Investigation on the unsteadiness of centrifugal compressor exposed to pulsating backpressure

Abstract

Centrifugal compressor is exposed to pulsating backpressure due to the movement of intake valves in internal combustion engine. The performance of compressor deviates from the steady performance map, which affects the matching between turbocharger and engine. The behavior of compressor system at pulsation conditions are investigated via an in-house developed 1D unsteady code validated by experimental results. The influence of pulse frequency, magnitude and compressor characteristic curve on the compressor transient responses, including filling-emptying effect and wave dynamics, are analyzed. Results show that the strength of wave dynamics grows stronger with the increasing of pulse frequency, while the strength of filling-emptying effect increases first then decreases. The rise of pulse magnitude results in an almost linearly increasing of filling-emptying effect, while it can hardly affect the wave dynamics. Furthermore, the influence of pulsation magnitude and frequency represents the influence of local pressure gradient, and a correlation as quadratic curve can be evaluated between the pressure gradient and compressor unsteadiness. On the other hand, the influence of operating point, including the average mass flow rate and the slope of characteristic curve, is confirmed to be evidently smaller, comparing to the influence of pulsation frequency and magnitude. This study is helpful to estimate the behavior of compressor and the discrepancy of performance when operating at unsteady environment or matched with engine.

Influence of pressure pulsation on the performance of compression system and turbocharged engine

“…Recently, with the rapid growth of turbo-charging pressure ratio and the trend of more engine downsizing, the amplitude of this pressure pulsation becomes even more significant, affecting the aerodynamic instability behavior of the rotary compressor and even the engine performance. 4,5 Similar phenomenon of pressure pulsation is also found in long-distance gas transportation. Taking the “West-East Gas Pipeline” project in China as an example, to overcome the pressure loss of the pipeline with a length of 4200 km, multiple compressors in series and parallel are used.…”

“…Pressure pulsations from the upstream reciprocating compressor will therefore influence the working of other connected compressors. 4 These widely existing phenomena of pressure pulsation directly affect the transient performance of the system. Research has been undertaken to investigate the subsequent influences and mechanisms.…”

A numerical study for correlating performance versus number of blades and investigating flow characteristics and loss generation of an automotive radial flow turbine

“…Ketata and Driss 8 studied the admission mode on a double entry turbocharger turbine using a one-dimensional gas dynamics model. Shu et al 9 investigated the effect of the pulse frequency on the unsteady behavior of centrifugal impellers by means of a one-dimensional model. Deng et al 10 presented a dimensionless method for quantifying transient performance of small-scale radial turbines.…”