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Long Liu
Harbin Engineering University,College of Power and Energy Engineering, Nangang district, Harbin, China

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Research article
Published: 09 February 2021 in E3S Web of Conferences
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Multi-injector system is potential to improve thermal efficiency and NOx emission of diesel engine at the same time. In order to optimize the combustion and emission of Marine medium speed diesel engine, the engine combustion with a multi-injector system is simulated and analyzed by CFD software Converge. In this research, two injectors are installed at the side of the cylinder head while the central injector is maintained. Various injection directions of side injectors and injection strategies of multi-injector system are simulated to optimize the fuel spray and combustion. The analysis results show that the spray angle of the side injector plays a key role for effective thermal efficiency improvement, since complex spray jet-jet interaction and spray impingement may deteriorate the combustion if the arrangement of spray angle was not set properly. Once the fuel injection direction has been optimized, the fuel ratio of the three injectors is optimized and improved the effective thermal efficiency with lower NOx emission. The results show that the two side injectors could increase the fuel injection rate into the cylinder, leading to high brake power and consequently increased the thermal efficiency by 1.26% and decreased the NOx emission by 16% for the best optimization.

ACS Style

Dai Liu; Yingzhu Guo; Long Liu; Qian Xia; Yong Gui. Optimization of Marine Medium Speed Diesel Engine Performance based on Multi-Injector System. E3S Web of Conferences 2021, 236, 01026 .

AMA Style

Dai Liu, Yingzhu Guo, Long Liu, Qian Xia, Yong Gui. Optimization of Marine Medium Speed Diesel Engine Performance based on Multi-Injector System. E3S Web of Conferences. 2021; 236 ():01026.

Chicago/Turabian Style

Dai Liu; Yingzhu Guo; Long Liu; Qian Xia; Yong Gui. 2021. "Optimization of Marine Medium Speed Diesel Engine Performance based on Multi-Injector System." E3S Web of Conferences 236, no. : 01026.

Journal article
Published: 20 July 2020 in Applied Sciences
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In diesel engines, fuel mixing is an important process in determining the combustion efficiency and emissions level. One of the measures used to achieve fuel mixing is controlling the nature and behavior of the fuel spray by shaping the injection rate. The mechanism underlying the behavior of the spray with varying injection rates before the start of combustion is not fully understood. Therefore, in this research, the fuel injection rate shape is investigated to assess the spraying and mixing behavior. Diesel sprays with different ambient temperatures and injection pressures are modeled using the CONVERGE-CFD software. The validation is performed based on experimental data from an Engine Combustion Network (ECN). The verified models are then used to analyze the characteristics of the diesel spray before and after the end-of-injection (EOI) with four fuel injection rate shapes, including a rectangular injection rate shape (RECT), a quick increase gradual decrease injection rate shape (QIGD), a gradual increase gradual decrease injection rate shape (GIGD), and a gradual increase quick decrease injection rate shape (GIQD). The spray vapor penetrations, liquid lengths, evaporation ratios, Sauter mean diameter (SMDs), distributions of turbulence kinetic energy, temperatures, and equivalence ratios were compared under different injection rate shapes. The results show that the QIGD injection rate shape can enhance mixing during injection, while the GIQD injection rate shape can achieve better mixing after the EOI.

ACS Style

Intarat Naruemon; Long Liu; Dai Liu; Xiuzhen Ma; Keiya Nishida. An Analysis on the Effects of the Fuel Injection Rate Shape of the Diesel Spray Mixing Process Using a Numerical Simulation. Applied Sciences 2020, 10, 4983 .

AMA Style

Intarat Naruemon, Long Liu, Dai Liu, Xiuzhen Ma, Keiya Nishida. An Analysis on the Effects of the Fuel Injection Rate Shape of the Diesel Spray Mixing Process Using a Numerical Simulation. Applied Sciences. 2020; 10 (14):4983.

Chicago/Turabian Style

Intarat Naruemon; Long Liu; Dai Liu; Xiuzhen Ma; Keiya Nishida. 2020. "An Analysis on the Effects of the Fuel Injection Rate Shape of the Diesel Spray Mixing Process Using a Numerical Simulation." Applied Sciences 10, no. 14: 4983.

