An oscillation model of a single free piston engine generator which is coupled with a linear generator is presented in this paper. Based on the dynamics and energy equilibrium, the oscillation model is described by the mass spring damping system. It demonstrates that the generator could be regarded as a single freedom self-exited vibration system. The excitation is the periodical combustion in the cylinder. And the system reaches a limit loop after several cycles. The frequency and amplitude characteristics with the effects of key variables are shown. It provides a power map as function of the stiffness and mass, which will be applied into the match design and optimization.

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The controller that used to follow the change of load for the single free-piston engine generator is presented here. It aims to achieve the stable operation with the piston oscillation. Based the energy balance equation in consecutive cycles, the kinetic energy of the free piston was described by discrete state functions. According to its error varying with minimums, the following controller was established to set the fuel injection. It was applied into the performance simulation. The results indicate that the controller is available. Due to the discrete characteristic of the energy transfer, the restoration progress has to require two or three cycles at least. And the stroke is increased with the load stepped up. The top dead center position has smaller changes than the bottom dead center. The displacement versus velocity limit loop is bigger than before. It will be used in the prototype design in the experimental research.

A rectangular vessel has two contact surfaces with different materials, iron and copper. In order to investigate thermo-structural characteristics of the vessel, the structural model is developed. The structural analysis is coupled with the thermal condition. The numerical simulation model with hex eight-node thermally coupled brick elements is established and solved by finite element method. The results show that the maximum stress with 112.5 MPa is distributed on the contact surface between the different materials. Because of the different materials’ expansions, there is stress concentration on the contact surface. The maximum displacement is 0.27 mm, almost the same at different pressure loads. The maximum stress increased to about 300 MPa as the temperature increase. The structural response caused by thermal expansion is important for the vessel design.

A numerical simulation model of heat flux sensors embedded in a flat plate is established. Each sensor has four thermal couples and is inserted into the specified hole. The problem is defined as a steady heat conduction problem with specified boundary conditions and solved by the finite element method. The results of the simulation case demonstrate that the maximum heat flux appears near the sensor shell. The average heat flux of the plate is much smaller than the maximum. Due to exiting of the contact heat resistance, the temperature of the sensor is much lower than that of the plate at horizontal surface. The maximum temperature difference appears on the bottom shell of the sensor. The maximum temperature difference between the simulation results and the experimental data at test points is 1.5 K. The model is verified and could be accepted for the further errors analysis.