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With the increasingly stringent requirements for NOx emission and NH3 leakage in China's diesel engine pollutant emission standards, it is of great practical importance to study the gas velocity uniformity and NH3 distribution uniformity at the front end of Urea-SCR carriers. To study the gas velocity and NH3 distribution at the front end of SCR carrier, a method is proposed to accurately evaluate the velocity uniformity and NH3 distribution uniformity, and the method is written into Star-CCM+ Report Manager to simulate and calculate the uniformity index, and an SCR single-point conversion efficiency test is conducted to verify the accuracy of the method. By comparing the uniformity index calculated by simulation with the experimentally measured conversion efficiency, the results show that the method can accurately evaluate the front-end gas velocity and NH3 distribution uniformity of SCR carriers, and provide a reference for the study of front-end gas velocity and NH3distribution of Urea-SCR carriers for diesel engines. Finally, the above uniformity evaluation method was used to simulate the factors influencing the front-end velocity uniformity of SCR carriers, and the results showed that the lower the exhaust flow rate and the lower the temperature, the better the front-end velocity uniformity of SCR carriers. [ABSTRACT FROM AUTHOR]

In this paper, taking the high-pressure formation brine in the SHB area of the Tarim Basin as an example, the properties of high pressure formation brine and its influence mechanism on waterbased drilling fluid are systematically studied. The research results show that the high-pressure formation brine in this area mainly contains three cations: Na+, K+, and Ca2+, and the anion is mainly Cl-. Moreover, the monovalent cation brine has a great influence on the rheology of the base slurry, and the divalent cation brine has a greater influence on the filtration loss of the base slurry. The effect of the simulated high pressure formation brine on the base slurry rheology is similar to that of monovalent cation brine. The effect of Zeta potential on fluid loss tends to be that of divalent cation brines. In addition, the simulation of high-pressure formation brine on four commonly used water-based drilling fluid treatment agents found that it mainly affects the fluid loss reduction of the experimental slurry; when 20% simulated high-pressure formation brine was used to infiltrate the experimental slurry, the fluid loss increased sharply. Finally, the mechanism of highpressure salt water intrusion into drilling fluid was revealed, which mainly includes two aspects: (1) The damage of the composite salt to the stability of the colloidal particles in the water-based drilling fluid leads to the coalescence and flocculation of the hydrated bentonite particles; (2) The key treatment agent of water-based drilling fluid is ineffective due to salt water intrusion. [ABSTRACT FROM AUTHOR]

In the circumstances that vehicle pollutants emission issues are highlighted all over the world, exhaust after-treatment (EAT) technologies of diesel engines, are critical to achieve effective clarification. This paper focused on the recent development of diesel engine denitration (De-NOx) after-treatment technologies, whilst an overview of the current state and challenges is presented. Ammonia and selective catalytic reduction (SCR) is the most common solution of diesel engine De-NOx for road vehicles. To achieve effective and efficient De-NOx with NH3- SCR, catalysts needs to operate within a wide temperature window while strongly resistant to sulfur dioxide (S02) poisoning and hydrothermal aging, the advanced control strategies of urea injection and uniformity index (UI) ofNH3 also requires optimization. Lean NOx trap (LNT) technology is another DeNOx route, yet sulfur poisoning and thermal aging hindered application. To achieve complete clarification, the influence of integration schemes on DeNOx efficiency also requires consideration, and system management will be a research highlight in the near future. [ABSTRACT FROM AUTHOR]

In order to mitigate current environmental pollution, after-treatment (EAT) technologies were widely applied in vehicle diesel engines. This paper focus on the recent development of particulate matter (PM) removal key EAT technologies, and provide an overview of current state and shortage. At present, diesel particulates filter (DPF) can filtrate almost 99% particulates from exhaust, while the filtration capacity and application scope are confined by filter material properties. DPF regeneration is important for normal operation of engine, researches on combining active and passive methods are necessary to investigate. As a prerequisite of timely regeneration, soot load determination can be realized by sensor methods. Model-based prediction presents huge potential in further promoting estimation accuracy (<5% now), and optimized regeneration strategy can contribute to control total CO2 emission. More accurate prediction methods will be established in the future with the further understanding of the mechanism of soot formation, filtration, and oxidation. Other EAT devices coupled with thermal management, also affects DPF operation and regeneration. To achieve complete clarification, the influence of integration schemes on DPF performance also requires consideration, and system thermal management will be a research highlight in the near future. [ABSTRACT FROM AUTHOR]

With the increasingly stringent environmental standards, higher requirements are put forward for the emission of mechanical engines. Several active control methods of diesel engine optimization and their effects on exhaust emission were studied via engine bench test under medium and low loads (engine speed at 1200RPM, 20% load rate and engine speed at 1400RPM, 30% load rate). Experimental results indicate that injection advance angle and pressure are closely related to exhaust temperature. An optimized late post injection angle can increase the exhaust products temperature by 90°C. Moreover, intake throttle adjustment can also significantly increase the exhaust products temperature by 120 °C (at 20% intake throttle valve opening), accompanied by a reduction in hydrocarbon and CO emissions. Besides, the intake throttle valve opening was found to have a significant effect on the exhaust products temperature. Under medium and low loads conditions, an appropriate late post injection strategy coupled with matched intake throttle valve opening can be considered as a valid approach to increase the exhaust temperature. This study can provide a reliable reference for improving the working efficiency and exhaust emission quality of diesel engine. [ABSTRACT FROM AUTHOR]