Optical screening investigations of backfire in a large bore medium speed hydrogen engine

Further improvement of hydrogen combustion in port fuel injection engines is limited by backfire. To overcome this drawback of hydrogen port fuel injection engines it is essential to locate and understand the reasons for the inflammation of a backfiring cycle. To contribute to this understanding a minimal invasive lateral optical access was developed for a medium speed large bore engine. The access uses a UV enhanced endoscope to investigate the OH radical’s natural chemiluminescence to locate the inflammation of a backfiring cycle in the combustion chamber. The investigations are carried out at high engine load. The optical investigations were based on a thermodynamic screening. This included the variation of the start of the hydrogen port fuel injection and the engine’s backpressure. These experiments prove the influence of exhaust backpressure and the start of injection on the probability of backfire. As higher backpressure leads to an increased probability of backfire, the SoI strategy has also a decisive influence. An optimum start of injection timing with less backfire under high backpressure was experimentally determined at 300°CA with respect to 720°CA as FTDC. The conducted optical investigations show that backfire starts by ignition by hot residual gasses during the first cycle located under the exhaust valves. Furthermore, the results show ongoing combustion in the intake manifold leading to serious damage of the engine if not prohibited.

Investigation of Valvetrain Dynamics Using Transient Dynamic Simulation in ANSYS

Engine valvetrain is one of the complex mechanisms in internal combustion engine as it involves many components namely, cam, pushrod, rocker lever, crosshead, intake and exhaust valves etc. Due to many components, their interactions with each other and presence of valve lash makes the system complicated to simulate. Typically, engine system level valvetrain dynamic simulation is performed in 1D software. Aim of this study is to understand the physics governing interactions and motion of the components in the valvetrain. This is done by simulating an inline 6-cylinder engine valvetrain mechanism through transient dynamic analysis in Ansys. This paper describes an approach used to simulate the valvetrain mechanism in Ansys and associated learnings. Finite Element Analysis model considers actual stiffnesses of all components. Appropriate joints/contacts are used to model the interactions. The comparative assessment of the valvetrain forces between Ansys results and 1D simulation results shows a good match. Further, 3D simulation in Ansys captures the key characteristics of valvetrain like crosshead tilting, uneven valve actuations and closing. It is also able to predict uneven contact and polishing observed on valve tip face. Overall, this study helped to ascertain the validity of 3D FEA method. This method also enhances the understanding of the valvetrain dynamics which can be helpful in further design improvements. This paper also includes a discussion on further steps to improve analysis model to make it more realistic e.g. including hot valve lash, valve seat wear etc. These improvements will help to understand effects of valve lash on valve velocities, sudden impact loads on valves, valve stresses/fatigue, pushrod buckling etc.

Reduced Scale Laboratory for Training and Research in Condition-Based Maintenance Strategies for Combustion Engine Power Plants and a Novel Method for Monitoring of Inlet and Exhaust Valves

This paper presents the practical aspects of development of a reduced scale laboratory and a set of monitoring tools for Internal Combustion Engines used in Thermal Power Plants. The reduced scale laboratory is based on the necessity of researchers to test new sensors and monitoring strategies that, otherwise, are seldom allowed to be installed in real plants without certification. In addition, the reduced scale laboratory allows the flexibility to insert failures on purpose, in order to evaluate the performance of new sensors/strategies in a safe and controlled environment. The paper also presents the development of a set of reduced cost sensors for monitoring in-cylinder pressure, crank angle, and the position of inlet and exhaust valves (without using ultrasound sensors, which may produce noisy readings on engines operating on gas-diesel fuel mode).

Practical Aspects of Cylinder Deactivation and Reactivation

Cylinder deactivation is an effective measure to reduce the fuel consumption of internal combustion engines. This paper deals with several practical aspects of switching from conventional operation to operation with deactivated cylinders, i.e., gas spring operation with closed intake and exhaust valves. The focus of this paper lies on one particular quantity-controlled stoichiometrically-operated engine where the load is controlled using the valve timing. Nevertheless, the main results are transferable to other engines and engine types, including quality-controlled engines. The first aspect of this paper is an analysis of the transition from fired to gas spring operation, and vice versa, as well as the gas spring operation itself. This is essential for mode changes, such as cylinder deactivation or skip-firing operation. Simulation results show that optimizing the valve timing in the last cycle before deactivating/first cycle after reactivating a cylinder, respectively, is advantageous. We further show that steady-state gas spring operation is reached after approximately 6 s regardless of the initial conditions and the engine speed. The second aspect of this paper experimentally verifies the advantage of optimized valve timings. Furthermore, we show measurements that demonstrate the occurrence of an unavoidable torque ripple, especially when the transition to and from the deactivated cylinder operation is performed too quickly. We also confirm with our experiments that a more gradual mode transition reduces the torque drop.

