scholarly journals Compression Ratio Effect on Methane HCCI Combustion

1999 ◽  
Vol 121 (3) ◽  
pp. 569-574 ◽  
Author(s):  
S. M. Aceves ◽  
J. R. Smith ◽  
C. K. Westbrook ◽  
W. J. Pitz
Keyword(s):  
Compression Ratio ◽  
Equivalence Ratio ◽  
Recent Experimental Data ◽  
Ignition Process ◽  
Operational Conditions ◽  
Hcci Combustion ◽  
Intake Pressure ◽  
Inlet Manifold ◽  
Compression Ignition Combustion ◽  
Gas Recirculation

We have used the HCT (hydrodynamics, chemistry, and transport) chemical kinetics code to simulate HCCI (homogeneous charge compression ignition) combustion of methane-air mixtures. HCT is applied to explore the ignition timing, burn duration, NOx, production, gross indicated efficiency and gross IMEP of a supercharged engine (3 atm. intake pressure) with 14:1, 16:1 and 18:1 compression ratios at 1200 rpm. HCT has been modified to incorporate the effect of heat transfer and to calculate the temperature that results from mixing the recycled exhaust with the fresh mixture. This study uses a single reaction zone that varies as a function of crank angle. The ignition process is controlled by adjusting the intake equivalence ratio and the residual gas trapping (RGT). RGT is internal exhaust gas recirculation, which recycles both thermal energy and combustion product species. Adjustment of equivalence ratio and RGT is accomplished by varying the timing of the exhaust valve closure in either two-stroke or four-stroke engines. Inlet manifold temperature is held constant at 300 K. Results show that, for each compression ratio, there is a range of operational conditions that show promise of achieving the control necessary to vary power output while keeping indicated efficiency above 50 percent and NOx levels below 100 ppm. HCT results are also compared with a set of recent experimental data for natural gas.

HCCI Combustion and Cyclic Variation for Lean Mixture Operation

2006 ◽  
Author(s):  
C. Liu ◽  
G. A. Karim ◽  
A. Soharabi ◽  
F. Xiao
Keyword(s):  
Carbon Dioxide ◽  
Natural Gas ◽  
Energy Release ◽  
Compression Ratio ◽  
Equivalence Ratio ◽  
Operating Conditions ◽  
Cyclic Variation ◽  
Operational Conditions ◽  
Hcci Combustion ◽  
Combustion Processes

The characteristics of HCCI combustion were investigated experimentally in a variable compression ratio CFR engine when operating on lean mixtures of n-heptane and n-pentane in air. The effects of changes in equivalence ratio, compression ratio, the addition of nitrogen, carbon dioxide, and methane into the intake charge on the cyclic variation in the ignition and the development of the combustion processes were investigated. The limiting conditions that produce ignition in one cycle only among many, repeated ignition in every cycle, and knock were identified. It was found that HCCI combustion and the range of its operating conditions are limited by the extent of non-homogeneity of the intake charge, both in mixture quality and temperature. The optimum values for the addition of nitrogen, carbon dioxide, and natural gas to produce higher indicated work and reduce cyclic variation and the intensity of energy release depend on the intake mixture strength and specific operational conditions.

Residual-effected homogeneous charge compression ignition at a low compression ratio using exhaust reinduction

2003 ◽  
Vol 4 (3) ◽  
pp. 163-177 ◽  
Author(s):  
P. A. Caton ◽  
A. J. Simon ◽  
J. C. Gerdes ◽  
C. F. Edwards
Keyword(s):  
Compression Ratio ◽  
Equivalence Ratio ◽  
Homogeneous Charge Compression Ignition ◽  
Compression Ignition ◽  
Single Digit ◽  
Hcci Combustion ◽  
Actuation System ◽  
Order Of Magnitude ◽  
No Emissions ◽  
Homogeneous Charge

Studies have been conducted to assess the performance of homogeneous charge compression ignition (HCCI) combustion initiated by exhaust reinduction from the previous engine cycle. Reinduction is achieved using a fully flexible electrohydraulic variable-valve actuation system. In this way, HCCI is implemented at low compression ratio without throttling the intake or exhaust, and without preheating the intake charge. By using late exhaust valve closing and late intake valve opening strategies, steady HCCI combustion was achieved over a range of engine conditions. By varying the timing of both valve events, control can be exerted over both work output (load) and combustion phasing. In comparison with throttled spark ignition (SI) operation on the same engine, HCCI achieved 25–55 per cent of the peak SI indicated work, and did so at uniformly higher thermal efficiency. This was accompanied by a two order of magnitude reduction in NO emissions. In fact, single-digit (ppm) NO emissions were realized under many load conditions. In contrast, hydrocarbon emissions proved to be significantly higher in HCCI combustion under almost all conditions. Varying the equivalence ratio showed a wider equivalence ratio tolerance at low loads for HCCI.

