Optimization of combustion noise and thermal efficiency in diesel engines over a wide speed and load operational range

2019 ◽  
Vol 21 (4) ◽  
pp. 698-712
Author(s):  
Gen Shibata ◽  
Kohei Yamamoto ◽  
Mikito Saito ◽  
Yuto Inoue ◽  
Yasumasa Amanuma ◽  
...  
Keyword(s):  
Heat Release ◽  
Thermal Efficiency ◽  
Engine Speed ◽  
Combustion Noise ◽  
Injection System ◽  
Injection Timing ◽  
Wide Range ◽  
Optimum Heat ◽  
Operational Range ◽  
Load Conditions

Pre-mixed diesel combustion has the potential of offering high thermal efficiency with low emissions; however, this may result in loud combustion noise because of the high maximum rate of pressure rise. Combustion noise and thermal efficiency work in a trade-off relation, and it has not been possible to achieve high thermal efficiency with low combustion noise, so far. Our laboratory has worked on combustion noise simulations calculated from the heat release history, and it is now possible to calculate a heat release shape for high thermal efficiency with low combustion noise. In this article, the objective of the research is the reduction of combustion noise by multiple fuel injections with high indicated thermal efficiency for a wide range of engine speeds and loads. The engine employed in the simulations and experiments is a supercharged, single-cylinder direct-injection diesel engine, with a high-pressure common rail fuel injection system. The heat release is approximated by Wiebe functions, and the combustion noise and indicated thermal efficiency are calculated in simulations. The engine operational range was divided into 12 conditions, four engine speed conditions each at three engine load conditions, and the optimum heat release shape for low combustion noise with high indicated thermal efficiency was calculated by a genetic-based algorithm method. The parameters for the genetic-based algorithm simulation were the number of injections, each injection timing, the heating value in each heat release, and the combustion period of each injection. The optimum heat release shape is a delta triangle (Δ)-shaped heat release (the heat release increase in the expansion stroke) with a high degree of constant volume for all conditions; however, the optimum number of heat releases and the injection timing are different depending on the engine speed and load conditions. The simulated results were confirmed by engine tests.

scholarly journals Optimization of multiple heat releases in pre-mixed diesel engine combustion for high thermal efficiency and low combustion noise by a genetic-based algorithm method

2018 ◽  
Vol 20 (5) ◽  
pp. 540-554 ◽  
Author(s):  
Gen Shibata ◽  
Hideyuki Ogawa ◽  
Yasumasa Amanuma ◽  
Yuki Okamoto
Keyword(s):  
High Temperature ◽  
Diesel Engine ◽  
Heat Release ◽  
Noise Reduction ◽  
Thermal Efficiency ◽  
Fuel Injection ◽  
Combustion Noise ◽  
Two Stage ◽  
Temperature Heat ◽  
Optimum Heat

The reduction of diesel combustion noise by multiple fuel injections maintaining high indicated thermal efficiency is an object of the research reported in this article. There are two aspects of multiple fuel injection effects on combustion noise reduction. One is the reduction of the maximum rate of pressure rise in each combustion, and the other is the noise reduction effects by the noise canceling spike combustion. The engine employed in the simulations and experiments is a supercharged, single-cylinder direct-injection diesel engine, with a high pressure common rail fuel injection system. Simulations to calculate the combustion noise and indicated thermal efficiency from the approximated heat release by Wiebe functions were developed. In two-stage high temperature heat release combustion, the combustion noise can be reduced; however, the combustion noise in amplification frequencies must be reduced to achieve further combustion noise reduction, and an additional heat release was added ahead of the two-stage high temperature heat release combustion in Test 1. The simulations of the resulting three-stage high temperature heat release combustion were conducted by changing the heating value of the first heat release. In Test 2 where the optimum heat release shape for low combustion noise and high indicated thermal efficiency was investigated and the role of each of the heat releases in the three-stage high temperature heat release combustion was discussed. In Test 3, a genetic-based algorithm method was introduced to avoid the time-consuming loss and great care in preparing the calculations in Test 2, and the optimum heat release shape and frequency characteristics for combustion noise by the genetic-based algorithm method were speedily calculated. The heat release occurs after the top dead center, and the indicated thermal efficiency and overall combustion noise were 50.5% and 86.4 dBA, respectively. Furthermore, the optimum number of fuel injections and heat release shape of multiple fuel injections to achieve lower combustion noise while maintaining the higher indicated thermal efficiency were calculated in Test 4. The results suggest that the constant pressure combustion after the top dead center by multiple fuel injections is the better way to lower combustion noise; however, the excess fuel injected leads to a lower indicated thermal efficiency because the degree of constant volume becomes deteriorates.