Journal article
Published: 05 November 2019 in Energies
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Common rail systems have been widely used in diesel engines due to the stricter emission regulations. The advances in injector technology and ultrahigh injection pressure greatly promote the development of multiple-injection strategy, leading to the shorter injection duration and more variable injection rate shape, which makes the mixing process more significant for the formation of pollutant emission. In order to study the mixing process of diesel sprays under variable injection rate shapes and find the optimized injection strategy, a one-dimensional spray model was modified in this paper. The model was validated by the measured spray penetrations based on shadowgraphy experiments with the varying injection rate. The simulations were performed with five injection rate shapes, triangle, ramping-up, ramping-down, rectangle and trapezoid. Their spray penetrations, entrainment rates and equivalence ratios along spray axial distance are compared. The potentials of multiple-injection and gas-jet after end-of-injection (EOI) to improve mixing process and emission reduction are discussed finally. The results indicated that ramping-up injection rate obtains the highest entrainment rate after EOI, and it needs 1.5 times of injection duration for the entrainment wave to arrive at the spray tip. For the other four injection rates, the sprays can be treated as a steady-like state, needing twice of injection duration from EOI to the time the entrainment wave reaches the spray tip. The multiple-injection with proper injection rate shape enhanced the entrainment rate, and the gas-jet after EOI affected the mixture distribution and entrainment rate in spray tail under ramping-down injection rate.

ACS Style

Intarat Naruemon; Long Liu; Qihao Mei; Xiuzhen Ma. Investigation on an Injection Strategy Optimization for Diesel Engines Using a One-Dimensional Spray Model. Energies 2019, 12, 4221 .

AMA Style

Intarat Naruemon, Long Liu, Qihao Mei, Xiuzhen Ma. Investigation on an Injection Strategy Optimization for Diesel Engines Using a One-Dimensional Spray Model. Energies. 2019; 12 (21):4221.

Chicago/Turabian Style

Intarat Naruemon; Long Liu; Qihao Mei; Xiuzhen Ma. 2019. "Investigation on an Injection Strategy Optimization for Diesel Engines Using a One-Dimensional Spray Model." Energies 12, no. 21: 4221.

Journal article
Published: 07 May 2019 in Applied Sciences
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Pilot injection combined with exhaust gas recirculation (EGR) is usually utilized to realize the partially premixed compression ignition (PPCI) mode in diesel engines, which enables the simultaneous decrease of nitrogen oxide and soot emissions to satisfy emission regulations. Moreover, the ignition delay of main injection combustion can also be shortened by pilot injection, and then combustion noise is reduced. Nevertheless, the mechanisms of pilot injection impacts on combustion noise are not completely understood. As such, it is hard to optimize pilot injection parameters to minimize combustion noise. Therefore, experiments were conducted on a four-stroke single-cylinder diesel engine with different pilot injection strategies and 20% EGR as part of an investigation into this relationship. Firstly, the combustion noise was analyzed by cylinder pressure levels (CPLs). Then, the stationary wavelet transforms (SWTs) and stationary wavelet packet transform (SWPT) were employed to decompose in-cylinder pressures at different scales, and thus the combustion noise generated by pilot and main combustion was investigated in both the time and frequency domain. The results show that pilot injection is dominant in the high frequency segment of combustion noise, and main injection has a major impact on combustion noise in the low and mid frequency segment. Finally, the effects of various pilot injection parameters on suppressing combustion noise were analyzed in detail.

ACS Style

Jingtao Du; Ximing Chen; Long Liu; Dai Liu; Xiuzhen Ma. Mechanism of Combustion Noise Influenced by Pilot Injection in PPCI Diesel Engines. Applied Sciences 2019, 9, 1875 .

AMA Style

Jingtao Du, Ximing Chen, Long Liu, Dai Liu, Xiuzhen Ma. Mechanism of Combustion Noise Influenced by Pilot Injection in PPCI Diesel Engines. Applied Sciences. 2019; 9 (9):1875.

Chicago/Turabian Style

Jingtao Du; Ximing Chen; Long Liu; Dai Liu; Xiuzhen Ma. 2019. "Mechanism of Combustion Noise Influenced by Pilot Injection in PPCI Diesel Engines." Applied Sciences 9, no. 9: 1875.

Journal article
Published: 08 November 2018 in IFAC-PapersOnLine
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In this paper, a chattering-free sliding mode control law is constructed for the diesel engine air path system with consideration of partial loss of actuator effectiveness and additive fault. Firstly, sliding mode method and adaptive technique are employed to develop a fault-tolerant controller. With the adaptation update law, there is no requirement of the priori knowledge of the upper bounds of the actuator faults. Then, to attenuate the chattering behavior and improve system performance, the boundary layer is introduced to modify the sliding mode control method. Rigorous theoretical analysis is presented based on Lyapunov stability theory, which demonstrates that the system trajectories converge to a small neighborhood around the origin. Finally, numerical simulation results are carried out to show the effectiveness and validness of the proposed algorithms.

