Trancriptomic analysis of the venom gland cDNA library of Bungarus flaviceps revealed Kunitz‐type serine protease inhibitor as one of the major venom protein families with three groups A, B, C. One of the group B isoforms named Flavikunin, which lacked an extra cysteine residue involved in disulfide bond formation in β‐bungarotoxin, was synthesized, cloned, and overexpressed in Escherichia coli. To decipher the structure‐function relationship, the P1 residue of Flavikunin, histidine, was mutated to alanine and arginine. Purified wild‐type and mutant Flavikunins were screened against serine proteases‐thrombin, factor Xa, trypsin, chymotrypsin, plasmin, and elastase. The wild‐type and mutant Flavikunin (H∆R) inhibited plasmin with an IC 50 of 0.48 and 0.35 µM, respectively. The in‐silico study showed that P1 residue of wild‐type and mutant (H∆R) Flavikunin interacted with S1′ and S1 site of plasmin, respectively. Thus, histidine at the P1 position was found to be involved in plasmin inhibition with mild anticoagulant activity.
Exhaust system typically experiences vibration during engine operating conditions due to periodic disturbing forces (firing force and inertia force) which are generated from the engine. Natural frequency of the exhaust system gets excited due to the periodic forces causing resonance which often leads to high cycle fatigue (HCF) failure. Turbocharger is a part of exhaust system and it is mounted on the exhaust manifold. The periodic forces are transferred from engine base (Cylinder head and Block) and these forces gets amplified to overhanging components like exhaust system turbocharger. It is an industrywide practice to perform modal analysis to determine the natural frequencies of the system. However, modal analysis cannot predict the intensity with which the system would vibrate. Thus, we need to make some assumptions about the system vibration ‘g’ levels. Based on accuracy of this assumption, we may end up under-designing or over-designing the system. Harmonic analysis enables us to accurately predict the ‘g’ level at turbocharger using experimental cylinder head base excitations. After recording the correlation with experimental data in many cases it was found that this approach further aided in establishing damping constant factor of the exhaust manifold at elevated temperature. This analysis process has been validated with multiple cases as it has turned out to be a potential approach while doing design risk assessments and optimizing the engine vibration validation efforts. The benefit of prediction of exhaust system vibration level allows us to avoid iterative design process in the early stage of product development thus optimizing the design by taking advantage of shifting the natural frequency of exhaust system to lower source excitation (cylinder head). This saves vast amount of simulation lead time. Another benefit of this process is that the prediction of resonance condition of exhaust system through simulation helps us to estimate the fatigue life against the predicted ‘g’ level.
The exhaust manifold is one of the key components of an engine exhaust system. Exhaust manifold simulations are time-consuming as they require modeling of complex thermal loading and multiple non-linearities like friction and plasticity. This proves to be a big constraint for using Multidisciplinary Design Optimization (MDO) for exhaust manifolds as it involves running a large number of models specified by a Design of Experiments (DOE). Also, during the initial phase of design development, it seems reasonable to compromise the accuracy of simulations at the cost of speed for getting correct feedback on design direction. Hence, the main objective of the current work was to a develop simplified analysis process for Thermomechanical Fatigue (TMF) and modal analysis of exhaust manifold. At the concept stage, due to the lack of availability of accurate thermal Boundary Conditions (BCs) and the goal to simplify modeling, thermal BCs are assumed with the help of thermal data history instead of accurate thermal BCs from test cells. Similarly, other aspects such as ‘level of component assembly required’, ‘mechanical loading’, and ‘outputs to be monitored for making design decisions were also investigated to come up with a simplified approach. The proposed approach was quick compared to the conventional one. This approach was implemented on a few heavy-duty and mid-range engine programs to check repeatability. It was observed that the proposed analysis approach provides correct design direction with a significantly reduced computational time of up to 80%. Incorporating the simplified approach for the MDO process has made it more practical and feasible for implementation during the concept design cycle in the early stage of an engine development program.
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