The engine cooling system must be able to match up with the stable operating conditions so as to guarantee the engine performance. On the working cycle level, however, the dynamic thermo-state of engines has not been considered in the cooling strategy. Besides, the frequent over-cooling boiling inside the gallery changes the cooling capacity constantly. It is necessary to study the coupling effect caused by the interaction of cooling flow and in-cylinder combustion so as to provide details of the dynamic control of cooling systems. To this end, this study develops a coupled modeling scheme of the cooling process considering the interaction of combustion and coolant flow. The global reaction mechanism is used for the combustion process and the multiphase flow method is employed to simulate the coolant flow considering the wall boiling and the interphase forces. The two sub-models exchange information of in-cylinder temperature, heat transfer coefficient, and wall temperature to achieve the coupled computation. The proposed modeling process is verified through the measured diesel engine power, in-cylinder pressure, and fire surface temperature of cylinder head. Then the effects of different cooling conditions on the cyclic engine performances are analyzed and discussed.

Within 30Hz, the discomfort caused by whole-body vibration in rotational direction is higher than vertical vibration at similar equivalent magnitude. Roll vibration, in particular, produces greater discomfort comparing with pitch and yaw vibrations. It is critical to understand the biodynamic characteristics of seated human body under roll vibration for both comfort assessment and vibration control. Experiments are carried out to obtain the biodynamic response of seated human body under random roll vibrations at four r.m.s. magnitude levels. It is found that the principal resonance in the roll apparent inertia is about 1Hz, but varied from 0.7 to 1.5Hz depending on the magnitude of vibration (0.5 to 2.0rad/s²), and the secondary resonance locates around 3Hz with a much lower modulus. It is noted that the human response to roll vibration has some features in common with that in the lateral direction. Two lumped parameter models are developed and calibrated to study the correlation between the two excitation axials. The equivalent relationships of magnitude and phase between roll and lateral vibrations are obtained on condition that they produce similar rotational responses of the upper human body. It suggests an equivalence approach between translational and rotational vibrations that can benefit the comfort assessment when exposed to multiaxial excitations.

Bubble diameter is important for the three-dimensional nucleate boiling two-phase flow simulation. However, the bubble diameter is rarely considered as a variable because it is difficult to estimate. In this paper, a novel bubble diameter model is proposed for the boiling flow. The heat transfer growth, the breakup or coalescence of collision and the liquid impacting separation are considered as the factors affecting the bubble diameter, and three bubble diameter sub-models are developed to calculate the overall bubble diameter based on a departure diameter. In the model, the heat transfer growth is calculated after estimating the bubble location. The collision variation is deduced from the interfacial area concentration equation. The liquid impacting variation is calculated through phase interaction force and gas viscous force. The proposed model is conducted through global information searching in the flow boiling simulation and validated using the void fraction and temperature data from the literature. The effects of the heat transfer growth, the collision, and the separating volume on the bubble diameter are discussed.

The ride comfort and the cargo safety are of great importance in the vibration design of heavy‐duty vehicle. Traditional ride comfort design method based on the response of components of vehicles or interaction between human and seat overlooks the most direct criterion, the response of occupants, which makes the optimisation not targeted enough. It will be better to conduct the ride comfort design with the biodynamic response of driver. To this end, a 17‐degrees‐of‐freedom (DOFs) vertical‐pitch‐roll vehicle dynamic model of a three‐axle heavy‐duty truck coupled with a 7 DOFs human model is developed. The ride comfort of human body under the vertical, the pitch, and the roll vibrations can be evaluated with the weighted root‐mean‐square (r.m.s.) acceleration of the driver in multiple directions. The flexibilities of chassis and carriage are also considered to improve the accuracy of the prediction of the ride comfort and to constrain the mounting optimisation of cab and carriage. After validation, the sensitivity analysis of the mounting system, the suspensions, and arrangement of sprung masses is carried out and significant factors to ride vibration are identified. The optimal combination of design parameters is obtained with the objective of minimizing the vibration of the driver and carriage simultaneously. The optimisation result shows that the weighted driver vibration is reduced by 27.9% and the carriage vibration is reduced by 31.8% at various speeds.