Writing
SDSU Hydraulic Engineering Flow Control Measurement Powerpoint Presentation

San Diego State University

Question Description

Need help with my Engineering question - I’m studying for my class.

This is hydraulic engineering class

You need to submit your projects in power-point format and the project could be based on the topic "Flow Control Measurement"

Your project should include an introduction, literature review, Methodology, Results and Discussion.

I recommend you to find a research paper and summarize it.

Prepare your slides based on maximum 15 minutes presentation

Student has agreed that all tutoring, explanations, and answers provided by the tutor will be used to help in the learning process and in accordance with Studypool's honor code & terms of service.

Final Answer

Attached.

Turbocharger and Turbocharging Special Issue

Bidirectional flow measurement based on
the differential pressure method for surge
analysis on a small centrifugal compressor

Proc IMechE Part C:
J Mechanical Engineering Science
0(0) 1–11
! IMechE 2016
Reprints and permissions:
sagepub.co.uk/journalsPermissions.nav
DOI: 10.1177/0954406216667406
pic.sagepub.com

Moritz Werner1, Roland Baar1, Peter Haluska2 and Ivo Sandor2

Abstract
To obtain a high temporal resolution of mass flow data, a flowmeter based on the differential pressure method has been
developed. It is capable of detecting negative flow for investigations of dynamic effects in small centrifugal compressors
used for turbocharging automotive internal combustion engines. Experiments were performed at a hot gas test bench
focusing on the surge characteristics at different turbocharger speeds and the influence of volume modifications downstream of the compressor. Instantaneous operating points could be traced in the compressor map including the typical
orbits at deep surge resulting from the cyclic character of the phenomenon.
Keywords
Centrifugal compressor, flow measurement, flowmeter, Venturi effect, surge
Date received: 6 April 2016; accepted: 28 July 2016

Introduction
Surge is an unstable turbocharger compressor performance occurring at low flow rates and high pressure ratios. If the pressure gradient in the compressor
is too high, flow separation and stalling of fluid within
the impeller or diffusor can result in temporarily
reversed flow. This causes a cyclic discharging and
charging of the compressor outlet volume and leads
to large oscillations in pressure and mass flow. Such
an unstable operating mode must be avoided since it
can severely damage the turbocharger and limit the
functionality of the combustion engine attached to the
compression system.
For an investigation of the cyclic phenomenon, the
instantaneous operating points of the compressor
during surge shall be traced. The surge phenomenon
with respect to the geometry of the ducting system
downstream of the compressor has first been analyzed
and modeled by Greitzer,1 followed by numerous
researches e.g. Galindo et al.2 and Kabalyk et al.3
Testing facilities for turbochargers of automotive
engines are commonly designed to record steady-state
performance maps. At these operating points, typically only one-directional, stable flow occurs. Hence,
the common data acquisition rates of turbocharger
test benches are in the range of 10–100 Hz.4 The oscillations during surge are of frequencies between 5 and
30 Hz.5 An analysis of this phenomenon therefore
demands higher time resolution of the data at

rates 51 kHz. In order to achieve this, the sampling
rate of the data acquisition hardware has to be
increased and sensors have to be used with a suitable
short latency and settling time.
Operating points of compressors are typically characterized by compressor speed, pressure ratio and
flow rate. Since the speed measurement is generally
based on counting the blades of the compressor
wheel passing the sensor position, it can be easily
adapted. The pressure can also be measured at suitable rates with well-proven techniques such as
piezoresistive or piezoelectric sensors. However, the
measurement of flow rate in this setting presents several challenges for commercially available solutions.
For the analysis of transient effects, it is necessary
to minimize damping effects caused by volumes and
piping. A sensor location very close to the inlet or
outlet of the compressor is mandatory with only a
small flow-calming section for the sensor itself.
However, this sensor position calls for a measuring
1
Institut für Land- und Seeverkehr, Fachgebiet
Verbrennungskraftmaschinen, Technische Universität Berlin, Berlin,
Germany
2
Continental Automotive GmbH, Regensburg, Germany

Corresponding author:
Moritz Werner, Technische Universität Berlin, Institut für Land- und
Seeverkehr, Fachgebiet Verbrennungskraftmaschinen, Carnotstraße 1 A,
Berlin 10587, Germany.
Email: moritz.werner@tu-berlin.de

