Exhaust Stroke Research Articles

A Twice-Open Control Method for a Hydraulic Variable Valve System in a Diesel Engine

In order to solve the cold-starting problem and improve the intake and exhaust pipe temperatures of diesel engines under cold-starting and low- and medium-speed conditions, this paper proposes a twice-open control method for a hydraulic variable valve system. First, a hydraulic variable valve system that can realize a fully variable valve lift and phase angle is applied to replace the original intake system in order to meet the air intake requirements of different conditions. Then, a twice-open control method in which the intake valve opens two times at the exhaust stroke and intake stroke is proposed to improve the intake pipe temperature and solve the cold-starting problem. This paper contains a numerical work analysis. A GT-POWER model is constructed to validate the intake valve twice-open control method. The cylinder pressure, cylinder temperature, intake pipe pressure, and intake pipe temperature are obtained and compared between the original intake valve system and the hydraulic variable valve system with the proposed intake valve twice-open control method. The results show that the twice-open control method can increase the intake pipe temperature to 260 K or even higher, which can improve the cold-starting performance and the exhaust temperature at low and medium speeds. At the same time, the performance under low- and medium-speed conditions is improved.

Investigation of gas exchange parameters of small two stroke engine correlated with hydrogen fuel supplement

Due to the lack of complete dedicated suction and exhaust strokes and obviate the need of valvetrain assembly in two stroke engines, the bottom surface of the piston and the crankcase is used as a scavenging pump leads to that about one fifth of the fresh charge is short-circuited to the exhaust results in very high hydrocarbon emissions and poor fuel consumption. It is suggested that a combination of gasoline and hydrogen could be a superior solution combining the advantages of both engine itself and hydrogen doping. An accurate amount of hydrogen that has high flame propagation speed blended with gasoline could provide faster combustion of fuel mixture over the few crank angle degrees in the short gas exchange process reducing short-circuited charge with little modifications to the engine system. In this paper hydrogen-gasoline blend as an alternative fuel in a 63.3 cc, air cooled single cylinder, crankcase scavenged two stroke engine is tested. The unseen decommissioning of small two stroke engine in near future, the attractiveness of studying alternative fuel specially hydrogen and absence of investigation of the effect of hydrogen fuel supplement on gas exchange parameters molded this paper.

RETRACTED: Research on the kinetics characteristics and in-cylinder combustion of opposed rotary piston engine for different power output modes

As a new type of internal combustion engine, opposed rotary piston (ORP) engine has the advantages of simple structure and high working frequency, and can achieve high power density. Consequently, it stands as an ideal power source for hybrid power systems and unmanned aerial vehicles. The ORP engine has different power output modes, corresponding to different piston rotation and volume evolutions of combustion chamber. However, the effect of power output modes on kinetics characteristics and in-cylinder combustion of ORP engines are still uncovered. In this paper, the kinematic model of an ORP engine is established for scenarios involving power output by different shafts (Shaft 1 and Shaft 3). Meanwhile, the piston rotation patterns and cylinder volume variations are investigated correspondingly. Further, three-dimensional numerical model of the ORP engine is established, enabling analysis of in-cylinder combustion characteristics, engine performance, as well as nitrogen oxides (NOx) emissions. The results indicate that the volume variations of all cylinders follow a consistent pattern under the power output by Shaft 3. A pair of opposed cylinders features longer durations of intake and expansion strokes, and shorter durations of compression and exhaust strokes, the other pair of combustion chambers is the opposite under the power output by Shaft 1. The engine demonstrates a charging efficiency of 95.36 %, with corresponding indicated thermal efficiency and indicated power output of 38.08 % and 40.9 kW, respectively. The two adjacent cylinders present significantly different operation processes in the case of the power output by Shaft 1, achieving charging efficiencies of 94.29 % and 89.11 %, respectively, with the indicated thermal efficiency of 34.49 % and 31.60 %. The corresponding minimum indicated specific fuel consumption under the two power output modes are 211.7 g/kW∙h and 243.7 g/kW∙h, respectively, accompanied by NOx emission factors of 25.3 g/kW∙h and 17.6 g/kW∙h. With the given range of ignition timing, a trade-off relationship exists between the engine performance and NOx emissions. The power density of the case of power output by Shaft 3 is superior to that of Shaft 1.

