PV2003_5933.pdf

1st International Energy Conversion Engineering Conference

17-21 August 2003, Portsmouth, Virginia

AIAA 2003-5933

A “ ggg ”-TYPE STIRLING ENGINE:

SOME RESULTS OF SECOND-ORDER NUMERICAL SIMULATIONS AND

EXPERIMENTAL TESTS

K. Mahkamov * , D. Djumanov **

B. Orunov † , A. Korobkov †

School of Engineering, Durham University

Durham, DH1 3LE, UK,

Tel: +44 191 334 2429, Fax:+44 191 334 2390

Email: khamid.mahkamov@durham.ac.uk

ABSTRACT ***†

The paper describes investigations performed

on a test rig at the University of Durham (UK)

with a small “g”-type Stirling engine. The engine

is equipped with instant pressure and

temperature sensors and a set of thermocouples

connected to a data acquisition system for the

registration of parameters of the working cycle

and the experimental performance of the engine.

An “in-house” second-order type computer code

was used to numerically simulate the working

processes of the engine and a comparison of

theoretical and numerical data demonstrates that

the developed code is capable of predicting the

performance of the engine within an accuracy

which is acceptable for engineering purposes.

These equations are written for each chamber in

the calculation scheme of the engine. The next

group of modelling techniques includes two- and

three-dimensional CFD models of the working

process of the Stirling engine. The use of CFD

techniques allows much insight into the heat and

flow processes which occur in the internal gas

circuit of the engine. Furthermore, CFD models

are also used to analyse the fuel burning process

in the combustion chambers for Micro CHP

installations and the flow patterns of flue gases

over the external surface of an engine’s heater.

Recently, a test rig with a small Stirling

engine has been commissioned in the Thermo-

Fluids Laboratory in collaboration with the

Physical-Technical Institute of the Uzbek

Academy of Sciences (Tashkent, Uzbekistan).

Preliminary experimental investigations have

commenced in order to accumulate data to use

for the calibration of the above mathematical

models. After completion of the preliminary

experimental trials, it is planned to refine the

designs of the engine and of the combustion

chamber. Finally, after installation of additional

equipment the test rig will be converted to a

Micro CHP installation.

INTRODUCTION

One of the research directions of the New and

Renewable Energy Centre at Durham University

(UK) is to develop efficient power units for

embedded power generation via theoretical and

experimental investigations. The Thermo-Fluids

Group in the School of Engineering is part of

this Centre and works intensively on the

development of Micro CHP installations on the

basis of small Stirling engines.

The theoretical aspect of the investigation is

concerned with the development of computer

codes which can be used for modelling the mass

and heat transfer processes present in

components of a micro CHP unit. Thus the

working process of the Stirling engine is

described using several types of mathematical

models. The simplest model is a second-order

type mathematical model based on the solution

of a system of ordinary differential equations

corresponding to energy and mass conservation.

DESCRIPTION OF THE ENGINE’S

DESIGN

Figure 1 represents the main cross-sections of

the small Stirling engine on the test rig. The

Stirling engine is of a g-type and for the

production of 400 Watts of electrical power. The

machine consists of two –“hot” (1) and “cold”

(2)- cylinders installed on a pressurised

crankcase (3) which houses a crankshaft drive

mechanism (4) with a fly-wheel (5). The

crankshaft is installed in the crankcase using

rolling bearings (6). The displacer (7), made

from a titanium alloy, and the power piston (8),

made from an aluminium alloy, are connected to

the crankshaft by rods (9) and (10). Both the

pistons have guiding (11) and sealing (12) rings

* Lecturer in Thermo-Fluids

** Visiting Research Assistant

†

Research Scientist

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