Exhaust Valve Seat Research Articles

Retracted: Influence of Sulfur and Additives on Wear of Exhaust Valve Seat of Cylinder Head

Retracted: Influence of Sulfur and Additives on Wear of Exhaust Valve Seat of Cylinder Head

APPLICATION OF FE3AL INTERMETALLIC PHASE FILLER METAL IN VALVE SEATING FACE HARD FACING

The exhaust valve seat face is a surface that degrades slowly as a result of mechanical and thermal stresses. There is extensive research on new materials for valves and for the improvement of valve production technology. This paper discusses the method of obtaining a filler metal made of Fe3Al intermetallic phase and the method of TIG hard-facing on a valve seating face made of H9S2 steel, evaluating the effects of essential hard-facing parameters. The resulting hard-facing build up was assessed in terms of quality using industrial radiography testing (RT).

Derivation and validation of heat transfer model for Spark-Ignition engine cylinder head

The valve train is located in the engine cylinder head, which has various operational heat transfer mechanisms to accommodate the combustion process. Most heat transfer studies in this area have only addressed medium-to high-power vehicles at a single running speed. In this study, a model of an air-cooled underbone motorcycle valve, valve seat, and engine cylinder head was tested to determine the thermal characteristics using actual engine operating conditions at low, medium, and high engine speeds. One-dimensional thermal simulation analyses were conducted to obtain the instantaneous heat-transfer coefficients of an actual engine. The average thermal value was determined as the boundary condition in the three-dimensional thermal analysis. A three-dimensional model was prepared using the ANSYS commercial computational fluid dynamics software package. The results show that as the engine speed increases, so does the thermal load toward the component in the engine cylinder head. The strongest temperature regions were concentrated around the combustion face. The exhaust valve held most of the heat, with the valve neck recording the highest temperature. For the intake valve, the combustion face registered the majority of the heat. The heat flux intensity was gathered in the contact surface area between the valve and its seat, between the valve stem and guide, and between the stem guide and tip section. A thermal survey was used to validate the three modelling results for two separate engine datasets. The cumulative relative errors for intake and exhaust valve seats for low engine speeds were 3.73% and 0.17%, respectively. The intake and exhaust valve seats had cumulative relative errors of 4.12% and 0.70%, respectively, at intermediate speeds. This methodology provides valuable information for analysing the heat characterisation of air-cooled engines. It can also be a useful blueprint for the automotive industry and other researchers involved in thermal measurements.

A Survey on the Oxidation Behavior of a Nickel-Based Alloy Used in Natural Gas Engine Exhaust Valve Seats

This study reports the oxidation behavior of a Ni-based alloy used in the manufacture of valve seats for automotive engine exhaust systems. Isothermal thermogravimetric analyses were carried out at temperatures of 660, 740, 860, and 900 °C under an oxygen atmosphere for up to 1 h. At 660 and 740 °C, only one stage was observed during the whole time studied. At this stage, the oxide layer was formed mainly by NiO + Cr2O3, following a linear oxidation law with a rate constant (Kl) on the order of magnitude of 10−6 kg/m2s and an apparent activation energy (Ea) of ~47 kJ/mol. At 860 and 900 °C, an identical first stage was observed with a transition to a different stage. In the second stage, the oxidation layer was composed of Cr2O3, and a parabolic oxidation law was followed with a rate constant (Kp) on the order of 10−8 kg2/m4s and Ea of ~128 kJ/mol. Moreover, the Ni-based alloy formed a dense and compact oxide layer after oxidation, with no apparent cavities, pores, or microcracks. Characterization techniques such as Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Raman Spectroscopy were carried out to characterize the formed oxide layer.

Calculation studies of the influence of exhaust gas recirculation on the characteristics of the natural gas-fueled diesel engine

When converting diesel engines to run on natural gas on the gas-diesel cycle, additional problems arise associated with the high thermal stress of the exhaust valves and valve seats at high loads and engine speeds. There is also an increase in NOx emissions due to higher combustion temperatures of natural gas. One of the ways to improve the economic and environmental performance of engines operating on a gas-diesel cycle with a lean air-fuel mixture is to optimize the combustion of the air-fuel mixture by using an exhaust gas recirculation system (EGR). The principle of operation of this system is as follows: exhaust gas entering the intake manifold and further into the combustion chamber reduces the oxygen concentration in the air-fuel mixture, which leads to a dilution effect and, accordingly, to a decrease in combustion temperature and a decrease in NOx content. In order to study the influence of EGR on the dual-fuel gas and diesel engine parameters in the AVL Boost software package, a computer model of the existing 6ChN13/15 engine was developed. A low-pressure EGR system with an exhaust gas cooler was simulated on this engine. Values of NOx emissions, brake specific fuel consumption (BSFC) and brake efficiency have been obtained at different recirculation rate by calculation method. These values allow to estimate the feasibility of using a cooled EGR in a natural gas-fueled diesel engine.