Effect of Fuel Injection Timing Relative to Ignition Timing on the Natural-Gas Direct-Injection Combustion

2001 ◽  
Author(s):  
Zuohua Huang ◽  
Seiichi Shiga ◽  
Takamasa Ueda ◽  
Nobuhisa Jingu ◽  
Hisao Nakamura ◽  
...  
Keyword(s):  
Heat Release ◽  
Late Stage ◽  
Equivalence Ratio ◽  
Fuel Injection ◽  
Direct Injection ◽  
Injection Timing ◽  
Ignition Timing ◽  
Fuel Injection Timing ◽  
Initial Stage ◽  
Wide Range

Abstract Effect of fuel injection timing relative to ignition timing on natural gas direct-injection combustion was studied by using a rapid compression machine. The ignition timing was fixed at 80 ms from the compression start. When the injection timing was relatively earlier (injection start at 60 ms), the heat release pattern showed slower burn in the initial stage and faster burn in the late stage, which is similar to that of flame propagation of a premixed gas. In contrast to this, when the injection timing was relatively later (injection start at 75 ms), the heat release rate showed faster burn in the initial stage and slower burn in the late stage, which is similar to that of diesel combustion. The shortest duration was realized at the injection end timing of 80 ms (the same timing as the ignition timing) over the wide range of equivalence ratio. The degree of charge stratification and the intensity of turbulence generated by the fuel jet is considered to cause these behaviors. Earlier injection leads to longer duration of the initial combustion, whereas the later injection does longer duration of the late combustion. Earlier injection showed relatively lower CO emission while later injection produces relatively lower NOx emission. It was suggested that earlier injection leads to lower mixture stratification combustion and later injection leads to higher mixture stratification combustion. Combustion efficiency maintained high value over the wide range of equivalence ratio.

Factors Affecting Performance of Dual Fuel Compression Ignition Engines

2013 ◽  
Vol 388 ◽  
pp. 217-222
Author(s):  
Mohamed Mustafa Ali ◽  
Sabir Mohamed Salih
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Thermal Efficiency ◽  
Fuel Injection ◽  
Direct Injection ◽  
Injection System ◽  
Dual Fuel ◽  
Injection Timing ◽  
Compression Ignition ◽  
Factors Affecting

Compression Ignition Diesel Engine use Diesel as conventional fuel. This has proven to be the most economical source of prime mover in medium and heavy duty loads for both stationary and mobile applications. Performance enhancements have been implemented to optimize fuel consumption and increase thermal efficiency as well as lowering exhaust emissions on these engines. Recently dual fueling of Diesel engines has been found one of the means to achieve these goals. Different types of fuels are tried to displace some of the diesel fuel consumption. This study is made to identify the most favorable conditions for dual fuel mode of operation using Diesel as main fuel and Gasoline as a combustion improver. A single cylinder naturally aspirated air cooled 0.4 liter direct injection diesel engine is used. Diesel is injected by the normal fuel injection system, while Gasoline is carbureted with air using a simple single jet carburetor mounted at the air intake. The engine has been operated at constant speed of 3000 rpm and the load was varied. Different Gasoline to air mixture strengths investigated, and diesel injection timing is also varied. The optimum setting of the engine has been defined which increased the thermal efficiency, reduced the NOx % and HC%.

