Diesel Engine Valve Clearance Fault Diagnosis Based on Features Extraction Techniques and FastICA-SVM

Numerous vibration-based techniques are rarely used in diesel engines fault diagnosis in a direct way, due to the surface vibration signals of diesel engines with the complex non-stationary and nonlinear time-varying fea- tures. To investigate the fault diagnosis of diesel engines, fractal correlation dimension, wavelet energy and entropy as features reflecting the diesel engine fault fractal and energy characteristics are extracted from the decomposed signals through analyzing vibration acceleration signals derived from the cylinder head in seven different states of valve train. An intelligent fault detector FastICA-SVM is applied for diesel engine fault diagnosis and classification. The results demonstrate that FastlCA-SVM achieves higher classification accuracy and makes better general- ization performance in small samples recognition. Besides, the fractal correlation dimension and wavelet energy and entropy as the special features of diesel engine vibration signal are considered as input vectors of classifier FastlCA- SVM and could produce the excellent classification results. The proposed methodology improves the accuracy of fea- ture extraction and the fault diagnosis of diesel engines.

Fault Diagnosis of Valve Clearance in Diesel Engine Based on BP Neural Network and Support Vector Machine

Based on wavelet packet transformation(WPT), genetic algorithm(GA), back propagation neural network(BPNN)and support vector machine(SVM), a fault diagnosis method of diesel engine valve clearance is presented. With power spectral density analysis, the characteristic frequency related to the engine running conditions can be extracted from vibration signals. The biggest singular values(BSV)of wavelet coefficients and root mean square(RMS)values of vibration in characteristic frequency sub-bands are extracted at the end of third level decomposition of vibration signals, and they are used as input vectors of BPNN or SVM. To avoid being trapped in local minima, GA is adopted. The normal and fault vibration signals measured in different valve clearance conditions are analyzed. BPNN, GA back propagation neural network(GA-BPNN), SVM and GA-SVM are applied to the training and testing for the extraction of different features, and the classification accuracies and training time are compared to determine the optimum fault classifier and feature selection. Experimental results demonstrate that the proposed features and classification algorithms give classification accuracy of 100%.

Semi-empirical modeling of volumetric efficiency in engines equipped with variable valve timing system

Volumetric efficiency and air charge estimation is one of the most demanding tasks in control of today's internal combustion engines.Specifically,using three-way catalytic converter involves strict control of the air/fuel ratio around the stoichiometric point and hence requires an accurate model for air charge estimation.However,high degrees of complexity and nonlinearity of the gas flow in the internal combustion engine make air charge estimation a challenging task.This is more obvious in engines with variable valve timing systems in which gas flow is more complex and depends on more functional variables.This results in models that are either quite empirical(such as look-up tables),not having interpretability and extrapolation capability,or physically based models which are not appropriate for onboard applications.Solving these problems,a novel semi-empirical model was proposed in this work which only needed engine speed,load,and valves timings for volumetric efficiency prediction.The accuracy and generalizability of the model is shown by its test on numerical and experimental data from three distinct engines.Normalized test errors are 0.0316,0.0152 and 0.24 for the three engines,respectively.Also the performance and complexity of the model were compared with neural networks as typical black box models.While the complexity of the model is less than half of the complexity of neural networks,and its computational cost is approximately 0.12 of that of neural networks and its prediction capability in the considered case studies is usually more.These results show the superiority of the proposed model over conventional black box models such as neural networks in terms of accuracy,generalizability and computational cost.