Influence of Sulfur and Additives on Wear of Exhaust Valve Seat of Cylinder Head

In this paper, taking a certain type of high-power diesel engine exhaust valve abnormal wear phenomenon as an example, we conduct research on the exhaust valve surface micromorphology characteristics, contact surface accumulation products, additive transition layer, and combustion test. These passed diesel sulfur content comparative test, diesel additive composition analysis, and high-sulfur-content and low-sulfur-content diesel and diesel oil additive action test. At present, there is no authoritative research on the influence of sulfur content in diesel on valve seat wear of high-power diesel engines, and the protection mechanism of diesel additives on the valve seat is not clear. The sulfur in diesel, like the lead in gasoline, has long been known to resist wear in the valve seats of high-power diesel engines; just as gasoline additives compensate for the loss of lead, diesel oil additives seem to compensate for the loss of sulfur. Tests show that a uniform carbon deposition layer is formed on the contact surface after the diesel is burned, and the carbon deposition layer is more densely and uniformly adsorbed on the contact surface under the action of diesel additives to form an antiwear layer. Tests also show that the sulfur in diesel has no effect on the wear resistance of the valve seat.

Cause Analysis and Preventive Measures of Cavitation Corrosion of Diesel Engine Exhaust Valve Seat

This paper analyses the formation of cavitation in the exhaust valve seat of marine diesel engine in combination with leakage of the exhaust valve seat. The paper mainly starts from the cooling water system of the diesel engine that affects cavitation. Finally, the paper puts forward some preventive measures of cavitation corrosion.

Influence of Cryogenic Temperatures on Mechanical Properties of Valve Seats of Internal Combustion Engines

Valve seats of internal combustion engines are used in cylinder heads, due to increase the strength and abrasion resistance of the intake and exhaust valve seats. Valve seats are made from alloy cast iron, high-alloy steels, wear-resistant alloys and seats made using powder metallurgy. The valve seats are pressed into the head. Some materials must be deep-frozen before pressing to reduce the pressing overlap. The overlap is large, in the order of tenths of a millimetre, due to the guaranteed seating of the seat in the cylinder head. The amount of overlap depends also on the material of the cylinder head. Liquid nitrogen (about -196 °C) is used for freezing. In our case, these are monometallic seats, made by technology of precision casting from cobalt alloys. A particular type of cobalt alloy uses the trade name STELLITE.

Computational Analysis of Dissimilar Materials Engine Valve: Technical Note

Engine exhaust valve are exposed to severe thermal loads and chemical corrosion. Exhaust valve opens and closes 2000 times per mile for passenger cars. Generally the material for manufacturing exhaust valve and exhaust valve seat insert have properties for working at high temperature continuously and resistance to corrosion due to their surrounding environment. Usually engine valve is made up of austenitic steels. This valve is to be replaced by a light weight dissimilar materials preferably by an Al6061 and FE 430 steel. In this paper, computational fluid dynamic analysis of such valve is presented. The flow characteristics and strength of the valve are assessed.

Numerical Simulation of Heat-and-Mass Transfer Processes in the Cooling Passages of a Cylinder Head in a Diesel Locomotive Engine

Results are given for the comparative numerical simulation of heat-and-mass transfer processes in the cooling passages of a cylinder head in diesel locomotive engine 16 FN 26/27 running under rated power conditions at different engine boost levels. The advanced numerical methods used are shown to ensure a high degree of accuracy and information content when simulating heat-and-mass transfer processes, and enable evaluating the local values of flow parameters with account of the complex configuration of the flow parts in the cooling passages and the impact of operating parameters. The results show that an increasing boost level of a diesel engine and, respectively, a growing thermal load degrade drastically the conditions of heat rejection from the most thermally stressed zones of the cylinder head – the central part of the bottom face in the area of the injector bore and of the bridge between the bores of exhaust valve seats. The paper assesses the impact of the boost level on the effectiveness of heat rejection from the most thermally stressed areas of the cylinder head of a diesel locomotive engine. Conclusions and recommendations for improving the operating conditions of the cylinder head are given.

