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).

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.

scholarly journals Performance and Exit Flow Characteristics of Mixed-Flow Turbines

1997 ◽  
Vol 3 (4) ◽  
pp. 277-293 ◽  
Author(s):  
C. Arcoumanis ◽  
R. F. Martinez-Botas ◽  
J. M. Nouri ◽  
C. C. Su
Keyword(s):  
Steady State ◽  
Velocity Ratio ◽  
Tangential Velocity ◽  
Flow Characteristics ◽  
Mixed Flow ◽  
Cross Sectional ◽  
Flow Angle ◽  
Turbine Efficiency ◽  
And Performance ◽  
Inlet Angle

The performance and exit flow characteristics of two mixed-flow turbines have been investigated under steady-state conditions. The two rotors differ mainly in their inlet angle geometry, one has a nominal constant incidence (rotor B) and the other has a constant blade angle (rotor C), but also in the number of blades. The results showed that the overall peak efficiency of rotor C is higher than that of rotor B. Two different volutes were also used for the tests, differing in their cross-sectional area, which confirm that the new larger area volute turbine has a higher efficiency than the old one, particularly at lower speeds, and a fairly uniform variation with velocity ratio.The flow exiting the blades has been quantified by laser Doppler velocimetry. A difference in the exit flow velocity for rotors B and C with the new volute was observed which is expected given their variation in geometry and performance. The tangential velocities near the shroud resemble a forced vortex flow structure, while a uniform tangential velocity component was measured near the hub. The exit flow angles for both rotor cases decreased rapidly from the shroud to a minimum value in the annular core region before increasing gradually towards the hub. In addition, the exit flow angles with both rotors were reduced with increasing rotational speeds. The magnitude of the absolute flow angle was reduced in the case of rotor C, which may explain the improved steady state performance with this rotor. The results also revealed a correlation between the exit flow angle and the performance of the turbines; a reduction in flow angle resulted in an increase in the overall turbine efficiency.

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.

scholarly journals Dynamic Response in Transient Operation of a Variable Geometry Turbine Stage: Influence of the Aerodynamic Performance

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Nicolas Binder ◽  
Jaime Garcia Benitez ◽  
Xavier Carbonneau
Keyword(s):  
Response Time ◽  
Transient Response ◽  
Aerodynamic Performance ◽  
Variable Geometry ◽  
Transient Phase ◽  
Theoretical Expectation ◽  
Turbine Stage ◽  
Experimental Campaign ◽  
Variable Geometry Turbine ◽  
Operating Points

The transient response of a radial turbine stage with a variable geometry system is evaluated. Mainly, the consequences of the variations of the aerodynamic performance of the stage on the response time are checked. A simple quasi-steady model is derived in order to formalize the expected dependences. Then an experimental campaign is conducted: a brutal step in the feeding conditions of the stage is imposed, and the response time in terms of rotational speed is measured. This has been reproduced on different declinations of the same stage, through the variation of the stator geometry, and correlated to the steady-state performance of the initial and final operating points of the transient phase. The matching between theoretical expectation and results is surprisingly good for some configurations, less for others. The most important factor identified is the mass-flow level during the transient phase. It increases the reactivity, even far above the theoretical expectation for some configurations. For those cases, it is demonstrated that the quasi-steady approach may not be sufficient to explain how the transient response is set.

Transient performance of the mixed flow and radial flow variable geometry turbines for an automotive turbocharger

2020 ◽  
Vol 234 (19) ◽  
pp. 3762-3775
Author(s):  
Ramesh Kannan ◽  
BVSSS Prasad ◽  
Sridhara Koppa
Keyword(s):  
Transient Response ◽  
Mass Flow ◽  
Radial Flow ◽  
Flow Variable ◽  
Mixed Flow ◽  
Flow Parameters ◽  
Actuation System ◽  
Turbine Inlet ◽  
Set Up ◽  
Swept Volume

In our previous paper, the steady-state test results of a mixed flow turbine with variable nozzle vanes for a turbocharger are reported. In this paper, the transient response of the same mixed flow turbine along with that of a similarly sized radial flow turbine is presented. The turbine size is suitable for handling the flow capacity of the diesel engines with swept volume up to 1.5 L. The previous experimental test set up is modified by adding a quick-release valve – actuation system before the turbine inlet to obtain a transient response. The radial and mixed flow turbines are tested for different turbine inlet pressures and for various opening positions of the nozzle vanes while matching the turbine mass flow parameters between radial and mixed flow turbines. Typically at nozzle vane openings corresponding to 50% mass flow parameter and 1.5 bar (abs) pressure at the inlet to the turbine, the transient response time for the turbine with mixed flow variable nozzle vanes configuration is about 0.770 s, as compared to 0.858 s for the turbine with radial flow variable nozzle vanes configuration.

scholarly journals Transient response of a large two-stroke marine diesel engine coupled to a selective catalytic reduction exhaust aftertreatment system