Application of Decellularized Scaffold Combined with Loaded Nanoparticles for Heart Valve Tissue Engineering in vitro

The purpose of this study was to fabricate decelluarized valve scaffold modified with polyethylene glycol nanoparticles loaded with transforming growth factor-β1（TGF-β1）,by which to improve the extracellular matrix microenvironment for heart valve tissue engineering in vitro.Polyethylene glycol nanoparticles were obtained by an emulsion-crosslinking method,and their morphology was observed under a scanning electron microscope.Decelluarized valve scaffolds,prepared by using trypsinase and TritonX-100,were modified with nanoparticles by carbodiimide,and then TGF-β1 was loaded into them by adsorption.The TGF-β1 delivery of the fabricated scaffold was measured by asing enzyme-linked immunosorbent assay.Whether unseeded or reseeded with myofibroblast from rats,the morphologic,biochemical and biomechanical characteristics of hybrid scaffolds were tested and compared with decelluarized scaffolds under the same conditions.The enzyme-linked immunosorbent assay revealed a typical delivery of nanoparticles.The morphologic observations and biological data analysis indicated that fabricated scaffolds possessed advantageous biocompatibility and biomechanical property beyond decelluarized scaffolds.Altogether this study proved that it was feasible to fabricate the hybrid scaffold and effective to improve extracellular matrix microenvironment,which is beneficial for an application in heart valve tissue engineering.

Trilayer anisotropic structure versus randomly oriented structure in heart valve leaflet tissue engineering

It has been hypothesized that leaflet substrates with a trilayer structure and anisotropicmechanical properties could be useful for the production of functional and long-lasting tissue-engineered leaflets.To investigate the influence of the anisotropic structural and mechanical characteristics of a substrate on cells,in this study,we electrospun trilayer anisotropic fibrous substrates and randomly oriented isotropic fibrous substrates(used as controls)from polycaprolactone polymers.Consequently,the random substrates had higher radial and lower circumferential tensile properties than the trilayer substrates;however,they had similar flexural properties.Porcine valvular interstitial cells cultured on both substrates produced random and trilayer cell-cultured constructs,respectively.The trilayer cell-cultured constructs had more anisotropic mechanical properties,17%higher cellular proliferation,14%more extracellular matrix(i.e.,collagen and glycosaminoglycan)production,and superior gene and protein expression,suggesting that more cells were in a growth state in the trilayer constructs than in the random constructs.Furthermore,the random and radial layers of the trilayer constructs had more vimentin,collagen,transforming growth factor-beta 1(TGF-ß1),transforming growth factor-beta 3(TGF-ß3)gene expression than in the circumferential layer of the constructs.This study verifies that the differences in structural,tensile,and anisotropic properties of the trilayer and random substrates influence the characteristics of the cells and ECM in the constructs.

Modeling the Effect of Variable Timing of the Exhaust Valves on SI Engine Emissions for Greener Vehicles

The problem with fixed valve timing that the valve train is set by the automaker for peak efficiency running at a specific point in the engine’s operating range. When the vehicle is moving slower or faster than this ideal operating point the engine’s combustion cycle fails to properly burn the air/fuel mixture leading to considerably compromised engine performance and wastes fuel. Variable Valve Timing (VVT) is a solution developed to overcome this engine deficiency, dynamically altering the valve's opening and closing for optimal performance at any speed. The intension in this work is to contribute towards pursuing the development of variable valve timing (VVT) for improving the engine performance. This investigation covers the effect of exhaust valve opening (EVO), and closing (EVC) angle on engine performance and emissions. The aim is to optimize engine power and brake specific fuel consumption (BSFC) where the effect of engine speed has also been considered. Power, BMEP, BSFC, NO, and CO were calculated and presented to show the effect of varying valve timing on them for all the valve timing cases. The calculations of engine performance were carried out using the simulation and analysis engineering software: LOTUS”, and engine emissions were calculated using “ZINOX” program. Sensitivity analysis shows that the reduction of 10% of (EVO) angle gave a reduction of around 2.5% in power and volumetric efficiency, also a slight increase in nitrogen oxide (NO) and carbon monoxide (CO), while a 10% decrease in (EVC) causes around 1% improvement in Power. The effects of different (VVT) from the simulations are analyzed and compared with those in the reviewed literature.

