We examined how the composition ratio of P 2 O 5 to TeO 2 affected the physical properties and the structure of the semiconductive vanadate glasses in a low-melting V 2 O 5 P 2 O 5 TeO 2 glass system containing 57 mol % V 2 O 5 . It was found that increasing the P 2 O 5 content and correspondingly decreasing the TeO 2 content raised the glass transition temperature and the deformation temperature as well as the fraction of the reduced V ions ([V 4+ ]/[V total ]) and the average interionic distance of the V ions. In addition, the increase in P 2 O 5 content from 7 to 32 mol % lowered the thermal expansion coefficient, volume resistivity, and density by 27, 42, and 14%, respectively, and also lowered the apparent molar volume of O ions and crystallization tendency. Furthermore, the infrared (IR) spectra suggested that the TeO 2 -enriched glasses had a layered structure similar to crystalline V 2 O 5 , whereas the P 2 O 5 -enriched glasses had a denser layered structure as a result of the increased packing density of the O ions due to the reduction of the V ions.

No abstract

No abstract

Gasoline Direct Injection Homogeneous Charge Compression (GDI-HCCI) combustion is achieved by closing early the exhaust valves for trapping hot residual gases combined with direct fuel injection. The combustion is chemically controlled by multi-point auto-ignition which its main combustion phase can be controlled by direct injection timing of fuel. This work investigates the effect of single pulse injection timing on a supercharged GDI-HCCI combustion engine by using a four-stroke single cylinder engine with a side-mounted direct fuel injector. Injection of primary reference fuel PRF90 under the near-stoichiometric-boosted condition is studied. The fuel is injected during negative valve overlap (NVO) or recompression period for fuel reformation under low oxygen concentration and the injection is retarded to intake stroke for the homogeneous mixture. It is found that the early fuel injection in NVO period advances the combustion phasing compared with the retarded injection in the intake stroke. Noticeable slower combustion rate from intake stroke fuel injection is obtained compared with the NVO injection due to charge cooling effect. Zero-dimensional combustion simulations with multiple chemical reaction mechanisms are simulated to provide chemical understanding from the effect of fuel injection timing on intermediate species generations. The species such as C2H4, C3H6, CH4, and H2 are found to be formed during the NVO injection period from the calculations. The effects of single pulse injection timings on combustion characteristics such pressure rise rate, combustion stability, and emissions are also discussed in this study.

No abstract