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Among many technical routes in solving the SCR (Selective Catalyst Reduction) deposition problem, a good mixer design can greatly improve the NO x conversion efficiency of the exhaust after-treatment system while avoiding urea deposition failures. This paper presents an anti-deposition mixer with novel conception which was optimized through CFD method, the more layers of wire mesh plates, the lower the evaporation efficiency is affected by the increase in injection volume. The new mixer with three layers of wire mesh plate shows better deposition resistance performance below 250℃through urea deposits boundary experiment, and it reduces the NO x emission value by 9.5% than conventional scheme under WHTC (Word Harmonized Transient Cycle) and WHSC (Word Harmonized Steady-state Cycle) test. By using the new mixer scheme in the after-treatment system, the problem of deposition under a variety of low emission temperature can be solved. • A new conception mixer make SCR system avoiding from urea deposition. • The new mixer scheme improve the engine emission limit of NO x by 9.5%. • The new mixer has excellent urea deposition resistance performance below 250 ℃. [ABSTRACT FROM AUTHOR]

In the lubrication analysis of piston ring-cylinder liner components for a diesel engine, it is usually assumed that the oil is Newton fluid. But in practice, the lubricant is not always in line with the law of viscosity, that is to say that the lubricant can characterize some non-Newtonian effect. In this paper, a power law fluid was taken as an example to establish the non-Newtonian liquid lubrication model of piston ring-cylinder liner components for a diesel engine. The model was solved by a MATLAB program simultaneously with the load equation. It was found by the results that when considering the non-Newtonian effect of lubricating oil, oil film pressure was different when the power law coefficient was different, but the distribution and the change trend of the oil film pressure was similar; and the highest oil film pressure appeared at a similar position However, the value of the oil film pressure increased with the increase of the power law coefficient, that is, the greater the power law coefficient, the greater was the oil film bearing capacity. The power law coefficient had little effect on the maximum oil film pressure. [ABSTRACT FROM AUTHOR]

In this paper, flexible multi-body dynamics was coupled with elastohydrodynamic lubrication of main bearings to study the lubricating properties of diesel engine main bearings. Data of bearing forces for diesel engine main bearings under rated conditions and cylinder 1 misfired conditions were analyzed, to provide a basis for the tribology design of a main bearing friction pair and the system optimization of a diesel engine. The result showed that single cylinder misfire had a greater influence on the two adjacent main bearing loads and the axis orbits of the two adjacent main bearings, but less effect on the other main bearing load and axis orbits of the other main bearings. [ABSTRACT FROM AUTHOR]

The majority of previous technical solutions improved the exhaust ATS's anti-deposits by innovating the nozzle's spray atomization performance or optimizing the mixing chamber's structural design. These methods are difficult to meet product development needs due to the escalation of emission laws and harsh operating conditions. This paper proposes a deposits control method based on the deposits boundary of the ATS structure. The engine bench test was used to test the deposition of the ATS at four different rotational speeds with exhaust flow rate, temperature, and urea injection volumes. The test results were plotted as a deposits boundary map to form three deposition risk regions: high, medium and low. The middle line of the medium risk region was used as the deposits control strategy value, which is used for the urea injection of the entire ATS. Under WHTC cycle and WHSC cycle conditions, urea consumption with deposits boundary control strategy was reduced by 11.2% and 15.3%, respectively, compared to the consumption without deposits boundary control strategy. Based on this deposits boundary, the engine can evaluate the quantity of urea injection under each working situation within the deposits risk range, allowing it to achieve emission regulations and avoid ATS deposits failures. The deposits problem of SCR mixing chamber in exhaust after-treatment system has been a difficult problem in diesel engine industry, which has been mostly dealt with by increasing the starting injection temperature of urea solution and optimizing the calibration control method for a long time. In this paper, a new method to avoid deposition of urea is proposed, using which the deposits boundary characteristics of the mixer are measured (Fig. 1) and used to control the upper limit of the urea injection volume, which has been proven effective in engineering practice to solve deposition failures in exhaust aftertreatment systems. Figure1. Urea deposition control method based on deposits boundary. [Display omitted] • Urea injection strategy with deposits control line can greatly reduce the deposits risk. • Deposits boundary control method can improve the emission efficiency by more than 10%. • Deposits boundary control method can significantly reduce urea consumption. [ABSTRACT FROM AUTHOR]

• A modified heavy-duty diesel engine with all six cylinders operating in HCII mode. • Gasoline ratio, exhaust gas recirculation ratio and start of injection are studied. • Performance over the whole engine map is showed. • DOC is used to solve the problem of ultra high HC and CO emissions. This paper is focused on the characteristics and performance of HCII in conditions close to practical engine operating. For this purpose, extensive experiments have been conducted on a modified six-cylinder heavy-duty diesel engine, with six-cylinder HCII, high pressure exhaust gas recirculation(EGR) loop and appropriate pressure rise rate. The experiments mainly include two aspects. Firstly, gasoline ratio(GR), EGR ratio and start of injection(SOI), are studied to summarize the combustion and emission characteristics of HCII. Secondly, European steady state cycle(ESC) test is conducted to evaluate HCII performance over the whole engine map. Results suggest that large GR is beneficial to effective thermal efficiency(ETE) or/and nitrogen oxide(NO x) and smoke emissions, however, it is limited by maximum pressure rise rate at low load and uncontrollable ignition time at high load. Similarly, the application of EGR can improve gasoline combustion and decrease NO x emission, while it cannot be too much because of decreased ETE at low load and uncontrollable ignition time at high load. Meanwhile, SOI can be advanced to 40 crank angle degree(CAD) before top dead center(BTDC) to achieve extremely low NO x and smoke emissions and relatively high ETE. However, this strategy can only be applied to B25 and C25 points. Finally, great success is achieved by HCII in ESC test. Just with diesel oxidation catalyst(DOC), the weighted specific emissions of NO x , particulate matter(PM), hydrocarbon(HC) and carbon monoxide(CO) can be 1.841 g/(kW·h), 0.024 g/(kW·h), 0.115 g/(kW·h) and 0.896 g/(kW·h) respectively. [ABSTRACT FROM AUTHOR]

The assembly consistency of a diesel engine will affect its nitrogen oxides (NOx) emission variation. In order to improve the NOx emissions of diesel engines, a study was carried out based on the assembly tolerance variation of the diesel engine's combustion system. Firstly, a diesel engine which meets the Euro VI standards together with the experimental data is obtained. The mesh model and combustion model of the engine combustion system are built in the Converge software (version 2.4, Tecplot, Bellevue, DC, USA), and the experimental data is used to calibrate the combustion model obtained in the Converge software. Then, the four-factor and three-level orthogonal simulation experiments are carried out on the dimension parameters that include nozzle extension height, throat diameter, shrinkage diameter and combustion chamber depth. Through mathematical analysis on the experimental data, the results show that the variation of nozzle extension height and combustion chamber depth have a strong influence on NOx emission results, and the variation of combustion chamber diameter also has a weak influence on NOx production. According to the regression model obtained from the analysis, there is a quadratic function relating the nozzle extension height and NOx emissions and the amount of NOx increases with increasing nozzle extension height. The relationship between emission performance and size parameters is complex. In the selected size range, the influence of the variation of the chamber diameter on NOx is linear. The variation of the chamber depth also has an effect on NOx production, and the simulation results vary with the change of assembly tolerance variation. Thus, in the engine assembly process, it is necessary to strictly control the nozzle extension height and combustion chamber depth. The research results are useful to improve the NOx emission of diesel engine and provide a basis for the control strategy of selective catalytic reduction (SCR) devices. [ABSTRACT FROM AUTHOR]