Effects of N-Butanol Content on the Dual-Fuel Combustion Mode With CNG at Two Engine Speeds

2018 ◽  
Author(s):  
Xiangyu Meng ◽  
Wuqiang Long ◽  
Yihui Zhou ◽  
Mingshu Bi ◽  
Chia-Fon F. Lee
Keyword(s):  
Thermal Efficiency ◽  
Engine Speed ◽  
Direct Injection ◽  
Fuel Combustion ◽  
Dual Fuel ◽  
Combustion Mode ◽  
Start Of Injection ◽  
Wide Range ◽  
Pilot Fuel ◽  
Dual Fuel Combustion

Because of the potential to reduce NOx and PM emissions simultaneously and the utilization of biofuel, diesel/compressed natural gas (CNG) dual-fuel combustion mode with port injection of CNG and direct injection of diesel has been widely studied. While in comparison with conventional diesel combustion mode, the dual-fuel combustion mode generally leads lower thermal efficiency, especially at low and medium load, and higher carbon monoxide (CO) and total hydrocarbons (THC) emissions. In this work, n-butanol was blended with diesel as the pilot fuel to explore the possibility to improve the performance and emissions of dual-fuel combustion mode with CNG. Various pilot fuels of B0 (pure diesel), B10 (90% diesel/10% n-butanol by volume basis), B20 (80% diesel/20% n-butanol) and B30 (70% diesel/30% n-butanol) were compared at the CNG substitution rate of 70% by energy basis under the engine speeds of 1400 and 1800 rpm. The experiments were carried out by sweeping a wide range of pilot fuel start of injection timings based on the same total input energy including pilot fuel and CNG. As n-butanol was added into the pilot fuel, the pilot fuel/CNG/air mixture tends to be more homogeneous. The results showed that for the engine speed of 1400 rpm, pilot fuel with n-butanol addition leads to a slightly lower indicated thermal efficiency (ITE). B30 reveals much lower NOx emission and slightly higher THC emissions. For the engine speed of 1800 rpm, B20 can improve ITE and decrease the NOx and THC emissions simultaneously relative to B0.

Particulate Matter Emission Suppression Strategies in a Turbocharged Gasoline Direct-Injection Engine

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Zhang Ming ◽  
Zhong Jun ◽  
Capelli Stefano ◽  
Lubrano Luigi
Keyword(s):  
Particulate Matter ◽  
Emission Reduction ◽  
Direct Injection ◽  
Injection Pressure ◽  
Particle Emission ◽  
Gasoline Direct Injection ◽  
Injection System ◽  
Dominant Factor ◽  
Injection Timing ◽  
Wide Range

The development process of a down-sized turbocharged gasoline direct-injection (GDI) engine/vehicle was partially introduced with the focus on particulate matter (PM)/particle number (PN) emission reduction. To achieve this goal, the injection system was upgraded to obtain higher injection pressure. Two types of prototype injectors were designed and compared under critical test conditions. Combined numerical and experimental analysis was made to select the right injector in terms of particle emission. With the selected injector, the effect of injection parameters calibration (injection pressure, start of injection (SOI) timing, number of injection pulses, etc.) on PM/PN emission was illustrated. The number of fuel injection pulses, SOI timing, and injection pressure were found playing the leading role in terms of the particle emission suppression. With single-injection strategy, the injection pressure and SOI timing were found to be a dominant factor to reduce particle emission in warm-up condition and cold condition, respectively; a fine combination of injection timing and injection pressure is generally able to decrease up to 50% of PM emission in a wide range of the engine map. While with multiple injection, up to an order of magnitude PM emission reduction can be achieved. Several New European Driving Cycle (NEDC) emission cycles were arranged on a demo vehicle to evaluate the effect of the injection system upgrade and adjusted calibration. This work will provide a guide for the emission control of GDI engines/vehicles fulfilling future emission legislation.

Influence of the Spatial and Temporal Interaction Between Diesel Pilot and Directly Injected Natural Gas Jet on Ignition and Combustion Characteristics

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Georg Fink ◽  
Michael Jud ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Combustion Process ◽  
Optical Observations ◽  
Gas Jet ◽  
Injection Timing ◽  
Ignition And Combustion ◽  
Temporal Interaction ◽  
Operational Range ◽  
The Impact