Review of the atypical systems of slow-speed two-stroke marine engines

This article provides a review of the varying systems of slow-speed, two-stroke marine engines. The paper begins with the operating principles of the typical two-stroke engine cycle employed in these engines, highlighting the intake, compression, combustion, and exhaust strokes. It then continues with defining and describing other unconventional systems rarely found on engines of different sizes and applications. The focus of the study case is on the systems that prevent pollution, as well as various other systems observed in larger marine engines.

Innovative developments on the use of hydrogen in transport internal combustion engines and power plants

BACKGROUND: Innovative technologies and design solutions aimed at using hydrogen in internal combustion engines and hydrogen power plants are reviewed in the paper. The advantages of hydrogen fuel are shown and the main problems that Western automakers face and which determine the ways to solve problems in road transport are identified. In this regard, the method of using hydrogen energy in internal combustion engines and hydrogen power plants becomes a decisive factor.
 AIMS: Search for a reasonable and effective method of using hydrogen in transport.
 METHODS: The technologies of hydrogen production with the electrolysis method and on-board generation of hydrogen using hydrogen-containing components are considered. It is proposed to use ammonia as a hydrogen carrier reagent for operation in dual-fuel diesel internal combustion engines.
 RESULTS: It is noted that ammonia, with a high level of hydrogen content in the molecule, is relatively safe, has a low cost and a significant volume of production. It is easier to store and transport compared to hydrogen. For internal combustion engines operating on hydrocarbon fuel, the use of ammonia and hydrogen, its derivative product, is attractive due to the need to remove highly toxic nitrogen oxides containing in the exhaust gases of diesel internal combustion engines.
 One of the main problems of creating an environmentally friendly diesel engine associated with reducing the NOx content to an environmentally safe level is considered. A positive factor of using ammonia is the on-board production of hydrogen in the thermal reactor, as well as the possibility of organizing an effective process of neutralizing nitrogen oxides in a diesel engine.
 CONCLUSIONS: The use of ammonia to generate hydrogen allows the diesel engine to implement the process of selective reduction of nitrogen oxides when ammonia is injected into the combustion chamber at the exhaust stroke. This method will significantly increase the efficiency of NOx neutralization in a diesel internal combustion engine due to the possibility of temperature regulation of the NOx neutralization reaction directly in the cylinder and in the exhaust system of the internal combustion engine.

Experimental investigation on effect of misfire and postfire on backfire in a hydrogen fuelled automotive spark ignition engine

This study investigates the effect of misfire and postfire on backfire in a hydrogen-fuelled automotive spark ignition engine. Backfire is a preignition phenomenon and the flame propagates toward the engine's intake manifold during the suction stroke. Postfire is a post-ignition phenomenon occurring in the exhaust manifold during the exhaust stroke and the flame propagates towards the exhaust manifold or backflow to the combustion chamber or combined both. Misfire occurs when cranking the engine (starting), fouled spark plug, and unoptimized spark timing. Several misfire cycles lead to an increase in the accumulation of unburnt hydrogen-air charge inside the cylinder and 13% hydrogen leaves the exhaust manifold resulting in postfire occurrence in a subsequent cycle. The postfire in the current cycle acting as an external ignition source for the preignition of the accumulated hydrogen-air charge results in backfire in the immediate next cycle. The misfire, postfire and backfire stall the engine operation due to a drop in indicated mean effective pressure. The experimental data indicates the backfire limiting equivalence ratio (BLER) should decrease with an increase in the engine speed as the equivalence ratio varies from 0.91 at 2000 rpm to 0.4 at 4900 rpm. As too advancement of spark timing increases the probability of misfire leading to postfire and backfire, the engine must be operated at backfire limiting spark timing to avoid misfire, postfire, and backfire occurrence. An important point emerged from this study that misfire without postfire does not lead to backfire occurrence. Physical mechanisms and mitigative measures for misfire, postfire and backfire are discussed in detail.

