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The use of fuels with tendencies to reduce carbon dioxide emissions, particularly gaseous fuels, and improve combustion systems is one of the directions for increasing an internal combustion engine’s attractiveness as a power source. This article presents the effects of combining natural gas combustion with a multi-stage combustion system. A two- and three-stage lean charge combustion system was proposed in order to increase the energy system efficiency. In order to achieve this, a single-cylinder test engine was used, with two interchangeably implemented combustion systems. The tests were carried out with two values of the excess air coefficient (λ = 1.3 and λ = 1.5), as well as two different fuel dose values (qo = 0.35 and 0.55 mg/inj), injected into the prechamber at the same indicated mean effective pressure value (IMEP = 6.5 bar) and the same engine speed (n = 1500 rpm). Based on the obtained research results, it was found that the use of a three-stage system limited the maximum combustion pressure and heat release rate due to the increased resistance of flows between the chambers. At the same time, it was found that the increase in the engine’s indicated efficiency took place in a two-stage system, regardless of the excess air coefficient. Changing the dose of fuel fed into the prechamber significantly affects the engine performance (and efficiency) but only in the two-stage combustion system.

This paper provides a review of different contributions dedicated thus far to entropy generation analysis (EGA) in turbulent combustion systems. We account for various parametric studies that include wall boundedness, flow operating conditions, combustion regimes, fuels/alternative fuels and application geometries. Special attention is paid to experimental and numerical modeling works along with selected applications. First, the difficulties of performing comprehensive experiments that may support the understanding of entropy generation phenomena are outlined. Together with practical applications, the lumped approach to calculate the total entropy generation rate is presented. Apart from direct numerical simulation, numerical modeling approaches are described within the continuum formulation in the framework of non-equilibrium thermodynamics. Considering the entropy transport equations in both Reynolds-averaged Navier–Stokes and large eddy simulation modeling, different modeling degrees of the entropy production terms are presented and discussed. Finally, exemplary investigations and validation cases going from generic or/and canonical configurations to practical configurations, such as internal combustion engines, gas turbines and power plants, are reported. Thereby, the areas for future research in the development of EGA for enabling efficient combustion systems are highlighted. Since EGA is known as a promising tool for optimization of combustion systems, this aspect is highlighted in this work.

This study uses AVL FIRE 2020 R1 software for simulation and experimental verification to deeply analyze the impact of combustion chamber geometry and biodiesel on diesel engine performance at different injection timings. The study found that: With the advancement of injection timing, the indicated fuel consumption rate, cylinder pressure and NOx emissions of the two combustion systems increased, while the indicated thermal efficiency, temperature and Soot emissions decreased accordingly; The blending of low calorific value biodiesel will increase the indicated fuel consumption rate of the two combustion systems, but at the same time it can effectively reduce NOx and Soot emissions; The T: Turbocharger, C: Charger air cooling, D: Diesel particle filter (TCD) combustion system improves the utilization rate of cylinder air due to its unique combustion chamber geometry, thereby improving combustion performance. Compared with the Omega combustion system, the indicated thermal efficiency of the TCD combustion system increased by 6.16% to 8.38% and the indicated fuel consumption rate decreased by 5.80% to 7.73% when burning four types of fuel. In addition, the in‐cylinder pressure and temperature increased, and it performed better in reducing Soot emissions. The research results show that the TCD combustion system can effectively improve the combustion and emission performance of diesel engines, provide data support for the development of diesel engine combustion systems and the combustion of oxygen‐containing fuels in plateau environments, and provide an important reference for energy conservation and emission reduction. This paper studies the effects of combustion chamber geometry and biodiesel blending on engine performance at different injection timings. Compared with the Omega combustion system, the TCD combustion system has improved combustion performance and emission performance.

Herein, a diesel engine jet disturbance combustion system was proposed to achieve efficient and clean combustion under heavy load conditions in heavy-duty diesel engines. The key components of the combustion system were designed, and a research platform was constructed. Focusing on the internal combustion conditions of the disturbance chamber and the developmental path of high-speed jets, the design and comprehensive optimization of the jet disturbance combustion system were carried out. Following optimization, the peak internal heat release rate increased from 86 J/deg to 269 J/deg, and the cumulative heat release increased by 112 J, significantly enhancing the energy of the disturbance chamber jet. Then, considering combustion optimization and the heat transfer loss from the piston, it was determined that the optimal configuration for the disturbance chamber jet channel angles was 60 deg inter-channel angle and 10 deg channel incidence angle. This configuration allowed the disturbance chamber jet to precisely disturb the concentrated mixture area in the middle and late stages of combustion. The intervention of the disturbance chamber jet provided sufficient energy for the fuel–air mixing process and complicated the gas flow state in the main combustion chamber. Despite its low-momentum density, the residual mixture in the cylinder maintained a high mixing rate after the end of the fuel injection process. Single-cylinder engine test results showed that a diesel engine using this jet disturbance system and a 180 MPa common rail pressure fuel system achieved 52.12% thermal efficiency.

