall fuel economy of CI engine vehicles is limited by their emissions of nitrogen oxides (NOx) and soot, which must be mitigated with costly, resource- and energy-intensive aftertreatment. NOx and soot could also be mitigated by adding premixed gasoline to complement the conventional, non-premixed direct injection (DI) of diesel fuel in CI engines. Several such “dual-fuel” combustion modes have been introduced in recent years, but these modes are usually studied individually at discrete conditions. This paper introduces a mapping system for dual-fuel CI modes that links together several previously studied modes across a continuous two-dimensional diagram. This system includes the conventional diesel combustion (CDC) and conventional dual-fuel (CDF) modes; the well-explored advanced combustion modes of HCCI, RCCI, PCCI, and PPCI; and a previously discovered but relatively unexplored combustion mode that is herein titled “Piston-split Dual-Fuel Combustion” or PDFC. Tests show that dual-fuel CI engines can simultaneously increase TE and lower NOx and/or soot emissions at high loads through the use of Partial HCCI (PHCCI). At low loads, PHCCI is not possible, but either PDFC or RCCI can be used to further improve NOx and/or soot emissions, albeit at slightly lower TE. These results lead to a “partial dual-fuel” multi-mode strategy of PHCCI at high loads and CDC at low loads, linked together by PDFC. Drive cycle simulations show that this strategy, when tuned to balance NOx and soot reductions, can reduce engine-out CO2 emissions by about 1% while reducing NOx and soot by about 20% each with respect to CDC. This increases emissions of unburnt hydrocarbons (UHC), still in a treatable range (2.0 g/kWh) but five times as high as CDC, requiring changes in aftertreatment strategy.

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