Research On Performance And Power Recovery Of Diesel Engine At Different Altitudes

Since the single-stage turbocharging system can hardly meet the demand for boost pressure ratio and reduced flow at different altitudes,the power,fuel economy and exhaust temperature of the diesel engine shall be influenced by variable altitude conditions.In this paper,the performance test of SC7 H diesel engine at different altitudes is carried out to analyze the influence of altitude change on the performance of the original engine.Then the matching calculation of the regulated two-stage supercharging(R2S)system is accomplished.Finally,the adaptability of the engine to variable altitude is improved.Through theoretical analysis,it is found that air intake flow can not be completely recovered by the original single-stage supercharging system when the altitude reaches 3000 m.The matching calculation of the R2 S system is carried out with the objective that the external characteristic power and air intake flow of 1400-2300r/min do not decrease within 4500 m altitude.The GT-POWER simulation model is built and the feasibility analysis of the matching scheme is conducted by simulation calculation.Based on the test bench of original SC7 H diesel engine,the experimental study is carried out under all working conditions at different altitudes,and the effects of altitude on single-stage turbocharging system,combustion characteristics and performance of the engine are obtained.When the altitude rises from the plain to 4500 m,the external characteristic power and air intake flow of diesel engine in the range of 1000-2300r/min,decrease by 25.9% and 34.7%.BSFC increases by 13.7%.Tests of SC7 H diesel with R2 S system at different altitudes are carried out.The matching scheme is verified and evaluated by analyzing the influence of altitude change on the performance of R2 S system and engine.The experimental results show that compared with the single-stage turbocharging system at an altitude of 4500 m,the external characteristic power and air intake flow increase by 19.9% and 38.4% in the range of 1400-2300r/min,respectively.The external characteristic power and air intake flow are completely recovered within 4500 m altitude,and all the indexes are within the limits.At the same time,the BSFC is less than 0.36% higher than that of the original diesel in plain,which shows that the matching scheme can meet the matching target well.