In this paper, pilot-ignited high pressure dual-fuel combustion of a natural gas jet is investigated on a fundamental basis by applying two separate single-hole injectors to a rapid compression expansion machine (RCEM). A Shadowgraphy system is used for optical observations, and the combustion progress is assessed in terms of heat release rates (HRRs). The experiments focus on the combined influence of injection timing and geometrical jet arrangement on the jet interaction and the impact on the combustion process. In a first step, the operational range for successful pilot self-ignition and transition to natural gas jet combustion is determined, and the restricting phenomena are identified by analyzing the shadowgraph images. Within this range, the combustion process is assessed by evaluation of ignition delays and HRRs. Strong interaction is found to delay or even prohibit pilot ignition, while it facilitates a fast and stable onset of the gas jet combustion. Furthermore, it is shown that the HRR is governed by the time of ignition with respect to the start of natural gas injection—as this parameter defines the level of premixing. Evaluation of the time of gas jet ignition within the operability map can therefore directly link a certain spatial and temporal interaction to the resulting heat release characteristics. It is finally shown that controlling the HRR through injection timing variation is limited for a certain angle between the two jets.

Effects of Pre-Injection on Combustion Characteristics of a Single-Cylinder Diesel Engine

2009 ◽  
Author(s):  
M. Mittal ◽  
G. Zhu ◽  
T. Stuecken ◽  
H. J. Schock
Keyword(s):  
Diesel Engine ◽  
Combustion Process ◽  
Load Condition ◽  
Combustion Characteristics ◽  
Combustion Noise ◽  
Injection Timing ◽  
Single Cylinder ◽  
Multiple Injections ◽  
Main Injection ◽  
Load Conditions

Multiple injections used for diesel engines, especially pre- and post-injections, have the potential to reduce combustion noise and emissions with improved engine performance. This paper outlines the combustion characteristics of a single-cylinder diesel engine with multiple injections. The effects of pre-injection (multi-injection) on combustion characteristics are presented in a single-cylinder diesel engine at different engine speeds and load conditions. A common rail fuel system with a solenoid injector, driven by a peak and hold circuit, is used in this work. This enables us to control the number of injections, fuel injection timing and duration, and the fuel rail pressure that can be used to optimize the engine combustion process (e.g., eliminate engine knock). Mass fraction burned and burn durations are determined by analyzing the measured in-cylinder pressure data. Results are compared with the cases when no pre-injection was used, i.e. only main injection, at the same engine speeds and load conditions. In each study, different cases are considered with the variation in main injection timing. It is found that at full-load condition and lower engine speeds pre-injection is an effective method to alter the engine burn rate and hence to eliminate knock.

Effects of Heat Release Mode on Emissions and Efficiencies of a Compound Diesel Homogeneous Charge Compression Ignition Combustion Engine

2005 ◽  
Vol 128 (2) ◽  
pp. 446-454 ◽  
Author(s):  
Wanhua Su ◽  
Xiaoyu Zhang ◽  
Tiejian Lin ◽  
Yiqiang Pei ◽  
Hua Zhao
Keyword(s):  
Heat Release ◽  
Thermal Efficiency ◽  
Homogeneous Charge Compression Ignition ◽  
Experimental Comparison ◽  
Injection Timing ◽  
Compression Ignition ◽  
Multiple Injection ◽  
Hcci Combustion ◽  
Flexible Mode ◽  
Homogeneous Charge

A compound diesel homogeneous charge compression ignition (HCCI) combustion system has been developed based on the combined combustion strategies of multiple injection strategy and a mixing enhanced combustion chamber design. In this work, a STAR-CD based, multidimensional modeling is conducted to understand and optimize the multiple injection processes. The parameters explored included injection timing, dwell time, and pulse width. Insight generated from this study provides guidelines on designing the multipulse injection rate pattern for optimization of fuel-air mixing. Various heat release modes created by different injection strategies are investigated by experimental comparison of combustion efficiency, heat loss, and thermal efficiency. It is demonstrated that the process of fuel evaporation and mixing are strongly influenced by pulse injection parameters. Through control of the parameters, the stratification and autoignition of the premixed mixture, and the heat release mode can be controlled. The dispersed mode of heat release created only by the compound diesel HCCI combustion is a flexible mode in combustion control. The thermal efficiency with this mode can reach approximately to as high as that of conventional diesel combustion, while the NOx and smoke emissions can be reduced simultaneously and remarkably.

scholarly journals Effect of Premixed Fuel Preparation for Partially Premixed Combustion With a Low Octane Gasoline on a Light-Duty Multicylinder Compression Ignition Engine

