A study on the effects of compression ratio, engine speed and equivalence ratio on HCCI combustion of DME

2007 ◽  
Author(s):  
Troels Dyhr Pedersen ◽  
Jesper Schramm
Keyword(s):  
Compression Ratio ◽  
Equivalence Ratio ◽  
Engine Speed ◽  
Hcci Combustion

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.

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.

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.

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

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Ida Truedsson ◽  
Martin Tuner ◽  
Bengt Johansson ◽  
William Cannella
Keyword(s):  
Compression Ratio ◽  
Ignition Temperature ◽  
Engine Speed ◽  
Hcci Combustion ◽  
Air Temperatures ◽  
Auto Ignition ◽  
Temperature Heat ◽  
Pressure Trace ◽  
Primary Reference ◽  
Primary Reference Fuels

The current research focuses on creating a homogeneous charge compression ignition (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 the 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 cooperative fuels research (CFR) engine with a 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 deg after top dead center (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 the LTHR from different primary reference fuels (PRFs) was evaluated. The AIT and the amount of LTHR for different combinations of n-heptane, iso-octane, and ethanol were charted.

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.

scholarly journals Turbulent Flame Velocity Model for SI Engine

2011 ◽  
pp. 127-135
Author(s):  
Rashid Ali ◽  
Nafis Ahmad
Keyword(s):  
Compression Ratio ◽  
Equivalence Ratio ◽  
Engine Speed ◽  
Present Model ◽  
Turbulent Flame ◽  
Spark Ignition Engine ◽  
Operating Parameters ◽  
Flame Velocity ◽  
Wide Range ◽  
Good Agreement

A new model for turbulent flame velocity of premixed flame in spark ignition engine for Iso-octane air mixture has been developed and validated for a wide range of engine operating parameters. The model developed is a zero dimensional thermodynamic model. The effects of engine speed (600-1160 rpm), equivalence ratio (0.7-1.1), unburnt mixture temperature (532- 650 Rankine), compression ratio (5-8) and ignition timing (5-30 degree before top dead center) have been studied in detail. The comparison between theoretical and experimental burning velocity has been made for a wide range of engine operating parameters such as compression ratio, angle of spark, equivalence ratio, flame radius, engine speed and unburnt mixture temperature. The flame velocity obtained from the present model is in good agreement with the experimental and theoretical flame velocity of Cakir. The flame velocity computed by the present model is also in good agreement with the flame velocity calculated by Malik model.

scholarly journals Research on Homogeneous Charge Compression Ignition Combustion of Intake Port Exhaust Gas Recirculation Based on Cam Drive Hydraulic Variable Valve Actuation Mechanism

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 438
Author(s):  
Linghai Han ◽  
Jiaquan Duan ◽  
Dingchao Qian ◽  
Yanfeng Gong ◽  
Yaodong Wang ◽  
...  
Keyword(s):  
Engine Speed ◽  
Valve Lift ◽  
Intake Port ◽  
Cyclic Variation ◽  
Response Characteristics ◽  
Variable Valve Actuation ◽  
Hcci Combustion ◽  
Variation Range ◽  
Variable Valve ◽  
Valve Actuation

The thermal efficiency of an efficient gasoline engine is only about 40% and it will produce a large number of harmful products. Curbing harmful emissions and enhancing thermal efficiency have always been the goals pursued and emission regulations are also being tightened gradually. As one of the main consumers of fossil fuels, automobile engines must further reduce fuel consumption and emissions to comply with the concept of low-carbon development, which will also help them compete with electric vehicles. Homogeneous charge compression ignition (HCCI) combustion combined with variable valve actuation (VVA) technology is one of the important ways to improve engine emissions and economy. HCCI combustion based on VVA can only be realized at small and medium loads. The actual application on the entire vehicle needs to be combined with spark ignition (SI) combustion to achieve full working condition coverage. Therefore, HCCI combustion needs fast valve response characteristics; however, the valve lift and timing of the existing VVA mechanisms are mostly controlled separately, resulting in poor valve response. In order to solve this problem, the cam driven hydraulic variable valve actuation (CDH-VVA) mechanism was designed. The valve lift and timing can be adjusted at the same time and the switching of valve lift and timing can be completed in 1~2 cycles. A set of combustion mode switching data is selected to show the response characteristics of the CDH-VVA mechanism. When switching from spark ignition (SI) to HCCI, it switches to HCCI combustion after only one combustion cycle and it switches to stable HCCI combustion after two combustion cycles, which proves the fast response characteristics of the CDH-VVA mechanism. At the same time, the CDH-VVA mechanism can form the intake port exhaust gas recirculation (EGR), as one type of internal EGR. This paper studies the HCCI combustion characteristics of the CDH-VVA mechanism in order to optimize it in the future and enable it to realize more forms of HCCI combustion. At 1000 rpm, if the maximum lift of the exhaust valve (MLEV) is higher than 5.0 mm or lower than 1.5 mm, HCCI combustion cannot operate stably, the range of excess air coefficient (λ) is largest when the MLEV is 4.5 mm, ranging from 1.0~1.5. Then, as the MLEV decreases, the range of λ becomes smaller. When the MLEV drops to 1.5 mm, the range of λ shortens to 1.0~1.3. The maximum value of the MLEV remains the same at the three engine speeds (1000 rpm, 1200 rpm and 1400 rpm), which is 5.0 mm. The minimum value of the MLEV gradually climbs as the engine speed increase, 1000 rpm: 1.5 mm, 1200 rpm: 2.0 mm, 1400 rpm: 3.0 mm. With the increase of engine speed, the range of indicated mean effective pressure (IMEP) gradually declines, 3.53~6.31 bar (1000 rpm), 4.11~6.75 bar (1200 rpm), 5.02~6.09 bar (1400 rpm), which proves that the HCCI combustion loads of the intake port EGR are high and cannot be extended to low loads. The cyclic variation of HCCI combustion basically climbs with the decrease of the MLEV and slightly jumps with the increase of the engine speed. At 1000 rpm, when the MLEV is 5.0 mm, the cyclic variation range is 0.94%~1.5%. As the MLEV drops to 1.5 mm, the cyclic variation range rises to 3.5%~4.5%. Taking the maximum value of the MLEV as an example, the cyclic variation range of 1000 rpm is 0.94%~1.5%, 1200 rpm becomes 1.5%~2.3% and 1400 rpm rises to 2.0%~2.5%.

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