An anti-crystallization design of selective catalytic reduction nozzle holder

From the aspect of reducing the risk of crystallization on nozzle surface, a new design of nozzle protective cover was to solve the problem in selective catalytic reduction (SCR) urea injection system. The simulation calculation and experimental verification methods were used to compare different schemes. The results show that reducing the height of nozzle holder can reduce the vortex currents near nozzle surface and effectively reduce the risk of crystallization on the nozzle surface. It is proposed to install a protective cover in the nozzle holder under the scheme of reducing the height of nozzle holder, which can further eliminate the vortex. Simulation and test results demonstrate good agreement under the rated running condition. The scheme of adding a protective cover in the nozzle holder shows the least crystallization risk by computational fluid dynamics (CFD) method. The crystallization cycle test shows that, after the height of nozzle holder is reduced, the risk of crystallization on the nozzle surface is reduced correspondingly. The addition of a protective cover in the nozzle holder solves the problem of crystallization on the nozzle surface, which provides a new method for anti-crystallization design.

Dynamic Modeling and Operation Characteristics Analysis of LiBr Absorption Heat Pump

In order to fully exploit the dynamic operation characteristics of absorption heat pump, a dynamic simulation model of LiBr absorption heat pump considering mass transfer and distribution parameters is established. The thermal inertia characteristics of the system are studied, and the thermal performance and crystallization characteristics of the system are analyzed under the conditions of heat source temperature change, cooling water temperature change and refrigerant water temperature change. The results show that: the model can accurately simulate the steady-state and dynamic characteristics of the absorption heat pump; the thermal inertia of the unit is mainly related to the mass of the solution stored in the unit; the upper limit of the heat source inlet temperature is affected by the COP of the system and the crystallization risk, the decrease of the inlet temperature of cooling water can increase the COP of the system, and the lower limit is limited by the crystallization risk, and the cooling water inlet temperature is affected by the crystallization risk , and the lower limit of the inlet temperature of cooling water is limited by the crystallization characteristics. The upper limit of the inlet temperature of refrigerant water is not limited by the crystallization characteristics, but is mainly limited by the user’s energy demand. This provides a reference for the dynamic operation of absorption heat pump.

Application Study on a New Hybrid Canning Structure of After-Treatment System for Diesel Engine

Based on the airflow rotation concept, a new packaging structure was designed to meet the performance requirements of China-VI stage emission regulations. The new structure is a hybrid structure of spiral space with small blades and conical plates. The Computational Fluid Dynamics (CFD) simulation was used to analyze the velocity uniformity and ammonia uniformity of the flow field, and the results showed that velocity uniformity and ammonia uniformity were higher than 0.95, and the possibility of crystallization risk was very low. The actual performance of the new structural prototype was verified by means of engine bench testing. The test results were excellent and the conversion efficiency reached 0.96. The new selective catalytic reduction (SCR) urea mixed structure design greatly improved the conversion efficiency of the after-treatment system and has excellent anti-crystallization performance.

Association of Adherence to The Mediterranean Diet with Urinary Factors Favoring Renal Lithiasis: Cross-Sectional Study of Overweight Individuals with Metabolic Syndrome

Our purpose was to study the relationship of adherence to the Mediterranean diet (MedDiet) with urinary factors that favor the formation of renal calcium and uric acid stones in overweight and obese participants who had metabolic syndrome. This cross-sectional study examined 267 participants. A well-known MedDiet score (range 0–9) was calculated for each patient, and patients were then categorized has having low (≤3), medium (4–5), or high (≥6) adherence to the MedDiet. Baseline characteristics and urinary parameters were also analyzed. High calcium salt urinary crystallization risk (CaUCR) and high uric acid urinary crystallization risk (UrUCR) were calculated from urinary parameters using pre-defined criteria. More than half of patients with MedDiet scores ≤3 had high UrUCR (55.4%) and high CaUCR (53.8%). In contrast, fewer patients with high adherence (≥6) to the MedDiet had high UrUCR (41.2%) and high CaUCR (29.4%). Relative to those with low adherence, individuals with high adherence had a prevalence ratio (PR) of 0.77 for a high UrUCR (95% CI: 0.46–1.12; p for trend: 0.069) and a PR of 0.51 for a high CaUCR (95% CI: 0.26–0.87; p for trend: 0.012) after adjusting for age, sex, body mass index, type 2 diabetes, and total energy intake. Our findings indicate that greater adherence to the MedDiet was associated with a reduced CaUCR and a reduced UrUCR. This suggests that adequate dietary management using the MedDiet patterns may prevent or reduce the incidence and recurrence of calcium salt and uric acid renal stones.

The influence of the injection frequency on the urea selective catalytic reduction systems performance

This study presents the influence of the UWS injection frequency on a close coupled SCR systems performance. The investigation was performed with the CFD tool AVL Fire. In the paper the analysis of four different UWS injection frequencies in the three different operating points of diesel engine was shown. The assessments of the system performance was referred to the ammonia distribution at catalyst intake and wall film formation inside the investigated geometry, as these are considered as crucial in such a configuration. The results showed that injection frequency affects both factors on different level depending from the flow conditions. In addition, the wall film crystallization risk was discussed basing on the obtained wall film characteristics.