The relevance of this article is due to the need for improving indicators of exhaust gas toxicity of diesel engines. One of the modern directions of achieving the required environmental performance of diesel engines is the addition of various nanomaterials to petroleum diesel fuel. The aim of the present study was to investigate the possibility of improving the environmental performance of a diesel engine for a generator set using carbon nanotubes as an additive to petroleum diesel fuel in an amount of up to 500 mg/L. Experimental studies were carried out on a D-243 diesel engine operating in a wide range of loads from idle to full load with the addition of 125, 250, and 500 mg/L of carbon nanotubes in the diesel fuel. The mixing of petroleum diesel fuel with nanotubes was done using an ultrasonic unit. The possibility of improving the environmental performance of the studied diesel engine fueled with carbon nanotube-blended petroleum diesel fuel was examined. Results showed that, in the full-load mode of diesel operation, the addition of 500 mg/L of carbon nanotubes to diesel fuel enabled the engine to reduce exhaust smoke from 26.0% to 11.2% on the Hartridge scale.

Introduction.  High-fidelity simulation of off-road and amphibious vehicle motion relies on accurate wheel-surface interaction models. Although empirical and semi-empirical wheel rolling models (Pacejka, Guo and Lu) are dominant on solid surfaces, their input parameters are often ambiguous and do not have a direct physical interpretation, it is significantly limiting their predictive capabilities under complex, multi-mode driving conditions. Expensive and time-consuming specific sample testing is often required to obtain accurate characteristics. Materials and Methods.  This study presents an experimental validation of a physically based wheel dynamics model for non-deformable supporting surfaces. The mathematical description of the tire model with the use of brush analogy has been previously presented. A laboratory test bench was used as a validation environment to measure wheel kinematics and dynamics under a wide range of vertical loads in both driving and driven modes. Key parameters, including rolling radius, longitudinal slip, and torque have been measured directly on the rig. Results.  Experimental data were used to validate the developed mathematical model, implemented in MATLAB/ Simulink. The model demonstrated match with experiment results in free-rolling mode, with a normalized root-meansquare error (RMS) below 1.2% for the covered distance. In driving mode, the error increased to approximately 10%, which, according to the analysis, is explained by the risen complexity of torque application and slip dynamics. Discussion and Conclusion.  Unlike purely empirical models, all parameters of the developed model have a clear physical meaning and can be determined from a limited set of experiments. It makes this model a preferred choice for problems requiring the behavior prediction under various conditions.

BACKGROUND: The dynamics of multi-axle amphibious wheeled transport and technological vehicles (AWTTV) remain poorly understood, especially under variable grip and extreme driving conditions. Existing studies focus primarily on two- and four-axle vehicles, ignoring complex nonlinear effects of tire slip and interaction between axles, which limit control accuracy for heavy multi-axle vehicles. AIM: Development of a complex mathematical model of AWTTV dynamics that combines torque distribution between axles, real-time correction of wheel steering angles, and consideration of nonlinear effects of slip, to improve stability and handling in transient and extreme conditions. METHODS: The following methods are used in the research: theoretical and analytical study based on the equations of vehicle dynamics, simulation modeling of the motion of an AWTTV with an 8x8 wheel arrangement, comparative analysis of two steering schemes (1-2-0-0 and 1-2-3-4), assessment of the influence of velocity, acceleration and steer angles on stability, verification of the model by means of the analysis of steady-state and transient modes. RESULTS: It was found that the difference in the slip angles of the outer axles increases proportionally to the velocity and the steer angle, reaching 10 degrees at a velocity of 40 km/h. Deviation from the specified path for the 1-2-0-0 scheme reaches 40%, which is 1.6 times higher than for the 1-2-3-4 scheme. In transient modes, an increase in the difference in slip angles by 15-20% was observed compared to the steady-state mode. CONCLUSION: The proposed model demonstrates that the integration of torque distribution and active steering reduces the path deviation and improves the stability of the AWTTV. The results highlight the need for adaptive algorithms for multi-axle vehicles, especially in transient conditions.

BACKGROUND: Amphibious wheeled transport and technological units (AWTTU) are critically important for rescues and other special operations, but their velocity in water is limited due to high wheel resistance and suboptimal hydrodynamics. Existing studies do not take into account the hydroplaning mode in a comprehensive manner. AIM: Development of a mathematical model of the motion in water of an amphibious vehicle in the hydroplaning mode, which takes into account both hydrostatic and hydrodynamic forces. METHODS: Equations for determining excess pressure on the hull surface are derived based on the Cauchy-Lagrange integral, a calculation scheme for the interaction of a flat-bottomed hull with the water surface is developed. Analytical expressions for the lifting hydrodynamic force, resistance force, and hydrodynamic moment are obtained. An analysis of the stability of motion is carried out taking into account the position of the center of gravity, the magnitude of the traction force of the watercraft propeller, and the trim angle. RESULTS: It was found that at Froude numbers Fr 3.0, hydrodynamic forces ensure 95–97% of sustaining the AWTTU afloat. The criteria for the motion stability are obtained: with a negative arm of the propulsion force, the stability depends on the magnitude of the thrust, with a positive arm, the critical speed of motion is determined. It was found that the thickness of the “reverse jet” is proportional to the angle of attack, the resistance force has a quadratic dependence on the velocity, the arm of the hydrodynamic moment is linearly dependent on the trim angle. CONCLUSION: The developed mathematical model allows analyzing the motion of the AWTTU in the hydroplaning mode taking into account key hydrodynamic factors. The obtained results create a theoretical basis for the design of high-velocity amphibious vehicles and require further experimental validation.