The development of modern vehicle drives is aimed at reducing fuel consumption (i.e., crude oil) and minimizing the exhaust emission of toxic components. One such development is the implementation of a two-stage combustion system. Such a system initiates ignition in the prechamber, and then the burning mixture flows into the main chamber, where it ignites the lean mixture. The system allows the efficient combustion of lean mixtures, both liquid and gaseous fuels, in the cylinder. This article proposes a solution for internal combustion engines with a cylinder capacity of approx. 500 cm3. The tests were carried out on a single-cylinder engine powered by pure methane supplied through a double, parallel injection system. A wide range of charge ignitability requires the use of an active chamber containing an injector and a spark plug. The tests were carried out at n = 1500 rpm with three load values (indicated mean effective pressure, IMEP): 2, 4 and 6 bar. All of these tests were carried out at a constant value of the center of combustion (CoC), 8 deg CA. This approach resulted in the ignition timing being the control signal for the CoC. As a result of the conducted research, it was found that an increase in the load, which improved the inter-chamber flow, allowed for the combustion of leaner mixtures without increasing the coefficient of variation, CoV(IMEP). The tests achieved a lean mixture combustion with a value of λ = 1.7 and an acceptable level of non-uniformity of the engine operation, CoV(IMEP) < 8%. The engine’s indicated efficiency when using a two-stage system reached a value of about 42% at λ = 1.5 (which is about 8 percentage points more than with a conventional combustion system at λ = 1.0).

In order to deeply absorb the power generation of new energy, coal-fired circulating fluidized bed units are widely required to participate in power grid dispatching. However, the combustion system of the units faces problems such as decreased control performance, strong coupling of controlled signals, and multiple interferences in measurement signals during flexible operation. To this end, this paper proposes a model predictive control (MPC) scheme based on the extended state Kalman filter (ESKF). This scheme optimizes the MPC control framework. The ESKF is used to filter the collected output signals and jointly estimate the state and disturbance quantities in real time, thus promptly establishing a prediction model that reflects the true state of the system. Subsequently, taking the minimum output signal deviation of the main steam pressure and bed temperature and the control signal increment as objectives, a coordinated receding horizon optimization is carried out to obtain the optimal control signal of the control system within each control cycle. Tracking, anti-interference, and robustness experiments were designed to compare the control effects of ESKF-MPC, ID-PI, ID-LADRC, and MPC. The research results show that, when the system parameters had a ±30% perturbation, the adjustment time range of the main steam pressure and bed temperature loops of this method were 770~1600 s and 460~1100 s, respectively, and the ITAE indicator ranges were 0.615 × 105~1.74 × 105 and 3.9 × 106~6.75 × 106, respectively. The overall indicator values were smaller and more concentrated, and the robustness was stronger. In addition, the test results of the actual continuous variable condition process of the unit show that, compared with the PI strategy, after adopting the ESKF-MPC strategy, the overshoot of the main steam pressure loop of the combustion system was small, and the output signal was stable; the fluctuation range of the bed temperature loop was small, and the signal tracking was smooth; the overall control performance of the system was significantly improved.

