14-01-2011, 08:05 PM
An Optimized Low Heat Rejection Engine for Automotive Use - An Inceptive Study
LAL PRASAD P
Roll NO: 27
S7 Mechanical Engineering
Govt. Rajiv Gandhi Institute of Technology
LAL PRASAD P
Roll NO: 27
S7 Mechanical Engineering
Govt. Rajiv Gandhi Institute of Technology
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CONTENTS
INTRODUCTION
BACKGROUND
DESIGN CRITERIA
CERAMIC MATERIALS
HIGH TEMPERATURE TRIBOLOGY
POWER PLANT STRUCTRE
POWER PLANT CONTROL
CONCLUSIONS
INTRODUCTION
Design Of LHR
Deficiencies
Progress in LHR Design
Design Criteria
Advances in Material Science
Design
BACKGROUND
Combustion
Materials
History
U.S. Army Tank-Automotive
Command (TACOM)
Cummins Engine Company Isuzu Motors
Ford Motor Company, General Motors Corporation
NKG Insulators/Mitsubishi Motors Corporation
Integral Technologies, Massachusetts Institute of Technology
OBSERVATIONS
High speed camera by Tiajin university
Reduced ignition delay
Impairing air-fuel mixing,
Prolonging combustion duration.
Reduced fuel injector nozzle orifice diameter / the employment of special impingement plates to enhance air-fuel mixing
DESIGN CRITERIA CRITERIASATISFYING TO THE VEHICLE OPERATOR
Quiet operation.
Smooth operation, lacking in vibration.
Quick response to control input.
Ample torque and power.
High reliability and durability.
Ease of operation and maintenance.
DESIGN CRITERIA ECONOMIC CRITERIA
Simple in design.
Manufactured from the minimum amount of materials by economical methods.
Modular and/or compact in construction for ease of repair and ease of placement in compact engine compartments.
Long service life.
DESIGN CRITERIA PASSENGER VEHICLE COMPATIBILITY CRITERIA
High torque at low speeds and less at high speeds.
Efficient part load operation.
Operable at temperatures between -30 to 50 °C, and unaffected by altitude.
DESIGN CRITERIA EFFICIENCY CRITERIA
Multi-fuel capable.
Highly fuel efficient.
Low in emissions of incomplete combustion products.
DESIGN CRITERIA
Low tolerance of ceramic materials to mechanical stress and thermal shock.
Failure of liquid lubricants at high temperatures.
Degraded combustion process due to high temperatures.
Reduced volumetric efficiency due to increased component temperatures encountered during induction.
CERAMIC MATERIALS Advantages
High hardness
High elastic moduli
Resistance to corrosion and wear
Strength at high temperatures
Low thermal conductivity
CERAMIC MATERIALS
Nitrides of silicon (Si3N4)
Carbides of silicon (SiC)
Oxides of chromium (Cr2O3)
Oxides of Iron (Fe2O3)
Oxides of Aluminum (Al203)
Partially stabilized oxide of zirconium (Zr02, or PSZ)
CERAMIC MATERIALS Disadvantages
Low ductility
Low tensile strength
Low bending strength
Conventional piston and cylinder stresses
HIGH TEMPERATURE TRIBOLOGY
Expander temperatures of 1200 to 1500 0C
Solid lubricants
Solids formed via gaseous dissociation
Gaseous lubricants.
POWERPLANT STRUCTURE
COMPRESSOR
INSULATED ACCUMULATOR
BURNER & FUEL INJECTION SYSTEM
THE EXPANDER
General Engine Schematic Showing Primary Component
COMPRESSOR
conventional, positive displacement piston device
driven by the expander via a suitable fixed-ratio, power transmission, but is a separate device
poppet type valves
reduce noise
improve air flow
contribute to complexity and cost
COMPRESSOR
Conventional air or liquid cooling
Reduce part load compressor work, increasing them overall, part load efficiency.
Throttling to vary induction air flow.
Varying intake valve timing
Idling individual cylinders.
INSULATED ACCUMULATOR
Store the compressed air supply.
Largest component in the power plant.
Sufficient volume to provide an energy reserve to the burner/expander during acceleration.
Not practical to construct an accumulator with sufficient volume to allow for prolonged operation without a functioning compressor or to allow for regenerative braking.
INSULATED ACCUMULATOR
Minimum heat energy loss
Torque versus engine speed
Full torque - available at zero RPM
Less torque at higher engine speeds.
Slower operating speeds
Reduced idling requirements
Locations
elongated form underneath the vehicle similar to a driveshaft.
engine compartment, somewhere in the rear of the vehicle.
BURNER & FUEL INJECTION SYSTEM
Similar in design to a small gas turbine combustor
Reliable
Repeated re-lighting.
Ceramic materials
Exit temperatures of 1200 to 1500 0C.
Complete combustion,
NO2 formation
THE EXPANDER
Insulated cylinder housing
A double acting piston.
An appropriate tribolical system
No oil sump
packing material will be a solid lubricant
Reduced lateral piston/cylinder forces
THE EXPANDER
Volumetric compression ratio of 6 to 8
1200 to1500 0C
assuming compressor and expander efficiencies of 85%
neglecting heat rejection
Exhaust gas regeneration
Integral accumulator/regenerator design.
Crosshead Shaft Packing
POWERPLANT CONTROL
INDUCTION
Throttle Control
ENGINE POWER
Throttle Control
Variable Intake Control
COMBUSTION
Modulation of fuel flow to the burner
POWERPLANT CONTROL
CONCLUSIONS
Smooth and quiet power delivery
Nonimpulsive combustion
Relatively slower engine speeds
A favorable torque response.
Enhanced part load efficiency
Variable compressor induction.
Reduced fuel consumption
Lean air/fuel ratios.
CONCLUSIONS
Improved combustion efficiency
A semi-continuous combustion prior to the expander.
Increased volumetric efficiency
Reduced induction component temperatures.
Increased thermodynamic efficiency
More complete expansion of combustion products.
Increased combustion temperatures.
