The non-heat-pipe receiver/P-40 Stirling engine system design is described. A 25 kW direct-driven induction-type alternator will be mounted directly to the P-40 engine to produce to a 60 Hz, 115/230 volt output

Haglund, R. A.

English

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NON-HEAT PIPE/P-40 STIRLING ENGINE
R. A. Haglund, Senior Project Engineer
Fairchild Stratos Division
Manhattan Beach, California
ABSTRACT
This project will demonstrate the technology for a full-up Hyb .`id
Point-Focus Distributed Dish Stirling Solar Thermal Power system
by the fall of 1980 at JPL's Desert Solar Test Facility near Lan-
caster, California. Hybrid operation is provided by fossil fuel
combustion augmentation, which enables the Stirling engine to
operate continuously at constant speed and power, regardless of
insolation level, thus providing the capability to operate on
cloudy days and at night.
The Non-Heat-Pipe Receiver/P-40 Stirling Engine system will be
installed and operated on the JPL Test Bed Concentrator. A 25-
kW direct-driven induction-type alternator will be mounted di-
rectly to the P-40 engine to produce to a 60-11z, 115/230-volt
output.
NON-HEAT PIPE RECEIVER DESIGN
The Non-Heat-Pipe Receiver design is a cavity-type receiver, as
illustrated in Figure 1. The primary receiver surface is a con-
ical plate with integral passages for the helium working fluid.
The passages are formed by Inconel 617 tubes imbedded in a
copper matrix, which in turn in incapsulated in an Inconel 617
sheet. The cone is heated by solar insolation on the exposed
surface and by combustion gas on the back surface and the re-
generator tubes. The receiver is attached directly to the Stir-
ling engine cylinders and regenerator housings. Simplicity in
design has been emphasized, along with extensive use of parts
and assemblies proven in other applications but under similar
operating conditions, such as normally found in industrial
boilers and gas turbines. Where expensive cobalt alloys are
required, their use has been minimized.
The combustion system design is based on heavy duty industrial
burner technology, sealed to the size and configuration required
to assure reliable cold start, stable combustion over the full
operating range and uniform heating of the heater tubes extending
from the underside of the cone to the engine regenerator mani-
folds. The combustion air, provided by an electric-motor-driven
constant speed blower, is directed through a preheater into the
combustion chamber, which contains eight integrally cast ven-
turies, oriented to produce a swirling flow field inside the
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FIGURE 1. NON-HEAT PIPE/P-40 STIRLING ENGINE
combustion chamber. Fuel is introduced through a ]et located
inside each venture. Electric spark igniters are provided di-
rectly in front of two of the venturies; the igniters also pro-
vide flame sensing, so that the main fuel valve closes auto-
matically in the event of flame-out. Automatic restart is pro-
vided.
Performance Goals
The following performance goals have been identified by JPL for
the Non-Heat-Pipe Receiver design:
Concentrator diameter (active)	 10 m
Geometric concenbrationratio	 2000
Peak insolation (1 kW.m
2
 )	 76.5 kW
Concentrator efficiency (clean)	 0.83
Total error (slope plus pointing)	 3 mr
Fossil fuel combustor peak input to helium 70.0 kWc
Combustor turndown ratio	 10:1
Working fluid temperature (helium)	 1200' to 1500°F
Peak engine pressure (heliurn)	 2500 to 3000 psi
96
.,.. ..	 eiver Performance (24 -cm Aperture Diameter)
Losses (kW)
Ra ation	 2.8	 5.2
Reflectance	 0.9	 0.7
Convection	 3.6	 4.4
Efficiency (t)	 0.875	 0.827
Maximum Cavity Temperature ('F)
Center Plug	 1966	 2053
Cone	 1561	 1836
Program Status
The receiver design effort has been completed and a Detailed De-
sign Review was held on September 27, 1979. As shown by the
scherdule in Figure 2, combustion and heat transfer tests are
being conducted at Fairchild Stratos Division in Manhattan
Beach, California and are carried out jointly by JPL, Fairchild
and the Institute of Gas Technology. Test objectives include
evaluation and demonstration of cold start, combustion stability
and energy release at various power levels, combustion air pre-
heat, pressure drop, fuel/air ratios and heat transfer. Reliable
cold start performance, full design output power and turndown
capability have been demonstrated. The general arrangement of
the combustion test rig is illustrated in Figure 3.
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3 4 t r, 7 A n 110111 12 1 2 3 4 5 6 7 8 h 1011 1'
Contract Co Ahead A
Preliminary Design (PDR)
Detailed Design (DDR)
Combustion Tests
Receiver/P-40 Comaatibility
Final Technical Review Tests
Receiver/P-40 Acceptance Tests I 0
Fall-up System Demonstration
FLGURE 2. MAJOR TECHNICAL MILESTONES CONTRACT 955400
30 November 1979
97
FIGURE 3. PHOTO Or TEST RIG
98


Non-heat pipe/P-40 Stirling engine

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