船用柴油机与燃气轮机动力装置的可靠性对比分析

从关键零部件数量、零部件制造材料、零部件工作条件和部件冗余数量角度,分别对船用柴油机和燃气轮机动力装置的不可靠度进行计算和对比分析。结果表明,柴油机动力装置包含的部件数量大,而燃气轮机动力装置结构相对简单,其结构可靠性高于柴油机动力装置。但对于多缸柴油机来说,由于冗余部件和冗余辅机系统的存在,柴油机动力装置的整体运行可靠性高于燃气轮机动力装置,说明柴油机动力装置的冗余部件对其运行可靠性非常重要。

Effect of tip geometry and tip clearance on aerodynamic performance of a linear compressor cascade

The tip leakage flow between a blade and a casing wall has a strong impact on compressor pressure rise capability, efficiency, and stability. Consequently, there is a strong motivation to look for means to minimize its impact on performance. This paper presents the potential of passive tip leakage flow control to increase the aerodynamic performance of highly loaded compressor blades. Experimental investigations on a linear compressor cascade equipped with blade winglets mounted to the blade tips have been carried out. Results for a variation of the tip clearance and the winglet geometry are presented. Current results indicate that the use of proper tip winglets in a compressor cascade can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction-side winglets are aerodynamically superior to the pressure-side or combined winglets. The suction-side winglets are capable of reducing the exit total pressure loss associated with the tip leakage flow and the passage secondary flow to a significant degree.

Effects of End-Bend and Curved Blades on the Flow Field and Loss of a Compressor Linear Cascade in the Design Condition

Curved blade and end-bend blade are considered as effective passive control methods for improving the aerodynamic performance of a compressor cascade,and their applicability also needs to be further studied.A highly-loaded compressor linear cascade in the design condition was taken as the research objective in this paper.Numerical simulation was used to study the positive and negative effects of these methods on the flow loss of the cascade by redistributing the vortex structures.Results show that:the curved blade could reduce the flow loss to 2.55%,while the end-bend blade and the end-bend+curved blade increase it to 10.58%and 2.19%,respectively.The positive effect of the curved blade weakens the strength and scale of Concentrated Shedding Vortex(CSV),which accounts for 59.2%of the total flow loss.The negative effect of the end-bend blade exacerbates the low-energy fluid clusters from the end wall and wake into CSV.Finally,the end-bend+curved blade can take their own strengths,but it enhances the twisting motion of Passage Vortex(PV)and CSV,which makes it fail to reduce the flow loss.Therefore,the positive and negative effects of these methods on the flow loss of a compressor cascade are much clearer.In addition,we also predict the potential danger of the end-bend blade in the negative incidence conditions and provides some suggestion for future study.

Investigation of the Vortex Dynamic Mechanism of the Flow Losses on a Transonic Compressor Stator

For a transonic axial-flow compressor, the numerical simulations, verified against experimental data, were used to study the inherent correlation between the evolutionary process of the vortex structures and the flow loss in a compressor stator passage during the throttling process. The flow loss was divided accurately and quantitatively, based on the evolutionary process of the vortex structures. According to the position of the singular points of the vortex structures, the influence of the evolution of the vortex structures on the generation and development of the flow loss was analyzed on a microscale scale. Thereafter, this paper provided the vortex dynamic mechanism of the flow loss, which was important to enrich the theoretical system of the flow field in the compressor. The results show that: the flow loss at the top of the stator tip is caused by the low-energy fluid clusters, which are transported and accumulated by the vortices from the endwall; the transport effect of the pressure separation vortex at the upper half-height only migrates the position of the flow losses, but there is new flow loss generated by its shear action to the endwall. The dominant flow loss during the throttling process concentrates upon the closed separation bubble around the middle of the suction side of the stator.

Effect of Winglet Geometry Arrangement and Incidence on Tip Clearance Control in a Compressor Cascade

An experimental study is conducted to investigate the influences of blade tip winglet on the flow field of a compressor cascade. The tests are performed in a low speed linear cascade with stationary endwall, with three blade tip configurations, including the baseline tip, the suction-side winglet tip and the pressure-side winglet tip. The flowfield downstream of the cascade is measured using five-hole probe, from which the three-dimensional velocity field, vorticity field and pressure field are obtained. Static pressure measurements are made on the endwall above the blade row using pressure taps embedded in the plywood endwall. All measurements are made at both design and off-design conditions for tip clearance level of about 2 percent of the blade chord. The results revealed the incidence variation significantly affects the secondary flow and the associated loss field downstream of the cascade, where the tip leakage vortex and passage vortex exist as the major contributors on the field. The winglet geometry arrangements can change the trajectory of the tip leakage vortex. The suction-side winglet tip blade provides a lower overall total pressure loss coefficient when compared to the baseline tip blade and pressure-side winglet tip blade at all incidence angles.

Research on Calculation Method of Aerodynamic Parameters of Supersonic Probe Based on Gas Compressibility Factor

The supersonic multi-hole probe is an essential test tool for wind tunnel experiments, which is necessary to develop the basic research of improving the measurement accuracy and expanding the application of the probes.