scholarly journals The effects of boost pressure on stratification and burn duration of gasoline homogeneous charge compression ignition combustion

2018 ◽  
Vol 20 (3) ◽  
pp. 359-377 ◽  
Author(s):  
Prasad S Shingne ◽  
Robert J Middleton ◽  
Claus Borgnakke ◽  
Jason B Martz
Keyword(s):  
Thermal Stratification ◽  
Homogeneous Charge Compression Ignition ◽  
Boost Pressure ◽  
Compression Ignition ◽  
Constant Magnitude ◽  
Computational Fluid Dynamics Simulations ◽  
Intake Pressure ◽  
Dynamics Simulations ◽  
Compression Ignition Combustion ◽  
Homogeneous Charge

This article investigates the effects of intake pressure (boost) on the pre-ignition stratification and burn duration of homogeneous charge compression ignition combustion. Full cycle computational fluid dynamics simulations are performed with gasoline kinetics. An intake pressure sweep is performed while maintaining the same combustion timing and mean composition. The burn duration reduces with increasing boost, even though intake temperature is reduced to hold combustion timing constant. It is shown that the compositional stratification increases with boost whereas thermal stratification decreases. A quasi-dimensional model is employed to assess the effect of compositional stratification, pressure, mean temperature and isolate the effect of thermal stratification on burn duration. The analysis reveals that reducing charge temperature neutralizes the effect of increased boost on reactivity and the shorter burn durations at higher boost are primarily due to the lower thermal stratification. It is shown that higher pressures do not significantly increase the mixing and the lower thermal stratification is due to lower wall heat losses per unit charge mass. A follow-up set of non-reacting simulations with adiabatic walls corroborate this claim by revealing a constant magnitude of thermal stratification across the boost sweep.

scholarly journals A thermodynamic model for homogeneous charge compression ignition combustion with recompression valve events and direct injection: Part I — Adiabatic core ignition model

2016 ◽  
Vol 18 (7) ◽  
pp. 657-676 ◽  
Author(s):  
Prasad S Shingne ◽  
Robert J Middleton ◽  
Dennis N Assanis ◽  
Claus Borgnakke ◽  
Jason B Martz
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Homogeneous Charge Compression Ignition ◽  
Direct Injection ◽  
Operating Conditions ◽  
Compression Ignition ◽  
Auto Ignition ◽  
Dynamics Simulations ◽  
Compression Ignition Combustion ◽  
Homogeneous Charge

This two-part article presents a model for boosted and moderately stratified homogeneous charge compression ignition combustion for use in thermodynamic engine cycle simulations. The model consists of two components: one an ignition model for the prediction of auto-ignition onset and the other an empirical combustion rate model. This article focuses on the development and validation of the homogeneous charge compression ignition model for use under a broad range of operating conditions. Using computational fluid dynamics simulations of the negative valve overlap valve events typical of homogeneous charge compression ignition operation, it is shown that there is no noticeable reaction progress from low-temperature heat release, and that ignition is within the high-temperature regime ( T > 1000 K), starting within the highest temperature cells of the computational fluid dynamics domain. Additional parametric sweeps from the computational fluid dynamics simulations, including sweeps of speed, load, intake manifold pressures and temperature, dilution level and valve and direct injection timings, showed that the assumption of a homogeneous charge (equivalence ratio and residuals) is appropriate for ignition modelling under the conditions studied, considering the strong sensitivity of ignition timing to temperature and its weak compositional dependence. Use of the adiabatic core temperature predicted from the adiabatic core model resulted in temperatures within ±1% of the peak temperatures of the computational fluid dynamics domain near the time of ignition. Thus, the adiabatic core temperature can be used within an auto-ignition integral as a simple and effective method for estimating the onset of homogeneous charge compression ignition auto-ignition. The ignition model is then validated with an experimental 92.6 anti-knock index gasoline-fuelled homogeneous charge compression ignition dataset consisting of 290 data points covering a wide range of operating conditions. The tuned ignition model predictions of [Formula: see text] have a root mean square error of 1.7° crank angle and R2 = 0.63 compared to the experiments.

Effect of engine size, speed, and dilution method on thermal stratification of premixed homogeneous charge compression–ignition engines: A large eddy simulation study

2019 ◽  
Vol 21 (9) ◽  
pp. 1612-1630 ◽  
Author(s):  
Aimilios Sofianopoulos ◽  
Mozhgan Rahimi Boldaji ◽  
Benjamin Lawler ◽  
Sotirios Mamalis ◽  
John E Dec
Keyword(s):  
Heat Transfer ◽  
Thermal Stratification ◽  
Homogeneous Charge Compression Ignition ◽  
Compression Ignition ◽  
Compression Ignition Engines ◽  
Light Duty ◽  
Large Eddy ◽  
Lower Heat ◽  
Compression Ignition Combustion ◽  
Homogeneous Charge