ACS Style

Jian Zhang; Long Liu; Xuemin Li; Wenhui Li. Chattering-Free Sliding Mode Control for Diesel Engine Air Path System with Actuator Faults. IFAC-PapersOnLine 2018, 51, 429 -434.

AMA Style

Jian Zhang, Long Liu, Xuemin Li, Wenhui Li. Chattering-Free Sliding Mode Control for Diesel Engine Air Path System with Actuator Faults. IFAC-PapersOnLine. 2018; 51 (31):429-434.

Chicago/Turabian Style

Jian Zhang; Long Liu; Xuemin Li; Wenhui Li. 2018. "Chattering-Free Sliding Mode Control for Diesel Engine Air Path System with Actuator Faults." IFAC-PapersOnLine 51, no. 31: 429-434.

Research article
Published: 15 October 2018 in Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering
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Accurate and quick prediction of spray characteristics such as spray penetration is paramount for the understanding and quantitative analysis of the combustion process in diesel engines, in order to perform parametric study on advanced combustion process in diesel engines, zero-dimensional diesel spray model is often used for the prediction of the spray evolution. In this study, a previous zero-dimensional diesel spray model applied for the spray penetration prediction including the part after the end of injection with a constant injection rate was extended to the cases with varying injection rate. The effective injection velocity was introduced into the previous spray model, which is defined as the ratio of the momentum flux and fuel mass flow rate over the spray tip cross-sectional area. Combined with this definition, the analysis of effective injection rate and its response time was performed during and after the end of injection. After that, the fuel mass flow rate and momentum flux over the spray tip cross-sectional area were derived for varying injection rate even after the end of injection based on the momentum and fuel mass conservation along the spray axis, and further the spray penetration. Finally, the developed model was validated by comparing with the experimental data.

ACS Style

Long Liu; Yan Peng; Xiuzhen Ma; Naoto Horibe; Takuji Ishiyama. Phenomenological modeling of diesel spray with varying injection profile. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 2018, 233, 2780 -2790.

AMA Style

Long Liu, Yan Peng, Xiuzhen Ma, Naoto Horibe, Takuji Ishiyama. Phenomenological modeling of diesel spray with varying injection profile. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering. 2018; 233 (11):2780-2790.

Chicago/Turabian Style

Long Liu; Yan Peng; Xiuzhen Ma; Naoto Horibe; Takuji Ishiyama. 2018. "Phenomenological modeling of diesel spray with varying injection profile." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, no. 11: 2780-2790.

Journal article
Published: 25 April 2017 in Applied Sciences
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We present a single-longitudinal-mode Ho:Sc2SiO5 (Ho:SSO) laser pumped by a Tm:YAP laser for the first time. Two intra-cavity Fabry–Perot etalons were used to realize the single-longitudinal mode of operation. The maximum output power of 590 mW at 2111.91 nm was obtained with the incident power of 10.2 W, when the slope efficiency was 9.7% and the optical conversion efficiency was 5.8%. The M2 factor of the single longitudinal mode Ho:SSO laser was measured to be 1.17.

ACS Style

Xiao-Tao Yang; Long Liu; Peng Zhang; Wen-Qiang Xie. A Resonantly Pumped Single-Longitudinal Mode Ho:Sc2SiO5 Laser with Two Fabry–Perot Etalons. Applied Sciences 2017, 7, 434 .

AMA Style

Xiao-Tao Yang, Long Liu, Peng Zhang, Wen-Qiang Xie. A Resonantly Pumped Single-Longitudinal Mode Ho:Sc2SiO5 Laser with Two Fabry–Perot Etalons. Applied Sciences. 2017; 7 (5):434.

Chicago/Turabian Style

Xiao-Tao Yang; Long Liu; Peng Zhang; Wen-Qiang Xie. 2017. "A Resonantly Pumped Single-Longitudinal Mode Ho:Sc2SiO5 Laser with Two Fabry–Perot Etalons." Applied Sciences 7, no. 5: 434.

Book chapter
Published: 05 October 2016 in Developments in Combustion Technology
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Phenomenological Modeling of Combustion Process in Diesel Engines Based on Stochastic Method | InTechOpen, Published on: 2016-10-05. Authors: Long Liu

ACS Style

Long Liu. Phenomenological Modeling of Combustion Process in Diesel Engines Based on Stochastic Method. Developments in Combustion Technology 2016, 1 .

AMA Style

Long Liu. Phenomenological Modeling of Combustion Process in Diesel Engines Based on Stochastic Method. Developments in Combustion Technology. 2016; ():1.

Chicago/Turabian Style

Long Liu. 2016. "Phenomenological Modeling of Combustion Process in Diesel Engines Based on Stochastic Method." Developments in Combustion Technology , no. : 1.