NUMERICAL ANALYSIS OF VALVE STRUCTURE OF HIGH POWER MARINE ENGINE

Valve as an important part of the gas distribution mechanism, is an crucial part of the engine. When the engine works, the valve is subjected to high temperature, high impact, frictional wear and corrosion and other harsh working conditions, and the reliable and durable valve has an important impact on the safety and reliability of the engine. In this paper, a model of four-stroke marine diesel engine valve is used as the research object, and the intake valve set and exhaust valve set models are established respectively. Heat transfer simulation and failure analysis of inlet and exhaust valves of different structures and materials under different operating conditions were carried out using finite element analysis. The results show that the different valve structures and manufacturing materials have different effects on the reliability of the valves; Changing the valve structures and choosing different valve manufacturing materials have a greater impact on the heat transfer and deformation, thus affecting the overall reliability of the valves.

Increasing the reliability of electronically controlled marine diesel parts

Эксплуатации судовых малооборотных дизелей с электронным управлением свидетельствует о том, что со временем появляются повреждения и отказы, связанные с естественными износами пар трения, особенно прецизионных, в силовой гидравлической системе (СГС), топливных насосах высокого давления и форсунках, а также выпускных клапанах с гидравлическим приводом. Фирмы изготовители судовых малооборотных дизелей для улучшения эксплуатационных показателей и повышения ресурсов указанных деталей широко используют новые более износостойкие и жаропрочные материалы, такие как высокоуглеродистые легированные стали, нержавеющие стали, сплавы на основе кобальта – стиллиты, сплавы на основе никеля – нимоники и инконели, в частности для выпускных клапанов. Такое решение позволяет повысить надёжность деталей, увеличить межремонтные периоды и гарантировать более длительный срок службы, одновременно снизив эксплуатационные затраты, несмотря на некоторое повышение стоимости этих деталей. Приведены характеристики указанных материалов ожидаемые и подтвержденные данные об увеличенных межремонтных интервалах. The operation of low-speed marine diesel engines with electronic control indicates that over time, damage and failures appear associated with natural wear of friction pairs, especially precision ones, in the power hydraulic system, high-pressure fuel pumps and injectors, as well as hydraulically operated exhaust valves. Engine makers / manufacturers in the due course of marine low-speed diesel engines performance improvement and enhancement sourced the way to extend the lifetime for these parts by utilizing modern highly reliable wear-resistant and heat-resistant materials, including high-percentage carbon steels, stainless steels, cobalt-based alloys - stillites, nickel-based alloys - nimonic and inconel, in particular for exhaust valves. This solution allows to increases the reliability of parts, extend “in between the overhaul” periods and guarantees longer service life, and at the same time to lower the operating costs, despite a slight increase in the initial investments related to the higher cost of these parts. The characteristics of the above materials are listed and the service data related to between the overhaul periods are included.

Thermal Profiling of Cooled Radial Turbine Wheel

Compliance with incoming new emission standards such as Euro6d and China6b will require new approaches to the design of thermally loaded automotive components e.g. turbochargers, exhaust valves and manifolds. However, the validation of those new designs and the need for a rapid market entry will require new temperature measurement technologies to provide accurate data across the entire component. A limited number of techniques are currently available, and all have limitations in the harsh operating conditions of turbomachinery. A new technique, called Thermal History Paint (THP), has been developed to overcome these limitations to enable accurate temperature profiles to be recorded in harsh environments. There are limited publications that cover the use of this technique and this paper demonstrates the capability of the THP through the implementation on turbocharger turbine wheels. A cooled, hollow radial turbine wheel was designed, manufactured via 3D printing and tested. A solid wheel of the same external dimensions was manufactured and tested under the same conditions to act as a baseline. The THP was used to measure the temperature profile of the blade surfaces and to quantify the effectiveness of the cooling. The paint exhibited good durability through the tests of both wheels in a hot gas rig at the University of Bath. Specific calibration data were generated for the test and the repeatability of the measurements was determined to be within 8K. Both the cooled and baseline wheels were measured at many locations and the THP recorded a significantly higher temperature on the baseline solid wheel. The measured temperature profiles were in good agreement with expectation and CFD simulations. The results enable the validation of thermal models and demonstrate the capability of the new measurement technique.

Camshaftless Technology on Internal Engines

Along with the development of internal combustion engines, camshafts have also been developed to optimize engine performance. In all types of internal combustion engines, the crankshaft is connected to the camshaft via a toothed belt, chain or pinion. When the crankshaft turns, the camshaft spins and opens and closes the intake and exhaust valve respectively. However, in this non-camshaft engine technology, each intake and exhaust valve will be integrated with an electronically controlled hydraulic pump unit. This system provides a unique ability to independently control intake and exhaust valves. For any engine load, load and discharge times can be programmed independently. The decision system is based on driving conditions, used to maximize performance or minimize fuel consumption and emissions. This allows a greater degree of control over the engine which in turn provides significant performance benefits. This article presents reviews of camshaftless technology developed by VALEO. It is a system that uses solenoid valves to open and close the valve. The solenoid valve will be mounted right on top of the valve inside the engine. The author can see that the technology using this electronic control valve will help reduce the fuel consumption of the engine.