WEAR AND SEALING CHARACTERISTICS OF ENGINE VALVE GUIDE

A novel powder metallurgy （P/M） material with high wear resistance is developed in order to decrease the wear and lubricant-leakage of a diesel engine valve guide. The friction and wear tests of this material are conducted. It indicates that the wear resistance of the newly developed P/M material has been improved and much better than that of the formerly used alloy steel. Moreover, three different sealing structures are designed and theoretically analyzed with respect to the characteristic of hydrodynamic sealing. Through comparative experiments of component leakage and engine run-in for different valve guide structures, it proves that the structure with a machined sealing groove but not installed with a seal-ring cannot only reduce the specific lubricant consumption （SLC） of cylinder head, but also decrease the wear of valve stern and valve guide.

DYNAMIC MODEL AND SIMULATION OF A NOVEL ELECTRO-HYDRAULIC FULLY VARIABLE VALVE SYSTEM FOR FOUR-STROKE AUTOMOTIVE ENGINES

In modem four-stroke engine technology, variable valve timing and lift control offers potential benefits for making a high-performance engine. A novel electro-hydraulic fully variable valve train for four-stroke automotive engines is introduced. The construction of the nonlinear mathematic model of the valve train system and its dynamic analysis are also presented. Experimental and simulation results show that the novel electro-hydraulic valve train can achieve fully variable valve timing and lift control. Consequently the engine performance on different loads and speeds will be significantly increased. The technology also permits the elimination of the traditional throttle valve in the gasoline engines and increases engine design flexibility.

Miller Cycle with Early Intake Valve Closing in Marine Medium-Speed Diesel Engines

In this study,a one-dimensional simulation was performed to evaluate the performance of in-cylinder combustion to control NO_(x) emissions on a four-stroke,six-cylinder marine medium-speed diesel engine.Reducing the combustion temperature is an important in-cylinder measure to decrease NO_(x) emissions of marine diesel engines.The Miller cycle is an effective method used to reduce the maximum combustion temperature in a cylinder and accordingly decrease NO_(x) emissions.Therefore,the authors of this study designed seven different early intake valve closing(EIVC)Miller cycles for the original engine,and analyzed the cycle effects on combustions and emissions in high-load conditions.The results indicate that the temperature in the cylinder was significantly reduced,whereas fuel consumption was almost unchanged.When the IVC was properly advanced,the ignition delay period increased and the premixed combustion accelerated,but the in-cylinder average pressure,temperature and NO_(x) emissions in the cylinder were lower than the original engine.However,closing the intake valve too early led to high fuel consumption.In addition,the NO_(x) emissions,in-cylinder temperature,and heat release rate remarkably increased.Therefore,the optimal timing of the EIVC varied with different loads.The higher the load was,the earlier the best advance angle appeared.Therefore,the Miller cycle is an effective method for in-engine NO_(x) purification and does not entail significant cost.

Development of Biofunctionalized Cellulose Acetate Nanoscaffolds for Heart Valve Tissue Engineering

Currently-used mechanical and biological heart valve prostheses have a satisfactory short-term performance, but may exhibit several major drawbacks on the long-term. Mechanical prostheses, based on carbon, metallic and polymeric components, require permanent anticoagulation treatment, and their usage often leads to adverse reactions, e.g. thromboembolic complications and endocarditis. In recent years, there is a need for a heart valve prosthesis that can grow, repair and remodel. The concept of tissue engineering offers good prospects into the development of such a device. An ideal scaffold should mimic the structural and purposeful profile of materials found in the natural extracellular matrix (ECM) architecture. The goal of this study was to develop cellulose acetate scaffolds (CA) for valve tissue regeneration. After their thorough physicochemical and biological characterization, a biofunctionalization process was made to increase the cell proliferation. Especially, the surface of scaffolds was amplified with functional molecules, such as RGD peptides (Arg-Gly-Asp) and YIGSRG laminins (Tyrosine-Isoleucine-Glycine-Serine-Arginine-Glycine) which immobilized through biotin-streptavidin bond, the strongest non-covalent bond in nature. Last step was to successfully coat an aortic metallic valve with CA biofunctionallized nanoscaffolds and cultivate cells in order to create an anatomical structure comparable to the native valve. Promising results have been obtained with CA-based nanoscaffolds. We found that cells grown successfully on the biofunctionalized valve surface thereby scaffolds that resemble the native tissues, elaborated with bioactive factors such as RGD peptides and laminins not only make the valve’s surface biocompatible but also they could promote endothyliazation of cardiac valves causing an anti-coagulant effect

