Flow Control Of A Centrifugal Compressorfor Internal Combustion Engine Operating At Various Altitude Conditions

The altitude of China is higher in the west and lower in the east over a wide range.As the contacts of east-west China become more and more frequently, speciallyreinforced investigation of centrifugal compressor overall performance is in progress toenhance the ability of the internal combustion engine (ICE) operating at various altitudeconditions. The turbocharging system is matched at a fixed altitude traditionally. Whenthe operating altitude changes leading to different inlet pressure, the engine operatingline deviates from the matching line and its performance declines greatly. To improveengine performance on overall operating conditions becomes more prominent for engineoperating at various altitude conditions.The compressor performance of ICE operating at various altitude conditions ispoor at off-design point, and it’s unable to meet the demand for high performance of allaltitude conditions. According to this key problem, centrifugal compressor flowparameter’s difference field analysis and control method was developed to improve theoverall performance of ICE operating at various altitude conditions. Based on theinvestigation on the compressor performance requirement of engine operating at variousaltitude conditions, the flow parameter’s difference field and control method werestudied. The thesis work mainly contains the following contents:Based on the experiment studied of a diesel engine external characteristic andcompressor performance operating at different altitude conditions, the deflection of thematching line of the ICE and compressor was studied. The compressor performancerequirements was investigated and the evaluation principle of compressor operating atvarious altitude conditions was brought out.The compressor flow field of ICE’s maximum torque point at sea level and highaltitude was separate into the flow field of the design point and the parameter’sdifference flow field. Analysis model and design method of compressor operating atvarios altitude conditions were established. Based on the investigation of parameter’sdifference flow field, the parameter’s difference of compressor blade’s tip area leads tothe bad compressor performance of different altitude conditions.The method of controlling compressor parameter’s difference flow field of ICE’s maximum torque point at sea level and high altitude to improve compressor overallperformance was proposed. Flow control methods of swept blade and vaned shroudwere successfully applied to a compressor. Simulation results show parameter’sdifference of new compressors with these two flow control methods decreases obviously.Performance of ompressor with vanned shroud was test. Experimental result shows thatthe compressor composite efficiency of various altitude conditions is improved by1.8%.