STUDY OF THE EFFECT OF FEED PRESSURE AND NOZZLE CHANNEL CROSS-SECTIONS ON FUEL SUPPLY PROCESSES IN GAS-DIESEL LOW-SPEED TWO-STROKE LOW-PRESSURE ENGINES

The use of gas fuels for marine two-stroke low-speed internal combustion engines is considered by the International Maritime Organization as the main tool for implementing the program adopted in 2018 to reduce greenhouse gas emissions by half by 2050 compared to 2008. In this regard, the world's leading manufacturers of this type of engines are actively engaged in research and development work aimed at developing, designing, manufacturing and putting them into operation. In this class of engines, there are a number of limitations that do not allow the existing experience of converting four-stroke marine engines to gas fuel to be applied to them. In this regard, each manufacturer develops its own approaches to solving this problem. As a result, two fundamentally different approaches were outlined - this is the supply of gas fuel directly to the working cylinder at the beginning and at the end of the compression stroke. Each of these methods has its own advantages and disadvantages. Earlier, the authors showed that in addition to the already implemented technical solutions, other approaches can be used related to the supply of gas fuel into the working cylinder under a pressure of 4.0...6.0 MPa, which allow combining the advantages of both methods implemented in practice and significantly reduce their inherent disadvantages. In particular, reducing the residence time of the gas-air mixture in the working cylinder of the engine during the compression stroke is an effective method of combating knocking combustion that occurs in low-pressure engines. In turn, this time depends on the pressure under which the gas fuel is supplied to the gas supply module and on the characteristics of its outflow through the flow path of this device. This article is devoted to the study of the influence of the design features of the flow path on the formation of the trajectories of gas fuel movement and the parameters of its outflow from the gas module to the working cylinder under conditions of changing back pressure.

Pneumatic spring with internal and external air throttling at the compression and rebound strokes

The design and method of calculating the elastic characteristics of a pneumatic spring with internal and external air throttling during compression and rebound strokes are presented. Calculations of the elastic characteristics with and without the internal volume of the pneumatic spring piston are proposed. Keywords: suspension, internal and external air throttling, pneumatic spring, rebound stroke, compression stroke, rubber-cord casing [email protected], [email protected], [email protected]

Turbulence Anisotropy Investigations in an Internal Combustion Engine

The assumption of isotropic turbulence is commonly incorporated into models of internal combustion engine (ICE) in-cylinder flows. While preliminary analysis with two-dimensional velocity data indicates that the turbulence may tend to isotropy as the piston approaches TDC, the validity of this assumption has not been fully investigated, partially due to lack of three-component velocity data in ICEs. In this work, the velocity was measured using two-dimensional, three-component (2D-3C) particle image velocimetry in a single-cylinder, motored, research engine to investigate the evolution of turbulence anisotropy throughout the compression stroke. Invariants of the Reynolds stress anisotropy tensor were calculated and visualized, through the Lumley triangle, to investigate turbulence states. Results showed the turbulence to be mostly anisotropic, with preferential tendency toward 2D axisymmetry at the beginning of the compression stroke and approaching isotropy near top-dead-center. Findings provide new insights into turbulence in dynamic, bounded flows to assist with the development of physics-based, quantitative models.

Compressor type engine brake

The accident rate in road transport remains unacceptably high, and in order to reduce it, it is nec-essary to take into account all the factors affecting this process. In this regard, the process of long-term braking deserves special attention, which negative processes require the creation of additional braking systems (retarder brakes) for vehicles operating in mountainous areas, primarily in the field of passenger transportation. Transmission retarder brakes that provide sufficient braking performance have a number of dis-advantages that inhibit their use. Existing engine retarder brakes provide insufficient deceleration, and studies were carried out at the Kuban State Agrarian University (KubSAU) to improve their efficiency. After a theoretical analysis, the compressor brake mode was experimentally investigated. The in-creased pressure was created in the intake manifold and at the end of the compression stroke, air from the cylinder was released through a special valve back into the system, due to which the brak-ing effect was created. The carried out experiments confirmed the possibility of a significant increase in the engine braking torque in the compressor brake mode, when both valves are closed - the exhaust after the exhaust manifold and the intake in front of the carburetor, and compressed air is supplied to the in-take manifold at different pressures. Then the braking torque increases in comparison with engine braking by more than 3 times.

Pneumatic spring with internal and external air throttling at rebound

The design and method for calculating the elastic characteristics of a pneumatic spring with internal and external air throttling during rebound are presented. The calculation of the elastic characteristics is carried out both with and without taking into account the internal volume of the piston of the air spring. Keywords: suspension, internal and external air throttling, air spring, rebound stroke, compression stroke, rubber-cord casing. [email protected], [email protected], [email protected]

Deep feature learning of in-cylinder flow fields to analyze cycle-to-cycle variations in an SI engine

Machine learning (ML) models based on a large data set of in-cylinder flow fields of an IC engine obtained by high-speed particle image velocimetry allow the identification of relevant flow structures underlying cycle-to-cycle variations of engine performance. To this end, deep feature learning is employed to train ML models that predict cycles of high and low in-cylinder maximum pressure. Deep convolutional autoencoders are self-supervised-trained to encode flow field features in low dimensional latent space. Without the limitations ascribable to manual feature engineering, ML models based on these learned features are able to classify high energy cycles already from the flow field during late intake and the compression stroke as early as 290 crank angle degrees before top dead center ([Formula: see text]) with a mean accuracy above chance level. The prediction accuracy from [Formula: see text] to [Formula: see text] is comparable to baseline ML approaches utilizing an extensive set of engineered features. Relevant flow structures in the compression stroke are revealed by feature analysis of ML models and are interpreted using conditional averaged flow quantities. This analysis unveils the importance of the horizontal velocity component of in-cylinder flows in predicting engine performance. Combining deep learning and conventional flow analysis techniques promises to be a powerful tool for ultimately revealing high-level flow features relevant to the prediction of cycle-to-cycle variations and further engine optimization.

Numerical assessment of ozone addition potential in direct injection compression ignition engines

This paper aims at taking into account the chemistry of O3 in a 3D CFD simulation of compression ignition engine with Diesel type combustion for low load operating points. The methodology developed in this work includes 0D homogeneous reactors simulations, 3D RANS simulations and validation regarding experimental results. The 0D simulations were needed to take into account O3 reactions during the compression stroke because of the high reactivity of O3 with NO and dissociation at high temperature. The values found in these simulations were used as an input in the 3D model to match the correct O3 concentration at fuel injection timing. The 3D simulations were performed using CONVERGETM with a RANS approach. Simulations reproduce the compression/expansion stroke after the intake valve closure to focus on the impact of O3 on the fuel auto ignition. The comparison between numerical and experimental results demonstrates that the proposed methodology is able to capture correctly the impact of O3 addition on ignition delay and on heat release. Moreover, the analysis of the data enables to better understand the fundamental processes driving O3 impact in a CI engine. In particular, using 0D simulations, the plateau effect observed experimentally when increasing O3 concentration is attributed to O3 thermal decomposition and reaction with NO during the compression stroke. Also, 3D CFD results showed that O3 impact is observed mainly during LTHR phase and does not affect the topology and the propagation of the flame inside the combustion chamber.