A Comparison of Valving Strategies Appropriate for Multimode Combustion Within a Downsized Boosted Automotive Engine—Part II: Mid Load Operation Within the SACI Combustion Regime

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Matthew S. Gerow ◽  
Prasad S. Shingne ◽  
Vassilis Triantopoulos ◽  
Stanislav V. Bohac ◽  
Jason B. Martz
Keyword(s):  
Kinematic Model ◽  
Combustion Regime ◽  
Valve Lift ◽  
Automotive Engine ◽  
Thermodynamic Simulations ◽  
Thermodynamic Conditions ◽  
Valve Opening ◽  
Definition Of ◽  
Negative Valve Overlap ◽  
Valve Overlap

Spark assisted compression ignition (SACI) is a combustion mode that may offer significant efficiency improvements compared to conventional spark-ignited combustion systems. Unfortunately, SACI is constrained to a relatively narrow range of dilution levels and top dead center temperatures. Both positive valve overlap (PVO) and negative valve overlap (NVO) strategies may be utilized to attain these conditions at low and intermediate engine loads. The current work compares 1D thermodynamic simulations of PVO valving strategies and a baseline NVO strategy in a downsized boosted automotive engine with variable valve timing capability. As future downsized boosted engines may employ multiple combustion modes, the goal of this work is the definition of valving strategies appropriate for SACI combustion at low to moderate loads and spark ignition (SI) combustion at moderate to high loads for an engine with fixed camshaft profiles. PVO durations, valve opening timings, and peak lifts are investigated at low to moderate loads and are compared to a baseline NVO configuration in order to assess valving strategies appropriate for multimode combustion operation. A valvetrain kinematic model is used to translate the desired valve lift profiles into camshaft profiles while a kinematic analysis is used to calculate piston to valve clearances and to define the practical limits of the PVO strategies. The NVO and PVO strategies are also compared to throttled SI operation at part load to assess the overall efficiency benefit of operating under the thermodynamic conditions of the SACI combustion regime. While the results of this study are engine specific, there are several camshaft profiles that are appropriate for the use of PVO rebreathing type valve events. For the range of PVO valve events examined and taking into consideration piston to valve interference, the use of high exhaust and low intake lifts with early exhaust valve opening timing and long PVO durations enables high levels of internal exhaust gas recirculation (EGR) with relatively low pumping losses.

A Comparison of Valving Strategies Appropriate for Multi-Mode Combustion Within a Downsized Boosted Automotive Engine: Part B — Mid Load Operation Within the SACI Combustion Regime

2013 ◽  
Author(s):  
Matthew S. Gerow ◽  
Prasad S. Shingne ◽  
Vassilis Triantopoulos ◽  
Stanislav V. Bohac ◽  
Jason B. Martz
Keyword(s):  
Kinematic Model ◽  
Combustion Regime ◽  
Valve Lift ◽  
Automotive Engine ◽  
Thermodynamic Conditions ◽  
Valve Opening ◽  
Definition Of ◽  
Negative Valve Overlap ◽  
Valve Overlap ◽  
Multi Mode

Spark Assisted Compression Ignition (SACI) is a combustion mode that may offer significant efficiency improvements compared to conventional spark-ignited combustion systems. Unfortunately, SACI is constrained to a relatively narrow range of dilution levels and top dead center temperatures. Both positive valve overlap (PVO) and negative valve overlap (NVO) strategies may be utilized to attain these conditions at low and intermediate engine loads. The current work compares 1D thermodynamic simulations of PVO valving strategies and a baseline NVO strategy in a downsized boosted automotive engine with variable valve timing capability. As future downsized boosted engines may employ multiple combustion modes, the goal of this work is the definition of valving strategies appropriate for SACI combustion at low to moderate loads and SI combustion at moderate to high loads for an engine with fixed camshaft profiles. PVO durations, valve opening timings and peak lifts are investigated at low to moderate loads and are compared to a baseline NVO configuration in order to assess valving strategies appropriate for multi-mode combustion operation. A valvetrain kinematic model is used to translate the desired valve lift profiles into camshaft profiles, while a kinematic analysis is used to calculate piston to valve clearances and to define the practical limits of the PVO strategies. The NVO and PVO strategies are also compared to throttled SI operation at part load to assess the overall efficiency benefit of operating under the thermodynamic conditions of the SACI combustion regime. While the results of this study are engine specific, there are several camshaft profiles that are appropriate for the use of PVO rebreathing type valve events. For the range of PVO valve events examined and taking into consideration piston to valve interference, the use of high exhaust and low intake lifts with early exhaust valve opening timing and long PVO durations enables high levels of internal EGR with relatively low pumping losses.

scholarly journals Effect of Negative Valve Overlap on Combustion and Emissions of CNG-Fueled HCCI Engine with Hydrogen Addition

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Yuelin Li ◽  
Zihan Zhang ◽  
Zhiqiang Liu ◽  
Peng Tong ◽  
Dezhi Yang ◽  
...  
Keyword(s):  
Combustion Temperature ◽  
Pressure Rise ◽  
Chemical Kinetic ◽  
Nox Emission ◽  
Spontaneous Ignition ◽  
Intake Valve ◽  
Compression Ignition Engine ◽  
Valve Opening ◽  
Negative Valve Overlap ◽  
Valve Overlap

