Centrifugal Compressor Aerodynamic Design And Analysis Of A Micro Turbo Jet Engine

As a kind of power propulsion system with high energy density ratio,Micro turbojet engine(MTE)is characteristic with high-thrust ratio,small size and high speed,etc.And it plays a vital role in various types of unmanned aerial vehicles,cruise missiles and other mini-aircrafts.Centrifugal compressor has a series of advantages such as wide scope of work,less parts and high reliability;it has been widely used in small and mini aircraft engine.As an air intake provides components of micro turbojet engine,its performance directly affects the working status and dynamic performance of engine,therefore,studies the design method of centrifugal compressor and internal flow state has important scientific significance and application value.This paper studied the design method of centrifugal compressor and its performance at the design point of a micro turbojet engine.The main contents are as follows:1.Combined with the demand of a micro turbojet engine air intake designed a centrifugal compressor pressure which ratio 3.8.Designed the impeller by adjusting theta angle of blade with five times Bezier curve into three forms.By comparing performance curve and the results of numerical simulation obtained that: Using low times of the Bezier curve to adjust blade,the efficiency of impeller can reach more than 0.8;Blade theta angle back speed the way can make the blade working at after loading state which is more advantageous to improve the efficiency of the impeller;Blade Angle acceleration positi on can make the impeller to different scope of work flow direction.2.Selecting theta angle back speed impeller and studied the impeller performance under the different tip clearance situation of 0%,2%,4% blade height.The results show that the existence of the tip clearance will cause impeller leakage flow,and exacerbate the effect of secondary flow,but the existence of the tip clearance can weaken the export of jet.Finished solving mechanics and modal of the high speed impeller.Through the results of deformation and the fixed value high percentage of leaf type space curve,the outline of that percentage high gap selection method is more suitable.Stress analysis found maximum stress is located on the blade root of blade trailing edge,at the bottom of the maximum stress of integral impeller is located in the center hole,stress are calculated in the selected materials of 7A09 within the yield limit of hard aluminum alloy.3.Under the premise of the same impeller and edge blade,studied leaf diffuser outlet and the impeller outlet diameter ratio of 1.05,1.08,1.12,the leaves of diffuser length on the influence of the combination of flow field and performance.Found that the impeller outlet air flow within the leaves diffuser can slow down significantly,and fully mixed reduce non-uniformity.Leaves smaller influence on the internal flow of impeller diffuser,the influences of diffuser radial diffuser,mainly lies in the high speed zone and high speed drafting scope effectively suppressed.4.Under the premise of the same diffuser blade angle,change hub angle and angle of attack is studied in two ways to increase the flow area of five kinds of diffuser.Obtained under different diffuser performance curve,compared the different diffuser in the working point of the internal flow state and different performance parameters.In terms of overall performance hub 5° angle of diffuser outlet pressure ratio and efficiency is the highest.The flow research results show that the appropriate internal expansion are a can improve the compression ratio and efficiency,but the change of angle of attack area increases way cause blade leeward surface flow separation and vortex,making efficiency greatly reduced.The main loss of way to increase the hub angle due to the in crease of import of velocity gradient and after turn period,enters the axial diffuser of flow separation.In this paper,the research results show that in high speed,high pressure and miniature centrifugal compressor internal flow is very complex,throug h the overall performance and flow state of the comprehensive discussion and research,can provide theoretical basis for further studies on transport of centrifugal compressor,the optimization for the centrifugal compressor design for technology accumulation.