Inte rnatio nal Jo urnal o f Sc ie ntific & Eng inee ring Re se arc h Vo lume 3, Issue 3 , Marc h -2012 1

ISSN 2229-5518

Decoding the NGTE/Calvert Axial Flow

Compressor Computer Program

Tonye K. Jack and Robin L. Elder

(

Abs tract— Several models are used f or the design and perf ormance evaluation of axial compressors – thickness, clearance, eff iciency and others. How ever, tw o principal models f or the overall perf ormance evaluation are used – in North America, the US National Aeronautics and Space Administration (NASA) or Steinke Model, and in Europe, the UK National Gas Turbine Establishment Model (NGTE) or How ell/Calvert Model. In all, there are essential relationships and connects in some of these models. A n earlier investigator had applied the NASA model to a major UK gas turbine manuf acturer’s equipment w ith usef ul results. The aim of this research eff ort w as to evaluate some of the major models, decode the NGTE Calvert computer program since some of these relationships are experimentally developed and not available in the open literature, f ind the connecting relationships, through new models development .

Inde x Terms— Axial Compressor, Axial Perf ormance, Compressor, Compressor Perf ormance, Compressor Tip Clearance,, Multistage

Co mpressor, Off-Design Perf ormance, Stage Stacking, Diff usion f actors, loss coeff icient, blade aspect ratio .

—————————— ——————————

n the original unpublished paper, the title was given as “ A

Yet to be Concluded Summary Evaluation of the Calvert

At Stall:

Program”. The current title depicts more accurately, the

*T*

1

*x h*

initial steps taken to fulfill the purpose of the research effort.

Given below is a brief summary of applicable relations from

mea n

0.99*T *

*h *

the Calvert program [1]. Additional relationships derived

ref

R

(4)

*A *

from velocity triangles and the open literature, and steps in

the derivation are not shown.

R1

0.975 *A *

Based on the input data given, and by using the area data giv- en at the sections, the mass flow correction factors, and the temperature rise mass weighted mean value correction factor, the following relations are useful in arriving at the Multiply-

At Maximum Efficiency:

2

*T*

*A*

*A *

ing factors.

mea n

*x* RM

*x* R 2

*Q * *MF *

Qmea n

(1)

0.99*T*ref

0.975 *A*R1

0.975 *A*R1

(5)

*T * *MF *

0.975*T*ref

*T*mea n

(2)

At Stall:

1 ARM

A

*x* R 2

A

*x* SM

A

*x* S 2

A

*x* S1

A

*x* SM

A

*x* S 2

A

*x* S1

0.99*T*ref

8

AR1

AR1

AR1

AR1

0.975

ARM

ARM

ARM

AR 2

At Maximum Efficiency:

At Maximum Efficiency:

(6)

AR 2

0.975 *A*RM

x hR

hS

(3)

AS 2

0.975 *A*RM

(7)

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Inte rnatio nal Jo urnal o f Sc ie ntific & Eng inee ring Re se arc h 2

ISSN 2229-5518

At Stall:

The Carter rule as applied is given by:

*T*mea n

0.99*T*ref

m

s

(12)

*T * *MF Q * *MF *

Where, *m*, is a function of the stagger angle (between 0 and 70

degrees).

(8)

*m * 0.2162 0.0008595 0.00002786 2

(13)

*V *

*D * 1.03 0.4 *t*

w

0.7t deH

c

s .V

c

(9)

L 0.02224 0.02436D 0.05D2

(14)

By rearranging “(9)”, the tangential velocity ratio in the Ca l- vert equation (*factor f*) is easily derived:

“(14)” applies for, D>0.244

For D<0.244, loss parameter is held constant, and, *L *= 0.0193.

Stator:

__ __2.*L *

*V D * *deH * 0.7*t*

1.03

s s

cos

(15)

*V * 0.4

t

.s

(10)

*c *

Rotor:

In Jack and Elder [2], a factor of 2 was missing in the clearance

r

s

2.*L *

2

equation. This was an error in the derivation based on the a v-

erage rather than, the addition of the hub and tip displac e-

ment thicknesses as specified in the Koch and Smith [3] paper. The corrected and modified tip clearance relation as a function

cos

*c *

cos 1

(16)

of the loss coefficients in the rotor and stator is given by:

Where, *L*, is the loss parameter.