In order to study the effect of negative valve overlap on combustion and emission characteristics of a homogeneous charge compression ignition engine fueled with natural gas and hydrogen, the test and the simulation were conducted using an engine cycle model coupling the chemical kinetic reaction mechanism under different valve timing conditions. Results show that the internal EGR formed by using negative valve overlap could heat the inlet mixtures and improve the spontaneous ignition characteristic of the engine. The residual exhaust gas could slow down the heat release rate, decrease the pressure rise rate and the maximum combustion temperature, and reduce the NOx emission simultaneously. Among the three NVO schemes, the strategy of changing the intake valve opening timing individually can create the least power loss, and the symmetric NVO strategy which changes both the exhaust valve closing timing and the intake valve opening timing simultaneously can achieve the best heating effect of inlet mixtures and the satisfactory decrease of combustion temperature, as well as the largest reduction of NOx emission.

scholarly journals Modeling of Homogeneous Mixture Formation and Combustion in GDI Engine with Negative Valve Overlap

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
M. K. Lalith ◽  
Akshay Dinesh ◽  
S. Unnikrishnan ◽  
Akhil Radhakrishnan ◽  
S. Srihari ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Valve Lift ◽  
Zone Model ◽  
Mixture Formation ◽  
Noticeable Effect ◽  
Engine Model ◽  
Gdi Engine ◽  
Negative Valve Overlap ◽  
Valve Overlap ◽  
Mixture Homogeneity

Mixture homogeneity plays a crucial role in HCCI engine. In the present study, the mixture homogeneity was analysed by three-dimensional engine model. Combustion was studied by zero-dimensional single zone model. The engine parameters studied include speed, injector location, valve lift, and mass of fuel injected. Valve lift and injector location had less impact on mixture formation and combustion phasing compared to other parameters. Engine speed had a noticeable effect on mixture homogeneity and combustion characteristics.

Numerical study on combustion characteristics of six-stroke-cycle gasoline compression ignition engine with continuously variable valve duration valve technology

2019 ◽  
Vol 22 (1) ◽  
pp. 165-183 ◽  
Author(s):  
Oudumbar Rajput ◽  
Youngchul Ra ◽  
Kyoung-Pyo Ha ◽  
You-Sang Son
Keyword(s):  
Numerical Study ◽  
Power Stroke ◽  
Compression Ignition ◽  
Ignition Timing ◽  
Compression Ignition Engine ◽  
Engine Operation ◽  
Wide Range ◽  
Negative Valve Overlap ◽  
Variable Valve ◽  
Valve Overlap

Engine performance and emissions of a six-stroke gasoline compression ignition engine with a wide range of continuously variable valve duration control were numerically investigated at low engine load conditions. For the simulations, an in-house three-dimensional computational fluid dynamics code with high-fidelity physical sub-models was used, and the combustion and emission kinetics were computed using a reduced kinetics mechanism for a 14-component gasoline surrogate fuel. Variation of valve timing and duration was considered under both positive valve overlap and negative valve overlap including the rebreathing of intake valves via continuously variable valve duration control. Close attention was paid to understand the effects of two additional strokes of the engine cycle on the thermal and chemical conditions of charge mixtures that alter ignition, combustion and energy recovery processes. Double injections were found to be necessary to effectively utilize the additional two strokes for the combustion of overly mixed lean charge mixtures during the second power stroke. It was found that combustion phasing in both power strokes is effectively controlled by the intake valve closure timing. Engine operation under negative valve overlap condition tends to advance the ignition timing of the first power stroke but has minimal effect on the ignition timing of second power stroke. Re-breathing was found to be an effective way to control the ignition timing in second power stroke at a slight expense of the combustion efficiency. The operation of a six-stroke gasoline compression ignition engine could be successfully simulated. In addition, the operability range of the six-stroke gasoline compression ignition engine could be substantially extended by employing the continuously variable valve duration technique.

Investigation of Performance and Fuel Economy for Cylinder Deactivation Engine at Part Load Operation

2016 ◽  
Vol 819 ◽  
pp. 443-448 ◽  
Author(s):  
S.F. Zainal Abidin ◽  
Mohd Farid Muhamad Said ◽  
Azhar Abdul Aziz ◽  
Mohd Azman Abas ◽  
N.I. Arishad
Keyword(s):  
Fuel Economy ◽  
Fuel Injection ◽  
Injection Timing ◽  
Original Performance ◽  
Part Load ◽  
Automotive Engine ◽  
Engine Efficiency ◽  
Efficiency Performance ◽  
Valve Opening ◽  
Load Conditions

