Lean and Straight Nozzle Vanes in a Variable Geometry Turbine: A Steady and Pulsating Flow Investigation

2008 ◽  
Author(s):  
Srithar Rajoo ◽  
R. F. Martinez-Botas
Keyword(s):  
Pressure Ratio ◽  
Velocity Ratio ◽  
Pulsating Flow ◽  
Maximum Pressure ◽  
Variable Geometry ◽  
Flow Investigation ◽  
Variable Geometry Turbine ◽  
The Difference ◽  
Vane Angle ◽  
Ratio Range

Variable Geometry Turbines (VGT) are widely used to improve engine-turbocharger matching and currently common in diesel engines. VGT has proven to provide air boost for wide engine speed range as well as reduce turbo-lag. This paper presents the design and experimental evaluation of a variable geometry mixed flow turbocharger turbine. The tests have been carried out with a permanent magnet eddy current dynamometer within a velocity ratio range of 0.47 to 1.09. The peak efficiency of the variable geometry turbine corresponds to vane angle settings between 60° and 65°, for both the lean and straight vanes in the region of 80%. The variable geometry turbine was tested under pulsating flow with straight and lean nozzle vanes for different vane angle settings, 40Hz and 60Hz flow. In general, the range of mass flow parameter is higher in the straight nozzle vanes with an average of 66.4% and 69.7% for 40Hz and 60Hz flow respectively. The straight nozzle vanes also shows increasing pressure ratio range compared to the lean nozzle vanes, which is more apparent in the maximum pressure ratio experienced by the turbine in an unsteady cycle. In overall, the cycle averaged efficiency in the straight vane configuration is marginally higher than the lean vane. Furthermore, the difference to the equivalent quasi-steady is better in the straight vane configuration compared to the lean vane.

A comparative study of the performance of the mixed flow and radial flow variable geometry turbines for an automotive turbocharger

2018 ◽  
Vol 233 (8) ◽  
pp. 2696-2712 ◽  
Author(s):  
K Ramesh ◽  
BVSSS Prasad ◽  
K Sridhara
Keyword(s):  
Mass Flow ◽  
Flow Parameter ◽  
Radial Flow ◽  
Velocity Ratio ◽  
Variable Geometry ◽  
Flow Variable ◽  
Mixed Flow ◽  
Turbine Efficiency ◽  
Variable Geometry Turbine ◽  
Specific Speed

A new design of a mixed flow variable geometry turbine is developed for the turbocharger used in diesel engines having the cylinder capacity from 1.0 to 1.5 L. An equivalent size radial flow variable geometry turbine is considered as the reference for the purpose of bench-marking. For both the radial and mixed flow turbines, turbocharger components are manufactured and a test rig is developed with them to carry out performance analysis. Steady-state turbine experiments are conducted with various openings of the nozzle vanes, turbine speeds, and expansion ratios. Typical performance parameters like turbine mass flow parameter, combined turbine efficiency, velocity ratio, and specific speed are compared for both mixed flow variable geometry turbine and radial flow variable geometry turbine. The typical value of combined turbine efficiency (defined as the product of isentropic efficiency and the mechanical efficiency) of the mixed flow variable geometry turbine is found to be about 25% higher than the radial flow variable geometry turbine at the same mass flow parameter of 1425 kg/s √K/bar m2 at an expansion ratio of 1.5. The velocity ratios at which the maximum combined turbine efficiency occurs are 0.78 and 0.825 for the mixed flow variable geometry turbine and radial flow variable geometry turbine, respectively. The values of turbine specific speed for the mixed flow variable geometry turbine and radial flow variable geometry turbine respectively are 0.88 and 0.73.

Mean-Line Modelling of a Variable Geometry Turbocharger (VGT) and Prediction of the Engine-Turbocharger Coupled Performance

2017 ◽  
Author(s):  
Anand Mammen Thomas ◽  
Jensen Samuel ◽  
A. Ramesh
Keyword(s):  
Pressure Ratio ◽  
Operating Conditions ◽  
Relaxation Techniques ◽  
Variable Geometry ◽  
Test Bed ◽  
Variable Geometry Turbocharger ◽  
Initial Assumption ◽  
Blockage Factor ◽  
Pressure Boundary Condition ◽  
Variable Geometry Turbine

Mean-line modelling approach which has generally been applied to fixed geometry turbocharger turbines has been extended to predict the performance of the variable geometry turbine for different inlet blade angles. The model uses an initial assumption of turbine inlet pressure which was iteratively corrected based on outlet pressure boundary condition. The model was implemented in MATLAB and stable and convergent solutions were obtained using relaxation techniques for different operating conditions. Experiments were done on a state of the art transient diesel engine test bed using the same VGT turbine in the turbocharger at different engine torques and speeds. Using experimental data the model was calibrated for the aerodynamic blockage in the fixed nozzle and rotor blade passages. Results revealed that turbine overall pressure ratio can be predicted accurately if a blockage factor varying with nozzle blade orientation is used in the model.