Prediction of Wear Loss of Exhaust Valve Seat of Gasoline Engine Based on Rig Test Result

Prediction of Wear Loss of Exhaust Valve Seat of Gasoline Engine Based on Rig Test Result

Experimental investigation on 4-strokes biodiesel engine cooling system based on nanofluid

Abstract Global biodiesel production grew by 23% per year between 2005 and 2015, leading to a very strong expansion of the sector in a decade and, at the same time, the interest in the use of liquid biofuels/biodiesel in compression ignition engines has grown quickly. Taking into account that the use of biodiesel in IC engines directly affects their coolant temperature, with impact on performance, in this study an experimental campaign has been carried out on a 4-strokes single cylinder engine, aimed to assess whether the use of nanofluids, instead of water, could be a valuable solution to reduce peak engine temperature. Such nanofluids were characterized by higher thermal conductivity compared to conventional fluids, due to CuO nanoparticles added at different concentrations within the base fluid. Measurements of temperature were recorded at steady and unsteady conditions, by proper thermocouples located around the exhaust valve seat in the cylinder head and in the exhaust valve spindle. Particularly, temperatures of the exhaust valve spindle and exhaust valve seat in the cylinder head were measured at part and full engine loads, using water as coolant and then CuO based nanofluids. Experimental results showed that, at 100% engine load in unsteady conditions, it was possible to achieve a temperature reduction up to 13.6% on the exhaust valve seat and up to 4.1% on the exhaust valve spindle, when nanofluid at 2.5% volume concentration was used.

엔진내구시험을 통한 Valve Train 수명예측에 관한 연구 (2)

In previous study, make an attempt to estimate exhaust valve seat and seat-ring wear acceleration factor for engine durability test with measuring and consideration of wear mechanism. But found abnormal initial wear rate in exhaust valve seat-ring. And have to improve exhaust valve seat-ring wear rate for reliability reason, because next GDI/Turbo engine is based on this engine and GDI/Turbo engine have higher combustion pressure and higher thermal load. In this study, Trying to find the cause of abnormal wear factor, improve valve-train durability by change specification & design of parts and verify variant parts for improving durability of valve-train. And then I would like to propose a design guide line of valve-train system in a reliability point of view, besides make a complement of previous study.

Failure analysis of the engine cylinder of a training aircraft

Two-blade aircraft propellers, designed to be powered by a small engine, were improved with engines used in three-blade aircraft propellers. As a consequence, the new engines revealed pressure losses, crack formation, and recurrent fracture, approximately after every 600h of flight. This paper analyzed one of the failed engines; the engine has six cylinders manufactured in aluminum alloy. Optical microscopy and scanning electron microscopy were used for microchemical and microstructural analyses. Cracks were identified by using liquid penetrant between two cooling fins in the exhaust port and around the exhaust port, at the exhaust valve seats. Shrinkage micropores were found in the aluminum alloy forming cracks in the exhaust port.

Effects of prior surface damage on high-temperature oxidation of Fe-, Ni-, and Co-based alloys

Multi-component metallic alloys have been developed to withstand high-temperature service in corrosive environments. Some of these applications, like exhaust valve seats in internal combustion engines, must also resist sliding, impact, and abrasion. The conjoint effects of temperature, oxidation, and mechanical contact can result in accelerated wear and the formation of complex surface layers whose properties differ from those of the base metal and the oxide scale that forms in the absence of mechanical contact. The authors have investigated the effects of prior surface damage, produced by scratch tests, on the localized reformation of oxide layers. Three high-performance commercial alloys, based on iron, nickel, and cobalt, were used as model materials. Thermogravimetric analysis (TGA) was used to determine their static oxidation rates at elevated temperature (850 °C). A micro-abrasion, ball-cratering technique was used to measure oxide layer thickness and to supplement the TGA results. By using taper-sectioning techniques and energy-dispersive elemental mapping, a comparison was made between oxide compositions grown on non-damaged surfaces and oxides that formed on grooves produced by a diamond stylus. Microindentation and scratch hardness data revealed the effects of high-temperature exposure on both the substrate hardness and the nature of oxide scale disruption. There were significant differences in elemental distribution between statically formed oxides and those that formed on scratched regions.

