Document that explains the chosen concept to the animator

Beta Stirling Engine With

Rhombic Drive Stirling engine uses heat as the energy input. It is proposed to develop a Stirling

engine for a 1.5 kW electrical output. Modelling and computer analysis is

performed for one such engine for 1.5 kWe capacity.

Student: Shendage D. J.

Co-supervisor: S B Kedare Supervisor: S L Bapat

Course Name: Cryogenics Engineering I (In Mech. Engg. Dept.)

Glossary Stirling engine Robert Stirling invented regenerative cycle heat engine. The ideal

Stirling cycle consists of two isothermal and two isochoric processes. The system operates on a closed thermodynamic cycle using low molecular weight, well-behaved gases such as helium or hydrogen.

Regenerator The regenerator may be thought of as a thermodynamic sponge,

alternately releasing and absorbing heat to and from the working fluid.

Piston Piston is a structural member sufficiently robust to withstand all

the gaseous, mechanical, and inertia forces imposed on it. Displacer Displacer is characterised as a component having negligible

pressure difference and high temperature difference across it.

Learning Objectives:

1. Thermodynamics of the Stirling cycle 2. Mechanical arrangement of beta type Stirling engine

Stirling cycle was mainly looked at for power generation rather than for cooling. As

such the analysis was developed first for the engine and then modified for the cryocoolers. Understanding of the cycle becomes much easier if the engine cycle is discussed before moving over to the reversed cycle for cooling.

Stirling engines are again becoming relevant due to shortage and high cost of fossil fuels. Stirling engines run quietly on combustion of any fuel. Stirling engines have high efficiency and are safe over a wide operating conditions range. Stirling engines are generally compact. Further, these engines are suitable for concentrated form of solar energy which is inexhaustible. The operation of various engine configurations based on practical considerations will be helpful if we consider the animation for these configurations.

Hollow displacer

(Displacer inside

volume)

Solid displacer

Pre

ssu

re,

bar

Expansion space volume, cm3

Hollow displacer

Solid displacer

Displacer inside

volume

Press

ure,

ba

rCompression space volume, cm

3

Hollow

displacer

Solid displacer

Displacer inside

volume

Press

ure,

ba

r

Total volume, cm3

Q1- The maximum thermal efficiency of Stirling cycle

(a) is the same as the Carnot cycle. (√)

(b) is less than the Carnot cycle.

(c) is more than the Carnot cycle.

Questionnaire for users to test their

understanding

Q2- The four processes in the Stirling cycle are maximum thermal

efficiency of Stirling cycle

(a) Isothermal compression- Constant volume heat addition –

Isothermal expansion - Constant volume heat rejection. (√)

(b) Isobaric compression- isentropic heat rejection – isobaric expansion

- isentropic heat addition.

(c) Isentropic compression - Isobaric heat rejection - isentropic

expansion – Isobaric heat addition.

(d) Adiabatic compression- Constant volume heat addition – Adiabatic

expansion - Constant volume heat rejection.

Questionnaire Q1.

Answers: The maximum thermal efficiency of Stirling cycle (a) is the same as

the Carnot cycle. (√)

Q2.

Answers:

The four processes in the Stirling cycle are maximum thermal efficiency of

Stirling cycle

(a) Isothermal compression- Constant volume heat addition – Isothermal

expansion - Constant volume heat rejection. (√)

1

5

2

4

3

Links for further reading

Reference websites:

http://sycomoreen.free.fr/syco_english/concept_SPRATL_artactuel_eng.html

Books:

1. Walker G., Stirling engine, Oxford University Press, New York, 1980.

2. Martini, W., Stirling engine design manual. NASA report, 1978.

3. Meijer, R. J., “The Philips Stirling Thermal Engine, analysis of the

rhombic drive mechanism and efficiency measurements”, Thesis,

Technical University, Delft, Nov. 1960.

Research paper:

1. Shendage D.J., Kedare S.B. and Bapat S.L., ‘An Analysis of Beta-type Stirling

Engine with Rhombic Drive Mechanism’, Renewable Energy, 2010

doi:10.1016/j.renene.2010.06.041

INSTRUCTIONS SLIDE

• Please provide points to remember to

understand the concept/ key terms of the

animation

• The summary will help the user in the quick

review of the concept.

Summary

Summary • Points to remember

THANK YOU…

These four (.gif) images are from web sites. It is only for reference.

Thank you …

Hollow displacer

(Displacer inside

volume)

Solid displacer

Press

ure, b

ar

Expansion space volume, cm3

Hollow displacer

Solid displacer

Displacer inside

volume

Press

ure,

ba

r

Compression space volume, cm3

Hollow

displacer

Solid displacer

Displacer inside

volume

Press

ure,

ba

r

Total volume, cm3

20

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