2019 ◽  
Author(s):  
Μιχαήλ Φωτεινός
Keyword(s):  
Diesel Engine ◽  
Selective Catalytic Reduction ◽  
Transient Response ◽  
Catalytic Reduction ◽  
Exhaust Aftertreatment ◽  
Marine Diesel Engine ◽  
Variable Geometry ◽  
Aftertreatment System ◽  
Marine Diesel ◽  
Variable Geometry Turbine

Οι μεγάλοι δίχρονοι ναυτικοί κινητήρες diesel χρησιμοποιούνται ως μέσο πρόωσης στην πλειονότητα των ποντοπόρων ναυτικών εφαρμογών. Με στόχο τη μείωση του περιβαλλοντικού αποτυπώματος του θαλάσσιου τομέα, ο Διεθνής Ναυτιλιακός Οργανισμός έχει θεσπίσει κανονισμούς που θέτουν αυστηρά όρια στις εκπεμπόμενες εκπομπές οξειδιών του αζώτου (ΝΟx) από ναυτικούς κινητήρες, γνωστούς και ως κανονισμούς ΙΜΟ Tier III. Η Επιλεκτική Καταλυτική Αναγωγή (Selective Catalytic Reduction, SCR) είναι μια τεχνολογία μετεπεξεργασίας καυσαερίων που επιτρέπει την συμμόρφωση με τα νέα πρότυπα εκπομπών NOx. Λόγω της απαίτησης υψηλών θερμοκρασιών για ομαλή λειτουργία του συστήματος SCR, σε ναυτικές εφαρμογές 2-Χ κινητήρων, το SCR τοποθετείται ανάντη του στροβίλου, δηλαδή μεταξύ του κινητήρα και του υπερπληρωτή (στην πλευρά υψηλής πίεσης του στροβίλου). Αυτό έχει ως αποτέλεσμα την διατάραξη της σύζευξης του κινητήρα και του υπερπληρωτή εισάγοντας προκλήσεις στην μεταβατική λειτουργία του κινητήρα. Λόγω της μεγάλης θερμικής αδράνειας του συστήματος SCR, ο υπερπληρωτής αποκρίνεται σε μία μεταβολή φορτίου του κινητήρα με μία σημαντική χρονική καθυστέρηση, η οποία σε χαμηλό φορτίο του κινητήρα μπορεί να οδηγήσει το σύστημα σε θερμική αστάθεια. Ερευνητές έχουν υπογραμμίσει την ευαισθησία του συστήματος και έχουν προτείνει περίπλοκες και κοστοβόρες λύσεις για να διασφαλίσουν την εύρωστη λειτουργία του, όπως το σύστημα στροβίλου μεταβλητής γεωμετρίας (Variable Geometry Turbine, VTG).Η διατριβή αυτή διερευνά τη μεταβατική απόκριση μεγάλου δίχρονου ναυτικού κινητήρα diesel, χωρίς μεταβλητότητα υπερπληρωτή, συνδεδεμένου με σύστημα απορρύπανσης καυσαερίων SCR. Σκοπός της εργασίας είναι η διερεύνηση της επίδρασης του συστήματος SCR υψηλής πίεσης στην μεταβατική απόκριση του κινητήρα με έμφαση στη λειτουργία σε χαμηλό φορτίο κινητήρα. Λόγω του υψηλού κόστους που εμπεριέχεται στα πειράματα με μεγάλους δίχρονους κινητήρες, η έρευνα διεξήχθη μέσω μοντελοποίησης και προσομοίωσης. Αναπτύχθηκαν μοντέλα μηδενικής διάστασης (zero dimensional models) για την προσομοίωση του κινητήρα πρόωσης και του συστήματος SCR. Το μοντέλο του κινητήρα αναπτύχθηκε χρησιμοποιώντας τον κώδικα προσομοίωσης κινητήρων του Εργαστηρίου Ναυτικής Μηχανολογίας MOTHER και επιβεβαιώθηκε με χρήση διαθέσιμων μετρήσεων από τις δοκιμές αγοράς του κινητήρα (shop trials). Επιπλέον, αναπτύχθηκε ένα μοντέλο για το σύστημα SCR ώστε να ληφθεί υπόψη η θερμοκρασιακή δυναμική του συστήματος. Το μοντέλο SCR επιβεβαιώθηκε μέσω σύγκρισης των αποτελεσμάτων του, με διαθέσιμες μετρήσεις από μία κλίνη δοκιμών ναυτικού κινητήρα με σύστημα SCR. Σε μεταβατικές καταστάσεις φόρτισης, το φορτίο που πρέπει να υπερνικήσει ο κινητήρας, δηλαδή η ροπή της έλικας, δεν είναι γνωστό εκ των προτέρων αλλά είναι προιόν περίπλοκων αλληλεπιδράσεων μεταξύ του κινητήρα, της έλικας και της γάστρας του πλοίου. Προκειμένου να επιτευχθή ακριβής πρόβλεψη του φορτίου του κινητήρα κατά τη διάρκεια των μεταβατικών φαινομένων, μοντέλα για την έλικα και τη γάστρα του πλοίου αναπτύχθηκαν και ενσωματώθηκαν στα μοντέλα γάστρας και έλικας. Το συζευγμένο μοντέλο του συστήματος πρόωσης επικυρώθηκε υπό συνθήκες μεταβατικής φόρτισης χρησιμοποιώντας διαθέσιμα μετρημένα δεδομένα επί πλοίου.Το συνολικό σύστημα προσομοιώθηκε υπό μεταβατική φόρτιση υπό καλές και δυσμενείς καιρικές συνθήκες. Τα αποτελέσματα έδειξαν ότι η μεταβατική απόκριση του κινητήρα επηρεάζεται πράγματι από την παρουσία του συστήματος SCR και το αποτέλεσμα είναι πιο έντονο στην περιοχή χαμηλότερου φορτίου κινητήρα. Ωστόσο, η θερμική αστάθεια του συστήματος μπορεί να αποφευχθεί και το σύστημα είναι σε θέση να λειτουργεί ακόμη και κατά τη λειτουργία σε πολύ χαμηλό φορτίο.