Performance of large-diameter pneumatic down-the-hole (DTH) hammers: A focus on influences of the hammer structure

Pneumatic down-the-hole (DTH) hammer has been extensively used in air drillings through hard and ultra-hard geological formations. Numerical modeling can offer close observation on the working behaviors by visualizing internal pressure status as well as provide reliable performance predictions for large-diameter DTH hammers to which conventional empirical and experimental approaches cannot be applied. In this study, CFD simulations coupled with dynamic meshing are utilized to simulate the air flow and piston movement inside the large-diameter DTH hammers. The numerical modeling scheme is verified against a theoretical model published in literature. Effects of structural parameters on hammer performance, including piston mass, piston upper-end diameter, piston groove diameter, and lengths of intake and exhaust stroke in both front and rear chambers, are analyzed in detail by virtue of sets of numerical simulations. The simulations suggest that changing the intake stroke of front chamber has a negligible influence on hammer performance while increasing the piston groove would lower all the four indicators of hammer performance, including impact energy, impact frequency, maximum stroke, and air consumption rate. Changing the other structural parameters demonstrates mixed effects on the performance indicators. Based on the numerical simulations, a large GQ-400 DTH hammer has been designed for reduced air consumption rate and tested in a field drilling practice. The air drilling test with the designed hammer provided a penetration rate 1.7 times faster than that of conventional mud drilling.

Algorithm for Cycle-To-Cycle Firing TDC Identification Based on Wasted Spark Duration Measurements in Small Engines

Spark ignition (SI) engines are often used as distributed power generation applications. They ensure quick deployment, cost effective electricity, and are a valid choice for back-up power. An essential aspect for small size engines is to improve control margins without increasing the number of sensors. It is not uncommon to employ fixed ignition timing for such power units, with so called wasted spark systems. These feature two spark events per cycle, one during compression and one during the exhaust stroke. On the other hand, ever more complex control systems are applied for this engine category in the search for better efficiency and lower emissions. Control of actuators that is phased with the working cycle could represent a significant advantage in this context. A method previously developed for identifying top dead center (TDC) phasing offline was applied as an algorithm capable of performing the required task while the engine is running. It is based on current measurements in the secondary ignition circuit of systems that feature wasted spark operation. Validation was performed on a 50 cm3 SI unit connected to a 1 kW power generator. Statistical distribution during sequences of 1000 cycles recorded at five different levels of load was used for testing TDC identification capabilities. Results were also compared to evaluations based on engine speed measurements. The overall TDC identification success rate of the proposed algorithm was found to be over 99.8%.

Analysis of the effects of lubricating oil viscosity and engine speed on piston-cylinder liner frictions in a single cylinder HCCI engine by GT-SUITE program

Engines with homogenous charge compression ignition (HCCI) are the low-temperature combustion models in which automatic oxidation reactions occur with the effect of in-cylinder pressure and heat at the end of preparation of homogenous air-fuel mixture and compression stroke within the cylinder by means of port injection or early direct injection. In-cylinder gas temperatures of such engines during the cycle are lower than conventional internal combustion engines. Therefore, they cause zero NOx and soot emissions. Moreover, the occurrence of combustion in very small crankshaft angles results in a decrease in heat losses observed in cylinder walls and an increase in thermal efficiency. Reducing mechanical friction is highly significant for increasing the effective productivity of HCCI engines. In internal combustion engines, 10% of total energy obtained from the fuel is spent on the heat emerging due to mechanical frictions. 20% of mechanical friction results from the friction occurring between piston ring and liners. In this article, frictional characteristics of compression ring (TOP) and piston skirt area have been examined for two different engine speeds and lubricants, by using technical properties of single-cylinder HCCI engine and in-cylinder pressure and temperature data obtained under full load by means of GT-SUITE software. As the increase in pressure, occurring inside the cylinder at the end of the exhaust stroke and at the beginning of intake stroke, increases ring pressure load in HCCI engines, higher level of piston ring frictions has been observed when compared to internal combustion engines with the same technical properties. Piston ring contact pressure force is a more effective parameter in terms of piston frictions, when compared to hydrodynamic pressure force. The use of lubricants with higher viscosity (SAE 10W-40) has enabled the piston to move more laterally. According to the analysis results, a maximum piston speed of 3.92 m/s for 800 rpm engine speed and 7.85 m/s for 1600 rpm engine speed has been obtained. Maximum friction power losses have been found as 63.84 W at 800 rpm engine speed and 85.91 W at 1600 rpm engine speed. Oil film thickness has obtained in the middle of the piston stroke in the intake, compression, power and exhaust strokes, respectively, 1.809, 1.674, 1.547 and 1.792 µm at 800 rpm engine speed and 1.101, 1.018, 0.932 and 1.119 µm at 1600 rpm engine speed.