High heat release rates limit the operating range of homogeneous charge compression–ignition engines to low and medium loads. Thermal stratification has been shown to stagger autoignition, lower heat release rates, and extend the operating range of homogeneous charge compression–ignition engines. However, the dependence of naturally occurring thermal stratification on the engine size, speed, and internal residual dilution is not fully understood. A three-dimensional computational fluid dynamics model with large eddy simulations and detailed chemical kinetics was developed using CONVERGE. This model was used to simulate two different engines: (1) a light-duty 2.0 GM Ecotec Engine modified for homogeneous charge compression–ignition combustion in one of the cylinders and (2) a medium-duty Cummins B-series engine modified for homogeneous charge compression–ignition combustion in one of the cylinders. For the light-duty engine, five consecutive modeled cycles were compared with experimental data from 300 consecutive cycles using residual gas dilution at 2000 r/min. For the medium-duty engine, five consecutive modeled cycles were compared with experimental data from 100 consecutive cycles using air dilution with intake heating at 1200 r/min. In the light-duty engine, it was found that incomplete mixing between fresh charge and residual gas increased thermal stratification early in the compression stroke for residual dilution compared to air dilution. Residual stratification at the onset of ignition was small and not directly coupled with thermal stratification. Heat losses to the walls were the dominant source of thermal stratification at the onset of ignition. The reduced oxygen concentration due to residual dilution, increased the temperature requirement for autoignition, which increased heat transfer losses and increased the thermal stratification around top dead center. The thermal stratification before ignition reduced when the engine speed increased because of the lower heat transfer losses. The light-duty engine was found to have larger portion of the fuel energy lost to heat transfer than the medium-duty engine, which resulted in larger thermal stratification before ignition.

The effect of fuel composition and additive packages on deposit properties and homogeneous charge compression ignition combustion

2019 ◽  
Vol 21 (9) ◽  
pp. 1631-1646
Author(s):  
Joshua Lacey ◽  
Karthik Kameshwaran ◽  
Zoran Filipi ◽  
Peter Fuentes-Afflick ◽  
William Cannella
Keyword(s):  
Combustion Chamber ◽  
Homogeneous Charge Compression Ignition ◽  
Fuel Composition ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Single Cylinder ◽  
Compression Ignition Combustion ◽  
Deposit Layer ◽  
Combustion Chamber Deposit ◽  
Homogeneous Charge

Homogeneous charge compression ignition combustion is highly dependent on in-cylinder thermal conditions that are favorable to auto-ignition, and the presence of deposits can dramatically impact the in-cylinder environment. Because fuels available at the pump can differ considerably in composition, and fuel composition and the included additive package directly affect how deposits accumulate in a homogeneous charge compression ignition engine, strategies intended to bring homogeneous charge compression ignition to market must account for this fuel and additive variability. In order to investigate this impact, two oxygenated refinery stream test fuels with two different additives were run in a single cylinder homogeneous charge compression ignition engine. The two fuels had varying chemical composition; one represents a “dirty” fuel with high aromatic content that was intended to simulate a worst-case scenario for deposit growth, while the other represents a California Reformulated Gasoline Blendstock for Oxygenate Blending fuel, which is the primary constituent of pump gasoline at fueling stations across the state of California. The additive packages are typical of technologies that are commercially available to treat engine deposits. Both fuels were run in an experimental, single-cylinder homogeneous charge compression ignition engine in a passive conditioning study, during which the engine was run at steady state over a period of time in order to track changes in the homogeneous charge compression ignition combustion event as deposits accumulated in-cylinder. Both the composition and the additive influenced the structure of the combustion chamber deposit layer, but more importantly, both the rate at which the layer developed and the equilibrium thickness it achieved. The overall thickness of the combustion chamber deposit layer was found to have a significant impact on homogeneous charge compression ignition combustion phasing.

Development and experimental validation of a field programmable gate array–based in-cycle direct water injection control strategy for homogeneous charge compression ignition combustion stability

2019 ◽  
Vol 20 (10) ◽  
pp. 1101-1113 ◽  
Author(s):  
David Gordon ◽  
Christian Wouters ◽  
Maximilian Wick ◽  
Bastian Lehrheuer ◽  
Jakob Andert ◽  
...  
Keyword(s):  
Field Programmable Gate Array ◽  
Homogeneous Charge Compression Ignition ◽  
Water Injection ◽  
Combustion Stability ◽  
Compression Ignition ◽  
Field Programmable ◽  
Gate Array ◽  
Compression Ignition Combustion ◽  
Gas Recirculation ◽  
Homogeneous Charge

Homogeneous charge compression ignition is a part-load combustion method, which can significantly reduce oxides of nitrogen (NO x) emissions compared to current lean-burn spark ignition engines. The challenge with homogeneous charge compression ignition combustion is the high cyclic variation due to the lack of direct ignition control. A fully variable electromagnetic valve train provides the internal exhaust gas recirculation through negative valve overlap which is required to obtain the necessary thermal energy to enable homogeneous charge compression ignition. This also increases the cyclic coupling as residual gas and unburnt fuel is transferred between cycles through exhaust gas recirculation. To improve combustion stability, an experimentally validated feed-forward water injection controller is presented. Utilizing the low latency and rapid calculation rate of a field programmable gate array, a real-time calculation of residual fuel mass is implemented on a prototyping engine controller. Using this field programmable gate array–based calculation, it is possible to calculate the amount of fuel and the required control interaction during an engine cycle. This controller prevents early rapid combustion following a late combustion cycle using direct water injection to cool the cylinder charge and counter the additional thermal energy from any residual fuel that is transferred between cycles. By cooling the trapped cylinder mass, the upcoming combustion phasing can be delayed to the desired setpoint. The controller was tested at several operating points and showed an improvement in the combustion stability as shown by a reduction in the standard deviation of combustion phasing and indicated mean effective pressure.

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