Development of Valve Steel for Internal Combustion Engine in China

This paper first briefly introduces the history of the development of China valve steel from mainly adopting valve steel from the former Soviet Uinoin in the fifties, manufacturing by herself in the sixties, to introducing advanced valve steel from other countries and instituting Chinese valve steel system since the seventies.The demand of valve steel for China internal combustion engine including material specification and quantity required at present is discussed. The principal difficulties being faced with in the development of China valve steel at the moment are put forward. Finally, a detailed discussion is made on the development of China valve steel with suggstions of developing 5Cr8Si2 and MF811 martensitic steels, 21 2N austenitic steel used for gasoline engine, 23 8N austenitic steel used for diesel engine, 21 4NWNb high strength austenitic steel and LF2 and LF4 for valve alloy.[WT5”BZ〗

Fabrication of a Novel Hybrid Scaffold for Tissue Engineered Heart Valve

The aim of this study was to fabricate biomatrix/polymer hybrid scaffolds using an electrospinning technique. Then tissue engineered heart valves were engineered by seeding mesenchymal stromal cells （MSCs） onto the scaffolds. The effects of the hybrid scaffolds on the proliferation of seed cells, formation of extracellular matrix and mechanical properties of tissue engineered heart valves were investigated. MSCs were obtained from rats. Porcine aortic heart valves were decellularized, coated with poly（3-hydroxybutyrate-co-4-hydroxybutyrate） using an electrospinning technique, and reseeded and cultured over a time period of 14 days. In control group, the decellularized valve scaffolds were reseeded and cultured over an equivalent time period. Specimens of each group were examined histologically （hematoxylin-eosin [HE] staining, immunohistostaining, and scanning electron microscopy）, biochemically （DNA and 4-hydroxyproline） and mechanically. The results showed that recellularization was comparable to the specimens of hybrid scaffolds and controls. The specimens of hybrid scaffolds and controls revealed comparable amounts of cell mass and 4-hydroxyproline （P〉0.05）. However, the specimens of hybrid scaffolds showed a significant increase in mechanical strength, compared to the controls （P〈0.05）. This study demonstrated the superiority of the hybrid scaffolds to increase the mechanical strength of tissue engineered heart valves. And compared to the decellularized valve scaffolds, the hybrid scaffolds showed similar effects on the proliferation of MSCs and formation of extracellular matrix. It was believed that the hybrid scaffolds could be used for the construction of tissue engineered heart valves.

Oxidization resistance of Ni76Cr19AlTi valve alloy at temperatures under operating mode of heavy-duty engines

The oxidization resistance of the Ni76Cr19A1Ti alloy was studied by a static oxidization experiment at 600-800℃. The results show that the oxidation behavior of the alloy can be explained by a kinetic equation： （△m/S）2 = Kpt ＋ C, where Kp is a kinetic constant of the nickel-base alloy. The higher the experimental temperature, the higher the value of Kp. It is discovered that the microstructure of the oxide scales is compact and the thickness of it is less than 10 μm The oxidization of the alloy is in the first grade. It is also found that the oxide scales are mainly composed of Cr2O3 and TiO2. Chrome and titanium react more easily with oxygen at temperatures under the operating mode.