Numerical Study of Exhaust Manifold

Abstract: The Exhaust manifold is an important component which affects the performance of the I.C engine. The exhaust system for any type of vehicle consists of an exhaust manifold, catalytic converter, resonator and a muffler which is connected to a tailpipe. Exhaust gases at the end of exhaust stroke are sent to the exhaust manifold through exhaust valves. The exhaust manifold has to withstand and operate under high exhaust temperature and pressure. The design aspect of the exhaust manifold has to be done through trial and error method to find the optimum layout to extract the performance of the manifold. In this paper, we will analyse the exhaust manifold through conjugate heat transfer. Keywords: Exhaust Manifold, Solidworks, Ansys, Conjugate Heat Transfer

Measurement of Cyclic Variation of the Air-to-Fuel Ratio of Exhaust Gas in an SI Engine by Laser-Induced Breakdown Spectroscopy

Temporally and spatially resolved laser-induced breakdown spectroscopy (LIBS) was applied to a four-stroke, single-cylinder test engine’s cyclic exhaust gas to demonstrate engine performance. The LIBS technique provided quantitative air-to-fuel ratio (A/F) measurements by generating localized breakdown plasma during the compression and exhaust strokes. The results showed that the timing and duration settings of the emission energy ionization and molecular spectra affect the intensity peaks. Optimum measurements performed between 200 ns and 10 ms after breakdown resulted in observed atomic spectra of CI (248 nm), Hβ (485 nm), Hα (656 nm), NI (745, 824 nm), and OI (777, 844 nm). The intensities of CI (248 nm) and Hα (656 nm) decreased with increasing A/F, whereas the intensity ratios of NI and OI remained constant. A decrease in the intensity ratio of C/O and Hα/O was observed as the A/F increased. This study is a major step toward defining a means of using LIBS to control the A/F ratio in gasoline engines by focusing on the exhaust gas rather than the flame.

Experimental Determination of Suitability of Algae Bio Diesel Blend as an Alternate to Diesel Fuel using Cylinder Pressure Variation with Respect to Crank Angle

Scientific and engineering community of whole world is working day and night to develop an alternate of fossil fuel. This is not only due to continuous depletion of fossil fuel reserves but also for day by day increasing global warming. This global warming is mainly due to emission of harmful gases from manufacturing industries and vehicles used for transportation including aerial vehicles. In this paper, an experimental study has been performed in variation of mean cylinder pressure at crank angles divided into 4 categories for each stroke. 180 actual movement of crankshaft is taken as 90 for study. Further analysis is done for all the four strokes starting from power stroke at 0 and end of compression stroke as 360 (actually 720). The fuel used for the study is a 20% blend of biodiesel named as B20 in the paper. The experimental results obtained in a variable compression ratio engine are compared with the corresponding characteristics of fossil fuel. Diesel named as D100 which is a proved and widely used fuel at present. The comparative study has shown a clear indication that though biodiesel blend B100 may not be suitable in, as it’s condition but blend B20 may be suitable to be used in as is condition as the experimental results are not varying largely with that of pure diesel. Variation in power strokes and exhaust strokes were found to have larger deviation from linear trend whereas it followed linear variation in induction and compression stroke. The performance can be improved further by using suitable additive in further research works.

