Fuel-Lubricant Interactions: Critical Review of Recent Work

A critical review of recent work on fuel lubricant interactions is undertaken. The work focusses on liquid fuels used in diesel and gasoline vehicles. The amount of fuel that contaminates the lubricant depends on driving conditions, engine design, fuel type, and lubricant type. When fuel contaminates a lubricant, the viscosity of the lubricant will change (it will usually decrease), the sump oil level may increase, there may be a tendency for more sludge formation, there may be an impact on friction and wear, and low speed pre-ignition could occur. The increased use of biofuels (particularly biodiesel) may require a reduction in oil drain intervals, and fuel borne additives could contaminate the lubricant. The move towards the active regeneration of particulate filters by delayed fuel post-injection and the move towards hybrid electric vehicles and vehicles equipped with stop-start systems will lead to increased fuel dilution. This will be of more concern in diesel engines, since significant fuel dilution could persist at sump oil temperatures in the range of 100–150 °C (whereas in gasoline engines the more volatile gasoline fuel will have substantially evaporated at these temperatures). It is anticipated that more research into fuel lubricant interactions, particularly for diesel engines, will be needed in the near future.

Research on Influence of Exhaust Characteristics and Control Strategy to DOC-Assisted Active Regeneration of DPF

For the purpose of designing a reasonable control strategy for DOC-assisted DPF regeneration, a mathematical model that describes the thermal phenomenon both in a diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) during regeneration is developed. All boundary conditions of this model are obtained by experiments. The effects of the main exhaust parameters such as exhaust mass flow rate, exhaust temperature, oxygen concentration and emission of reactants are investigated comprehensively. The effects of two main parameters of control strategy, DOC-out temperature and soot loading, are analyzed as well. To quantify the effects of relevant parameters, the fuzzy grey relational analysis method is utilized to evaluate the correlation coefficient of all factors to key indexes of DPF regeneration such as maximum temperature, maximum rate of temperature increase and regeneration duration. The results of this work will greatly reduce the complexity of analysis and enable more rational control strategy design of DOC–DPF regeneration systems.

Fuel-Lubricant Interactions: Critical Review of Recent Work

A critical review of recent work on fuel lubricant interactions is undertaken. The work focusses on liquid fuels used in diesel and gasoline vehicles. The amount of fuel that contaminates the lubricant depends on driving conditions, engine design, fuel type and lubricant type. When fuel contaminates a lubricant, the viscosity of the lubricant will change (it will usually decrease), the sump oil level may increase, there may be a tendency for more sludge formation, there may be an impact on friction and wear, and low speed pre-ignition could occur. The increased use of biofuels (particularly biodiesel) may require a reduction in oil drain intervals, and fuel borne additives could contaminate the lubricant. The move to active regeneration of particulate filters by delayed fuel post-injection and the move to hybrid electric vehicles, and vehicles equipped with stop-start systems will lead to increased fuel dilution. This will be of more concern in diesel engines, since significant fuel dilution could still persist at sump oil temperatures in the range 100-150C (whereas in gasoline engines the more volatile gasoline fuel will have substantially evaporated at these temperatures). It is anticipated that more research into fuel lubricant interactions, particularly for diesel engines, will be needed in the near future.

Carbon-Assisted Bioleaching of Chalcopyrite and Three Chalcopyrite/Enargite-Bearing Complex Concentrates

Overcoming the slow-leaching kinetics of refractory primary copper sulfides is crucial to secure future copper sources. Here, the effect of carbon was investigated as a catalyst for a bioleaching reaction. First, the mechanism of carbon-assisted bioleaching was elucidated using the model chalcopyrite mineral, under specified low-redox potentials, by considering the concept of Enormal. The carbon catalyst effectively controlled the Eh level in bioleaching liquors, which would otherwise exceed its optimal range (0 ≤ Enormal ≤ 1) due to active regeneration of Fe3+ by microbes. Additionally, Enormal of ~0.3 was shown to maximize the carbon-assisted bioleaching of the model chalcopyrite mineral. Secondly, carbon-assisted bioleaching was tested for three types of chalcopyrite/enargite-bearing complex concentrates. A trend was found that the optimal Eh level for a maximum Cu solubilization increases in response to the decreasing chalcopyrite/enargite ratio in the concentrate: When chalcopyrite dominates over enargite, the optimal Eh was found to satisfy 0 ≤ Enormal ≤ 1. As enargite becomes more abundant than chalcopyrite, the optimal Eh for the greatest Cu dissolution was shifted to higher values. Overall, modifying the Eh level by adjusting AC doses to maximize Cu solubilization from the concentrate of complex mineralogy was shown to be useful.

