Operating process of oil-free scroll vacuum pump

The Ministry of Science and Higher Education of the Russian Federation 
Kazan National Research Technological University 
OPERATING PROCESS OF OIL -FREE
SCROLL VACUUM PUMP 
Monograph 
Kazan 
KNRTU Press 
2023 

UDC 621.52 
Published by the decision of the Editorial Review Board  
of the Kazan National Research Technological University 
Reviewers: 
PhD in Technical Science E. Kapustin 
Doctor in Physisc and Mathematics P. Osipov 
Authors: A. Tyurin, A. Raykov, S. Salikeev, A. Burmistrov 
Operating process of oil-free scroll vacuum pump : Monograph / I. Tyurin, 
A. Raykov, S. Salikeev, A. Burmistrov; The Ministry of Education and Science of the Russian Federation, Kazan National Research Technological University. – Kazan : KNRTU Press, 2023. – 112 p.
ISBN 978-5-7882-3446-5 
The monograph highlights the operating principle, structural modifications and 
classifications of oil-free scroll vacuum pumps. Engineering solutions applied for SVP 
are analysed specifying their advantages and disadvantages. Experimental study procedure is described, and research findings are presented. 
The book is intended for use by technicians in vacuum and compressor engineering. 
It will be useful for professors, Ph.D. fellows and students engaged in the training programs 15.03.02 “Technological machines and equipment”, 16.03.01 “Applied physics”, 
14.03.01 “Nuclear engineering and thermal physics”, 28.03.02 “Nanoengineering”. 
The monograph is prepared at the Department of Vacuum and compressor equipment of physical machines. 
UDC 621.52 
ISBN 978-5-7882-3446-5 
© A. Tyurin, A. Raykov, S. Salikeev, 
A. Burmistrov, 2023
© Kazan National Research Technological 
University, 2023 
2

CONTENT 
LIST OF ABBREVIATIONS AND REFERENCE ................................. 4 
INTRODUCTION 
........................................................................................ 7 
1. STATE OF THE ART AND RESEARCH OBJECTIVES ................. 9 
1.1. Determination of SVP operating principle 
...................................... 9 
1.2. Description of SVP Standard Design ............................................ 11 
1.3. Description of SVP Operating Process.......................................... 14 
1.4. SVP Classification ......................................................................... 17 
1.5. Advantages of SVP 
........................................................................ 23 
1.6. Disadvantages of SVP ................................................................... 24 
1.7. Summary ........................................................................................ 25 
2. EXPERIMENTAL STUDY OF SVP 
................................................... 27 
2.1. Review of Methods for Obtaining Indicator Diagrams 
................. 27 
2.2. Development of Subject Experimental Study ............................... 31 
2.3. Description of the Experimental Test Unit 
.................................... 35 
2.4. Study Procedure 
............................................................................. 40 
2.4.1. Pressure Measurement in the Pump Working Cavities 
........ 
40 
2.4.2. Measurement of Pumping Speed and Power 
Consumption 
................................................................................... 
48 
2.4.3. Estimation of Pressure Measurement Error  in the Pump 
Working Cavities ............................................................................ 
53 
2.4.4. Evaluation of Measurement Error in Pumping Speed ......... 
58 
3. MATHEMATICAL SIMULATION OF SVP OPERATING
PROCESS ................................................................................................... 63 
3.1. Review of Performance Methods for Scroll Machines .................. 
63 
3.2. Fundamentals of Mathematical Model 
........................................... 
67 
3.3. Calculation of Gas Backflow  in Channels with Moving 
Walls ...................................................................................................... 
73 
3.4. Calculation of Radial Clearance Size ............................................. 
80 
3.5. Comparison of Experimental Indicator Diagrams 
and Mathematic Simulation Data .......................................................... 
85 
3.6. SVP Power Performance Analysis ................................................. 
88 
3.7. Analyzing the Influence of Scroll Geometrics on SVP Power 
and Volume Values 
................................................................................ 
92 
CONCLUSION......................................................................................... 101 
LITERATURE ......................................................................................... 102 
3 