A Computational Fluid Dynamics Investigation Comparing the Performance of an Alternative Valvetrain Design Against a Traditional Poppet Valvetrain

Abstract The poppet valve is by far the most widely used in cylinder head design of internal combustion (IC) engines; however, poppet valves themselves create significant flow restrictions during both the intake and exhaust strokes, thus causing a reduction in volumetric efficiency that affects overall engine performance. By removing the restrictive poppet valve from the flow path of air into and out of the cylinder head and allowing air to flow unobstructed, any given IC engine can achieve greater volumetric efficiency and higher specific output. The Vaztec ECOREV rotary valve system utilizes straight-cut flow passages that reduce such restrictions. This rotary valve system is designed to be directly driven by the crankshaft, thereby replacing the camshaft and poppet valve system altogether. This paper will primarily explore the differences in flow characteristics between this rotary valve and a conventional poppet valve cylinder head using both computational fluid dynamics (CFD) and flow bench data. Both configurations will be evaluated on the same single-cylinder four-stroke internal combustion engine. CFD simulations were run at multiple valve opening positions on each cylinder head configuration for both intake and exhaust cycles to validate the CFD process against flow bench test data for both cylinder head designs. The CFD was performed in 3D using hexahedral meshing and steady-state Reynolds-averaged Navier–Stokes (RANS) turbulence models. Comparison between the two engine configurations will include both intake and exhaust airflow rates as well as discharge coefficients and overall flow field evaluation using numerous scalar and vector properties.

In-cylinder gas flow characteristics study of CI engine under motoring and pre-ignition firing conditions using a high-speed PIV

Engine properties such as engine speed and fuel injection quantity may affect the swirl flow of diesel engines. In this paper, experiments are conducted at two engine rpm and various operation conditions. For instance, motoring with no fuel injected, pre-ignition firing conditions, in addition to different fuel quantities. In this experimental analysis, PIV technique is performed to observe the flow patterns of the charging gas. The obtained results indicate that the swirls behavior is similar under all operation conditions during the intake and compression strokes regardless of the engine speed. In comparison to pre-ignition firing process, generation of more swirl centers has been observed for both engine speeds i.e., 1000 rpm and 1500 rpm under motoring conditions. Additionally, at CA of 610 deg., the swirls centers were maintained for all configurations except for motoring conditions and lowest fuel quantity of 2 mg. Moreover, during expansion strokes for both engine speeds the least magnitude of velocity-vectors was observed under motoring condition. Nevertheless, the higher mean velocity-vectors among that of expansion stroke was observed under pre-ignition firing configuration. The obtained results suggest that, the movement of the induced swirl centers across the piston cavity during expansion to exhaust strokes and increasing the engine speed corresponded to an increase in the mean-velocity, swirl ratios, and TKE.

Water injection in spark ignition engines—Impact on engine cycle

Water injection in internal combustion engines is mainly used for additional cooling of the combustion chamber and knock suppression. The main advantages of the water injection are the potential for the enhancement of the performance of the engine. Studies conducted so far have aimed to track engine performance at maximum load and fuel consumption (brake-specific fuel consumption BSFC). Specialized literature is less consistent as regards to the injection of water at medium and low loads. This work monitors the effects of water injection at medium loads and the evolution processes of the four-strokes in the engine with and without water injection. A side-valve, air cooled natural aspirated engine with water and fuel injections in the intake manifold was used for this study. The work during expansion was increased, but this trend was reversed by the higher loads required during intake, compression and exhaust strokes, leading to a reduction in the indicated efficiency when water was injected.