Mild Hybridization via Electrification of the Air System: Electrically Assisted and Variable Geometry Turbocharging Impact on an Off-Road Diesel Engine

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Nicola Terdich ◽  
Ricardo F. Martinez-Botas ◽  
Alessandro Romagnoli ◽  
Apostolos Pesiridis
Keyword(s):  
Energy Efficiency ◽  
Diesel Engine ◽  
Transient Response ◽  
Engine Speed ◽  
Variable Geometry ◽  
Flow Capacity ◽  
Electrically Assisted ◽  
Air System ◽  
Variable Geometry Turbine ◽  
Reduction Of Co2

Electric turbocharger assistance consists in incorporating an electric motor/generator within the turbocharger bearing housing to form a mild hybrid system without altering other mechanical parts of the engine. This makes it an ideal and economical short-to-medium-term solution for the reduction of CO2 emissions. The scope of the paper is to assess the improvements in engine energy efficiency and transient response correlated to the hybridization of the air system. To achieve this, an electrically assisted turbocharger with a variable geometry turbine has been compared to a similar, not hybridized system over step changes of engine load. The variable geometry turbine has been controlled to provide different levels of initial boost, including one optimized for efficiency, and to change its flow capacity during the transient. The engine modeled is a 7-liter, 6-cylinder diesel engine with a power output of over 200 kW and a sub-10-kW turbocharger electric assistance power. To improve the accuracy of the model, the turbocharger turbine has been experimentally characterized by means of a unique testing facility available at Imperial College and the data has been extrapolated by means of a turbine meanline model. Optimization of the engine boost to minimize pumping losses has shown a reduction in brake-specific fuel consumption up to 4.2%. By applying electric turbocharger assistance, it has been possible to recover the loss in engine transient response of the efficiency-optimized system, as it causes a reduction in engine speed drop of 71%–86% and of 79%–94% in engine speed recovery time. When electric assistance is present in the turbocharger, actuating the turbine vanes to assist transient response has not produced the desired result but only a decrement in energy efficiency. If the variable geometry turbine is opened during transients, an improvement in specific energy efficiency with negligible decrement in engine transient performances has been achieved.

Transient EGR in a Long-Route and Short-Route EGR-System

2009 ◽  
Author(s):  
Simon Reifarth ◽  
Hans-Erik A˚ngstro¨m
Keyword(s):  
Steady State ◽  
Heat Release ◽  
Fuel Consumption ◽  
Transient Response ◽  
Short Route ◽  
Driving Cycles ◽  
Combustion Simulation ◽  
Negative Effect ◽  
Variable Geometry Turbine ◽  
Release Data

The use of EGR to lower NOX-emissions from Diesel engines is a well-documented method. Recently, more and more research is done on alternative EGR routing systems such as long-route EGR. To reach future emission legislation goals it is not sufficient to focus on steady-state driving. The emission peaks during the transient parts of driving cycles are gaining importance. It is therefore interesting to analyze the EGR-flow in transients for different configurations of the EGR system. In this work, a 1-D simulation is performed in GT-Power for a Euro 4 passenger car diesel engine equipped with cooled short-route EGR and a variable geometry turbine. For calibration of the simulation, load transients were measured including the measurement of transient EGR-rates using a fast CO2-analyzer and cylinder pressure to obtain heat-release data. While the transient heat-release rates are used as an input for the combustion-simulation, the EGR response measurements are used as a reference for calibration of the EGR-system and its components. A long route EGR system and a short-route EGR system are then simulated and compared, focusing on transient response, availability of EGR during the transient and the fuel consumption in steady state. It is shown that the long-route system has advantages in both steady-state and transient driving conditions. In steady state it can decrease fuel consumption, in transient it can provide EGR without negative effect on the transient response.

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