Exhaust valve profile modulation for improved diesel engine curb idle aftertreatment thermal management

Rapid warm-up of a diesel engine aftertreatment system (ATS) is a challenge at low loads. Modulating exhaust manifold pressure (EMP) to increase engine pumping work, fuel consumption, and as a result, engine-outlet temperature, is a commonly used technique for ATS thermal management at low loads. This paper introduces exhaust valve profile modulation as a technique to increase engine-outlet temperature for ATS thermal management, without requiring modulation of exhaust manifold pressure. Experimental steady state results at 800 RPM/1.3 bar BMEP (curb idle) demonstrate that early exhaust valve opening with negative valve overlap (EEVO+NVO) can achieve engine-outlet temperature in excess of 255°C with 5.7% lower fuel consumption, 12% lower engine out NOx and 20% lower engine-out soot than the conventional thermal management strategy. Late exhaust valve opening with internal EGR via reinduction (LEVO+Reinduction) resulted in engine-outlet temperature in excess of 280°C, while meeting emission constraints at no fuel consumption penalty. This work also demonstrates that LEVO in conjunction with modulation of exhaust manifold pressure results in engine-outlet temperature in excess of 340°C while satisfying desired emission constraints. Aggressive use of LEVO can result in engine-outlet temperatures of 460°C, capable of active regeneration of DPF at curb idle, without the significant increase in engine-out soot emissions seen in previously studied strategies.

Intensity and duration of phases of wound healing after surgical intervention in сases of spontaneous periodontitis accompanied by various reactivity of the body

The usage of the principle of optimal management, namely such effects on complicated forms, when the course of the disease is close to that of uncomplicated course of the disease is very promising in drug therapy of patients with generalized periodontitis. The aim is to study the intensity and duration of the phases of wound healing of the mucosa after spontaneous periodontitis surgery accompanied by normo-, hyper- and hyporeactivity of the body by cytological examination of smear-imprints of wound exudate. Materials and methods: The experiments were performed on 24 adult mongrel dogs divided into three equal groups. In the first group, drugs that disrupt the reactivity of the organism were not used (normoreactivity of the organism). In the second group, the animals were simulated a сondition of hyperreactivity, in the third group – the hyporeactivity of the organism. All the animals with spontaneous periodontitis underwent a patchwork surgery. In the period after surgery, cytological examination was performed on the 1st, 4th, 6th and 9th day of the experiment. Results: It has been revealed that in cases of the normal reactivity of the organism the following periods of cellular reactions during the healing of the gums mucous membrane can be differentiated within the appropriate terms: the period of degenerative-inflammatory changes (1st day), active granulocyte-macrophage reaction (4th day), reparations (6th day) and the period of increase of reparative processes with a decrease in the overall cellular response (9th day). Examination of smear-imprints after surgical treatment in animals with spontaneous periodontitis with hyper- and hyporeactivity of the body allowed to identify the same periods of cellular reactions during the healing of the gingival mucosa, as in cases of normoreaction with hyperreation.Tthe intensity and duration of the wound healing phases differed from those which are typical for normoreactivity of the body: granulocyte-macrophage reaction was more pronounced and lasted longer until the 6th day, so later only on the 9th day there were cellular signs of regeneration. With hyporeaction, the intensity and duration of the wound healing phases differed from those which are typical for normoreactivity of the body: granulocyte reaction occurred later (only on the 6th day) and lasted longer, signs of active regeneration appeared later on the 9th day. Therefore, postoperative wound healing in animals with impaired body reactivity was delayed for 3-4 days. Conclusions: Thus, direct medical correction with transforming intensity and duration of the phases of the wound process which are characteristic for impaired reactivity of the body into the phases which are typical for normoreaction is essential. It provides synchronization of necrotic and reparative processes and creates conditions for normal uncomplicated healing of periodontal soft tissues