Investigation of a Variable Geometry Turbine Nozzle for Diesel Engine Turbochargers

2019 ◽  
Author(s):  
Anuj Srivastava ◽  
Kuldeep Kumar ◽  
Ganesh Banda
Keyword(s):  
Pressure Ratio ◽  
Boost Pressure ◽  
Variable Geometry ◽  
Efficient Design ◽  
Performance Variation ◽  
High Efficient ◽  
Emission Regulations ◽  
Variable Geometry Turbine ◽  
Potential Benefits ◽  
Wide Operating

Abstract High power demand, emission regulations, high efficient design are the prime requirement for the design of turbochargers. VGT (variable geometry turbocharging) is most widely used and explored compared to other available options to deal with today’s market. VGT turbochargers offers several potential benefits when compared to fixed geometry turbochargers, like increased transient response, wide operating range, improved torque characteristics, boost pressure recovery and better fuel economy. In this paper performance variation of compressor and turbine viz, — Pressure ratio, mass flow, and efficiency, and throat area are optimized to reach to the operating point of the engine. Different vane angles (0, +4°, +7°, +10° & +15°) are studied to understand the variation of transient turbine response. Authors also discussed the mechanical conceptualization of the VANT (Variable area nozzle) in thought of having great impact on the performance.

Investigations Into the Performance of a Turbogenerated Biogas Engine During Speed Transients

2011 ◽  
Author(s):  
Ian Thompson ◽  
Stephen Spence ◽  
Charles McCartan ◽  
David Thornhill ◽  
Jonathan Talbot-Weiss
Keyword(s):  
Engine Speed ◽  
Combustion Engine ◽  
Pressure Ratio ◽  
Exhaust Gas ◽  
Variable Geometry ◽  
System Efficiency ◽  
Variable Geometry Turbine ◽  
Exhaust Stream ◽  
Full Power ◽  
System Operating

Turbogenerating is a form of turbocompounding whereby a Turbogenerator is placed in the exhaust stream of an internal combustion engine. The Turbogenerator converts a portion of the expelled energy in the exhaust gas into electricity which can then be used to supplement the crankshaft power. Previous investigations have shown how the addition of a Turbogenerator can increase the system efficiency by up to 9%. However, these investigations pertain to the engine system operating at one fixed engine speed. The purpose of this paper is to investigate how the system and in particular the Turbogenerator operate during engine speed transients. On turbocharged engines, turbocharger lag is an issue. With the addition of a Turbogenerator, these issues can be somewhat alleviated. This is done by altering the speed at which the Turbogenerator operates during the engine’s speed transient. During the transients, the Turbogenerator can be thought to act in a similar manner to a variable geometry turbine where its speed can cause a change in the turbocharger turbine’s pressure ratio. This paper shows that by adding a Turbogenerator to a turbocharged engine the transient performance can be enhanced. This enhancement is shown by comparing the turbogenerated engine to a similar turbocharged engine. When comparing the two engines, it can be seen that the addition of a Turbogenerator can reduce the time taken to reach full power by up to 7% whilst at the same time, improve overall efficiency by 7.1% during the engine speed transient.

Performance of a Mixed Flow Turbocharger Turbine Under Pulsating Flow Conditions

1995 ◽  
Author(s):  
C. Arcoumanis ◽  
I. Hakeem ◽  
L. Khezzar ◽  
R. F. Martinez-Botas ◽  
N. C. Baines
Keyword(s):  
High Efficiency ◽  
Pressure Ratio ◽  
Velocity Ratio ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Engine Exhaust ◽  
High Pressure Ratio ◽  
Design Speed ◽  
Swallowing Capacity

The performance of a high pressure ratio (P.R.=2.9) mixed flow turbine for an automotive turbocharger has been investigated and the results revealed its better performance relative to a radial-inflow geometry under both steady and pulsating flow conditions. The advantages offered by the constant blade angle rotor allow better turbocharger-engine matching and maximization of the energy extracted from the pulsating engine exhaust gases. In particular, the mixed inlet blade geometry resulted in high efficiency at high expansion ratios where the engine-exhaust pulse energy is maximum. The efficiency characteristics of the mixed flow turbine under steady conditions were found to be fairly uniform when plotted against the velocity ratio, with a peak efficiency at the design speed of 0.75. The unsteady performance as indicated by the mass-averaged total-to-static efficiency and the swallowing capacity exhibited a departure from the quasi-steady assumption which is analysed and discussed.

scholarly journals Formation of Static Characteristics of a Diesel Engine

2020 ◽  
pp. 43-50
Author(s):  
A.G. Kuznetsov ◽  
S.V. Kharitonov
Keyword(s):  
Diesel Engine ◽  
Power Plants ◽  
Guide Vane ◽  
Fuel Efficiency ◽  
Maximum Pressure ◽  
Variable Geometry ◽  
Static Characteristics ◽  
Fuel Supply ◽  
Air Supply ◽  
Variable Geometry Turbine