Gear Drive Mechanism for Continuous Variable Valve Timing of IC Engines

Continuous variable valve actuating (CVVA) technology provides high potential in achieving high performance, low fuel consumption and pollutant reduction. To get full benefits from (CVVT) various types of mechanisms have been proposed and designed. Some of these mechanisms are in production and have shown significant benefits in improving engine performance. In this investigation a newly designed gear drive mechanism that controls the intake valve opening (IVO) and closing (IVC) angles is studied. The control scheme is based on maximizing the engine brake power (P) and specific fuel consumption (BSFC) at any engine speed by continuously varying the phase between the cam shaft angle and the crank shaft angle. A single-cylinder engine is simulated by the “LOTUS” software to find out the optimum phase angle for maximum power and minimum fuel consumption at a given engine speed. The mechanism is a planetary gear drive designed for precise and continuous control. This mechanism has a simple design and operation conditions which can change the phase angle without limitation.

Application of modified polyethylene glycol hydrogels in the construction of tissue engineered heart valve

To enhance the adhesion of seeding-cells to the biomaterial scaffolds, the PEG-hydrogels were modified. Porcine aortic valves were decellularized with Triton X-100 and trypsin. The cells were encapsulated into the PEG-hydrogels to complete the process of the cells attaching to the acellular porcine aortic valves. Herein, the autologous mesenchymal stem cells （MSCs） of goats were selected as the seeding-cells and the tendency of MSCs toward differentiation was observed when the single semilunar TEHV had been implanted into their abdominal aortas. Furthermore, VEGF, TGF-β1, and the cell adhesive peptide motif RGD were incorporated. Light and electron microscopy observations were performed. Analysis of modified PEG-hydrogels TEHV＇s （PEG-TEHV） tensile strength, and the ratio of reendothelial and mural thrombosis revealed much better improvement than the naked acellular porcine aortic valve （NAPAV）. The data illustrated the critical importance of MSC differentiation into endothelial and myofibroblast for remodeling into native tissue. Our results indicate that it is feasible to reconstruct TEHV efficiently by combining modified PEG-hydrogels with acellular biomaterial scaffold andautologous MSCs cells.

Expression of matrix metalloproteinase-9 was effected by epoxy chloropropan on creating tissue engineered heart valves

Objectives To investigate the effects of epoxy chloropropan on the expression of matrix metalloproteinases-9 （MMP-9）in creating tissue engineered heart valves（TEHV）,on the tissue structures of TEHV,and to study the effects of epoxy chloropropan on the calcification of TEHV.Methods The porcine aortic valve leaflets were digested and decellularized by using detergent and trypsin.Those treated with 0.3% glutaraldehyde for 48 hours were the control group;those treated with 3% epoxy choloropropan for 24 hours were the experimental group.The cultured human bone marrow mesenchymal stem cells（hBMSCs）were seeded onto the decellularized scaffolds of TEHV.The histological studies were done with pathological sections and scanning electron microscopy and reverse transcriptase-polymerase chain reaction（RT-PCR）were used to detect the expression of MMP-9.Results In the experimental group.the histology showed that the BMSCs grew well into the pores and formed a confluent layer in decellularized scaffolds;RT-PCR indicated significantly attenuated expressions of MMP-9,compared with the control（P〈0.05）.Conclusion The decellularized porcine aortic valves treated with 3% epoxy chloropropan may inhibit the expression of MMP-9;therefore epoxy chloropropan may prevent the calcification of tissue engineered heart valves.

