Search Results

This paper details the development of a compressed natural gas (CNG) engine with ultra lean burn low emissions potential. Hydrogen assisted jet ignition (HAJI) is used to achieve reliable combustion and low NOx emissions, whilst direct injection is used to improve thermal efficiency and decrease hydrocarbon (HC) emissions. It is found that port inducted propane, port inducted CNG and directly injected CNG all produce negligible levels of CO and NOx when operating at air/fuel ratios higher than λ = 1.8. Furthermore, direct injection of CNG produced approximately 100 ppm C6 less HC emissions than port induction of CNG, and port induction of CNG decreased the HC emissions by around a factor of a third to a half in comparison with port induction of propane.

Gas assisted jet ignition is an advanced prechamber ignition process that allows ignition of ultra lean mixtures in an otherwise standard spark ignition engine. The results presented in this paper indicate that in a gas assisted jet ignition system fuelled with LPG in both the main chamber and prechamber, the lean limit can be extended to between λ = 2-2.35, depending on the load and speed. Although the fuel combinations that employ H2 as the prechamber fuel can extend the lean limit furthest (λ = 2.5-2.6), the extension enabled by the LPG-LPG prechamber-main chamber combination provides lower NOx emission levels at similar λ. In addition, when LPG is employed in place of gasoline as the main chamber fuel, hydrocarbon emissions are significantly reduced, however with a slight penalty in indicated mean effective pressure due to the gaseous state of the LPG.

The HAJI (Hydrogen Assisted Jet Ignition) system for S.I. engines utilises direct injection of small amounts of hydrogen to enhance the combustion of a variety of automotive fuels. Although not the primary purpose of HAJI, the hardware, once in place, also lends itself to the possibility of hydrogen-only running during a cold start. Cold-start simulations have been performed using a single cylinder engine. Results are presented, comparing hydrogen-only tests with standard HAJI operation and normal spark-ignition operation. HAJI and spark ignition tests were carried out with gasoline as the main-chamber fuel. Emission levels and combustion stability characteristics were recorded as the engine warmed up. The differences between the various fueling/ignition scenarios are presented and the implications for possible automotive applications are discussed in light of current and proposed emissions legislation.

Favorable and unfavorable properties of hydrogen as a combustion engine fuel have been accommodated in a design of a fuel efficient and clean engine providing similar to gasoline maximum torque and power. The advanced H2ICE being developed is a turbocharged engine fitted with cryogenic port hydrogen fuel injection and the hydrogen assisted jet ignition (HAJI). The combustion chamber is designed to produce a high compression ratio and therefore high thermal efficiency. A waste gated turbocharger provides pressure boosting for an increased power density running ultra lean for SULEV operation without after treatment. Thanks to the combustion properties of hydrogen further enhanced by the HAJI system, the engine load is mainly controlled throttle-less decreasing the fuel-to-air equivalence ratio from ultra lean ϕ=0.43 to ultra-ultra lean ϕ=0.18. The computational model developed for addressing the major design issues and the predicted engine performance and efficiency maps are included.

HAJI (Hydrogen Assisted Jet Ignition) is an advanced combustion initiation system for otherwise standard S.I engines. It utilises the fluid mechanics of a turbulent, chemically active jet, combined with the reliability of spark igniting rich hydrogen mixtures. The result is an extremely robust ignition system, capable of developing power from an engine charged with air-fuel mixtures as lean as λ = 5. Experiments have been performed using a single cylinder engine operating on gasoline in the speed range of 600-1800 r/min. Data are presented in the form of maps which describe fuel efficiency, combustion stability and emissions with respect to load, speed, air-fuel ratio and throttle. The results are incorporated into a model of a known engine and vehicle and this is used to estimate performance over the Federal drive-cycle.

A real time energy management (EMS) optimizing algorithm is introduced that performs similar to offline dynamic programming (DP) for parallel HEVs. The EMS and the DP are compared, especially with the addition of a local hill climbing technique, to the example performance prediction of the fuel consumption of a 1.67 tonne large car using a 50 kW Honda Insight engine (representing 65% power reduction from standard) as reference. Then the performance of the vehicle in HEV mode, with a parallel 30 kW motor/generator is examined. The average improvement of this vehicle over five drive cycles from around the world is about 50% reduction in fuel consumption. Next the engine is replaced with an advanced SI turbocharged engine with assisted ignition which returns the performance to that expected of this class of car i.e. 0-100 km/h acceleration time of 7 s. This results in a 14% average reduction in fuel consumption across the five cycles compared with the base Honda engine.

This paper presents a study of the performance of a 6-cylinder, spark-ignited, port-fuel-injected, production engine modified for hydrogen fueling. The engine modifications include turbo-charging, multiple fuel injectors per port and charge-dilution control techniques. Pumping losses are reduced through ultra-lean burn and throttle-less operation alongside high charge dilution ratio control achieved by twin independent variable cam timing without external EGR. Lean-burn combustion, engine-out emissions and brake thermal efficiency results are examined in detail. In particular, low NO emissions and brake thermal efficiencies near 38% are observed experimentally at the same operating conditions. The former is explained in terms of the usual thermal NOx pathway. Usage of throttle position, injection timings and cam timings for avoiding preignition and knock over the entire engine map are also discussed.

Hydrogen assisted jet ignition (HAJI) is a pre-chamber ignition system for otherwise standard gasoline fueled spark ignition engines that involves the use of a chemically active turbulent jet to initiate combustion in lean fuel mixtures. HAJI burns the lean main charge rapidly and with almost no combustion variability, which allows for low hydrocarbon emissions and almost zero NOx, due to lower peak temperatures. This paper focuses on the effects of different pre-chamber fuels on combustion stability, lean limit and emissions in a single cylinder, HAJI equipped, CFR engine under a worst case, light load condition. Results indicate that the choice of pre-chamber fuel affects the main chamber lean limit but that emissions are not largely affected before this lean limit is reached. The lean limit was extended furthest, to λ = 2.5 with hydrogen, followed by λ = 2.35 with LPG, λ = 2.25 with CNG and λ = 2.15 with carbon monoxide.