To investigate the influences of thermal and pressure loads on the structural deformation of the Liquid Oxygen/Methane rocket engine combustion chamber, a complete thermo-structural analysis scheme including fluid-thermal analysis and structural finite element analysis is developed and then verified to be reasonable. By conducting fluid-thermal analysis, the detailed distribution of the thermal and pressure loads is obtained. These results are utilized as body loads and surface loads in structural finite element analysis. Then, the stress-strain responses of the combustion chamber and the accumulation process of the deformation induced by thermal and pressure loads were studied in detail. The main conclusions are as follows: Under the action of thermal loads alone, the most pronounced residual mechanical strain is at the upstream of the nozzle divergent segment. Reducing the temperature difference between the hot run and the pre-cooling phase can be a feasible improvement measure for this issue. Under the action of the pressure loads alone, the bottom of the cooling channel bends toward the centerline of the combustion chamber. Properly increasing the thickness of the channel bottom near the coolant inlet is deemed to be an effective measure to reduce this bending trend. Under the combined action of thermal and pressure loads, the structural deformation characteristics are determined by the combination of thermal loads and pressure loads, rather than mainly by thermal loads. The accumulation rate of mechanical strain at the channel bottom corner is much rapider than the other positions. Turning the sharp bottom corner of the cooling channel into rounded corner is an alternative method of suppressing strain accumulation.
Nanofluids which act as coolants in various thermal applications have been promising in accomplishing the primary objective of heat transfer. However, the impact of such fluids on flow lines in the form of enhanced friction factor through unacceptable viscosity rise is an issue to be addressed. On the other hand, these fluids are expected to deteriorate the environment when used or disposed. Hence this research focuses on preparing a bionanofluid and investigating on its primary properties, the thermal conductivity and viscosity. The bionanofluid is prepared by dispersing neem (azadirachta indica) assisted zinc oxide nanoparticles in a binary mixture of ethylene glycol-water (50:50 by volume), at volume concentrations of φ=0.05, 0.2 and 0.5%. To compare the properties of these bionanofluids, additional nanofluids were prepared by dispersing combustion derived pure zinc oxide at same volume concentration. By XRD analysis, the average crystallite size of neem assisted ZnO and pure ZnO was found to be 36 nm and 32 nm. Based on the SEM images, the particles were found to be much closely packed in bioparticles than combustion derived ones. The zeta potential of the nanofluids was found to be ±30 mV at pH 6.5, at which the stability is deemed excellent. The thermal conductivity and viscosity of the nanofluids were measured under varying volume concentration and temperature ranging between 20oC and 50oC. Though the thermal conductivity of the conventional ZnO nanofluid is 3.8% higher than the ZnO bionanofluid, the viscosity is 2% lower for the latter than the former, which is highly expected from any nanofluid for an efficient thermal transport.
Indonesia has implemented a policy of using diesel fuel containing 20 percent biofuel (commonly known as B20 biodiesel), as stated in Energy and Mineral Resources Ministerial Decree No. 23/2013. This study investigated the flame-spread characteristics of biodiesel (B20) in a microgravity environment through drop tower facilities. This is due to the difficulty in creating droplet sizes similar to the real liquid sprays in the combustion chamber of diesel engines. The experiment used biodiesel (B20) droplets with a diameter 1 mm. The results show that the biodiesel (B20) droplets have characteristics of a flame–spread limit distance SBC/dC0limit = 7. This paper discusses the characteristics of biodiesel (B20) droplets in detail.