# Effect on Vehicle Turbocharger Exhaust Gas Energy Utilization for the Performance of Centrifugal Compressors under Plateau Conditions

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Compressor Performance Analysis

_{P}in the physical properties is 0.2%, the change rate of the K value is 0.07%, the change rate of P

_{r}is about 1%, and change rate of the three is very small. If we neglect the influence of the physical properties at the impeller inlet, Equation (1) can be expressed as:

_{2}is the impeller outlet diameter.

## 3. Numerical Calculation Method

## 4. Calculation Results Analysis

#### 4.1. Compressor Performance Comparison

#### 4.2. Internal Flow Analysis in the Compressor

#### 4.3. Exergy Destruction and Flow Loss Analysis in the Impeller

#### 4.4. Loss Analysis of Impeller Downstream

## 5. Conclusions

- (1)
- The high altitude work environment has remarkable effects on exhaust gas energy utilization for a vehicle turbocharger. The compressor inlet conditions change with altitude, which influences turbocharger compressor pressure ratio and efficiency features. The results show that with the increase of altitude from 0 m to 4500 m, the peak efficiency of the compressor is reduced by 2.4%, while the peak pressure ratio is increased by 7%. With the increase of altitude, the Reynolds number decreases and air viscous force increases significantly, which causes the efficiency of the compressor to drop obviously.
- (2)
- From the detailed internal flow analysis in compressor, the main reasons for the low efficiency under the condition of the plateau environment include: the shock loss is increasing at the leading edge and the leakage flow loss is more intense at the downstream. The main blade load is more sensitive to the altitude, and it has obvious change at the downstream of the pressure side and upstream of the suction side.
- (3)
- The results show that, on the one hand, as the altitude increases, the compressor impeller static pressure gradient increases, the pressure contour lines will become dense, which can lead to higher pressure ratio at the impeller outlet, while on the other hand, blade loads all increase from 80% position of the main blade and 40% position of the splitter blade, which can contribute to the pressure ratio increment.
- (4)
- The exergy destruction analysis shows that, with the increasing altitude, the leading edge of the impeller has the biggest exergy destruction difference, and the downstream of the compressor impeller passage has the second biggest exergy destruction difference, and more attention needs to be paid to these positions during compressor design.
- (5)
- In the downstream of the impeller, due to the decrease of Reynolds number, the boundary layer is thickened, and the flow loss in the diffuser and volute is intensified, especially the position near the volute tongue. The region where the entropy is over 150 J/(kg·K) expands significantly near the volute tongue. These positions need a detailed optimization design to decrease flow losses and to satisfy the plateau condition requirements.

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## Nomenclatures

Symbols | |

π_{c} | Compressor pressure ratio |

η_{c} | Adiabatic efficiency |

${M}_{c}^{\ast}$ | Corrected mass flow rate |

${n}_{c}^{\ast}$ | Corrected rotational speed |

C_{p} | Specific heat at constant pressure |

K | Specific heat ratio |

P_{r} | Prandtl number |

Re | Reynolds number |

M_{c} | Mass flow rate |

n_{c} | Actual speed of the compressor |

T_{0} | Inlet Total temperature |

P_{0} | Inlet Total pressure |

P_{1} | Outlet Total pressure |

μ | Dynamic viscosity coefficient |

u_{2} | Peripheral speed |

b_{2} | Impeller blade outlet width |

ρ_{0} | Air density at the impeller inlet |

R | Gas constant of air |

W_{T} | Output power of the turbine |

m_{e} | Mass flow rate of gas |

AFR | Air/Fuel Ratio |

T_{03} | Turbine inlet temperature |

T_{04} | Turbine outlet temperature |

η_{T} | Efficiency of the turbine |

η_{TC} | Efficiency of turbocharger |

π_{T} | Expansion ratio of the turbine |

C_{pe} | Gas specific heat at constant pressure |

$\dot{S}$ | Entropy of the airflow |

p | Static pressure |

$\Delta {\dot{S}}_{0}$ | Entropy increases of the environment |

$\dot{I}$ | Exergy destruction |

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**Figure 4.**Change of compressor performances: (

**a**) Efficiency characteristics; (

**b**) Pressure ratio characteristics.

**Figure 5.**Characteristics of compressor volume flow rate, pressure ratio and efficiency: (

**a**) Efficiency characteristics; (

**b**) Pressure ratio characteristics.

**Figure 6.**Relative Mach number distribution at the meridional averaged surface ((

**left**) plain, (

**right**) plateau).

**Figure 7.**Relative Mach number distribution at the inlet of the impeller ((

**left**) 0 m, (

**right**) 4500 m).

**Figure 8.**Static pressure ratio distribution on the meridional averaged surface: (

**a**) (

**left**) plain, (

**right**) plateau; (

**b**) contour lines superposition graph.

**Figure 10.**Distribution of relative Mach number and static pressure ratio along meridian direction: (

**a**) Relative Mach number; (

**b**) Static pressure ratio.

**Figure 11.**Load distribution of blade surface at 10% blade span: (

**a**) main blade; (

**b**) splitter blade.

**Figure 12.**Load distribution of blade surface at 50% blade span: (

**a**) main blade; (

**b**) splitter blade.

**Figure 13.**Load distribution of blade surface at 90% blade span: (

**a**) main blade; (

**b**) splitter blade.

**Figure 14.**Distribution of the relative Mach number and its gradient at 90% blade span: (

**a**) Relative Mach number ((

**left**) plain; (

**right**) plateau); (

**b**) Distribution of the gradient of the relative Mach number ((

**left**) plain; (

**right**) plateau).

**Figure 15.**Exergy destruction comparison analysis: (

**a**) Sections of the compressor passage; (

**b**) Exergy destruction in the compressor.

**Figure 17.**Entropy distribution of the impeller tail: (

**a**) 90% blade span; (

**b**) 50% blade span; (

**c**) 10% blade span.

**Figure 18.**Relative meridional velocity and streamline distribution at channel section of the impeller trailing edge.

**Figure 21.**Distribution of static pressure ratio of 0-0 section of the volute ((

**left**) plain, (

**right**) plateau).

**Figure 22.**Distribution of relative Maher number of 0-0 section of the volute ((

**left**) plain, (

**right**) plateau).

**Figure 23.**Entropy distribution on the section of diffuser and volute ((

**left**) plain, (

**right**) plateau).

Altitude/m | Inlet Total Temperature/K | Inlet Total Pressure/kPa | Rotational Speed/rpm | Solid Wall |
---|---|---|---|---|

0 | 298 | 100 | 90,000 | Adiabatic, no slip |

4500 | 269 | 56 | 90,000 | Adiabatic, no slip |

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**MDPI and ACS Style**

Zhang, H.; Zhang, H.; Wang, Z.
Effect on Vehicle Turbocharger Exhaust Gas Energy Utilization for the Performance of Centrifugal Compressors under Plateau Conditions. *Energies* **2017**, *10*, 2121.
https://doi.org/10.3390/en10122121

**AMA Style**

Zhang H, Zhang H, Wang Z.
Effect on Vehicle Turbocharger Exhaust Gas Energy Utilization for the Performance of Centrifugal Compressors under Plateau Conditions. *Energies*. 2017; 10(12):2121.
https://doi.org/10.3390/en10122121

**Chicago/Turabian Style**

Zhang, Hong, Hang Zhang, and Zhuo Wang.
2017. "Effect on Vehicle Turbocharger Exhaust Gas Energy Utilization for the Performance of Centrifugal Compressors under Plateau Conditions" *Energies* 10, no. 12: 2121.
https://doi.org/10.3390/en10122121