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Integrated Gasification Combined Cycle (IGCC) is a technology that integrates the coal gasification and combined cycle to produce electricity efficiently. Due to the fact that the heating value of syngas from coal gasification process is typically lower than that of the natural gas, the conventional gas turbine will have to be adapted for syngas. The nozzle adjustment is the key to the successful transformation since the ignition properties are different between syngas and natural gas which have totally different compositions. The nozzles suitable for natural gas have been prone to partially melting around the flame stabilization holes on sidewalls of the nozzle in real operation. Thus a computational fluid dynamics (CFD) model was constructed for the syngas nozzles as well as combustion chamber of the gas turbine for low heating value syngas to study the thermostability of the nozzle. The detailed structure of the syngas nozzle, the combustion characteristics of syngas, as well as the actual operation condition of the gas turbine were all employed in the CFD model to improve the simulation accuracy. The reason of partially melting of the nozzles suitable for natural gas can be attributed to that the syngas leaked from the flame stabilization holes into the mainstream air can quickly mix with air, adhere to the sidewalls of the nozzles and then ignite around the holes which result in temperatures high enough to melt the material of the nozzle around the holes through CFD simulation. Finally, a new structure of the syngas nozzle was proposed and validated by CFD simulations. The simulation result shows that the flames caused by the syngas leaked from the flame stabilization holes are no longer adhering to the nozzle sidewalls and local high temperature can be lowered by about 30% which will not be able to melt the nozzle material.

The S-shaped characteristic curves in pump-turbines complicate synchronization with the electrical grid and affect system safety. Misaligned guide vanes (MGVs) are one of the most effective solutions to avoid S-shaped characteristics. The internal flow mechanism with the MGV for improving S-shaped characteristics was studied by numerical analysis. Six operating conditions were modeled in the S-shaped region. Four guide vanes were arranged as the MGVs to qualitatively and quantitatively analyze the flow behavior. The internal flow was quite complex at the four operating points without the MGV; here, the attack angle and the flow behavior had no obvious difference at each vane. For the similar conditions with MGVs, attack angles and internal flow fields varied clearly at each vane, especially in the vaneless region and in the runner blade passages. For the same discharge rates, total openings, and rotating speeds, the internal flows were quite different between with and without the MGVs. The MGVs disrupt the high-speed circumferential water ring (appreciably faster compared to the main flow) in the vaneless region and maintain operation with higher unit speeds. Consequently, the unit speed is larger at the same unit discharge in the S-shaped region. Therefore, the MGV method can reduce S-shaped characteristics.

In Pelton turbine, the dispersion of cylindrical jet have a great influence on the energy interaction of jet and buckets. This paper simulated the internal flow of nozzle and the downstream free jet flow at 3 different needle strokes. The nozzle model consists of the elbow pipe and the needle rod which supported by 4 ribs. Homogenous model and SST k-ω model were adopted to simulate the unsteady two-phase jet flow. The development of free flow, including a contraction process followed by an expansion process, was analysed detailed as well as the influence of the nozzle geometry on the jet flow pattern. The increase of nozzle opening results in a more dispersion jet, which means a higher hydraulic loss. Upstream bend and ribs induce the secondary flow in the jet and decrease the jet concentration.

Pelton turbine, which applied to the high water head and small flow rate, is widely used in the mountainous area. During the operation period the sediment contained in the water does not only induce the abrasion of the buckets, but also leads to the erosion at the nozzle which may damage the needle structure. The nozzle and needle structure are mainly used to form high quality cylindrical jet and increase the efficiency of energy exchange in the runner to the most. Thus the needle erosion will lead to the deformation of jet, and then may cause the efficiency loss and cavitation. The favourable prediction of abrasion characteristic of needle can effectively guide the optimization design and maintenance of needle structure. This paper simulated the unsteady three-dimensional multi-phase flow in the nozzle and injected jet flow. As the jet containing water and sediment is injected into the free atmosphere air with high velocity, the VOF model was adopted to predict the water and air flow. The sediment is simplified into round solid particle and the discrete particle model (DPM) was employed to predict the needle abrasion characteristic. The sand particle tracks were analyzed to interpret the mechanism of sand erosion on the needle surface. And the numerical result of needle abrasion was obtained and compared with the abrasion field observation. The similarity of abrasion pattern between the numerical results and field observation illustrated the validity of the 3D multi-phase flow simulation method.