In automotive engine applications, the spark ignition (SI) engines can operate at various engine speed and load conditions. However, most of the time was spend at part load operations, where they operate below their rated output especially during cruising or idling. The needs of improvement in term of engine efficiency at part load operation become more popular among the engine manufacturers. One of the main reasons for efficiency dropped at part load conditions is the flow restrictions at the throttle valve opening area due to nearly-close position to control amount of inducted air into the cylinder, which leads to increasing in pumping losses. Hence, there are a lot of studies and investigations have been carried out to tackle these problems without sacrificing the original performance. This paper will investigate further the engine efficiency, performance as well as fuel economy by using one-dimensional (1-D) simulation tool. A baseline simulation model of a 1.6 liters four cylinders, port fuel injection engine has been developed based on the actual engine geometries. This baseline model applied predictive combustion to predict the amount of cylinder pressure based on actual ignition and injection timing on bench. The simulated results show a very good agreement with the measured data. Additionally, this study also proved that the deactivation half of the cylinders can significantly reduce the pumping losses of fired cylinder while eliminated the pumping work of unfired cylinders.

Assessment of Residual Mass Estimation Methods for Cylinder Pressure Heat Release Analysis of HCCI Engines With Negative Valve Overlap

2011 ◽  
Author(s):  
Elliott A. Ortiz-Soto ◽  
Jiri Vavra ◽  
Aristotelis Babajimopoulos
Keyword(s):  
Heat Release ◽  
State Equation ◽  
Operating Conditions ◽  
Exhaust Valve ◽  
Estimation Methods ◽  
Cylinder Pressure ◽  
Hcci Engines ◽  
Release Analysis ◽  
Negative Valve Overlap ◽  
Valve Overlap

Increased residual levels in Homogeneous Charge Compression Ignition (HCCI) engines employing valve strategies such as recompression or negative valve overlap (NVO) imply that accurate estimation of residual gas fraction (RGF) is critical for cylinder pressure heat release analysis. The objective of the present work was to evaluate three residual estimation methods and assess their suitability under naturally aspirated and boosted HCCI operating conditions: i) the Simple State Equation method employs the Ideal Gas Law at exhaust valve closing (EVC); ii) the Mirsky method assumes isentropic exhaust process; and iii) the Fitzgerald method models in-cylinder temperature from exhaust valve opening (EVO) to EVC by accounting for heat loss during the exhaust process and uses measured exhaust temperature for calibration. Simulations with a calibrated and validated “virtual engine” were performed for representative HCCI operating conditions of engine speed, fuel-air equivalence ratio, NVO and intake pressure (boosting). The State Equation method always overestimated RGF by more than 10%. The Mirsky method was most robust, with average errors between 3–5%. The Fitzgerald method performed consistently better, ranging from no error to 5%, where increased boosting caused the largest discrepancies. A sensitivity study was also performed and determined that the Mirsky method was most robust to possible pressure and temperature measurement errors.

scholarly journals An applicable approach to mitigate pressure rise rate in an HCCI engine with negative valve overlap

2020 ◽  
Vol 257 ◽  
pp. 114018 ◽  
Author(s):  
Jacek Hunicz ◽  
Maciej Mikulski ◽  
Michal S. Geca ◽  
Arkadiusz Rybak
Keyword(s):  
Pressure Rise ◽  
Pressure Rise Rate ◽  
Hcci Engine ◽  
Rise Rate ◽  
Negative Valve Overlap ◽  
Valve Overlap

Effect of Fuel Injection Timing During Negative Valve Overlap Period on a GDI-HCCI Engine

2018 ◽  
Author(s):  
Sok Ratnak ◽  
Jin Kusaka ◽  
Yasuhiro Daisho ◽  
Kei Yoshimura ◽  
Kenjiro Nakama
Keyword(s):  
Fuel Injection ◽  
Direct Injection ◽  
Single Pulse ◽  
Injection Timing ◽  
Pulse Injection ◽  
Hcci Combustion ◽  
Fuel Injection Timing ◽  
Intake Stroke ◽  
Negative Valve Overlap ◽  
Valve Overlap

Gasoline Direct Injection Homogeneous Charge Compression (GDI-HCCI) combustion is achieved by closing early the exhaust valves for trapping hot residual gases combined with direct fuel injection. The combustion is chemically controlled by multi-point auto-ignition which its main combustion phase can be controlled by direct injection timing of fuel. This work investigates the effect of single pulse injection timing on a supercharged GDI-HCCI combustion engine by using a four-stroke single cylinder engine with a side-mounted direct fuel injector. Injection of primary reference fuel PRF90 under the near-stoichiometric-boosted condition is studied. The fuel is injected during negative valve overlap (NVO) or recompression period for fuel reformation under low oxygen concentration and the injection is retarded to intake stroke for the homogeneous mixture. It is found that the early fuel injection in NVO period advances the combustion phasing compared with the retarded injection in the intake stroke. Noticeable slower combustion rate from intake stroke fuel injection is obtained compared with the NVO injection due to charge cooling effect. Zero-dimensional combustion simulations with multiple chemical reaction mechanisms are simulated to provide chemical understanding from the effect of fuel injection timing on intermediate species generations. The species such as C2H4, C3H6, CH4, and H2 are found to be formed during the NVO injection period from the calculations. The effects of single pulse injection timings on combustion characteristics such pressure rise rate, combustion stability, and emissions are also discussed in this study.

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