Abstract: Thermal fatigue tests were conducted on diesel engine cylinder heads of gray cast iron HT250 with conductive heating fatigue test rig. The thermal fatigue life is affected by the maximum temperature and heating time. The relationship between thermal fatigue life, temperature, and heating time was researched. Thermal fatigue life prediction model was derived from classical energy fatigue criteria. The parameters of the model were obtained from the results of the thermal fatigue test. The model and thermal fatigue test method are suitable for cylinder heads of cast irons and cast aluminum alloys, the parameters should be fixed by thermal fatigue test.
Abstract: In this research, the non-linear thermo-mechanical simulation, experimental study and lifetime prediction of engine exhaust manifold were systematically analyzed. Fluid-structure coupled method was employed in the simulation. Heat transfer analysis simultaneous considered radiation, convection and conduction. Inelastic properties of the materials used for the thermo-mechanical analysis included kinematic hardening and creep. Some models were introduced and used to predict lifetime of the manifold. Temperature data obtained during the engine bench tests can be accurately matched with the analysis results. The results indicated that the highest temperature located on the confluence of exhaust manifold and the plastic dissipated energy field caused by the cyclic thermal loading can be matched with the crack zone of exhaust manifold.
Abstract: Experiments of the valve bridge are carried out and the boiling states are investigated, to study the boiling heat transfer in cylinder head jacket. The effects of inlet flow rate and temperature on boiling heat flux are analyzed, as well as the thickness of fire deck. The results show that the inlet velocity has little effect on the velocity in valve bridge zone, even the velocity in the valve bridge zone can strongly affect on boiling heat transfer. The results can offer references to practical application in power-enhanced diesel engine.
Abstract: A preconcentration method based on the adsorption of palladium-dimethylglyoxime -anchored organobentonite (DMG-bentonite) for the determination of palladium at trace levels by flame atomic absorption spectrometry (AAS) has been developed. The optimum experimental parameters for the adsorption and preconcentration of the palladium, such as pH value of medium, contact time, eluent and coexisting ion, have been investigated. The results showed that the palladium ion could be quantitatively retained by the DMG-bentonite in the pH range of 3–5 using citric acid/citrate buffer, the adsorption time was 20 min, and capability of adsorption was 8.73 mg•g-1. The palladium ion adsorbed on the DMG-bentonite could be completely eluated by using 1 mol•L-1 HCl. The detection limits of this method for palladium was 1.02µg•L-1 with an enrichment factor of 60. The method has been applied to the determination of trace amounts of palladium ion in street dust and environmental water with satisfactory results.
Abstract: The performance of a single-chamber pneumatic spring and a dual-chamber pneumatic spring have much difference. Dynamical models of these two types pneumatic springs were built and the characteristics of them were analyzed in this paper. Based on the theory of engineering thermodynamic, gas state equations were established and the dynamical models were obtained. The results show that: the single-chamber pneumatic spring can be equivalent to three stiffness springs in parallel and the dual-chamber pneumatic spring can be equivalent to a stiffness spring and a damping in series, then connect with three stiffness springs in parallel. The stiffness and natural frequency are main influenced by chamber pressure, effective area, volume of the chamber, displacement. The stiffness increases with the chamber pressure increasing and decreases with the volume of the chamber increasing. Such an accurate model for the pneumatic springs would contribute to more effective design or control of vibration isolation systems.
Abstract: The biosorption of Acid Red R, from aqueous solutions by acid treated Penicilium sp. was studied in a batch mode. Operating variables like contact time, pH and initial dye concentration was investigated. The acid treated biomass exhibited maximum dye uptake at initial pH value of 3. The dye adsorption by the biomass was rapid process and the equilibrium was established in 60 min for 50 mg/L of initial dye concentration. Biosorption equilibrium data were fitted very well to the Langmuir as well as to the Freundlich adsorption model. According to the Langmuir model, the monolayer biosorption capacity of Penicillium sp. biomass was found to be 312.5 mg/g for Acid Red R at temperature of 30°C. The results indicate that the acid treated Penicilium sp. biomass can be used as an effective biosorbent to remove Acid Red R from aqueous solution.
Abstract: The objective of this study is to investigate the deformed configuration and free vibration around the deformed configuration of clamped buckled beams by co-rotational finite element formulation. The principle of virtual work, d'Alembert principle and the consistent second order linearization of the nonlinear beam theory are used to derive the element equations in current element coordinates. The governing equations for linear vibration are obtained by the first order Taylor series expansion of the equation of motion at the static equilibrium position of the buckled beam. Numerical examples are studied to investigate the natural frequencies of clamped buckled beams with different slenderness ratios under different axial compression.
Abstract: The environment of Venus surface is extremely harsh, while the lower attitude atmosphere is similar to the Earth's stratosphere, so the balloons can be exploited extensively for Venus exploration. First, the Venus atmospheric environment is described with mathematical model. And the Venus balloon thermodynamic model is established. Then, the floating process of a helium prototype balloon, whose floating altitude is 35 km, is numerically examined by this model. The results show that (1) Wherever the Venus balloon releases at the altitude between 30km and 40km, it could reach floating altitude quickly and keep long-term floating; (2) The balloon system temperature should endure the temperature between 440 K and 520 K; (3) Its instantaneous maximum speed is less than 10 m/s.
Abstract: In numerous engineering systems it is essential to know the vibrational behavior. Often laser vibrometers are used for vibration measurements. But this point should be considered that method utilization because of complex volume of source of vibration is difficult. To alleviate this problem several other methods were recommended such as Near Field Acoustical Holography and Inverse Numerical Acoustics. Vibrational properties knowledge helps in design, control and reduce undesirable vibration, but direct measurement is difficult and contain significant errors. The aim of this paper is the presentation of an efficient method using acoustics that can obtain vibrational properties by measuring other quantities, like fluid pressure dynamics somewhere near the structure. This procedure is based on inverse analysis that is more intricate than direct analysis.