2
system with a low impact of swirls or unbalanced flow
profiles. Flow straighteners would also add to the
damping volumes or their geometry might reduce
the effect to be examined.
One of the fundamental requirements for a precise
surge analysis is the reliable detection and measurement of negative flow. Systems that offer this feature,
such as ultrasonic sensors or particle image velocimetry, require considerable investments. Hotwire
probes are commonly used for this measuring task,
e.g. by Grigoriadis.4 However, they do not contain a
determination of the flow direction and are easily
affected by asymmetric flow profiles. In addition they
are rather fragile. Possible occurrence of oil droplets or
dust particles should be considered though which must
not impair the results or even damage the sensor.
To meet these objectives, a differential pressure
flowmeter was designed to be installed directly at
the compressor outlet, as shown in Figure 1. This
position allows the indication of flow direction with
a method based on pressure trends, which is explained
further below in the text. Measurement techniques for
pulsating flow with the differential pressure principle
are proposed by Gajan et al.6 and Dobelhoff-Dier
et al.7 using orifice plates as well as by Beaulieu8
using a Venturi tube for a liquid flow application.
Venturi tube measurements of pulsating, unidirectional gas flow are described by Laurantzon9 and
Reuter.10 In addition to the industry standards11,12
for the design and installation of such an instrument,
Mottram’s13 and Reader-Harris’14 work were used as
the basis for the development.

Flowmeter design
The flowmeter presented here uses the Venturi effect
at a defined constriction inside the measuring device,
which is built into a fluid leading conduit. Due to the
reduction of cross section, the flow is accelerated at

Proc IMechE Part C: J Mechanical Engineering Science 0(0)
this throat and a static pressure drop from the duct of
original flow area can be determined. This pressure
difference characterizes the flow velocity and therefore
the mass flow.
The flowmeter presented here has a symmetrical
geometry with cylindrical sections at the inlet, throat
and outlet with conical sections in between (Figure 2).
It differs from typical Venturi tubes defined by the
industry standard.12 One parameter in accordance
with the norm and inside the proposed range is the
diameter ratio of  ¼ D2/D1 ¼ 0.74, which results in a
significant rise of velocity in the center part. This leads
to high differential pressures that are easier to detect,
especially if the flow is subject to pressure fluctuations. However, the geometry was designed so that
Mach numbers in the throat do not exceed 0.3 at
steady-state operating points. In addition, rather
high b-values minimize the influence of the flowmeter
on the flow and the phenomenon to be examined.
Since the flowmeter itself holds a certain volume of
fluid, draining effects occurring during the change
of flow direction have to be minimized. During the
designing process, different length/diameter ratios
L/D1 for the flowmeter have been tested at the test
bench. The evaluation resulted in a minimized short
length/diameter ratio of L/D1 ¼ 1.79 with a high
opening angle of d ¼ 30 on both sides.
The symmetrical design is the basis for the analysis
of reverse flow. Therefore, the flowmeter is equipped
with a sensor set at the main flow inlet (A) and at
outlet (B). The measurement planes are located halfway along each of the cylindrical sections. Prior to the
measurements, computational fluid dynamics analysis
was used to investigate the locations. For the simulation, the flowmeter was connected to a fully modeled
compressor side of the turbocharger. Further information on the compressor simulation are described
by Schäfer.15 The results calculated for one line of
constant compressor speed showed consistent values

L

δ

D1

D 3 =D 1

D2

Main flow direction

TA
Sensors:

Figure 1. Differential pressure flowmeter.

pA
set A

Δp A

Δp B

pB
set B

Figure 2. Schematic representation of the flowmeter.

TB

3

of the flow rate coefficient cD of the flowmeter,
although swirl effects increase with higher mass
flows and are dominant at compressor operating
points close to choke. Swirl flow should therefore
only have a negligible influence on the measurement
results.
Differential pressure sensors are installed between
the large and the narrowed flow section, pA and
pB. For the large cross-sectional areas, pressure
and temperature are also measured to determine the
fluid density. For a temporal resolution of 1 kHz,
pressure sensors with a response time of 0.5 ms and
limited internal volume are installed. They are connected with the flow through small bore holes in the
wall of the flowmeter. The temperature is measured by
open th...

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Carnegie Mellon University

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