05-05-2014, 10:53 AM
ADVANCED INTERNAL COMBUSTION ENGINE RESEARCH
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Abstract
In this manuscript, research on hydrogen internal combustion engines is discussed. The
objective of this project is to provide a means of renewable hydrogen based fuel utilization. The
development of a high efficiency, low emissions electrical generator will lead to establishing a
path for renewable hydrogen based fuel utilization. A full-scale prototype will be produced in
collaboration with commercial manufacturers.
The electrical generator is based on developed internal combustion engine technology. It is able
to operate on many hydrogen-containing fuels. The efficiency and emissions are comparable to
fuel cells (50% fuel to electricity, ~ 0 NOx). This electrical generator is applicable to both
stationary power and hybrid vehicles. It also allows specific markets to utilize hydrogen
economically and painlessly.
Introduction
Two motivators for the use of hydrogen as an energy carrier today are: 1) to provide a transition
strategy from hydrocarbon fuels to a carbonless society and 2) to enable renewable energy
sources. The first motivation requires a little discussion while the second one is self-evident.
The most common and cost effective way to produce hydrogen today is the reformation of
hydrocarbon fuels, specifically natural gas. Robert Williams discusses the cost and viability of
natural gas reformation with CO2 sequestration as a cost-effective way to reduce our annual CO2
emission levels.
Background
Electrical generators capable of high conversion efficiencies and extremely low exhaust
emissions will no doubt power advanced hybrid vehicles and stationary power systems. Fuel
cells are generally considered to be ideal devices for these applications where hydrogen or
methane are used as fuel. However, the extensive development of the IC engine, and the
existence of repair and maintenance industries associated with piston engines provide strong
incentives to remain with this technology until fuel cells are proven reliable and cost
competitive. In addition, while the fuel cell enjoys high public relations appeal, it seems possible
that it may not offer significant efficiency advantages relative to an optimized combustion
system. In light of these factors, the capabilities of internal combustion engines have been
reviewed.
Combustion Approach
Homogeneous charge compression ignition combustion could be used to solve the problems of
burn duration and allow ideal Otto cycle operation to be more closely approached. In this
combustion process a homogeneous charge of fuel and air is compression heated to the point of
autoignition. Numerous ignition points throughout the mixture can ensure very rapid
combustion (Onishi et al 1979). Very low equivalence ratios (φ ~ 0.3) can be used since no
flame propagation is required. Further, the useful compression ratio can be increased as higher
temperatures are required to autoignite weak mixtures (Karim and Watson 1971).
2-Stroke Cycle
Inherent in the configuration selected is the need to scavenge the exhaust gases out of the
cylinder and replace them with fresh fuel/air charge while the piston is down at the bottom of the
cylinder. This requirement is due to the need to have trapped gases in the cylinder to act as a
spring, as well as to provide the next combustion event.
Conventional 2-stroke cycle engines have developed a reputation for low fuel efficiency and
high hydrocarbon emissions due to short-circuiting of the inlet fuel/air mixture directly to the
exhaust port. The typical 2-stroke application stresses power density over efficiency and
emissions – chain saws, weed whackers, marine outboard motors. These devices must operate
over a wide speed and power range.