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Adam B. Dempsey ◽  
Scott Curran ◽  
Robert Wagner ◽  
William Cannella
Keyword(s):  
High Pressure ◽  
Thermal Efficiency ◽  
Fuel Injection ◽  
Premixed Combustion ◽  
Injection System ◽  
Injection Timing ◽  
Pilot Injection ◽  
Compression Ignition ◽  
Partially Premixed Combustion ◽  
Injection Strategies

Gasoline compression ignition (GCI) concepts with the majority of the fuel being introduced early in the cycle are known as partially premixed combustion (PPC). Previous research on single- and multicylinder engines has shown that PPC has the potential for high thermal efficiency with low NOx and soot emissions. A variety of fuel injection strategies have been proposed in the literature. These injection strategies aim to create a partially stratified charge to simultaneously reduce NOx and soot emissions while maintaining some level of control over the combustion process through the fuel delivery system. The impact of the direct injection (DI) strategy to create a premixed charge of fuel and air has not previously been explored, and its impact on engine efficiency and emissions is not well understood. This paper explores the effect of sweeping the direct injected pilot timing from −91 deg to −324 deg ATDC, which is just after the exhaust valve closes (EVCs) for the engine used in this study. During the sweep, the pilot injection consistently contained 65% of the total fuel (based on command duration ratio), and the main injection timing was adjusted slightly to maintain combustion phasing near top dead center. A modern four cylinder, 1.9 l diesel engine with a variable geometry turbocharger (VGT), high pressure common rail injection system, wide included angle injectors, and variable swirl actuations was used in this study. The pistons were modified to an open bowl configuration suitable for highly premixed combustion modes. The stock diesel injection system was unmodified, and the gasoline fuel was doped with a lubricity additive to protect the high pressure fuel pump and the injectors. The study was conducted at a fixed speed/load condition of 2000 rpm and 4.0 bar brake mean effective pressure (BMEP). The pilot injection timing sweep was conducted at different intake manifold pressures, swirl levels, and fuel injection pressures. The gasoline used in this study has relatively high fuel reactivity with a research octane number of 68. The results of this experimental campaign indicate that the highest brake thermal efficiency (BTE) and lowest emissions are achieved simultaneously with the earliest pilot injection timings (i.e., during the intake stroke).

Mechanism of thermal efficiency improvement in twin shaped semi-premixed diesel combustion

2021 ◽  
pp. 146808742110264
Author(s):  
Kazuki Inaba ◽  
Yanhe Zhang ◽  
Yoshimitsu Kobashi ◽  
Gen Shibata ◽  
Hideyuki Ogawa
Keyword(s):  
Heat Release ◽  
Thermal Efficiency ◽  
Gas Flow ◽  
Fuel Injection ◽  
Premixed Combustion ◽  
Combustion Noise ◽  
Diesel Combustion ◽  
Combustion Mode ◽  
Secondary Stage ◽  
Combustion Phase

Improvements of the thermal efficiency in twin shaped semi-premixed diesel combustion mode with premixed combustion in the primary stage and spray diffusive combustion in the secondary stage with multi-stage fuel injection were investigated with experiments and 3D-CFD analysis. For a better understanding of the advantages of this combustion mode, the results were compared with conventional diesel combustion modes, mainly consisting of diffusive combustion. The semi-premixed mode has a higher thermal efficiency than the conventional mode at both the low and medium load conditions examined here. The heat release in the semi-premixed mode is more concentrated at the top dead center, resulting in a significant reduction in the exhaust loss. The increase in the cooling loss is suppressed to a level similar to the conventional mode. In the conventional mode the rate of heat release becomes more rapid and the combustion noise increases with advances in the combustion phase as the premixed combustion with pilot and pre injections and the diffusive combustion with the main combustion occurs simultaneously. In the semi-premixed mode, the premixed combustion with pilot and primary injections and the diffusive combustion with the secondary injection occurs separately in different phases, maintaining a gentler heat release with advances in the combustion phase. The mechanism of the cooling loss suppression with the semi-premixed mode at low load was investigated with 3D-CFD. In the semi-premixed mode, there is a reduction in the gas flow and quantity of the combustion gas near the piston wall due to the suppression of spray penetration and splitting of the injection, resulting in a smaller heat flux.

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