Three-Dimensional Computational Loss Analysis of a Compressor for Heavy Duty Truck Engine Turbochargers

Abstract

This paper presents a detailed loss analysis of a centrifugal compressor stage with a vaned diffuser for application in a heavy-duty engine turbocharger. The analysis is carried out in order to investigate the loss distribution in the stage. To quantify the impact of different loss types and locations, a detailed validated steady-state three-dimensional (3D) computational fluid dynamics (CFD) solution is employed. The local entropy production rate is calculated for two operating points (full load and part load), which are most relevant to the real-world operation of the compressor in a truck application. Two methods are suggested as the procedure for the division of the whole fluid volume into subvolumes because this is key for the resulting loss distribution. The primary loss-generating mechanisms are shown at main operating conditions to reveal the regions of improvement. A detailed grid study was conducted to enable the calculation of the entropy ratio. It was possible to capture around 78% (partial load) and 70% (full load) of the entropy production with a mesh with circa 100 × 106 elements. Around half of the losses were due to the boundary layer friction, followed by losses associated with a boundary layer separation resulting from the back-flow at the shroud contour close to the impeller exit and back disk friction accounted for with 6–7% of the stage's losses.

Effect of housing surface roughness on the performance of a centrifugal compressor for turbocharger: Experimental and numerical study

“…In their CFD study, Sun et al 48 also found higher compressor efficiency, when the wheel backside cavity was neglected. Further, the 3D computational loss analysis by Abel et al 5 reported that the wheel backside cavity losses raised with increase in mass flow rate and contributed to about 6%–7% on the total pressure losses. However, the main focus of the present study is to evaluate the effect of roughness level of the housing on the compressor performance.…”

“…The CFD predictions of Javed and Kamphues 25 reported a reduced performance with volute surface roughness because of additional flow blockage and increased meridional velocity. Also, the loss analysis by Abel et al 5 described that circa half of the volute losses were because of friction in the housing surfaces.…”

“…The increase in the losses with roughness can be attributed to higher entropy production because of increased turbulent kinetic energy and viscous shear at the volute surface. 5 Also, more reduction in compressor efficiency occurs with higher volute roughness levels at higher mass flow rates. Again, this is similar to the findings of Javed and Kamphues, 25 in which compressor efficiency reduction for volute roughness level of 3.3 BR at peak efficiency point with design speed was about 0.6% and 1% by predictions and experiments, respectively.…”

“…3 The accumulation of particle deposits in the housing affects the compressor performance during operation and significantly degrade the engine power output. 4 Moreover, according to Abel et al, 5 about half of the losses in the compressor were because of boundary layer friction and they emphasise a need for evaluation of effect of volute surface roughness on the compressor performance.…”