 
LIST OF ABBREVIATIONS AND REFERENCE 
List of abbreviations 
 
SVP – scroll vacuum pump 
CFD – computational fluid dynamics (вычислительная гидродинамика) 
KNRTU – Kazan National Research Technological University 
VP – vacuum pump 
CNC – computer numerical control 
KF – Klein Flange (фланец Клейна) 
GBD – gas ballast device 
MM – mathematical model 
CVP – claw vacuum pump 
VDТО - standard deformation-thermocouple vacuum gauge 
AC – accuracy class 
ERR – error 
RMSD – root mean square deviation 
 
List of Reference 
 
c – pressure change rate along the channel 
k – adiabatic exponent 
R – gas constant 
T – absolute temperature 
M – gas molecular mass 
∆τ – lag period 
lch – length of cylindrical channel 
Sin – pumping speed 
Q – gas flow entering the measuring chamber 
Pin – measuring chamber pressure 
Pult – ultimate pressure (base pressure) in chamber 
W – power consumption 
Pi – pressure differential measured by a sensor between atmospheric and 
working chamber pressure 
vMIC – sensor report rate 
n – rotation speed of drive shaft 
vphoto – phototachometer reading 
Np –number of points in period 
4 

Тave – averaged period of rotor rotation 
𝐴
̃ – arithmetical average of observation data
k – number of points for each experimental set 
S – root-mean-square deviation 
h – abnormality criterion 
ε – confidence random error of measuring data 
tq – quantile of Student`s t-distribution 
θ – systematic error 
∆Sin – measuring data confidence limit 
δ – maximum relative measurement error 
Vin – inlet volume 
Vcut – cut-off volume 
Vout – outlet volume 
SD – positive displacement volume 
h – scroll height 
Fcut – cut-off region area 
L – arc length 
е – eccentricity 
rb – base circle radius 
ф – angle of scroll end 
b – scroll thickness 
V – cavity current volume 
 – angular rate 
QH – external heat flow 
φ – rotation angle of drive shaft 
M – gas in or gas out per second 
h – gas enthalpy 
w – tangential velocity 
b(x) – channel half thickness in section x 
P(x) – pressure in section x 
λ0 – average free-path length 
Kn – Knudsen number 
μ – dynamic viscosity 
Rg – gas constant 
Тw – wall temperature 
Тg – gas temperature 
α – heat-exchange coefficient 
Fw – wall surface area 
5 

λ – gas thermal conductivity 
R – radius of scroll wall curvature at certain point 
dh – typical size – hydraulic diameter of the channel 
R – Reynolds number 
Pr – Prandtl number 
фwp – working process duration 
P – working cavity pressure 
V – working cavity volume 
L1 and L2 – indicator work for each cut-off cavity 
6 

 
INTRODUCTION 
On account of sanctions policy of some foreign countries against Russia, 
our country has taken the line of imports phase-out which means high-tech 
manufacturing design allowing to produce world-class equipment.  
Development of modern vacuum technology processes, accordingly, 
puts forward new demands towards pumping facilities, among those 
the provision of oil-free low and medium vacuum in the pumped volume. 
Thereby, of note, vacuum produced in the pumped volume is regarded as oilfree, in case that mass-spectrum of residue gases lacks molecules with mass 
number over 44 [1]. 
Among oil-free vacuum pumps with pumping speed of 60 m3/h and 
ultimate pressure of about 1 Pa, the most in-demand are scroll vacuum pumps 
(SVP) [2, 3] due to a number of objective advantages such as quietness, low 
vibration, low specific energy consumption and capability of pumping 
vapors and gas-vapor media. SVP are used both as individual pumping 
facilities and forevacuum pumps for Roots, turbomolecular and other oil-free 
machines [4, 5]. 
SVP have been manufactured abroad for more than 25 years and still are 
studied and improved, whereas in Russia, SVP started to be produced serially 
only in 2016 [6, 7]. Scroll machines are phased-in amid intense global rivalry 
of vacuum technology manufacturers [8–10]. Therefore, this paper is 
intended for comprehensive study of operating process of SVP, thus, laying 
the groundwork for further development of domestically made scroll 
machines to ensure their competitive performance. 
The first scroll compressor machines in our country were designed by 
a group of scholars under the guidance of I. A. Sakun. Study of scroll 
compressors was then continued in the works by E. R. Ibragimov [11] and 
Yu. A. Paranin [12] with the lead of I. G. Khisameev. The works above 
provided scroll compressor indicating and thermal profiling, and 
the observed dependenies were applied for drawing up calculation 
procedure. Study of scroll machines operation under vacuum began about 
10 years ago, at the department of KNRTU “Vacuum and compressor 
equipment of physical machines”, the results obtained being presented in 
the paper by R. R. Yuakupov [13] providing pumping speed measurement 
data at various rotation speeds of drive shaft, and SVP mathematical model 
developed on account of temperature-induced variations of scroll elements. 
7 