Pressure Sensitivity of HCCI Auto-Ignition Temperature for Oxygenated Reference Fuels

2012 ◽  
Author(s):  
Ida Truedsson ◽  
Martin Tuner ◽  
Bengt Johansson ◽  
William Cannella
Keyword(s):  
Compression Ratio ◽  
Ignition Temperature ◽  
Equivalence Ratio ◽  
Engine Speed ◽  
Pressure Sensitivity ◽  
Hcci Combustion ◽  
Air Temperatures ◽  
Auto Ignition ◽  
Temperature Heat ◽  
Pressure Trace

The current research focuses on creating an HCCI fuel index suitable for comparing different fuels for HCCI operation. One way to characterize a fuel is to use the Auto-Ignition Temperature (AIT). The AIT can be extracted from the pressure trace. Another potentially interesting parameter is the amount of Low Temperature Heat Release (LTHR) that is closely connected to the ignition properties of the fuel. The purpose of this study was to map the AIT and amount of LTHR of different oxygenated reference fuels in HCCI combustion at different cylinder pressures. Blends of n-heptane, iso-octane and ethanol were tested in a CFR engine with variable compression ratio. Five different inlet air temperatures ranging from 50°C to 150°C were used to achieve different cylinder pressures and the compression ratio was changed accordingly to keep a constant combustion phasing, CA50, of 3±1° after TDC. The experiments were carried out in lean operation with a constant equivalence ratio of 0.33 and with a constant engine speed of 600 rpm. The amount of ethanol needed to suppress LTHR from different PRFs was evaluated. The AIT and the amount of LTHR for different combinations of n-heptane, iso-octane and ethanol were charted.

Effects of Exhaust Gas Recirculation on Knock Intensity of a Downsized Gasoline Spark Ignition Engine

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Mingzhang Pan ◽  
Haiqiao Wei ◽  
Dengquan Feng
Keyword(s):  
Compression Ratio ◽  
Fuel Injection ◽  
Maximum Amplitude ◽  
Exhaust Gas Recirculation ◽  
Spark Ignition Engine ◽  
Exhaust Gas ◽  
Engine Knock ◽  
Intake Pressure ◽  
Control Port ◽  
Gas Recirculation

Exhaust gas recirculation (EGR) has gained prominence as a significant method to control port fuel injection engine knock caused by high compression ratio and high intake pressure (IP). In this paper, the effect of EGR on knock intensity was investigated under various conditions which included different compression ratios (9:1, 10:1, 11:1), IPs (1.0 bar, 1.2 bar, 1.4 bar) and intake temperatures (ITs, 20 °C, 40 °C, 60 °C). The torque output being a crucial variant was also considered. The results showed that EGR effectively reduced the maximum amplitude of pressure oscillations (MAPO) and knock intensity factor (KI20). The effect of EGR on knock resistance was more significant at higher compression ratio, IP, and IT. The output torque of the engine reached a peak value with a suitable EGR ratio which also controlled the intensity of knock under different conditions.

Simulating the homogeneous charge compression ignition process using a detailed kinetic model for n-heptane mixtures

2000 ◽  
Vol 1 (3) ◽  
pp. 281-289 ◽  
Author(s):  
J Kusaka ◽  
T Yamamoto ◽  
Y Daisho
Keyword(s):  
Compression Ratio ◽  
Homogeneous Charge Compression Ignition ◽  
Combustion Model ◽  
Ignition Process ◽  
Compression Ignition ◽  
Complete Combustion ◽  
Hcci Combustion ◽  
Excess Air ◽  
Auto Ignition ◽  
Homogeneous Charge

The homogeneous charge compression ignition (HCCI) combustion has been attracting growing attention in recent years due to its potential for simultaneous improvement of exhaust gas emissions and fuel consumption in diesel engines. For practical application of HCCI to internal combustion (IC) engines, precise control of auto-ignition of pre-mixtures during the compression stroke is inevitable. This paper discusses the auto-ignition processes in an HCCI engine operated with n-heptane/air mixtures using a zero-dimensional combustion model including a detailed kinetics. The model proposed is validated first by a comparison between calculated and experimental pressure diagrams, and then the effects of initial charge conditions, compression ratio and excess air ratio on ignition and combustion are investigated. It was found from the parametric study that HCCI combustion of n-heptane/air mixtures is classified into three types of combustion: complete combustion, only low-temperature reaction and misfire, depending on the compression ratio and excess air ratio at which the engine is operated. Finally, the major paths of the HCCI reaction occurring in the engine cylinder were clarified by a sensitivity analysis of chemical reactions involved in the HCCI reaction scheme.

Combustion Characteristics of HCCI in Motorcycle Engine

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Yuh-Yih Wu ◽  
Ching-Tzan Jang ◽  
Bo-Liang Chen
Keyword(s):  
Cylinder Head ◽  
Internal Combustion Engines ◽  
Peak Pressure ◽  
Pressure Rise ◽  
Combustion Characteristics ◽  
Hcci Combustion ◽  
Lower Maximum ◽  
Intake Air Heating ◽  
Gas Recirculation ◽  
Motorcycle Engine

Homogeneous charge compression ignition (HCCI) is recognized as an advanced combustion system for internal combustion engines that reduces fuel consumption and exhaust emissions. This work studied a 150 cc air-cooled, four-stroke motorcycle engine employing HCCI combustion. The compression ratio was increased from 10.5 to 12.4 by modifying the cylinder head. Kerosene fuel was used without intake air heating and operated at various excess air ratios (λ), engine speeds, and exhaust gas recirculation (EGR) rates. Combustion characteristics and emissions on the target engine were measured. It was found that keeping the cylinder head temperature at around 120–130°C is important for conducting a stable experiment. Two-stage ignition was observed from the heat release rate curve, which was calculated from cylinder pressure. Higher λ or EGR causes lower peak pressure, lower maximum rate of pressure rise (MRPR), and higher emission of CO. However, EGR is better than λ for decreasing the peak pressure and MRPR without deteriorating the engine output. Advancing the timing of peak pressure causes high peak pressure, and hence increases MRPR. The timing of peak pressure around 10–15 degree of crank angle after top dead center indicates a good appearance for low MRPR.

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