The Influence of Cycle-to-Cycle Hydrocarbon Emissions on Cyclic NO:NO2 Ratio From a HSDI Diesel Engine

Abstract Knowledge of the NO:NO2 ratio emitted from a diesel engine is particularly important for ensuring the highest performance of selective catalytic reduction (SCR) NOx after-treatment systems. As real driving emissions from vehicles increase in importance, the need to understand the NO:NO2 ratio emitted from a diesel engine during transient operation similarly increases. Previous work by the authors identified significant differences in NO:NO2 ratio throughout the exhaust period of a single-engine cycle, with proportionally more NO2 being emitted during the blowdown period compared to the rest of the exhaust stroke. At the time it was not known what caused this effect. In this study, crank-angle resolved NO and NO2 measurements using fast response chemiluminescence detector (CLD) (for NO) and a new fast laser-induced fluorescence (LIF) instrument (for NO2) have been taken from a single-cylinder high-speed light-duty diesel engine at three different speed and load points including a point with and without exhaust gas recirculation (EGR). In addition, crank-angle resolved unburned hydrocarbon (UHC) measurements have been taken simultaneously using a fast flame ionization detection (FID). The NOx emitted per cycle and the peak cylinder pressure of that cycle have shown high correlation coefficients (R2 < 0.97 at all test points) in this work. In addition, a variation of the NO:NO2 ratio through the engine's exhaust stroke is also observed indicative of in-cylinder stratification of NO and NO2. A new link between the NO:NO2 ratio and the UHC emissions from an individual engine cycle is observed - the results show that where there are higher levels of UHC emissions in the first part of the exhaust stroke (blowdown), perhaps caused by injector dribble or release from crevices, the proportion of NO2 emitted from that cycle is increased. This effect is observed and analyzed across all test points and with and without EGR. The performance of the new fast LIF analyzer has also been evaluated, in comparison with the previous state-of-the-art and standard “slow” emissions measurement apparatus showing a reduction in the noise of the measurement by an order of magnitude.

Comparative evaluation of 4-cylinder CI engine camshaft based on FEA using different composition of metal matrix composite

The Camshaft is a vital part of the Internal Combustion engine of automobiles. It functions as a timing mechanism that controls the opening and closing of the inlet and exhaust valves, as well as the valve overlap that occurs at the TDC of the exhaust stroke. The camshaft is made up of several journals that run on bearings within an engine. The camshaft is bound to rotate with the crankshaft by either a set timing gear, timing belt, or timing chain. As the camshaft drive fails, the valves and piston crowns come into contact, causing extensive internal damage. For high-speed diesel engines (Compression Ignition), power impulses have a greater value than spark-ignition engines in multi-cylinder configurations. In this study, a comparative analysis of an existing automobile camshaft of four-stroke, a four-cylinder Compression Ignition (CI) engine made of Cast Iron was carried out with different compositions of metal matrix composites. For this condition, the outcomes were taken as Von-Mises stresses and displacement values for the static state of the camshaft. The modal analysis (Free vibration) was performed using ANSYS after the static analysis results were obtained. Finally, comparing all the results obtained for different materials, the AlSiC 20% metal matrix composite has been recommended as the most suitable material for the production of camshafts which can replace cast iron because of its similar behavior as to cast iron. This will aid in the development of more precise camshafts, which will be useful for larger displacement engines.

Analysis of the effectiveness and the possibility of creating an auxiliary braking system for an electronically controlled vehicle of the utility patent No. 153 247

The paper notes that electronic control of work processes in vehicle units and systems is one of the most effective and modern ways to improve their operational parameters. The means of electronics make it possible to increase the average speed of vehicles, reduce fuel consumption, improve controllability, stability, passability and smooth driving, improve braking performance and safety, and facilitate driving. All modern vehicle electronic systems are digital, data transfer rate is up to 1 megabit per second. This allows each sensor to be used for several systems. Dimensions of sensors are gradually decreasing, their speed, reliability, and accuracy are increasing. One perspective way to improve vehicles is the use of an internal combustion engine with electronic control of its braking torque as an auxiliary braking system. The analysis of the patent № 153 247 for useful model "Auxiliary braking system of vehicle with electronic control" is considered and its analysis using the valve timing diagrams. The errors made in the description of the patent were revealed. The description of the intake and exhaust strokes does not take into account the increase in the cylinder volume by the manifold volume due to the opening of the respective valves and the fact that the pressure in the exhaust tract is limited by the preloading force of the engine exhaust brake springs. The electromagnetic valve must have speed by an order of magnitude greater than the regular valves and the same capacity, its springs must have a large pre-pressure so that it does not open under the pressure in the receiver of the regular brake system. For fast pressure release, the electromagnetic valve must open a large flow cross-section as quickly as possible, overcoming the force of the high pressure acting on its disc in the cylinder (7.5 MPa) plus the force of pre-pressure of the valve springs. The formulas for determination of the valve throughput capacity of the valve, analysis of which showed that to ensure a given capacity of the valve by reducing its opening time it is necessary to proportionally increase the height of the rise of electro-magnetic valve or the average diameter that is not always possible. The analysis carried out in the article showed that the efficiency of the proposed system is lower than the declared one, and its creation is impossible because there is no electromagnetic air valve satisfying the requirements for it in this design.