The most uniform calculation procedures of SVP are given in the works 
by Zeyu Li [14], Xiang-Ji Yue [16] and Tadashi Sawada [17] describing 
the mathematical model of scroll vacuum pump operating process, based on 
solutions of differential equationswith regard to experimental study of both 
external and internal specifications of a scroll machine. 
Of special interest are works by Xiang-Ji Yue, A Spille-Kohoff [18], 
Qingqing Zhang [19]. Therein, gas flow simulation in a scroll pump is carried 
out by CFD method (Computational Fluid Dynamics). 
The authors are grateful to their colleagues for instructive discussion, 
provision of separate materials and help of various kinds when editing 
the manuscript. Particular thanks are due to PhD in Physics and Mathematics, 
Associate Professor M. D. Bronshtein (KNRTU, Kazan). 
Readers` criticism and suggestions are welcome and will be accepted 
with gratitude. 
8 

 
1. STATE OF THE ART AND RESEARCH OBJECTIVES 
1.1. Determination of SVP operating principle 
SVP (Fig. 1.1) is a distinctive pump which as it follows from 
GOST 5197-85 “Vacuum engineering. Terms and definitions” [24] 
combines various structural solutions and operating principles of four 
vacuum pumps (VP) at once. Thus, SVP blend at a time:  
– mechanical vacuum pump,  
– positive displacement volume vacuum pump, 
– gas ballast vacuum pump, 
– dry-sealed vacuum pump. 
For the sake of completeness, we cite GOST definitions of above pumps. 
Mechanical vacuum pump is a gascompressor vacuum pump; its 
pumping action is based on gas transfer due to mechanical movement of 
the pump operating parts [24]. 
Positive displacement volume vacuum pump is a mechanical vacuum 
pump, whereby the volume filled with gas is cut off from the input at regular 
intervals and pumped to the output [24]. 
Gas ballast vacuum pump is an oil-sealed vacuum pump with a metering 
device for noncondensable gas supply aimed to prevent condensation of 
pumped vapors in the pump [24]. 
Dry-sealed vacuum pump is a positive displacement volume pump 
without oil (fluid) seal [24]. 
It can be said now that SVP is a mechanical vacuum pump for gas 
transporting, its pumping action is based on regular volume variation of 
crescent-shaped cavities (Fig. 1.2) formed by nonmovable (Fig. 1.1, pos. 1) 
and movable (Fig. 1.1, pos. 2) scroll elements. Variation of crescent-shaped 
cavities is due to orbital movement of the movable scroll part about 
the nonmovable one. Thus, gas is pumped from input to output of the pump. 
9 

Figure 1.1. General view of SVP: 1 – scroll element movable; 
2 – scroll element nonmovable; 3 – casing; 4 – eccentrical drive shaft,
5 – anti-turn shaft; 6 – balancer; 7 – fan blading; 8 – compensator;  
9 – half-coupling; 10 – motor; 11 – electrical fan; 
12 – input nozzle; 13 – output nozzle; 14 – support;  
15 – hanger; 16 – face seal;17 – fan cover; 
18 – ballast gas-supply duct; 19 – reverse valve; 
20 – gas  ballast metering device; 21 – angular-contact bearing; 
22 – angular-contact bearing; 23 – bearing;  
24 – needle bearing; 25 – seal; 26 – sealing ring; 27 – seal 
10