Combustion a lean air-fuel mixture in a spark ignited (SI) engine is one way to reduce nitrogen oxide (NO x ) emissions that results in an increase of engine efficiency by decreasing a peak combustion temperature. An effective concept to lean mixture combustion can be a two-stage combustion system of stratified burn mixture in the engine with pre-chamber, in which combustion starts in a pre-chamber (1 stage) and, further, the flame jet from a pre-chamber initiate lean mixture combustion in the engine cylinder (2 stage). The paper presents the results of the laboratory research of the SI stationary engine with two-stage combustion system powered by LPG gas. The results were compared to the results of the dual-fuel engine with two-stage combustion system and the conventional engine with one-stage combustion process. Air-fuel mixture stratification method in the test engine, by using two-stage combustion system with pre-chamber, allowed burning of lean mixture with the overall excess air ratio (») up to 2.0, and thus led to lower emissions of nitrogen oxides in the exhaust gases of the engine. The test engine implementing a conventional, single-stage combustion process has allowed a correct burning of air-fuel mixtures of excess air ratio not exceeding 1.5. Of the value λ > 1.5, an increase of coefficient of variation indicated mean effective pressure (COV IMEP ), and it decreased the engine thermal efficiency (ITE), which became virtually impossible to operate. The engine implementing a two-stage combustion process, working with λ = 2.0 allowed to reduce the NO x content in exhaust gases to a level of about 0.02 g/kWh (for gas engine) and 1.15 g/kWh (for dual-fuel engine). These values are significantly less than the values obtained in the conventional engine, which indicated thermal efficiency (34%) characterized by the emission of NO x — 26.25 g/kWh.

In this study, an innovative Low Temperature Combustion (LTC) system named Temperature Controlled Reactivity Compression Ignition (TCRCI) is presented, and a numerical optimization of the hardware and the operating parameters is proposed. The studied combustion system aims to reduce the complexity of the Reaction Controlled Compression Ignition engine (RCCI), replacing the direct injection of high reactivity fuel with a heated injection of low reactivity fuel. The combustion system at the actual state of development is presented, and its characteristics are discussed. Hence, it is clear that the performances are highly limited by the actual diesel-derived hardware, and a dedicated model must be designed to progress in the development of this technology. A Computational Fluid Dynamics (CFD) model suitable for the simulation of this type of combustion is proposed, and it is validated with the available experimental operating conditions. The Particle Swarm Optimization (PSO) algorithm was integrated with the Computational Fluid Dynamic (CFD) software to optimize the engine combustion system by means of computational simulation. The operating condition considered has a relatively high load with a fixed fuel mass and compression ratio. The parameters to optimize are the piston bowl geometry, injection parameters and the boosting pressure. The achieved system configuration is characterized by a wider piston bowl and injection angle, and it is able to increase the net efficiency of 3% and to significantly reduce CO emissions from 0.407 to 0.136 mg.

Two-stroke engines have higher power density than traditional four-stroke engines, and therefore are suitable for engine downsizing. In this work, a four-stroke single-cylinder diesel engine is modified for two-stroke operation, and the combustion system is designed and optimized using a 3D simulation. Three different combustion chamber profiles and injection spray angles are compared to determine an optimized combustion system. The engine test results show that the two-stroke engine equipped with the newly designed combustion system is able to achieve the same effective power output at a much lower speed than the original four-stroke engine, as well as obtain a better indicated thermal efficiency. This indicates that the poppet-valve two-stroke engine could be an effective technical approach for engine downsizing.

Pyrolysis of biomass followed by combustion of pyrolytic vapors to replace fossil fuels is an economic low-carbon solution. However, the polycyclic aromatic hydrocarbons and N-containing species in biomass pyrolysis vapors result in the soot and NO emissions. The flue gas recirculation (FGR) technology, having the potential to reduce the soot and NO emissions, was introduced to the biomass pyrolysis-combustion system. In addition, it was numerically studied by simulating the biomass pyrolysis vapors based co-flow diffusion flames with CO 2 addition. Both the experimental and simulated results showed that the FGR had significant suppression effects on the soot formation. When the FGR ratio (i.e., CO 2 addition ratio) increased from 0% to 15%, the experimental and simulated soot volume fraction respectively decreased by 32% and 21%, which verified the models used in this study. The decrease in OH concentration caused by the CO 2 addition was responsible for the decrease in the decomposition rate of A2 (A2+OH=A2–+H 2 O). Hence, more benzo(ghi)fluoranthene (BGHIF) was generated through A1C 2 H-+A2→BGHIF+H 2 +H, leading to the increase in inception rate. The decrease in benzo(a)pyrene (BAPYR) concentration was the major factor in the decrease in soot condensation rate. Moreover, the decrease in the C 2 H 2 and OH concentrations was responsible for the decrease in the HACA surface growth rate. Furthermore, the simulated results showed that the NO concentration decreased by 0.4% when the content of CO 2 was increased by 1 vol.%. The decrease in OH concentration suppressed the NO formation via decreasing reaction rates of N+OH=NO+H and HNO+OH=NO+H 2 O and enhanced the NO consumption via increasing reaction rate of HO 2 +NO=NO 2 +OH.