Designing, modeling, and structural analysis of a newly designed double lobe camshaft for a two-stroke compressed air engine

With the rapid increase of urbanization and industrialization, the energy demand has expeditiously risen. The natural resources are limited and will be extinct in the next few years. If the depletion of fossil fuels continues at the same rate as it is, the world will suffer from severe energy scarcity in the nearer future. Therefore, to reduce the dependency on liquid-based petroleum fuels, there is an urgent need for alternative fuels that could compensate for diesel demand and reduce harmful emissions from the atmosphere. The paper presents the designing, modeling, and analyzing a newly designed double lobe camshaft for a compressed air engine. In this study, a 100-cc Four-Stroke SI engine manufactured by Bajaj Auto, an Indian motorcycle manufacturer, was used and tested on compressed air. The engine was modified from a conventional four-stroke to a two-stroke engine by designing a new camshaft for opening the valves at different timings. The newly designed camshaft contains axisymmetric double lobes on both the inlet and outlet cams. Thus, in one complete revolution of the crankshaft, both the valves open once, resulting in one power stroke and one exhaust stroke, eliminating the compression and intake stroke. Any modifications in the camshaft cause various changes in the stress distribution and deformation along the shaft, which should be studied to provide us vital information about the life and effectiveness of the new modified camshaft. The objective is to determine the new valve lift profile, deformation, and equivalent (Von-Mises) stress under loading conditions on the double lobe camshaft. The designing and modeling of the camshaft are done in SOLIDWORKS 2020, and structural analysis is carried out in ANSYS 2020. The maximum total deformation resulted from the analysis comes out to be 5.72 × 10-4 mm, and the maximum value of equivalent stress evaluated is 31.17 MPa.

The issue of improving the efficiency of nitrogen oxide neutralization systems in diesel internal combustion engines

The most effective method of reducing nitrogen oxides in diesel exhaust gas is selective purification by the SCR-NH3 method. The method uses ammonia released during thermolysis and hydrolysis of a urea solution when it is injected through a nozzle into a neutralizer. This method has a relatively low efficiency of cleaning the exhaust gas from nitrogen oxides. The main factor hindering the achievement of high efficiency of the NOx neutralization system is the insufficiently high temperature during the implementation of this process. The article analyzes various ways to increase the efficiency of the neutralization process and proposes a new method for neutralizing NOx by using urea injection into the cylinders of the internal combustion engine at the expansion stroke in a diesel internal combustion engine. Efficiency can be achieved due to a higher exhaust gas temperature in the cylinder of the internal combustion engine and an increase in the time of the process of thermolysis and hydrolysis of urea. The kinetics of the decomposition of nitrogen oxides, the process of NH3 oxidation, and the calculation of temperature conditions in the cylinder of a diesel internal combustion engine at the exhaust cycle are considered. The experience of neutralization of NOx contained in the flue gases of thermal power plants, where NOx purification takes place at high temperatures without the use of a catalyst, is analyzed. It is shown that the modernization of the SCR-NH3 process, due to the injection of urea at the exhaust stroke in a diesel internal combustion engine, will simplify the existing method of NOx neutralization and at the same time obtain additional advantages for a modern high-speed engine.