The introduction of modern diesel fuel supply systems and the use of electronic components in control systems provide new possibilities for shaping engine characteristics targeted at specific energy consumers. Under these conditions, the type of engine characteristics is determined by the operation of the air supply system. This work examines the formation of static characteristics for a promising D500 diesel engine for train and ship power plants. Modeling of the diesel operation modes is carried out on computer models in the MATLAB/Simulink and Diesel-RK software packages. Variants of the full-load curves of the diesel engine are presented for different ways of turbocharger control: using a turbine of variable geometry and with sequential turbocharging. The fuel supply is limited according to the air-fuel ratio and the maximum pressure in the engine cylinders. For a variable geometry turbine, a matrix of the positions of the guide vane blades is obtained from the condition of optimizing diesel modes for fuel efficiency. Possibilities to obtain the efficiency characteristic that would provide the minimal fuel consumption for train and ship power plants are shown.

Investigation of Vaned Diffusers as a Variable Geometry Device for Application to Turbocharger Compressors

1992 ◽  
Vol 206 (3) ◽  
pp. 209-220 ◽  
Author(s):  
P M Jiang ◽  
A Whitfield
Keyword(s):  
Pressure Ratio ◽  
Leading Edge ◽  
Variable Geometry ◽  
Vaneless Diffuser ◽  
Double Row ◽  
Guide Vanes ◽  
Operating Range ◽  
Consequent Reduction ◽  
Inlet Angle ◽  
Vane Angle

The potential of guide vanes as a variable geometry device, placed in the conventional vaneless diffuser, to extend the operating range of a turbocharger compressor is investigated. Vaned diffusers are not normally employed in turbocharger applications as the consequent reduction in operating range is more damaging than the beneficial improvement in peak efficiency and pressure ratio. The variable geometry concept considered here is primarily one in which the guide vanes are introduced at the near surge flow conditions. The leading edge vane angle is set to accept the highly tangential flow at the near surge conditions, and the vane is then used to guide the fluid towards the radial direction in order to reduce the long flow path through the diffuser. Four types of vane arrangements are considered: (a) 12 and 6 full length vanes, with inlet vane angles of 75° and 80°; (b) 6 short inlet vanes to give a high aspect ratio; (c) 12 and 6 short vanes located in the outer half of the vaneless diffuser passage; and (d) double-row vane rings. It is shown that short vanes deployed at the diffuser outlet not only improve the efficiency and pressure ratio but also extend the high flow operating range. Further, the introduction of short inlet vanes with an inlet angle of 80° improves the peak pressure ratio and efficiency, and extends the near surge operating range.

Transient Response of Mixed Flow Variable Geometry Turbine for a Turbocharger

2015 ◽  
Author(s):  
Ramesh Kannan ◽  
Bhamidi Prasad ◽  
Sridhara Koppa
Keyword(s):  
Steady State ◽  
Transient Response ◽  
Velocity Ratio ◽  
Typical Result ◽  
Variable Geometry ◽  
Flow Variable ◽  
Data Logging ◽  
Mixed Flow ◽  
Response Behaviour ◽  
Variable Geometry Turbine

A specific design of mixed flow variable geometry turbine for an automotive sub 1.5 litre diesel engine turbocharger is proposed in this paper. An experimental set up is developed for measuring the steady state and transient response behaviour of the turbine at different nozzle vane opening positions. The rotor speed, pressure and temperature before and after the turbine are measured and recorded using high frequency data logging system. The steady state performance for mass flow, efficiency, velocity ratio, specific speed and the transient response behaviour of the mixed flow variable geometry turbine (MFVGT) are compared against the same parameters of a radial flow variable geometry turbine (RFVGT) of similar dimensions. Typical result indicates that the transient response of the MFVGT is faster by about 350 milliseconds than the radial at turbine inlet pressure of 0.2 bar (g).

Aerodynamic Design of Fixed and Variable Geometry Nozzleless Turbine Casings

1980 ◽  
Vol 102 (1) ◽  
pp. 141-147 ◽  
Author(s):  
P. M. Chappie ◽  
P. F. Flynn ◽  
J. M. Mulloy
Keyword(s):  
Design Method ◽  
Pressure Ratio ◽  
Wall Friction ◽  
Variable Geometry ◽  
Aerodynamic Design ◽  
Blade Vibration ◽  
Turbine Wheel ◽  
Design Constraints ◽  
Variable Geometry Turbine ◽  
Turbine Casing

A design method has been developed to produce nozzleless turbine casings which provide a centrifugal turbine wheel with a uniform inlet state. The analysis includes the effect of wall friction and has been found to accurately predict the mass flow versus pressure ratio characteristics of nozzleless casings. The uniform inlet state provided by this design approach provides turbine wheel/casing configurations with near optimum efficiency and a very low aerodynamic blade vibration excitation level. The model has been extended to produce variable area casings to simulate a simplified variable casing geometry. Testing has verified the accuracy of the approach both in the design point and variable geometry cases. Also depicted are new insights into turbine wheel design constraints discovered when using a variable geometry turbine casing.

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