Large-Scale Surface Modification of Decellularized Matrix with Erythrocyte Membrane for Promoting In Situ Regeneration of Heart Valve

In situ regeneration is a promising strategy for constructing tissue engineering heart valves(TEHVs).Currently,the decellularized heart valve(DHV)is extensively employed as a TEHV scaffold.Nevertheless,DHV exhibits limited blood compatibility and notable difficulties in endothelialization,resulting in thrombosis and graft failure.The red blood cell membrane(RBCM)exhibits excellent biocompatibility and prolonged circulation stability and is extensively applied in the camouflage of nanoparticles for drug delivery;however,there is no report on its application for large-scale modification of decellularized extracellular matrix(ECM).For the first time,we utilized a layer-by-layer assembling strategy to immobilize RBCM on the surface of DHV and construct an innovative TEHV scaffold.Our findings demonstrated that the scaffold significantly improved the hemocompatibility of DHV by effectively preventing plasma protein adsorption,activated platelet adhesion,and erythrocyte aggregation,and induced macrophage polarization toward the M2 phenotype in vitro.Moreover,RBCM modification significantly enhanced the mechanical properties and enzymatic stability of DHV.The rat models of subcutaneous embedding and abdominal aorta implantation showed that the scaffold regulated the polarization of macrophages into the anti-inflammatory and pro-modeling M2 phenotype and promoted endothelialization and ECM remodeling in the early stage without thrombosis and calcification.The novel TEHV exhibits excellent performance and can overcome the limitations of commonly used clinical prostheses.

Immobilization of Decellularized Valve Scaffolds with Arg-Gly-Asp-containing Peptide to Promote Myofibroblast Adhesion

The cell adhesive properties of decellularized valve scaffolds were promoted by immobilization of valve scaffold with arginine-glycine-aspartic acid （RGD）-containing peptides. Porcine aortic valves were decellularized with trypsin/EDTA, and detergent Triton X-100. With the help of a coupling reagent Sulfo-LC-SPDP, the valve scaffolds were immobilized with glycine-arginine-glycine-aspartic acid-serine-proline-cysteine （GRGDSPC） peptide. X-ray photoelectron spectroscopy （XPS） was used for surface structure analysis. Myofibroblasts harvested from rats were seeded onto the valve scaffolds. Cell count by using microscopy and modified MTT assay were performed to assess cell adhesion. Based on the spectra of XPS, the conjugation of GRGDSPC peptide with decellularized valve scaffolds was confirmed. Both cell count and MTT assay showed that myofibroblasts were much easier to adhere to the modified valve scaffolds, which was also confirmed histologically. Our findings suggest that it is feasible to immobilize RGD-containing peptides onto decellularized valve scaffolds. And the technique can effectively promote cell adhesion, which is beneficial for in vitro tissue engineering of heart valves.

Effect of a semi electro-mechanical engine valve on performance and emissions in a single cylinder spark ignited engine

In this study, an electro-mechanical valve （EMV） system for the intake valve ofa fottr stroke, single cylinder, overhead valve and spark ignition （SI） engine was designed and constructed. An engine with the EMV system and a standard engine were tested to observe the effects of the EMV on engine performance and emissions at different speeds under full load. The EMV engine showed improved engine power, engine torque and break specific fuel consumption （BSFC）. A 66% decrease in CO emissions was also obtained with the EMV system, but hydrocarbons （HC） and NOx emissions increased by 12% and 13% respectively.

Immobilization of RGD Peptidcs onto Decellularized Valve Scaffolds to Promote Cell Adhesion

Porcine aortic valves were decellularized with trypsinase/EDTA and Triton-100. With the help of a coupling reagent Sulfo-LC-SPDP, the biological valve scaffolds were immobilized with one of RGD （arginine-glycine-aspartic acid） containing peptides, called GRGDSPC peptide. Myofibroblasts harvested from rats were seeded onto them. Based on the spectra of X-ray photoelectron spectroscopy, we could find conjugation of GRGDSPC peptide and the scaffolds. Cell count by both microscopy and MTT assay showed that myofibroblasts were easier to adhere to the modified scaffolds. It is proved that it is feasible to immobilize RGD peptides onto decellularized valve scaffolds, and effective to promote cell adhesion, which is beneficial for constructing tissue engineering heart valves in vitro.