*t * *h *1 1 r__ V__1

1 2

p

2 2 1

*

h

(11)

It has not been possible to arrive at the exact values in some of

3

2*U V*w2

*V*w1

the figures in the output as displayed in the Calvert program„s

[1] Sample Printer Results Sheets 1 and 2. Furthermore, in

Sample Sheet 2, the correction for mass flow rate has probably

It is proposed to use the deviation angle proposed by Carter [4] as given in the Oldham [5] paper referenced in the pro- gram. An alternative deviation angle equation with improved accuracy has been proposed by Boyce [6] but complex to ap- ply, and will take additional computing memory. It might be interesting to combine the Boyce [6] relation (since this ac- counts for the Mach number effects, and the thickness to chord ratio) with the factor, *m*, in the Oldham [5] relationship. The accuracy of this is yet to be verified.

been done with a specific heat ratio of “γ=1.0”. If this is an error in the program, the actual corrected mass flow is 15 per- cent above its true value. How this affects the overall results is yet to be determined.

This unpublished research effort was conducted at Cranfield University in the autumn months of 1998. The authors wish to thank Cranfield School of Mechanical Engineering for provid- ing the facilities, particularly their specilised research library materials, and computer laboratories.

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Inte rnatio nal Jo urnal o f Sc ie ntific & Eng inee ring Re se arc h 3

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P Pressure

T Temperature

V Velocity

A Area

Q Flow rate

h Aspect ratio

t Blade thickness

tp Tip clearance s spacing

D Diffusion c Chord

L Loss parameter

f factor

deH de Haller number

Greek Letters

Loss coefficient

α air angle

β Blade angle

δ deviation

δ* Displacement thickness

Subscripts

s stator

r rotor

1 inlet

2 outlet

SM mean stator

RM mean rotor

[1] W.J. Calvert, “User‟s Guide to the Howell Multistage Compressor Perfor-

mance PredictionProgram”, NGTE Memo 77023, 1977

[2] T.K. Jack and R.L. Elder, “A Modified Stage Stacking Method for Axial Flow Compressors Calculation, *International journal of Science and Engineering Re- search *, 2012, (Pending Publication)

[3] C.C. Koch, and L.H. Smith, “Loss Sources and their ma gnitudes in

Axial Flow Compressors,” *ASME J. of Engr. For Power, *vol. 2, no. 4, pp. 193-218, July 1976.

[4] A.D.S. Carter and H.P. Hughes, “A Theoretical Investigation into the

Effect of Profile Shape on the Performance of Aerofoils in Cascade, R

& M 2384, 1946

[5] R.K. Oldham, “Some Stage Design Data for Double Circular Arc Compressor

Blading” NGTE Notes NT 589, 1965

[6] M.P. Boyce, “Design of CompressorBlades Suitable for Transonic Axial Flow

Compressors”, ASME 67-GT-47, 1967

[7] M.V. Casey, “A Mean Line Prediction Method for Estimating, the Perfor-

mance of Axial Compressors”, *Proceedings of the Imech*., C264/87, 1987

[8] A.R. Howell, and R.P. Bonham “Overall and Stage Characteristics of Axial

Flow Compressors”, Proceedings of Imech., 1950

[9] A.R. Howell and W.J. Calvert, “A New Stage Stacking Technique for Axial

Flow Compressors”, *ASME J. of Engr. For Power, *1978

[10] D.C. Miller and D.L. Wasdell, “Off-Design Prediction of Compressor Blade

Losses” *Proceedings of the Imech*., C279/87, 1987

**Tonye K. Jack**, registered Engineer and ASME member, has a Masters Degree in Rotating Machine Design from Cranfield University, and is currently a University Teacher in Port Hrrcou rt, Rivers State, Nigeria, teaching undergraduate classes in Mechanical Engineering. E -mail: to- nyekjack@yahoo.com

**Robin L. Elder **, Ph.D, Professor of Turbomachinery Design and Engi- neering, and former Head of Turbomachinery & Engineering Mechanics Department, School of Mechanical Engineering, Cranfield University, England. He is currently a Director of PCA Engineers Ltd, a Turboma- chinery Engineering Consultancy.

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