自動車エンジン用Ｃｏフリー排気バルブシート材の開発

Sintered materials have been widely used for valve seat insert (VSI) for automotive engines. They have possessed high flexibility in their alloying design to increase their performance in heat and wear resistance in comparison with that of conventional wrought steel and cast alloys. Especially several high cobalt containing sintered materials are used as exhaust valve seat insert materials because it's high wear and heat resistant properties. Recently, the circumstance of exhaust valve seat inserts has become sever due to A/F ratio (Air/Fuel ratio) of recent engines are set to leaner than that of conventional. This trend is aim to reduce exhaust gases and fuel consumption. On the other hands, the reduction use of high environmental burden materials such as cobalt has also been continually needed. And cobalt is expensive, reduce cobalt content is good for economy of these materials. This paper reports the development and the application detail of cobalt-free, lead-free and environmentally friendly exhaust valve seat insert.

403 環境対応ガソリンエンジンにおける排気バルブシートの開発

The recent passenger car gasoline engines have oriented for low fuel consumption and low emission due to the eco-friendly requirements. As the concrete problem to develop the eco-friendly engine, the exhaust valve seat insert is exposed to severe wear condition by friction due to the rise of combustion temperature with the progress of the lean burn. This paper is to introduce the exhaust valve seat insert which we have developed for this kind ofeco-friendly gasoline engine.

Wear Mechanism Analysis of Engine Exhaust Valve Seats with a Laboratory Simulator

Engine valve seat wear affects engine performance. A common goal for both valve and engine manufacturers is to improve both valve quality and life. By performing tests on a simulator which is verified to be capable of simulating an engine operating environment, the wear resistance of various valve materials is ranked, and the wear mechanisms are investigated. Four commonly used exhaust valve materials, 23–8N, 21–4N Mod, Pyromet 31 and Stellite 6 (hardfacing), were tested with insert material made of Sil XB at an operating temperature of 538° C. Tests run for three million cycles showed that Pyromet 31 had the lowest wear rate and 21-4N Mod had the highest. Then, three valve materials, 23-8N, 21-4N Mod and Pyromet 31, were tested with insert material made of Eatonite 6 at an operating temperature of 649° C. These tests gave the same ranking as those tested with the Sil XB inserts. However, all three valve materials in the second group showed much less wear than those in the first group. The valve seat wear mechanisms were found to be a complex combination of abrasive wear, adhesive wear/material transfer, plastic deformation and oxidation. Based on analysis of the test specimens by scanning electron microscopy and energy dispersive X-ray, the degree to which these mechanisms appeared varied with different materials. Some ways to make valve materials more wear resistant to these mechanisms would be to select more compatible valve and insert materials and to improve the operating environment. Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

The Elimination of Lead in Gasoline

Due to the health consequences of lead exposure, as well as to the introduction of catalytic converters, many countries have reduced or eliminated use of lead additives in motor gasolines. But in many other countries, leaded gasoline remains the norm. In these countries there is often confusion about the health significance of gasoline lead, the ability of cars to use unleaded gasoline, and the costs of unleaded gasoline. This chapter shows that leaded gasoline is a major source of human lead exposure. All cars, with or without catalytic converters, and with or without hardened exhaust valve seats, can use unleaded gasoline exclusively. Unleaded gasoline typically costs on the order of $0.01 more per liter than leaded gasoline to produce. Recent concerns about benzene exposure from unleaded gasoline have been addressed through choice of gasoline formulation and other measures.

The Elimination of Lead in Gasoline

Due to the health consequences of lead exposure, as well as to the introduction of catalytic converters, many countries have reduced or eliminated use of lead additives in motor gasolines. But in many other countries, leaded gasoline remains the norm. In these countries there is often confusion about the health significance of gasoline lead, the ability of cars to use unleaded gasoline, and the costs of unleaded gasoline. This chapter shows that leaded gasoline is a major source of human lead exposure. All cars, with or without catalytic converters, and with or without hardened exhaust valve seats, can use unleaded gasoline exclusively. Unleaded gasoline typically costs on the order of $0.01 more per liter than leaded gasoline to produce. Recent concerns about benzene exposure from unleaded gasoline have been addressed through choice of gasoline formulation and other measures.